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

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.