A fast approach to the design of compact couplers

Based on the admittance parameters, a simple, efficient, and precise approach is proposed to design compact couplers. The required admittance parameters are directly derived from the goal of scattering properties. And the pure admittance parameters of a actual compact structure are obtained by means of de-embedding technique. Because all parasitic effects of a compact structure have been included in pure admittance parameters naturally, the tuning process is easy and fast. Two cross-slot patch couplers (power splitting ratio k²=1.0, 0.25) worked at 17 GHz are developed to validate the proposed approach. Measured results showed that, at the center frequency, the return-losses of two couplers are beyond 28 dB, the isolation are beyond 24dB, the total insert-losses are below 1.6 dB, and the practical deviations from the ideal power splitting ratio are below 0.2 dB.