Signal monitor utilizing digital signal processing

A method of extracting azimuth information from a VOR signal for evaluation to ensure that the transmitted signal in space remains within tolerance, said method comprising the steps of:

• subjecting the VOR signal to detection and presenting the detected signal as digital data,
• digitally processing said data in the time domain to derive a reference signal component and a low frequency signal component having an azimuth-dependent phase, one of said components appearing on said VOR signal as amplitude modulation and the other of said components appearing thereon as frequency modulation,
• subjecting said signal components to further digital processing to extract phase information therefrom, and
• determining from said phase information the relative phase between said signal components.

Apparatus for extracting predetermined parameters of a VOR signal for evaluation to ensure that the transmitted signal in space remains within tolerance, said apparatus comprising:

• means responsive to the VOR signal for subjecting the same to detection and presenting the detected signal as digital data in the time domain,
• time domain processing means responsive to said digital data for digitally processing said data in the time domain to derive the amplitude of a subcarrier included in said data, a reference signal applied to said subcarrier as frequency modulation, and a low frequency signal component having an azimuth-dependent phase appearing on said VOR signal as amplitude modulation,
• frequency domain processing means for receiving said reference signal and said signal component and digitally processing the same to extract amplitude and phase information therefrom, and
• means for computing said parameters from the extracted amplitude and phase information and the amplitude of said subcarrier.

Apparatus for extracting azimuth information from a VOR signal for evaluation to ensure that the transmitted signal in space remains within tolerance, said apparatus comprising:

• means responsive to the VOR signal for subjecting the same to detection and presenting the detected signal as digital data in the time domain,
• time domain processing means responsive to said digital data for digitally processing said data in the time domain to derive a reference signal component and a low frequency signal component having an azimuth-dependent phase, one of said components appearing on said VOR signal as amplitude modulation and the other of said components appearing thereon as frequency modulation,
• frequency domain processing means for receiving said signal components and digitally processing the same to extract phase information therefrom, and
• means for determining from said phase information the relative phase between said signal components.