A battery-free identification transponder is presented. It incorporates a dual-beam angle-diversity leaky-mode antenna array, connected to two power divider/combiner networks. The integrated antenna shows 20.4 dBi directivity and 16.3 dB gain by measurement The first-trial designs also include an RF-to-DC converter of 20% efficiency and an oscillator of 18% DC-to-RF efficiency. By placing two horn antennas in the base station, one at 1 meter away for sending the interrogating CW signals and another at 2.5 meters away for receiving the coded, modulated signals from the transponder, we obtain the demodulated signals matched identically to the coding signals at the transponder for data rates up to 15K bps.