3-db Couplers Constructed from Two Tandem Connected 8.34-dB Asymmetric Couplers (Correspondence)

The technique of tandeming two symmetric 8.34-dB directional couplers to produce a 3-dB coupler was described in 1965 by J.P. Shelton, et al.. This technique is useful because broadband 3-dB couplers are difficult to synthesize directly, due to the impedance levels involved. This correspondence shows that it is possible to tandem connect two asymmetric 8.34-dB couplers to yield a broadband 3-dB device. Design tables for 8.34-dB asym. metric couplers which give the normalized even-mode impedances required for a given ripple, number of sections, and bandwidth are also presented.