Microwave Rectifier Research Articles

High-Efficiency Microwave Rectifier With Coupled Transmission Line for Low-Power Energy Harvesting and Wireless Power Transmission

In this article, a Schottky diode-based microwave rectifier that employs coupled transmission lines (CTLs) is proposed. CTL is herein used to enhance the voltage amplitude across the Schottky diode with the consequent increase in the rectifier efficiency, especially for low input powers. It is also shown that multiple cascaded CTLs can further enhance the rectifier conversion efficiency, even if this benefit is partially annihilated by the increased insertion loss. Several compact prototypes with single and dual CTLs for 2.45 GHz have been fabricated and measured for different input power levels. Particularly, a single CTL rectifier exhibits RF-to-dc conversion efficiency of 67.7% for an input power of 0 dBm, leading to an improvement of about 3% with respect to other referred rectifiers (with a dc load of 4.47 kQ), while dual CTL rectifier has an outstanding efficiency of 75.3% for an input power of only 5.5 dBm (with a dc load of 1.76 kQ). Passive voltage boost by means of CTLs can be applied to other rectifier circuits as also demonstrated.

Short-Distance Wireless Power Transfer Based on Microwave Radiation via an Electromagnetic Rectifying Surface

Microwave power transmission has traditionally been used for long-distance applications so far. For the first time, we experimentally demonstrate efficient short-distance wireless power transfer based on microwave radiation. To overcome the directivity deterioration of an antenna as the transfer distance decreases in the near field, an electromagnetic rectifying surface is proposed for reflection-less microwave reception and rectification. The rectifying surface is an array of metamaterial particles integrated with rectifiers, as a whole its impedance engineered to match with free space. Therefore, it keeps fully receiving the radiated power in the near field of a transmitting antenna without reflection; and maximally converts it into direct current. A rectifying surface of 14 × 14 unit cells is fabricated, and a short-distance wireless power transfer system is developed. Under an input power up to 45 dBm at 2.45 GHz, the measured transmission efficiency (from the microwave input to the direct current output) reaches 52.3%, 52.5%, 47.9%, and 41.7% over a distance of 5, 10, 15, and 20 cm, respectively. Even when the incident angle severely deviates to ±52.5° on E- and H-plane, the transmission efficiency over distance 15 cm merely declines 12% and 22.2% at most, respectively. The presented wireless power transfer based on microwave radiation via an electromagnetic rectifying surface provides a highly efficient and distance/angle-alignment insensitive alternative to the common coupling-based coil solution for short-distance applications.

Effect of channel length to the frequency response of Si-based Self-Switching Diodes using two-dimensional simulation

A planar nanodevice, known as the self-switching diode (SSD) which can be exploited as a high-speed rectifier in a wide range of applications. The non-linearity in the I-V characteristic of the SSD structure has been aimed for rectification application at GHz frequencies is reported. In this work simulation has been conducted on Si-based SSD structure with 230 nm L-shaped channels using ATLAS device simulator under the channel length range of 0.5 μm to 1.3 μm. Furthermore, the validity of the cut-off frequency has also been described using a theoretical value of f t at zero bias. The results showed that the optimization in the channel length of the SSD can assist the high cut-off frequency of SSD rectifying behavior to efficiently operate as microwave rectifier.

GaN Schottky Barrier Diode-Based Wideband and Medium-Power Microwave Rectifier for Wireless Power Transmission

This article presents a finger-type gallium nitride (GaN) Schottky barrier diode (SBD)-based microwave rectifier with medium-power capacity and wide power bandwidth. A complete solution including SBD design and fabrication, model extraction, circuit optimization, and demonstration is proposed. The finger-type anode and critical thickness epitaxial layer techniques are adopted to reduce the GaN SBD resistance to 1.9 $\Omega $ (0.011 $\text{m}\sf \Omega \cdot \text {cm}^{{2}}$ ) and achieve nearly constant junction capacitance over a wide range of voltages (17–25 V). Revised equivalent models including the effects of large pads, critical thickness epitaxial layer, and finger-type layout are proposed to describe the new features of the SBD. A 2.45-GHz microwave rectifier based on the GaN SBD is designed and measured, having a maximum power and an efficiency of 1.91 W and 78.5%, respectively. The high-efficiency power range (≥70% and ≥75%) is significantly extended to 14 and 10.8 dB. Finally, a wireless clinical examination prototype constructed by a rectifier, antennas, biomedical sensors, and a signal processer is proposed for demonstration. The resulting wireless electrocardiogram shown in computer is clear and stable.

Improved microwave sensitivity to 706 kV/W by using p-GaAsSb/n-InAs nanowire backward diodes for low-power energy harvesting at zero bias

In this study, a p-GaAs0.4Sb0.6/n-InAs nanowire backward diode (NW BWD) with a large sensitivity of 706 kV/W, exceeding that of Schottky barrier diodes (SBDs), was developed for low-power microwave rectification at zero bias. The interband tunneling of the NW BWDs under zero-bias condition displayed a large nonlinear characteristic of typical BWDs, which is effective for realizing power detection with high sensitivity. The fabricated NW BWDs indicated linear detected voltages (Vdet) when a microwave input power (Pin) of ∼1 µW was applied at 2.4 GHz. From the Vdet, Pin, and return loss obtained from the S-parameter measurements, an impedance-matched voltage sensitivity of 706 kV/W was calculated for the NW BWD at zero bias. The obtained sensitivity value was higher than that of a well-designed SBD, which was ∼62 kV/W at 2.4 GHz. According to the extracted device parameters, it was found that to improve the sensitivity of the NW-BWD, not only the junction capacitance of the diode but also the parasitic pad capacitance needs to be reduced. The high sensitivity is attributed to the high curvature coefficient of −26.7 V−1 and the small junction capacitance of the NW structure of the BWD.

A Compact High-Efficiency Broadband Rectifier With a Wide Dynamic Range of Input Power for Energy Harvesting

In this letter, a compact high-efficiency broadband microwave rectifier with an extended range of input power is proposed for energy harvesting. In the proposed structure, a novel broadband impedance-matching network is employed to reach high radio frequency (RF) to dc conversion efficiency. The reduction in mismatching loss over a wide bandwidth and input power range is achieved by impedance transformation from three segments of microstrip lines, which leads to a compact design to realize broadband impedance matching. A theoretical analysis and simulations of the proposed rectifier are presented. For validation, a broadband rectifier operating between 2.1 and 3.3 GHz is implemented and tested. The proposed rectifier shows a bandwidth of 44.4% for efficiency over 70% at an input power of 14 dBm. The measured efficiency remains above 50% from 2 to 3.3 GHz with an input power from 4 to 16 dBm. Moreover, the proposed rectifier has a compact size of 31 mm $\times18$ mm.

Design of Strained Ge Schottky Diode on Si Substrate for Microwave Rectifier Circuit

In recent years, wireless energy transmission technology has developed rapidly and has received increasing attention in the industry. For microwave wireless energy transfer system applications, Ge Schottky diodes as the core components of the rectifier circuit are commonly used. Compared with Ge semiconductor, strained Ge semiconductor on Si substrate has the advantages of compatibility with Si process, low cost, and high electron mobility. It is an ideal replacement material for Ge semiconductor applications. In view of this, based on the model of the relationship between the performance of strained Ge semiconductor on Si substrate Schottky diodes and the geometric parameters of the device and the physical parameters of the material, Silvaco TCAD and ADS simulation software are jointly used to propose a novel strained Ge semiconductor on Si substrate Schottky diode for microwave rectification circuit. Simulation results show that the strained Ge semiconductor on Si substrate Schottky diode has a rectification efficiency of 70.1% when the input of the rectifier circuit is 20 dBm, the load resistance is R = 1000 Ω, and the load capacitance is C = 100 pF. Compared with traditional Ge Schottky diodes, this optimal operating point is closer to a low energy density, which is beneficial to a wide range of energy absorption. Studies have shown the feasibility of replacing Ge Schottky diodes. The research in this paper can provide valuable reference for the design and development of the core components of the rectifier circuit of the microwave infinite energy transmission system.

A Wide Dynamic Range Rectifier Array Based on Automatic Input Power Distribution Technique

In this letter, a microwave rectifier array using an automatic input power distribution technique (AIPDT) is proposed to achieve high conversion efficiency over a wide dynamic input power range. The rectifier array employs two rectifier cells operating at low- and high-power levels, respectively, and utilizes AIPDT to distribute the RF input power between them according to the input power level. In this way, a high RF-dc power conversion efficiency (PCE) and a low reflection coefficient over a wide input power range are achieved. For validation, the proposed rectifier array at 2.4 GHz was designed, fabricated, and characterized. The experimental results show that the PCE maintains over 50% when the input power ranges from 2.2 to 26.5 dBm, and the input power range for PCE >30% is from −7 to 30 dBm. Besides, the reflection coefficient remains less than −10 dB over a 40-dB dynamic range (−10 to 30 dBm).

High-Power Wire Bonded GaN Rectifier for Wireless Power Transmission

A novel wire bonded GaN rectifier for high-power wireless power transfer (WPT) applications is proposed. The low breakdown voltage in silicon Schottky diodes limits the high-power operations of microwave rectifier. The proposed microwave rectifier consists of a high breakdown voltage GaN rectifying element for high-power operation and a novel low loss impedance matching technique for high efficiency performance. Wire bonding method is adopted to provide electrical connection between GaN chip and board which induces undesirable inductance. In order to realize high efficiency performance, an impedance matching network is proposed to exploit the unavoidable inductance along with a single shunt capacitor, resulting in a low loss matching circuit to achieve a compact high-power rectifier. The fabricated GaN rectifier exhibits a good performance in the high-power region and can withstand up to 39 dBm input power before reaching the breakdown limit at the operating frequency of 0.915 GHz and load resistance of 100 Ω. It has a compact size and exhibits high efficiency performance in high-power region (achieved a maximum efficiency of 61.2% at 39 dBm), making it suitable for high-power applications like future unmanned intelligent devices and WPT in space applications.

A High-Efficiency Inverse Class-F Microwave Rectifier for Wireless Power Transmission

A high-efficiency inverse class-F microwave rectifier for wireless power transmission is described in this letter. The proposed inverse class-F harmonic termination network is realized by connecting a $\lambda /12$ open-ended transmission line in parallel with the diode cathode, and a $\lambda /8$ short-ended transmission line in series with the diode anode. This structure yields a compact layout, and measurement results have demonstrated a peak conversion efficiency of 80.4% for an input power of 13 dBm at 2.35 GHz, and an efficiency larger than 60% within the bandwidth 2.25–3 GHz and for a wide range of output loads.

Compact High-Efficiency Broadband Rectifier With Multi-Stage-Transmission-Line Matching

This brief proposes a compact high-efficiency broadband microwave rectifier for energy harvesting. The proposed rectifier is designed to operate over a broad bandwidth spanning from 2 to 3 GHz and an input power dynamic range from 0 dBm to 10 dBm. In the proposed structure, a compact broadband low-loss matching network and a dc-pass filter with a broad stopband were designed, leading to a high conversion efficiency in a wide frequency range with compactness. For the matching network, low loss and compact size were achieved by strategically choosing and designing three transmission line segments. Moreover, the proposed dc-pass filter is compact and can effectively block broadband RF signal and its in-band high order harmonics. Theoretical analysis and simulations of the proposed structure were carried out. A prototype was fabricated, which demonstrates a broadband bandwidth of 41.5% (2.0–3.05 GHz) where the RF-dc power conversion efficiency is higher than 70% at an input power of 10 dBm. The measured efficiency remains over 45% within 1.9–3.05 GHz when the input power decreases to 0 dBm. The maximum measured efficiency is 75.8% at an input power of 14 dBm.

A Compact High-Efficiency Watt-Level Microwave Rectifier With a Novel Harmonic Termination Network

A compact high-efficiency and high-power class-F microwave rectifier for the frequency of 2.45 GHz is described in this letter. The proposed rectifying circuit mainly consists of a high reverse breakdown voltage Schottky diode for high power conversion, and a novel harmonic termination circuit, resulting in a simpler and more compact structure. The microwave rectifier has been optimized with the aid of a simulation software, and the manufactured prototype exhibits a measured microwave-to-dc conversion efficiency larger than 80% for an input power level of 31 dBm, in good agreement with simulation results.

The linear relationship of spin pumping energy in a La:YIG/Pt heterostructure used in a microwave rectifier

ABSTRACTLa3+ doped yttrium iron garnet films have been grown on (111) oriented gadolinium gallium garnet substrates via Liquid phase epitaxy technique as a basic material for ISHE device fabrication. Pt as a material with a large spin hall angle was used as a spin detection layer. We investigated the dependence of the spin pumping effect on the power and frequency of the excitation microwaves in La:YIG/Pt bilayers by measuring the ISHE voltage. We demonstrated that the area under the ISHE curve(SISHE) across a wide power range had a nearly linear correlation with the input microwave power (Pin). The parameter SISHE can be used to describe the spin current energy in a Pt layer which can be a useful parameter for a microwave rectifier.

Compact Microwave Rectifier with Wide Input Power Dynamic Range Based on Integrated Impedance Compression Network

A compact rectifier with high efficiency at wide input power dynamic range is proposed in this paper. The circuit consists of a matching network, two shunt connected diodes with an integrated impedance compression network (IICN) and a dc-pass filter. The IICN significantly reduces the diode impedance variation when input power changes, hence improves matching as well as efficiency of the rectifier at wide input power dynamic range. Different from the conventional resistance/impedance compression networks, which can only work under certain impedance condition with dual-branch topology, the IICN can directly operate two diodes in parallel in a single-branch with no impedance limitation. Thus, less components and branch are needed, resulting in size reduction and lower circuit complexity. The design flexibility is also enhanced. Mechanism of the IICN is analyzed. A prototype operating at 2.45 GHz is optimized, fabricated and measured. The total size of the prototype is 0.18λ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The efficiency higher than 70% of the peak value is realized at input power ranging from 0.8 dBm to 18.0 dBm.

High-Efficient Rectifier With Extended Input Power Range Based on Self-Tuning Impedance Matching

In this letter, a microwave rectifier with a wide input power range is presented by proposing a self-tuning impedance matching (STIM). The STIM consists of a varactor reversely biased by the output voltage of the rectifier to compensate the variation of the input impedance caused by the input power, so that impedance matching is obtained over a wider input power range. For validation, the proposed rectifier at 2.4 GHz was designed and implemented. The experimental results show that the RF-dc power conversion efficiency maintains over 50% and 70% within the input power ranges of 2.5–25.5 dBm and 11–24.5 dBm, respectively. Compared with the counterpart without the STIM, an improvement of 7.2 dB in terms of the input power range when the reflection coefficient is less than −10 dB was successfully demonstrated.

High-frequency very long wave infrared quantum cascade detectors

High speed quantum cascade detectors (QCDs) in a very long wave infrared range have been fabricated and characterized. Based on the resonant longitudinal optical-phonon scattering extraction relaxation mechanism, the QCD material behaves at an intrinsically high speed. In order to achieve high speed operation, we integrated microwave technology into the device process to reduce the parasitic parameters and ensure a low time constant of the effective resistance, iInductance, capacitance (RLC) circuit. The peak response is located at 14.2 μm at 77 K. The electrical response characteristics of these QCDs was tested using a microwave rectification technique. The −3 dB cutoff frequency of a 100 × 100 μm2 QCD is 3.2 GHz. The cutoff behavior of our devices were modeled with a second order filter RLC circuit model and showed good agreement with the experimental data.

High-Efficiency Microwave Rectifier With Extended Operating Bandwidth

This brief presents a microwave rectifier using a novel impedance matching technique to extend the operating bandwidth. Originated from the impedance control at two separated frequencies, the matching network is capable of manipulating the impedance over a wide frequency band by three steps. In this way, the operating bandwidth is extended. Theoretical analysis is carried out and closed-form design equations are derived. For validation, a wideband rectifier is implemented operating at 0.57–0.90 GHz at the input power of 12.8 dBm. It exhibits the fractional bandwidth of 44.9% for RF-dc conversion efficiency of higher than 70%. Moreover, the rectifier keeps more than 50% efficiency within 0.57–0.90 GHz at the input power from 3 dBm to 14.1 dBm.

InGaAs-based planar barrier diode as microwave rectifier

In this report, we proposed and simulated a new planar nonlinear rectifying device fabricated using InGaAs substrate and referred to as a planar barrier diode (PBD). Using an asymmetrical inverse-arrowhead-shaped structure between the electrodes, a nonuniform depletion region is developed, which creates a triangular energy barrier in the conducting channel. This barrier is voltage dependent and can be controlled by the applied voltage across the PBD, thus resulting in nonlinear diode-like current–voltage characteristics; thus it can be used as a rectifying device. The PBD’s working principle is explained using thermionic emission theory. Furthermore, by varying the PBD’s geometric design, the asymmetry of the current–voltage characteristics can be optimized to realize superior rectification performance. By employing the optimized structural parameters, the obtained cut-off frequency of the device was approximately 270 GHz with a curvature coefficient peak of 14 V−1 at a low DC bias voltage of 50 mV.

Novel Time-Domain Schottky Diode Modeling for Microwave Rectifier Designs

A novel modeling methodology of Schottky diode for microwave rectifier design is proposed in this paper. The challenge was to consider the effective capacitance of the diode under different status being usually ignored in previous works. In addition, the charging and discharging behaviors causing extra power consumption had been considered for a higher modeling accuracy. To improve the diode modeling, Kirchhoff current and charge conservation law are utilized to analyze the charge and discharge effects and synthesize the corresponding close-form equations. Based on these equations, once the diode model, operating frequency, output dc current are determined, the optimal performance prediction for the diode, load value selection, and impedance matching design can be implemented accordingly. For validation, the proposed modeling methodology is compared with the commercial simulation software advanced design system and other related works. For further verification, a compact single diode rectifier operating at 5.8 GHz is designed, fabricated, and measured. Good agreement between the calculated, simulated, and measured data can be obtained, demonstrating the effectiveness of proposed method.

Novel Microwave Rectifier Optimizing Method and Its Application in Rectenna Designs

In this paper, a fast converging and computationally efficient iterative method for rectifier optimization is proposed. The method is carried out in the advance design system. By taking into account the interaction between the received power and output performance, the impedance of the Schottky diode when operating optimally in the rectifier can be precisely obtained once the spice model, operating frequency, and the dc load value are given. The impedance can be used to design the matching to minimize the insertion loss. The time and effort needed for the method are smaller than the optimizing tools provided in ADS and other related works, and the reliability of simulation is enhanced. For demonstration, a compact rectifier operating at 5.81 GHz is optimized, fabricated, and measured. The measured power conversion efficiency exceeds 40% at input power level ranging from −5.5 to 12.5 dBm, and the optimum reaches 69.4% at 8.2 dBm. Good agreement can be found between simulated and measured data. Finally, the rectifier is integrated with a high-efficiency antenna to form a rectenna design; 69.2% optimal efficiency is obtained at 0.41 mW/cm2 power density in the measurement.