A Mode-Suppressing Metasurface for Large-Width MMICs Suitable for Tightly Packaged Millimeter and Submillimeter Heterodyne Receivers

When packaging large-width microwave integrated circuits, care has to be taken to avoid structures that could sustain unwanted oscillations. Unfortunately, this situation may not be attainable since large holding cavities are prone to support parasitic waveguide modes that could produce a feedback loop which, in turn, is especially dangerous in high-gain components with poor match with subsequent elements. This letter presents an scalable metasurface, implemented as a gap-waveguide perfect magnetic conductor, suitable to overcome this problem in millimeter- and submillimeter-band receivers. The proposed solution was integrated into a compact $W$-band (75-110 GHz) receiver where a large chip-width amplifier was placed near a mixer, thus generating oscillations at high-gain levels compromising its operation at some frequencies. The metasurface was incorporated at the top of the amplifier's cavity where it did not only suppressed completely the oscillation, but also increased isolation between components. As a result, the receiver became fully operational as attested by measurements of its noise temperature at the compromised frequencies.