First results of a 1.2 THz MMIC sub-harmonic mixer based GaAs Schottky diodes for planetary atmospheric remote sensing

We present here the first measurement results of a 1200 GHz heterodyne receiver front-end prototype based on this Schottky GaAs membrane technology. The 1200 GHz subharmonic mixer design, previously reported, uses a suspended MMIC GaAs membrane that feature a balanced pair of planar Schottky diodes and an on-chip MIM capacitor for DC forward biasing capabilities. The possibility to bias the sub-harmonic mixer is very important in order to release constraints on the amount of LO power required at 600 GHz. Measurement results show a DSB mixer noise temperature better than 6000 K and DSB mixer conversion losses better than 15 dB are achieved in the RF range 1130 GHz to 1220 GHz. The estimated LO input power available is between 1 mW and 1.5 mW. For this relatively low LO power levels, the optimum bias voltage is approx. 0.85 V with a rectifying current of 170 uA. These performance values are in agreement with predictions, but it is believed that the performance can be improved by selecting devices with better electrical characteristics and increasing the amount of LO power available.