Showing papers on "RF power amplifier published in 2018"

A 28-GHz CMOS Direct Conversion Transceiver With Packaged $2 \times 4$ Antenna Array for 5G Cellular System

Abstract: This paper describes a 28-GHz CMOS direct conversion transceiver with packaged $2 \times 4$ patch antenna array for 5G communication. Beamforming antenna and reconfigurable transceiver architecture are used for high effective isotropic radiated power (EIRP). For low error vector magnitude (EVM), switchless matching transmitter (Tx)/receiver (Rx) to antenna and 28-GHz injection-locked local oscillator (LO) generator are employed. Test chip was fabricated in 28-nm RF CMOS process. Measurement results show Tx EIRPsat of 31.5 dBm ( $P_{\mathrm {sat}}$ of 10.5 dBm in one power amplifier (PA)), EIRPmax 24 dBm ( $P_{\mathrm {max}}$ of 2 dBm with backoff of 7.5 dB in one PA), Rx noise figure of 6.7 dB, and integrated LO phase noise of −38.7 dBc (0.67°). After IQ mismatch calibration, Tx LO leakage and image power are less than −35 dBc. Rx and Tx EVM show 2.2% (−33 dB) at medium RF power (Rx $P_{\mathrm {in}}$ of −60 dBm and Tx EIRP of 0 dBm) with well-fit beam control capability.

Multiport Pixel Rectenna for Ambient RF Energy Harvesting

Abstract: We describe the design of a multiport pixel rectenna for ambient radio-frequency (RF) energy harvesting consisting of an optimized triple-port pixel antenna and a triple-port rectifier with dc combining. The advantages of the multiport pixel approach include enhanced harvested RF power for a given area as well as a reduction in the antenna matching requirements. We formulate the design of the triple-port pixel antenna as a binary optimization problem with an objective function related to harvested RF power in the GSM-1800 band for specified power angular spectrums without the need for antenna matching components. The optimization of the triple-port pixel antenna is obtained by using successive exhaustive Boolean optimization. The design for the triple-port rectifier with dc combining is also provided and a prototype is demonstrated. The rectenna measurement demonstrates that the proposed triple-port pixel antenna has dc output power over double that of single-port-based antennas of similar size. The overall RF-to-dc efficiency of the multiport pixel rectenna is also evaluated and shown to be 19% when the total input RF power is −20 dBm. The effects of nonuniformity in the input RF power across antenna ports are also investigated.

RF coils: A practical guide for nonphysicists

Abstract: Radiofrequency (RF) coils are an essential MRI hardware component. They directly impact the spatial and temporal resolution, sensitivity, and uniformity in MRI. Advances in RF hardware have resulted in a variety of designs optimized for specific clinical applications. RF coils are the “antennas” of the MRI system and have two functions: first, to excite the magnetization by broadcasting the RF power (Tx‐Coil) and second to receive the signal from the excited spins (Rx‐Coil). Transmit RF Coils emit magnetic field pulses ( B1+) to rotate the net magnetization away from its alignment with the main magnetic field (B0), resulting in a transverse precessing magnetization. Due to the precession around the static main magnetic field, the magnetic flux in the receive RF Coil ( B1−) changes, which generates a current I. This signal is “picked‐up” by an antenna and preamplified, usually mixed down to a lower frequency, digitized, and processed by a computer to finally reconstruct an image or a spectrum. Transmit and receive functionality can be combined in one RF Coil (Tx/Rx Coils). This review looks at the fundamental principles of an MRI RF coil from the perspective of clinicians and MR technicians and summarizes the current advances and developments in technology. Level of Evidence: 1 Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2018;48:590–604.

A Flexible 2.45-GHz Power Harvesting Wristband With Net System Output From −24.3 dBm of RF Power

Abstract: This paper presents a flexible 2.45-GHz wireless power harvesting wristband that generates a net dc output from a −24.3-dBm RF input. This is the lowest reported system sensitivity for systems comprising a rectenna and impedance-matching power management. A complete system has been implemented comprising: a fabric antenna, a rectifier on rigid substrate, a contactless electrical connection between rigid and flexible subsystems, and power electronics impedance matching. Various fabric and flexible materials are electrically characterized at 2.45 GHz using the two-line and the T-resonator methods. Selected materials are used to design an all-textile antenna, which demonstrates a radiation efficiency above 62% on a phantom irrespective of location, and a stable radiation pattern. The rectifier, designed on a rigid substrate, shows a best-in-class efficiency of 33.6% at −20 dBm. A reliable, efficient, and wideband contactless connection between the fabric antenna and the rectifier is created using broadside-coupled microstrip lines, with an insertion loss below 1 dB from 1.8 to over 10 GHz. A self-powered boost converter with a quiescent current of 150 nA matches the rectenna output with a matching efficiency above 95%. The maximum end-to-end efficiency is 28.7% at −7 dBm. The wristband harvester demonstrates net positive energy harvesting from −24.3 dBm, a 7.3-dB improvement on the state of the art.

Design of an 87% Fractional Bandwidth Doherty Power Amplifier Supported by a Simplified Bandwidth Estimation Method

Abstract: This paper presents a novel technique for the design of broadband Doherty power amplifiers (DPAs), supported by a simplified approach for the initial bandwidth estimation that requires linear simulations only. The equivalent impedance of the Doherty inverter is determined by the value of the output capacitance of the power device, and the Doherty combiner is designed following this initial choice and using a microstrip network. A GaN-based single-input DPA designed adopting this method exhibits, on a state-of-the-art bandwidth of 87% (1.5–3.8 GHz), a measured output power of around 20 W with 6 dB back-off efficiency between 33% and 55%, with a gain higher than 10 dB. System-level measurements prove the linearizability of the designed Doherty amplifier when a modulated signal is applied.

A Load Modulated Balanced Amplifier for Telecom Applications

Abstract: This paper presents the design and characterization of a load modulated balanced amplifier for telecom base station applications adopting a novel mode of operation. The theory of operation is described explaining the main differences compared to Doherty amplifiers, in particular the RF bandwidth advantages and, on the other hand, the intrinsic nonlinear behavior. The specific design strategy that adopts prematching for back-off broadband matching is explained in detail. A prototype, based on 25-W GaN packaged devices, has been fabricated and measured with single tone CW and modulated signal stimulus. For CW conditions, on the 1.7–2.5-GHz band, the peak output power is between 63 and 78 W, with power added efficiency higher than 48%, 43%, and 39% at saturation, 6- and 8-dB output power back-off, respectively. With a modulated signal for Long Term Evolution the amplifier provides an average output power of around 10 W, with efficiency higher than 40%, and can be linearized by adopting a low complexity predistorter. If compared to previously published power amplifiers targeting similar power and bandwidth, the measurement shows very good performance, demonstrating the potential of this novel technique in the field of efficiency enhanced transmitters.

1.032-Tb/s CPRI-Equivalent Rate IF-Over-Fiber Transmission Using a Parallel IM/PM Transmitter for High-Capacity Mobile Fronthaul Links

Abstract: We report high-capacity intermediate-frequency-over-fiber (IFoF) transmission using parallel intensity/phase modulators (IM/PM). Thanks to the parallel IM/PM transmitter, we can avoid all the null frequencies caused by dispersion-induced RF power fading. Compared to other techniques to avoid RF power fading, the parallel IM/PM transmitter offers a simple solution because it does not rely on any sophisticated digital signal processing. We transmitted 14 $\times$ 1.2-GHz orthogonal-frequency-division-multiplexed signals over a 20-km single-mode fiber using the parallel IM/PM transmitter and achieved a Common Public Radio Interface equivalent data rate of 1.032 Tb/s. Thus, an IFoF system with the parallel IM/PM transmitter shows great potential to be applied to high-capacity mobile fronthaul links in the upcoming fifth-generation mobile system and beyond.

Energy Harvesting Using a Low-Cost Rectenna for Internet of Things (IoT) Applications

Abstract: Traditionally employed human-to-human and human-to-machine communication has recently been replaced by a new trend known as the Internet of things (IoT). IoT enables device-to-device communication without any human intervention, hence, offers many challenges. In this paradigm, machine’s self-sustainability due to limited energy capabilities presents a great challenge. Therefore, this paper proposed a low-cost energy harvesting device using rectenna to mitigate the problem in the areas where battery constraint issues arise. So, an energy harvester is designed, optimized, fabricated, and characterized for energy harvesting and IoT applications which simply recycles radio-frequency (RF) energy at 2.4 GHz, from nearby Wi-Fi/WLAN devices and converts them to useful dc power. The physical model comprises of antenna, filters, rectifier, and so on. A rectangular patch antenna is designed and optimized to resonate at 2.4 GHz using the well-known transmission-line model while the band-pass and low-pass filters are designed using lumped components. Schottky diode (HSMS-2820) is used for rectification. The circuit is designed and fabricated using the low-cost FR4 substrate ( ${h}$ = 16 mm and $\varepsilon _{r} = 4.6$ ) having the fabricated dimensions of 285 mm $\times \,\,90$ mm. Universal software radio peripheral and GNU Radio are employed to measure the received RF power, while similar measurements are carried out using R&S spectrum analyzer for validation. The received measured power is −64.4 dBm at the output port of the rectenna circuit. Hence, our design enables a pervasive deployment of self-operable next-generation IoT devices.

Design of Ultrawideband High-Efficiency Extended Continuous Class-F Power Amplifier

Abstract: Total bandwidth of existing wireless communication technologies covers a wide frequency range of over one octave. But most existing power amplifier configurations cannot meet this requirement while at the same time maintaining a high efficiency. Therefore, a new structure that can achieve multioctave bandwidth is proposed in this paper together with the design methodology. The difficulty in realizing a bandwidth larger than one octave lies in the overlapping of fundamental and harmonic frequencies. Regarding this problem, the continuous class-F mode is extended to allow a resistive second harmonic impedance, rather than the pure reactive one. With the relaxed design requirements and overlapping design space of fundamental and second harmonic frequencies, harmonic tuning and fundamental frequency matching networks can be designed separately. More importantly, broadband matching for fundamental frequencies can be implemented simply by considering only three fundamental frequency points using the multiple frequencies matching method. To verify the validity of the proposed methodology, a multioctave power amplifier was designed, fabricated, and measured. Measured results verify a wide bandwidth of 128.5% from 0.5 to 2.3 GHz. Over this frequency range, drain efficiency was larger than 60% with output power greater than 39.2 dBm and large signal gain larger than 11.7 dB.

Tunneling RFID Tags for Long-Range and Low-Power Microwave Applications

Abstract: Backscatter modulation in radio frequency identification (RFID) tags will potentially connect billions of tomorrow’s devices to the Internet-of-Things. Current passive RFID systems have power constraints that limit RFID tag communication to short ranges, but these limitations can be overcome by employing reflection amplifiers. In this paper, we show that negative differential resistance devices, such as tunnel diodes, exhibit 27 dB more gain and 10 dB lower power consumption than state-of-the-art reflection amplifiers. Two 5.8 GHz prototypes using off-the-shelf tunnel diodes show reflection gains of 40 dB and 29 dB for a total biasing power consumption of 45 ${\mu }\text{W}$ and 39 ${\mu }\text{W}$ , respectively, at impinging RF power levels as low as −84 dBm. A 5.8 GHz RFID link of 23 m was achieved when transmitting only −14 dBm of effective isotropic radiated power from a transceiver with a sensitivity of −90 dBm.

On the Role of Power Electronics in Visible Light Communication

Abstract: The continuous demand of increasing data rates provided by wireless communication systems is contributing to saturating the RF spectrum. Visible light communication (VLC) systems aim to alleviate this congestion using the visible light spectrum. These systems have been proposed to make use of high-brightness LEDs (HB-LEDs) not only for lighting but also for transmitting information by rapidly changing the intensity of the emitted light. A critical issue is that VLC requires a fast HB-LED driver in order to reproduce the target light intensity waveforms, which can include components of several megahertz. Consequently, the HB-LED drivers proposed to date are based on the use of an RF power amplifier (RFPA). These devices provide the required speed, but suffer from very high power losses. To overcome this drawback, different solutions based on the use of fast-response dc/dc converters are presented in this paper. Several dc/dc converters, either to be used instead of an RFPA or to help an RFPA to achieve high efficiency, are thus analyzed. The proposed HB-LED drivers enable the implementation of VLC transmitters without sacrificing one of the most important advantages of HB-LED lighting, namely, its high-power efficiency.

Design and experiments of a dual-band rectenna for ambient RF energy harvesting in urban environments

Abstract: Energy harvesting technologies are required for autonomous applications, like sensors, for which a long-time power sourcing from a battery is infeasible. An energy harvester converts different forms of environmental energy into electricity. It can replace, totally or partially, the batteries of certain micro-systems that have low-energy requirements. Therefore, the authors exploit the use of electromagnetic waves from broadcasters to power wireless sensors. The authors propose to realize harvesting operation at typical ambient radio frequency power levels found within urban environments. To explore the potential for ambient RF energy harvesting, an RF spectral survey was undertaken from outside in Paris. The average RF power in the frequency range 0.9-3 GHz is about -12 dBm. The harvester includes an antenna, an impedance-matching network, and a rectifier; it was designed to cover two frequency bands from the largest RF contributors (GSM1800 and UMTS Band 1). A prototype is designed, fabricated, and measured. The RF-to-DC rectifier and the choice of the load to optimize the amount of DC power are presented. An efficiency of ~45% was observed experimentally for the UMTS Band 1 and 33% for the GSM1800, whenever the incident power is -7 dBm. Numerical and experimental data are reported and discussed.

Exposure of Insects to Radio-Frequency Electromagnetic Fields from 2 to 120 GHz

Abstract: Insects are continually exposed to Radio-Frequency (RF) electromagnetic fields at different frequencies. The range of frequencies used for wireless telecommunication systems will increase in the near future from below 6 GHz (2 G, 3 G, 4 G, and WiFi) to frequencies up to 120 GHz (5 G). This paper is the first to report the absorbed RF electromagnetic power in four different types of insects as a function of frequency from 2 GHz to 120 GHz. A set of insect models was obtained using novel Micro-CT (computer tomography) imaging. These models were used for the first time in finite-difference time-domain electromagnetic simulations. All insects showed a dependence of the absorbed power on the frequency. All insects showed a general increase in absorbed RF power at and above 6 GHz, in comparison to the absorbed RF power below 6 GHz. Our simulations showed that a shift of 10% of the incident power density to frequencies above 6 GHz would lead to an increase in absorbed power between 3–370%.

A quantum-based power standard: Using Rydberg atoms for a SI-traceable radio-frequency power measurement technique in rectangular waveguides

Abstract: In this work, we demonstrate an approach for determining radio-frequency (RF) power using electromagnetically induced transparency (EIT) in a Rydberg atomic vapor. This is accomplished by placing alkali atomic vapor in a rectangular waveguide and measuring the electric (E) field strength (utilizing EIT and Autler-Townes splitting) for a wave propagating down the waveguide. The RF power carried by the wave is then related to this measured E-field, which leads to a direct International System of Units measurement of RF power. To demonstrate this approach, we first measure the field distribution of the fundamental mode in the waveguide and then determine the power carried by the wave at both 19.629 GHz and 26.526 GHz from the measured E-field. We show comparisons between the RF power obtained with this technique and those obtained with a conventional power meter.

System and methods of using electromagnetic waves to wirelessly deliver power to electronic devices

Abstract: Wireless charging systems, and methods of use thereof, are disclosed herein. As an example, a method includes: (i) receiving, by a communications radio of a wireless power transmitter, a communication signal from a communications radio of a wireless power receiver, the communication signal including data used to determine a location of the wireless power receiver, and (ii) determining a location of the wireless power receiver based, at least in part, on the data included in the communication signal. The method further includes, in response to determining that the location of the wireless power receiver is within a wireless power transmission range defined by the transmitter, transmitting radio frequency (RF) power transmission waves towards the wireless power receiver, the RF power transmission waves converging to form controlled constructive interference patterns and destructive interference patterns in proximity to the location of the wireless power receiver.

Compact rectenna based on a fractal geometry with a high conversion energy efficiency per area

Abstract: This work presents the design of a rectenna topology by using a compact microstrip patch antenna based on a fractal model and with the rectifier circuit integrated into the same physical structure. This configuration presents a very reduced circuit area, which makes the proposed rectenna circuit suitable for harvesting and wireless power transfer applications where the size is critical. The proposed compact rectenna, implemented on a low-cost FR-4 substrate, can harvest RF power from 2.45 GHz (ISM band) with a efficiency of ∼62% when the input power harvested by the rectenna is +2 dBm. The suggested rectenna has been manufactured and experimentally characterised, showing a good agreement with the expected simulated results.

Highly-multiplexed microwave SQUID readout using the SLAC Microresonator Radio Frequency (SMuRF) electronics for future CMB and sub-millimeter surveys

Abstract: The next generation of cryogenic CMB and submillimeter cameras under development require densely instrumented sensor arrays to meet their science goals. The readout of large numbers (~10,000-100,000 per camera) of sub-Kelvin sensors, for instance as proposed for the CMB-S4 experiment, will require substantial improvements in cold and warm readout techniques. To reduce the readout cost per sensor and integration complexity, efforts are presently focused on achieving higher multiplexing density while maintaining readout noise subdominant to intrinsic detector noise and presenting manageable thermal loads. Highly-multiplexed cold readout technologies in active development include Microwave Kinetic Inductance Sensors (MKIDs) and microwave rf-SQUIDs. Both exploit the high quality factors of superconducting microwave resonators to densely channelize sub-Kelvin sensors into the bandwidth of a microwave transmission line. In the case of microwave SQUID multiplexing, arrays of transition-edge sensors (TES) are multiplexed by coupling each TES to its own superconducting microwave resonator through an rf-SQUID. We present advancements in the development of a new warm readout system for microwave SQUID multiplexing, the SLAC Superconducting Microresonator RF electronics, or SMuRF, by adapting SLAC National Accelerator Laboratory's Advanced Telecommunications Computing Architecture (ATCA) FPGA Common Platform. SMuRF aims to read out 4000 microwave SQUID channels between 4 and 8 GHz per RF line. Each compact SMuRF system is built onto a single ATCA carrier blade. Daughter boards on the blade implement RF frequency-division multiplexing using FPGAs, fast DACs and ADCs, and an analog up- and down-conversion chain. The system reads out changes in flux in each resonator-coupled rf-SQUID by monitoring the change in the transmitted amplitude and frequency of RF tones produced at each resonator's fundamental frequency. The SMuRF system is unique in its ability to track each tone, minimizing the total RF power required to readout each resonator, thereby significantly reducing the linearity requirements on the cold and warm readout. Here, we present measurements of the readout noise and linearity of the first full SMuRF system, including a demonstration of closed-loop tone tracking on a 528 channel cryogenic microwave SQUID multiplexer. SMuRF is being explored as a potential readout solution for a number of future CMB projects including Simons Observatory, BICEP Array, CCAT-prime, Ali-CPT, and CMB-S4. In addition, parallel development of the platform is underway to adapt SMuRF to read out both MKID and fast X-ray TES calorimeter arrays.

A Scalable and Multidirectional Rectenna System for RF Energy Harvesting

Abstract: A rectenna system having multidirectional receiving capability and scalable antenna gain is presented for radio frequency (RF) energy harvesting. The technique of ray tracing was implemented to evaluate RF power collected by antennas with different half-power beam widths. The results indicate that different radiation features are suited to distinct scenarios. This further indicates that a scalable and multidirectional radiation characteristic is highly desired for energy-harvesting antennas because the level of ambient energy varies over time and space. Accordingly, a rectenna system is proposed that can scale in array size, antenna gain, direction of reception, and radiation pattern to enhance conversion efficiency and dc outputs. The proposed device is comprised of five rectenna cells. Each cell consists of a quasi-Yagi antenna with variable numbers of directors and one RF-to-dc energy-harvesting circuit. Thus, the proposed system can achieve either uniform coverage with enhanced antenna gain or highly directional characteristics at one/multiple incidence angle(s). A prototype is designed, fabricated, and tested in terms of each component and the entire system. The experimental results indicate that the proposed system can be useful in various scenarios, and it outputs enhanced power as scaling is performed in the direction of reception and antenna gain.

Uneven-to-Even Power Distribution for Maintaining High Efficiency of Dual-Linearly Polarized Rectenna

Abstract: The RF-to-dc power conversion efficiency (PCE) of the conventional dual-linearly polarized (DLP) rectenna often suffers from uneven RF power received by two ports of the DLP antenna, which is caused by a tilt angle between the linearly polarized incidence and the two polarizations of the antenna. In this letter, a hybrid coupler is employed to redistribute the uneven power from the DLP antenna to two even power distributions for a successive modified Greinacher charge pump (GCP). Thus, a high RF-to-dc PCE of the modified GCP can be maintained. Both theoretical analysis and experiment validate the proposed power distribution scheme, which maintains a stable high PCE of a DLP rectenna irrespective of polarization tilt angle. The proposed scheme is, thus, suitable for high-efficiency wireless power transfer.

1.0 THz GaN IMPATT Source: Effect of Parasitic Series Resistance

Abstract: The degradation of high-frequency characteristics of a 1.0-THz double-drift region (DDR) impact avalanche transit time (IMPATT) diode based on wurtzite gallium nitride (Wz-GaN), due to the influence of parasitic series resistance, has been investigated. A two-dimensional (2-D) large-signal (L-S) simulation method based on a non-sinusoidal voltage excitation (NSVE) model has been used for this purpose. A comprehensive model of series resistance has been developed by considering the influence of skin effect, and the said model has been incorporated in the 2-D L-S simulation for studying the effect of RF power output and DC to RF conversion efficiency of the device. Results indicate 24.2–35.9% reduction in power output and efficiency due to the RF power dissipation in the positive series resistance. However, the device can still deliver 191.7–202.9 mW peak RF power to the load at 1.0 THz with 8.48–6.41% conversion efficiency. GaN IMPATT diodes are capable of generating higher RF power at around 1 THz than conventional diodes, but the effect of parasitic series resistance causes havoc reduction in power output and efficiency. The nature of the parasitic resistance is studied here in the level of device fabrication and optimization, which to our knowledge is not available at present.

A cm-Scale 2.4-GHz Wireless Energy Harvester With NanoWatt Boost Converter and Antenna-Rectifier Resonance for WiFi Powering of Sensor Nodes

Abstract: The widespread use of WiFi in the 2.4-GHz ISM band creates the potential for RF powering using WiFi radios. This paper presents the design of a cm-scale RF-energy harvester including antenna, rectifier, and dc–dc boost converter for RF powering in the 2.4-GHz ISM band. The rectifier and boost converter are designed while considering cold-start operation and nanowatt-scale available power from the rectifier for RF incident power $\times $ and ~2 $\times $ improvement in range compared to prior art. Measurements using a commercial WiFi TX demonstrate the ranges of up to 1.25 m for 14-dBm output power with 1.3% TX duty-cycling in WiFi access-point mode, demonstrating the feasibility of powering sensors from RF power beacons in the 2.4-GHz ISM band as well as from background WiFi transmissions.

Energy-Ball: Wireless Power Transfer for Batteryless Internet of Things through Distributed Beamforming

Abstract: Wireless power transfer (WPT) promises to deliver energy to devices that are otherwise hard to charge or replace batteries for. This paper presents a new power transfer approach by aligning the phases of a collection of radio frequency (RF) energy chargers at the target receiver device. Our approach can ship energy over tens of meters and to mobile targets. More importantly, our approach leads to a highly asymmetric energy density distribution in the charging area: the energy density at the target receiver is much higher than the energy density at other locations. It is a departure from existing beamforming based WPT systems that have high energy along the energy beam path. Such a technology can enable a large array of batteryless Internet of Things applications and render them much more robust and long-running. Thanks to its asymmetric energy distribution, our approach potentially can be scaled up to ship higher level of energy over longer distances. In this paper, we design, prototype, and evaluate the proposed energy transfer approach, referred to as Energy-Ball. We implement an Energy-Ball testbed that consists of 17 N210 and 4 B210 Universal Software Radio Peripheral (USRP) nodes, yielding a 20 x 20 m2 energy delivery area. We conduct carefully designed experiments on the testbed. We demo that the energy density of Energy-Ball at the target spot is considerably higher than the energy density elsewhere, with the peak to average power ratio of 8.72. We show that Energy-Ball can transfer energy to any point within the area. When the receiver moves at a speed of 0.5 m/s, Energy-Ball can transfer 80% of optimal power to the mobile receiver. Further, our results also show Energy-Ball can deliver over 0.6mw RF power that enables batteryless sensors at any point across the area.

Instantaneous Sample Indexed Magnitude-Selective Affine Function-Based Behavioral Model for Digital Predistortion of RF Power Amplifiers

Abstract: 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.

A 77-dB Dynamic Range Low-Power Variable-Gain Transimpedance Amplifier for Linear LADAR

Abstract: An adjustable-gain transimpedance amplifier with a wide linear dynamic range, low power consumption, and low input impedance was designed for a pulsed linear laser detection and ranging system. To extend the linear dynamic range within a low power consumption, some specific techniques are presented. A low-power current-mirror amplifier with a level shifter was used to decrease the input impedance and keep it stable. Adjustable transimpedance gain extends the input dynamic range, and a high-pass filter eliminates the influence of dc operating point drift caused by the variable gain. When implemented in 0.18- ${\mu }\text{m}$ standard CMOS technology, the receiver achieved a high gain of 106 dB with four configurable gain modes, a wide linear output swing of 1 V, an input-referred noise current of $1.52~ {\rm p{A}/ \sqrt {Hz}}$ , and a minimum detectable signal of 400 nA at SNR = 5, leading to a linear dynamic range of 77 dB, and the power consumption in the highest gain mode was 8 mW with a 3.3-V supply.

A lightweight tile structure integrating photovoltaic conversion and RF power transfer for space solar power applications

Abstract: We demonstrate the development of a prototype lightweight (1.5 kg/m) tile structure capable of photovoltaic solar power capture, conversion to radio frequency power, and transmission through antennas. This modular tile can be repeated over an arbitrary area to form a large aperture which could be placed in orbit to collect sunlight and transmit electricity to any location. Prototype design is described and validated through finite element analysis, and high-precision ultra-light component manufacture and robust assembly are described.

A New Quantum-Based Power Standard: Using Rydberg Atoms for a SI-Traceable Radio-Frequency Power Measurement Technique in Rectangular Waveguides

Abstract: In this work we demonstrate an approach for the measurement of radio-frequency (RF) power using electromagnetically induced transparency (EIT) in a Rydberg atomic vapor. This is accomplished by placing alkali atomic vapor in a rectangular waveguide and measuring the electric (E) field strength (utilizing EIT and Autler-Townes splitting) for a wave propagating down the waveguide. The RF power carried by the wave is then related to this measured E-field, which leads to a new direct International System of Units (SI) measurement of RF power. To demonstrate this approach, we first measure the field distribution of the fundamental mode in the waveguide and then measure the power carried by the wave at both 19.629 GHz and 26.526 GHz. We obtain good agreement between the power measurements obtained with this new technique and those obtained with a conventional power meter.

Reliable and Compact 3- and 4-Bit Phase Shifters Using MEMS SP4T and SP8T Switches

Abstract: This paper presents radio frequency (RF) micro-electromechanical system-based 3- and 4-bit phase shifters using single-pole-four-throw (SP4T) and single-pole-eight-throw (SP8T) switches. The design is fabricated on $635~\mu \text{m}$ alumina substrate using a surface micromachining process. SP4T and SP8T switches demonstrate measured return loss of >16 dB, worst case insertion loss of 1.66 dB, and isolation of >13.6 dB up to 40 GHz. Total area of the SP4T and SP8T switches is 0.98 mm2 and 1.66 mm2, respectively. Switches are capable of handling 1 W of incident RF power and can sustain up to 1 billion cycles at 85°C. Finally, 3- and 4-bit phase shifters deliver measured return loss of >12 dB, average insertion loss of 1 billion cycles with 0.1 W of power in cold switching. In addition, phase shifters also worked satisfactory up to >400 million cycles with 0.5 W of power at 85 °C in hot switching condition. Devices were enclosed within a low-cost package and characterized them systematically. [2017-0104]

Systems, methods, and devices for using a battery as an antenna for receiving wirelessly delivered power from radio frequency power waves

Abstract: Methods of constructing a wireless power receiver that uses a battery as an antenna are provided. The method includes power conversion circuitry that has a connector, the first end connected to at least a part of a battery, and the part of the battery is configured to act as an antenna and receive radio frequency (RF) power signals. The second end of the connector is opposite to the first end and connected to the power conversion circuitry. The power conversion circuitry converts the RF power signals into a direct current (DC) voltage that is used to charge the battery. Additional, some methods for constructing a wireless power receiver include a different connector between the power conversion circuitry and charging circuitry. The charging circuitry is electrically coupled with at least the part of the battery via another connector and provides DC voltage to charge the battery.

A Dual-Polarized Antenna Array With Enhanced Interport Isolation for Far-Field Wireless Data and Power Transfer

Abstract: An in-band full-duplex scheme is proposed for simultaneous power transfer and data delivery in far-field wireless sensor systems. To realize two independent links for power and data delivery, a high isolation level between the local transmitter and receiver of the in-band full-duplex system is critical. An RF front-end architecture, here standing for a dual-polarized antenna array with its feeding network, is presented and detailed in this paper. By using the proposed architecture, self-interference can be well canceled within a wide frequency band, leading to a high inter-port isolation level. To demonstrate the performance of such a front-end structure, an on-board prototype has been developed and examined experimentally. Measured results show that the impedance bandwidth of the developed antenna is from 4.5 to 5.8 GHz. The achieved inter-port isolation is higher than 65 dB from 4.4 to over 6.0 GHz, and over 71 dB from 5.36 to 5.82 GHz, indicating a very high self-interference suppression level. Furthermore, RF power and video transferring experiments are carried out, and good consistency with calculated results is observed.