Patent Number: 05999889&
Section: summary

BACKGROUND OF THE INVENTION The present invention relates to the measurement of antenna performance parameters in real time. More specifically, but without limitation thereto, the present invention relates to the measurement of voltage, current, resistance, and reactance of a transmitting antenna during normal broadcast. Previous methods for measuring antenna performance typically required the transmission of a CW signal, which meant interrupting normal communications during the measurement period. The possibility of an undetected malfunction while the transmitter was operating is a factor limiting the confidence in the capability of a communications system. U.S. Pat. No. 5,233,537 issued on Aug. 3, 1993 and incorporated herein by reference thereto describes a system that solves the problem of testing an antenna while transmitting a frequency shift-keyed signal. FIG. 2 of this patent shows the four components used to measure antenna operating parameters: a sensor to generate a signal representative of antenna feed point voltage and current, a sampling trigger circuit, an A/D converter, and a data processing unit to calculate antenna performance from the sampled voltage and current. Because the antenna parameters change with the frequency of the signal being transmitted, the sampling trigger is required to gate samples to the A/D converter during the time periods when the frequency being measured is transmitted. Separate measurements are performed at each transmission frequency. A continuing need still exists, however, for an antenna performance monitor that is not dependent on knowledge of the frequency excursions of the transmitted signal. SUMMARY OF THE INVENTION An antenna performance monitor of the present invention is directed to overcoming the problems described above, and may provide further related advantages. No embodiment of the present invention described herein shall preclude other embodiments or advantages that may exist or become obvious to those skilled in the art. An antenna performance monitor of the present invention comprises an antenna sensor for coupling to an antenna radiating a radio frequency signal. The antenna sensor generates signals Vm and Im representative of the antenna input voltage and current. An A/D converter is coupled to the antenna sensor for digitizing signals Vm and Im. A data processor is coupled to the A/D converter for generating outputs representative of impedance magnitude and phase angle of the antenna substantially concurrently with changes in frequency of the radio frequency signal. An advantage of the antenna performance monitor is that the performance parameters of an antenna may be measured while connected to an operating transmitter. Another advantage is that no sampling trigger is required to select specific transmission frequencies. Yet another advantage is that antenna performance parameters may be broadcast virtually in real time within the transmitted signal or over other comunnication links. The features and advantages summarized above in addition to other aspects of the present invention will become more apparent from the description, presented in conjunction with the following drawings.