A WAVEGUIDE SHUNT-SLOT FEED FOR MICROSTRIP PATCH ANTENNAS

Abstract

Waveguide slot feeds for microstrip patch antennas are a relatively. recent concept. They offer the advantage of reduced transmission-line losses which is an important factor at millimeter frequencies. A further advantage of using a waveguide at these frequencies is the mechanical rigidity provided by it. This dissertation presents a study of the waveguide shunt-slot feed for microstrip antennas. A theoretical analysis procedure using the Method of Moments has been developed utilizing entire domain sinusoidal basis functions. A computer program i.n FORTRAN has been written to implement the analytical procedure. The. proposed antenna was fabricated on an RT-5880 Durold substrate for operation in the X-band. Impedance •and VSWR measurements were carried out upon the antenna using the HP8720B Vector Automatic Network Analyzer. The resul (n show Chat. l.he patch resonant Frequency as well. as the input VSWR are strong functions of slot offset. Further, the radiation pattern measurements indicate that higher order modes are excited because of the impedance loading of the patch by the feed slot It is concluded that although this feeding technique is feasible and has some potential advantages, more detailed study of waveguide-slot &.slot-patch interactions Is required to evolve a suitable design procedure.