Design of Wideband Waveguide-to-Microstrip Transition for 60 GHz Frequency Band

Abstract

Introduction. The frequency band around 60 GHz is one of the most promising to realize new generation communication systems with high data rate due to the utilization of a wide operational frequency band that significantly exceeds traditional frequency bands below 6 GHz. High interest in the development of 60 GHz communication systems is related to the recent evolution of MMIC technology that allows creating effective components for this band and the variety of planar devices. Both are typically realized on printed circuit boards and have interfaces that are based on microstrip lines. The wideband waveguide-to-microstrip transition is required to test various active and passive planar devices with microstrip interfaces in order to provide an effective interconnection between the standard waveguide interface of measurement equipment and planar microstrip structures.Objective. The paper deals with the design of planar wideband waveguide-to-microstrip transition with low insertion loss level in the 60 GHz frequency band.Materials and methods. The main objective is achieved by analyzing of discontinuities in waveguide-tomicrostrip transition structure and their influence on transition characteristics. The transition characteristics are analyzed using full-wave electromagnetic simulation and confirmed with experimental investigation of designed wideband waveguide-to-microstrip transition samples.Results. The designed transition is based on an electromagnetic coupling through a slot aperture in a microstrip line ground plane. The transition is performed without using blind vias in its structure that provides low production cost and al-lows integrating the WR-15 rectangular waveguide in a simple manner without any modifications in the waveguide structure. Results of the electromagnetic simulation are confirmed with experimental investigations of the fabricated waveguide-to-microstrip transition samples. The designed transition provides operation in the nominal bandwidth of the WR-15 waveguide, namely, 50…75 GHz with the insertion loss level of 2 dB and with less than 0.8 dB insertion loss level at the 60 GHz frequency.Conclusion. The designed waveguide-to-microstrip transition can be considered as an effective solution for interconnection between various waveguide and microstrip millimeter-wave devices due to its wideband performance, low insertion loss level, simple integration and robustness to the manufacturing tolerances structure.