Mj. Vaughan et al., IMPROVEMENT OF MICROSTRIP PATCH ANTENNA RADIATION-PATTERNS, IEEE transactions on antennas and propagation, 42(6), 1994, pp. 882-885
Microstrip patch antennas typically have radiation patterns containing
unwanted sidelobes or local minima caused by surface waves, especiall
y when fabricated on high dielectric-constant substrates. This communi
cation shows that removal of the substrate beneath the patch can great
ly improve the pattern. A variation of this technique, compatible with
monolithic fabrication, is applied to fabrication of a patch on GaAs
and shows similar pattern improvement.