An experimental technique used to measure the unloaded Q of microstrip antennas

We present a scattering method for measuring the unloaded Q of a prototype microstrip (patch) antenna structure without the need to implement connecting circuitry. The patch antenna is placed on a large reflecting ground plane. Two auxiliary antennas are used. Antenna number 1 acts as a transmitting antenna and is oriented at an angle of approximately 45/spl deg/ with respect to the x-y plane. Antenna number 2 acts as a receiving antenna and is oriented along the z-direction normal to the ground plane directly above the patch antenna. This orientation places it in a near minimum of the specular beam. Both antennas are properly polarized with respect to the desired radiation field of the patch antenna. Ideally, such a measurement system would be placed in an electromagnetic anechoic chamber.