Coaxial End-Launched and Microstrip to Partial $H$-Plane Waveguide Transitions

Conventional rectangular waveguides are commonly used for high power and other microwave and millimeter-wave applications. Their use at lower frequencies has been limited by their bulky nature. A new type of compact waveguide called a partial H-plane waveguide has previously been proposed that has only one quarter of the cross-sectional area of a conventional waveguide. However, only limited information relating to the feeding of such waveguides is available. This paper presents two types of transitions to partial H-plane waveguides from the coaxial and microstrip transmission mediums. Additionally, in the coaxial case, the transition is end-launched to offer collinear properties. The development of both transitions is discussed and optimized designs presented with simulated and measured results over H-band (3.95-5.85 GHz).