Abstract: A security system suitable for retail establishments carrying articles comprises tags for affixing to the articles, the tag being capable of generating a responsive microwave signal in response to a microwave detection signal; and at least one transceiver for generating the microwave detection signal and for receiving the responsive microwave signal.

Abstract: Methods and systems for calibrating an array antenna are described. The array antenna has a plurality of antenna elements each having a signal with a phase and an amplitude forming an array antenna signal. For calibration, the phase of each element signal is sequentially switched one at a time through four orthogonal phase states. At each orthogonal phase state, the power of the array antenna signal is measured. A phase and an amplitude error for each of the element signals is determined based on the power of the array antenna signal at each of the four orthogonal phase states. The phase and amplitude of each of the element signals is then adjusted by the corresponding phase and amplitude errors.