Analysis of the Propagation Constant of a Ridge Gap Waveguide and Its Application of Dual-Band Unequal Couplers

In this article, an analysis of the propagation constant and the characteristic impedance of a ridge gap waveguide (RGW) is proposed, which includes the comparison of the phase variation between three kinds of guiding structures, the approximation for the propagation constant of RGW, and the variation of characteristic impedances and phase characteristics. According to the analysis, the RGW technology, rather than the traditional microstrip transmission line, is utilized to implement two dual-band unequal couplers operating at two frequency bands. Furthermore, a coupler is fabricated and measured, exhibiting a dual-band operation with a power-dividing ratio of 2 dB and a quadrature phase difference with the same sign between two output ports.