Sheng Li

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.

The development of next-generation terahertz (THz) transmitters and receivers based on 3D stacked packaging technology relies heavily on the integration of high-performance waveguide directional couplers. This paper presents an accurate and efficient method based on the mode-matching method (MMM) for the rapid analysis of a branch waveguide coupler fabricated through a silicon-based 3D stacking process. In contrast to the traditional method using the finite-element method (FEM) in HFSS, which is cumbersome and time-consuming, the proposed method offers orders-of-magnitude speed improvement. It is especially well-suited for large-scale uncertainty error analysis and statistical evaluation of THz waveguide couplers and related components. This theoretical MMM is validated through an experiment by characterizing a deep reactive ion etching (DRIE) fabricated and 3D stacked 220 GHz waveguide coupler.

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 paper presents a high gain, broadband silicon micromachined diagonal horn array antenna for the 190 GHz to 250 GHz frequency band. The antenna array is configured to be built from 34 silicon layers. The upper 25 layers of silicon wafers create an 8×8 diagonal horn array antenna and the lower 9 layers form the feed network. The diagonal horn is selected as a radiation element for its 45° polarization direction, which suppresses side and grating lobes in the E-plane and H-plane after array formation. Polarization converters are innovatively employed in the feed network to resolve the issue of opposite polarization from waveguide T-junctions. In order to meet the silicon micromachining criteria, all diagonal horns and the feed network are step-profiled designed based on silicon wafer thickness. The 34 silicon layers are aligned and fixed by CNC-milling metal tooling. Monte Carlo analysis is utilized to quantify the interlayer offset errors introduced during the assembly of the wafers. The measurement results are within the error allowance. The antenna achieves a peak gain of 30.9 dBi and a working frequency bandwidth of 27%. Characterized by highly directive radiation patterns with low side lobe levels in the E-plane and H-plane, the antenna is well-suited for next-generation THz point-to-point communication systems.

In this paper, a W-band waveguide bandpass filter with a standard fourth-order Chebyshev response is proposed based on the computer numerical control (CNC)-milling technology. The harmonics-staggered technique and orthogonal coupling method are incorporated into this waveguide filter design without increasing the complexity of the filter structure in order to suppress the intrinsic spurious responses near the passband. Furthermore, the proposed filter design maintains a simple construction, which can be conveniently fabricated using CNC milling. The fabricated waveguide filter exhibits an average insertion loss of 0.9 dB and a return loss of above 20 dB in a 3 dB fractional bandwidth (FBW) of 5.5% centered at 85 GHz. The excellent spurious suppression property can reach better than −25 dB up to 165 GHz. The wide stopband performance of the proposed W-band filter is very competitive compared with the reported waveguide filters.

A wideband multi-polarized square-horn antenna based on an orthogonal mode transducer (OMT) is developed for working in the whole W-band in this paper. The designed antenna is capable of radiating multiple polarization modes as horizontal polarization (HP) and vertical polarization (VP) when as single-port excitation and left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) when as dual-port excitation, owing to the characteristic of the OMT with the transmitting of orthogonally polarized waves. A CNC-layered fabrication approach is proposed, which means that the antenna prototype integrating with a Boifot-type OMT, turning waveguide, twisting waveguide and phase shifter is divided into three layers along the vertical direction to be fabricated based on computerized numerical control (CNC) technology. In the design, the turning waveguide and twisting waveguide are employed to achieve plane consistency of the antenna branch ports. Furthermore, a phase shifter is designed to compensate the orthogonally polarized waves, which can keep the phase of the orthogonally polarized waves consistent in a wideband frequency range from 75 GHz to 110 GHz. A prototype is fabricated and measured to verify the performance of the proposed multi-polarization antenna, and the measured results agree well with the simulation ones. In the whole W-band, the value of return loss is better than 10 dB of all polarization modes, and the value of AR of the LHCP and RHCP is below 3.5 dB. The maximum gain of the antenna reaches up to 18.8 dBi at 110 GHz. In addition, regarding the layered structure, the possible layered assembly error analysis is discussed, which verifies the feasibility of the layered machining for this antenna.

A W-band H-plane horn array antenna with tilted radiation beam based on waveguide structure is proposed in this paper. The designed antenna array consists of four H-plane antenna elements and a broadband feed network. The distribution of excitations is determined by the theory of maximum power transmission efficiency (MMPTE). A multiple branch coupler, two T-junctions and three fixed phase shifters are employed to construct the feed network, which can generate the required amplitude and phase in broadband frequency range from 80 GHz to 100 GHz. The computer numerical control (CNC) milling machines technology is employed to machine the feed network and antenna. All measured and simulated results are in good agreement, which verify the feasibility of the theory of MMPTE to generate a radiation beam directed to any angle from −35° to 35° with suitable excitation provided by the proposed feed network in this paper.