A ka-band butler matrix with antenna array based on micromachined rectangular coaxial structures

A Ka-band 4×4 Butler matrix feeding a 4-element linear antenna array has been presented in this paper. The Butler matrix is based on a rectangular coaxial structure, constructed using five layers of gold coated micromachined silicon slices. The patch antennas are of an air-filled microstrip type, and spaced by half a wavelength at 38 GHz to form the array. The demonstrated device is 26 mm by 23 mm in size and 1.5 mm in height. The measured return losses at all input ports are better than −10 dB between 34.4 and 38.3 GHz. The measured radiation pattern of one beam has shown good agreement with the simulations.