COMSTAR Experiment: The 19- And 28-GHz Receiving Electronics for the Crawford Hill COMSTAR Beacon Propagation Experiment

The receiving electronics for the COMSTAR beacons has placed strong demands on technology in several areas in order to meet the requirements of the propagation experiments. 1,2,3 The receiving system built at the Bell Laboratories Crawford Hill facility includes a precision antenna 4 and the receiving electronics necessary to make maximum use of the 19- and 28-GHz beacon signals radiated by the COMSTAR satellites. The receiving electronics is the subject of this paper. Continuous unattended operation is required so that all significant weather events are included in the resulting data base; thus, a very high 1289 degree of reliability in the receiving electronics is required, and automatic reacquisition of the beacon signal after dropout due to severe attenuation or momentary power outage is essential. Since relative phases of the many signal components must be precisely measured, the phase stability of all circuits and components demanded careful attention. Also, circuit arrangements had to be devised to ensure that signals which were later to be compared in phase traversed a common path through high-gain amplifiers and other phase-sensitive equipment. In order to obtain the maximum possible measuring range using the modest powers radiated by the satellite beacons, very narrow receiver noise bandwidths are required. This puts a premium on the stability of the source oscillators in the satellites and the local oscillators in the earth stations. The receiver includes an AFC circuit with built-in memory to facilitate reacquisition after loss of signal.