  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 3-port waveguide
T-junction which is modified to a LWA unit cell with an internal matching
mechanism to suppress the stop-band 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 be either be
allowed to radiate in free-space or kept confined inside a PPW structure. The
proposed side-fire structure thus can be completely shielded useful as an
analog broadband spectrum analyzer using 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 GHz - 66 GHz providing 1 GHz frequency resolution. Furthermore, a
simple mathematical model consisting of array of line sources is proposed to
efficiently model the beam-scanning characteristics of the curved side-fire LWA
in the near-field of the structure.
