35-GHz dual-polarization propagation link for rain-rate estimation

Abstract

A 35-GHz dual-polarization propagation link (DPPL) is described and initial measurements are presented. The instrument is essentially a small, low-power, portable, dual linearly polarized pulsed radar that provides differential attenuation measurements along a short propagation path in rain. Alternate vertically and horizontally polarized pulses are transmitted at a 2200-Hz pulse repetition frequency (PRF). Rain attenuation measurements are made by range gating a passive corner reflector located some distance from the DPPL. Deployment logistics are considerably simplified relative to a standard unidirectional propagation link. Using the ratio of horizontal to vertical received power to determine the differential attenuation reduces the sensitivity to instrument fluctuations since transmitter and receiver drifts slower than the PRF will be cancelled out. This greatly relaxes the calibration and stability requirements on the hardware. Simultaneous measurements of differential attenuation in rain by the DPPL and of rainfall rate with a ground-based rain gauge demonstrate the feasibility of this technique.