Microwave and Optical Technology Letters最新文献

A 47–52-GHz power amplifier (PA) Microwave Monolithic Integrated Circuit (MMIC) with silicon carbon (SiC)-based gallium nitride (GaN) was reported in this work. The circuit solution gives particular consideration to the loss of matching the output matching network. In pulse conditions, the PA can reach a maximum saturated output power of 43 dBm (20 W) with typical gain values of 18 dB and power-added efficiency of 21%. The output power at −1 dB gain compression ($��P_{�1�d�B�}�$) is 40.2 dBm, and the power density is up to 3.36 W/mm in the active periphery under the drain voltage of 24 V. The chip is compact with an area of 5.6 × 3.7 mm². This PA achieves higher output power in comparison to the reported PA MMIC.

This article presents an ultrawideband (UWB) bandpass filter (BPF) using integrated passive device technology on a GaAs substrate. This bandpass filter uses a multistage coupled line to achieve an ultrawide passband. The filter with a 3 dB fractional bandwidth can achieve a UWB of 106.1% (11.8–38.5 GHz). Introducing short-circuit capacitors and two open microstrip lines between coupling lines achieved two transmission zeros on both sides of the passband and excellent frequency selectivity. Furthermore, to improve impedance matching performance within the ultrawide passband, a step impedance resonator (SIR) structure was adopted for the coupling line. To demonstrate the working mechanism of the proposed BPF, an LC equivalent circuit model was proposed and analyzed to investigate transmission poles and zeros. The suggested filter was fabricated into a small size of 1.4 × 0.85 mm². According to the measurement results, the filter's insertion loss in the 13–34 GHz range was less than 2 dB, and its return loss exceeded −12 dB. The improved performance of the suggested filter was validated by the consistency between simulation results and measured findings.

The tunneling effect of an epsilon-near-zero (ENZ) is exploited to fulfill a narrowband large group delay by using a compact half-mode substrate integrated waveguide structure built on thin substrate. The ENZ channel possesses a finite input impedance at the tunneling frequency point, and the finite input impedance can be matched to the final I/O port simply by a quarter wavelength impedance transformer. Thus, the enhanced integrability is realized in a planar form in the proposed circuit comparing to the conventional waveguide ENZ channel. Meanwhile, in the real ENZ channel, the effective impedance is observed to be close to 50 Ω, so that the ENZ can be connected with 50 Ω microstrip directly, which has been experimentally validated. The final measured net group delay is 1.36 ns at 3.08 GHz with 3.6 dB insertion loss, and the proposed method provides an alternative for the group delay engineering.

This paper presents an innovative and condensed blueprint for an ultra-wideband (UWB) printed monopole antenna, aiming to augment bandwidth and achieve dual band-stop capabilities, all while accounting for the impact of the human body model on stop bands. The proposed design showcases a square radiating patch situated on the top layer of the substrate, complemented by a ground plane etched on the underside, integrating two sets of adapted U-shaped slots. Such a configuration delivers a broad operational fractional bandwidth that surpasses 132%. Within our design, a modified C-shaped slot in the radiation patch creates the first band-stop property, while a pair of modified F-shaped slots etched in the radiation patch generates the second stop-band property. Measuring 12 mm × 18 mm × 0.8 mm, the antenna offers a compact form factor, broad bandwidth, cost-effectiveness, omnidirectional radiation patterns within the H-plane and acceptable behavior for using in In-body microwave applications.

GaN high electron mobility transistor (HEMT)-based low noise amplifiers (LNAs) are an integral part of microwave receiver systems to enhance signal-to-noise ratio (SNR). The noise of LNA itself becomes critical for systems requiring high SNR, such as imaging and satellite communication systems. This paper discusses the design of a three-stage LNA operating at the X-band in the frequency range of 8.0–12.0 GHz. The amplifier's design and small signal, noise, and linearity characterizations are discussed. Stagewise analysis for gain, noise figure (NF), and matching network losses at the design stage results in achieving promising results. The proposed LNA provides a gain of 23.2 dB with $��\pm �\; � �\; �1.0�$ dB gain ripple. Its NF is below 1.5 dB, output power at 1 dB gain compression is 16.4 dBm, and third-order intercept point is 24.7 dBm at 10 GHz. LNA's survivability is validated to input stress as high as 42 dBm. This LNA is the best reported NF and survivability combination in the 8.0–12.0-GHz frequency range. The reverse recovery time of LNA is measured under two different pulse conditions, and it has been shown that LNA has better recovery times for lower pulse width signals. This LNA finds its applications in radars and satellite communication systems.

This study examines the high-power microwave (HPM) jamming effect on software-defined radio (SDR). Following theoretical analysis and formula derivation of the single-tone jamming, the HPM jamming effect is validated using an SDR platform. Jamming is relatively easily achieved when the jamming signal falls within the communication system's frequency band. For out-of-band signals, a higher jamming signal ratio is needed, with the receiving front-end device's nonlinearity causing the jamming. This study highlights the susceptibility of broadband receivers to HPM jamming, demonstrating that even out-of-band threats cannot be disregarded in wideband receiver designs for strong signals such as HPM.

This letter presents a new circularly polarized (CP) active antenna for global navigation satellite systems (GNSS) operating in the L1-band (1.164–1.28 GHz) and L2-band (1.525–1.615 GHz). The active antenna consists of a passive antenna and a two-channel low-noise amplifier (LNA) circuit. To achieve wideband coverage of the L1/L2 bands while maintaining a low profile, a new electroplating process is utilized in fabricating the passive antenna. Additionally, to realize CP performance, the passive antenna is sequentially fed by four ports with a wideband feeding network. To minimize phase variations, a 90° phase shifter loaded with open-short-stub is integrated into the feeding network. Furthermore, to improve noise immunity, out-of-band rejection, and amplify GNSS signals, the LNA circuit cascades two-stage dielectric bandpass filters and three-stage LNAs. Consequently, the circuit features a low noise figure of below 1.65 dB, a maximum out-of-band rejection level of 60 dB, and a stable active gain of 30 dB. The performance of the active antenna is evaluated in an outdoor open field using a GNSS receiver.

In this article, we propose a set of new expressions of four noise parameters for InP high electron mobility transistor (HEMT) devices based on PRC noise equivalent circuit model. The effects of gate-to-drain capacitance, drain-to-source conductance as well as extrinsic resistances have been taken into account. High consistency between measured and modeled noise parameters for 70 nm HEMT with 2 × 30 μm gate width in the frequency range 8–50 GHz are given by the expressions. Great usability is demonstrated for determination of small signal and noise model parameters extraction.

In this paper, a novel wideband circularly polarized (CP) array antenna is proposed. The array element is composed of four driven patches, four parasitic patches, and a loop feeding structure. On the basis of the array element structure, 1 × 2 and 2 × 2 arrays with shared patches are formed separately. Compared with the traditional structure, the volume of the 1 × 2 array antenna which only shares the patches in the x direction is reduced by 15%, and the volume of the 2 × 2 array antenna which shares the patches in the x and y directions is further reduced by 28%. The cleverness of this method is that it can keep the impedance bandwidth almost unchanged. To validate the simulated results, antenna prototypes are fabricated and measured. The results of the measurements demonstrate that the impedance bandwidths of the 1 × 2 and 2 × 2 array antennas are 27.2% (5.40–7.10 GHz) and 35.7% (5.22–7.49 GHz), respectively, and the 3 dB axial ratio (AR) bandwidths are 22.7% (5.31–6.67 GHz) and 25.4% (5.47–7.06 GHz), respectively. In addition, the measured data show that the 1 × 2 array exhibits a peak gain of 11.1 dBic, and the 2 × 2 array achieves a peak gain of 12.6 dBic. Both of them achieve a flat gain with a maximum ripple of less than 1.3 dB over the whole operating band.

This letter proposes a novel four-degrees of freedom (4-DOFs) antenna for 5.8 GHz wireless local area network band communications. The proposed antenna realizes 4-DOFs with a low profile (0.11λ), which is composed of ±45°-polarized dipole (DP), an artificial magnetic conductor (AMC) reflector, and a dual-polarized slot-loaded microstrip antenna (MA). The whole size of the proposed antenna is 83 mm × 83 mm × 5.9 mm (1.6λ × 1.6λ × 0.11λ). The DP is printed on the substrate with the wideband characteristic, and the MA operates at TM₅₀ mode. The AMC reflector operating for the DP is designed for the low profile, causing the low isolations between the DP and the MA. The broadside radiation with 4-DOFs is first reported. The envelope correlation coefficients are lower than 0.07, and the DOFs are 3.75. The measured results are in accord with the simulated results.