TH-3 Microwave Radio System: Networks

The frequency selectivity required by the microwave transmitter and receiver of the T H - 3 radio system is provided by passive networks. Adjacent-channel selectivity, together with suppression of second and third harmonics of the intermediate frequency (IF) which are generated in the receiving modulator and IF preamplifier, is provided by a loss- and delay-equalized intermediate-frequency filter. Microwave filters and selective networks provide image-frequency and adjoining-channel selectivity, furnish the required discrimination against unwanted tones and noise originating in the microwave generator, and are used for the multiplexing of transmitters and receivers into a common antenna-feed waveguide. Microwave delay equalizers compensate for the envelope delay distortion (EDD) of the selective microwave transmission networks,* so that only a relatively small residue of E D D remains to be mopped up by IF delay equalizers.