A low-cost active antenna for short-range communication applications

A low-cost active antenna to be used in a miniature microwave transponder is presented, This active antenna operating at 9.9 GHz consists of a compact microstrip array antenna of electromagnetically gap-coupled rectangular resonators and a novel ASK demodulator/differential phase-shift keying (DPSK) modulator circuit, In order to minimize the power consumption and to reduce the cost of the active antenna, this novel microwave circuit employs a single "cold" MESPET which performs both the modulator and demodulator functions, The original methods used to realize the active antenna provide high performance, size reduction, and low power consumption.