Showing papers in "IEEE Transactions on Microwave Theory and Techniques in 2013"
TL;DR: In this article, a city-wide RF spectral survey was undertaken from outside all of the 270 London Underground stations at street level, and four harvesters (comprising antenna, impedance-matching network, rectifier, maximum power point tracking interface, and storage element) were designed to cover four frequency bands from the largest RF contributors within the ultrahigh frequency (0.3-3 GHz) part of the frequency spectrum.
Abstract: RF harvesting circuits have been demonstrated for more than 50 years, but only a few have been able to harvest energy from freely available ambient (i.e., non-dedicated) RF sources. In this paper, our objectives were to realize harvester operation at typical ambient RF power levels found within urban and semi-urban environments. To explore the potential for ambient RF energy harvesting, a city-wide RF spectral survey was undertaken from outside all of the 270 London Underground stations at street level. Using the results from this survey, four harvesters (comprising antenna, impedance-matching network, rectifier, maximum power point tracking interface, and storage element) were designed to cover four frequency bands from the largest RF contributors (DTV, GSM900, GSM1800, and 3G) within the ultrahigh frequency (0.3-3 GHz) part of the frequency spectrum. Prototypes were designed and fabricated for each band. The overall end-to-end efficiency of the prototypes using realistic input RF power sources is measured; with our first GSM900 prototype giving an efficiency of 40%. Approximately half of the London Underground stations were found to be suitable locations for harvesting ambient RF energy using our four prototypes. Furthermore, multiband array architectures were designed and fabricated to provide a broader freedom of operation. Finally, an output dc power density comparison was made between all the ambient RF energy harvesters, as well as alternative energy harvesting technologies, and for the first time, it is shown that ambient RF harvesting can be competitive with the other technologies.
778 citations
TL;DR: This paper reviews recent advances in biomedical and healthcare applications of Doppler radar that remotely detects heartbeat and respiration of a human subject and reviews different architectures, baseband signal processing, and system implementations.
Abstract: This paper reviews recent advances in biomedical and healthcare applications of Doppler radar that remotely detects heartbeat and respiration of a human subject. In the last decade, new front-end architectures, baseband signal processing methods, and system-level integrations have been proposed by many researchers in this field to improve the detection accuracy and robustness. The advantages of noncontact detection have drawn interests in various applications, such as energy smart home, baby monitor, cardiopulmonary activity assessment, and tumor tracking. While many of the reported systems were bench-top prototypes for concept verification, several portable systems and integrated radar chips have been demonstrated. This paper reviews different architectures, baseband signal processing, and system implementations. Validations of this technology in a clinical environment will also be discussed.
625 citations
TL;DR: A prototype microwave breast imaging system is used to scan a small group of patients, and several of the resulting images show responses consistent with the clinical patient histories.
Abstract: A prototype microwave breast imaging system is used to scan a small group of patients. The prototype implements a monostatic radar-based approach to microwave imaging and utilizes ultra-wideband signals. Eight patients were successfully scanned, and several of the resulting images show responses consistent with the clinical patient histories. These encouraging results motivate further studies of microwave imaging for breast health assessment.
315 citations
TL;DR: In this paper, the authors designed and fabricated two separate transmit arrays that operate at 77 GHz, one as a quarter-wave plate that transforms a linearly polarized incident wave into a circularly polarized transmitted wave.
Abstract: Two separate transmitarrays that operate at 77 GHz are designed and fabricated. The first transmitarray acts as a quarter-wave plate that transforms a linearly polarized incident wave into a circularly polarized transmitted wave. The second transmitarray acts as both a quarter-wave plate and a beam refracting surface to provide polarization and wavefront control. When the second transmittarray is illuminated with a normally incident, linearly polarized beam, the transmitted field is efficiently refracted to 45 °, and the polarization is converted to circular. The half-power bandwidth was measured to be 17%, and the axial ratio of the transmitted field remained below 2.5 dB over the entire bandwidth. Both designs have a subwavelength thickness of 0.4 mm (λ°/9.7). The developed structures are fabricated with low-cost printed-circuit-board processes on flexible substrates. The transmitarrays are realized by cascading three patterned metallic surfaces (sheet admittances) to achieve complete phase control, while maintaining high transmission. Polarization conversion is accomplished with anisotropic sheets that independently control the field polarized along the two orthogonal axes. The structures are analyzed with both circuit- and fields-based approaches.
305 citations
TL;DR: In this paper, a microwave resonator is presented as a microfabricated sensor dedicated to liquid characterization with perspectives for chemistry and biology, where the nanolitter range aqueous solution under investigation is located on top of the planar resonator thanks to a microfluidic channel compatible with a future lab-on-a-chip integration.
Abstract: A microwave resonator is presented as a microfabricated sensor dedicated to liquid characterization with perspectives for chemistry and biology. The nanolitter range aqueous solution under investigation is located on top of the planar resonator thanks to a microfluidic channel compatible with a future lab-on-a-chip integration. The interaction between the electric field and the liquid translates into a predictable relationship between electrical characteristics of the resonator (resonant frequency and associated insertion loss) and the complex permittivity of the fluid (real and imaginary parts). A prototype of the resonator has been fabricated and evaluated with de-ionized water/ethanol mixtures with ethanol volume fraction ranging from 0% to 20%. Good agreement has been reached between theoretical and measured electrical parameters of the resonator. The discrepancy on the resonant frequency is estimated to 0.5%, whereas the one on the associated transmission coefficient is lower than 1%. This translates into a maximum relative error on the real and imaginary part of the predicted relative permittivity of less than 6.5% and 4%, respectively, validating the principle of this accurate permittivity characterization methodology.
269 citations
TL;DR: In this paper, a new type of microresonators enabled by micromachining of ion sliced X -cut LiNbO3 thin films is reported, which has a high electromechanical coupling (kt2) of 11.5%.
Abstract: This paper reports on a new type of microresonators enabled by micromachining of ion sliced X -cut LiNbO3 thin films. In operation, the device is excited into lateral vibrations, thus allowing the center frequency to be determined by the lithographically defined dimensions of the excitation electrodes. The demonstrated device has a high electromechanical coupling (kt2) of 11.5%-the highest attained for laterally vibrating microelectromechanical systems resonators. Device orientation was also varied to investigate its impact on kt2 and experimental data have shown good agreement with theoretical predictions. Several key performance parameters, including the quality factor (Q), the static capacitance, C0 , the temperature coefficient of frequency (TCF), and the power handling, are also characterized and the related experimental data are presented. The devices demonstrate Q 's up to 1800. The measured TCFs range from -55 to -69 ppm/K and can be considered sufficiently low for wideband RF filtering. The high electromechanical coupling and the high Q of this new class of devices show promise for the implementation of multifrequency wideband multiplexers and filter banks for reconfigurable RF front-ends.
245 citations
TL;DR: In this paper, a Debye relaxation model for the permittivity of aqueous glucose solution is given up to 40 GHz, which is compared with invasive measurements on over 40 blood samples.
Abstract: A Debye relaxation model for the permittivity of aqueous glucose solution is given up to 40 GHz. Measurements of aqueous solutions are compared with invasive measurements on over 40 blood samples. Reflection- and transmission-based techniques are explained, concerning the application in biomedical concentration measurements. Wideband measurements on different sensing structures are introduced. Reflection- and transmission-based sensors are applied to a six-port reflectometer, as well as a homodyne vector network analyzer.
233 citations
TL;DR: In this paper, stacked field effect transistor (FET) CMOS millimeter-wave power amplfiers (PAs) are studied with a focus on design of appropriate complex impedances between the transistors.
Abstract: Stacked field-effect transistor (FET) CMOS millimeter-wave power amplfiers (PAs) are studied with a focus on design of appropriate complex impedances between the transistors. The stacking of multiple FETs allows increasing the supply voltage, which, in turn, allows higher output power and a broader bandwidth output matching network. Different matching techniques for the intermediate nodes are analyzed and used in two-, three-, and four-stack single-stage $Q$ -band CMOS PAs. A four-stack amplifier design achieves a saturated output power greater than 21 dBm while achieving a maximum power-added efficiency (PAE) greater than 20% from 38 to 47 GHz. The effectiveness of an inductive tuning technique is demonstrated in measurement, improving the PAE from 26% to 32% in a two-stack PA design. The input and output matching networks are designed using on-chip shielded coplanar waveguide transmission lines, as well as metal finger capacitors. The amplifiers were implemented in a 45-nm CMOS silicon-on-insulator process. Each of the amplifiers occupies an area of 600 $\mu$ m $\,\times\,$ 500 $\mu$ m including pads.
232 citations
TL;DR: In this article, a power divider with two bandpass filters is presented, where the isolation elements are loaded at the filters' open ends to get a good isolation between the output ports.
Abstract: This paper presents a novel device integrating a power divider with two bandpass filters. It is capable of splitting power and selecting frequency at the same time. The phase shift of the filter is found to be ±90° at the center frequency. Therefore, when it is matched to 70.7 Ω, it can replace the conventional quarter-wave length transmission line in the power divider. The isolation elements are loaded at the filters' open ends to get a good isolation between the output ports. As a result, both the transmission and isolation property are satisfied. The equivalent even- and odd-mode circuits of the proposed structure are analyzed and design equations are derived. They are used to guide the design of the devices. For demonstration, filter-integrated power dividers with single- and dual-band operation are implemented, respectively. Comparisons of the measured and simulated results are presented to verify the theoretical predications.
208 citations
TL;DR: In this paper, a chipless RF identification based on a multiresonant high-impedance surface is proposed, which performs deep absorptions of the impinging signal at several resonant frequencies related to the loop resonators.
Abstract: A novel chipless RF identification based on a multiresonant high-impedance surface is proposed. The structure is based on a finite metallic frequency-selective surface (FSS) comprising 2 × 2 (30 mm × 30 mm) or 3 × 3 (45 mm × 45 mm) unit cells. The FSS unit cell is formed by several concentric square loop resonators. The thin structure performs deep absorptions of the impinging signal at several resonant frequencies related to the loop resonators. If one of the printed loops in the unit cell is removed, the corresponding absorption peak disappears from the reflected signal giving the possibility of encoding a desired bit sequence. The proposed structure exhibits some intrinsic advantages, such as scalability (bit number increase) without any size increase, polarization independence, large read range, and the capability of operating when mounted on metallic objects. A transmission line model is employed to illustrate the operation principle of the structure, whereas measurements on realized prototypes are provided to assess the reliability and effectiveness of the proposed design.
191 citations
TL;DR: In this paper, a new chipless RF identification (RFID) tag design is presented to ease the detection of items in a real environment, where multiple scatterers are able to depolarize the incident wave to create a response in the orthogonal polarization.
Abstract: A new chipless RF identification (RFID) tag design is presented in this paper to ease the detection of items in a real environment. For this purpose, we present multiple scatterers able to depolarize the incident wave to create a response in the orthogonal polarization. Measurements in anechoic chamber and in a real environment, when the tags are positioned on dielectric and metal objects, show their higher detection capability. For the first time, a study on the technique to increase the detection area with a simplified calibration step is carried out. This makes possible the detection of the tag on objects of various sizes and compositions, which is required in the majority of RFID applications.
TL;DR: A unique embedded wireless energy-harvesting prototype (E-WEHP) that exploits the unique makeup of ambient digital-TV signals, and scavenges wireless power from them at distance of over 6.3 km from the TV broadcast source.
Abstract: The use of digital television broadcasting standards has resulted in transmission of perpetually on wireless digital-TV signals over the air at wider bandwidths in ultrahigh-frequency bands for high-definition video and audio broadcasts to TV and smart phones. This paper presents a unique embedded wireless energy-harvesting prototype (E-WEHP) that exploits the unique makeup of ambient digital-TV signals, and scavenges wireless power from them at distance of over 6.3 km from the TV broadcast source. The harvested wireless power is successfully used to power and sustain a 16-bit embedded microcontroller for sensing and machine-to-machine applications without the use of batteries. The E-WEHP uses a miniaturized planar log-periodic antenna and RF-dc charge-pump circuit with maximum sensitivities of - 14.6 and -18.86 dBm and an embedded firmware-based power management scheme to power microcontroller peripherals from different types of ambient digital-TV signals.
TL;DR: In this paper, the authors focused on the analysis of coplanar waveguides (CPWs) loaded with circularly shaped electric-LC (ELC) resonators, the latter consisting of two coplanars connected in parallel through a common gap.
Abstract: This paper is focused on the analysis of coplanar waveguides (CPWs) loaded with circularly shaped electric-LC (ELC) resonators, the latter consisting of two coplanar loops connected in parallel through a common gap. Specifically, the resonator axis is aligned with the CPW axis, and a dynamic loading with ELC rotation is considered. Since the ELC resonator is bisymmetric, i.e., it exhibits two orthogonal symmetry planes, the angular orientation range is limited to 90°. It is shown that the transmission and reflection coefficients of the structure depend on the angular orientation of the ELC. In particular, the loaded CPW behaves as a transmission line-type (i.e., all-pass) structure for a certain ELC orientation (0°) since the resonator is not excited. However, by rotating the ELC, magnetic coupling to the line arises, and a notch in the transmission coefficient (with orientation dependent depth and bandwidth) appears. This feature is exploited to implement angular displacement sensors by measuring the notch depth in the transmission coefficient. To gain more insight on sensor design, the lumped element equivalent-circuit model for ELC-loaded CPWs with arbitrary ELC orientation is proposed and validated. Based on this approach, a prototype displacement sensor is designed and characterized. It is shown that by introducing additional elements (a circulator and an envelope detector), novel and high precision angular velocity sensors can also be implemented. An angular velocity sensor is thus proposed, characterized, and satisfactorily validated. The proposed solution for angular sensing is robust against environmental variations since it is based on the geometrical alignment/misalignment between the symmetry planes of the coupled elements.
TL;DR: The recent advances of microwave-based and millimeter-wave-based dielectric spectroscopy performed at the cellular and molecular levels is progressively emerging, as it permits the non-invasive and real-time probing of cells in their culture biological medium.
Abstract: Cancer remains a leading cause of death in the world. To overcome this problem, it is necessary to develop new analysis tools, in complementarity to existing ones, to enable the early diagnostic of the diseases, personalized treatment, and further fundamental cancer mechanisms understanding. In this context, microwave-based and millimeter-wave-based dielectric spectroscopy performed at the cellular and molecular levels is progressively emerging, as it permits the non-invasive and real-time probing of cells in their culture biological medium. The recent advances of this topic are given in this paper with a specific highlight of its various assets.
TL;DR: For the first time, radar, wireless communications, and data processing techniques are combined, enabling contactless fall detection and tagless localization and demonstrates an adequate detection of the target's absolute distance.
Abstract: Innovative technology approaches have been increasingly investigated for the last two decades aiming at human-being long-term monitoring. However, current solutions suffer from critical limitations. In this paper, a complete system for contactless health-monitoring in home environment is presented. For the first time, radar, wireless communications, and data processing techniques are combined, enabling contactless fall detection and tagless localization. Practical limitations are considered and properly dealt with. Experimental tests, conducted with human volunteers in a realistic room setting, demonstrate an adequate detection of the target's absolute distance and a success rate of 94.3% in distinguishing fall events from normal movements. The volunteers were free to move about the whole room with no constraints in their movements.
TL;DR: It is theoretically shown that the proposed amplifier can simultaneously provide high efficiency at both full output power and at output power back-off, over a much improved bandwidth compared to the conventional Doherty power amplifier.
Abstract: This paper derives the theory and presents measurements of a new power amplifier based on the Doherty power amplifier topology. It is theoretically shown that the proposed amplifier can simultaneously provide high efficiency at both full output power and at output power back-off, over a much improved bandwidth compared to the conventional Doherty power amplifier. It is also shown that the proposed amplifier allows reconfiguration of the efficiency in power back-off without the need of tunable elements.
TL;DR: In this article, a 57-64 GHz low phase error 5-bit switch-type phase shifter integrated with a low phase-variation variable gain amplifier (VGA) is implemented through TSMC 90-nm CMOS low power technology.
Abstract: A 57-64-GHz low phase-error 5-bit switch-type phase shifter integrated with a low phase-variation variable gain amplifier (VGA) is implemented through TSMC 90-nm CMOS low-power technology. Using the phase compensation technique, the proposed VGA can provide appropriate gain tuning with almost constant phase characteristics, thus greatly reducing the phase-tuning complexity in a phased-array system. The measured root mean square (rms) phase error of the 5-bit phase shifter is 2° at 62 GHz. The phase shifter has a low group-delay deviation (phase distortion) of +/- 8.5 ps and an excellent insertion loss flatness of ±0.8 dB for a specific phase-shifting state, across 57-64 GHz. For all 32 states, the insertion loss is 14.6 ± 3 dB, including pad loss at 60 GHz. For the integrated phase shifter and VGA, the VGA can provide 6.2-dB gain tuning range, which is wide enough to cover the loss variation of the phase shifter, with only 1.86° phase variation. The measured rms phase error of the 5-bit phase shifter and VGA is 3.8° at 63 GHz. The insertion loss of all 32 states is 5.4 dB, including pad loss at 60 GHz, and the loss flatness is ±0.8 dB over 57-64 GHz. To the best of our knowledge, the 5-bit phase shifter presents the best rms phase error at center frequency among the V-band switch-type phase shifter.
TL;DR: In this article, the applicability of magnetless non-reciprocal metamaterial (MNM) technology to non-rewarding microwave components is investigated. And the authors present the first extensive investigation of the application of MNM technology to microwave components, including a microstrip-ring configuration, an isolator and a circulator.
Abstract: A magnetless nonreciprocal metamaterial (MNM), consisting of traveling-wave resonant ring particles loaded by transistor and exhibiting the gyromagnetic properties as ferrites, without their size, weight, cost, and monolithic microwave integrated circuit incompatibility drawbacks, was recently introduced in 2011 by Kodera et al. This paper presents the first extensive investigation of the applicability of MNM technology to nonreciprocal microwave components. It recalls the key principle of the MNM, provides basic MNM design guidelines, explains coupling mechanism between a microstrip line and MNM rings, and demonstrates two nonreciprocal MNM components based on a microstrip-ring configuration, an isolator, and a circulator. Although these components have not been fully optimized, they already exhibit attractive performance and provide a proof-of-concept that MNM technology has a potential for microwave nonreciprocal microwave components with substantial benefits compared to their ferrite and active-circuit counterparts.
TL;DR: In this paper, a monostatic radar based on a six-port interferometer operating a continuous-wave signal at 24 GHz and a radiated power of less than 3 GHz is presented.
Abstract: A novel remote respiration and heartbeat monitoring sensor is presented The device is a monostatic radar based on a six-port interferometer operating a continuous-wave signal at 24 GHz and a radiated power of less than 3 $\mu\hbox{W}$ Minor mechanical movements of the patient's body caused by the respiration as well as hearbeat can be tracked by analyzing the phase modulation of the backscattered signal by means of microwave interferometry with the six-port network High-distance measurement accuracy in the micrometer scale as well as low system complexity are the benefits of the six-port receiver To verify the performance of the system, different body areas have been observed by the six-port radar The proposed system has been tested and validated by measurement results
Journal Article•
TL;DR: In this paper, the authors presented a reconfigurable antenna capable of independently reconfiguring the operating frequency, radiation pattern and polarization, using a switched grid of small metallic patches known as pixel surface as a parasitic layer to provide reconfiguration capabilities to existing antennas acting as driven element.
Abstract: This communication presents a reconfigurable antenna capable of independently reconfiguring the operating frequency, radiation pattern and polarization A switched grid of small metallic patches, known as pixel surface, is used as a parasitic layer to provide reconfiguration capabilities to existing antennas acting as driven element The parasitic pixel layer presents advantages such as low profile, integrability and cost-effective fabrication A fully operational prototype has been designed, fabricated and its compound reconfiguration capabilities have been characterized The prototype combines a patch antenna and a parasitic pixel surface consisting of 6 $\,\times\,$ 6 pixels, with an overall size of $06 \lambda \times 06 \lambda$ and 60 PIN-diode switches The antenna simultaneously tunes its operation frequency over a 25% frequency range, steers the radiation beam over ${\pm 30^\circ}$ in E and H-planes, and switches between four different polarizations ( ${\mathhat{\rm x}},$ ${\mathhat{\rm y}}$ , LHCP, RHCP) The average antenna gain among the different parameter combinations is 4 dB, reaching 6–7 dB for the most advantageous combinations The distance between the driven and the parasitic layers determines the tradeoff between frequency tuning range (12% to 25%) and radiation efficiency (45% to 55%)
TL;DR: The breathing signals of male humans and a seven-week-old infant are presented, qualifying the IR-UWB radar principle as a useful tool for breath-rate determination.
Abstract: In this paper an impulse-radio ultra-wideband (IR-UWB) hardware demonstrator is presented, which can be used as a radar sensor for highly precise object tracking and breath-rate sensing. The hardware consists of an impulse generator integrated circuit (IC) in the transmitter and a correlator IC with an integrating baseband circuit as correlation receiver. The radiated impulse is close to a fifth Gaussian derivative impulse with $\sigma=51\ {\hbox {ps}}$ , efficiently using the Federal Communications Commission indoor mask. A detailed evaluation of the hardware is given. For the tracking, an impulse train is radiated by the transmitter, and the reflections of objects in front of the sensor are collected by the receiver. With the reflected signals, a continuous hardware correlation is computed by a sweeping impulse correlation. The correlation is applied to avoid sampling of the RF impulse with picosecond precision. To localize objects precisely in front of the sensor, three impulse tracking methods are compared: Tracking of the maximum impulse peak, tracking of the impulse slope, and a slope-to-slope tracking of the object's reflection and the signal of the static direct coupling between transmit and receive antenna; the slope-to-slope tracking showing the best performance. The precision of the sensor is shown by a measurement with a metal plate of 1-mm sinusoidal deviation, which is clearly resolved. Further measurements verify the use of the demonstrated principle as a breathing sensor. The breathing signals of male humans and a seven-week-old infant are presented, qualifying the IR-UWB radar principle as a useful tool for breath-rate determination.
TL;DR: A low-power and high data-rate fully integrated 60-GHz on-off keying (OOK) transceiver for short-range wireless communication is demonstrated and achieves energy efficiency of 6.26 pJ/bit.
Abstract: A low-power and high data-rate fully integrated 60-GHz on-off keying (OOK) transceiver for short-range wireless communication is demonstrated. The transceiver consists of a switch, transmitter, and receiver and uses OOK modulation for a compact and low-power design. With a highly efficient Tx, high-speed modulator/demodulator, and wideband characteristic, the transceiver has low-power and high data-rate capability. Implemented in 90-nm CMOS technology, the transmitter and the receiver consume 31 and 36 mW at 10.7 Gb/s and occupy an active footprint of 0.15 and 0.29 mm2, respectively. The transceiver with an on-board Yagi-Uda antenna achieves 10.7-Gb/s wireless OOK data transmission over 10 cm at a bit-error rate of less than 10-12 for 27 -1 pseudorandom binary sequence. As a result, the proposed transceiver achieves energy efficiency of 6.26 pJ/bit.
TL;DR: In this article, an open stub-loaded shorted stepped-impedance resonator (OSLSSIR) with two identical open stubs loaded at its impedance junctions is proposed.
Abstract: This paper presents a new class of dual-, tri- and quad-band BPF by using proposed open stub-loaded shorted stepped-impedance resonator (OSLSSIR). The OSLSSIR consists of a two-end-shorted three-section stepped-impedance resistor (SIR) with two identical open stubs loaded at its impedance junctions. Two 50- Ω tapped lines are directly connected to two shorted sections of the SIR to serve as I/O ports. As the electrical lengths of two identical open stubs increase, many more transmission poles (TPs) and transmission zeros (TZs) can be shifted or excited within the interested frequency range. The TZs introduced by open stubs divide the TPs into multiple groups, which can be applied to design a multiple-band bandpass filter (BPF). In order to increase many more design freedoms for tuning filter performance, a high-impedance open stub and the narrow/broad side coupling are introduced as perturbations in all filters design, which can tune the even- and odd-mode TPs separately. In addition, two branches of I/O coupling and open stub-loaded shorted microstrip line are employed in tri- and quad-band BPF design. As examples, two dual-wideband BPFs, one tri-band BPF, and one quad-band BPF have been successfully developed. The fabricated four BPFs have merits of compact sizes, low insertion losses, and high band-to-band isolations. The measured results are in good agreement with the full-wave simulated results.
TL;DR: In this article, the first flip-chip-packaged and fully integrated Doppler micro-radar in 90-nm CMOS for noncontact vital-sign and vibration detection is presented.
Abstract: This paper presents the first flip-chip-packaged and fully integrated Doppler micro-radar in 90-nm CMOS for noncontact vital-sign and vibration detection. The use of a smaller wavelength compared with previous works achieves the highly compact system for portable devices, and the radar design considerations at 60 GHz are discussed from both system and circuits points of view. The compact 60-GHz core (0.73 $\hbox{mm}^{2}$ ) provides a 36-dB peak down-conversion gain and transmits a radar signal around 0 dBm at 55 GHz. Quadrature generation at the intermediate frequency stage of the heterodyne receiver gives a power- and area-efficient solution to the null detection point issue, ensuring robust detection. By using single-patch antennas and without a high-power amplifier, the system demonstrates the first-pass success of human vital-sign detection at 0.3 m. The small mechanical vibration with a displacement of 0.2 mm can be detected up to 2 m away. At 60 GHz, target displacement comparable to wavelength results in strong nonlinear phase modulation and increases detection difficulties. A signal-recovery algorithm is proposed to improve the accuracy of vital-sign detection.
TL;DR: In this paper, a 32-element symmetrical TX/RX 60 GHz RF integrated circuit (RFIC) with built-in self-test is presented, which achieves record size and power consumption.
Abstract: Fully integrated 32-element symmetrical TX/RX 60-GHz RF integrated circuit (RFIC) with built-in self-test is presented. The RF bidirectional power-combining architecture with shared blocks and less than 1-dB millimeter-wave transmit/receive (T/R) switch loss achieves record size and power consumption. The RFIC features an 8-dB noise figure and - 28-dBm IP1 dB in RX mode, 10-dB power gain, and Psat of +3.5 dBm per chain in TX mode. Further included are a 2-bit phase shifter, an IF converter to/from 12 GHz, and an integrated frac-N synthesizer with push-push voltage-controlled oscillator having a-93 dBc@1-MHz phase noise at 48-GHz local oscillator port. A novel high dynamic range phase and power detector is presented with 2° and ±1-dB accuracy over PVT in phase and power. A detailed analysis of both phase quantization and power distribution is presented. Array impairments such as mismatch and coupling were compared for different topologies. The RFIC is packaged on alumina for testing and on low-temperature co-fired ceramic (LTCC) for antenna integration. The 6 × 6 patch antenna on LTCC including four dummies achieves a gain of 19 dBi with scanning of ± 30°. The total root mean square amplitude and phase error of the array is 0.8 dB and 6° , respectively, resulting in a maximum array beam degradation of 1.4 dB for 2-bit quantization. The RFIC area is 29 mm2 and it consumes 1.2 W/0.85 W at TX/RX, with a 29-dBm effective isotropic radiated power at -19-dB error vector magnitude.
TL;DR: In this article, a dual-band bandpass filter with independently tunable passband center frequencies and bandwidths is proposed, which is realized using a varactor-loaded transmission line dual-mode resonator.
Abstract: This paper presents a novel approach to the design of tunable dual-band bandpass filter (BPF) with independently tunable passband center frequencies and bandwidths. The newly proposed dual-band filter principally comprises two dual-mode single band filters using common input/output lines. Each single BPF is realized using a varactor-loaded transmission-line dual-mode resonator. The proposed filter also offers switchable characteristics to select either of the passbands (either the first or the second passband only). To suppress the harmonics over a broad bandwidth, defected ground structures are used at input/output feeding lines without degrading the passbands characteristics. From the experimental results, it was found that the proposed filter exhibited the first passband center frequency tunable range from 1.48 to 1.8 GHz with a 3-dB fractional bandwidth (FBW) variation from 5.76% to 8.55% and the second passband center frequency tunable range from 2.40 to 2.88 GHz with the 3-dB FBW variation from 8.28% to 12.42%. The measured harmonic results of the proposed filters showed a rejection level of 19 dB, which is up to more than ten times of the highest center frequency of the first passband without degradation of the passbands.
TL;DR: This paper proposes a novel two-dimensional modified memory polynomial (2D-MMP) technique to compensate for nonlinear distortion in the concurrent dual-band transmitters to achieve nearly the same linearization accuracy compared to the prior 2D-DPD model.
Abstract: Cross-band modulation effects in the concurrent dual-band transmitters are quite noticeable for the linearization. This paper proposes a novel two-dimensional modified memory polynomial (2D-MMP) technique to compensate for nonlinear distortion in the concurrent dual-band transmitters. By taking into account the cross-band modulation effects, the 2D-MMP model is developed by properly modifying the envelope terms of the conventional memory polynomial (MP) model. This makes the model complexity of the 2D-MMP model significantly reduced compared to the prior 2D-DPD model in previous work. However, the linearization ability of the 2D-MMP model is still retained. Simulations prove that the 2D-MMP model is quite robust to different PA models. Experimental measurements were carried out for a dual-band class-AB PA exhibiting mild nonlinearity and a highly nonlinear dual-band Doherty PA. The results show that the 2D-MMP model can achieve nearly the same linearization accuracy compared to the 2D-DPD model, with much less coefficients. Less than -52 dBc adjacent channel power ratios (ACPRs) for the dual-band class-AB power amplifiers (PAs) and -50 dBc ACPRs for the dual-band Doherty PA in the dual bands were achieved.
TL;DR: The experimental results show that the proposed radar system is effective to relieve the linearity burden of the baseband circuit and help compensate the RBM and that larger body movement does not necessarily mean larger radar baseband output.
Abstract: This paper presents a Doppler radar vital sign detection system with random body movement cancellation (RBMC) technique based on adaptive phase compensation. An ordinary camera was integrated with the system to measure the subject's random body movement (RBM) that is fed back as phase information to the radar system for RBMC. The linearity of the radar system, which is strictly related to the circuit saturation problem in noncontact vital sign detection, has been thoroughly analyzed and discussed. It shows that larger body movement does not necessarily mean larger radar baseband output. High gain configuration at baseband is required for acceptable SNR in noncontact vital sign detection. The phase compensation at radar RF front-end helps to relieve the high-gain baseband from potential saturation in the presence of large body movement. A simple video processing algorithm was presented to extract the RBM without using any marker. Both theoretical analysis and simulation have been carried out to validate the linearity analysis and the proposed RBMC technique. Two experiments were carried out in the lab environment. One is the phase compensation at RF front end to extract a phantom motion in the presence of another large shaker motion, and the other one is to measure the subject person breathing normally but randomly moving his body back and forth. The experimental results show that the proposed radar system is effective to relieve the linearity burden of the baseband circuit and help compensate the RBM.
TL;DR: In this article, the authors present a linear multi-harmonic analysis method to evaluate the performance of digitally controlled dual RF-input power amplifiers (PAs) in a complex design space involving two independent inputs.
Abstract: This paper presents a linear multi-harmonic analysis method to evaluate the performance of digitally controlled dual RF-input power amplifiers (PAs). The method enables, due to its low computational cost, optimization of PA efficiency and bandwidth in a complex design space involving two independent inputs. Under the idealized assumption of short-circuited higher harmonics, the analysis is used to prove the existence of a Doherty-outphasing continuum, featuring high average efficiency over 100% fractional bandwidth. With this result as a foundation, a combiner incorporating microwave transistor parasitics is analyzed without assuming short-circuited higher harmonics, showing that high average efficiencies are also achievable under more realistic conditions. A PA is straightforwardly designed from these calculation results using two 15-W GaN HEMTs. The simulated layout-ready (large-signal transistor model) PA average drain efficiency exceeds 50% over 1.1-3.7 GHz for a 6.7-dB peak-to-average power-ratio WCDMA signal. The measured PA has a maximum output power of 44 ±0.9 dBm and a 6-dB output power back-off (OPBO) power-added efficiency (PAE) of 45% over 1-3 GHz. After applying digital pre-distortion, excellent linearity is demonstrated when transmitting the WCDMA signal, resulting in an adjacent channel leakage power ratio lower than -57 dBc with corresponding average PAE of 50% and 40% at 1.2 and 2.3 GHz, respectively. This is, to the authors' knowledge, the most wideband OPBO efficiency enhanced PA reported to date, proving the effectiveness of employing linear multi-harmonic analysis in dual-input PA design.
TL;DR: In this paper, a Wilkinson power divider on a single-layer microstrip line that can reduce the occupied area, suppress the harmonic components, and/or provide the arbitrary power division ratios is described.
Abstract: This paper describes a new Wilkinson power divider on a single-layer microstrip line that can reduce the occupied area, suppress the harmonic components, and/or provide the arbitrary power division ratios. It consists of two-section transmission lines, two inductors, and one isolation resistor. Four different designs have been conducted to investigate the capabilities of the structure. In addition, a compact divider along with harmonic suppression and a practical divider with a large power-dividing ratio has been constructed and measured. The simulation and measurement results are in good agreement with each other. This indicates that the structure can effectively be used as a power divider for miniaturized or arbitrary power division ratio applications.