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Mobile and wireless communications are playing an irreplaceable role in our daily life. 5G is highly expected and can be considered as the convergence of mobile and wireless communications. This topic becomes one of the hottest research topics recently, and papers on this topic have been paid much attention. lists the top ten papers published in the IEEE Transactions on Microwave Theory and Techniques (TMTT) in 2019 with the highest numbers of Full Text View since published. Seven papers are about millimeter-waves (mm-waves), and because mm-waves multiple-input–multiple-output (MIMO) will be adopted globally, the 24.25–27.5-GHz band and 27–29.5-GHz bands are now approved worldwide as the standard 5G communication bands. The most popular paper is published by Asbeck et al. [item 1) in the Appendix] for mm-wave power amplifiers. [ABSTRACT FROM AUTHOR]

In this paper, the feasibility of inkjet printing of circuit and microwave structures on paper-based substrates is investigated for the first time in the implementation of a complete low-cost wireless platform for sensors. First, the system-level design of the module including the amplifier characterization were carried out to ensure optimum performance of the sensor modules in the UHF bands used in RF identification communication. These results were then used to design two different antenna structures, which are printed on paper along with their respective circuit layouts using inket-printing technology. Different techniques were investigated for the assembly of circuit components on the silver printed layouts. Finally, wireless link measurements on the assembled prototypes verified the good performance on the wireless and sensing sides. [ABSTRACT FROM AUTHOR]

This paper demonstrates the design of an 800-MHz solar-powered active wireless beacon composed of an antenna and an integrated oscillator on a low-cost paper substrate. Inkjet printing is used to fabricate the conductive circuit traces and the folded slot antenna, while the oscillator circuit is designed using off-the-shelf components mounted on the paper substrate. Flexible, low-cost, amorphous silicon (a-Si) solar cells are placed on top of the slot ground and provide autonomous operation of the active circuit eliminating the use of a battery. A prototype is built and characterized in terms of phase noise, radiation patterns, and the effect of solar irradiance. Such low-cost flexible circuits can find significant applications as beacon generator circuits for real-time identification and position purposes, wearable biomonitoring as well as solar-to-wireless power transfer topologies. The measured phase noise is -\116 dBc/\Hz at 1-MHz offset, while drain current is 4 mA and supply voltage is 1.8 V. [ABSTRACT FROM AUTHOR]

This Transactions’ Mini-Special Issue includes four papers from the 2018 IEEE Radio and Wireless Week (RWW 2018) held in Anaheim (Garden Grove), CA, USA, January 14–17, 2018. RWW consists of five conferences focusing on the wireless communication theory, systems, circuits, and device technologies. They include the Radio and Wireless Symposium, Topical Conference on Power Amplifiers for Wireless and Radio Applications, Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, Topical Conference on Wireless Sensors and Sensor Networks, and Topical Workshop on The Internet of Space. The program included parallel track technical sessions, three workshops, an Internet of Things (IoT) summit, a plenary session on IoT within 4G/5G networks, a panel session on the role of the device in power amplifier design, a joint RWW student paper contest, and a demo track session. A total of 243 papers were submitted to the RWW 2018 Technical Program Committee and 177 papers were accepted for presentation at the meeting and publication on the IEEE Xplore website. [ABSTRACT FROM AUTHOR]

In this paper, an extensive review of the most up-to-date papers on microwave Doherty power amplifiers is presented. The main applications are discussed, together with the employed semiconductor technologies. The different research trends, all aimed to improve the advantages of the Doherty scheme and to solve its inherent drawbacks, are presented. The first considered topic is the maximization of efficiency and/or linearity, where analog and digital techniques are exploited. Another important trend is the bandwidth enlargement of the Doherty architecture, that involves a large number of papers. Multi-band, multi-mode solutions are also considered, using either fixed or reconfigurable solutions. The final section is dedicated to the most significant Doherty integrated implementations. [ABSTRACT FROM AUTHOR]

This Transactions on Microwave Theory and Techniques’ Mini-Special Issue includes ten papers from the 2017 IEEE Radio and Wireless Week (RWW 2017) held in Phoenix, AZ, USA, January 15–18, 2017. The Radio and Wireless Week consists of five related conferences that focus on the intersection between wireless communication theory, systems, circuits, and device technologies: the Radio and Wireless Symposium, the Topical Conference on Power Amplifiers for Wireless and Radio Applications, the Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, the Topical Conference on Wireless Sensors and Sensor Networks, and the Topical Workshop on The Internet of Space. Radio and Wireless Week is thus a multidisciplinary event bringing together innovations that are happening across the broad wireless spectrum. A total of 214 papers were submitted to the RWW 2017 Technical Program Committee, of which 168 papers were accepted for presentation and publication online on the IEEE Xplore website. Together with the technical sessions, four workshops, one special talk on the Internet of Things powered by wireless, a plenary session on 5G hardware and system solutions, a panel session on linearization of power amplifiers for 5G, and a demo track session to show the latest innovative wireless experimental achievements were successfully held. [ABSTRACT FROM PUBLISHER]

This paper presents an automatic impedance transforming technique to extend the radio frequency rectifier input power range with high conversion efficiency. The rectifier employs two branches of subrectifier, each achieving impedance matching at high and low input power ranges. Then, the two branches are connected by a $\lambda/4 $ T-junction power divider. With such configuration, the input impedance of the two subrectifiers are transformed automatically, allowing the impedance matching over a wide input power range. In this way, the injected power can be optimally delivered to the subrectifiers, achieving a high efficiency over this wide input power range. This scheme manages to eliminate the power detetor for branch selection and can be applied to both single- and dual-band rectifiers with a reduced design difficulty. For validation, a single-band rectifier working at 915 MHz and a dual-band rectifier at 915/2450 MHz are implemented. Design analysis on the single- and dual-band rectifiers is carried out. The measurement results show that 68% maximum efficiency is achieved for the single-band (915 MHz) rectifier, and the input power range for the efficiency >70% of the peak efficiency is from −5 to 31 dBm. Besides, the dual-band rectifier shows 66% and 58% peak efficiencies at 915 and 2450 MHz, respectively. The input power range is from −6 to 33 dBm for the efficiency >70% of its peak value at 915 MHz, while from 10 to 32 dBm at 2450 MHz. These indicate that the input power range with high efficiency is extended. [ABSTRACT FROM AUTHOR]

Due to technological advances in various fields and the rising demand for automation, the popularity of service robots is expected to grow rapidly in the upcoming years. One of the core functions of such robots is their interaction with people. One type of interaction, which is studied in this paper, is when the robot leads or follows a person. This presupposes that the position of the person is known relative to the mobile robot. In this paper, we present a 24-GHz wireless locating system to enable this kind of human–robot interaction. The system consists of a radar node attached to the robot and an active portable wireless beacon that is carried by the person. Using a secondary radar approach to measure the distance and angle to the beacon, the 2-D position of the person relative to the mobile robot can be accurately determined by a single radar node on the robot. This is unfeasible with standard multilateration localization approaches. An extended Kalman filter is used to increase the accuracy and reliability of the positioning system. The measurements presented in this paper, performed in a scenario that is both challenging and realistic, demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

With the great explosion of wireless systems and their applications and also with the limited enabling energy and spectrum resources available, it becomes more and more crucial to focus on the reduction of energy use in future wireless systems. The most efficient way of electromagnetic wave energy reception is to fully capture the two orthogonal components of its field vector in connection with polarization diversity. This paper shows how to exploit the concept of polarization diversity over the millimeter-wave (mmW) frequency band which has been assigned for wireless applications. This is done by developing the theory of operation and design procedure of dually-polarized mmW components. The novelty presented in this paper lies in developing a principle of operation so to come up with a class of dually-polarized mmW components, namely, 3-dB couplers, 0-dB couplers, and phase shifters. This allows the development of dually-polarized beamforming networks such as Butler matrix. A full analytical design procedure is presented with verification through full-wave simulations and prototype measurements. [ABSTRACT FROM AUTHOR]

This paper introduces new techniques for ultra-wideband (UWB) joint spatial coding in order to establish a secure line-of-sight wireless communication link, performing precision localization of point objects, and generating high-resolution images from complex scenes. For the proposed technique, symbol generation and coding are jointly performed by multiple widely spaced transmitters. This method enables the transmission of directionally modulated signals that can only be decoded at a desired angle, resulting in a secure communication link. It is also shown that joint spatial coding by multiple transmitters that are synchronized with each other enables the precise localization of multiple point objects and allows high-resolution 3-D imaging of distributed objects. The technique is demonstrated experimentally in the frequency range 3–10 GHz by generating and detecting UWB pulses. [ABSTRACT FROM PUBLISHER]

This Transactions’ Mini-Special Issue includes seven expanded papers from the fourth IEEE Wireless Power Transfer Conference (WPTC), held in Aveiro, Portugal, on May 5–6, 2016. [ABSTRACT FROM PUBLISHER]

Integrated antennas have become the attractive solution as the electromagnetic (EM) interface for mm-Wave and terahertz ICs. However, on-chip antennas lying at the interface between two different dielectrics (such as air and substrate) can channel most of its power into multiple nonradiative surface-wave modes, reducing efficiency drastically. In this paper, we consider the following problem: given a dielectric substrate, what is the theoretical optimal 2-D surface-current configuration that collectively suppresses surface waves and maximizes radiation efficiency with the desirable radiation pattern? This paper also discusses demonstrative examples of a circuit-EM codesign approach to realize the approximation of such current configurations. Measurement results of radiating arrays in CMOS at mm-Wave frequencies (250–300 GHz) are presented and compared with theoretical predictions. [ABSTRACT FROM PUBLISHER]

Nowadays, the explosive growth of Internet-of-Things-related applications has required the design of low-cost and low-power wireless sensors. Although backscatter radio communication is a mature technology used in radio frequency (RF) identification applications, ambient backscattering is a novel approach taking advantage of ambient signals to simplify wireless system topologies to just a sensor node and a receiver (RX) circuit eliminating the need for a dedicated carrier source. This paper introduces a novel wireless tag and RX system that utilizes broadcast frequency modulated (FM) signals for backscatter communication. The proposed proof-of-concept tag comprises of an ultralow-power microcontroller (MCU) and a RF front-end for wireless communication. The MCU can accumulate data from multiple sensors through an analog-to-digital converter, while it transmits the information back to the RX through the front-end by means of backscattering. The front-end uses ON–OFF keying modulation and FM0 encoding on ambient FM station signals. The RX consists of a commercial low-cost software-defined radio which downconverts the received signal to baseband and decodes it using a suitable signal processing algorithm. A theoretical analysis of the error rate performance of the system is provided and compared to bit-error-rate measurements on a fixed transmitter-tag-RX laboratory setup with good agreement. The prototype tag was also tested in a real-time indoor laboratory deployment. Operation over a 5-m tag-reader distance was demonstrated by backscattering information at 2.5 kb/s featuring an energy per packet of 36.9~\mu \textJ . [ABSTRACT FROM PUBLISHER]

This paper presents a technique capable to ameliorating the impairment caused by radio channel multipath, in the estimation of the wireless communications direction of arrival (DoA). This feature is enabled by a space division multiple access approach supported by a DoA technique based on the combination of the estimates achieved at both 2.45 and 5.2 GHz. The DoA estimation relies on a comparison between the real-time received signal strength indicator and the predicted signal level distribution, which can be estimated and stored without the need of lengthy offline measurement. The experimental setup adopted for the technique validation involves an active interferer, by which arbitrary multipath levels can be implemented. An equivalent reflection coefficient signal-to-interference ratio is defined as the ratio of the unperturbed signal and the induced coherent isofrequency interferer signal, compatible with the two-ray model of the multipath impairment. The proposed technique exploits a dual-band frequency planning, and because of the combined use of the data at the two frequencies, a mean error of 2.6° is observed within a domain ranging from 0.5 to 4 m, for the entire 360° angle in the reference anechoic scenario. The 90th percentile of the cumulative error distribution is 5.4°. In the presence of a strong coherent interferer, compatible with a total reflection from the walls, the mean error is 4.9°, while the 90th percentile of the cumulative error distribution is 10.5°. In the presence of the strongest coherent interferer signal available, which is more severe than the worst case of total reflection, the mean error is 7.1°, while the 90th percentile of the cumulative error distribution is 15.1°. [ABSTRACT FROM PUBLISHER]

Wireless communications from an airborne device to an underwater receiver is challenging because the conductivity of water severely dampens the magnitude of electromagnetic waves in the spectrum commonly used for wireless applications. In this paper, microwave-induced thermoacoustic communications (TAC), a hybrid technique for wireless communications, is investigated and experimentally demonstrated to provide a potential solution to this deficiency. TAC is based on the thermoacoustic effect and directly converts electromagnetic energy in air into acoustic energy in water. Experimental demonstration of TAC is reported by successful wireless information transmission from a microwave antenna in air to an acoustic transducer in water. Bench-top TAC experiments are combined with an analytical model to study the influences of pivotal design parameters on the performance of TAC. The experiments and theoretical analysis suggest that TAC might lead to a new paradigm of air-to-underwater wireless communications. [ABSTRACT FROM AUTHOR]

In this paper, an extremely low-power and low-complexity CMOS sourceless millimeter-wave (mmW) receiver for the next-generation wireless communication and sensing systems including fifth-generation (5G) is proposed and demonstrated. It makes the use of injection-locked self-oscillating mixers (SOMs) in order to enable a direct conversion to baseband without resorting to any external local oscillator (LO) nor an IF processing block, therefore, greatly reducing power consumption, as well as the receiver’s complexity. This architecture is created through multi-input and multi-output (MIMO) arrays in connection with slicing frequency spectrum or frequency band of interest. In this way, the proposed receiver supports a high data transmission throughput based on the frequency-diversified MIMO, which presents a unique feature in the architectural implementation of a low-power and high bit-rate communication and sensing systems. Transmission and demodulation of a digital modulated signal M-quadratic-amplitude modulation (M-QAM) at 40 GHz, is successfully demonstrated with simulated and measured results. [ABSTRACT FROM AUTHOR]

In-band full-duplex (IBFD) wireless systems offer the ability to revolutionize frequency spectrum utilization for future networks. This is only possible if the self-interference generated by each wireless node is sufficiently mitigated, and becomes more challenging as the bandwidth increases. RF cancellation is one of the critical components that enables this interference reduction, but has previously been limited to narrowband operation or restricted to distinctive environments. This paper presents a novel RF canceller that utilizes photonic components to create a wideband vector modulator architecture with tunable time-delay taps. A prototype system with 20 canceller taps has been demonstrated to provide 25 and 20 dB of cancellation over 500-MHz and 1-GHz instantaneous bandwidths, respectively, and is tunable between 0.5 and 5.5 GHz. This unique photonic-enabled RF canceller design provides a path forward to achieve the wideband operation and high tap counts that will be required to successfully deploy future wireless systems with IBFD technology. [ABSTRACT FROM AUTHOR]

This paper proposes a novel concept of an integrated duplex antenna for realizing a compact multifunction RF front end by integrating a duplexer and a dual-band patch antenna. First, an all-resonator-based duplexer is designed. It is composed of two sets of split-ring resonators as channel filters, which are joined by a dual-mode stub-loaded resonator as the junction resonator. Then, a novel dual-band patch antenna is achieved by coupling a patch with a hairpin resonator through a slot in the ground. Uniform radiation characteristics have been achieved across the two bands. Finally, the duplexer is integrated with the dual-band patch antenna to form a highly integrated duplex antenna by coupling the hairpin resonator to the junction resonator of the duplexer directly. In this process, the 50- $\Omega $ interface and matching network between them are removed, contributing to a compact footprint. The details of codesign approach have been discussed in this paper. Compared with the traditional cascaded duplexer and antennas, this paper is much more compact and integrated but with an improved frequency response. A prototype of an integrated duplex antenna at S-band is fabricated and measured, showing two operation channels of 2.52–2.65 GHz for transmitting and 2.82–2.94 GHz for receiving with an isolation of over 32 dB. The measured results agree well with the simulation results. [ABSTRACT FROM PUBLISHER]

In this paper, a novel filtering 180° hybrid coupler is proposed and used to design a $2 \times 4$ filtering Butler matrix. The filtering 180° hybrid coupler can provide power division and phase shift together with a second-order bandpass transfer function, and is based only on coupled resonators. The $2 \times 4$ filtering Butler matrix is easily realized by utilizing several hybrid couplers. The analytical synthesis procedures for the hybrid coupler and Butler matrix are presented in this paper. Finally, broadside and end-fire arrays are realized by using the Butler matrix. To illustrate the concept experimentally, a filtering 180° microstrip hybrid coupler and a $2 \times 4$ filtering microstrip Butler matrix are designed, fabricated, and measured. Simulation and measured results are found to be in good agreement with each other. [ABSTRACT FROM AUTHOR]

This paper describes the design and implementation of a W-band phased-array system with printed circuit board (PCB) integrated antennas in two polarizations capable of multi-gigabit spectrally efficient wireless communication. The chipset is manufactured in a 0.18- $\mu \text{m}$ SiGe BiCMOS technology with $f_{T}/f_{\mathrm {MAX}}$ of 240-/270-GHz and is flip-chipped onto a low-cost organic PCB with integrated antenna arrays. Each chip is equipped with 16-transmit/4-receive or 16-receive/4-transmit calibrated phase shifter elements and direct up- and downconverters plus a half-rate phase-locked loop. The different system tradeoffs required to establish a multi-Gb/s wireless link at millimeter waves are carefully studied. Built-in element failure detectors, power detectors, and digital interface enable factory calibration and self-test capability. Each transceiver chip operates from 1.5- and 2.5-V supplies and consumes 5.5 and 4.5 W in transmit and receive mode, respectively. The peak transmitter effective isotropic radiation power is 34 dBm in each polarization with a measured receiver noise figure of 6.5 dB at 94 GHz. At a distance of 1 m, a maximum wireless data rate of 30 Gb/s (per polarization) using 64-QAM can be achieved and at 20 m, 8 Gb/s (dual polarization) can be established using QPSK modulation. [ABSTRACT FROM AUTHOR]

In this paper, a general design method for multiband filters is proposed. First, the frequency and element transformations from a low-pass prototype filter to a practical multiband bandpass filter is derived. Afterwards, formulas for extracting the coupling coefficient $k$ between coupled multimode resonators and the external quality factor $Q_{e}$ are also obtained. Thereafter, the design procedure of coupled multiresonator multiband filters is similar to that of single-band filters. A tri-band microstrip filter with tri-mode resonators is successfully designed with the proposed method and fabricated, which validates this theory. [ABSTRACT FROM AUTHOR]

Wireless systems like radar and communication systems evolved progressively into multichannel systems over the past years. The most common multichannel concepts are multiple-input multiple-output (MIMO) and phased array architectures. In this paper, we present a transmitter monolithic microwave integrated circuit (MMIC) in a SiGe BiCMOS technology for its application, a mixed-mode frequency modulated continuous wave radar that is able to operate in both ways, in an MIMO and a beamforming mode. The MIMO mode is used for medium range and fast 3-D scans and the phased array mode is used for beamforming. This mode increases the effective output power of the transmitted signal beam and thus system dynamic and detection range. For this purpose, we developed ultrawideband quadrature (IQ) generation techniques to generate synchronous IQ-signals in each channel of our system to feed a vector adder, which is capable of shifting the phase for beamforming. The developed IQ-generation circuits are able to operate from 1 to 30 GHz, and the complete radar transmitter MMIC, including a power amplifier (PA), operates from 11 to 20 GHz. The IQ-generation phase error in this frequency range is below 6° and below 9°/3.2°rms for the IQ-generation together with vector modulator. The power consumption is 285 mW and the PA consumes 1.25 W with a maximum output power of the complete multimode TX MMIC of 24.4 dBm at 15 GHz. [ABSTRACT FROM AUTHOR]

Using the wireless signals to extend the sensors’ battery life in a network or make them battery-free becomes prominent with the high number of sensors and circuits that are desired in the Internet of Things. Decreasing the power consumption of the sensors is also a valid point. Colocating information signals and power signals at the same frequency further decreases the size of the sensor and the used bandwidth. To fulfill all the mentioned requirements, we used an integrated rectifier–receiver (IRR) to decrease the power consumption and fully utilize all the received signals without splitting signals. We propose a novel magnitude ratio modulation, utilizing two-tone signals. We extend this paper by introducing the ratio phase modulation (PM) and, finally, merging the ratio amplitude–PM. The main advantage of the proposed modulations is the degree of freedom that it is possible to deliver a constant dc power to the sensor even with symbol variations, that is not possible by using M-ASK or ON–OFF keying modulations. If the channel is narrowband, the demodulation of our proposed modulation is possible even by not knowing the channel’s attenuation. Since the IRR is highly nonlinear and this feature is used to fulfill our goals to receive power and information, we characterize the IRR’s to show the symbol diagram considering the influence of nonlinearity of the circuit and its limitation on modulation. We report the power conversion efficiency to prove that the IRR is harvesting RF energy well with the proposed modulation. [ABSTRACT FROM PUBLISHER]

This paper presents the first wirelessly synchronized multichip array (WSMA) in 65-nm CMOS. The proposed architecture makes use of a central wireless signal to synchronize an mm-wave array, eliminating the need for connecting wires between the array elements. Wireless injection locking of a single chip is successfully demonstrated, and a 3-dB linewidth of 400 Hz at a carrier frequency of 50 GHz is achieved (stability ratio of 8 ppb). In addition, a two-element WSMA with an array aperture greater than 20 wavelengths is demonstrated using the proposed transceiver architecture. The reported transceiver includes a receiving on-chip antenna, a low-noise amplifier, an injection-locked voltage-controlled oscillator, a buffer amplifier, an in-phase/quadrature generator, a phase shifter, a power amplifier, and a transmitting on-chip antenna. The chip is fabricated in a 65-nm CMOS process and occupies an area of 1.7 mm $\times 3.8$ mm. This paper sets the foundation for increasing the array aperture through wireless injection locking, extending traditional array systems into the high-resolution, narrow-beamwidth regime. [ABSTRACT FROM PUBLISHER]

Summary form only given, as follows. We are honored and delighted to introduce several accepted papers from the 2011 IEEE International Symposium on Radio-Frequency Integration Technology (RFIT2011) to the IEEE Microwave Theory and Techniques Society (IEEE MTT-S) community. RFIT is a relatively new and small focused forum for crossed disciplines in microelectronics and microwaves. It was established firstly as a workshop in Singapore in 2005 and became a symposium in 2009. The 2011 RFIT Symposium was held in Beijing, China, from November 30 to December 2, 2011, and it will move around IEEE Region 10. RFIT provides a forum for the integrated circuit and technology communities to meet and present the latest developments in integrated circuit design and technology and system integration with an emphasis on wireless communication systems and emerging applications such as terahertz, biology and health care, as well as emerging 3-D integration technologies. The 2011 RFIT received 87 contributed submissions from 14 countries, and accepted 42 papers after a peer-review process. An additional ten invited papers were presented in the program. The symposium consists of one day of tutorial and two days of technical sessions with a total of over 90 delegates. All presenters were invited to submit expanded versions of their papers, and several groups of authors submitted their papers. The papers were handled in the same way as all other submissions by the editorial staff and reviewed according to the same standards as other regular papers. Furthermore, they had to expand the technical content of the paper compared to the RFIT paper, which is not easy. We wish to express a special acknowledgment to this TRANSACTIONS' Editor-in-Chief, Dr. George E. Ponchak, for his unstinting help and advice. We express our gratitude to the expert reviewers who donated their time and effort to make detailed reviews of these papers. Finally, we are grateful to the authors for submitting their contributions and for their efficient working relationships with the editors and reviewers to meet the publication schedule. [ABSTRACT FROM PUBLISHER]

To reduce the weight of a satellite, an internal wireless system (IWS) for satellites was proposed in a previous study. It is a system that can communicate between the satellite’s subsystems by using wireless communication modules. In this paper, we propose a complete IWS for a satellite using microwave wireless power transmission technology. The design of a 5.8-GHz high efficiency rectifier circuit-based charge pump circuit is also presented. Furthermore, we introduced a class-F load that can process the third harmonic components. The rectifying efficiencies of a normal charge pump rectifier and a charge pump rectifier with the class-F load are theoretically compared. To improve the conversion efficiency of the charge pump rectifier, the applied voltages of diodes are adjusted. Owing to inserting the class-F load and adjusted the applied voltage of diodes in this circuit, the conversion efficiency of the charge pump circuit at 30 mW increases to about 78% at 30 mW in the simulation, and to about 71% conversion efficiency in the experiment. In addition, the output voltage is higher than 5 V at an optimal load 1300 $\Omega $ . [ABSTRACT FROM PUBLISHER]

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]

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]

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 presents a novel coherent full-duplex (FD) double-sided two-way ranging (CFDDS-TWR) technique for wireless locating and velocity measurement between separate radio units. The idea presented here is a quantum leap in wireless locating since it enables coherent ranging, continuous phase tracking, and velocity measurement between wireless units that operate incoherently with separate low-cost crystal oscillator clock sources. Frequency modulated continuous wave chirp sequences are exchanged in a FD manner between two radio units. The signals transmitted from two radio units are received, respectively, by each of the two units and down-converted in a mixer with the receiver’s own transmit signal to generate a beat signal in each unit. The two beat signals are then processed together, after one beat signal is transmitted to the partner unit. Phase coherent range and Doppler phase measurements can be conducted between incoherent radio units. The presented CFDDS-TWR technique also offers options for reducing noise-like distortions caused by mixing the products of uncorrelated phase noise. We show both analytically and experimentally that the described compensation method reduces the noise level and enhances the dynamic range of the ranging signals tremendously—as evidenced by an improvement of around 24 dB in our results. These unique signal and synchronization properties show that the CFDDS-TWR method is a highly accurate measurement approach. Results acquired with a 24-GHz test system in a 7- to 17-m range demonstrate a standard deviation in range and velocity of 0.25 mm and 0.05 mm/s, respectively. [ABSTRACT FROM AUTHOR]

A new class of in-phase and out-of-phase power dividers with constant equal-ripple frequency response and wide operating bandwidth is presented in this paper. The proposed design is based on microstrip-to-slotline transitions and slotline resonators. A slotted T-junction is adopted to split the power into two parts and obtain wideband isolation between the two output signals at the same time. The characteristic impedance of the transitions and resonators determines the operating bandwidth and in-band magnitude response. By reversing the placement direction of the slotline-to-microstrip transition, the electrical field is reversed, thus resulting in out-of-phase responses between output ports. A thorough analysis of the relations between the structure and the characteristic functions is provided to guide the selection of parameters of the structure in order to meet the design objectives. In the structure, simulation and measurement are conducted to verify the design method. For both in-phase and out-of-phase cases, more than 110% bandwidth has been achieved with excellent matching at all ports and isolation of output signals. Constant in-band ripple is obtained within the operating band of the power dividers, indicating that the proposed design can realise minimal power deviations, which is extremely desired in wireless systems. [ABSTRACT FROM AUTHOR]

This paper presents the proposal and design of multistate diplexer on uniform- and stepped stub-loaded resonators, that is, a three-state diplexer (TSD) and a four-state diplexer (FSD). The two proposed diplexers have an attractive application in a frequency-hopping system with miniaturization in their overall size. Next, three and four sets of second-order bandpass filters are applied to form the three and four filtering channels, respectively. These filtering channels are then used to comprise these multiple-state diplexers. In this way, compact size and high-frequency selectivity have been well achieved. For the purpose of demonstration, the prototypes of TSD and FSD are fabricated and measured. The measured results are found in good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

In this paper, we study the radio frequency (RF) backscatter for high data rate wireless communication with deep medical implants. The radar approach permits remote reading of the implant’s information. This means that the active transmitter is removed from the implant that results in significant power saving. We customize our design for wireless capsule endoscopy (WCE) application, which is used for streaming high data rate video signals for improved visualization of the gastrointestinal tract. An efficient antenna system is designed and integrated into the WCE prototype that generates large radar cross section (RCS) using a self-resonant antenna geometry. The antenna is reconfigurable using an active microwatt switch, which is controlled by the data stream. The switch alters the antenna RCS for an efficient modulation of the incident electromagnetic (EM) wave transmitted from outside the body. The antenna design considers the specific conditions of wave propagation in the biological environments and antenna loading with the lossy tissues. Polarization diversity using bistatic on-body reader antennas is used for communicating with the implant device. The on-body antennas can direct EM energy to the capsule device for improving the backscatter link performance. The feasibility study is demonstrated using numerical computations and experimentally validated in a liquid phantom and in-vivo animal experiments. A reliable backscatter data connectivity of 1 and 5 Mb/s is measured for the capsule in the gastrointestinal tract for the depths up to 10 cm using an acceptable level of RF radiations. [ABSTRACT FROM AUTHOR]

In this paper, we present a low-power event-driven receiver intended for miniaturized biomedical implants. The fully integrated system can operate by power harvesting from electromagnetic fields using a radio frequency-to-dc converter or through a 0.5-V voltage supply such as a rechargeable battery. Without any external component and calibration overhead, the proposed double-mixing receiver is operating at a frequency of 915-MHz industrial, scientific, and medical band and is robust to process, supply voltage, and body temperature variations. The proof-of-concept receiver is designed and implemented in a 0.13- $\mu \text{m}$ CMOS technology. The system occupies a silicon area of 0.75 mm2 and consumes only 9.1- $\mu \text{W}$ power while achieving a sensitivity of −48 and −39 dBm at the data rate of 1 and 100 kb/s, respectively. [ABSTRACT FROM AUTHOR]

This paper reports on a 15-Gb/s wireless link that employs a high-power resonant tunneling diode (RTD) oscillator as a transmitter (Tx). The fundamental carrier frequency is 84 GHz and the maximum output power is 2 mW without any power amplifier. The reported performance is over a 50-cm link, with simple amplitude shift keying modulation utilized. The 15-Gb/s data link shows correctable bit error rate (BER) of $4.1 \times 10^{-3}$ , while the lower data rates of 10 and 5 Gb/s show a BER of $3.6 \times 10^{-4}$ and $1.0 \times 10^{-6}$ , respectively. These results demonstrate that the RTD Tx is a promising candidate for the next-generation low-cost, compact, ultrahigh data rates wireless communication systems. [ABSTRACT FROM AUTHOR]

In this paper, we present a new behavioral model for digital predistortion (DPD) of RF power amplifiers in wireless transmitters. Derived from the decomposed vector rotation model, the new model uses magnitude-selective affine functions as nonlinear operators to construct nonlinear behavior of the model, leading to a highly efficient hardware implementation. Moreover, cross-terms are carefully redesigned based on a new formulation of model structure that not only improves the modeling performance but also significantly lowers the complexity of model extraction. Simulation and experimental results have demonstrated its superior performance and efficient hardware implementation, making this model well suitable for future DPD deployment in 5G small cell base stations where digital hardware resource is highly constrained. [ABSTRACT FROM AUTHOR]

Emerging broadband and millimeter-wave frequency applications, including 5G wireless communications, high-speed optical networks, radars, sensors, imaging and security systems, and measurement instrumentation, continue to expand and grow in the next decade. One of the key components of these systems is the broadband (including sub-6 GHz) and millimeter-wave power amplifier. The specific requirements, as well as the technology of choice (e.g., Si CMOS, SiGe, GaAs, GaN, and InP), are dictated by the application. This Transactions’ “Special Issue on Broadband and Millimeter-Wave Power Amplifiers” is aimed to publish technical papers focusing on the most recent research and development of broadband (including sub-6GHz) and millimeter-wave power amplifiers for emerging applications. The submitted papers went through the same peer-review process as regular submissions to this Transactions. After being carefully reviewed, 20 manuscripts were accepted for publication. The topics cover a wide range of areas, including millimeter-wave amplifiers in InP, Si SOI, SiGe, linearization techniques, 5G power amplifiers, and broadband and high-power GaN technologies. [ABSTRACT FROM AUTHOR]

This invited paper reviews the progress of silicon–germanium (SiGe) bipolar-complementary metal–oxide–semiconductor (BiCMOS) technology-based integrated circuits (ICs) during the last two decades. Focus is set on various transceiver (TRX) realizations in the millimeter-wave range from 60 GHz and at terahertz (THz) frequencies above 300 GHz. This article discusses the development of SiGe technologies and ICs with the latter focusing on the commercially most important applications of radar and beyond 5G wireless communications. A variety of examples ranging from 77-GHz automotive radar to THz sensing as well as the beginnings of 60-GHz wireless communication up to THz chipsets for 100-Gb/s data transmission are recapitulated. This article closes with an outlook on emerging fields of research for future advancement of SiGe TRX performance. [ABSTRACT FROM AUTHOR]

This paper discusses the feasibility of a real-time active matching circuit (MC) for wireless power transfer applications, especially for biomedical systems. One prototype of low-cost real-time automatic MC, utilizing a variable circuit topology, including discrete passives and p-i-n diodes, has been implemented and the principle has been verified by measurements. One genetic algorithm was introduced to optimize the design over a wide range of impedances to match. As a result of preliminary operation verification tests, the proposed real-time MC system results in improving the transfer coefficient in the range of 10–16-cm coil separation distance a maximum of 3.2 dB automatically in about 64 ms. Similar performance improvement results were observed in additional tests under misaligned conditions, as well as for nonsymmetrical Tx–Rx coil configurations further verifying the potential applicability of the proposed system to practical biomedical devices. [ABSTRACT FROM PUBLISHER]

Recent advances in software-defined radio (SDR) technology have been pushing mixed-signal circuits to higher frequencies and forcing system integration in a single chip. These new mixed-signal devices have the capability to replace part of what was hitherto the analog side of the radio circuit, and simultaneously add several advantages. This imposes on radio engineers the need to understand and cope with these new developments. In this paper, a new framework for mixed-signal behavioral modeling is presented and discussed. It is an extension of the well-known scattering parameters, termed as D-parameters. Both linear and nonlinear methodologies are considered and analyzed. Also, application examples of this framework are presented as a way to model, characterize, and thus improve mixed-signal systems. [ABSTRACT FROM PUBLISHER]

In this paper, a novel 8-phase-shift-keying (8-PSK) carrier recovery and demodulation method using a comparator and frequency divider is proposed. A proof-of-concept 8-PSK demodulator for high-data-rate millimeter-wave communication systems is designed and tested, which can support 8-PSK transmission up to 15 Gb/s with a bit error rate less than \10^-7. [ABSTRACT FROM AUTHOR]

In this paper, we propose a self-directed adaptive phased array control method using the low-frequency part of the signal for a millimeter-wave wireless personal area network, which can reduce the hardware requirement and power consumption compared with those of the conventional digital beamforming method. The signal from each element antenna of the antenna array is phase shifted and down converted to the baseband and then divided into two paths. The first paths are low-pass filtered to extract the low-frequency part of the signals for beamforming control. The second paths from all antennas are combined in-phase in an analog domain and then sampled by two high-speed A/D converters for demodulation. A beamforming algorithm using the sampled low-frequency part of the signal is also proposed. The beamforming calculation time is established as a function of the signal-to-noise ratio, the bandwidth of the low-frequency part, and the required phase control accuracy. The calculated values match the measured results. Using the IEEE 802.15.3c specifications with an eight-element array antenna, the calculation time is less than \5~\mu\s for initial beam establishment and less than \30~\mu\s for beam tracking. Therefore, high-speed beamforming is possible while reducing the power consumption. [ABSTRACT FROM AUTHOR]

Wireless body area network (WBAN) applications benefit extensively from the advantages offered by unique features of ultra-wideband (UWB) wireless communication, such as high data rate, low power consumption, and simple transmitter design. A major disadvantage in using UWB for WBAN applications is the complexities introduced by UWB receivers, such as high power consumption, poor receiver performance due to low sensitivity, and complex hardware implementation. This paper presents hardware implementation of a new communication system, where UWB is used for high data-rate transmission from sensor nodes and a 433-MHz industrial, scientific, and medical (ISM) band receiver is used for receiving low data-rate control messages at the sensor nodes. A full network system for WBAN applications has been implemented including a unique medium access control protocol. The proposed WBAN system is designed to dynamically control the pulses per bit value used for the UWB data communication using control messages received via the narrowband feedback link (i.e., the 433-MHz ISM link). This leads to dynamic bit error rate (BER) and power control at the sensor nodes, which improves the reliability of communication and power efficiency of sensor nodes under dynamic channel conditions. The performance of the system is evaluated in terms of BER, sensor initialization delay, and power consumption. This novel dual-band architecture utilizes the unique advantages offered by UWB communication and narrowband technology to enable high data rate, low-complexity hardware design, low power consumption, and small form factor for WBAN sensor systems. [ABSTRACT FROM AUTHOR]

An ultra-wideband (UWB)-based cognitive radio (CR) is a promising technique to utilize 3.1–10.6-GHz band efficiently for high data-rate short-range wireless connectivity even in overcrowdedness of the frequency spectrum. Frequency synthesizers tailored to the UWB-based CR should provide wide lock range, multiple frequency bands, and low in-band spurs while consuming low power. This paper investigates a low power, wide lock range, integer-N frequency synthesizer approach with 132-MHz frequency step and 57 subbands in the UWB band. Two-stage supply regulated differential ring oscillator provides linear and wide tuning range with voltage controlled oscillator gain of 22.5 GHz/V and low supply-noise sensitivity. A modular true-single-phase-clock programmable divider achieves wide operating frequency range of 0.1–6.5 GHz and power efficiency of 6.25 GHz/mW by compensating leakage current at the dynamic nodes with conditional latches. Replica-based digital calibration reduces the current mismatch of the charge pump to <1% for low in-band reference spurs of <−60 dBc. A frequency synthesizer test chip was fabricated in 65-nm complementary metal–oxide–semiconductor technology. The active area of the frequency synthesizer is 0.12 mm2. It achieves <−30-dBc integrated phase noise and enables the UWB-based CR to get bit error rate of <10−3 while consuming <−10.1 mW. [ABSTRACT FROM AUTHOR]

This paper proposes a novel double ground plane coaxial resonator that allows to realize two independent coaxial cavity modes in reduced physical volume. This configuration of compact high performance filters is an enabler for multiband transmitter architectures using modern radio frequency data convertors. The proposed approach benefits from simple design and design flexibility. The benefit of the proposed approach is the ease of design and the design flexibility. The proposed filters provide the ability to control the frequency, the bandwidth, and the introduction of transmission zeros separately for each band. A number of designs are presented to demonstrate the operation principle and the performance characteristics of the proposed filters. A $2 \times 4$ pole filter has been manufactured and tested with very good obtained results. [ABSTRACT FROM AUTHOR]

In this paper, patent pending self-temperature-compensated air-filled substrate-integrated waveguide (AFSIW) cavities and filters are proposed and demonstrated for high-performance and low-cost components, circuits, and systems on substrate. First, a theoretical multiphysics transmission line model is developed for the synthesis of self-temperature-compensated air-filled cavities. It is determined that temperature compensation can be achieved using an appropriate substrate material and dielectric sidewall slab width. Moreover, a postprocess temperature compensation technique is introduced to counterbalance potential fabrication errors. For demonstration purposes, a self-temperature-compensated first-order AFSIW filter (based on a single cavity) is fabricated and compared to its dielectric-less temperature-uncompensated counterpart. Then, a self-temperature-compensated fourth-order AFSIW filter centered at 21 GHz with 300-MHz bandwidth is designed and fabricated. It achieves a measured unloaded $Q$ -factor of 975 at ambient temperature and a measured central frequency thermal stability as low as 2.26 ppm/°C at −40 °C and 1.67 ppm/°C at 80 °C (without using any postprocess tuning), compared to −17.4 ppm/°C at −40 °C and −18.38 ppm/°C at 80 °C for its dielectric-less temperature-uncompensated counterpart. [ABSTRACT FROM AUTHOR]

In this paper, we propose a beam-oriented digital predistortion (BO-DPD) technique for power amplifiers (PAs) in hybrid beamforming massive multiple-input multiple-output (MIMO) transmitters, which can achieve linearization of the transmitted signal in the main beam direction and address the DPD implementation issue in the hybrid beamforming array. In massive MIMO hybrid beamforming transmitters, the conventional DPD to linearize each PA is impractical to implement for that the number of digital chains is less than the number of PAs; however, the BO-DPD can resolve this issue by constructing and linearizing the “virtual” main beam signal rather than single PAs. According to the beamforming weights for array elements, the feedback path combines all PA’s outputs to estimate the main beam signal for DPD processing. In addition, an average estimation method is also presented to broaden the linearized angle range around the main beam direction. A $4 \times 16$ (four subarrays and 16 antennas in each subarray) uniform linear array (ULA) simulation along with a $1 \times 2$ ULA at 2.5 GHz and a $2 \times 2$ ULA at 3.5-GHz experimental tests was performed. The experimental results show that the proposed technique and linearization angle range broadening method achieve up to 15-dB adjacent channel power ratio improvement and 10° linearization angle range in the main beam direction. [ABSTRACT FROM AUTHOR]

In this paper, a design method for multiband bandpass filters with compact configuration in substrate integrated waveguide is proposed by combining the single-band/dual-band synthesis method and the multimode resonator theory. The designed filters could generate multiple filtering passbands without expanding their entire physical size. In addition, all the passbands could be efficiently synthesized and designed with any prescribed order in theory, which has been rarely reported in multiband filters, especially in the design of quad-band filters. As examples, one third-order quad-band filter and one third-order tri-band filter are designed, fabricated, and measured. Good agreement is attained between their simulated and measured S-parameters, and both the two sets of results have verified the feasibility of the proposed design method and attractive performances of the designed multiband filters. [ABSTRACT FROM AUTHOR]

This paper presents a linear Doherty power amplifier (DPA) topology suitable for low-powered small cell and multiantenna fifth generation transceivers. The proposed topology relies on augmenting the conventional two-way DPA with a linearization amplifier (LA) in order to enhance its efficiency versus linearity tradeoff when driven with wideband modulated signals. For this, a study of the interactions between the LA and DPA circuitries is conducted, and a design strategy is developed to determine the circuit’s parameters that maximize the adjacent channel leakage ratio (ACLR) improvement while minimizing its power overhead. For validation purpose, this strategy is applied to design a proof of concept prototype with a center frequency of 800 MHz and an output peak envelope power of 12 W. Compared with the case where the LA is not integrated, more than 11-dB improvement of the ACLR was obtained at the prototype output when driven with modulated signals of up to 40 MHz of modulation bandwidth. Furthermore, an ACLR of about −45 dBc or better was maintained over a wide average power range. [ABSTRACT FROM PUBLISHER]

Chipped radio-frequency identification (RFID) sensor systems have been studied for structural health monitoring (SHM) applications. However, the use of chip in sensor tags and its standardized narrowband operation contribute shortcomings in cost, durability, and detection capability. This paper presents a novel use of the frequency signature-based chipless RFID for metal crack detection and characterization operating in ultra-wideband frequency. The vision is to implement a low-cost and high-temperature-resistant passive wireless sensor able to monitor the crack on a metallic structure with multiparameter detection. We propose a chipless RFID sensor tag integrating four tip-loaded dipole resonators as a 4-bit ID encoder and a circular microstrip patch antenna (CMPA) resonator as a crack sensor. The radar cross section spectrum of the chipless RFID sensor tag generates four resonant frequencies from the dipole resonators and a resonant frequency from the CMPA resonator. Simulation and experimental results show that the resonant frequency shift of the CMPA is a useful feature to indicate the crack orientation and the crack width on a metallic structure. The direction of the resonant frequency shift represents the orientation of the crack, while the magnitude of the resonant frequency shift is proportional to the width of the crack. Furthermore, the experimentation with a natural fatigue crack sample proves that the proposed sensor tag is capable of detecting submillimeter cracks. [ABSTRACT FROM PUBLISHER]