Millimeter-wave Dual-Function Hollow Metal Waveguide to Microstrip Transition and Bandpass Filter based on ENZ Metamaterial

This paper presents a novel design of a millimeterwave dual-function in-plane hollow metal waveguide to microstrip transition and bandpass filter based on epsilon-near-zero (ENZ) metamaterial. A hollow metallic rectangular waveguide (HMRW) that operates near its cut-off frequency of the fundamental TE
₁₀
mode is used to mimic the ENZ metamaterial, allowing the wave to tunnel through the waveguide with an effectively infinite phase-velocity. As a waveguide transition, the ENZ waveguide directly interconnects HMRW and microstrip in the same plane with a minimum insertion loss of 0.7 dB at the 33.06 GHz, overcoming the significant impedance mismatch and geometry difference between HMRW and Microstrip. As a bandpass filter, the design has a near-flat passband with the minimum insertion loss of 0.7 dB and a bandwidth of 1.31 GHz centered at 32.96 GHz, which leads to a Q-factor of 25.17. The work offers a step towards a novel dual-function waveguide transition and bandpass filter that can be used in a variety of functional components for millimeter-wave multichip modules and hybrid integrated circuits.