Abstract: A microwave detector, which integrates two circular patch antennas with a detector diode. The high impedance at the edge of the circular patch antenna is combined with 180.degree. out of phase electric fields at diametrically opposite points, so as to match to the RF impedance of a zero or small DC bias diode. The result is a very simple, high-sensitivity narrow-band microwave integrated detector.

Abstract: An electronic identification system comprising a transmitter for generating an electromagnetic excitation signal, one or more portable transponders for storing variable identification data, and for transmitting an information signal containing the identification data upon entering the field. Transmission of the information signal is independent of the excitation signal in both time and frequency. A radio frequency receiver is provided for receiving the information signal and in response generating output signal representing the variable identification data contained in the information signal.

Abstract: A battery housing comprising a main body portion, a socket in the main body portion shaped to receive a battery, contacts disposed at one end of the socket adapted to connect with correspondingly disposed electrodes on the battery, and a lid adapted to open and close over the socket, the lid including means for urging the battery electrodes into close connection with the contacts.