Yi Wu

This letter proposes a highly compact hybrid-mode diplexer based on the metal-integrated suspended line (MISL) technology. By embedding nonresonant nodes (NRNs) into suspended patch resonators, independently controllable transmission zeros (TZs) are generated to improve the interchannel isolation. A double-sided dual-mode metal-integrated waveguide (MIW) is employed as the common junction, which facilitates a seamless mode transition between the TE mode of the waveguide resonator and the TM mode of the patch resonator, synergizing the spatial compactness of suspended patch resonators with the high quality-factor of MIW resonators. Consequently, mode-conversion losses are effectively suppressed while preserving a miniaturized footprint. For validation, an X-band diplexer prototype was designed and fabricated. Experimental measurements reveal dual-channel operation at center frequencies of 10.36 and 12.28 GHz, with −15-dB reflection bandwidths of 9.31% and 8.91%, respectively. The realized minimum insertion losses of two channels are 0.85 and 0.77 dB, respectively, alongside an interchannel isolation exceeding 39 dB. This work provides an effective solution for the design of low-loss, high-isolation, and miniaturized diplexers.

In modern RF and microwave systems, the electromagnetic environment is increasingly congested. Demand for massive data throughput and ultra-high-resolution sensing has driven systems to higher frequency bands. Beyond 30 GHz (subterahertz and above), dielectric loss becomes the primary bottleneck limiting system noise figure improvement and power efficiency. At these frequencies, traditional planar transmission lines, such as microstrip lines and substrate-integrated waveguides, degrade significantly due to increased dielectric loss and radiation leakage. Traditional metal waveguides offer excellent power-handling capability and near-zero dielectric loss. However, they are highly dependent on high-precision computer numerical control milling, resulting in bulky, heavy, high-cost structures that are incompatible with miniaturization of modern satellite payloads and mobile terminals.

This letter presents a W-band (75–110 GHz) frequency tripler using metal-integrated suspended line (MISL) technology. The entire tripler device is designed and fabricated from five layered metal sheets, with the antiparallel GaAs Schottky diode mounted by a flip chip on the central metal layer. The tripler’s matching circuit is fabricated on the same metal layer, with a small size accomplished via vertical connections of input and output. In addition, the connection holes of the UG-387 flange are positioned on each layer of the metal sheet, facilitating self-packaging. The tripler prototype has been fabricated by precise and cost-effective metal etching. The measured results indicate that the tripler’s maximum output power is 7.7 dBm, reached with 21.5 dBm of input power at 104 GHz. This approach achieves low cost, miniaturization, and high performance.

This work suggests using low-loss beam-lead technology instead of wire bonding to prevent performance degradation in THz chip interconnects. Full 3-D finite-element method (FEM) simulations and lumped-element analysis indicate the parasitic reduction process, proving this structure’s superiority. Comparative measurements were taken in four frequency bands: 170–220 GHz, 240–320 GHz, 420–470 GHz, and 500–700 GHz. Experimental results show that the beam-lead interconnection substantially reduces insertion loss by approximately 0.5 dB in the 170–320 GHz range. More crucially, the performance advantage increases as the frequency rises to higher THz frequencies. In the 500–700 GHz range, beam-lead technology outperforms wire bonding by about 3 dB due to reduced inductive degradation. This study shows that beam-lead technology can connect future terahertz (THz) integrated systems with high-performance and wideband connections.

In this letter, an ultrabroadband distributed amplifier (DA), fabricated by using 0.25- $\mu $ m GaAs E/D-mode pseudomorphic high electron-mobility transistor (pHEMT) process with $f_{T}$ of 57GHz and extending the operation frequency up to 49.8GHz, is presented. To alleviate the gain roll-off of DA at high operation frequency caused by the parasitic parameters of transistors and the losses of artificial transmission lines, a gain cell with a signal path to compensate the gain is proposed. Measurement results show that the DA using the proposed gain cell features an 8.1-dB average gain in the frequency range from 2.1 to 49.8GHz, a typical group delay of 58ps, and a peak OP ${}_{\mathrm {1 dB}}$ of 14dBm. Integrated the biasing circuit on chip, the implemented DA occupies a chip area of $1.3\times 1.5$ mm including test pads.

This letter aims to design a third-order bandpass filter (BPF) based on the metal integrated suspended line (MISL) platform. To achieve a compact filter design, a triangular patch resonator (TPR) is used, effectively reducing the overall size. At the same time, the available 3-D space is efficiently utilized by employing a vertically stacked resonator arrangement. By implementing a separate electric and magnetic coupling path (SEMCP), a flexible arrangement of transmission zeros (TZs) is introduced, and the influence of different resonator configurations on the dominance of electric and magnetic couplings is discussed. In order to validate the proposed design method and theory, we have developed a prototype. The measurement results show good agreement with the simulation ones, confirming the compact size and low-loss characteristics of the proposed design.

This letter proposes a miniaturized wideband bandpass filter (BPF) with flexible transmission zeros (TZs) using slow wave meander line resonators (SWMLRs) based on metal integrated suspended line (MISL) technology. The TZ positions of the BPF are flexibly controllable via different SWMLR arrangements. A third-order BPF is designed and fabricated by introducing separate electric and magnetic coupling paths (SEMCPs) and source-load coupling, enabling multiple TZs on both sides of the passband. Benefiting from the all-metal MISL structure (copper sheets), the BPF eliminates dielectric loss, achieving a low insertion loss (IL) of 0.28 dB. The filter size is as compact as $0.11\lambda _{g} \times 0.092\lambda _{g} \times 0.067\lambda _{g}$ . Finally, the measured results were in good agreement with the simulation results, verifying the proposed design as a promising solution for miniaturized high-performance microwave filters.

This article presents a systematic electromagnetic (EM)-mechanical co-design methodology based on metal-integrated suspended line (MISL) technology. The method is demonstrated through the design, fabrication, and experimental validation of an F-band mixer. Due to the absence of a supporting substrate in MISL, incorporating the specific mechanical support design is indispensable to ensure mechanical stability. To address this challenge, the innovative approach in this article fully leverages the dual functionality of the short-circuit structures within filters in the mixer for both filtering and support. This eliminates the dependency on additional support structures, thereby reducing redundant circuit area usage and associated insertion loss. By establishing an EM-mechanical bi-objective evaluation function, both the intermediate frequency (IF) and local oscillator (LO) filter structures were designed and optimized. For the first time in terahertz circuit design, mechanical reliability is incorporated from the initial design stage. Experimental results demonstrate that the mixer exhibits conversion losses ranging from 5.48 to 7.72dB across 113–120 GHz, which aligns well with simulation curves, demonstrating competitive radio frequency (RF) performance and verified mechanical fabrication reliability. This approach provides a new solution for terahertz circuit packaging and MISL circuit design, achieving high performance and miniaturization.

This article presents a novel quasi-planar TM₁₀ singlet based on the metal-integrated suspended line (MISL) technology. Compared with the conventional TE₂₀₁ waveguide singlet, the proposed structure achieves an 87% reduction in planar area, demonstrating significant potential for circuit miniaturization. A systematic design approach is developed by exploiting independent control over the transmission pole and zero, thus providing a general framework for the rapid design of MISL singlet. For pole placement, accurate analytical expressions for the TM₁₀ mode are derived using the method of images. Subsequently, zero placement is accomplished by formulating a slope equation that relates the pole-zero ratio to key parameters of the source–load coupling, supplemented by an univariate single-objective parameter fitting process. In contrast to the multivariate multiobjective parameter fitting process typically required for the TE₂₀₁ waveguide singlet, the proposed approach substantially simplifies both the circuit design and modeling procedures for the TM₁₀ MISL singlet. To validate the proposed structure and design approach, two representative examples are provided. The implemented third-order bandpass filter exhibits an insertion loss (IL) of 0.62 dB, and the fourth-order filtering antenna array attains the maximum radiation efficiency of 96.8%. Both designs attest to distinct advantages in circuit miniaturization and low loss, highlighting the promise of the proposed TM₁₀ MISL singlet for millimeter-wave RF filtering circuits.