Gp. Gauthier et al., MICROSTRIP ANTENNAS ON SYNTHESIZED LOW DIELECTRIC-CONSTANT SUBSTRATES, IEEE transactions on antennas and propagation, 45(8), 1997, pp. 1310-1314
Micromachining techniques using closely spaced holes have been used un
derneath a microstrip antenna on a high dielectric-constant substrate
(epsilon(r) = 10.8) to synthesize a localized low dielectric-constant
environment (epsilon(r) = 2.3). The measured radiation efficiency of a
microstrip antenna an a micromachined 635-mu m thick epsilon(r) = 10.
8 Duroid 6010 substrate increased from 48 +/- 3% to 73 +/- 3% at 12.8-
13.0 GHz (including 3,3-cm feed line losses). We believe that this tec
hnique can be applied to millimeter-wave antennas (microstrip, dipoles
, slots, etc,) on silicon and GaAs substrates to result in relatively
wideband (3-6%) monolithic microwave integrated circuits (MMIC) active
antenna modules for phased-arrays and collision-avoidance systems.