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This paper presents the design of a broadband power amplifier (PA) in 130-nm SiGe BiCMOS technology. First, a single-stage broadband single-cell PA covering the 4.5–18-GHz frequency band is introduced. In this frequency range, this single cell achieves a measured gain, saturated output power ( Psat), output 1-dB compression point ( P1dB), and power-added efficiency (PAE) in the range from 12.8 to 15.7 dB, 18.8 to 23.7 dBm, 16.7 to 19.5 dBm, and 11.4 to 31.9%, respectively. Its peak saturated output power and maximum PAE are both obtained at 8.5 GHz. Second, to increase the output power, a PA consisting of two parallel broadband cells with a power combination is presented. This PA operates in the 4.5–15.5-GHz frequency range with measured gain, Psat, P1{\rm dB}, and PAE in the range from 11 to 16.6 dB, 21.3 to 25.5 dBm, 18.7 to 21.7 dBm, and 11.9 to 28.7%, respectively. It achieves its peak saturated output power of 25.5 dBm at 8.5 GHz and its maximum PAE of 28.7% with an associated output power of 23.6 dBm at 6.5 GHz. Each of those two PAs achieves better performances than the state-of-the-art in broadband SiGe technology when comparing the output power level and efficiency. [ABSTRACT FROM AUTHOR]

Motivated by advanced-generation signals and corresponding trends for multiband, broadband, and ultra-wideband transmitters, several models have recently been proposed for digital predistortion in a dual-band concurrent transmission. These state-of-the-art models assume that two frequencies of operation are uncorrelated and harmonic products can be filtered out. However, when the harmonic of one signal falls on the frequency band of another signal, it cannot be removed with filters. This paper proposes a 3-D harmonic memory polynomial based model for the dual-band concurrent transmission in the presence of harmonic interferences. The model is extracted and predistortion is implemented using a low-cost field-programmable gate-array-based system including a transmitter and a feedback receiver. Using the proposed model, a performance improvement up to 22 dB in terms of normalized mean square error and performance improvement up to 20 dB in terms of the adjacent channel power ratio is achieved compared to a conventional dual-band memory polynomial model not including harmonics. [ABSTRACT FROM AUTHOR]

We present a fully-integrated 256 QAM single-chip transceiver (TRX) with 300-MHz channel bandwidth at the 6.5-GHz band. A novel architecture for self-interference suppression (SIS) is proposed. A noise-canceling low-noise amplifier with the embedded programmable source degeneration network based on the bond wires, manifesting the notch filtering characteristics of the self-interference signal, has been utilized to facilitate the SIS, and LC-tuned tanks further improve the interference filtering in a receiver (RX) and considerable adjacent channel leakage power ratio in a transmitter (TX). The SAW-less /duplexer-less TRX allows TDD/FDD co-operation in closely spaced channels. The RX achieves a noise figure (NF) as low as 3 dB with +17.5-dBm out-of-band IIP3. The EVM is 2.02% and 2.72% for the RX and TX, respectively, in 160-MHz bandwidth OFDM 256 QAM. In the SIS mode, the blocker P1dB is −8 dBm, and the NF of the RX degrades only 2.1 dB (from 3.0 to 5.1 dB), withstanding 0-dBm interference at 150-MHz offset. The TRX exhibits a slight EVM degradation (from 2.02% to 2.98%) when receiving a −40-dBm 160-MHz bandwidth 256 QAM desired signal, in the presence of a −15-dBm 80-MHz bandwidth self-interference signal at 300-MHz offset. The TRX has been implemented in 0.13- $\mu \text{m}$ CMOS with superior overall performances. [ABSTRACT FROM AUTHOR]

In this paper, a family of broadband differential phase shifters using bridged T-type bandpass networks and their design procedures are presented. Conventional high/low-pass networks are widely applied in 22.5^\circ–90^\circ phase shifters. However, the tradeoff must be made between the bandwidths of return loss and phase error, which are limited to less than 90%. The proposed bridged T-type bandpass network can improve the bandwidth of phase error while keeping good return loss. Theoretically, the fractional bandwidth of a phase shifter using a bridged T-type bandpass network can be improved by more than 40 percentage points as compared with a conventional high-pass network. 22.5^\circ, 45^\circ, and 90^\circ phase shifters are demonstrated on FR4 using discrete surface mounted device (SMD) L/C components. Due to limited discrete SMD component values, the phase and return-loss bandwidths of the realized three phase shifters are slightly reduced, but still larger than 125% and are better than 18 dB from 0.55 to 2.51 GHz. [ABSTRACT FROM PUBLISHER]

A new design methodology is presented for the planar implementation of a classical Marchand balun. A novel intuitive analysis shows that the Marchand configuration can be designed optimally to eliminate the phenomenon of “trace separation,” which is frequently observed in planar implementations. The new theory shows that this unbalancing effect is caused by the parasitic transmission line formed between the inner strip and ground, which is not considered in Marchand's original coaxial structures. Compact design equations are derived, based on which a new innovative structure is proposed and fabricated. This demonstrates the elimination of trace separation and achieves flat equal port split over a double octave bandwidth, performing up to 10 GHz, using an industry standard single-layer thin-film process having a continuous unpatterned ground plane. Popular planar variants of Marchand's original structures are also designed and fabricated to verify the new design equations. These structures are compared in terms of bandwidth, trace separation, and balanced port impedances. [ABSTRACT FROM PUBLISHER]

Two new wideband in-phase and out-of-phase balanced power dividing/combining networks are proposed in this paper. Based on matrix transformation, the differential-mode and common-mode equivalent circuits of the two wideband in-phase and out-of-phase networks can be easily deduced. A patterned ground-plane technique is used to realize the strong coupling of the shorted coupled lines for the differential mode. Two planar wideband in-phase and out-of-phase balanced networks with bandwidths of 55.3% and 64.4% (\vert S{ dd21,31}\vert<4\ {\ {dB}}) for the differential mode with wideband common-mode suppression are designed and fabricated. The theoretical and measured results agree well with each other and show good in-band performances. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a design method of multi-way combining networks with impedance transformation for millimeter-wave (MMW) power amplifiers (PAs) to achieve high output power and wideband performance simultaneously in millimeter-wave frequency. Based on the proposed methodology, three power amplifiers are designed and fabricated in V-band, W-band, and D-band using 65-nm CMOS technology. With 1.2-V supply, the saturation powers of these power amplifiers are 23.2 dBm, 18 dBm and 13.2 dBm at 64 GHz, 90 GHz, and 140 GHz, with 25.1-GHz, 26-GHz, and 30-GHz 3-dB bandwidth, respectively. Compared with the published MMW amplifiers, these PAs achieve high output power and wide band performances simultaneously, and the ouput power levels is the state-of-the-art performance at these frequencies. [ABSTRACT FROM AUTHOR]

In this paper, the balanced-to-balanced Gysel power divider is proposed with bandpass filtering response for the first time. The component is based on a ring structure and designed with an extended coupled-resonator circuit model. The characteristic impedances, electrical lengths, and isolation resistance are calculated analytically by our derived equations, according to the design specifications of the filtering power divider. The achievable bandwidth is from about 3% to 12%. As an example, a fabricated prototype occupies an area of 0.97\,\times\,0.87 \lambdag^{2}, whose bandwidth is 8.4%. It has low differential-mode in-band insertion loss, good magnitude, and phase balances between two output ports, good isolation, and good suppression of common-mode noises and mode conventions. Based on stub-loaded sections, another prototype is realized for miniaturization, whose occupied area is reduced to 0.67\,\times\,0.63 \lambdag^{2}. In comparison with the original prototype, the central insertion loss is increased by 0.13 dB, and the rejection band of common-mode and mode-conversion noises is narrowed by 21%. [ABSTRACT FROM AUTHOR]

In this paper, a prototype automotive radar sensor is presented that is capable of generating simultaneously multiple transmit (TX) beams. The system is based on a four-channel 77-GHz frequency-modulated continuous-wave (FMCW) radar system. The number of beams, their radiated power, steering angle, and beam pattern can be changed adaptively. This is achieved by the utilization of orthogonal waveforms applied to different beams in combination with digital beamforming on the receive side. Key components are vector modulators in the TX path controlled by digital-to-analog converters. The performance of the system is shown in measurements focused on beam pattern, signal-to-noise ratio, and susceptibility in case of interfering targets at cross-range. Measurement results are discussed and compared to theory and simulations. Furthermore, crest factor minimization of the vector modulator's control signals is introduced and used to increase the achievable TX power, which will be also shown in measurements. [ABSTRACT FROM AUTHOR]

This paper proposes a novel concurrent dual-band receiver architecture that uses only one six-port correlator circuit to downconvert two signals in two different bands concurrently. The receiver is reconfigurable over a broadband to simultaneously receive two different signals with different modulation techniques and bandwidths. There are no limitations on the carrier frequencies of the two signals except that they have to be within the bandwidth of the six port receiver. The mathematical model for the receiver is derived and subsequently implemented to evaluate its performance. This approach shows that, by analytically choosing the frequencies of the two local oscillator signals sent into the six-port correlator, the in-phase (I) and the quadrature (Q) components of each of the two input RF signals can be obtained from the filtered high-pass and low-pass components of the diode detectors outputs. A black box model, which uses a modified memory polynomial, is used to calibrate the receiver. The calibration constants are estimated by sending a training signal of similar characteristics as the signal to be received. Two signals pairs with different modulation types are received to verify the model, and to evaluate the performance and test the robustness of the receiver. A 64-QAM signal at 2.5 GHz and a 16-QAM signal at 3.0 GHz, both with a data rate of 2 Mbps are received. The measured EVMs were 1.9% for the 64-QAM and 1.8% for the 16-QAM. Real communication signals, WCDMA and LTE were also received concurrently with measured EVMs of 1.9% and 2.0%, respectively. A bit error rate (BER) profile of the receiver for a 16QAM and 64QAM, both at 2Mbps is also plotted to evaluate the receiver. [ABSTRACT FROM AUTHOR]

This paper presents an X-band balanced Colpitts oscillator in GaN HEMT technology and a method to calculate its phase noise accurately. The method employs a low-frequency (LF) noise measurement and the oscillator waveforms from a harmonic-balance simulator. These data are post-calculated by Hajimiri's phase-noise model, in which the LF noise can be activated with a cyclo-stationary effect in the calculation of phase noise. Compared to commercial phase-noise simulation using predefined stationary noise, the calculation gives significantly improved phase-noise prediction in the 30-dB/decade region near carrier. The prediction is within 3-dB accuracy at 10-kHz, 100-kHz, and 1-MHz offset frequencies. In addition to the method used for phase-noise prediction, the potential for wideband tuning of this oscillator topology is analytically investigated. The measured phase noise of the oscillator is -\102 dBc/Hz at 100-kHz offset from a 8.6-GHz carrier frequency for drain voltage and current of Vd=15~\V and Id=40~\ mA. [ABSTRACT FROM PUBLISHER]

A method enabling the codesign of a high-efficiency power amplifier (PA) and a ring-resonator microstrip bandpass filter is proposed in this paper. Even–odd-mode analysis and a series of continuous modes (SCMs) are combined to realize broadband or multiband impedance matching as well as the suppression of undesired signals. The proposed codesign method can achieve both broadband and multiband frequency responses, and the designed component is relatively easy to analyze and fabricate due to its microstrip structure. For verification, a broadband and triband PA-filter components are designed and fabricated separately. The first component operates across 0.8–3.2 GHz (120%) with 39.7–42.9-dBm maximum output power and 57%–74% drain efficiency (DE). The second component, which has three passbands, covers several commercial frequencies with a measured output power of 39.6–41.3 dBm and DE from 62% to 68%. When these two components are driven by a 20-MHz long-term evolution signal with a peak-to-average power ratio of 6.2 dB, adjacent channel leakage ratios from −26.4 to −33.8 dBc and from −29.4 to −33.1 dBc are measured, respectively. [ABSTRACT FROM AUTHOR]

Two-stage reactively matched gain cells are proposed to implement a high-gain multioctave distributed power amplifier (DPA). The proposed reactively matched distributed amplifier (RMDA) structure shows high gain and power in a small die size. Detailed analysis is presented to understand the design criteria for interstage matching of reactively matched cells. A shared dc bias network is proposed to simplify the biasing of each section to reduce the DPA die size. The thermal coupling effect of GaN high-power amplifier is minimized by optimizing the chip layout. The theoretical analysis is verified by the simulation and supported by the measured data. Two RMDAs are fabricated with a commercial 0.25- $\mu \text{m}$ GaN HEMT process. The implemented RMDA with the compact transistor layout has been implemented in a small die size of 10.7 mm2 and shows output powers reaching 40.3–43.9 dBm, power added efficiencies (PAEs) of 16–27%, and small-signal gains of 15.3–23.2 dB. The RMDA with the reduced thermal coupling achieves 40.6–43.4 dBm with a peak PAE of 29% in a slightly larger die size of 13.8 mm2. To the best of our knowledge, this is the first demonstration of a GaN DPA using reactively matched gain cells, showing very high gain and efficiency over multioctave bandwidth in a small die size. [ABSTRACT FROM AUTHOR]

In this paper, an interferer-tolerant receiver for the first group of ultra-wideband (3.1–4.8 GHz) is presented. The entire system operates in two modes: detecting and receiving. In the detecting mode, the interferers pass through a low-noise amplifier (LNA), a multiplier, a phaser, which is a dispersive delay structure, and a decision circuit, while in the receiving mode, the signal passes through the LNA, three tunable notch filters, a mixer [consisting of a switch, a baseband (BB) transconductance stage, and a transimpedance amplifier], and a BB filter. The blocker detector detects the locations of blockers and reports them to the notch filters of the receiver for rejection. The entire system is integrated in a standard TSMC CMOS 65-nm technology and consumes up to 23.8 and 9.6 mW, in the receiving and detecting modes, respectively, with a 1-V voltage supply. The receiver achieves a simultaneous rejection of up to three out-of-band interferers and maximum out-of-band IIP3 and out-of-band IIP2 of 18.9 and 46 dBm, respectively, using a dynamic blocker detection and rejection technique. [ABSTRACT FROM PUBLISHER]

This paper presents a design strategy to enhance the bandwidth of three-stage Doherty power amplifier (DPA) with operation upto 12-dB back-off. Based on the proposed strategy, a broadband 48-W DPA is designed and implemented using packaged CREE GaN transistors. The measured drain efficiency of 50%–61.8% at 12-dB back-off and 51.9%–66.2% at 6-dB back-off is obtained over the frequency range of 600–900 MHz. Over this 300-MHz band, the drain efficiency is between 51.1% and 78% at saturation. This corresponds to 40% fractional bandwidth. The three-stage DPA is also linearized with a three carrier 15-MHz WCDMA signal with a PAPR of 10.6 dB at various frequencies within operating band and shows the output signal qualifies spectral mask specifications. [ABSTRACT FROM PUBLISHER]

This paper expounds a three-way Doherty power amplifier (3W-DPA) as a solution to the need for high-efficiency wideband power amplifiers when driven by multi-standard signals. The paper begins with a theoretical analysis of 3W-DPA architecture from which the governing equations are derived. This analysis enables the identification of circuit parameters for maximizing bandwidth. A comprehensive methodology was devised to address the practical design challenges resulting from the transistor nonidealities: nonlinear input capacitance, transistor package, and output capacitance. Based on this methodology, a fully analog 30-W 3W-DPA was designed and implemented using GaN packaged transistors. The 3W-DPA prototype maintained an average drain efficiency of 55% at an output back-off of up to 9 dB, over the frequency range of 0.73–0.98 GHz. The 3W-DPA was successfully linearized when driven with 20-MHz four-carrier wideband code division multiple access (WCMDA) signals. 830- and 900-MHz power-added efficiencies of 47% and 53% was achieved at 32- and 35-dBm average output power, corresponding to a peak-to-average power ratio of 11.7 and 7.14 dB, respectively. [ABSTRACT FROM PUBLISHER]

This paper presents a new class of dual-, tri- and quad-band BPF by using proposed open stub-loaded shorted stepped-impedance resonator (OSLSSIR). The OSLSSIR consists of a two-end-shorted three-section stepped-impedance resistor (SIR) with two identical open stubs loaded at its impedance junctions. Two 50-\Omega tapped lines are directly connected to two shorted sections of the SIR to serve as I/O ports. As the electrical lengths of two identical open stubs increase, many more transmission poles (TPs) and transmission zeros (TZs) can be shifted or excited within the interested frequency range. The TZs introduced by open stubs divide the TPs into multiple groups, which can be applied to design a multiple-band bandpass filter (BPF). In order to increase many more design freedoms for tuning filter performance, a high-impedance open stub and the narrow/broad side coupling are introduced as perturbations in all filters design, which can tune the even- and odd-mode TPs separately. In addition, two branches of I/O coupling and open stub-loaded shorted microstrip line are employed in tri- and quad-band BPF design. As examples, two dual-wideband BPFs, one tri-band BPF, and one quad-band BPF have been successfully developed. The fabricated four BPFs have merits of compact sizes, low insertion losses, and high band-to-band isolations. The measured results are in good agreement with the full-wave simulated results. [ABSTRACT FROM PUBLISHER]

This paper analyzes the influence of the Miller effect on the gain performance of the cascode stage. A passive compensation network is proposed to cancel Cbc at the millimeter-wave range without distinct penalty on noise figure and stability. Using this passive compensation network, the cascode stage can achieve a higher gain in a wider bandwidth than other cascode topologies. Furthermore, a W-band amplifier based on the new cascode stage is designed and fabricated using the 0.13-\mum BiCMOS process successfully. The proposed passive compensation network has a potential to be used in other building blocks, which need improvement through Miller effect cancellation. [ABSTRACT FROM PUBLISHER]

This paper proposes a multistage transformer-feedback-based design approach for a high fractional-bandwidth (fBW) IF stage in a 60-GHz heterodyne receiver. An in-depth analysis of source-to-gate transformer-feedback amplifiers, including the design of the matching network, is presented. Analytic expressions for the input resistance, quality factor, and noise figure (NF) as a function of the transformer turns-ratio (n) and magnetic coupling factor (k) are derived. To validate the proposed analysis, a wideband IF amplifier and mixer were designed in a 40-nm CMOS process. From measured results, this device achieves a 16% -3-dB fBW, a peak power gain of 27.6 dB, an NF of 5.3 dB while consuming 28.8 mW from a 0.9-V supply. [ABSTRACT FROM AUTHOR]

This paper presents a fully analytical model to determine the transmission and reflection properties of planar 1-D distributions of metal strips or slits made in thin metal screens. In contrast with other analytical or quasi-analytical approaches, the formulation incorporates the presence of dielectric slabs and is valid over a wide frequency band, from the long wavelength limit to the grating lobes operation. The model has been adapted to the case where two 1-D planar grids are stacked or a single grid is printed on a grounded substrate. In these cases, the model rigorously takes into account higher order mode interaction between the two stacked arrays of strips/slits or with the ground plane. Oblique incidence and both TE and TM polarizations have been considered. The analytical results show a good agreement with those computed by high-performance numerical methods, accounting for very fine details of extremely complicated transmission/reflection spectra. These results are of straightforward application to a variety of practical situations from microwaves to the terahertz regime. The present methodology can still be useful at higher frequencies provided that adequate models of the planar conductors are incorporated. In general, the model provides physical insight on the nature of the expected spectra and facilitates the design of devices based on planar metallic gratings. [ABSTRACT FROM AUTHOR]

The continuously increasing demand for wide bandwidth creates great difficulties in employing digital predistortion (DPD) for radio frequency (RF) power amplifiers (PAs) in future ultra-wideband systems because the existing DPD system requires multiple times the input signal bandwidth in the transmitter and receiver chain, which is sometimes almost impossible to implement in practice. In this paper, we present a novel band-limited digital predistortion technique in which a band-limiting function is inserted into the general Volterra operators in the DPD model to control the signal bandwidth under modeling, which logically transforms the general Volterra series-based model into a band-limited version. This new approach eliminates the system bandwidth constraints of the conventional DPD techniques, and it allows users to arbitrarily choose the bandwidth to be linearized in the PA output according to the system requirement without sacrificing performance, which makes the DPD system design much more flexible and feasible. In order to validate this idea, a high-power LDMOS Doherty PA excited by various wideband signals, including 100-MHz long-term evolution advanced signals, was tested. Experimental results showed that excellent linearization performance can be obtained by employing the proposed approach. Furthermore, this technique can be applied to other linear-in-parameter models. In future ultra-wideband systems, this new technique can significantly improve system performance and reduce DPD implementation cost. [ABSTRACT FROM AUTHOR]

This paper presents generalization and reduction of the line-series-shunt (LST) calibration technique, including generic parasitic treatments on the series/shunt standards and number reduction of calibration standards, for broadband GaAs and CMOS on-wafer scattering parameter (S-parameter) measurements. The series/shunt standards are modified with additional transmission-line (TL) sections on both the left and right sides to directly solve the five calibration parameters, namely, TL propagation constant, series impedance, shunt admittance, series parasitic admittance, and shunt parasitic impedance. This approach relaxes the constraint on the series/shunt standards that may not satisfy the plain lossy TL assumption in the parasitic evaluations. The calibration can be further reduced by only two standards if the lossy TL models for the series/shunt standards are satisfied. These points are examined by a microstrip test structure built on GaAs and CMOS technologies, with verification of an independent thru-reflect-line calibration. [ABSTRACT FROM AUTHOR]

Jitter limitations pose significant challenges for high-resolution and sampling-rate analog-to-digital converters (ADCs). This paper describes an integrate-and-sample (IAS) receiver suitable for use in an optical parametric photonic ADC. Rate-scalable photonic-sampling techniques provide low-jitter optical sampling and analog-to-digital conversion of the wideband signal up to 10 GHz and beyond. An 8-bit 2-GS/s IAS receive channel is described for a rate-scalable photonic ADC. Electronic measurements are shown for an RF tone and a photonic Gaussian pulse source and compared to simulations. A two-channel IAS array is fabricated in a 120-nm SiGe BiCMOS process and packaged onto a printed circuit board for integration into the photonic-sampling setup. A single 2-GS/s channel achieves a measured performance higher than 8.1 ENOB. The two-channel integrated circuit consumes 890 mA per channel from 5- and 2.5-V supplies and occupies an area of \ 1.6\times \ 2.0~\ mm^2. [ABSTRACT FROM AUTHOR]

An innovative vector-sum phase shifter with a full 360^\circ variable phase-shift range in 0.18-\mum CMOS technology is proposed and experimentally demonstrated in this paper. It employs an I/Q network with high I/Q accuracy over a wide bandwidth to generate two quadrature basis vector differential signals. The fabricated chip operates in the 2.3–4.8 GHz range. The root-mean-square gain error and phase error are less than 1.1 dB and 1.4^\circ over the measured frequency span, respectively. The total current consumption is 10.6 mA (phase shifter core: \sim2.6 mA) from a 1.8 V supply voltage and overall chip size is 0.87\times \ 0.75\ mm^2. To the best of the authors' knowledge, this circuit is the first demonstration of microwave CMOS phase shifter with very low phase error over a wide bandwidth employing the vector sum method for all monolithic microwave integrated circuit phase shifters with 360^\circ phase-control range to date. [ABSTRACT FROM PUBLISHER]

A new doubly balanced drain-pumped topology for CMOS passive mixer design is proposed in this paper. In the efforts to improve the conversion loss of passive balanced mixers, the CMOS drain-pumped topology is employed. In addition, the doubly balanced architecture with the advantages of good port-to-port isolations has been combined with the CMOS drain mixer design. For the broad bandwidth and the flatness of the conversion loss, a wideband matching technique using a broadband Marchand balun network is analyzed and successfully implemented in the mixer design. This mixer is fabricated in standard 90-nm CMOS technology. According to experiment results, the mixer has a measured conversion loss of \7.5\pm \1.5∼\ dB from 33 to 58 GHz. Based on the double-balanced architecture, the local oscillator (LO)-to-RF and LO-to-IF isolations are better than 42.7 and 51.5 dB, respectively. The mixer consumes zero dc power with a compact size of 0.55\,\times \,0.52 \ mm^2. To the best of our knowledge, this paper presents the first CMOS drain mixer using doubly balanced topology. [ABSTRACT FROM AUTHOR]

A novel wideband receiver RF front-end, including a resistive negative feedback wideband low-noise amplifier (LNA) with feedforward noise and distortion cancellation and a current commutating down conversion passive mixer with biquad trans-impedance amplifier, is presented in this paper. In comparison to conventional resistive negative feedback LNAs, theory analysis and experimental results for the proposed LNA circuit shows improved performance parameters, including voltage gain, noise figure (NF), and input-referred third-order intercept point (IIP3), especially helpful for wideband LNA design in modern deep-submicrometer CMOS. A wideband receiver RF front-end fabricated in 0.13-\mu\m CMOS, based on the proposed feedforward noise and distortion-cancellation resistive-feedback LNA, has 42–48-dB conversion gain with 0.8–12-MHz tunable IF -3-dB bandwidth and 12-dB adjacent channel selectivity at 2fp, -14-dBm IIP3, and 3-dB NF double-sideband with 10-kHz flicker-noise corner frequency. [ABSTRACT FROM AUTHOR]

A wideband low-noise amplifier (LNA), which is a key block in the design of broadband receivers for multiband wireless communication standards, is presented in this paper. The LNA is a fully differential common-gate structure. It uses multiple feedback paths, which add degrees of freedom in the choice of the LNA transconductance to reduce the noise figure (NF) and increase the amplification. The proposed LNA avoids the use of bulky inductors that leads to area and cost saving. A prototype is implemented in IBM 90-nm CMOS technology. It covers the frequency range of 100 MHz to 1.77 GHz. The core consumes 2.8 mW from a 2-V supply occupying an area of 0.03 \ mm^2. Measurements show a gain of 23 dB with a 3-dB bandwidth of 1.76 GHz. The minimum NF is 1.85 dB, while the average NF is 2 dB across the whole band. The LNA achieves a return loss greater than 10 dB across the entire band and a third-order input intercept point IIP3 of -2.85 dBm at the maximum gain frequency. [ABSTRACT FROM PUBLISHER]

This paper presents the first known synthesis method for the design of nonuniform transmission lines (NUTLs) for ultra-wideband (UWB) pulse shaping, which can account for, and partially compensate for, the loss and dispersion present in real transmission lines. Without this compensation, cumulatively increasing distortion occurs in UWB pulse trains generated using NUTLs. The synthesis method novelly combines techniques from both the microwave and digital design domains: first, the transfer function of the transmission line is modeled as a cascade of minimum-phase and all-pass networks in the Z-domain; next, this model is used in a modified layer-peeling algorithm that automatically partially corrects for line nonidealities. Two possible implementations are presented: one taking advantage of noncausal filtering and the other with filtering implemented in the frequency domain. The effectiveness of the method is confirmed with both simulations and measurements of an UWB pulse shaper, which generates the first known sequence of modified Hermite polynomial pulses with successful compensation for loss and dispersion in an NUTL up to 15 GHz. The presented example shows that the synthesis method reduced the error between NUTL models and measurements by an average of 55%. [ABSTRACT FROM AUTHOR]

A broadband Nolen matrix in substrate integrated waveguide (SIW) technology is proposed and studied in this paper. Being serial feeding networks, Nolen matrices usually introduce significant phase dispersion in their standard form, thus limiting effective bandwidth. In this work, broadband frequency operation is achieved with adequate coupler delay compensation, resulting in a more “parallel” matrix topology. Consequently, H-plane couplers with continuous aperture are preferred in the proposed design as opposed to the cross-couplers previously used in the “serial” configuration. The SIW couplers and phase shifters of a balanced amplitude 4\,\times\,4 Nolen matrix are designed at 77 GHz for radar applications. The resulting matrix that combines these elementary building blocks is fabricated and measured, and measured characteristics are in good agreement with theoretical and simulated predictions. This first design achieves excellent results over a 11.7% frequency bandwidth centered at 77 GHz. This modified Nolen matrix combines advantages of standard Nolen and Butler matrices and may be used as a building block for generalized orthogonal matrices. [ABSTRACT FROM PUBLISHER]

This paper presents a new design of wide slot antenna for various wideband applications. The proposed printed antenna consists of a slot and a turning stub, both formed by a binomial curve function; thus, various bandwidths (BWs) can be obtained based on the structure with different binomial curves. Some key parameters affecting the antenna performance have been analyzed and discussed in detail as an antenna design guideline. To validate the theoretical design, six prototypes of various binomial-curved slot antennas were designed, fabricated, and measured. Good agreement between the simulated results and the measured ones is observed. The results demonstrate that the proposed type of antenna can obtain a BW range from 9.8% to 99.7% for VSWR \leq 2 by selecting various binomial-curved slots, which may provide a convenience for various wideband antenna designs. Moreover, the proposed type of antenna owns a simple structure and a stable gain of about 3–5.5 dBi, which is very suitable for wideband wireless system applications. [ABSTRACT FROM AUTHOR]

In this paper, a horizontally meandered strip (HMS) feed technique is proposed to achieve good impedance matching and symmetrical broadside radiation patterns for a single-fed broadband circularly polarized stacked patch antenna, which is suitable for universal ultrahigh frequency (UHF) RF identification (RFID) applications. The antenna is composed of two corner truncated patches and an HMS, all of which are printed on the upper side of the FR4 substrates. One end of the HMS is connected to the main patch by a probe, while the other end is connected to an SMA connector. Simulation results are compared with the measurements, and a good agreement is obtained. The measurements show that the antenna has an impedance bandwidth (VSWR<1.5) of about 25.8% (758–983 MHz), a 3-dB axial ratio (AR) bandwidth of about 13.5% (838–959 MHz), and a gain level of about 8.6 dBic or larger within the 3-dB AR bandwidth. Therefore, the proposed antenna can be a good candidate for universal UHF RFID readers operating at the UHF band of 840–955 MHz. In addition, a parametric study and a design guideline of the proposed antenna are presented to provide the engineers with information for designing, modifying, and optimizing such an antenna. At last, the proposed antenna is validated in RFID system applications. [ABSTRACT FROM AUTHOR]

In this paper, a new behavioral model for bandpass sampling receivers (BPSRs) is presented. The new model describes the wideband behavior of the BPSR and addresses specifically its nonlinear behavior, either in-band distortion, but also intermodulation and harmonic generation. [ABSTRACT FROM AUTHOR]

In this paper, a novel two hidden layers artificial neural network (2HLANN) model is proposed to predict the dynamic nonlinear behavior of wideband RF power amplifiers (PAs). Starting with a generic low-pass equivalent circuit of the PA, several circuit transformations are applied in order to build an appropriate artificial neural network structure and improve the modeling accuracy. This approach culminates in the development of a real-valued and feed-forward 2HLANN-based model. The parameters (number of neurons, memory depth, etc.) of the proposed model and the back propagation learning algorithm (learning rate, momentum term, etc.) used for its training were carefully studied and thoughtfully chosen to ensure the generality of the constructed model. The validation of the proposed models in mimicking the behavior of a 250-W Doherty amplifier driven with a 20-MHz bandwidth signal is carried out in terms of its accuracy in predicting its output spectrum, dynamic AM/AM and AM/PM characteristics, and in minimizing the normalized mean square error. In addition, the linearization of the Doherty PA using the 2HLANN enabled attaining an output power of up to 46.5 dBm and an average efficiency of up to 40% coupled with an adjacent channel power ratio higher than 50 dBc. [ABSTRACT FROM AUTHOR]

This paper investigates the virtues of the asymmetrical Doherty power amplifier (PA) for improving the average power efficiency, linearity, and peak envelope power. It commences with an in-depth study of the effects of increasing the size of the peaking amplifier's transistor and its conduction angle on the Doherty PA's RF performance. In particular, the impact of the extended current profile of the peaking amplifier and reduced turn-on effects on the soft-turn characteristic are thoroughly analyzed, and their impacts on the average efficiency and peak power are deduced. Furthermore, the aggravation of the memory effects that accompany the gm3-based nonlinear distortion cancellation is experimentally demonstrated. Two asymmetrical Doherty PAs prototypes are fabricated using 80 W and 150 W laterally diffused metal oxide semiconductor field-effect transistors to individually improve average efficiency and linearity. When driven with a four carrier wideband code division multiple access (4C-WCDMA) signal, the asymmetrical Doherty PA allowed for excellent drain efficiency of approximately 50%, along with high linearity of approximately - \ 50~\ dBc, using a memory polynomial digital predistorter at an average output power of 50 W. To the best of the authors' knowledge, this achieved efficiency is the highest reported in the literature for a high-power Doherty PA implemented in LDMOS technology. [ABSTRACT FROM AUTHOR]

In this paper, differential low-noise amplifiers are presented as a very powerful solution for radio astronomy applications. A fully differential amplifier topology has been analyzed and implemented in microstrip technology with discrete surface mount components. The amplifier design is made for an active receiving dense antenna array. Thus, the differential amplifier source impedance is no longer 50 \Omega, but 150 \Omega from the proposed bunny-ear antennas. A full characterization in terms of gain and noise has been undertaken. Source–pull measurements have been included in order to evaluate the performance of the amplifiers operating with variable source impedances. Noise temperatures below 55 K have been obtained for the differential design in the 300–1000-MHz band for the 150-\Omega impedance. In addition, the results for different scanning angles are also presented. [ABSTRACT FROM AUTHOR]

This paper presents a dimensional synthesis method for the design of symmetric wideband waveguide cross-coupled filters without resorting to global full-wave optimization. In this method, we propose two circuit models suitable for the synthesis of wideband cross-coupled filters. Besides, we propose a novel physical realization of the cross-coupled K-inverter in the waveguide filter. As a design example, an X-band four-pole waveguide cross-coupled filter has been designed and fabricated. The results show good equal-ripple performance in the passband and improved rejection performance beyond the passband. [ABSTRACT FROM AUTHOR]

Given the trend towards a user-centric concept in mobile communications, body area networks have received increasing attention within the wireless personal and body area networks community. In this paper, an experimental investigation is presented to derive suitable radio propagation models for ultra wideband (UWB) body-centric wireless communications. The performance of the body-centric UWB radio channel is investigated by considering several on-body links, including different body postures. System-level modeling of potential multiband orthogonal frequency-division multiplexed UWB system has been conducted and system performance is measured using bit error rate (BER) and signal-to-noise ratio. The conducted system analysis demonstrated that for 78% in the static case and 75% and 61% for stable and unstable transmitter locations in the pseudodynamic in-motion scenarios (respectively) of the specified on-body radio links, the BER is equal to or less than 0.1%. This demonstrates promising applications of the proposed UWB body-centric radio system. Based on these results, clear recommendations are given for best on-body locations leading to optimal system performance. [ABSTRACT FROM AUTHOR]

This paper demonstrates two broadband air-filled micro-coaxial 4:1 (2–24 GHz) and 2.25:1 (2–22 GHz) impedance transformers. The 4:1 transformer converts 50 to 12.5 \Omega and the 2.25:1 device transforms 50 to 22.22 \Omega. The circuits are fabricated on silicon with PolyStrata technology, and are implemented with \650\ \mu\ m\times \400\ \mu\ m air-filled micro-coaxial lines. Back-to-back circuits and single structures with geometrical tapers are designed for systematic characterization. Simulation and measurement results are in excellent agreement. The return loss for both transformers is better than 15 dB over the design bandwidth. [ABSTRACT FROM PUBLISHER]

A dual-band switchable harmonic receiver for downconverting the industrial-scientific-medical and local-multipoint-distribution-service bands at 24 and 31 GHz is proposed in this paper. The front end utilizes a new technique for band selection. Mathematical formulation, including the effect of mismatches, for the new switchable harmonic receiver is provided in this paper. In addition, new circuit techniques for the low-noise amplifier and millimeter-wave mixer implementations are presented. The receiver is implemented using 0.18-\mum BiCMOS technology with a total power consumption of 60 mW. Measurements show a band rejection higher than 43 dB, gain of 21 and 18 dB, NF lower than 8 and 9.5 dB, and third-order intercept point of -18 and -17 dBm for the 24- and 31-GHz frequency bands, respectively. [ABSTRACT FROM PUBLISHER]

This paper first describes the phenomenon of Gaussian pulse spread due to numerical dispersion in the finite-difference time-domain (FDTD) method for electromagnetic computation. This effect is undesired, as it reduces the precision with which multipath pulses can be resolved in the time domain. The quantification of the pulse spread is thus useful to evaluate the accuracy of pulsed FDTD simulations. Then, using a linear approximation to the numerical phase delay, a formula to predict the pulse duration is developed. Later, this formula is used to design a Gaussian source that keeps the spread of numerical pulses bounded in wideband FDTD. Finally, the developed model and the approximation are validated via simulations. [ABSTRACT FROM PUBLISHER]

In this paper, a new synthesis and design methodology is presented and applied for the fast and accurate design of inductive rectangular waveguide filters. By using this technique, the dimensions of both homogeneous and inhomogeneous filters can be successfully synthesized for almost any practical filter bandwidth, return loss, or filter order. This novel technique is based on a prototype with additional degrees of freedom, able to match the response of the different filter components in a wideband frequency range, and an elaborated design procedure that fully exploits this flexibility. During the design procedure, the prototype and the real structure are continuously aligned in order to have the same electromagnetic behavior and jointly evolve to obtain an equiripple response. Once the final prototype has been synthesized, excellent filter dimensions can be extracted that, in most cases, do not require further optimization. Examples will show the outstanding performance of the proposed design technique in terms of versatility, accuracy, and CPU time. [ABSTRACT FROM AUTHOR]

In this paper, the design, implementation, and experimental results of a high-efficiency wideband GaN-HEMT power amplifier are presented. A method based on source-pull/load-pull simulation has been used to find optimum source and load impedances across the bandwidth and then used with a systematic approach to design wideband matching networks. Large-signal measurement results show that, across 1.9-4.3 GHz, 9-11-dB power gain and 57%-72% drain efficiency are obtained while the corresponding power-added efficiency (PAE) is 50%-62%. Moreover, an output power higher than 10 W is maintained over the band. Linearized modulated measurements using a 20-MHz long-term evolution signal with 11.2-dB peak-to-average ratio show an average PAE of 27% and 25%, an adjacent channel leakage ratio of -44 and -42 dBc at 2.5 and 3.5 GHz, respectively. [ABSTRACT FROM AUTHOR]

The circuit-oriented finite-element method (FEM) is a method that combines a finite-element field solver with a circuit analyzer and is suitable for analyzing electromagnetic field/circuit coupled problems. This paper describes a significant improvement to existing circuit-oriented FEMs that reduces the number of circuit elements and eliminates low-frequency stability problems. A modified LU recombination method is used to reformulate the original field-solver matrix equations. Circuits based on the reformulated equations are relatively insensitive to numerical errors and do not contain the small-value series resistors that circuit solvers are normally forced to add in order to guarantee a stable solution. Using this approach, the circuit-oriented FEM is capable of time- and/or frequency-domain simulations of problems containing linear or nonlinear lumped elements over a wide bandwidth. Examples are provided that demonstrate the ability of the new technique to model geometries from dc to several gigahertz in a single simulation. [ABSTRACT FROM AUTHOR]

In this paper, a new uniplanar 180° phase switch suitable for space differential radiometers is proposed. It is based on two dc-contact-microelectromechanical system (MEMS) single-pole-double-throw switches that switch between two different back-to-back coplanar-to-slotline transitions. Since these transitions are multimodal structures, rigorous multimodal models are developed to analyze them and to assess the effects of the unwanted coplanar odd mode. These models are capable of predicting under what conditions the transitions produce a good wideband, 180°-phase-shift and/or matching behavior; they are applied to the design of the 180° phase switch. A compact implementation of the phase switch in the frequency range 14-20 GHz is fabricated using the FBK-irst eight-mask surface micro-machining process, featuring a 180° phase-shift bandwidth of 35% for a maximum phase error of 5° and insertion loss better than 2 dB. Experimental results show a very good agreement with the multimodal model predictions. The designed dc-contact MEMS switches fulfill the typical requirements of differential radiometers, featuring measured mechanical switching and release times of 100 and 15 µs, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a new class of wideband 90° hybrid coupler with an arbitrary coupling level. The physical size of the proposed coupler is close to that of a conventional two-section branch-line coupler, but it has an additional phase inverter. The impedance bandwidth of the proposed coupler is close to that of a four-section branch-line coupler. The proposed coupler is a backward-wave coupler with a port assignment different from that of a conventional branch-line coupler. The design formulas of the proposed coupler are proved based on its even- and odd-mode half structures. We demonstrated three couplers at the center frequency of 2 GHz with different design parameters. [ABSTRACT FROM AUTHOR]

This paper describes a novel fully calibrated four channel broadband time-domain measurement system for the characterization of nonlinear microwave devices with memory. The hardware architecture of the proposed time-domain measurement system is based on a wideband sub-sampling principle. The sampling heads work at a high strobe signal repetition frequency that can be tuned between 357-536 MHz. We achieve a 40-GHz RF frequency bandwidth and a 160-MHz IF bandwidth. This instrument enables the measurement of carrier and envelope waveforms at both ports of nonlinear microwave devices driven by broadband modulated multicarriers. The test-bench is applied to the cross modulation characterization of a 15-W GaN HEMT CREE S-band power amplifier with memory due to different biasing circuit configurations. The amplifier under test is driven by the sum of a large-signal modulated carrier (double-sideband amplitude modulation at 3.6 GHz) and a small single-tone signal at a 110-MHz offset frequency. Our significant contribution comes from the capability of the measurement system to record the time-domain waveforms of several nonadjacent modulated signals on a similar time equivalent scale for different cases of memory effects of the power amplifier under test. [ABSTRACT FROM AUTHOR]

This paper presents a preliminary investigation of orthogonal frequency coding (OFC) surface acoustic wave tags and sensors at a 500- and 900-MHz operational frequency range using conventional contact lithography techniques. The higher frequency devices are achieved using second harmonic operation; eliminating the need for advanced lithography techniques. The objective of this effort is to increase the technology readiness level of wideband OFC tags at higher frequencies. Measured device results are presented and compared with coupling of modes model predictions to demonstrate performance. The fundamental and harmonic device response is compared for devices designed for operation in the 900-MHz frequency band. The experimental correlation against an ideal matched filter is also presented. [ABSTRACT FROM AUTHOR]

In this paper, we present the development of an even-mode matching network for a Marchand balun to achieve 50-Ωmatch and high isolation at the balanced ports. A very wide matching bandwidth can be accomplished with the novel addition of an open-circuit stub to the network. Experimental results demonstrate that the even-mode matched balun achieves return losses that are greater than 15 dB at the balanced ports from 6 to 17 GHz. The measured isolation between the balanced ports is greater than 15 dB from 4 to 19 GHz. For the unbalanced port, the return loss is greater than 15 dB from 4 to 19 GHz. The measured insertion loss is less than 1 dB, and amplitude and phase imbalances are ±0.5 dB and ±5° from 4 to 18 GHz, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a design technique to match lumped resistors in the dc to 20-GHz band is presented. This technique makes it possible to implement very wideband matched loads with a return loss that is better than 20 dB. The proposed implementation is simple, low cost, and gives superior performance than previously reported alternatives. The technique was developed to match surface-mount resistors soldered on plastic substrates, and was then successfully applied to match trimmed printed resistors on low-temperature co-fired ceramic substrates. [ABSTRACT FROM AUTHOR]

Uniplanar 1800 hybrids are basic building blocks in uniplanar technology. In this paper, a new rigorous analysis of a uniplanar 180° magic-T hybrid based on an air-bridged coplanar cross is performed. The analysis proposed is multimodal since it takes into account the coplanar even and odd fundamental modes simultaneously. From this analysis, a complete circuit model for the hybrid is extracted, and the conditions for ideal performance are derived. This new multimodal model is necessary for the design of the hybrid, and allows a quantitative analysis of its performance, notably bandwidth, isolation, and return loss under any actual loading condition. It has been used to design and implement a 180° hybrid on alumina with a working frequency of 15 GHz. A very good agreement between simulation and measurement is obtained. The experimental results prove a frequency-independent phase-shift behavior with a measured phase error less than ±2°. [ABSTRACT FROM AUTHOR]