Microstrip patch antennas on corrugated substrates

Periodic corrugations on the metallized backside of a microstrip dielectric substrate enhance the effective permittivity well beyond the bulk material permittivity. This is achieved by corrugations whose depths and period are both much smaller than the wavelength. Straight microstrip lines as well as rectangular, circular and annular ring patch antennas of small size have been designed using corrugated substrates of low bulk permittivity. A size reduction corresponding to a reduction in resonance frequency of the antennas of 25-40% can be achieved easily using this new approach.