Gap Waveguide PMC Packaging for Improved Isolation of Circuit Components in High-Frequency Microwave Modules

In this paper, perfect magnetic conductor (PMC)-based packaging technique was used to improve the isolation performance among various microwave circuit components such as high-gain amplifier chains. In this approach, a periodic structure (such as metal pin rows) together with the ground plane of the substrate created a stopband for unwanted parallel plate or cavity modes as well as substrate modes, and thereby suppressed the problems of circuit resonances and related package phenomena. This paper describes two Ka-band amplifier chains that were tested with this new packaging technique. Firstly, a single amplifier chain was tested for maximum stable gain operation, and it was found that the stable gain of was achieved, whereas traditional metal wall package with RF absorber offered stable gain of 40 dB, thus showing significant isolation improvement. Secondly, two high-gain amplifier chains were placed side by side and their mutual isolation was tested. With the proposed gap waveguide packaging, a minimum isolation of 78 dB was achieved, whereas a complete metal shield provided a minimum isolation of only 64 dB over the band of interest.