Rectangular waveguide to strip-transmission-line directional couplers

Bethe´s small slot coupling formulas are presented in a form covering the general case of coupling between dissimilar transmission lines, and these formulas are applied to the special case of coupling between waveguide and strip transmission line. The theoretical coupling of a rectangular slot in the sidewall is calculated, and the coupling and directivity of multiple element arrays are discussed. Measured data on a basic slot are presented and the design procedure for specific couplers is outlined. The test results on a three and four element binomial array coupler in L-band, capable of carrying 7 megawatts peak power, in nonpressurized guide, is presented.