HIGH PERFORMANCE MULTI-SECTION CORRUGATED SLOT-COUPLED DIRECTIONAL COUPLERS

Abstract—In this paper a robust technique for the design of high performance directional couplers is proposed. It combines the advantages of wiggly coupled lines and slot-coupled lines but overcomes their main limitations. The key to this novel technique is a new corrugated slot that allows perfect compensation of the even and odd mode phase velocities and can be easily designed using Bloch-Floquet theory, yielding outstanding performance. To demonstrate the validity of the proposed technique, the design of two different wideband directional couplers is presented. The first design consists of a 10 dB asymmetric directional coupler with a one decade bandwidth (1.2– 12GHz) that exhibits a coupling accuracy of 10 ± 0.6 dB, a return loss better than 23 dB and an isolation better than 28 dB across the complete frequency band. The second design consists of a symmetric quadrature hybrid that operates over the complete UWB band (3.1 to 10.6GHz) showing an amplitude and phase imbalance between the output ports lower than ±0.5 dB and ±0.7◦, respectively. 1.