RF Rectifier Research Articles

A 17.5dB wide-dynamic range high-efficiency RF-to-DC power converter for wireless energy harvesting

ABSTRACT A novel reconfigurable RF-to-DC power converter is proposed for wireless energy harvesting. The proposed RF rectifier employs low-threshold transistors with cross-coupled configuration to enhance the flow of the forward current to the load at low input RF power and adaptive stacking diodes to reduce the leakage current by lowering the driving voltage of the rectifying PMOS transistors at high input RF power. The proposed rectifier utilises the body biasing technique to modulate the threshold voltage and minimises the leakage current of the feedback diodes. The proposed novel techniques improve efficiency and extend the dynamic range. The prototype is implemented in a 65 nm CMOS technology and occupies an active area of 0.0148 mm2. The proposed rectifier achieves a peak power conversion efficiency (PCE) of 76% with a load of a 100-KΩ load at the industrial, scientific, and medical band 433 MHz, and the achieved sensitivity of the rectifier is −18.5 dBm for 1 V DC output voltage. The proposed rectifier offers PCE at −35 dBm of 45.6%, which is the best low-power performance. Compared to the state-of-the-art rectifiers, the proposed design achieves an excellent wide-dynamic range of 17.5 dB, which is ten times better than the conventional cross-coupled rectifier.

A Concurrent Triple-band RF Energy Harvesting Circuit for IoT Sensor Networks

In this paper, a concurrent triple-band RF energy harvesting circuit is proposed. The proposed circuit incorporates a triple-band microstrip antenna combining a low-loss diplexer and three compact RF rectifiers. The proposed circuit operates concurrently at three popular frequency bands: GSM-900, GSM-1800, and 2.45 GHz. To improve output voltage and efficiency, three rectifiers are connected in a stacked topology. The simulated and measured results demonstrate that the circuit operates well in concurrent bands. Moreover, the proposed circuit exhibits a low-complexity structure and compactness in size. These advantages make the circuit a strong potential candidate for running low-power devices in IoT sensor networks.

Differential-drive CMOS rectifier with photovoltaic-assist and self-Vth-cancellation schemes for high power conversion efficiency under low input power conditions

In this study, a differential-drive CMOS RF rectifier equipped with photovoltaic assistance and self-Vth-cancellation (SVC) mechanism has been developed for efficient energy harvesting from ambient radio waves. In addition to the differential-drive dynamic biasing, in which by dynamically biasing the MOSFET gates with differential input signal, both on-resistance and reverse leakage current of the MOSFET are reduced and high power conversion efficiency (PCE) can be achieved, the combination of SVC technology and photovoltaic assist technology allows further improvement of the PCE under low input power conditions. As a result, the PCE of 38.5% was achieved at an input power level of −22 dBm, a frequency of 1 GHz, an output load resistance of 10 kΩ, and a light irradiance of 1 W m−2.

A High Conversion Gain Envelope Detector with Wide Input Range for Simultaneous Wireless Information and Power Transfer System

Wireless sensors networks (WSN) have been gradually facilitating the pervasive connectivity of wireless sensor nodes. A greater number of wireless sensors have been used in different aspects of our life. However, limited device battery life restricts the applications of large-scale WSN. This paper presents a batteryless envelope detector with radio frequency energy harvesting (RFEH) for wireless sensor nodes, which enables simultaneous wireless information and power transfer (SWIPT). The envelope detector is designed for small modulation index AM signals with large amplitude variations. Therefore, the envelope detector is supposed to have wide input range while achieving a high conversion gain. We proposed an adaptive biasing technique in order to extend the input range of envelope detector. The input differential pair is adaptively biased through a feedback loop to overcome the variation of bias point when the amplitude of input signal changes. The cross coupled rectifier and DC-DC boost converter with maximum power point tracking (MPPT) are presented against power conversion efficiency (PCE) degradation of RF rectifier with the input power varying. The adaptive biased envelope detector is theoretically analyzed by square law MOSFET model. Designed with 0.18 μm complementary-metal-oxide-semiconductor (CMOS) standard process, the power consumption of proposed envelope detector is 9 μW. Simulated with a 915 MHz AM input signal with 2 Mbps data rate and 0.05 modulation index, the proposed envelope detector achieves 20.37 dB maximum conversion gain when the amplitude of input signal is 0.5 V, and the PCE of energy harvesting circuits achieves 55.2% when input power is –12.5 dBm.

Design of a Five-Band Dual-Port Rectenna for RF Energy Harvesting

This paper proposed the design of a dual-port rectifier with multi-frequency operations. The RF rectifier is achieved using a combination of L-section inductive impedance matching network (IMN) at Port-1 with a multiple stubs impedance transformer at Port-2. The fabricated prototype can harvest RF signal from GSM/900, GSM/1800, UMTS/2100, Wi-Fi/2.45 and LTE/2600 frequency bands at (0.94, 1.80, 2.10, 2.46, and 2.63 GHz), respectively. The rectifier occupies a small portion of a PCB board at 0.20 λg × 0.15 λg. The proposed circuit realized a measured peak RF-to-dc (radio frequency direct current) power conversion efficiency (PCE) of (21%, 22.76%, 25.33%, 21.57%, and 22.14%) for an input power of −20 dBm. The RF harvester attains a measured peak RF-to-dc PCE of 72.70% and an output dc voltage of 154 mV for an input power of 3 dBm at 2.46 GHz. Measurement of the proposed rectifier in the ambiance gives a peak dc output voltage of 376.1 mV from the five signal tones. Similarly, a low-powered bq25504-674 evaluation module (EVM) is integrated with the rectifier. The module boost and drive the rectifier output dc voltage to 945 mV. The performance of the proposed rectifier in the ambiance environment makes it a suitable module for low-powered RF applications.

A Broadband High-Efficiency RF Rectifier for Ambient RF Energy Harvesting

In this letter, a compact broadband high-efficiency RF rectifier is presented for ambient RF energy harvesting (EH). A novel impedance matching network with an additional quarter-wavelength short-circuited stub was designed to achieve broadband impedance matching. After the branch was added, the parallel resonance point on track $S_{11}$ did not move, and the remaining points were compressed. The measurement results show that the proposed topology could realize a broadband high-efficiency rectifier for ambient RF EH, and the measured results were basically consistent with the simulation results. The measured efficiency is as high as 71.5% for an input power level of 8 dBm. A 1–2.4 GHz wide frequency band with an efficiency above 50% is achieved for an input power level of 5 dBm with a terminal load of 1.6 $\text{k}\Omega $ . Moreover, the circuit had wide dynamic input power characteristics, whose measured values remained above 50% with an input power of 3–14 dBm.

RF Near-Field Coupling System Using Reverse PDN and Considering Electromagnetic Effects

One of the more intriguing applications of wireless power transfer is power delivery for low-power Internet of Things (IoT) devices. By utilizing RF near-field coupling (NFC), an improved combination of small receiver coil area and system efficiency can be achieved, as is ideal for wireless charging for low-power IoT platforms. However, utilizing high efficiency RF NFC comes with a cost—various electromagnetic effects can lead to detuning of the resonant frequency if not properly modeled. In addition, integrating power regulation with high frequency ac–dc conversion can create large ripple voltage supply to a power distribution unit (PDU). This paper investigates the system level issues that arise in efficient, regulated RF NFC systems for milliwatt-scale output power. A method for modeling the various electromagnetic, frequency detuning effects is presented, as well as a selection process for the circuit component values in the design. Furthermore, a reverse power distribution network is designed to integrate the rectifier with a PDU, introducing a target impedance and phase considerations for an RF rectifier. The modeling and integration solutions are experimentally verified through two different RF NFC systems. The systems have measured peak efficiency of 68.4% at 3.3 V output and 58.6% for 1 V output with less than 100 mm $^2$ receiver coil area, demonstrating a unique combination of small coil area and high efficiency compared to other NFC systems to better support low-power IoT devices.

A survey on low power RF rectifiers efficiency for low cost energy harvesting applications

In this paper the analysis, simulation and prototyping of radio frequency rectifier topologies for ambient energy harvesting applications are evaluated, highlighting the effects of input power levels below −10 dBm. The equivalent diode impedance model is taken into consideration for better interpreting its effects when attached to each rectifier topology. Furthermore, the output capacitance modeling and its effects over the rectifier efficiency are discussed for different capacitance types, including a radial stub. A prototype of the most prominent topology was built on a low cost FR-4 substrate for RF harvesting in the range of −10 to −20 dBm, resulting in an approximate efficiency between 40% and 25%, respectively.

An Optimized 2.4GHz RF Energy Harvester for Energizing Low-Power Wireless Sensor Platforms

The lifetime of battery-operated sensor platforms (i.e., sensor nodes) is a critical issue. The replacement of their batteries is quite a challenging task if these platforms are deployed for detecting events in inaccessible geographical areas (e.g., forest). This paper describes an optimized RF energy harvester/scavenger (consisting of an antenna, impedance matching circuit and rectifier) for energizing low-power sensor platforms (electronic systems). Few nonmatched rectifiers (using HSMS-285X Schottky diodes) are fabricated to characterize the input impedance for different sets of parameters. After characterization a proper impedance matching circuit is integrated for the maximum power transfer from antenna to rectifier. It is shown that a single stage of RF rectifier is enough to produce output voltage of 1.8[Formula: see text]V. Very few realizations of RF energy harvester are reported in the literature under 2.4[Formula: see text]GHz ISM band category. Furthermore, high-gain microstrip patch array antennas are fabricated to capture the maximum power from the surroundings. The maximum harvesting range of 0.92[Formula: see text]m is obtained at 27[Formula: see text]dBm transmitting power level.

Analysis and design of an integrated RF energy harvester for ultra low‐power environments

SummaryRadio‐frequency (RF) energy harvesting must cope with the limited availability and high variability of the energy source. In this paper, the available RF power in three typical environments (urban, semi‐urban, and rural) is investigated. Measurements show that in the surveyed urban and semi‐urban environments, an average input power above −22 and −29 dBm, respectively, is available in the [700, 1,000] MHz band.A mathematical model of the interface between the RF rectifier and the DC‐DC converter is provided. The analysis demonstrates that the energy can be efficiently transferred to the external accumulator coupling the rectifier with a strobed, input control DC‐DC converter.Based on the measurements and the analysis, an RF harvester architecture has been designed in 65 nm Complementary Metal‐Oxide Semiconductor (CMOS) technology to operate over the [−40, 85]oC temperature and the [1.1, 2.5] V battery voltage ranges. The input control strategy adopted for the converter allows the adaptation of the harvester to the available RF power and enables a real maximum power point tracking (MPPT).Post‐layout simulation of the harvester, recharging a large capacitor, precharged at 2 V, at 950 MHz of input frequency returned a 33.4% peak efficiency with an input power of 15 μW (−18 dBm). The minimum input power leading to a positive energy balance is −30 dBm with an output voltage of 1.1 V.

Design of high‐efficiency CMOS rectifier with low reverse leakage for RF energy harvesting

A CMOS cross-coupled RF rectifier that improves power conversion efficiency (PCE) with low reverse leakage current for energy harvesting wireless sensors is proposed. In this Letter, the authors propose a CMOS cross-coupled differential RF rectifier that uses a thick-oxide MOSFET as a rectifying device to improve PCE by reducing reverse leakage current. The proposed rectifier is designed for UHF band application using 0.18 µm CMOS technology. Proposed rectifier achieves a peak PCE of 75.2% and sensitivity of − 17 dBm for 1 V output voltage. Peak PCE is improved by 8.8% compared to the conventional rectifier.

In brief

PAGE 436 A novel subwavelength and low-profile element has been proposed by a group of Chinese researchers for reflected antenna array applications. A metallic hole is used to achieve smaller profile and period dimensions with the element obtaining a wide reflected phase shifting range. The results are validated with data gained from a fabricated prototype. PAGE 473 A classical expression of quantum microwaves after measurement, dependent on intrinsic correlated characteristics between measurement uncertainties and components of the microwave field, has been presented by researchers from China. The results are in agreement with experiments of entangled quantum microwaves and provide a more intuitive understanding of the wave behavior. Configuration of the proposed element. PAGE 434 A pair of researchers in China have designed and produced a slim dual-polarised antenna with omnidirectional patterns for WLAN applications. The slim structure has the advantages of light weight, convenient implementation, and easy fabrication due to the improved isolation between the two polarisations, with a rectangular loop acting as a tuner for the antenna impedance. Waveform schematics before and after measurement. PAGE 446 Improved energy harvesting efficiency in wireless sensors using a CMOS cross-couple RF rectifier has been presented by researchers in Korea. The proposed device uses a thick-oxide MOSFET to improve efficiency by reducing reversing leakage current and presents an 8% peak efficiency gain compared to conventional rectifiers. Feeding network of the proposed antenna. PAGE 438 Researchers from Taiwan have put forward a fully integrated bio-system with high sensitivity for electrochemical detection. The system measures the electrochemical characteristics using cyclic voltammetry whith the operating mechanism of the potentiostat behaving like a single-slope ADC. The system demonstrates feasibility in low-electrolyte environments. Voltage waveforms of internal nodes and output. Electrochemical detection system architecture.

High-Efficient Broadband CPW RF Rectifier for Wireless Energy Harvesting

In this paper, the implementation of a compact, wideband, single layer, and simple RF rectifier design is discussed. The proposed rectifier configuration is based on the coplanar waveguide transmission line. The rectifier is constructed using the voltage doubler circuit in conjunction with a broadband matching network. To obtain a small circuit size, the matching circuit is constituted with a series dual-inductive lumped element. The overall rectifier dimensions are very compact $22.5\times 31\,\,\text {mm}^{2}$ . In order to accurately characterize the rectifier performance, the electromagnetic and harmonic balance simulations are conducted using the Agilent, ADS software. The comparison shows good agreement between the simulation and measurement results. For instance, the peak measured efficiency is 74.8% at 10-dBm RF input power and the corresponding simulated value is 75% with a terminal load of 1 $\text{k}\Omega $ . The efficient frequency range is extending from 0.1 to 2.5 GHz, with an efficiency of more than 45% at input power 10 dBm.

Harvesting Ambient RF Energy Efficiently With Optimal Angular Coverage

Ambient electromagnetic and RF energy is an ubiquitous energy resource that is found everywhere but difficult to harvest because of the time-varying orientation of incoming radiations and the low efficiency of RF rectifiers resulting from a low input power density operation. In response to these two challenges that come with the design of rectennas for ambient energy harvesting, this paper discusses a figure of merit to evaluate the rectenna performance that combines the rectification efficiency, the radiation efficiency, and the spherical coverage of the antenna. To illustrate this proposed figure of merit, a rectenna with a strengthen RF-to-dc efficiency and also a full spatial coverage is designed using beam-forming networks. The resulting system is demonstrated for a wireless sensor mounted on a pole. To maintain a reasonable size of the prototype, a miniaturization technique of a $4 \times 4$ Butler matrix (BM) is investigated, which allows for the reduction of the footprint of the BM by 2 compared to its classical microstrip design counterpart at 2.4 GHz. The overall rectification efficiency and dc power patterns are reported for the elevation plane of one multidirectional rectenna at 2.4 GHz for an incident power density of $0.45\,\,\mu \text {W}\cdot \text {cm}^{-2}$ . It is shown that the system can triple the dc output power compared to a three-dipole counterpart occupying the same area. Furthermore, while the maximum harvesting capability at $1 \,\,\mu \text {W}\cdot \text {cm}-^{2}$ does not exceed $28\pi $ %.steradian in the literature, it reaches $43.6\pi $ %.steradian with the proposed demonstrator.

A high efficiency CMOS RF rectifier for RF energy harvesting with dynamic self-body-biasing technique

A high efficiency CMOS RF rectifier for RF energy harvesting with dynamic self-body-biasing technique

Compact and Broadband RF Rectifier With 1.5 Octave Bandwidth Based on a Simple Pair of L-Section Matching Network

This letter proposes a novel wideband rectifier circuit for RF energy harvesting. The proposed circuit can collect signals efficiently over broad bandwidth spanning from 0.87 to 2.7 GHz which includes UHF ISM 900 MHz, GSM 900 and 1800 MHz, wireless communication, PCS, and ISM 2.4 GHz. In order to obtain sufficiently large rectifier bandwidth, a matching circuit based on high-pass type L-section for lower band impedance matching and inductive L-section for higher band impedance matching is proposed. The rectifier circuit is constructed using voltage doubler configuration with Schottky diode SMS7630-005LF. The circuit is optimized and refabricated to compensate the undesired parasitic and obtain the required rectifier performance. Two prototypes were simulated, fabricated, and characterized. The rectifier has a measured conversion efficiency exceeding 30% from 870 MHz to 2.5 GHz at 0 dBm input power and a load terminal of 2 $\text{k}\Omega $ and a dc output voltage equal to 1 V. The circuit sensitivity may reach up to −20 dBm with dc output voltage 40 mV and 8% conversion efficiency. The maximum measured efficiency is 63% from 1.1 to 1.35 GHz.

Transient Input Impedance Modeling of Rectifiers for RF Energy Harvesting Applications

This brief presents a model for the input impedance of the RF rectifiers during charging. It uses a power-based method and finds a closed form equation for the transient variation of the input impedance. To validate the model, a typical single stage rectifier is designed using Schottky diodes and simulated at 900 MHz using ADS. The simulation results show a good agreement with the proposed model. Moreover the rectifier is realized on PCB. The measurements agree well with the values calculated using the model which further confirms the proposed model.

GaN HEMT DC $I$ – $V$ Device Model for Accurate RF Rectifier Simulation

Recently, various high-efficiency RF rectifiers have been proposed. In this letter, to improve the simulation accuracy of RF active rectifier circuits, a new device model for GaN HEMTs is proposed that improves the reproducibility of $I_{D}$ – $V_{\mathrm{ DS}}$ characteristics in the third-quadrant region (both drain voltage and drain current are negative). Based on measured characteristic data of an actual GaN HEMT, the device parameters for this model have been decided, and the advantage of the new device model has been confirmed.

Balanced RF Rectifier for Energy Recovery With Minimized Input Impedance Variation

A balanced RF rectifier is proposed to replace terminations in microwave circuits and thus to recycle the otherwise dissipated power in resistances. In order not to degrade the performance of the original circuits, a balanced configuration is adopted because it minimizes the variation of input impedance of the rectification circuitry. This approach achieves good input reflection coefficient over a large dynamic range and operating frequencies. The highly efficient energy recycler is composed of a 3 dB quadrature coupler and two identical RF rectifiers. The impact of amplitude and phase imbalances of the transfer characteristics of the coupler is discussed. Furthermore, an arbitrary-port-resistance coupler is studied to replace non-50- $\Omega $ terminations. The experimental verification demonstrates that the proposed circuit provides an input reflection coefficient of better than −15 dB from 2.2 to 2.5GHz over different input power levels. The measured peak RF-to-dc efficiency is 74.9% at 2.34 GHz with $S_{11} = -24\,\mbox {dB}$ . The proposed balanced rectifier thus significantly improves $S_{11}$ over existing rectifiers and is therefore suitable for replacing resistive terminations in a large variety of circuits.

A Fully Integrated Reconfigurable Self-Startup RF Energy-Harvesting System With Storage Capability

This paper introduces a fully integrated RF energy-harvesting system. The system can simultaneously deliver the current demanded by external dc loads and store the extra energy in external capacitors, during periods of extra output power. The design is fabricated in 0.18-μm CMOS technology, and the active chip area is 1.08 mm 2 . The proposed self-startup system is reconfigurable with an integrated LC matching network, an RF rectifier, and a power management/controller unit, which consumes 66-157 nW. The required clock generation and the voltage reference circuit are integrated on the same chip. Duty cycle control is used to operate for the low input power that cannot provide the demanded output power. Moreover, the number of stages of the RF rectifier is reconfigurable to increase the efficiency of the available output power. For high available power, a secondary path is activated to charge an external energy storage element. The measured RF input power sensitivity is -14.8 dBm at a 1-V dc output.