Low Conversion Loss Research Articles

A Broadband Low Conversion Loss Single-Ended Resistive Mixer With an Innovative Topology

A Broadband Low Conversion Loss Single-Ended Resistive Mixer With an Innovative Topology

A mixer architecture using GaN-based split-gate nanowire transistor

Frequency mixer is an essential block in radio-frequency signal processing for frequency translation and phase comparison. The most common mixers are fabricated using passive elements which suffer from significant conversion loss and low isolation. Mixers using active devices are used less frequently and rather less matured on GaN technology. Here, we demonstrate a mixer based on GaN split-gate nanowire transistor, allowing low conversion loss and high isolation. A constriction is formed by electrostatic modulation of the effective gate width. The threshold voltage of the transistor is modified by one of the gate voltages through the width variation, while the other gate voltage biases the transistor in the saturation region. The nonlinear dependency of the transistor characteristics on the two gate voltages facilitates frequency translation. The mixing characteristics of this architecture are verified both experimentally and theoretically. The output power spectral density peaks at the difference frequency with a minimal conversion loss. Extremely high isolation is measured using three-port S-parameter measurements. The proposed architecture shows multiple benefits, additionally facilitating monolithic mixers on the GaN platform.

3D-printed x-band 1-port TM01 circular waveguide to 4-port TE10 rectangular waveguide mode converter & power splitter

ABSTRACT This paper investigates a novel waveguide component design with dual functionality of mode conversion and power splitting. Because of its complex internal geometry which conventional fabrication methods cannot realize, additive manufacturing was explored, specifically selective laser melting. The end-to-end process of design, simulation, fabrication, and measurement will be discussed in detail. The said waveguide component converts between 4 rectangular waveguide TE10 mode and 1 circular waveguide TM01 mode. The 1 to 4 splitter was done while achieving low power splitting losses and mode conversion losses with low return losses. This allows for waveguide connections to be made between circular waveguides and rectangular waveguides at X-Band, which can be used for radars or satellite communication applications. The novelty of this component design comes from impedance matching between 4 rectangular waveguides operating in the fundamental mode and 1 single highly over-moded circular waveguide by means of coaxial rod and matching fins. All these are done while keeping the overall size small, compact, and lightweight.

A 52–65 GHz Frequency Quadrupler With Low Conversion Loss and High Harmonic Rejection Ratio in 28-nm CMOS

This brief presents a 52-65 GHz frequency quadrupler with low conversion loss and high harmonic rejection ratio based on 28-nm bulk CMOS process. The frequency quadrupler includes two stages balanced frequency push-push doublers (PPD) cascaded with common-gate buffers. A series LC pair is placed between the PPD and the buffer of the first stage, which not only improves the conversion gain, but also suppresses the unwanted fundamental signals. A filter-integrated matching network is designed as the output matching network to reject undesired harmonics. As a result, the proposed design exhibits advantages in conversion gain and harmonic rejection ratio. The measured peak output power is -1.8 dBm and the output power 3-dB bandwidth is 52-65 GHz when the input power is 0 dBm. The even and odd harmonics rejection ratios are better than 35 dBc and 45 dBc, respectively, which can be used in high-performance mm-Wave LO chain.

A multifunctional additive strategy to stabilize the precursor solution and passivate film defects for MA-free perovskite solar cells with an efficiency of 22.75%

Though great progress has been realized in perovskite solar cells (PSCs), there are still some thorny challenges that exist such as 1) low power conversion efficiency (PCE) and loss of stability due to the defects in the film; 2) poor reproducibility of solution-processed PSCs due to the unstable perovskite precursor solution. Here, an effective multifunctional additive, benzoyl hydrazine (BH), was developed to modify the perovskite film. The result shows that the defect of the film decreased after BH modification due to the interaction between BH and perovskite. Meanwhile, the I ions (I−) migration is also suppressed due to the weak interaction between BH and perovskite. In addition, the –NH–NH2 in BH can reduce the undesired I2 by reducing it to I−. Finally, the PCE of PSCs modified by BH achieved a PCE of 22.75%, which is one of the highest PCE of the reported MA-free PSCs. The modified device still exhibited excellent stability in different conditions.

Low-Cost Third-Harmonic Mixer for -Band Retrodirective System Applications

This letter presents a low-cost third-harmonic mixer suitable for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula> -band retrodirective systems. Measured results show that when fixing the local oscillator (LO) frequency at 35 GHz, the conversion loss (CL) below 11 dB is achieved over the radio frequency (RF) range of 100–110 GHz with intermediate frequency (IF) from dc to 5 GHz, while for the RF range of 108 GHz, the minimum CL of 6.8 dB is obtained. Therefore, the presented mixer exhibits an excellent performance with low CL in comparison with that of a normal subharmonic mixer (SHM). The isolations of RF/LO and RF/IF are improved to the level of 35 and 38 dB, respectively. The simulated and measured isolations of LO/RF are 41 and 37 dB, respectively. This mixer has properties of low LO frequencies, high isolations, and low CL; therefore, it provides a high-performance and low-cost alternative solution for the applications of retrodirective systems.

High-Efficiency D-Band Monolithically Integrated GaN SBD-Based Frequency Doubler With High Power Handling Capability

A high-efficiency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}$ </tex-math></inline-formula> -band monolithically integrated GaN frequency doubler based on a pair of antiseries four-anode planar GaN Schottky barrier diodes (SBDs) has been successfully fabricated. Unlike the traditional hybrid integrated circuit technology, the monolithic integrated circuit technology has been used in the design and fabrication of GaN SBD-based frequency doubler circuits to achieve good alignment and low conversion losses. At room temperature, the experiments show that the peak conversion efficiency reaches 17.0% at 115.6 GHz under a continuous wave (CW) driving which is a critical requirement for many practical applications. The efficiency of 17.0% is the highest efficiency of GaN SBD-based multipliers at present under CW driving mode. This monolithically integrated doubler also exhibits a broadband high efficiency characteristic of more than 4.7% (−5.58 dB from 17%) across a 10% band from 109 to 121 GHz. In addition, high CW power handling capability of the proposed frequency doubler is verified. The experiments show that the frequency doubler can endure a maximum CW input power of 0.5 W.

A high‐gain multi‐input single‐output switched quasi‐Z‐source converter for the integration of multiple renewable energy sources

AbstractAiming to integrate distinct renewable energy sources and to obtain the benefits of quasi‐Z‐source converter, voltage doubler rectifier, and switched capacitor converter, a high‐gain multi‐input single‐output switched quasi‐Z‐source converter (SqZSC) with a multi‐input high‐frequency transformer is proposed. The proposed SqZSC fed three‐phase six‐level (TPSL) micro‐inverter is designed to integrate multiple small‐scale renewable energy sources such as wind, photovoltaic systems, and fuel cells with the utility grid. Compared with the other topology of Z‐source converter, the designed converter can offer a high boost factor, low conversion losses, low voltage and current stress across the main chopping switches, and the one‐port impedance network. The design, working principle, voltage and current stress of the chopping switches, experimental results, and comparison with the other topology of ZSC are presented. Finally, the results of a 1200‐W prototype model are given to authenticate the steady‐state and dynamic performance of the proposed multi‐input single‐output SqZSC.

Progress in the torrefaction technology for upgrading oil palm wastes to energy-dense biochar: A review

The growing health and environmental concerns associated with the consumption of fossil energy sources catalyze the production of biofuels as renewable energy carriers for heat and electricity generation. Production of biofuels from biomass, being the most available renewable feedstock, is advantageous as it results in increased mitigation of GHGs (greenhouse gas) emissions. Co-firing biomass pellet in power plants is a promising way of using biomass for renewable energy generation. Among the various thermochemical conversion routes, torrefaction represents an efficient low-temperature pyrolysis technology to produce co-firing biofuel at 200–300 °C with low conversion losses. However, the current practice of using conventional heating in batch operation adversely affects oil palm torrefaction, leading to low throughput, low biomass processing rate, and poor heat transfer rate. Integration of microwave technology has emerged as a promising solution to enhance the upscaling capacity of torrefaction technology, offering higher production rates and better volumetric heat transfer. The present work critically reviews and discusses the latest developments in the torrefaction of oil palm waste to produce energy-dense biochar with reduced moisture content (for better water resistivity and durability). The use of microwave radiation as a heating method could also catalyze the torrefaction reaction with lower activation energy. In conclusion, microwave systems incorporated into continuous reactors seem to have great potential in streamlining torrefaction processes, thereby producing environmentally friendly energy.

An 8–10-GHz Low-Loss Image-Reject HTS Mixer Based on Cascaded Josephson Junctions

A 7.8-9.8-GHz low-loss high- T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> superconducting (HTS) image-reject Josephson junction mixer is presented in this letter. Image rejection is achieved using low-loss image rejection filters and a pair of parallel dual-mode resonators. Three cascaded Josephson junctions are monolithically integrated with impedance matching networks and bandpass/low-pass filters on a single chip for low loss and compactness. The implementation of series junction array increased the overall junction equivalent impedance, so that a better impedance matching is achieved. Measurement results of the novel HTS mixer showed a low conversion loss at 5.5 dB and an image-reject ratio over 30 dB within the desired frequency. The proposed cascaded junction configuration provides a new approach for impedance matching in HTS mixer designs, and the demonstrated mixer performance makes it an ideal candidate for X-band radar systems.

A 28-GHz Bidirectional Active Gilbert-Cell Mixer in 90-nm CMOS

A bidirectional active mixer based on Gilbert-cell topology is proposed and realized in 90-nm CMOS at 28 GHz. The offered mixer can achieve both the up- and down-conversion under 1-dBm local oscillator (LO) power by adjusting the Gilbert quad switch's gate bias. An IF bidirectional amplifier (IFBDA) is adapted to compensate for the conversion loss (CL) of the Gilbert quad switch. The measured peak conversion gain (CG) is -2.14/-3.28 dB at 28-GHz, and the 3-dB bandwidth is 7/6 GHz in transmit (Tx)/receive (Rx) mode. Total dc power consumption is only 8.4/6.4 mW for Tx/Rx mode under 1.2-V supply voltage. Compared with the traditional bidirectional passive mixers, this mixer demonstrates a low CL with a low LO power.

Readout Distance Enhancement of Battery-Free Harmonic Transponder

This work proposes to enlarge the maximum readout distance of battery-free harmonic transponders through a careful Schottky diode selection and a consideration of low-temperature operations. Diode SMS7621 is identified to deliver lower conversion loss (CL) of harmonic transponders based on a diode selection guide. Moreover, an analytical method for studying temperature effects on the transponder CL performance is introduced and derived with satisfactory accuracy. A diplexer inserted in the harmonic transponder design can help reduce the antenna number. To mitigate matching difficulties at both fundamental and second-harmonic frequencies, a third-order diplexer is developed to enhance its bandwidth performance. Experimental verification has shown that low-temperature operations can effectively reduce the CL of the SMS7630-based harmonic transponder, thus increasing its readout distance. Specifically, its maximum readout distance at −40 °C has increased by more than 10%, from 6.4 to 7.1 m, compared with that at +40 °C. A complete harmonic transponder based on SMS7621, with dimensions of 85 mm $\times45$ mm has reached a maximum readout distance of 8 m when the fundamental frequency is 3.5 GHz.

An Improved Bipolar Voltage Boost AC Voltage Controller With Reduced Switching Transistors

Single-stage power conversion with simple circuit arrangement is one of the attractive features of direct bipolar voltage ac-ac converters. This increases their potency in various applications that require voltage and frequency regulation. The grid voltage compensators, direct variable speed ac-ac drives, and induction heating systems require inverting and non-inverting operation of the input voltage. Their size, cost, and circuit complexity directly depend on the number of switching transistors, as the operation of each transistor requires the use of one gate drive circuit (GDC) and one isolated dc power supply (IDCPS). The size and cost of GDC and IDCPS are much larger than that of switching transistors. The use of fewer switching transistors also ensures low conversion losses and simplifies the switching schemes. Therefore, this research proposes a new ac-ac converter that is realized as a bipolar boost ac voltage controller having a low count of switching transistors. The suggested topology also eliminates the shoot-through of the input source or output filtering capacitor. The characteristics of the proposed circuit are explored through simulation results obtained through the Simulink platform. The confirmation of the simulation results is validated through the laboratory prototype.

Integrated Dipole Antenna With Bandwidth Enhancement for Terahertz Waveguide-to-CPWG Transition

In this letter, a broadband waveguide-to-coplanar waveguide with ground transition for large-chip-width substrate operating within terahertz frequencies is demonstrated. This transition adopts an integrated dipole antenna with coupling branches and disks topology. This compact transition reduces parasitic effects by wire bonding and is suitable for direct integration with terahertz monolithic integrated circuits, and it enables low energy conversion loss over a wide frequency band. The transition was fabricated on a 970 μm wide substrate by the 50 μm thick InP technology and designed for WR-4.3 standard waveguide (546 μm width). The measured results show that the bandwidth with 1 dB insertion loss per antenna is as wide as 80 GHz, and the in-band return loss is better than 10 dB.

Design of a CaAlSiN3:Eu/glass composite film: Facile synthesis, high saturation-threshold and application in high-power laser lighting

Even though CaAlSiN3:Eu2+ (CASN) is, in many regards, a highly suitable red phosphor that can be used in white light-emitting diodes, it can hardly be used in high-power laser-lighting because of its low saturation-threshold. By using CASN-based composite ceramics, it is possible to increase the threshold but new difficulties appear. These include complex and expensive synthesis, while the saturation-threshold still has room for improvement. In this study, we prepare a CASN/glass composite film, using an industry-friendly blade-coating method. The film has a high internal quantum efficiency of 79%, which suggests low conversion loss. Under 1.17 W blue laser excitation, a high luminous efficacy of 21.0 lm/W can be obtained. More importantly, the composite film shows a record-high saturation-threshold of more than 12.7 W (∼320 W/cm2) blue laser excitation. With these outstanding properties, CASN/glass composite films may open doors towards commercially viable red color converters for high-power laser-lighting applications.

A New Single-Phase Direct Frequency Controller Having Reduced Switching Count without Zero-Crossing Detector for Induction Heating System

Induction heating (IH) is an environmentally friendly solution for heating and melting processes. The required high-frequency magnetic field is accomplished through frequency controllers. Direct frequency controllers (DFC) are preferred to dual converters as they have low conversion losses, compact size, and simple circuit arrangement due to low component count. Numerous frequency controllers with complex switching algorithms are employed in the induction heating process. They have a complicated circuit arrangement, and complex control as their switching sequences have to synchronize with source voltage that requires the zero-crossing detection of the input voltage. They also have a shoot-through problem and poor power quality. Therefore, this research proposes a novel frequency controller with a low count of six controlled switching devices without a zero-crossing detector (ZCD) having a simple control arrangement. The required switching signals are simply generated by using any pulse-width-modulated (PWM) generator. The performance of the proposed topology is verified through simulation results obtained using the MATLAB/Simulink environment and experimental setup.

A low conversion loss single balanced subharmonic mixer

A new circuit topology for the design of a single balanced second-order subharmonic mixer (SHM) is proposed. In the proposed topology, it is not necessary for the radio frequency (RF) and local oscillator (LO) signal to be within 15% frequency difference. Thus, the limitation of a conventional rat-race mixer has been alleviated. Moreover, it shows very low conversion loss, high LO-to-RF, LO to intermediate frequency (IF), and 2LO-to-RF port isolations. The measured minimum down conversion loss is 5.8 dB at 13 GHz and remains below 7.65 dB over the 2 GHz RF operational band 12-14 GHz for a fixed IF of 550 MHz. Measured LO-to-RF and LO-to-IF port isolations are better than −40 dB over the entire operational band. The 2LO-to-RF isolation is more than −62 dB which is extremely necessary for a second harmonic mixer where 2LO and RF frequency are close to each other. The input 1-dB compression point is measured to be −1 dBm.

A New Single-Phase AC Voltage Converter With Voltage Buck Characteristics for Grid Voltage Compensation

Voltage sags and swells are the major problems of the power distribution system that arise due to uneven distribution of the single-phase and nonlinear loads. They severely degrade the power quality and may cause the failure of the equipment at the user's side. The voltage sag and swell issues are compensated by operating the AC voltage controllers with bipolar voltage gain characteristics. In these converters, high switching voltage and current, and a large number of switching devices are the main issues that cause unwanted power losses and result in reduced efficiency of the system. High voltage stresses may cause device failure due to the increase in dv/dt rating. The large count of switching devices results in high cost and high conversion losses. So here, we propose a novel AC converter with fewer switching devices that reduces switching voltage and current to have low conversion losses. The amplitude of the output is governed through the direct PWM control (DPWM) of one switch that controls the switching state of the other switch indirectly called indirect PWM control switch (IDPWM). The detailed analysis of the proposed converter is carried out to compare its performance with the existing converters. MATLAB/Simulink environment-based simulation results are proved through the experimental results obtained by developing a hardware prototype.

A 200–240 GHz Sub-Harmonic Mixer Based on Half-Subdivision and Half-Global Design Method

For the terahertz harmonic mixer, a design model based on Half-Subdivision and Half-Global Design Method (HS-HGDM) with a single functional unit is proposed. The single functional unit circuit of the mixer, such as LO or IF Low Pass Filter (LPF), is designed by Subdivision Design Method (SDM), and the rest circuits of the mixer are designed by Global Design Method (GDM). The harmonic mixer based on this model is characterized by simple circuit structure, low conversion loss, small circuit size and high stability. In this paper, an improved Compact Suspended Micro-strip Resonators (CSMRs) filter is developed for the IF part of sub-harmonic mixer. The remaining circuits consist of some basic transmission units, such as the High-Z Low-Z impedance Transmission Lines (H-Z L-Z TLs) applied for main circuit, and full/reduced height WR4.3/WR8 applied for providing RF/LO signal. In RF frequency range 200–240 GHz, a Single Sideband (SSB) conversion loss of 7.36±0.76 dB operating at IF frequency 1.8 GHz, and a Double Sideband (DSB) noise temperature below 1034 K with the LO power of 2–5 mW and the LO frequency of 107 GHz were achieved. This broadband sub-harmonic mixer operates at room temperature, which makes it applicable to sub-millimeter wave or terahertz wireless communication systems and imaging inspection systems.

A Wideband Subharmonic Mixer With Low Conversion Loss and High Port-to-Port Isolations

A design of a diode based wideband subharmonic mixer (SHM) with low conversion loss and high port-to-port isolations is reported. To achieve low conversion loss, for a given diode, the radio frequency (RF) and intermediate frequency (IF) signals at the respective port should remain unattenuated over the frequency range of interest. At the same time, it has to reject unwanted signals over a wide bandwidth. The excellent wideband bandstop filtering behavior of signal interference technique is exploited for this purpose. The mixer is designed to operate over the RF band 8.5-11.5 GHz. The local oscillator (LO) frequency is tuned to keep IF fixed at 200 MHz. Measured minimum conversion loss is obtained as 6.05 dB while the theoretical limit of conversion loss for the chosen diode is 4.68 dB. Measured LO-to-RF and 2LO-to-RF isolations are better than −30 dB (maximum −50 dB) and −59 dB (maximum −73 dB), respectively, over the entire operational band. Large signal measurements show that the 1-dB compression point is −1 dBm and the third order intercept point is 10 dBm. Simplicity in circuit topology is another significant feature.