A 17:1 Dual Band Circularly Polarized Two-Channel Monopulse Tracking System
AIR FORCE AVIONICS LAB WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
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The paper describes a feed system designed for ultimate use in the 85-foot NASA STADAN dishes. This system uses a series of nested multiarm spirals to provide sum and difference two-channel monopulse tracking outputs for simultaneous left- and right-hand circularly polarized signals. These outputs are simultaneously provided at frequencies of 136 MHz, 235 MHz, 400 MHz, 1700 MHz, and 2200 MHz. The paper describes the theory of operation and the results obtained with the feed itself. The paper concentrates on results obtained in the field with the unit mounted in a 60-foot test dish. The unit was used to track the Apollo VIII vehicle to the moon and back. In addition to this, the feed was also used for star tracking to establish its boresight accuracy. The fact that the feed system has now been operationally checked out demonstrates that two-channel monopulse is a technically sound method of tracking, with the added advantages of simplicity in feed design and improved secondary pattern characteristics.