60 GHz ASK modulator using switchable FSS

A switchable frequency selective surface (FSS) designed to operate as a free space amplitude shift keying (ASK) modulator at 60 GHz is presented. The FSS is based on rectangular loop aperture geometry, with each unit cell having two PIN diodes across the aperture at 180 degree interval. This makes the FSS operate in only one polarization i.e. either TE or TM depending on the orientation of the incident electric field. To minimize the effect of bias line on the overall frequency response of the FSS, an orthogonal negative dc bias line, which is connected to the center of the FSS unit cell, has been placed on the rear surface of the dielectric substrate. Positive dc biasing is provided from the front side of the FSS structure. Theoretically, a transmission loss of about 21 dB can be achieved by switching PIN diodes to ON from OFF state. Preliminary theoretical results are described.