Substrate Integrated Waveguide with Corrugated Wall
Substrate integrated waveguide (SIW) allows waveguide techniques to be implemented on PCBs . The technology has been successfully applied to a number of devices such as filters, couplers, dividers, slot array antennas , oscillators, six port circuits, and circulators . Its models and numerical analysis techniques have also been extensively researched . One particular challenge facing SIW circuits is their integration with active components that require DC biasing. An inherent DC short-circuit is formed between conventional SIWs’ top and bottom waveguide plates due to the conducting vias. Several schemes have been proposed to address this issue. They include the use of discrete capacitors on microstrip lines leading up to the SIW circuit , embedding an interdigitated capacitor into the SIW-tomicrostrip transition , and using AC coupling on half mode SIW . None of the existing methods allow direct shunt connection of active components, such as Gunn diodes, into a waveguide. Compromises are usually made to accommodate the need of DC bias; and consequently, the advantages of SIW structure are not fully utilized and the solution is suboptimal. In this work we propose a new SIW structure, called the corrugated SIW (CSIW), which does not require conducting vias to achieve TE₁₀ type boundary conditions at the side walls. Instead, the vias are replaced by quarter wavelength microstrip stubs arranged in a corrugated pattern on the edges of the waveguide. This, along with series interdigitated capacitors , results in a waveguide section comprising two separate conductors, which facilitates shunt connection of active components such as Gunn diodes . The concept of this arrangement is shown in Fig. 1.