This article presents a novel 200-GHz four-element phased-array receiver system-in-package (SiP) using high-temperature co-fired ceramic (HTCC) technology for wireless communications. The receiver employs a local oscillator (LO) phase-shifting architecture to realize sub-terahertz (THz) beamforming. All components of the front-end array are heterogeneously integrated within the HTCC. To achieve low-loss interconnection and 3-D integration, quartz substrates and vertical air-filled waveguides are incorporated within the HTCC. Meanwhile, an electromagnetic bandgap (EBG) structure is introduced in the vertical transitions to mitigate energy leakage caused by assembly gaps, thus reducing the sensitivity to assembly errors. Besides, a highly efficient parabolic reflector antenna array with a multilayered structure is designed for beam scanning. The overall size of the front-end package is 40.7 $\times$ 43 $\times$ 7.3 mm $^{3}$ . The measured channel gain is 8.2–23 dB from 194.5 to 234.5 GHz (18.6% bandwidth), and the measured lower-sideband noise figure is 7.5–9.4 dB, covering from 196 to 215 GHz. The phased-array receiver can achieve a scanning range of $\pm$ 30 $^{\circ}$ in the E -plane. To evaluate its over-the-air (OTA) performance, a wireless link is demonstrated with 16-quadrature amplitude modulation (QAM) and 64-QAM waveforms, achieving a maximum data rate of 32 Gbps.

A high-integration and low-cost transmitter packaging solution for 0.2-THz system-in-package (SiP) application is newly presented using high-temperature co-fired ceramic (HTCC) technology. To improve 3-D integration, internal vertical air-filled interconnection waveguides buried in the HTCC package are explored and fabricated. A compact MoCu waveguide bandpass filter (BPF) is designed and integrated into the package to suppress the harmonic output of the mixer. To demonstrate the potential SiP application in the future 0.2-THz radar systems, based on the proposed solution, two 0.2-THz transmitters using frequency multipliers/mixer are designed, fabricated, and measured. All the components are buried in HTCC, and the overall size is $36\times 14\times9.8$ mm ³ and $54\times 14.5\times9.8$ mm ³ , respectively. Both the transmitters show good performance, and the measured output power is better than 8 and 5 dBm, respectively.

In terahertz communication systems, amplifiers and other components can induce non-linear distortion in terms of amplitude and phase, resulting in system performance degradation. This paper presents a terahertz metamaterial waveguide to mitigate amplitude and phase distortions in some terahertz systems. A simple method based on free-space analysis is proposed for designing metamaterial waveguides in an enclosed space. The quasi-periodic metamaterial structures, which feature I-shaped resonant patterns, are integrated onto the inner walls of rectangular waveguides. The phase and amplitude of electromagnetic waves within the waveguide can be modulated by varying the dimensions and number of these resonators. Utilizing the effective medium theory and the equivalent circuits, the metamaterial waveguide’s phase and absorption modulation mechanisms are analyzed. Based on the proposed structure, a metamaterial waveguide with I-shaped resonators is designed and fabricated, and its abilities to modulate the phase and absorption of terahertz waves around 0.2 THz are demonstrated.

A wideband front-end module with antenna-in-package (AiP) for X -band phased-array radar applications is newly presented using low-temperature con-fired ceramic (LTCC) technology. This work integrates multiple chips into the AiP, resulting in a multi-functional front-end prototype. For improving antenna bandwidth and radiation efficiency, four air cavities are embedded inside the package to lower the effective dielectric constant. Additionally, bowtie-shaped patches and improved apertures are introduced to increase the antenna bandwidth further. The overall size of the LTCC package is 14.3 × 24.5 × 3.55 mm ³ . The antenna's voltage standing wave ratio is better than 2.5 at the full X band (40% bandwidth), and the maximum gain is 8 dBi. Besides, the receive gain of the active prototype is better than 30 dB at the full X band, and the transmit equivalent isotropic radiated power is 32–38.5 dBm, showing a good performance.

This article presents a 200-GHz phased-array wireless communication system featuring local oscillator (LO) beamforming using high-temperature co-fired ceramic (HTCC) technology. The system is constructed using HTCC transmit (Tx) and receive (Rx) system-in-packages (SiPs), which are mounted on printed circuit boards (PCBs) and connected to parabolic antennas through waveguide feeders. These SiPs heterogeneously integrate all components of the front-end channels, achieving low-loss interconnection and 3-D integration through vertical hollow waveguides within the HTCC. The Tx SiPs incorporate integrated Schottky diode mixers with MoCu waveguide filters, performing single-sideband upconversion with high image rejection. Measured Tx channel gain ranges from 17 to 40 dB over 192.5 to 212.5 GHz, with channel saturated output power from 5.2 to 9.6 dBm over 193.5 to 211.5 GHz. Furthermore, the eight-element Tx array achieves an effective isotropic radiated power (EIRP) of 35.9 to 43.3 dBm across 196 to 213 GHz and supports a scanning capability of ±30° in the E-plane. The phased-array Tx-Rx wireless link is demonstrated over a 30-m distance using 16-quadrature amplitude modulation (QAM) and 64-QAM waveforms, supporting maximum data rates of 32 and 24 Gbps, respectively.

We propose a meta-waveguide, a component based on metamaterials and waveguides, to customize the phase and absorption of devices. This meta-waveguide integrated quasi-periodic metamaterial resonators with film resistors in the inner wall of the waveguide. The phase and absorption at multiple specified frequency points can be changed regularly by adjusting the resonators and film resistors. We analyzed the meta-waveguide structure and derived a transcendental equation, which revealed the physical mechanism of phase control. In addition, we propose an equivalent circuit model to explain the mechanism of absorption control. Then, a customized meta-waveguide that works from 90 to 100 GHz was designed, fabricated, and demonstrated.