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This paper describes Ka-band inductor-shared RF switches and their applications to a 35.2-ps 6-bit true-time-delay (TTD) switched-line (SL) phase shifter (PS). The inductor-shared RF switches share an inductor to match the input and output (I/O) ports of different states, which are realized with a switched inductor for SP ${n}\text{T}$ case and with a shared matching network for DP ${n}\text{T}$ case. The switches are applied to controlling most significant 3 bits of the proposed TTD SL PS. The delay lines and reference lines of the PS are implemented with microstrip lines and inverted microstrip lines in the same space, respectively. The dual-side microstrip lines allow it to have not only a small size but also compensation of the loss difference between the signal lines with different lengths. The least significant 3 bits are implemented with the modified structure of the SL PS, which reduces the size further by replacing a reference line by a series switch. The test chip is fabricated in a 65-nm CMOS process. It operates in the range of 20–30 GHz occupying a 0.18 mm2 core size. Its measured insertion loss and IP1dB are 11 dB and 6.5 dBm at 28 GHz, respectively. The measured gain error and rms delay error are less than 2 dB and 0.7 ps at operation frequencies. [ABSTRACT FROM AUTHOR]

This paper presents a 300-GHz voltage-controlled oscillator (VCO) with a wide frequency tuning range and high output power. To generate fundamental oscillation at 300 GHz, a cascode cross-coupled pair is employed as a VCO core instead of a conventional common-emitter pair. Capacitive emitter degeneration is added to the VCO core to achieve a wide bandwidth of a negative conductance. In addition, the phase of the oscillation feedback loop is analyzed and optimized to further extend the tuning range. The VCO is fabricated in a 0.25- $\mu \text{m}$ InP DHBT technology ($f_{\mathrm {T}}/f_{\mathrm {max}} = 392$ /859 GHz). Measurements show that the VCO frequency is tuned from 272.4 to 310.8 GHz with a peak output power of 1.5 dBm. To the best of authors’ knowledge, this is the widest tuning range of 38.4 GHz (a fractional bandwidth of 13.2%) among the reported fundamental VCOs at the WR-3 band. [ABSTRACT FROM AUTHOR]

In this paper, we introduce the first integrated circuit (IC) implementation of spatiotemporally modulated angular-momentum (STM-AM)-biased magnetless circulators. The design is based on a modified current-mode topology, which is less sensitive to parasitics and relies on switched capacitors rather than varactors to achieve the desired modulation, thus reducing the circuit complexity and easing its chip-scale realization. We analyze the presented circuit and study its performance in the presence of inevitable nonidealities using an in-house so-called composite Floquet scattering matrix (CFSM) numerical method. We also validate the analysis with simulated and measured results using a standard 180-nm CMOS technology, showing good performance. Compared to previous discrete implementations of STM-AM circulators, the presented CMOS chip reduces the form factor by at least an order of magnitude and occupies a total area of only 36 mm2. [ABSTRACT FROM AUTHOR]

A new kind of contactless electromagnetic bandgap (EBG) structure in the form of interdigital-pin bed of nails is introduced for the first time in this paper. It consists of two metal plates with interdigital-pin bed of nails face to face with each other, where each pin is surrounded by four pins on the other plate. The working mechanism of the interdigital-pin contactless EBG structure is suppressing the modes supported by the parallel plate waveguide (PPW) by loading interdigital pins inside the PPW. The advantage of the interdigital-pin lattice is there is a significant pin gap increase. This lattice makes the minimum pin gap that could be processed by the machining center, after assembling, reduced from the diameter of the milling clutter to its radius. It provides a way to process EBG structures at higher frequency band with the same milling cutter. The cases the pins allocated between the two plates in a random manner are also studied. Compared to its traditional counterpart, the stopband is stable with a small variation. A W-band groove gap waveguide (GGW) prototype with interdigital-pins and a Ka-band GGW with randomly allocated pins are designed, manufactured, and tested. The measured results agree well with the simulation. [ABSTRACT FROM AUTHOR]

Measurement-based black box behavioral models are widely used nowadays. To handle nonlinear effects efficiently, such models often rely on approximation techniques. Polyharmonic distortion (PHD) modeling emerged as a viable approach for describing a nonlinear mapping. Typical PHD-based models, such as the well-known $X$ -parameter model, are gained from linearization while operating on a certain large signal (LS) operational point. This limits the accuracy, especially for hard nonlinearities. However, quadratic terms can be added, which result in the quadratic PHD (QPHD) model. This enables highly accurate models for devices in strongly nonlinear operation, even in highly mismatched environments. In this paper, the accuracy of such models is investigated by predicting typical nonlinear measures, such as load–pull contours and intermodulation distortion, to assess the model accuracy for both static and dynamic stimulus. Furthermore, the LS matching problem is solved for both the $X$ -parameter and the QPHD model. This allows to predict the optimum matching analytically, without performing load–pull analysis. To verify the accuracy of the model, the results are presented by comparing the model prediction with verification measurements for a commercially available GaN HEMT. [ABSTRACT FROM AUTHOR]

In this paper, a new method to develop balanced-to-unbalanced (BTU) filtering out-of-phase power divider (PD) is presented. Based on the comparison between BTU filtering out-of-phase PD and balanced-to-balanced (BTB) filter, it is found that the BTU filtering out-of-phase PD can be constructed by combining a BTB filter and an additional parallel four-port network. The design equations are derived and corresponding circuit models are given. Finally, a prototype is designed to verify the theoretical prediction. The design procedure and parameter selection are detailed. The good performance and the consistency between the simulated and measured results verify the design theory. [ABSTRACT FROM AUTHOR]

Silicon-based millimeter-wave (mm-wave) phased-array technologies are enabling directional wireless data communications at Gb/s speeds. In this paper, we review and discuss the challenges of implementing a multichip phased-array antenna module for mm-wave applications using organic buildup substrate technology. A prototype test vehicle has been fabricated and studied to evaluate the antenna and interconnect performance, dielectric properties, package substrate warpage conditions at different temperatures, chip- and board-level joint process reliability, and thermal management feasibility for cooling. Based on the learning from the test vehicle, an organic-based multilayered phased-array antenna package for 28-GHz mm-wave radio access applications is implemented. The package incorporates 64 dual-polarized antenna elements and features an air cavity common to all antennas. Direct probing measurements on a single-antenna element of the package show over 3 GHz of bandwidth and 3-dBi gain at 28 GHz. A phased-array transceiver module has been developed with the package; the module includes four SiGe BiCMOS ICs attached using flip-chip assembly. Module-level measurements in the TX mode show a 35-dB near-ideal output power increase for 64-element power combining; 64-element radiation pattern measurements are reported with a steering range of ± 50° without tapering in off-boresight directions, and 64-element radiation pattern measurements with tapering show achievement of a sidelobe level lower than −20 dB. The transceiver modules achieved 20.64-Gb/s throughput with 256 QAM and 800-MHz bandwidth in direct over-the-air link measurement results. [ABSTRACT FROM AUTHOR]

Terahertz (THz) sources with stabilized output frequencies are desired in many systems, however, the design of conventional THz phase-locked loops encounters many challenges. In this paper, a fully on-chip frequency-stabilization feedback mechanism is proposed, which avoids the use of both frequency dividers and the off-chip reference, achieving much lower power consumption and system integration cost. Using this scheme, two circuit prototypes are designed in a 0.13- $\mu \text{m}$ SiGe BiCMOS technology. The first one is a 302–332-GHz frequency-stabilized source with ultralow power consumption. It achieves a −13.9-dBm probed output power with a dc power consumption of only 51.7 mW. The second design is a 308–317-GHz frequency-stabilized high-output-power radiating array, which achieves a peak-radiated power and EIRP of 4.6 mW and 24.7 dBm, respectively, with a total dc power consumption of 1.18 W. With significantly lower system integration cost and power consumption, the proposed scheme is attractive for many applications that require short coherence time, such as THz active imaging systems and short-range millimeter-wave (mm-wave)/THz FMCW radars. With further calibration and enhancement in long-term stability, this scheme will also be useful in systems like communication transceivers. [ABSTRACT FROM AUTHOR]

A fast and accurate calculation of the resonant frequency of a solenoid coil is needed in many applications, e.g., wireless power transfer and magnetic resonance imaging. It helps to accelerate the design and optimization of a coil. However, the existing calculation models for the key equivalent parameters, the inductance ($L$) and the capacitance ($C$), of the solenoid coils can only provide estimations for standard tightly wound cylindrical coils, and the accuracy is not high. There are no accurate models available for calculating $L$ , $C$ , and the resonant frequency when a solenoid becomes irregular, e.g., when it is sparse (with a large pitch), when it has nonuniform pitches, or when it is noncylindrical. In this paper, we propose a fast and accurate model for such an irregular solenoid coil to calculate its inductance, capacitance, and, thus, the resonant frequency. The accuracy of the proposed model is tested on the solenoid coils (with large pitches, nonuniform pitches, or noncylindrical shape) by comparing the calculated results to those using commercial simulation software and the measurement results. For a sparsely wound solenoid, the proposed model provides an accurate calculation of the inductance with a maximal pitch-to-wire-diameter ratio of 40 (an error rate of 8.33% at this ratio). For a varied-pitch solenoid and a noncylindrical one, an error rate of less than 5% can be achieved for a calculation of the inductance. [ABSTRACT FROM AUTHOR]

A phase-coherent technique for multiple all-digital phase-locked loops (ADPLLs) is presented and developed in this paper to target a 57–63-GHz multiple-input multiple-output (MIMO) transmitter (TX) with a digital beam-steering capability. The ADPLL TX chains are first fabricated in nanoscale CMOS and then time-synchronized and frequency–phase locked by a field-programmable gate array (FPGA) evaluation board. The calibration approach for phase alignment is carried out using a cancellation method to acquire the out-of-phase state within two ADPLLs. The accuracy of beam steering and phase alignment is investigated and analyzed based on a time-domain model for ADPLL to consider the impact of phase noise. The analysis results offer the required values of the ADPLL parameters to allow a millimeter-wave (mm-wave) MIMO TX with a highly accurate digital beam-steering capability. [ABSTRACT FROM AUTHOR]

This paper reports a transmit–receive (Tx–Rx) front-end (FE) in bulk CMOS targeting fifth-generation (5G) mobile user equipment (UE)-phased arrays. Block-level specifications are first reviewed based on link budget and UE array beam steering considerations, and compared against measured standalone power/low-noise amplifier and phase shifter test circuit performances. Then, the codesign of the Tx–Rx switch and antenna impedance matching is investigated for the important case of wideband dual-resonance networks, leading to a proposed topology that is experimentally verified using silicon passive test structures. A fully integrated FE prototype is fabricated in 1.1-V 1P6M 40-nm bulk CMOS and characterized in detail across digital gain and phase settings. Measurements show Tx-mode $P_{\mathrm {1\,dB}}$ /PAE1 dB ≥ 14.6 dBm/21.9% across 27–30 GHz, and peak $P_{\mathrm{ out}}$ /PAE = 6.5dBm/8.8% at 27 GHz for an $8\,\,\times100$ -MHz carrier-aggregated 64-QAM OFDM signal. In Rx-mode, a noise figure of 5.5–6 dB and an input-referred third-order intercept point of −8.5 to −6 dBm are achieved across 27–33 GHz. Normalized to area/power consumption, the achieved performance is the state of the art relative to the most recent CMOS/SiGe FEs. [ABSTRACT FROM AUTHOR]

In this paper, a novel high-efficiency, low-cost, and low-complexity RF-to-dc converter was designed for RF energy harvesting in the 2.4-GHz band. The proposed design has two RF inputs and maintains high efficiency over a wide range of incoming incident wave angles. The circuit is based on a Wilkinson power combiner and has two single-diode rectifiers. One rectifier is connected at the combiner’s output and collects the energy coming from the two inputs. The second rectifier replaces the isolation resistor of the combiner in order to collect the power that would, otherwise, be dissipated in it. The second rectifier is used for recycling the wasted power when the input signals do not have the same phase. The novel RF-to-dc converter was fabricated using the commercially available components and a low-cost FR-4 substrate. A prototype was designed, and its efficiency was optimized for low-power input levels. The measured system efficiency was 16.2% for in-phase input signals with an available input power of −17 dBm. When the relative phase of input signals varied from 0° to 360°, a variation in efficiency between 15.3% and 22% was observed. For an input power of 3 dBm, the efficiency varies from 26% to 39% between 0° and 360° phase difference. [ABSTRACT FROM AUTHOR]

In this paper, a newly shunted-line stepped-impedance resonator (SLSIR) is studied and applied to realize high-order balanced filter design for radio astronomy application. The proposed SLSIR not only has more flexible control of the internal coupling between adjacent units but also provides more design freedom for the cascade connection of high-order filter. Then, the operating theory of three kinds of electrically, magnetically, and electromagnetically coupled SLSIR pairs has been discussed and utilized to high-performance filter design. Hence, fourth-order balanced filter using electromagnetically coupled SLSIR pairs is investigated and designed, which exhibits an excellent filtering performance under differential-mode (DM) operation as well as a high common-mode (CM) suppression level. In addition, the production mechanism of DM transmission zero is modeled and analyzed. Based on the analysis above, two dissimilar types of coupled SLSIR pairs with the same fundamental frequency but different harmonics are adopted to design an eighth-order balanced filter. Finally, the high-order balanced filter is fabricated on 0.5-mm-thick MgO wafer with double-sided YBCO thin films. Measured results show that the eighth-order balanced filter operates at 2.53 GHz with the corresponding in-band insertion loss of 0.1 dB. Results well verify the proposed structure with high selectivity, low insertion loss, and wide stopband performances. [ABSTRACT FROM AUTHOR]

In this paper, we present a frequency-tunable constant-bandwidth waveguide filter structure with contactless tuning plungers. For the purpose of adjusting the center frequency of the filter, we, for the first time, developed the contactless plungers of waveguide corrugation structure. The new plungers do not require any electrical and mechanical contacts with the waveguide circular resonators, and this allows the plungers to move freely. Although each plunger does not have electrical and mechanical contacts with each resonator, its ${Q}$ -factor is comparable to a conventional resonator with no openings. We have also developed a design method for a frequency-tunable waveguide filter capable of having a constant absolute bandwidth. The tuning plungers are used only for the resonators, and the coupling structures are designed to be static in order to minimize the number of tuning devices. For demonstration, a fourth-order waveguide filter has been designed, fabricated, and measured. The measurement shows that it can be tuned from 19.00 to 19.48 GHz having the absolute bandwidth of 54.5 ± 2.5 MHz. [ABSTRACT FROM AUTHOR]

5G massive MIMO devices require over-the-air (OTA) calibration and RF measurement in a phase coherent test system. Device and antenna array size make it very challenging to measure RF performance in a true far-field OTA environment due to the large distances required, which also impact the link budget and test system cost. This paper presents a millimeter-wave (mmWave) midfield (MF) OTA RF performance test system designed to minimize size and cost. This system can perform antenna array phase coherence calibration and support RF parametric measurement per 3GPP conformance test specifications. An overview of system design challenges and measurement approaches is provided. Detailed theoretical analysis and simulation of the MF OTA test method are provided, together with experimental validation of the system’s performance to prove its effectiveness in OTA phase coherence calibration and in RF parametric measurement for 5G massive MIMO devices. [ABSTRACT FROM AUTHOR]

A wideband hybrid mode-switching push–push oscillator with low phase noise is presented in this paper. To achieve the wide tuning range, the inductive and capacitive hybrid mode-switching technique is proposed for the first time. It introduces more freedom of design parameters (i.e., inductance and capacitance) in the resonant tank. Under certain tuning range requirement, the hybrid mode-switching oscillator achieves higher input impedance of the resonator compared to the conventional mode-switching oscillators. Meanwhile, a transformer-coupled inductor ring with symmetrical layout configuration is proposed to realize the switch-less hybrid mode switching, which further improves the circuit performance at sub-THz. Therefore, a good phase noise performance can be obtained within a wide tuning range, which leads to a relaxed tradeoff between the phase noise and tuning range. To verify the aforementioned mechanism operating at sub-THz band, a hybrid mode-switching oscillator based on the dual-mode push–push topology is proposed and fabricated in a conventional 28-nm CMOS technology. The measured results show a 21.7% tuning range with the center frequency of 169.6 GHz and a state-of-the-art FoMT of −180.6 dBc/Hz. The core circuit only occupies 0.039 mm2, while drawing 95 mW with a 0.9-V supply. [ABSTRACT FROM AUTHOR]

In this paper, a systematic research campaign on eighth-mode substrate integrated waveguide (EMSIW) filters is reported. The sizes of these EMSIW resonant cavities are only one-eighth or one-sixteenth of a conventional SIW resonant cavity. Two different coupling topologies, i.e., electric coupling and magnetic coupling, are employed between two EMSIW resonant cavities, which are analyzed theoretically via the response of the structure and the relationship between the cavities. Both coupling topologies enable structural variations that possess advantages and flexibility of the second-order EMSIW bandpass filters (BPFs) designing. By utilizing these basic coupling mechanisms, multilayer board technology, and other practical techniques, a class of triple-order SIW BPFs with the merits of compact size and high selectivity are demonstrated. Specifically, several triple-order EMSIW BPFs composed of pure EMSIW cavities or comprised by combining EMSIW and quarter-mode SIW cavities are simulated, fabricated, and measured for verification. [ABSTRACT FROM AUTHOR]

In this paper, we present a new filtering power divider structure that has a reflectionless response at the two output ports and excellent isolation performance between the two output ports. Hence, the presented filtering power divider can be employed in, for example, combining two signals in two paths without producing signals reflected back to both paths. For obtaining the aforementioned new features of the presented filtering power divider, we have developed a new isolation network made with a resonator, two resistors, and two inverters. We provide analytic design equations so that time-consuming optimization or parametric study is not required in designing filtering power dividers. For verifying the new divider structure and the design equations, we have designed, fabricated, and measured a second-order microstrip reflectionless filtering power divider. [ABSTRACT FROM AUTHOR]

This paper presents the design and characterization of millimeter-wave (28/38 GHz), circularly polarized (CP) active antennas, suitable for future 5G services. By augmenting the modeling capabilities of commercially available nonlinear CAD tools, the active antenna design can simultaneously optimize figures of merits for both radiation and nonlinear (NL) performance. The radiating part is computed and optimized layoutwise by means of an artificial neural network (ANN), suitably trained off-line. For the NL design purpose, the harmonic neural network (HNN) of the antenna is subsequently implemented as a standard circuit component, to include the antenna behavior at all the harmonics of its NL regime. This allows avoiding time-consuming electromagnetic (EM)-simulations in the harmonic balance optimization loop. In this way, a well-defined interface between the antenna and the amplifier can be avoided. To demonstrate the effectiveness of the design approach, one active integrated antenna (AIA), consisting of a class AB amplifier feeding a CP patch at 38 GHz, has been fabricated with the standard 0.1- $\mu \text{m}$ AlGaAs-InGaAs pHEMT technology and extensively measured with respect to both the electrical and radiation performances. To reduce fabrication costs, hybrid integration of the antenna and amplifier connection is used, and the antenna is incorporated into the main PCB. [ABSTRACT FROM AUTHOR]

This paper investigates the linearization of high-efficiency multistage PAs through gate bias modulation derived from the envelope of the RF input signal. We show that separate control of the driver- and power-stage gate bias voltages allows for independent linearization of gain and phase. An iterative algorithm determines signal-dependent gate voltage functions that minimize amplitude-to-amplitude (AM/AM) and amplitude-to-phase (AM/PM) distortion, and is demonstrated on a 10-W high-efficiency X-band GaN monolithic microwave integrated circuit (MMIC) PA with a custom-designed hybrid dual-gate bias modulator. The noise power ratio (NPR) of a 5-MHz-wide signal is improved by as much as 9.4 dB compared to the PA with a static bias, without degradation in power-added efficiency (PAE) and gain. The measured average PAE improves from 19.9 % at 9.8-dB backoff by 0.8 points, with a saturated gain increase of 0.2 dB at 9.7 GHz. A long-term evolution (LTE) signal with different envelope statistics and a 10.6-dB peak-to-average power ratio (PAPR) is amplified with an adjacent channel power ratio (ACPR) improvement of up to 7.9 dB. [ABSTRACT FROM AUTHOR]

Accurate and precise knowledge of the relative permittivity of printed circuit board (PCB) materials is essential for the reliable design of high-frequency circuits. For simplicity reasons, planar, resonant permittivity sensors, which are directly integrated on the unknown PCB material, are widely used. However, the sensors are affected by the nonidealities of the copper-clad laminate and PCB manufacturing process, e.g., the difference in roughness between the top and bottom sides of each metal layer. This paper analyzes the influence of these nonidealities on the extracted relative permittivity values of different sensor geometries in microstrip and substrate integrated waveguide (SIW) technology up to 100 GHz. Microstrip resonators are very sensitive against the investigated nonidealities. Additional roughness measurements and more detailed simulation models cannot noticeably reduce the uncertainties. SIW cavity sensors are more robust, and simple modeling approaches lead to low uncertainties smaller than 0.05 for the whole frequency range from 10 to 100 GHz. [ABSTRACT FROM AUTHOR]

This paper demonstrates an eight-element multiple-input-multiple-output (MIMO) hybrid beamforming receiver array with autonomous millimeter-wave (mm-Wave)/RF front-end beamforming and digital baseband beamforming. It enables autonomous dynamic suppression of unknown blockers and beamforming on unknown desired signals, without knowing their carrier frequency, angle-of-arrival (AoA), and modulation scheme as a priori. After autonomous cancellation of an in-band/cochannel wideband-modulated blocker, a wideband-modulated desired signal is measured with high SNR, achieving −25.7-dB EVM for 6-Gb/s 64 QAM and −31.8-dB EVM for 1.6-Gb/s 256 QAM. Without baseband DSP beam-searching, the closed-loop mm-Wave/RF front-end beamformer (BF) realizes <1- $\mu \text{s}$ rapid response per stage, 100-to- $1000\times $ faster than existing mm-Wave analog/digital BFs with DSP beam-searching. The eight-element MIMO receiver array covers a wide frequency range (23–30 GHz) and the full field-of-view (FoV) to address future low-latency applications of practical 5G MIMO systems. To the best of our knowledge, this is the first MIMO receiver array enabling autonomous wideband-modulated 64-/256-QAM blocker rejection and desired signal beamforming with $\mu \text{s}$ response time. [ABSTRACT FROM AUTHOR]

In this paper, we characterize the signature of traps existing in the new AlGaN/GaN HEMT of 0.15- $\mu \text{m}$ ultrashort gate length and $8 \times 50\,\,\mu \text{m}^{2}$ gate width (GH15) through three different measurement techniques which are low frequency (LF) S-parameters, drain-current deep level transient spectroscopy (I-DLTS), and LF drain noise characterization. These three different measurements techniques were performed for varying chuck temperatures ($T_{\mathrm {chuck}}$) ranging between 25 °C and 125 °C and for the same biasing condition. All measurements ensure approximatively the extraction of the same signature of traps [apparent activation energy ($E_{a}$) and cross section ($\sigma _{n}$)] existing in the UMS device. Furthermore, we have characterized the thermal resistance ($R_{\mathrm {TH}}$) using pulsed $I$ – $V$ measurement and a two-step calibration process. The determination of $R_{\mathrm {TH}}$ is important to evaluate the device and to know precisely the signature of traps $E_{a}$ and $\sigma _{n}$ defined by the Arrhenius equation. A large signal measurements using an unequally spaced multitone (USMT) signal were done in order to evaluate the performance of GH15 transistor around the optimum load impedance in terms of efficiency (max PAE ~ 55%). The leakage current which measured before and after all measurements for $V_{\mathrm {GS}} = -6$ , −7 V and for $V_{\mathrm {DS}}$ varying from 0 to 10 V was lower than $100~\mu \text{A}$ /mm. To our knowledge, results on charge-trapping and large-signal performance are reported for the first time in 0.15- $\mu \text{m}$ technology. [ABSTRACT FROM AUTHOR]

This paper introduces a new method to suppress the undesired spatial leakage of a 76-GHz phased array. In this system, $8 \times 1$ antenna elements on board are driven by digitally modulated quadrature phase shift keying (QPSK) and on–off keying (OOK) elements fabricated in 28-nm bulk CMOS. The total number of the eight-element output combinations is as large as 5&8hat;, and QPSK and 16 quadrature amplitude modulation (QAM) constellation can be formed at the broadside direction ($\theta = 0^{\circ }$) by numerous qualified combinations. The peak array effective isotropic radiated power (EIRP) is measured at 31.6 dBm, and the EIRP for the redundancy-rich spatially synthesized QPSK (with eight elements) and 16QAM (with six elements) constellations are 28.5 and 23.3 dBm, respectively. The redundancy is utilized to alleviate the array spatial leakage: For a given zenith angle requiring a low leakage, the qualified combinations corresponding to the lowest leakage is adopted, and the broadside performance is not affected. Unlike conventional approaches, fine-grain magnitude and phase control for the elements are not required in synthesizing the low leakage. Simulation shows that the leakage power can be suppressed to −25 dBc for most zenith angles between 10° and 50°, supported by the measured results. [ABSTRACT FROM AUTHOR]

This paper presents three millimeter-wave (mm-wave) continuous-mode power amplifiers (PAs) for fifth-generation (5G) MIMO applications, including a two-stage differential continuous-mode Class-F−1 PA in 130-nm SiGe process, a single-stage differential continuous-mode hybrid Class-F/F−1 PA in 45-nm SOI CMOS process, and a two-stage differential continuous-mode hybrid Class-F/F−1 PA in 45-nm SOI CMOS process. The first PA design covers 19–29.5 GHz, while the other two designs cover 23–41 GHz, all covering multiple 5G bands (24/28/37/39 GHz). All the presented PA designs are based on a proposed transformer-based continuous-mode harmonically tuned PA output network. This network provides proper harmonic impedance terminations for the fundamental, second-order, and third-order harmonic impedances, which supports continuous-mode Class-F−1 or hybrid Class-F/F−1 PA operations to achieve ultrawide bandwidth yet high efficiency. The first PA design achieves a wide $P_{\mathrm {sat}}~1$ -dB bandwidth of 19–29.5 GHz (43.3%) and high peak power-added efficiency (PAE) (43.5%). The second design achieves an ultrawide $P_{\mathrm {sat}}~1$ -dB bandwidth of 23.5–41 GHz (53.3%) and high peak PAE (46%). Moreover, it achieves 43.4% PAE and 18.6-dBm $P_{\mathrm {sat}}$ at 27 GHz, 40.2% PAE and 18.6-dBm $P_{\mathrm {sat}}$ at 37 GHz, and 41.2% PAE and 18.5-dBm $P_{\mathrm {sat}}$ at 39 GHz, respectively. The third PA design also achieves an ultrawide $P_{\mathrm {sat}}~1$ -dB bandwidth of 23.5–41 GHz (53.3%) and high peak PAE (43.2%). It achieves 43% PAE and 18.9-dBm $P_{\mathrm {sat}}$ at 27 GHz, 37% PAE and 19-dBm $P_{\mathrm {sat}}$ at 37 GHz, and 36% PAE and 18.9-dBm $P_{\mathrm {sat}}$ at 39 GHz, respectively. Extensive 64-/256-QAM modulation tests demonstrate the high PA linearity. Our proposed PA designs outperform the reported mm-wave silicon-based 5G PAs in terms of high efficiency over an ultrawide bandwidth. [ABSTRACT FROM AUTHOR]

In this paper, a Ka/Q dual-band Doherty power amplifier (DPA) with simplified offset lines is implemented in a 0.1- $\mu \text{m}$ gallium arsenide (GaAs) process. It is found that the dual-band transmission lines (TLs) employed in the sub-6-GHz dual-band DPA are not suitable to be used as the offset lines in millimeter-wave (mm-wave) dual-band DPAs due to their large sizes and insert losses. An in-depth analysis reveals that the phase requirement of the offset lines can be relaxed, and the DPA exhibits a reasonable performance in a certain phase-shift range. A novel design method is proposed to realize offset lines using simple TLs, which can satisfy the phase-shift ranges in dual bands by choosing a proper electrical length. To enhance the gain of the DPA, a reversed uneven power splitter is adopted to deliver more power to the main power amplifier (PA). The fabricated DPA achieves an output power of 25.4/25.2 dBm, a peak power-added efficiency (PAE) of 33%/25%, and a 6-dB back-off PAE of 22%/17% at 29/46 GHz, respectively, with a compact size of 2.2 1.4 mm2. Applying a 20-MHZ 64-quadratic-amplitude modulation (QAM) signal with a 7.7-dB peak-to-average power ratio (PAPR), the measured average output power, PAE, and error vector magnitude (EVM) at 29/46 GHz are 18.4/19 dBm, 17%/15%, and 1.5%/1.1% after linearization, respectively. To the best of our knowledge, the proposed DPA is the first demonstration of mm-wave dual-band DPAs that do not require any additional switching or reconfiguration. [ABSTRACT FROM AUTHOR]

This paper reports a 60-GHz four-element beam-tapering phased-array transmitter with a lower sidelobe level (SLL). The array factor and the error vector magnitude (EVM) were calculated to explain the low sidelobe characteristic of a nonuniform amplitude array and to emphasize the importance of phase compensation, respectively. The phase-compensated radio frequency (RF) variable gain amplifiers (VGAs) were proposed to compensate the gain variance of phase shifters and, simultaneously, excite the nonuniform amplitude to each array element. The proposed VGA improves the relative phase error by 2° and the OP1dB by 2.4 dB within a gain control range of 5 dB, compared to the current steering without any compensation. Implemented in a commercial 65-nm CMOS process, the integrated array chip displays an root-mean-square (rms) gain error of <0.53 dB and an rms phase error of <8.8° in the frequency range of 57–66 GHz, while consuming a dc power of 403.2 mW and occupying a chip area of 2.88 mm2. The fabricated array was integrated with a $1 \times 4$ Teflon array antenna to verify the beamforming and beam-tapering operations. With proper gain and phase control, the integrated array decreases the SLL by up to 5.2 dB, and the minimum SLL is −15.2 dB. To the best of the authors’ knowledge, this is the first report on the implementation of CMOS beam-tapering arrays in the 60-GHz band. [ABSTRACT FROM AUTHOR]

Distributed multiple-input-multiple-output (D-MIMO) is a very promising technique to improve capacity and quality of service for emerging 5G systems. In this paper, we propose a flexible and low-cost testbed for D-MIMO systems, where a sigma–delta over fiber (SDoF) solution is proposed to address the fundamental challenge of phase-coherent transmission between multiple distributed access points (APs) from a central unit (CU). Employing low-cost standardized optical data interconnects, SDoF, brings a very flexible and software controlled transmission of RF signals over optical fiber. An SDoF-based D-MIMO testbed with a CU feeding 12 distributed APs has been realized and experimentally evaluated. Initial experiments of D-MIMO and conventional colocated MIMO systems at 2.365 GHz have been performed to demonstrate the flexibility and potential of the proposed testbed as a new powerful tool in the design and analysis of emerging communication system concepts. [ABSTRACT FROM AUTHOR]

Verification of physical (PHY) layer and medium access control (MAC) layer procedures of the fifth-generation (5G) specifications with real hardware prototypes is important in the commercialization of 5G mobile communication systems and is challenging as well. In this paper, we propose a flexible software-defined-radio (SDR)-based prototype hardware design for user equipment (UE), which can be used to implement novel 5G communication concepts. The proposed hardware architecture is featured by using a flexible baseband signal processing module and two independent programmable wideband radio frequency (RF) front ends that, respectively, cover the lower and higher frequencies of sub-6-GHz band. The flexibility of the baseband signal processing module is ensured by using four powerful field-programmable gate arrays (FPGAs) running the PHY entities and a powerful FPGA-based system-on-chip running the MAC entities. The flexibilities of the RF front ends lay in the facts that: 1) the design covers three sub-6-GHz frequency bands, that is, 2.5, 3.5, and 4.9 GHz; 2) it can support dual connectivity for the upcoming 5G networks; and 3) it enables carrier aggregation (CA) over up to three carriers to achieve 300-MHz bandwidth. Accordingly, this prototype is capable of verifying the complicated scheduling procedures, evaluating the sophisticated signal processing algorithms in both PHY and MAC layers, and supporting the 100-MHz 4T4R multiple-input multiple-output (MIMO) or 200-MHz 2T2R MIMO techniques. Experiments have been performed on 256-QAM modulated waveforms to assess transmission power, error vector magnitude, adjacent channel leakage ratio from the UE side, and peak data rates between a base station and the UE. [ABSTRACT FROM AUTHOR]

Multiple-input and multiple-output (MIMO) over-the-air (OTA) measurements have helped 4G wireless systems significantly for the communication throughput and to enhance the network stability. However, there remains a potential challenge, which may substantially obstruct the OTA test methodologies being adopted in 5G evaluations. According to the MIMO OTA measurement standards, throughput tests should be conducted in the far-field. As a result, a general system covering all the 4G frequency bands should be larger than 3.6 m, and even tens of meters for 5G. In addition to the cost of the chamber hardware, a sizeable footprint of building space is also required for the test system. Consequently, conducting far-field tests directly incurs excessively high costs in 5G. A compact system with dimensions of 1.9 m for 5G MIMO OTA is proposed in this paper, where a near-field to far-field transformation method is adopted into the current standard MIMO OTA test approach (the radiated two-stage approach), and the throughput in the near field is measured. Compared to existing test systems, the compact solution can achieve a cost reduction by at least an order of magnitude and obtain comparable results as a full-scale certification system. [ABSTRACT FROM AUTHOR]

This paper presents a 28-GHz low-cost high-precision phased array for fifth-generation millimeter-wave communications. The local oscillator (LO) phase shifting approach and the subharmonic mixing technique are adopted to achieve a full 360° phase-shifting range with up to 10-bit phase resolution and ultralow magnitude deviation. Each phased channel in this array contains a 1-bit 180° intermediate frequency phase shifter and a low-voltage varactor-tuned reflective-type phase shifter at LO path. The LO phase shifting is used to achieve fine phase shifting with low-magnitude variation. The subharmonic mixing enables lower phase range and lower operation frequency at the LO path. The measured root-mean-square phase error and magnitude variation are around 0.3° and 0.1 dB, respectively. The over-the-air phased array calibration and measurement are also performed. The eight-element phased array achieves +/−50° beam scanning angle and fine beam resolution less than 1° step. The gain flatness of the phased array is less than +/−1dB at 1-GHz signal bandwidth. The eight-element array achieves an effective isotropic radiated power of 41 dBm at 10-dB power backoff. The measured error-vector-magnitude is 1.72% with a 500-MHz orthogonal-frequency-division-multiplexing QAM-64 signal. [ABSTRACT FROM AUTHOR]

It is well established that the utilization of unused millimeter-wave (mmWave) spectrum is inevitable due to unavailability of required bandwidth in the conventional RF band to support the high data demands of 5G. Large antenna arrays with beamforming capabilities are required to compensate for the high path loss at mmWave frequencies. We are at the verge of a massive mmWave radio front-end deployment, and low-complexity low-cost hardware beamforming solutions are required now at this stage than ever before. In this paper, one such solution is demonstrated and analyzed. A high-performance and low-complexity lens-based beamformer consisting of constant dielectric material ($\epsilon _{r}$) with antenna feeds is presented for multibeam operation. A prototype is developed based on the classical synthesis approach, and in line with the requirements of mmWave hybrid multiuser multiple-input multiple-output (MU-MIMO) systems. A characterization at 28 GHz is performed wherein an uplink signal-to-noise ratio of user terminals is evaluated with the zero-forcing (ZF) baseband signal processing. Radiation performance of a single-source beamformer is measured in an anechoic environment, and end-to-end ergodic sum spectral efficiency performance is estimated based on the measured data. It is shown that the constant- $\epsilon _{r}$ -based beamformer solution is simple, yet significantly outperforms conventional antenna array beamformers with analog phase shifter networks, making it a promising candidate for future hybrid massive MIMO systems. [ABSTRACT FROM AUTHOR]

This paper presents a single-bit RF transmitter based on single-bit switched-capacitor RF digital-to-analog converters (DACs) embedded in an finite-impulse response (FIR) filter (FIR-DACs). The transmitter system comprises a single-bit quadrature delta–sigma modulator ($\Delta \Sigma \text{M}$), a digital mixer, and a 109-tap RF FIR-DAC stage with a single external inductor, combining D–A conversion with discrete- and continuous-time filtering. The on-chip part of the FIR-DAC is built exclusively with CMOS inverters and metal–oxide–metal capacitors, which are implemented in the interconnect layers to propose a compact fully digital solution, suitable for advanced CMOS nodes. A method for canceling redundant switching in the FIR-DAC is proposed to reduce its complexity and power consumption. Combining discrete- and continuous-time filtering, the out-of-band quantization noise of the 1-bit RF signal is strongly attenuated below the level required by emission masks. The RF FIR-DAC prototype is implemented in a 28-nm FD-SOI CMOS technology with ten metal layers and occupies a total active area of only 0.047 mm2. The overall power consumption is 38 mW at 4.6-dBm peak output power, 900-MHz carrier frequency, and 1-V supply. FD-SOI body bias $V_{t}$ tuning is used to effectively correct mixing clock duty-cycle errors in order to perform precise high-frequency I/Q interleaving, which enables high image and local oscillator rejections. The resulting power consumption, surface, and performance of the measured prototype make the proposed circuits and concepts particularly appropriate for use in emerging Internet of Things (IoT) applications. [ABSTRACT FROM AUTHOR]

There has been a growing interest in the commercialization of millimeter-wave (mmW) technology as a part of the fifth-generation new radio wireless standardization efforts. In this direction, many sets of independent measurements show that the biggest determinants of viability of mmW systems are penetration and blockage of mmW signals through different materials in the scattering environment. With this background, the focus of this paper is on understanding the impact of blockage of mmW signals and reduced spatial coverage due to penetration through the human hand, body, vehicles, and so on. Leveraging measurements with a 28-GHz mmW experimental prototype and electromagnetic simulation studies, we first propose statistical models to capture the impact of the hand, human body, and vehicles. We then study the time scales at which mmW signals are disrupted by blockage (hand and human body). Our results show that these events can be attributed to physical movements, and the time scales corresponding to blockage are, hence, on the order of a few 100 ms or more. Network densification, subarray switching in a user equipment designed with multiple subarrays, fall back mechanisms, etc., can address blockage before it leads to a deleterious impact on the mmW link margin. [ABSTRACT FROM AUTHOR]

This paper demonstrates a high-efficiency dual-band RF power amplifier (PA) for sub-6 GHz 5G carrier aggregation. The dual-band PA is tested with modulated signals generated by a new algorithm designed to provide realistic waveforms for carrier aggregation scenarios, allowing flexible complex (IQ) modulated sequences with arbitrary peak-to-average power ratio (PAPR), bandwidth, and band distribution. A single-stage PA is designed with a packaged 6-W transistor and a diplexer-like output matching network that separates the two bands into two outputs. It achieves an output power of 36.7 and 37.1 dBm and a power-added efficiency (PAE) of 40.4% and 39.9% at 3.5 and 5.5 GHz, respectively. Under concurrent, dual-band drive with 10-MHz, 6-dB PAPR signals and with digital predistortion applied to varying frequency notch bandwidths, an average PAE of 25.6%, a normalized mean square error of 2.4%/1.0%, and an adjacent channel power ratio of −46.8/−48 dBc in the two bands (3.5/5.5 GHz) is measured. [ABSTRACT FROM AUTHOR]

A design methodology for a compact millimeter-wave on-chip bandpass filter (BPF) is presented in this paper. Unlike the previously published works in the literature, the presented method is based on quasi-lumped elements, which consists of a resonator with enhanced self-coupling and metal–insulator–metal capacitors. Thus, this approach provides inherently compact designs comparing with the conventional distributed elements-based ones. To fully understand the insight of the approach, simplified LC-equivalent circuit models are developed. To further demonstrate the feasibility of using this approach in practice, the resonator and two compact BPFs are designed using the presented models. All three designs are fabricated in a standard 0.13- $\mu \text{m}$ (Bi)-CMOS technology. The measured results show that the resonator can generate a notch at 47 GHz with the attenuation better than 28 dB due to the enhanced self-coupling. The chip size, excluding the pads, is only $0.096 \times 0.294$ mm2. In addition, using the resonator for BPF designs, the first BPF has one transmission zero at 58 GHz with a peak attenuation of 23 dB. The center frequency of this filter is 27 GHz with an insertion loss of 2.5 dB, while the return loss is better than 10 dB from 26 to 31 GHz. The second BPF has two transmission zeros, and a minimum insertion loss of 3.5 dB is found at 29 GHz, while the return loss is better than 10 dB from 26 GHz to 34 GHz. Also, more than 20-dB stopband attenuation is achieved from dc to 20.5 GHz and from 48 to 67 GHz. The chip sizes of these two BPFs, excluding the pads, are only $0.076\times 0.296$ mm2 and $0.096\times 0.296$ mm2, respectively. [ABSTRACT FROM AUTHOR]

This Special Issue is formed by collecting 46 regular papers on the topic of systems and applications, which reflects the latest progress in microwave systems and applications from MHz to THz. All those 46 papers are divided into six subtopics, namely, digital predistortion of RF power amplifiers (five articles), radar systems and applications (14 articles), wireless systems (nine articles), detectors and imaging (ten articles), microwave applications (five articles), and microwave power transfer technologies (three articles). [ABSTRACT FROM AUTHOR]

The need for accurate material property measurements using microwave cavities requires a form of compensation to correct for changes in temperature and other external influences. This paper details a method for temperature correcting microwave cavity perturbation measurements by monitoring two modes; one which is perturbed by the sample and one which is not (referred to as a nodal mode). The nodal modes used (TM310 and TE311 for an axial sample in a cylindrical cavity) are subject only to sample-independent influences. To demonstrate this technique, the bulk permittivity of a PTFE rod has been measured under varying temperature conditions. The results show that without correction, the measured temperaturedependent dielectric constant has large variations associated with the stepped and linear temperature ramping procedures. The corrected response mitigates systematic errors in the real part. However, the correction of the imaginary part requires careful consideration of the mode coupling strength. This paper demonstrates the importance of temperature correction in dynamic cavity perturbation experiments. [ABSTRACT FROM AUTHOR]

This paper presents a model for the parasitic series resistance and inductance of pads used to on-wafer probing of microstrip-line-fed devices. The model accounts for the frequency-dependent current distribution and skin effects, as well as for the geometry of the pad array, which allows to obtain the series parasitics without the need of measuring a "short" dummy structure. Accordingly, these closed-form formulas can be used by designers in order to predict the series parasitic effects introduced by the pads. In this paper, the proposal is used to correct experimental S-parameters from the pad parasitics on inductor and transmission line measurements requiring the implementation of only an "open" dummy structure. Finally, results as good as those corresponding to using experimental data measured on open and short dummies are obtained up to 40 GHz. [ABSTRACT FROM AUTHOR]

Large metallic losses and short propagation lengths associated with surface plasmons (SPs) have long been considered as the obstacles which severely limit the practical applications of surface plasmonic waveguides. In this paper, we introduce the concept of dielectric spoof SPs (SSPs) and show that subwavelength high-contrast gratings (HCGs) offer a route to effectively suppress the losses and hence dramatically increase the propagation length of surface electromagnetic waves. We experimentally realized a wideband ultra-low-loss high-confinement plasmonic waveguide constructed by a high refractive-index dielectric array with deep-subwavelength periodicity on a metal substrate. Simulation and measurement results on the nearfield distributions and S-parameters at microwave frequencies provide explicit evidences of strong field localization and show excellent transmission efficiency of HCGs-based SSPs across a broad frequency band. More importantly, the propagation length of the HCGs-based SSPs is proved to be at least more than one order of magnitude larger than that of metallic gratings-based SSPs at the same or even higher level of field confinement. Thus, the SSPs as experimentally realized in this paper hold great promise for numerous practical applications in ultra-low-loss and long-range transmission SP devices and circuits and may open up new vistas in SP optics. [ABSTRACT FROM AUTHOR]

A vector-based meshless method or vector meshless method, which is proven to be divergence-free, was recently proposed for transient electromagnetic analysis. In this method, an explicit finite-difference scheme is used for approximating the time derivatives in Maxwell's equations. Therefore, the stability criterion constraints the maximum time-step. This paper presents the alternating-direction implicit (ADI) formulation of the vector meshless method based on a different form of the ADI algorithm named the leapfrog ADI scheme. The computational cost of the leapfrog ADI scheme is less than the conventional ADI algorithm and algebraically equivalent. In the proposed vector meshless method, Courant-Friedrichs-Lewy limit does not constrain the time-step due to its implicit formulation. Moreover, the stability condition of the conventional vector meshless method and the proposed ADI vector meshless method are investigated through their amplification matrices in this paper. The results show that the proposed method has two features: unconditional stability and divergence-free property. The first one is obtained due to the incorporation of the leapfrog ADI algorithm, and the second one is achieved by the use of vector basis functions. The divergencefree property of the proposed method can lead to obtaining more accurate solutions than the conventional meshless method. In addition, some numerical examples are presented to verify the properties and the efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

This paper reviews recent progress of portable short-range noncontact microwave radar systems for motion detection, positioning, and imaging applications. With the continuous advancements of modern semiconductor technologies and embedded computing, many functionalities that could only be achieved by bulky radar systems in the past are now integrated into portable devices with integrated circuit chips and printed circuits boards. These portable solutions are able to provide high motion detection sensitivity, excellent signal-to-noise ratio, and satisfactory range detection capability. Assisted by on-board signal processing algorithms, they can play important roles in various areas, such as health and elderly care, veterinary monitoring, human-computer interaction, structural monitoring, indoor tracking, and wind engineering. This paper reviews some system architectures and practical implementations for typical wireless sensing applications. It also discusses potential future developments for the next-generation portable smart radar systems. [ABSTRACT FROM AUTHOR]

The unique fingerprint spectra of volatile organic compounds for breath analysis and toxic industrial chemicals make an mm-wave (mmW)/THz gas sensor very specific and sensitive. This paper reviews and updates results of our recent work on sensor systems for gas spectroscopy based on integrated transmitter (TX) and receiver (RX), which are developed and fabricated in IHP’s 0.13~\mu \textm SiGe BiCMOS technology. In this paper, we present an mmW/THz spectroscopic system including a folded gas absorption cell of 1.9 m length between the TX and RX modules. We discuss the results and specifications of our sensor system based on integrated TX and RX. We demonstrate TXs and RXs with integrated antennas for spectroscopy at 238–252 GHz and 494–500 GHz using integer- $N$ phase-locked loops (PLLs). We present a compact system by using fractional- {N} PLLs allowing frequency ramps for the TX and RX, and for TX with superimposed frequency shift keying or reference frequency modulation. In another configuration, the voltage controlled oscillators of the TX and RX local oscillator are tuned directly without PLLs by applying external voltages. Further developments of our system are aimed at realizing an even wider frequency span by switching between frequency bands, and to use a more compact gas absorption cell. [ABSTRACT FROM AUTHOR]

This paper presents a new class of dual-band filters and diplexers, realized based on dual-band resonators. The proposed dual-band filter and diplexer do not require junctions and can achieve equivalent performance with fewer cavities, thus offering a significant reduction in size compared with traditional approaches. The concept is potentially applicable to most dual-band cavities and is demonstrated in this paper using elliptical and rectangular waveguide cavities. The first design is an inline structure employing elliptical cavities, whereas the second design is implemented through a unique layout that combines the use of dual-band and single-band rectangular cavities. The result is a group of highly compact dual-band filters and diplexers that offer increased Q and an improved spurious-free window. To verify the concept, an eighth-order Ku-band elliptical dual-band filter and a fourth-order Ku-band rectangular diplexer are designed, manufactured, and tested to allow comparisons with traditional designs. [ABSTRACT FROM AUTHOR]

In this paper, a new type of millimeter-wave waveguide isolator is demonstrated. After developing an analytical model for a rectangular waveguide loaded with stratified media, all the modes propagating through the structure are found. Isolators are then designed by utilizing the frequency ranges where high nonreciprocal attenuation is identified. Here, an isolator is designed to work within the Ka-band by loading a WR-28 waveguide with a transversely magnetized indium antimonide (InSb) slab cooled to 77 K. Measured performance shows more than 20-dB isolation with 1-dB insertion loss, which agrees with theoretical predictions. Moreover, the effects of changing the magnetic bias ( B0 ) and adding dielectric layers above the InSb slab were analyzed theoretically and verified through measurement. Results prove the possibility of achieving high isolation using a weaker magnetic bias by topping the gyroelectric slab with dielectric layers. Nonreciprocal behavior was also demonstrated using an isolator working at 105 GHz, where simulated results show more than 33-dB isolation with 1.16-dB insertion loss. The results presented in this paper could pave the way toward the realization of nonreciprocal components working in the submillimeter-wave and terahertz frequency ranges, where the performance of the classical ferrite device deteriorates. [ABSTRACT FROM PUBLISHER]

In this paper, a new quasi-transverse electromagnetic (TEM) microstrip line, named as packaged microstrip line, is proposed for microwave and millimeter-wave applications. It is comprised of three dielectric substrates: a base layer to place the metal strip, a top layer to build the perfect magnetic conductor (PMC) shielding with periodic plated vias, and a middle layer to separate the PMC layer from the metal strip and the bottom ground plane. With the top PMC shielding, this novel microstrip line no longer suffers from issues of radiation losses, surface waves, or cavity resonances that exist in the classical microstrip line without or with a metallic shielding box. Also, the unwanted higher order mode created in the stripline by any vertical asymmetry between the ground planes will not be generated in the packaged microstrip line. In addition, the fundamental quasi-TEM mode will help this novel line avoid the mode conversion losses when integrated with other quasi-TEM lines, which happen to the substrate-integrated waveguide due to its fundamental TE10 mode. This paper focuses on the effects of the PMC-layer substrate on this line performance. We present how to adopt a proper substrate for each layer of the packaged microstrip line considering both stopband and transmission loss, and how to design the linewidth for a given characteristic impedance. Two different transition schemes of the packaged microstrip line to the standard microstrip line are taken into account. Two prototypes of the proposed packaged microstrip lines using different substrates for the PMC layer are fabricated. The measured and simulated results show good agreement. [ABSTRACT FROM PUBLISHER]

Knowledge of the dielectric properties of human tissues is important for several biomedical applications, including imaging and hyperthermia treatment, as well as for determining safety thresholds in policy making. Breast tissues, both normal and tumorous, are of particular interest because of the medical and social impact of breast cancers. While experimental data is available up to 20 GHz, for higher frequencies, this information is missing, or has been extrapolated from models based on lower-frequency data. Emerging technologies and applications in the millimeter-wave region would benefit from experimental data that bridge this gap. This paper presents the characterization of dielectric properties of breast tissues for the frequency range from 0.5 to 50 GHz. Cole–Cole models are derived for normal and tumorous tissues based on experimental measurements on more than 220 tissue samples obtained at surgery (ex vivo) from a population exceeding 50 patients, covering a wide span of normal and tumorous tissues, from patients ranging in age from 28 to 85 years, with a time from excision to measurements under 3.5 h. This paper also presents a comprehensive analysis of the differences between normal and tumorous breast tissues at different frequencies in terms of sensitivity and specificity. [ABSTRACT FROM PUBLISHER]

In this paper, we present a method to implement digital predistortion (DPD) memory models using lookup tables (LUTs) with linear interpolation and extrapolation. We introduce the required set of basis functions to describe this model. The DPD output is expressed as a linear combination of these basis functions and we show how to directly estimate the LUT entries using least squares. We show how this model achieves lower complexity at similar or better performance compared to polynomial models translated to LUTs with interpolation or models based on LUTs without interpolation whose coefficients are adapted directly. We refer to this model as the direct adaptation of LUTs with interpolation/extrapolation (DLUTI). In this paper we also introduce the composite memory polynomial model: a new polynomial model which is a hybrid between the generalized memory polynomial and the dynamic deviation reduction models. This model is used as a starting point to generate the final LUT-based model. [ABSTRACT FROM PUBLISHER]

Monitoring physiological signs in animal testing is crucial for the development of new therapeutic strategies and better understanding of diseases. This paper exploits Doppler radar and nonlinear phase demodulation effect to achieve noncontact measurement of both displacements and frequencies of a laboratory rat’s cardiorespiratory activities. The implementation of displacement acquisition method relying on demodulation-generated harmonics is described, and this paper provides a guideline of implementing the acquisition method. Demodulation-generated harmonics are analyzed, and the effect of vibration-generated harmonics is studied. To demonstrate the effectiveness, a 60-GHz radar is used that shows good correlation with the instrument-recorded data. Average errors of respiration rate and heart rate (HR) are 0.057% and 0.33%, respectively, using three test subjects. In addition, two drug tests are performed to verify the monitoring function with controlled raised/dropped HR. By observing the time periods before, during, and after drug injection, results of rat’s physiological response to drugs reveal the drug efficacy and body reaction over time. The measured cardiorespiratory variations can provide useful information without using implant devices, and the implementation could be an improvement over current invasive methods. The result presented in this paper is believed to be the first reported simultaneous measurements of both frequencies and displacements of both respiration and heartbeat movements of a laboratory animal using microwave radar. [ABSTRACT FROM AUTHOR]

In this paper, we present a new dynamic-bias measurement setup and its application to the extraction of a nonlinear model for microwave field-effect transistors. The dynamic-bias technique has been recently proposed and relies on the use of low-frequency (LF) and high-frequency (HF) vector-calibrated measurements acquired, for instance, by means of a large-signal network analyzer. In this paper, we propose a new and alternative technique to perform the dynamic-bias measurements, based on relatively low-cost instrumentation commonly available in microwave laboratories. The new acquisition system is composed of a four-channel vector LF receiver (e.g., an oscilloscope) and a one-channel HF scalar receiver (e.g., a spectrum analyzer), which replace the eight-channel vector receiver. Moreover, the proposed architecture greatly simplifies the measurement setup and the calibration procedure. As a case study, a 0.25- \mu \textm GaN HEMT is considered. Dynamic-bias measurements, carried out by means of the proposed measurement setup, are used for the identification of a nonlinear model of this device. Finally, the model is fully validated through comparison with time-domain harmonic load–pull measurements carried out at 5 GHz. [ABSTRACT FROM PUBLISHER]