A LOW-COST 20-22-GHZ MIC ACTIVE RECEIVER RADIOMETER

A microwave integrated circuit active receiver is built and tested at 19-25 GHz. The receiver consists of a planar CPW-fed double folded-slo t antenna coupled to a six-stage MESFET amplifier and followed by a pl anar Schottky-diode detector, The folded-slot antenna on a GaAs half-s pace results in a wide frequency bandwidth suitable for MMIC amplifier s, The measured system performance show a video responsivity close to 1 GV/W at 20 GHz with a 3-dB bandwidth of 1500 MHz, A novel method whi ch uses the planar video detector after the amplifier stages as an RF mixer is used to measure the noise-figure of the direct detection radi ometer. The system noise figure is 4.8 dB at 22 GHz, The radiometer se nsitivity to a hot/cold load is 3.8 mu V/K. The measured antenna patte rns show a 90% Gaussicity at 20-22 GHz, The active MIC receiver can be integrated monolithically for low-cost applications and is well suite d for millimeter-wave linear imaging arrays.