Search Results (17)

This work describes the design and experimental testing of a low-noise amplifier (LNA) fabricated on a printed circuit board (PCB) and operating near 2 GHz. The amplifier uses a discrete bipolar junction transistor (BJT) together with fully distributed microstrip matching networks without relying on lumped matching components. The main design goal is to obtain stable operation with low noise figure and moderate gain over a wide frequency range while keeping the circuit tolerant to layout parasitics and fabrication variations. Circuit-level simulations are performed using AWR Microwave Office and are followed by full-wave electromagnetic simulations in Sonnet Software to account for layout-dependent effects. A prototype is fabricated on a 60-mil Rogers RO4003C substrate and characterized through S-parameter, noise-figure, and linearity measurements. Measured results show a gain of approximately 13.84 ± 1 dB over the 1.75–2.25 GHz frequency range, with a minimum noise figure of 1.615 dB at 2 GHz. Stable operation is maintained across the entire band, and the measured 1 dB gain compression point is approximately 0.5 dBm. The results demonstrate that a fully distributed microstrip matching approach provides a practical and reproducible PCB-based LNA solution for sub-6-GHz receiver front-end applications. Full article

Wireless power transfer via RF/microwave rectifiers has emerged as a sustainable solution to the energy requirements of low-power devices. In this study, a novel four-parallel-shunt-diode ultra-wideband rectifier is proposed to enable wireless power transfer in the sub-6-GHz 5G bands. The proposed circuit maintains a power conversion efficiency (PCE) above 50% across the 1.6–5.1 GHz frequency range at 10 dBm input power and also achieves an efficiency above 50% at 3 GHz for input powers between 1 dBm and 16 dBm. Designed and fabricated on a low-cost FR4 substrate, the rectifier achieves a maximum power conversion efficiency of 76% at 2.9 GHz with a 10 dBm input power. Furthermore, a wideband impedance analysis is performed, taking into account the packaging parasitics of the HSMS-2860 diodes used in the study. Despite the use of a lossy substrate such as FR4, the proposed four-parallel-shunt-diode topology improves impedance stability and provides impedance matching over both a wide input-power range and a wide frequency band when compared with single- and double-diode structures reported in the literature. Full article

Massive Multiple-Input Multiple-Output (MIMO) systems with hundreds or thousands of antenna elements are fundamental to next-generation wireless networks, promising unprecedented spectral efficiency through spatial multiplexing and beamforming. However, the computational burden of channel state information (CSI) acquisition and processing scales dramatically with array size, creating a critical bottleneck for practical deployments. While previous works demonstrated that Fast Fourier Transform (FFT)-based beamspace processing can exploit the inherent angular sparsity of wireless channels to compress CSI feedback, the digital implementation requires intensive computations that become prohibitive for ultra-large arrays. This paper presents an analog alternative using Butler matrices—passive beamforming networks that realize the Discrete Fourier Transform in hardware—combined with RF switching circuits to select only dominant angular components. We provide a comprehensive analysis of Butler matrix architectures for arrays up to 32 × 32 elements, characterizing insertion losses across different technologies (microstrip, substrate-integrated waveguide, and waveguide) and operating frequencies (10–30 GHz). The proposed system incorporates parallel power sensing with Winner-Take-All circuits for sub-microsecond beam selection, drastically reducing the number of active RF chains. Full-wave simulations and capacity evaluations at 12 and 30 GHz demonstrate that the Butler-based approach achieves comparable performance to FFT methods while offering significant advantages in power consumption and processing latency. For a 256 × 256 array, FFT computation requires 0.36 ms compared to near-instantaneous analog processing, making Butler matrices particularly attractive for real-time massive MIMO systems. These findings establish Butler matrix front-ends as a practical pathway toward scalable, energy-efficient beamspace processing in 6G networks. Full article

In this study, a single-pole double-throw (SPDT) switch for Sub-6 GHz application is designed. In particular, a shunt inductor is connected to the antenna port of the switch for ESD (electrostatic discharge) protection in RF (radio frequency) front end module. The shunt inductor not only serves as an ESD protection device, but also serves as a component of a parallel resonance circuit to suppress insertion loss of the switch. In addition, in order to secure the power handling capability, transistors turned off in the transmit (Tx) mode are implemented as quadruple-gate transistors. An SPDT switch is fabricated using GaAs pHEMT provided in the 500 nm GaAs BiFET process to verify the feasibility of the proposed switch structure. The operating frequency is set from 3 GHz to 5 GHz. The insertion loss and isolation measured in the Tx mode are lower than 0.35 dB and higher than 31.6 dB, respectively. The insertion loss and isolation measured in the Rx mode are lower than 0.32 dB and higher than 33.9 dB, respectively. The chip size including test pads is 0.890 × 0.875 mm². Full article

Millimeter-wave radar is emerging as a key sensor technology not only for autonomous driving but also for various industrial applications, such as vital sign monitoring and structural displacement sensing using millimeter-wave FMCW radar, which must detect extremely small displacements on the sub-micron scale. Accurate displacement measurements fundamentally rely on obtaining precise intermediate frequency (IF) phase data over slow time (i.e., chirp-to-chirp intervals or pulse repetition time) generated by the radar sensor system. In this study, we developed a millimeter-wave FMCW radar sensor for displacement sensing using a 77–81 GHz radar transceiver MMIC (Monolithic Microwave Integrated Circuit) and evaluated its accuracy and precision through a series of experiments. First, we assessed the MMIC’s phase performance under static conditions using a rigid RF waveguide, and second, we measured a vibrating target using an industrial vibration shaker as a reference. The experiments demonstrated a maximum accuracy error of +0.359 degrees (1.907 μm displacement) and a maximum 3-sigma precision of ±0.358 degrees (±1.180 μm displacement), validating the feasibility of using millimeter-wave radar to measure very small displacements. Full article

We demonstrate absorber-free passive and hybrid mode-locking at sub-GHz repetition rates, using a hybrid integrated extended cavity diode laser operating near 1550 nm. The laser is based on InP as a gain medium and a Si₃N₄ waveguide feedback circuit. Absorber-free Fourier domain mode-locking with ≈15 comb lines at around 0.2 mW total power is achieved with repetition rates around 500 MHz, using three highly frequency-selective micro-ring resonators that extend the on-chip cavity length to 0.6 m. To stabilize the repetition rate, hybrid mode-locking is demonstrated by weak RF modulation of the diode current. The RF injection reduces the Lorentzian linewidth component from 8.9 kHz to a detection-limited value of around 300 mHz. To measure the locking range of the repetition rate, the injected RF frequency is tuned with regard to the passive mode-locking frequency and the injected RF power is varied. The locking range increases approximately as a square-root function of the injected RF power. At 1 mW injection, a wide locking range of about 80 MHz is obtained. We also observe the laser maintaining stable mode-locking when the DC diode pump current is increased from 40 mA to 190 mA, provided that the cavity length is maintained constant with thermo-refractive tuning. Full article

A novel 10-Watt-Level high-power microwave rectifier with an inverse Class-F harmonic network for microwave power transmission (MPT) is presented in this paper. The high-power microwave rectifier circuit comprises four sub-rectifier circuits, a 1 × 4 power divider, and a parallel-series dc synthesis network. The simple inverse Class-F harmonic control network serves dual roles: harmonic control and impedance matching. The 1 × 4 power divider increases the RF input power fourfold, reaching 40 dBm (10 W). The parallel-series dc synthesis network enhances the resistance to load variation. The high-power rectifier circuit is simulated, fabricated, and measured. The measurement results demonstrate that the rectifier circuit can reach a maximum RF input power of 10 W at 2.45 GHz, with a maximum rectifier efficiency of 61.1% and an output dc voltage of 23.9 V, which has a large application potential in MPT. Full article

Monitoring the tortoise Chelonoidis chilensis in the wild, currently in a vulnerable state of conservation in southern Argentina, is essential to gather movement information to elaborate guidelines for the species preservation. We present here the electronic circuit design as well as the associated firmware for animal monitoring that was entirely designed by our interdisciplinary research team to allow the extension of device features in the future. Our development stands out for being a family of low-cost and low-power devices, that could be easily adaptable to other species and contexts. Each device is composed of a sub 1 GHz radiofrequency IoT-compatible transceiver, a global navigation satellite system (GNSS) receiver, a magnetometer, and temperature and inertial sensors. The device does not exceed 5% of the animal’s weight to avoid disturbance in their behavior. The board was designed to work as a monitoring device as well as a collecting data station and a tracker, by adding only small pieces of hardware. We performed field measurements to assess the autonomy and range of the radiofrequency link, as well as the power consumption and the associated positioning error. We report those values and discuss the device’s limitations and advantages. The weight of the PCB including battery and GNSS receiver is 44.9 g, its dimensions are 48.7 mm × 63.7 mm, and it has an autonomy that can vary between a week and a month, depending on the sampling rates of the sensors and the rate of the RF signal and that of the GNSS receiver. The characterization of the device parameters will favor the open use of this development by other research groups working on similar projects. Full article

Radio-frequency (RF) energy harvesting (EH) is emerging as a reliable and constantly available free energy source. The primary factor determining whether this energy can be utilized is how efficiently it can be collected. In this work, an RF EH system is presented. More particularly, we designed a dual-band RF to DC rectifier circuit at sub-6 GHz in the 5G bands, able to supply low-power sensors and microcontrollers used in agriculture, the military, or health services. The system operates at $3.5$ GHz and 5 GHz in the 5G cellular network’s frequency band FR1. Numerical results reveal that the system provides maximum power conversion efficiency (PCE) equal to 53% when the output load (sensor or microcontroller) is $1.74$ kΩ and the input power is 12 dBm. Full article

In this paper, a high-performance 0.34 THz sub-harmonic mixer combining two-stage reduced matching technology with an improved active circuit model is established and analyzed. The mixer’s improved active circuit model is realized by decomposing passive functional models into basic transmission line units and their impedance matching and filtering are realized through automatic optimization. The improved active circuit model takes out the RF (radio frequency) transition model separately to set an optimization goal instead of operating directly in the mixing circuit. Compared with traditional active circuit models in the SDM (subdivision design method) and GDM (global design method), it provides a massive optimization space, larger working bandwidth, and better results. In the RF frequency range of 320–360 GHz, the SSB (single sideband) conversion loss of the 0.34 THz sub-harmonic mixer is below 9.5 dB and the RF return loss is less than 12 dB. Full article

The monolithic microwave integrated circuit (MMIC) power amplifiers serve an essential and critical role in RF transmit/receive (T/R) modules of phased array radar systems, mobile communication systems and satellite systems. Over recent years, there has been an increasing requirement to develop wideband high-efficiency MMIC high power amplifiers (HPAs) to accommodate wideband operation and reduce power consumption. This paper presents a wideband high efficiency MMIC HPA for Sub-6-GHz applications using a 0.25-μm gate-length D-mode GaN/SiC high electron mobility transistor (HEMT) process. The amplifier consists of two stages with two HEMT cells for the driver stage and eight HEMT cells for the power stage. To obtain a flat gain while maintaining the wideband characteristic, a gain equalization technique is employed in the inter-stage matching circuit. Meanwhile, a low-loss output matching network is utilized to ensure high efficiency. The fabricated HPA occupies a compact chip area of 14.35 mm² including testing pads. Over the frequency range of 2–6 GHz, measured results of this HPA show a saturated continuous wave (CW) output power of 44.4–45.2 dBm, a power added efficiency (PAE) of 35.8–51.3%, a small signal gain of 24–25.5 dB, and maximum input and output return losses of 14.5 and 10 dB, respectively. Full article

The paper presents a computationally efficient and accurate numerical approach to evaluating RF–DC power conversion efficiency (PCE) for energy harvesting circuits in the case of multi-tone power-carrying signal with periodic envelopes. This type of signal has recently received considerable attention in the literature. It has been shown that their use may result in a higher PCE than the conventional sine wave signal for low to medium input power levels. This reason motivated the authors to develop a fast and accurate two-frequency harmonic balance method (2F-HB), as fast PCE calculation might appreciably expedite the converter circuit optimization process. In order to demonstrate the computational efficiency of the 2F-HB, a comparative study is performed. The results of this study show that the 2F-HB significantly outperforms such extensively used methods as the transient analysis (TA), the harmonic balance method (HB), and the multidimensional harmonic balance method (MHB). The method also outperforms the commercially available non-linear circuit simulator Keysight ADS employing both HB and MHB. Furthermore, the proposed method can be readily integrated into commonly used commercially available non-linear circuit simulation software, including the Keysight ADS, Ansys HFSS, just to name a few—minor modifications are required. In addition, to increase the correctness and reliability of the proposed method, the influence of PCB is considered by calculating Y parameters of its 3D model. The widely employed voltage doubler-based RF–DC converter for energy harvesting and wireless power transfer (WPT) in sub-GHz diapason is chosen to validate the proposed method experimentally. This RF–DC converter is chosen for its simplicity and capability to provide sufficiently high PCE. The measurements of the PCE for a voltage doubler prototype employing different multi-tone waveform signals were performed in laboratory conditions. Various combinations of the matching circuit element values were considered to find the optimal one in both—theoretical model and experimental prototype. The measured PCE is in very good agreement with the PCE calculated numerically, which attests to the validity of the proposed approach. The proposed PCE estimation method is not limited to one selected RF–DC conversion circuit and can also be applied to other circuits and frequency bands. The comparison of the PCE obtained by means of the proposed approach and the measured one shows very good agreement between them. The PCE estimation error reaches as low as 0.37%, and the maximal estimation error is 32.65%. Full article

(1) Background: This work presents a high-efficiency, high sensitivity, compact rectifier based on a dual-band impedance matching network that employs a simple and straightforward T-matching circuit, for sub-1 GHz license-free applications. The development of a low-cost RF energy harvester dedicated to the ISM bands is introduced. The proposed rectifier design is optimized to operate at the sub-GHz frequency bands (0.9 to 2.4 GHz), specifically those at the ISM 900 and 2400 MHz. The motivation for this band is due to the low attenuation, well-known fundamental electromagnetic theories and background, and several wireless communications are emitting at those bands, such as RFID (2). Methods: The rectifier design is based on a simple, balanced single-series diode connected with a T-matching circuit. The dual-band performance is achieved by deploying reactive elements in each branch. The full mathematical analysis and simulation results are discussed in the manuscript. (3) Results: The rectifier can achieve a 80 MHz bandwidth around 920 MHz frequency and 200 MHz around the higher band 2.4 GHz. The resultant conversion efficiency level is maintained above 45% at both bands with a peak efficiency reaches up to 70% at the higher band. The optimum terminal load attached to the circuit at which the peak efficiency is achieved, is given as 4.7 k$\Omega$. (4) Conclusion: Due to the compactness and small footprint, simple design, and simple integration with microwave circuits, the proposed rectifier architecture might find several potential applications in wireless RF energy harvesting. Full article

Controlling Radio Frequency (RF) signals through switching technology is of interest to designers of modern wireless platforms such as Advanced Wireless services (AWS) from 2.18 GHz–2.2 GHz, mid-bands of sub-6 GHz 5G (2.5 GHz and 3.5 GHz), and 4G bands around 600 MHz/700 MHz, 1.7 GHz/2.1 GHz/2.3 GHz/2.5 GHz. This is because certain layout efficiencies can be achieved if suitable components are chosen to control these signals. The objective of this paper is to present a new model of an RF switch denoted as a Magnetostatic Responsive Structure (MRS) for achieving reconfigurable operation in 4G/5G antennas. In particular, the ABCD matrices of the MRS are derived from the S-parameter values and shown to be a good model from 100 kHz to 3.5 GHz. Furthermore, an overall agreement between simulations, analytical results, and circuit model values are shown. Full article

A compact broadband monolithic sub-harmonic mixer is presented in a 70 nm GaAs Technology for millimeter wave wireless communication application. The proposed mixer adopts a novel multi-line coupler structure; where the two-sided coupling energy of radio frequency (RF) and local oscillation (LO) signals are both collected and efficiently feed to anti-parallel diode pair (APDP) topology; resulting in broadband performance and compact chip size. As a comparison in the same circuit configuration; the five-line coupler can expand the bandwidth of the existing three-line coupler by 85% and reduce the area by 39.5% when the central frequency is 127 GHz. The measured conversion gain is −16.2 dB to −19.7 dB in a wide operation frequency band of 110–170 GHz. The whole chip size is 0.47 × 0.66 mm² including test pads. The proposed mixer exhibits good figure-of-merits for D-band down-converter applications Full article