Millimeter-Wave Integrated Side-Fire Leaky-Wave Antenna and Its Application as a Spectrum Analyzer

An analog, low-profile and shielded spectrum analyzer is proposed for operation at mm-wave frequencies around the 60 GHz band based on a novel side-fire leaky-wave antenna (LWA) configuration. The proposed side-fire periodic LWA is systematically developed from a conventional three-port waveguide T-junction which is modified to a LWA unit cell with an internal matching mechanism to suppress the stopband and enable broadside radiation based on unit cell symmetry considerations. The resulting periodic side-fire antenna radiates in the plane of the antenna, whereby the leakage power can either be allowed to radiate in free-space or kept confined inside a parallel-plate waveguide (PPW) structure. The proposed side-fire structure can therefore be completely shielded, making it useful as a broadband spectrum analyzer that is compatible with substrate-integrated waveguide (SIW) technology. Furthermore, a convex side-fire antenna is demonstrated to focus the radiated beams in the near-field of the structure to make the entire system compact. The integrated spectrum analyzer is experimentally demonstrated between 59 and 66 GHz providing 1 GHz frequency resolution. Furthermore, a simple mathematical model consisting of an array of line sources is used to efficiently model the beam-scanning characteristics of the curved side-fire LWA in the near-field of the structure.