Broadband Planar Microstrip-to-WR12-Waveguide Transition for E1 band Transceiver Application

This paper presents a broadband planar microstrip-to-WR12-waveguide transition based on a planar probe. The transition comprises a dielectric substrate mounted on a metal plate, accompanied by an open-ended WR12 waveguide. The probe, acting as the termination point of the microstrip line, is inserted into the waveguide on the upper surface of the dielectric substrate. The matching patch is created through etching technology on the center ground plane of the dielectric substrate's backplane. In the conventional transition, via-hole placement around the rectangular waveguide and microstrip line prevents power leakage caused by the presence of multiple transmission modes. In the case of a broadband planar microstrip-to-waveguide transition, via-hole positioning is employed to introduce inductance and effectively restrict the dominance of the single-transmission mode. By optimizing the matching patch length and the distance between via holes and edge of waveguide short, resonance occurs at 73.5GHz, and impedance matching can be obtained by controlling the insertion length of the microstrip line. In contrast to conventional configurations, this transition excels at simultaneously satisfying the demanding criteria of high frequency, wide bandwidth, and low insertion loss, and can cover the higher frequency band of the El band (71-76GHz). A back-to-back prototype has been successfully fabricated and tested. The obtained results exhibit the insertion loss of transition is 0.36dB at 73.5GHz and the reflection characteristics is exceptionally outstanding in full El band.