Kaiqiang Zhu

In this letter, a high-mode-purity TM₀₁-to-TE₁₀ mode transducer operating at 340 GHz is designed, which has great potential in terahertz (THz) power combining. A compact configuration and high mode purity are realized through the integration of a five-step septum and an impedance matching structure within the transducer. By adopting a well-optimized septum and transition structure, high suppression of spurious modes (TE₁₁, degenerated TE₁₁ mode) greater than 50 dB can be achieved, resulting in a TM₀₁ mode purity as high as 99.9%. Notably, the septum-based transducer enables same-direction mode conversion from TM₀₁ to TE₁₀, which significantly simplifies subsequent assembly and enhances overall system integration. A back-to-back prototype of the transducer operating in the 310–355 GHz range was fabricated and tested. The measured results show that within the frequency range, the overall average insertion loss of single transducer is approximately 1.55 dB (1.5dB at 340 GHz), and the return loss of the input port is better than 10 dB.

This article presents an ultra-compact and broadband Wilkinson power divider/combiner (WPDC) designed for large-scale phased arrays. To minimize the chip area, a shortened transmission line (T-line) topology using a metal-stacked inductor is introduced into the two stages. Furthermore, to address the isolation bandwidth (BW) limitations, two sections of shortened T-lines are adopted and innovatively implemented within a single inductor footprint by utilizing a magnetic coupling self-canceling technique. Detailed analysis and design flow of the proposed network synthesis are provided, demonstrating a 67% area reduction. Moreover, a novel shielding topology is employed to simultaneously enhance isolation between combiners and ensure amplitude/phase uniformity across distribution branches. To verify the proposed technique, a C–X-band WPDC, consisting of two 1:4 power combining units dedicated to intermediate frequency (IF) and local oscillator (LO) bands, respectively, is fabricated in a 65-nm bulk CMOS process. The prototype exhibits a measured insertion loss (IL) of within 3.2/3.4 dB and isolation exceeding 24.9/26.0 dB across the IF (6–10 GHz)/LO (8–12GHz) band. Notably, isolation greater than 60 dB is attained between IF and LO crossover networks, which is validated in antenna-in-package (AiP) measurements. This design features an ultra-compact core area, a highly competitive fractional isolation BW, and an outstanding branch isolation among state-of-the-art reported works, rendering it well-suited for area-constrained large-scale and multibeam phased-array systems.

Metasurface holography has emerged as a transformative technology with significant potential in information encryption, virtual displays, and high-capacity data storage. However, developing a holographic display system with ultrahigh information capacity and multidimensional multiplexing remains a major challenge. To address this issue, we propose a Janus metasurface holographic display scheme featuring asymmetric transmission and multi-depth imaging at microwave frequencies, enabled by complex-amplitude modulation. The modified three-dimensional holography method we proposed enables the complex-amplitude modulation devices to acquire the ability of manipulating multi-depth holographic displays. By simultaneously multiplexing the propagation direction and propagation distance of incident waves, a large number of distinct holographic images can be reconstructed throughout the entire propagation space. As a proof of concept, we experimentally demonstrate the reconstruction of five distinct letter images, each located on different planes along opposite propagation directions. The measured results show excellent agreement with simulations, validating the proposed strategy. This approach paves the way for metasurface-based holographic display systems featuring ultrahigh information capacity, robust holographic encryption, and high-efficiency data storage.

This article presents a wideband terahertz (THz) 2-D ${M} \times {M}$ spatial power combiner (SPC) based on a mode conversion method. It consists of a transmitting array, a transmitarray (TA), and a receiving antenna, which are integrated in a sealed metal cavity. The TA provides phase manipulation to transform the TE₁₀-mode ${M} \times {M}$ beams from the transmitting array to the Gaussian beam matched with the receiving antenna. The proposed SPC achieves efficient power combining in a wide bandwidth by designing the low-loss dielectric TA elements with a linear phase shift and a wideband transmitting/receiving antenna. A 3-D printed $4\times 4$ THz SPC is designed and fabricated. The measured output and input return loss are greater than 12 and 9 dB, respectively, and the combining efficiency is 54%~74% within 230–325 GHz (34.2%). The proposed ${M} \times {M}$ THz SPC can be applied for THz high-power sources based on photodiodes.

This letter presents a wideband phase-reconfigurable reflector (PRR) for a reconfigurable reflectarray antenna (RRA) in K-band, which is implemented in a 0.15- $\mu $ m GaAs pHEMT process. The proposed PRR consists of a series resonant network and a series-parallel resonant network, which are composed of three pHEMT switches, inductors, and capacitors. By using 0/−5-V voltage to control the on/off of three pHEMT switches separately, different circuit states can be formed. Constructing mappings between different circuit states and the required phase shifts can achieve a phase shift of 0°–360° in 90° steps while effectively reducing reflection losses (RLs) and improving bandwidth. The experimental results show that in the 20–27-GHz bandwidth, with phase shift errors (PEs) of each phase shift state less than ±15°, the RLs of all states are less than 2.35 dB, and the percentage bandwidth can reach 30%. To the best of our knowledge, this PRR achieves the maximum bandwidth among the published 90° step PRR.

This letter presents a 27-32 GHz compact phase shifter (PS) and attenuator (ATT) in 16-element phased-array for satellite communication (SATCOM) in 65-nm CMOS technology. Each element comprises a 5-bit switched-type attenuator (STA), a driver amplifier (DA), a 6-bit vector modulation phase shifter (VMPS) and a two-stage power amplifier (PA). STA occupies an area of only 60 μm × 100 μm, enabled by capacitive compensation technology. Furthermore, an extremely compact layout of the I/Q signal generation reduces the VMPS area to 140 μm × 225 μm.

This paper proposes a compact W-band antenna-in-package (AiP) design for a phased array front-end module. A slot-coupled stacked patches structure is developed to address integration challenges and enhance bandwidth limited by the thin substrate. The antenna is optimized by particle swarm optimization (PSO) algorithm and manufactured by cost-effective modified semi-additive process (mSAP). Experimental results from an 8 × 8 phased array module demonstrate consistent performance, including $\pm 30 ^{\circ }$ beam scanning ability, low scan gain loss (< 2 dB) and low cross-polarization(< -20 dB) with a maximum measured EIRP of 54.8 dBm. This work provides a scalable and cost-effective solution for the integration of millimeter wave phased array systems.

A sextuple band circularly polarized (CP) shared- aperture antenna (SAA) with a small frequency ratio (FR) is presented in this paper. The SAA consists of a wideband scanning array and five narrow-band antennas. For a high integration, the stacked, interlaced and structure-reused schemes are employed comprehensively. To solve the problem of the insufficient area of the lower antenna to support the upper antenna in a stacked scheme, the metal column is introduced and it can also shield out the effects of feeding coaxial lines on the performance of the lower antenna. By loading the cavity, the degraded performance at the low elevation angle can be compensated. The SAA has a high ratio of aperture reduction compared with tradition multiple separate antennas, while keeping a lower profile. It can achieve 2D beam steering in a scanning range of ±45°.The prototype was fabricated and the measured results are consistent with the simulated ones. This SAA is well suited for navigation and wireless communication.

This letter presents a vertically polarized omnidirectional antenna designed for operation within the 50-75 GHz (V-band) frequency range. The compact antenna structure and wide working bandwidth are achieved through the use of a radial waveguide radiator and an axial intermediate converter. The measured results from the manufactured prototype agree well with the simulated data in terms of radiation pattern and return loss. The antenna exhibits a 3 dB beamwidth in the elevation direction exceeding 30 $^\circ$ and a return loss greater than 10 dB across the working band. Owing to its wide bandwidth and omnidirectional radiation performance, the proposed antenna emerges as a promising candidate for indoor wireless communication system.