Zero-Gap Waveguide: A Parallel Plate Waveguide With Flexible Mechanical Assembly for mm-Wave Antenna Applications

Abstract

A new gap waveguide concept is presented, where the air gap between the perfect electric conductor and artificial magnetic conductor (AMC) parallel plates of a conventional gap waveguide structure has been reduced to almost zero. When the air gap is reduced, the periodic metal pin layer (which emulates the AMC characteristics) may come in contact with the top metal layer. A statistical analysis of a random contact of the pin texture and the top metal plate in this new type of gap technology guiding structure, so-called zero-gap, is elaborated in this paper. The periodic pin texture creates a stopband for parallel plate modes, and it is also used as a mechanical support while assembling the waveguide structure. This presents a significant manufacturing advantage, especially for corporate feed-network of array antennas at millimeter-wave frequencies. A $V$ -band $8\times 8$ slot array fed with this new waveguide is also designed and manufactured to show the potential of this newly proposed zero-gap waveguide structure. The measured results show 20% of relative impedance bandwidth ( $|S_{11}| dB) and an overall antenna efficiency larger than 60% over the 56.5–69-GHz frequency band.