An Experimental Dual Polarization Antenna Feed for Three Radio Relay Bands

There are at least two communications problems which require frequency selective filters that operate in waveguides over an approximately 3-to-l frequency interval: (1) channel-separation filters for a circular-electric waveguide system in which it is desirable to use the medium from perhaps 35 to 75 kmc,1 and (2) band-separation networks needed for the horn reflector antenna that permits simultaneous transmission or reception in the 4, G and 11 kmc bands with both polarizations. 2,3 The research reported in this paper was directed at determining the capabilities of coupled-wave transducers for solving such problems. Experimental work was directed toward the second problem (above) because it is more immediate. Fig. 1, which is a schematic representation of the feed array, comprised of three sets of directional couplers, shows that the 4-kmc bands are Fig. 1 -- Schematic of dual-polarization feed for three microwave bands. 391 392 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1957 separated one at a time at the antenna end of the array. The 6-kmc bands are separated next and the 11-kmc bands are added or removed at the far end of the array. GENERAL OBJECTIVES