Showing papers in "IEEE Transactions on Microwave Theory and Techniques in 2016"
TL;DR: A 3GPP-like stochastic IR channel model is developed from measured power delay profiles, angle of departure, and angle of arrival power spectra, supporting air interface design of mmWave transceivers, filters, and multi-element antenna arrays.
Abstract: This paper presents a 3-D statistical channel impulse response (IR) model for urban line of sight (LOS) and non-LOS channels developed from 28- and 73-GHz ultrawideband propagation measurements in New York City, useful in the design of 5G wireless systems that will operate in both the ultra-high frequency/microwave and millimeter-wave (mmWave) spectrum to increase channel capacities. A 3GPP-like stochastic IR channel model is developed from measured power delay profiles, angle of departure, and angle of arrival power spectra. The extracted statistics are used to implement a channel model and simulator capable of generating 3-D mmWave temporal and spatial channel parameters for arbitrary mmWave carrier frequency, signal bandwidth, and antenna beamwidth. The model presented here faithfully reproduces realistic IRs of measured urban channels, supporting air interface design of mmWave transceivers, filters, and multi-element antenna arrays.
564 citations
TL;DR: In this paper, the authors developed an analytical theory for magnetless non-reciprocity circuits, which allows determining the conditions for designing them with optimum characteristics, and presented two designs based on lumped and distributed-element circuits for applications at the very high-frequency and wireless-communications bands, respectively.
Abstract: Nonreciprocal components are ubiquitous in electronic and optical systems. To date, the use of magneto-optical materials has been the prevailing method to achieve nonreciprocity. However, magnetic-based devices are accompanied by several drawbacks, such as the requirement of bulky biasing devices and their incompatibility with semiconductor technology, which make their integration challenging. Recently, strong magnetless nonreciprocity was demonstrated in spatiotemporally modulated coupled-resonator networks as a result of an effective spin imparted to the structure by an RF signal. These structures can be easily integrated, and they potentially exhibit good power and noise performance, as any parametric device. Here, we develop an analytical theory for such devices, which allows determining the conditions for designing them with optimum characteristics, and present two designs based on lumped- and distributed-element circuits for applications at the very high-frequency and wireless-communications bands, respectively. The circulators exhibit large isolation and low insertion loss within reasonable modulation requirements. Furthermore, they can be realized with a modulation frequency substantially lower than the input frequency, significantly simplifying the design. Measurements for the lumped-element design are provided and show good agreement with theory and full-wave simulations. The nonlinear characteristics of the presented designs are also studied, and possible ways to reduce nonlinear distortion by increasing the static bias of the varactors or using advanced varactor topologies are explored.
190 citations
TL;DR: In this article, the electric and magnetic field (EMF) safety aspects of a wireless power transfer (WPT) system based on magnetic resonant coupling between two coils are discussed.
Abstract: This paper deals with the electric and magnetic field (EMF) safety aspects of a wireless power transfer (WPT) system based on magnetic resonant coupling between two coils. The primary coil is assumed to be on-body, while the secondary coil is assumed to be inside the human body and connected to a battery recharge system of an active implantable medical device such as a pacemaker. This study allows us to identify a good preliminary solution of the WPT coil configuration, compensation capacitor topology, and operational frequency. Demonstrative WPT systems operating at two different frequencies are proposed in order to verify the WPT performances. The EMF safety has been finally assessed by numerical dosimetry studies using anatomically realistic human body models revealing no particular concerns about this application.
176 citations
TL;DR: In this article, a single-compound triple complementary split-ring resonator (SC-TCSRR) was used to determine the complex permittivity and thickness of a material under test (MUT).
Abstract: This paper presents a novel noncontact measurement technique that entails using a single-compound triple complementary split-ring resonator (SC-TCSRR) to determine the complex permittivity and thickness of a material under test (MUT). The proposed technique overcomes the problem engendered by the existence of air gaps between the sensor ground plane and the MUT. In the proposed approach, a derived governing equation of the resonance frequencies is used to estimate the thickness and complex permittivity of the MUT by calculating the resonant frequency $(f_{{ r}})$ and magnitude response in a single-step noncontact measurement process. This study theoretically analyzed and experimentally verified a simple and low-cost SC-TCSRR measurement method for assessing materials in a noncontact method. For a 0.2-mm air gap, the experiments yielded average measurement errors of 4.32% and 5.05% for the thickness and permittivity, respectively. The proposed SC-TCSRR technique provides excellent solutions for reducing the effect of air-gap conditions on permittivity, thickness, and loss tangent in noncontact measurements.
174 citations
TL;DR: In this paper, a 3-dimensional frequency selective rasorber (FSR) is proposed, which consists of a 2-D periodic array of parallel waveguides with a metallic post in the center.
Abstract: This paper introduces the concept, theory, and design of 3-D frequency selective rasorbers (FSRs), which have a transmission window transparent to the incident electromagnetic wave with two absorption bands located at both sides of the window. The proposed rasorber consists of a 2-D periodic array of parallel waveguides. The transmission characteristics with high selectivity are produced by lossless resonators implemented using a parallel waveguide with a metallic post in the center. On the other hand, the absorption bands are obtained by lossy resonators constructed by loading of lumped resistors at the entry port of short-circuited waveguides. Physical mechanism of the proposed FSRs is explained with the aid of an equivalent circuit model, and relevant design equations are formulated. Two prototypes of the designed FSRs are fabricated and measured as a proof of concept. The experimental results show that a bandwidth of 50% for the insertion loss less than 3 dB and two absorption bands with a high absorptance of around 90% can be achieved. Moreover, the simulated results also show that the proposed structure exhibits stable performance against the variation of the incident angle of an incoming plane wave.
165 citations
TL;DR: In this paper, the authors proposed a new set of coil design formulas for high efficiency and low harmonic currents and a new design procedure for low leakage of magnetic fields for high-power wireless power transfer (WPT) system.
Abstract: For wireless charging of electric vehicle (EV) batteries, high-frequency magnetic fields are generated from magnetically coupled coils. The large air-gap between two coils may cause high leakage of magnetic fields and it may also lower the power transfer efficiency (PTE). For the first time, in this paper, we propose a new set of coil design formulas for high-efficiency and low harmonic currents and a new design procedure for low leakage of magnetic fields for high-power wireless power transfer (WPT) system. Based on the proposed design procedure, a pair of magnetically coupled coils with magnetic field shielding for a 1-kW-class golf-cart WPT system is optimized via finite-element simulation and the proposed design formulas. We built a 1-kW-class wireless EV charging system for practical measurements of the PTE, the magnetic field strength around the golf cart, and voltage/current spectrums. The fabricated system has achieved a PTE of 96% at the operating frequency of 20.15 kHz with a 156-mm air gap between the coils. At the same time, the highest magnetic field strength measured around the golf cart is 19.8 mG, which is far below the relevant electromagnetic field safety guidelines (ICNIRP 1998/2010). In addition, the third harmonic component of the measured magnetic field is 39 dB lower than the fundamental component. These practical measurement results prove the effectiveness of the proposed coil design formulas and procedure of a WPT system for high-efficiency and low magnetic field leakage.
160 citations
TL;DR: An advanced technique to develop combined neural network and pole-residue-based transfer function models for parametric modeling of electromagnetic (EM) behavior of microwave components and can obtain better accuracy in challenging applications involving high dimension of geometric parameter space and large geometrical variations, compared with conventional modeling methods.
Abstract: This paper proposes an advanced technique to develop combined neural network and pole-residue-based transfer function models for parametric modeling of electromagnetic (EM) behavior of microwave components. In this technique, neural networks are trained to learn the relationship between pole/residues of the transfer functions and geometrical parameters. The order of the pole-residue transfer function may vary over different regions of geometrical parameters. We develop a pole-residue tracking technique to solve this order-changing problem. After the proposed modeling process, the trained model can be used to provide accurate and fast prediction of the EM behavior of microwave components with geometrical parameters as variables. The proposed method can obtain better accuracy in challenging applications involving high dimension of geometrical parameter space and large geometrical variations, compared with conventional modeling methods. The proposed technique is effective and robust especially in solving high-order problems. This technique is illustrated by three examples of EM parametric modeling.
148 citations
TL;DR: In this paper, the authors focus on the analysis of splitter/combiner microstrip sections where each branch is loaded with a complementary split ring resonator (CSRR), and a model that includes lumped elements (accounting for the CSRR-loaded line sections) and distributed components (corresponding to the transmission lines) is proposed and used to infer the position of the transmission zeros.
Abstract: This paper focuses on the analysis of splitter/ combiner microstrip sections where each branch is loaded with a complementary split ring resonator (CSRR). The distance between CSRRs is high, and hence, their coupling can be neglected. If the structure exhibits perfect symmetry with regard to the axial plane, a single transmission zero (notch) at the fundamental resonance of the CSRR, arises. Conversely, two notches (i.e., frequency splitting) appear if symmetry is disrupted, and their positions are determined not only by the characteristics of the CSRRs but also by the length of the splitter/combiner sections. A model that includes lumped elements (accounting for the CSRR-loaded line sections) and distributed components (corresponding to the transmission lines) is proposed and used to infer the position of the transmission zeros. Frequency splitting is useful for the implementation of differential sensors and comparators based on symmetry disruption. Using the model, the length of the splitter/combiner sections necessary to optimize the sensitivity of the structures as sensing elements is determined. Parameter extraction and comparison with electromagnetic simulations and measurements in several symmetric and asymmetric structures is used to validate the model. Finally, a prototype device sensor/comparator based on the proposed CSRR-loaded splitter/combiner microstrip sections is presented.
141 citations
TL;DR: In this paper, a 60 GHz wafer-scale transmit phased array with 64 and 256 elements spaced λ λ 2 /2 apart in the $x$ - and $y$ -directions, and occupying an area of 21.4 $\times $ 22 mm2 (471 mm2) and 41.4 $ 42 mm2(1740 mm2), respectively, is presented.
Abstract: This paper presents 60-GHz wafer-scale transmit phased arrays with 64- and 256-elements spaced $\lambda $ /2 apart in the $x$ - and $y$ -directions, and occupying an area of 21.4 $\times $ 22 mm2 (471 mm2) and 41.4 $\times $ 42 mm2 (1740 mm2), respectively. The 64-element phased array is built as a complete reticle and includes 64 independent transmit channels with 5-b phase control, 3-b (9 dB) amplitude control, a saturated output power of 3 dBm at the antenna port, a 1–64 distribution network with redundant line amplifiers, and a high-efficiency on-chip antenna at each element. In addition, redundant serial digital interface and power strips, dual series metal–insulator–metal capacitors, and multiple RF inputs are employed for improved yield. The 256-element array uses the same phased-array blocks as the 64-element design, but is built using a subreticle stitching technique so as to result in a chip which is larger than the standard reticle size (22 $\times $ 22 mm2). The 64- and 256-element arrays result in a half-power beamwidth of 12° and 6° in the $E$ - and $H$ -planes, a directivity of 23 and 29 dB, respectively, and scan to ±55° in the $E$ - and $H$ -planes with near-ideal patterns and a cross-polarization level of lesser than −30 dB. The measured equivalent isotropically radiated power (EIRP) of the 64-element array is 38 dBm at 62 GHz with a 3-dB bandwidth of 61–63 GHz, while that of the 256-element array is 45 dBm at 61 GHz with a 3-dB beamwidth of 58–64 GHz. A 1–4-Gb/s communication system is also demonstrated using the 64-element phased array up to ±45° scan angles, and at 4-, 30-, and 100-m ranges. To the best of our knowledge, this paper represents the first demonstration of large size (64- and 256-element) phased-array transmitters on a single wafer.
138 citations
TL;DR: Different from the frequency-domain “micro-Doppler” approach, the proposed remote gesture recognition based on linear motion reconstruction is able to recognize definitive signatures for the corresponding motions, exhibiting promising potential in practical applications of human-computer interaction.
Abstract: Short-range continuous-wave Doppler radar sensors have been mainly used for noncontact detection of various motions. In this paper, we investigate the feasibility to implement the function of a remote mouse, an input device of a computer, by recognizing human gestures based on a dual-channel Doppler radar sensor. Direct conversion architecture, symmetric subcarrier modulation, and bandpass sampling techniques are used to obtain a cost-effective solution. An arcsine algorithm and a motion imaging algorithm are proposed to linearly reconstruct the hand and finger motions in a 2-D plane from the demodulated Doppler phase shifts. Experimental results verified the effectiveness of the proposed architecture and algorithms. Different from the frequency-domain “micro-Doppler” approach, the proposed remote gesture recognition based on linear motion reconstruction is able to recognize definitive signatures for the corresponding motions, exhibiting promising potential in practical applications of human–computer interaction.
136 citations
TL;DR: In this article, a single-series circuit with one double diode on a low-cost, lossy FR-4 substrate was proposed for RF energy harvesting, where rectennas were connected in series configuration (voltage summing), forming rectenna arrays.
Abstract: This work presents an efficient and high-sensitivity radio frequency (RF) energy harvesting supply. The harvester consists of a single-series circuit with one double diode on a low-cost, lossy FR-4 substrate, despite the fact that losses decrease RF harvesting efficiency. The design targeted minimum reflection coefficient and maximum rectification efficiency, taking into account not only the impedance matching network, but also the rectifier microstrip trace dimensions and the load. The simulated and measured rectenna efficiency was 28.4% for $-\hbox{20-dBm}$ power input. In order to increase sensitivity, i.e., ability to harvest energy and operate at low power density, rectennas were connected in series configuration (voltage summing), forming rectenna arrays. The proposed RF harvesting system ability was tested at various input power levels, various sizes of rectenna arrays, with or without a commercial boost converter, allowing operation at RF power density as low as 0.0139 $\mu \hbox{W/cm}^{2}$ . It is emphasized that the boost converter, whenever used, was self-started, without any additional external energy. The system was tested in supplying a scatter radio sensor, showing experimentally the effect of input power density on the operational cold start duration and duty cycle of the sensor.
TL;DR: In this paper, a symmetrical Doherty power amplifier with an extended efficiency range is proposed, achieving an average power-added efficiency of 50% and adjacent power leakage ratio of $-{\hbox{49 dBc}}$ with 9dB peak-to-average power-ratio 20-MHz long-term evolution test signals.
Abstract: A symmetrical Doherty power amplifier (PA) with an extended efficiency range is proposed. This paper proves the existence of a class of symmetrical Doherty PAs having efficiency peaks for back-off levels larger than 6 dB. A design technique is developed that maintains the full voltage and current swings of both the main and auxiliary transistors. The concept is experimentally verified in a 1.95-GHz 25-W circuit demonstrator fabricated using identical GaN HEMT devices. An average power-added efficiency of 50% and adjacent power leakage ratio of $-{\hbox{49 dBc}}$ is obtained with 9-dB peak-to-average power-ratio 20-MHz long-term evolution test signals.
TL;DR: A Ka-band highly linear power amplifier (PA) is implemented in 28-nm bulk CMOS technology using a deep class-AB PA topology with appropriate harmonic control circuit, highly linear and efficient PAs are designed at millimeter-wave band.
Abstract: A Ka-band highly linear power amplifier (PA) is implemented in 28-nm bulk CMOS technology. Using a deep class-AB PA topology with appropriate harmonic control circuit, highly linear and efficient PAs are designed at millimeter-wave band. This PA architecture provides a linear PA operation close to the saturated power. Also elaborated harmonic tuning and neutralization techniques are used to further improve the transistor gain and stability. A two-stack PA is designed for higher gain and output power than a common source (CS) PA. Additionally, average power tracking (APT) is applied to further reduce the power consumption at a low power operation and, hence, extend battery life. Both the PAs are tested with two different signals at 28.5 GHz; they are fully loaded long-term evolution (LTE) signal with 16-quadrature amplitude modulation (QAM), a 7.5-dB peak-to-average power ratio (PAPR), and a 20-MHz bandwidth (BW), and a wireless LAN (WLAN) signal with 64-QAM, a 10.8-dB PAPR, and an 80-MHz BW. The CS/two-stack PAs achieve power-added efficiency (PAE) of 27%/25%, error vector magnitude (EVM) of 5.17%/3.19%, and adjacent channel leakage ratio (ACLR $_{\mathrm{ E-UTRA}}$ ) of −33/−33 dBc, respectively, with an average output power of 11/14.6 dBm for the LTE signal. For the WLAN signal, the CS/2-stack PAs achieve the PAE of 16.5%/17.3%, and an EVM of 4.27%/4.21%, respectively, at an average output power of 6.8/11 dBm.
TL;DR: In this paper, the authors present a direct-conversion quadrature transmitter and receiver chipset at 240 GHz, which is implemented in a 0.13-μm SiGe bipolar-CMOS technology.
Abstract: This paper presents a fully integrated direct-conversion quadrature transmitter and receiver chipset at 240 GHz. It is implemented in a 0.13- $\mu{\hbox{m}}$ SiGe bipolar-CMOS technology. A wideband frequency multiplier ( $\times$ 16) based local-oscillator (LO) signal source and a wideband on-chip antenna designed to be used with an external replaceable silicon lens makes this chipset suited for applications requiring fixed and tunable LO. The chipset is packaged in a low-cost FR4 printed circuit board resulting in a complete solution with compact form-factor. At 236 GHz, the effective-isotropic-radiated-power is 21.86 dBm and the minimum single-sideband noise figure is 15 dB. The usable RF bandwidth for this chipset is 65 GHz and the 6-dB bandwidth is 17 GHz. At the system level, we demonstrate a high data-rate communication system where an external modem is operated in its two IF-bandwidth modes (250 MHz and 1 GHz). For the quadrature phase-shift keying modulation scheme, the measured data rate is 2.73 Gb/s (modem 1-GHz IF) with bit-error rate of ${\hbox{10}}^{-9}$ for a 15-cm link. The estimated data rate over the 17-GHz RF bandwidth is, hence, 23.025 Gb/s. Also, higher order modulation schemes like 16 quadrature amplitude modulation (QAM) with a data rate of 0.677 Gb/s and 64-QAM with a data rate of 1.0154 Gb/s (modem 250-MHz IF) is demonstrated. A second application demonstrator is presented where the wide tunable RF bandwidth of the chipset is used for material characterization. It is used to characterize an FR4 material (DE104) over the 215–260-GHz range.
TL;DR: In this article, the authors describe a design and measurement results for a lens antenna system for a $E$ -band having 2-D beam-steering capability, which is demonstrated with the lens having the maximum measured directivity of 36.7 dB.
Abstract: The new services available through smart devices require very high cellular network capacity. The capacity requirement is expected to increase exponentially with the forthcoming 5G networks. The only available spectrum for truly wideband communication (>1 GHz) is at millimeter wavelengths. The high free space loss can be overcome by using the directive and beam-steerable antennas. This paper describes a design and the measurement results for a lens antenna system for $E$ -band having 2-D beam-steering capability. Continuous beam-switching range of about $\pm 4 {^{\circ }} \times \pm 17^{\circ }$ is demonstrated with the lens having the maximum measured directivity of 36.7 dB. Link budget calculation for backhaul application using the presented lens antenna system is presented and compared with the measurement results of the implemented demo system.
TL;DR: In this article, a symmetric spoof surface plasmon (SSP)-based slow-wave transmission line (SW-TL) with compact transition, low ohmic loss, and low crosstalk between SW-TLs is proposed and investigated.
Abstract: The symmetric spoof surface plasmon (SSP)-based slow-wave transmission line (SW-TL) with compact transition, low ohmic loss, and low crosstalk between SW-TLs is proposed and investigated. First, the SSP cells are modeled by equivalent circuit elements. The proposed equivalent circuit model is appealing for the integration of SW-TLs with other microwave circuits. With the symmetricity, the SW-TLs are readily realized by a compact mode converter providing gradual impedance, momentum, and polarization matching from guided waves to spoof microwave plasmons. Then, simulation studies and experiments verify that the proposed SSP SW-TL features as low as half the ohmic loss of the traditional counterparts. After that, the low mutual coupling between the proposed SSP SW-TLs is numerically and experimentally substantiated and showed to be up to 10 dB lower than that between conventional microstrip TLs. The proposed low loss, highly isolated and compact SW-TL along with the reliable circuit model enables the further exploitation of promising spoof plasmon modes in microwave technology.
TL;DR: In this paper, an iterative learning algorithm is proposed to identify the optimal power amplifier (PA) input signal that drives the PA to the desired linear output response, and the parameters of the predistorter are estimated using standard modeling approaches, e.g., least squares.
Abstract: This paper proposes a new technique to identify the parameters of a digital predistorter based on iterative learning control (ILC). ILC is a well-established control theory technique that can obtain the inverse of a system. Instead of focusing on identifying the predistorter parameters, the technique proposed here first uses an iterative learning algorithm to identify the optimal power amplifier (PA) input signal that drives the PA to the desired linear output response. Once the optimal PA input signal is identified, the parameters of the predistorter are estimated using standard modeling approaches, e.g., least squares. To this end, in this paper, we present a complete derivation of an ILC scheme suitable for the linearization of PAs, which includes convergence conditions and the derivation of two learning algorithms. The proposed ILC scheme and parameter identification technique were demonstrated experimentally and compared with the indirect learning architecture (ILA) and direct learning architecture (DLA). The experimental results show that, even for the most difficult cases, the proposed ILC scheme can successfully linearize the PA. The experimental results also indicate that the proposed parameter identification technique is more robust to measurement noise than ILA and can provide better linearity performance when the PA nonlinearities are strong. In addition, the proposed parameter identification technique can achieve similar or better linearity performance than DLA but with a simpler identification process.
TL;DR: In this paper, the authors present different coupling mechanisms and feeding techniques for the design of quarter-mode SIW filters: side coupling and corner coupling are considered, highlighting the advantages and disadvantages of the two techniques.
Abstract: This paper presents a systematic investigation of quarter-mode filters in substrate integrated waveguide (SIW) technology. This class of filters is particularly convenient because it combines the features of SIW structures with the improvement of size reduction. After a thorough analysis of the quarter-mode SIW cavity, this paper presents different coupling mechanisms and feeding techniques for the design of quarter-mode SIW filters: side coupling and corner coupling are considered, highlighting the advantages and disadvantages of the two techniques. Novel filter topologies are introduced, with the design and experimental verification of simple filters and their extension to higher order filter structures. Techniques to introduce transmission zeros are described and demonstrated. Moreover, the combination of quarter-mode SIW cavities and coplanar waveguide resonators leads to increasing the filter order to higher order and allows the implementation of quasi-elliptic filters.
TL;DR: In this paper, a modified elliptic low-pass filtering (LPF) matching network (MN) was proposed to provide a sharp impedance transition from the higher end of the fundamental frequency band to the lower end of second harmonic band.
Abstract: This paper proposes a design approach for a broadband and high-efficiency continuous inverse Class-F ( ${\text {CCF}}^{-1}$ ) power amplifier (PA) based on a modified elliptic low-pass filtering (LPF) matching network (MN). From theoretical and practical perspectives, the importance of a swift impedance transition from the higher end of the fundamental frequency band to the lower end of the second harmonic band is discussed, when designing a broadband single-mode PA. After being compared with widely used Chebyshev LPF MNs, a modified elliptic LPF MN, which provides a sharp roll-off, is utilized to provide the required rapid transition. A step-by-step design procedure of the proposed modified elliptic LPF MN is presented. Experimental results show that a high-efficiency ${\text {CCF}}^{-1}$ PA is realized from 1.35 to 2.5 GHz (fractional bandwidth = 60%) with measured drain efficiency of 68%–82% and output power of 41.1–42.5 dBm. When stimulated by a 20-MHz LTE signal with an average output power of approximately 34.5 dBm, the proposed PA, combined with digital pre-distortion, achieved adjacent channel leakage ratios (ACLRs) below $-{\text {45 dBc}}$ , with average efficiency (AE) ranging from 37% to 45.8%. Similar performance is measured when the proposed PA is driven by a dual-band dual-mode modulated signal with a 100-MHz instantaneous bandwidth at a center frequency of 2.14 GHz.
TL;DR: In this article, a broadband Doherty power amplifier based on the continuous mode technique (C-DPA) is proposed, which is focused on manipulating harmonic components in a DPA structure to improve bandwidth and efficiency.
Abstract: In this paper, a novel broadband Doherty power amplifier based on the continuous-mode technique (C-DPA) is proposed. The amplifier is focused on manipulating harmonic components in a Doherty power amplifier (DPA) structure to achieve improved bandwidth and efficiency. In a conventional DPA, harmonic isolation is typically required between the two transistors to prevent them from modulating each other at harmonic frequencies. However, as presented in this paper, such isolation is not actually necessary. On the contrary, by allowing the two transistors to modulate each other at harmonic frequencies with the help of a properly designed postharmonic tuning network, a series of highly efficient DPA modes can be created over a continuous frequency band, leading to a broadband C-DPA. Based on the proposed method, an example of a C-DPA working from 1.65 to 2.75 GHz was designed. According to the measured results, the designed C-DPA exhibits a 52%–66% efficiency at a −6 dB power backoff and a power utilization factor higher than 1.08 over the 1.1-GHz band. In addition, when simulated by a 7.5-dB peak-to-average power ratio 20-MHz LTE signal, the example C-DPA exhibits an efficiency of 46%–62% while maintaining an adjacent channel power ratio below −45 dBc after linearization over the full 1.1-GHz band. To the best of our knowledge, this is the first proposed C-DPA and a state-of-the-art performance for broadband DPAs.
TL;DR: In this paper, two W-band waveguide bandpass filters were fabricated using laser micromachining and 3-D printing techniques, one fabricated from a single metal workpiece and the other from polymer resin.
Abstract: This paper presents two W-band waveguide bandpass filters, one fabricated using laser micromachining and the other 3-D printing. Both filters are based on coupled resonators and are designed to have a Chebyshev response. The first filter is for laser micromachining and it is designed to have a compact structure allowing the whole filter to be made from a single metal workpiece. This eliminates the need to split the filter into several layers and therefore yields an enhanced performance in terms of low insertion loss and good durability. The second filter is produced from polymer resin using a stereolithography 3-D printing technique and the whole filter is plated with copper. To facilitate the plating process, the waveguide filter consists of slots on both the broadside and narrow side walls. Such slots also reduce the weight of the filter while still retaining the filter’s performance in terms of insertion loss. Both filters are fabricated and tested and have good agreement between measurements and simulations.
TL;DR: In this paper, a gallium nitride Doherty power amplifier (DPA) using an integrated compensating reactance (CR) for broadband operation is presented, where an additional quarterwavelength transmission line is integrated in the peaking amplifier output to compensate the load impedance of the carrier amplifier in the low power region and thus enhance the backoff efficiency over a wide frequency range without affecting the Doherty load modulation at saturation.
Abstract: This paper presents a high-efficiency gallium nitride Doherty power amplifier (DPA) using an integrated compensating reactance (CR) for broadband operation. With an additional quarter-wavelength transmission line integrated in the peaking amplifier output, a CR is generated to compensate the load impedance of the carrier amplifier in the low-power region and thus enhance the back-off efficiency over a wide frequency range without affecting the Doherty load modulation at saturation. For this purpose, a peaking output matching network (OMN) is employed to convert the output impedance of the peaking device into quasi-short circuit when it is off and achieve proper impedance matching when it is on. A two-point matching technique using the transmission ( $ABCD$ ) matrix is employed to design such desired OMN. Measurement results show that the DPA has a 6-dB back-off efficiency of 50%–55% and a saturated efficiency of 57%–71% over the frequency band of 1.7–2.8 GHz (49% fractional bandwidth). When driven by a 20-MHz long term evolution modulated signal at 6.5-dB back-off power, the DPA can achieve an average efficiency of more than 50% with high linearity after linearization over the design frequency band.
TL;DR: To further enhance the accuracy of the HR estimation, a recently developed state-space method has been successfully combined with CSD and AD techniques and over 10 dB improvements in SNR is demonstrated.
Abstract: Ultra-wideband (UWB) pulse Doppler radars can be used for noncontact vital signs monitoring of more than one subject. However, their detected signals typically have low signal-to-noise ratio (SNR) causing significant heart rate (HR) detection errors, as the spurious harmonics of respiration signals and mixed products of respiration and heartbeat signals (that can be relatively higher than heartbeat signals) corrupt conventional fast Fourier transform spectrograms. In this paper, we extend the complex signal demodulation (CSD) and arctangent demodulation (AD) techniques previously used for accurately detecting the phase variations of reflected signals of continuous wave radars to UWB pulse radars as well. These detection techniques reduce the impact of the interfering harmonic signals, thus improving the SNR of the detected vital sign signals. To further enhance the accuracy of the HR estimation, a recently developed state-space method has been successfully combined with CSD and AD techniques and over 10 dB improvements in SNR is demonstrated. The implementation of these various detection techniques has been experimentally investigated and full error and SNR analysis of the HR detection are presented.
TL;DR: It is demonstrated that the penetration depth in both water and saline has a clear dependence on the probe diameter, but is remarkably uniform over frequency and with respect to the intervening liquid permittivity.
Abstract: We have performed a series of experiments, which demonstrate the effect of open-ended coaxial diameter on the depth of penetration. We used a two-layer configuration of a liquid and movable cylindrical piece of either Teflon or acrylic. The technique accurately demonstrates the depth in a sample for which a given probe diameter provides a reasonable measure of the bulk dielectric properties for a heterogeneous volume. In addition, we have developed a technique for determining the effective depth for a given probe diameter size. Using a set of simulations mimicking four 50- $\Omega $ coaxial cable diameters, we demonstrate that the penetration depth in both water and saline has a clear dependence on the probe diameter, but is remarkably uniform over frequency and with respect to the intervening liquid permittivity. Two different 50- $ \Omega $ commercial probes were similarly tested and confirm these observations. This result has significant implications to a range of dielectric measurements, most notably in the area of tissue property studies.
TL;DR: In this paper, the authors examined the possibility to code information thanks to the magnitude level of the radar cross section (RCS) in addition to the more classical technique of frequency position (FP).
Abstract: Hybrid coding techniques have been proposed recently to improve the coding capacity of chipless RF identification (RFID) tag. This paper examines the possibility to code information thanks to the magnitude level of the radar cross section (RCS) in addition to the more classical technique of frequency position (FP). Single-layer tags based on C-folded dipoles are designed to have different magnitude levels. A magnitude span of up to 15.2 dB is obtained for coupled resonators. A magnitude resolution of 3.5 dB is evaluated for practical applications based on the measurement of the realized tags in different configurations. The problem of tags applied to an unknown object is considered and a compensation technique is proposed for an object similar to a thin dielectric plate.
TL;DR: In this paper, a new design of an antenna array with integrated functions of filtering, harmonics suppression, and radiation is proposed, which employs a multi-port network of coupled resonators.
Abstract: In this paper, a new design of an antenna array with integrated functions of filtering, harmonics suppression, and radiation is proposed. The device employs a multi-port network of coupled resonators, which is synthesized and designed as a whole to fulfill the functions of filtering, power combination/division, and radiation. The 50- $\Omega $ interfaces between the cascaded filter, power divider, and antenna in traditional RF front-ends are eliminated to achieve a highly integrated and compact structure. A novel resonator-based four-way out-of-phase filtering power divider is proposed and designed. It is coupled to the patch array, rendering a fourth-order filtering response. The coupling matrix of the resonator network is synthesized. The physical implementations of the resonators and their couplings are detailed. Compared to a traditional patch array, the integrated filtering array shows an improved bandwidth and frequency selectivity. In addition, the harmonic of the antenna array is suppressed due to the use of different types of resonators. To verify the concept, a $2\times 2$ filtering array at S-band is designed, prototyped, and tested. Good agreement between simulations and measurements has been achieved, demonstrating the integrated filtering antenna array has the merits of wide bandwidth, high frequency selectivity, harmonics suppression, stable antenna gain, and high polarization purity.
TL;DR: In this paper, the authors implemented the first ultralong-range chipless sensing sticker, by providing more than an order of magnitude increase in reading range, compared with the state of the art.
Abstract: In this effort, the authors implement the first ultralong-range chipless sensing sticker, by providing more than an order of magnitude increase in reading range, compared with the state of the art. The theoretical advantages of the use of millimeter-wave frequencies for high-performance chipless radio-frequency identification (RFID) sensor implementations are first argued before both a new fully inkjet-printed flexible device, based on the Van-Atta reflectarray structure, as well as a new chipless RFID polarimetric interrogation, and time-frequency data-processing approach is then presented and implemented, for operation in the Ka-band. The array, fully inkjet printed on Kapton HN polyimide, was demonstrated as being robust to variations of interrogation angle (between ±70° from normal), as well as to bending. With its demonstrated range, in excess of 30 m, and its proven adequacy for dense multitag and multisensing implementations in indoor environments, the structure may set the foundation for the emergence of flexible printable low-cost sensing smart skins for the Internet of Things.
TL;DR: In this article, a complete solution from parameter extraction to large-signal electrothermal model generation for gallium nitride (GaN) HEMTs is presented with the consideration of trap deduced gate and drain lag effects.
Abstract: A complete solution from parameter extraction to large-signal electrothermal model generation for gallium nitride (GaN) HEMTs is presented in this paper with the consideration of trapping deduced gate and drain lag effects. The extrinsic parasitic parameters are extracted by multibias hot-FET optimization using artificial bee colony algorithm. New terminal charge ( $Q_{\mathrm {gs}}$ , $Q_{\mathrm {gd}}$ , and $Q_{\mathrm {ds}})$ models with temperature dependence are proposed to better characterize the GaN devices. Physical mechanisms of the electrothermal and trapping effects have been investigated, and the artificial neural network (ANN) is exploited to construct the drain current based on pulsed $I$ – $V$ (PIV) measurements. Besides the instantaneous terminal voltages, additional three auxiliary variables are employed to describe the memory effects of GaN HEMT: channel temperature, gate trapping state, and drain trapping state. These variables are identified from PIVs to compose the input layer of the ANN, while in the simulator, they are captured by the thermal and two envelop tracking subcircuits. These physical auxiliary variables together with the ANN technology enable unlimited fitting sets of PIVs with satisfying accuracy. Single-tone and two-tone on-wafer measurements are conducted for the verification, and a good agreement has been achieved between the measurements and simulations.
TL;DR: In this paper, three different configurations of the secondary coil are investigated placing it inside the titanium case of the pacemaker, on the top surface of the case, or being part of the top-surface case.
Abstract: A wireless power transfer (WPT) system based on magnetic resonant coupling is applied to a pacemaker for recharge its battery. The primary coil is assumed to be on-body, while the secondary coil is in-body. Three different configurations of the secondary coil are hereby investigated placing it inside the titanium case of the pacemaker, on the top surface of the case, or being part of the top surface case. The operational frequency is fixed to be at a relatively low frequency (20 kHz) in order to allow field penetration through the case and to limit the electric and magnetic field safety and thermal increase issues. For each examined configuration, these aspects are investigated by numerical and experimental techniques. The obtained results demonstrate the feasibility of the proposed solutions highlighting their advantages and disadvantages.
TL;DR: In this paper, a 1-V ultra-low power, compact, and wideband low-noise amplifier (LNA) using common-gate (CG) NMOS and PMOS transistors as input devices in a complementary current-reuse structure was proposed.
Abstract: This work presents and analyzes the design of a 1-V ultra-low power, compact, and wideband low-noise amplifier (LNA). The proposed LNA uses common-gate (CG) NMOS and PMOS transistors as input devices in a complementary current-reuse structure. Low power input matching is achieved by employing an active shunt-feedback architecture while the current of the feedback stage is also reused by the input transistor to improve the current efficiency of the LNA. A forward body biasing (FBB) scheme is exploited to tune the feedback coefficient. The complementary characteristics of the input stage leads to partial second-order distortion cancellation. The proposed inductorless LNA is implemented in an IBM 0.13- $\mu {\text {m}}~1$ P8M CMOS technology and occupies only $0.0052~{\text {mm}}^{2}$ . The measured LNA has a 12.3-dB gain 4.9-dB minimum noise figure (NF) input referred third-order intercept point (IIP3) of −10 dBm and 0.1–-2.2 GHz bandwidth (BW), while consuming only 400 $\mu {\text {A}}$ from a 1-V supply.