Tunable 245 GHz transmitter and receiver in SiGe technology for gas spectroscopy

Abstract

A 245 GHz sensor system for gas spectroscopy is presented, which includes an integrated SiGe transmitter (TX) and receiver (RX), and a 0.6 m‐long gas absorption cell between the TX and RX modules. The integrated local oscillators (LOs) of TX and RX chips are controlled by two external phase‐locked loops (PLLs), whose reference frequencies are swept with constant frequency offset for a low intermediate frequency of the RX. The RX consists of a differential low‐noise amplifier, an integrated 122 GHz LO with a 1/64 divider, a 90° differential hybrid and an active subharmonic mixer. The TX consists of an integrated 122 GHz LO with a 1/64 divider, and a frequency doubler. The TX and RX chips are fabricated in 0.13 µm SiGe BiCMOS technology with f T / f max of 300 GHz/500 GHz. Using external dielectric lenses for the TX and RX modules, the gas absorption spectra were measured for acetonitrile and methanol.