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This article presents the design of a CMOS-based voltage-controlled oscillator (VCO) operating in both $V$ - and $W$ -bands by fully utilizing the harmonics in Class-F23 tank. An auxiliary common mode (CM) resonance is introduced to Class-F23 structure via a transformer for CM resonance expansion. This transformer serves dual functions, also generating the second harmonic output, thereby enhancing the area efficiency. The proposed CM resonance expansion suppresses the flicker noise upconversion in a widehband without manual harmonic tuning. A Class-F23 VCO without CM expansion is designed and fabricated for comparison. Besides, the challenges in high-frequency harmonic extraction are highlighted and addressed. The proposed VCO is fabricated using 40-nm CMOS technology. The frequency can cover from 69.92 to 73.84 GHz and from 104.88 to 110.75 GHz with tuning ranges of 5.7%. The measured $V$ - and $W$ -band phase noises (PNs) are −102.5 and −92.35 dBc/Hz at 1-MHz offset with figures of merit of −182.5 and −176 dBc/Hz, respectively. The power consumption is 44 mW in an area of 0.36 mm2.

In this study, we present the design, fabrication, and measurements of a 3-D heterogeneous integrated RF-module at W-band. A 3-D transition structure based on micro-bumps is fabricated and measured to obtain the transition loss of one bump. One micro-bump has an insertion loss of 0.21 dB at the W-band. A packaged filter and a benzocyclobutene (BCB)-based back cavity antenna are designed and analyzed in detail. The filter has a 2.6-dB insertion loss at 94 GHz with four transmission zeros (TZs) and a $2.14f_{0}~10$ -dB stopband. An extra loss of 0.9 dB is found after packaging. Then, the filter and antenna are integrated with a SiGe-based low-noise amplifier (LNA) and a mixer to realize a fully packaged receiver by using our in-house Si-based micro-electromechanical systems (MEMS) through-silicon-trench (TST) technology and multilayer photosensitive composite film. The proposed 3-D heterogeneous integrated receiver is measured on-wafer. This low-loss packaging solution can be further used in millimeter-wave communication or radar systems.

A 3-D integrated antenna array is proposed with the low-temperature co-fired ceramic (LTCC) technology in this article, which has the characteristics of circular polarization (CP), good filtering response, and high efficiency simultaneously. To guarantee both the transmission efficiency and the routing flexibility, a hybrid feeding network is constructed with a 16-way air-filled gap waveguide (AFGWG) power divider and $4\times 4$ stripline (SL) two-stage sequentially rotated feeding networks, to excite $16\times 16$ radiating elements of stacked patch etched with cross-shaped slots, operating in K-/Ka-bands. The AFGWG feeding structure is very suitable for large-scale integrated arrays. A substrate integrated waveguide (SIW) filter is introduced with the passband of 23–27.5 GHz to further improve the bandedge frequency selectivity. All the components and their transitions are designed collaboratively and co-implemented vertically, enabling high-density multifunctional integration. The proposed antenna array shows the peak realized gain of 25.2 dBi, the in-band antenna efficiency of 38%–48.6%, and the axial ratio (AR) below 1.98 dB. By combining the responses of all parts, such as the quasi-bandpass stacked patches, the quasi-bandpass AFGWG-to-SL transitions, the quasi-highpass AFGWG structure, and the bandpass SIW filter, the out-of-band suppression is achieved better than 32.5 dB in 28.5–40 GHz and 41 dB in 18–22 GHz. Our idea has been demonstrated by the good agreement obtained between the simulated and measured results.

This article presents a novel 30.5-dBm output power 1 transmitter and 2 receivers (1T2R) heterogeneously integrated (HI) phased-array frequency-modulated continuous-wave (FMCW) radar transceiver using local oscillator (LO) phase shifting (PS). Two $X$ -band GaAs-based 6-bit PSs are designed and placed at the LO path. Two $W$ -band GaN-based power amplifiers (PAs) are proposed, amplifying the FMCW signals with 30.5 dBm at output. The antenna in package (AiP) is designed and fabricated in a high-resistivity silicon wafer by combining through silicon ring-trench and artificial magnetic conductor (AMC), where the $1\times4$ antenna array has a high radiation efficiency (70%), a broadband (12%), and a high gain (11.8 dBi) in the $W$ -band. Two $W$ -band SiGe-based transceiver systems on a chip, GaN-based PAs, AMC-based AiPs, and two $X$ -band GaAs PSs are HI with a transceiver size of $31\times17$ mm2 by using our in-house silicon-based MEMS photosensitive composite film given the advantages of high-density integration and fabrication accuracy. The HI radar application is measured with an effective isotropic radiated power of 41 dBm with a measured 2 cm range resolution. The beam scanning performance is also measured and presented using three corner reflectors located at different azimuths. Simulated and measured beamforming results show good agreement. The HI radar sensor has a size of $70\times70$ mm2 with a weight of only 200 g.

This article presents a novel high-gain antenna-on-chip (AoC) solution for the sub-terahertz band using a standard semiconductor and packaging process. The novel AoC is realized by bonding on a usual AoC in a semiconductor technology with a microbump in a flip-chip technology. As a result, an additional radiation mode can be activated, leading to increased radiation efficiency and gain. Both usual and novel AoCs were designed in the dipole-type antenna configuration for the band of 300 GHz. The usual AoC was fabricated using a $0.13 \, \mu \text{m}$ silicon-germanium (SiGe) technology, while the novel AoC was fabricated using the same $0.13 \, \mu \text{m}$ SiGe technology and the standard flip-chip technology. The usual and novel AoCs have the same die area of $2 \times 2$ mm2. Compared with the usual AoC, the novel AoC has demonstrated the enhancement of all performance parameters. The radiation efficiency, peak realized gain, and impedance bandwidth have been improved significantly, rising from 15.9% to 41.1%, 1.91 to 8.67 dBi, and 15.6 to 39.6 GHz, respectively. Hence, it is believed that the novel AoC solution is particularly suitable for highly integrated sub-terahertz systems.