A 340-GHz THz Amplifier-Frequency-Multiplier Chain With 360° Phase-Shifting Range and its Phase Characterization

A 340-GHz compact terahertz (THz) amplifier-frequency-multiplier chain (AMC) offering a full 360° phase shifting range for phased-array applications is proposed in this paper. The AMC comprises an 85 -GHz phase-shifter-embedded ( $\Delta \varphi $ -embedded) power amplifier (PA) and a high-output-power frequency quadrupler (FQ). The PA is equipped with multifunctional impedance matching networks (M-IMNs) that can simultaneously provide balun, impedance transformation, and phase-shifting functions. Analytic expressions have been derived to provide design guidelines for the M-IMNs. With the integrated M-IMNs, the proposed PA can concurrently deliver high output power and a phase shift exceeding 90° in a compact chip area. The proposed FQ can achieve optimal impedance matching at second and fourth harmonic frequencies, leading to the output power enhancement of 2.6 dB. Furthermore, the output phase of the PA is quadrupled by the FQ, resulting in the output signal of the AMC with a full 360° phase-shifting capability. A measurement setup for characterizing the phase of a THz signal is also presented. Implemented in a 40-nm CMOS technology without ultra-thick metal layers available, the proposed THz AMC achieves a peak output power of −3.5 dBm at 368 GHz with a conversion gain of 1.8 dB and a 3-dB bandwidth from 340 to 376 GHz. The output phase can continuously vary over 360° within the 324 to 346 GHz frequency range. The phase noise of the output signal at 346 GHz is −105 dBc/Hz at a 10-MHz offset frequency. The proposed 340-GHz AMC consumes 215.1 mW from a 0.9-V supply.

I. Introduction

Terahertz (THz) science and technology have garnered considerable attention in recent years due to their potential applications in communication and sensing [1], [2], [3], [4]. Notably, they have been considered promising candidates for the sixth-generation (6G) high-speed wireless communication system, aiming for data rates of up to 100 Gb/s [5], [6], [7], [8]. However, THz waves confront a substantial challenge of high path loss, e.g., 82 dB at 300 GHz for only a 1-m communication distance. Furthermore, generating high-output power at such high operation frequencies remains challenging in THz electronics. These dual impediments significantly limit the operation distance and performance of THz systems. To address these issues, the integration of phased-array technology becomes imperative. By coherently combining signals emitted and received from regularly distributed transmitters and receivers, the signals can be steered and accepted along the desired directions, significantly increasing the equivalent isotropically-radiated power and the signal-to-noise ratio.