Recent work on improvement of the AN/MPQ-501 counter mortar radar receiving system is summarized, along with calculated and measured effects of rainfall on the system. Laboratory evaluation of an image-rejection mixer and a commercial parametric amplifier indicates that a basic receiver noise figure close to 4db can be obtained. A revision of the noise monitor equipment to improve its accuracy is described. The construction and performance of a ceramic waveguide window having a VSWR less than 1.1 within the radar band is included. Measurement of the effectiveness of the circular polarizer as a means of reducing rain clutter indicates a gross cancellation of about 20db. Measured clutter levels of 22 to 32db above receiver noise power for light to moderate rainfall rates at a range of 10km are reported.
National Research Council of Canada. Radio and Electrical Engineering Division
Report (National Research Council of Canada. Radio and Electrical Engineering Division : ERB), no. ERB-759.