Claims
- 1. An antenna performance monitor comprising:
- an antenna sensor for coupling to an antenna radiating a radio frequency signal, wherein said antenna sensor generates signals Vm and Im representative of an input voltage and an input current respectively of said antenna;
- an A/D converter coupled to said antenna sensor for digitizing samples of said signals Vm and Im; and
- a data processor coupled to said A/D converter for generating outputs representative of an impedance magnitude and an impedance phase angle of said antenna substantially concurrently for each frequency of said radio frequency signal.
- 2. The antenna performance monitor of claim 1 wherein said antenna sensor comprises a capacitive voltage divider and a current transformer.
- 3. The antenna performance monitor of claim 1 wherein said A/D converter comprises anti-aliasing filters.
- 4. The antenna performance monitor of claim 1 wherein said A/D converter comprises a digitizer having a sampling rate of at least twice a highest frequency of said radio frequency signal.
- 5. The antenna performance monitor of claim 1 wherein said antenna sensor is coupled to said A/D converter by a double shielded coaxial cable.
- 6. The antenna performance monitor of claim 1 wherein said antenna sensor is coupled to said A/D converter by a fiber optic link.
- 7. The antenna performance monitor of claim 1 wherein said data processor comprises the following functions:
- a bandpass filter coupled to said A/D converter having a center frequency substantially equal to a midpoint of said radio frequency signal for bandpass filtering said samples of said signals Vm and Im;
- a mixer coupled to said bandpass filter for forming a complex product of said samples of said signals Vm and Im with a signal representative of each frequency respectively in said radio frequency signal;
- a lowpass filter coupled to said mixer for generating a filtered complex baseband of said complex product;
- a decimator coupled to said lowpass filter for generating a resampled complex baseband of said filtered complex baseband at a reduced sample rate;
- a complex FFT transform coupled to said decimator for generating complex spectral coefficients of said signals Vm and Im from said resampled complex baseband;
- an averager coupled to said complex FFT transform for generating averaged complex spectral coefficients of said signals Vm and Im from said spectral coefficients;
- a voltage magnitude function coupled to said averager for generating a voltage magnitude of said averaged complex spectral coefficients for said samples of said signal Vm;
- a current magnitude function coupled to said averager for generating a current magnitude of said averaged complex spectral coefficients for said samples of said signal Im;
- a magnitude divide function coupled to said voltage magnitude function and said current magnitude function for generating the quotient of said voltage magnitude divided by said current magnitude for a plurality of frequencies within said radio frequency signal;
- a voltage divide function coupled to said averager for generating a voltage quotient of each real part of said averaged complex spectral coefficients for said signal Vm divided by its corresponding imaginary part;
- a current divide function coupled to said averager for generating a current quotient of each real part of said averaged complex spectral coefficients for said signal Im divided by its corresponding imaginary part;
- a voltage arctangent function coupled to said voltage divide function for generating a voltage phase signal from each said voltage quotient;
- a current arctangent function coupled to said current divide function for generating a current phase signal from each said current quotient; and
- a difference function coupled to said voltage arctangent function and said current arctangent function for generating the difference of said voltage phase signal minus said current phase signal for said plurality of frequencies in said radio frequency signal.
LICENSING INFORMATION
The invention described below is assigned to the United States Government and is available for licensing commercially. Technical and licensing inquiries may be directed to Harvey Fendelman, Patent Counsel, Space and Naval Warfare Systems Center, Code D0012, 53510 Silvergate Avenue Room 103, San Diego, Calif. 92152-5765; telephone no. (619)553-3818; fax no. (619)553-3821.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
5233537 |
Tietsworth |
Aug 1993 |
|
5887038 |
Golden |
Mar 1999 |
|