Qianyin Xiang

This letter leverages the advantages of substrate-integrated suspended line (SISL) and photonic crystals to propose a novel third-order cross-coupled bandpass filter (BPF) characterized by compactness and self-packaging. By altering the structural size of the photonic crystal, the slow wave and bandgap effects can be flexibly adjusted in the SISL structure. An effective balance can be achieved among compact size, filtering performance, and insertion loss—since reducing size tends to significantly increase loss. Electrical and magnetic couplings serve as cross-coupling mechanisms to realize a cascaded trisection (CT) topology, which introduces a transmission zero (TZ) on the left of the passband. To validate this design, a compact third-order cross-coupled BPF with a center frequency of 4.658GHz was fabricated and measured. The results show good agreement with simulations and demonstrate an upper out-of-band rejection exceeding 30 dB. The overall circuit size is $0.39\lambda _{\text {g}} {\times } 0.22\lambda _{\text {g}} \times 0.06\lambda _{\text {g}}$ .

A tunable filtering attenuator based on lossy-tuned multimode resonators is proposed in this letter, featuring wide tunable attenuation range with low minimum insertion loss, improved in-band flatness, and high frequency selectivity. The design consists of one lossy-tuned triple-mode resonator coupling with two lossy-tuned dual-mode resonators. The improved in-band flatness and in-band matching at high attenuation levels are implemented through fine-tuned lossy resonator modes using p-i-n diodes. The mechanism behind high-attenuation flat passband and switch-off function is clarified. The p-i-n diode equivalent circuits and shunt capacitors are used to achieve circuit optimization and miniaturization. A prototype was fabricated and measured, demonstrating a tunable attenuation range of 1.14–41.83 dB, a 77.7% fractional bandwidth at 2 GHz, and a switch-off capability with over 34.8-dB in-band suppression.

The contradiction between achievable sum rate enhancement and limited antenna aperture in base stations has prompted the exploration of the unconventional antenna architectures. We propose a novel heterogeneous antenna array architecture with uniform element spacing that leverages multiple elements with distinct directional patterns to reduce channel correlation and minimize mutual interference in multi-user environments. Unlike a regular array consisting of identical elements, this approach increases design flexibility while maintaining compatibility with digital beamforming techniques, without adding system costs. In such a framework, the joint configuration optimization problem is formulated by considering both the achievable sum rate and coverage performance of base stations, which is numerically solved to obtain a near-optimal array configuration within a prescribed optimality gap. Numerical results validate the superiority of the heterogeneous array over the regular array, with up to a 24.7% improvement in sum rate in high signal-to-noise ratios cases while maintaining the same coverage performance considering user scheduling. The same heterogeneous array (with fixed array topology) demonstrates performance gains across multiple channel environments as compared to the regular array. This environmental adaptability arises from the irregular element patterns, which spatially decorrelate channels by improving distinct angular resolvability for close-located users. These findings suggest that heterogeneous arrays offer a promising avenue for improving baseband communication with limited aperture constraints.

In this letter, a novel reconfigurable filter with multifunction of continuous tunable frequency, bandwidth (BW), and attenuation is proposed. The tunable filter is integrated designed based on a fully tunable filtering coupling structure with external quality factor (Q _e ) control and a tunable attenuation unit with impedance transformation capability. The fully tunable filtering coupling structure is deigned using terminal varactor loaded half‐wavelength microstrip resonator with tunable center frequency and coupling coefficient. Adjustment of Q _e is realized through the addition of a varactor at the feedline port. Tunable attenuation is achieved by loading PIN diodes through a coupling structure. To improve the efficiency of impedance transformation, an asymmetric structure is employed. The performance degradation of the bandwidth and center frequency due to the tunable attenuation can be compensated by the fully tunable filtering coupling structure. The measurements show that the reconfigurable filter can be tuned from 0.99 to 1.61 GHz with tunable attenuation and bandwidth. The attenuation can be tuned over a range of 30.6 dB at 1.4 GHz, and the fractional bandwidth (FBW) can be tuned from 10% to 30% at 1.3 GHz.

A novel voltage-controlled tunable filtering attenuator is proposed based on tunable lossy resonators and lossy coupling, featuring wide attenuation tunable range, improved in-band flatness, and bandwidth stability. The proposed component is implemented through an eighth-order ladder-type microstrip filter tuned by p-i-n diodes. The symmetrical feature of the component enables comprehensive analysis through odd- and even-mode methods, facilitating precise parameter optimization. A proof-of-concept prototype has been fabricated and measured. The measurement results demonstrate an attenuation tuning range from 4.4 to 50 dB while maintaining a flat passband of 907 MHz (±7.4%) or 46.9% (±3.2%) at 1.93 GHz and show the switch-off ability of in-band suppression of 53–74 dB. The multifunctional integration of filter, voltage-controlled attenuation, and switch is achieved.

The tradeoff between the unloaded quality factor (Q_u) and resonant frequency tunable range of novel planar integrated switchable and tunable resonator is studied. The novel switchable and tunable resonators are designed based on quarter-wavelength resonator with floating strip loaded by varactor diode and PIN diode, and continuously switchable tuning characteristics of the resonant frequency is modeled and investigated. A reconfigurable bandpass filter with continuously tunable frequency and stable bandwidth based on the switchable and tunable resonator with improved Q_u is designed, fabricated and measured. The developed component demonstrates a tuning range of 1.05-2 GHz with a typical bandwidth of 124 MHz, and a minimum insertion loss of 1.8 dB.

This letter introduces a group delay controller (GDC) based on reflective tunable filter with tunable frequency and tunable group delay. The wideband nonlinear conversion of the reflective low-pass delay network to the reflective bandpass delay network was studied, and the deterioration of tunable group delay response was analyzed. Asymmetric tuned reflective topology with self-coupling coefficients was used to compensate for the flatness of the in-band group delay. As a demonstration, a reflective tunable group delay circuit was designed based on tunable quarter-wavelength microstrip resonator and feeding network with tunable external quality factor ( $Q_{e}$ ). The measurements show that the GDC can be tuned from 8 to 20 ns, with a tunable center frequency from 0.8 to 1 GHz.

A novel class-E rectifier with quasi-constant transconductance (QC-G_m) is proposed. The operation mechanism of the class-E QC-G_m rectifier is investigated, and the transconductance is calculated. The rectifier exhibits zero-voltage switching (ZVS) over a wide input and output range. The QC-G_m performance of a designed 40 mS rectifier is verified in a 6.78 MHz wireless power transfer link as demonstration. The rectifier is driven by constant voltage operation mode LCC-LCC network and class-E inverter, with unity overall dc–ac driving gain. The calculation matches the simulation, and the measurement shows that the output current is 0.96 A (±3.8%) under 25 V input voltage and 1–20 Ω loads.