Analysis and design of slot-coupled directional couplers between double-sided substrate microstrip lines

The characteristics of a slot-coupled directional coupler between two microstrip lines coupled through a rectangular slot in the common ground plane are studied. Conformal mapping techniques are used to obtain analytic closed-form expressions for the coupler's even and odd-mode impedance and propagation constants for any coupler configuration. Using the spectral domain approach, a full-wave analysis is performed to determine the dispersion properties of coupler parameters. Theoretical and experimental results for a 10-dB coupler at 10 GHz are presented.<
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