. Airborne radar. Airplanes; Guided missiles. 550 ANTENNAS AND RF COMPONENTS The uses of 3-db hybrid junctions are many in radar systems,^^ from their use as a 3-db directional coupler and for power splitting, to deriving "sum" and "difference" signals in the microwave bridge circuits of monopulse antenna feeds. The use of 3-db hybrids in balanced mixers and duplexers will be described later. Many other multiport hybrid junctions have been developed or devised for special application. Among these are two of particular interest for circularly polarized systems: the turnstile
. Airborne radar. Airplanes; Guided missiles. 550 ANTENNAS AND RF COMPONENTS The uses of 3-db hybrid junctions are many in radar systems,^^ from their use as a 3-db directional coupler and for power splitting, to deriving "sum" and "difference" signals in the microwave bridge circuits of monopulse antenna feeds. The use of 3-db hybrids in balanced mixers and duplexers will be described later. Many other multiport hybrid junctions have been developed or devised for special application. Among these are two of particular interest for circularly polarized systems: the turnstile waveguide junction^^'^^ and the trimode turnstile waveguide ; The latter junction, shown schematically in Fig. 10-23, has particular utility in a compact dual balanced mixer for circularly polarized applications.^^ S^. Fig. 10-22 The Hughes H-Plane Folded Fig. 10-23 The Trimode Turnstile June- Hybrid Tee, a 3-db Hybrid Junction. tion, a Symmetrical Seven-Port Hybrid (Microwave Development Laboratories, Junction. Inc.) The Mixer. The purpose of the mixer^^ in a radar receiver is to convert the incoming microwave signal to an intermediate frequency (IF) signal of similar character which can be amplified using low-frequency techniques. This process is accomplished by mixing the received signal ^''J. W. Sutherland, "Waveguide Hybrid Circuits and Their Use in Radar Systems," Etec- tronic Eng. 28, 464-469 (1956). 3'^M. A. Meyer and H. B. Goldbers;, "Applications of the Turnstile Junction," IRE Trans. MTT-3, No. 6, 40-45 (December 1955). ^^R. S. Potter and A. Sagar, "A New Property of the Turnstile Waveguide Junction," 1957 Proc. Natl. Electronics ConJ. , 452-458 (1958). s^R. S. Potter, "A Trimode Turnstile Waveguide Junction," IRE Convention Record 4, Part 5, 36-43 (1956). ^P. J. Allen and R. D. Tompkins, "An Instantaneous Microwave Polarimeter," Pf-oc. IRE 47, 1231-1237 (1959). 39R. V. Pound, Microwave Mixers, McGra
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