Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Patent
1982-11-04
1985-09-03
Blum, Theodore M.
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
455306, 343417, G01S 124
Patent
active
045395667
ABSTRACT:
An auto notch system which automatically "notch" filters up to four interference signals (interferers) in the band from 50 KHz to 150 KHz comprises a signal detector, an adjustable notch filter, a bandpass receiver and a digital controller, plus the software that runs in the digital controller. The signal detector circuit has an antenna, a preamplifier and a group of "fixed" filters. The adjustable notch filters are four circuits, each includes an active notch type filter stage with a DAC (digital to analog converter) in series with the input resistor to allow gain control and another DAC that controls the current through a diode that is optically coupled to a light dependent resistor pair. The light resistor pair is in the filter loop and as the resistance varies the frequency response of the filter changes. Thus the frequency response is controlled by varying the diode current. The bandpass receiver is used to sense and amplify the signal output of the Loran bandpass filter or the signal output of the notch filters under control of the controller. The bandpass receiver is tuned by the controller to one 128 specific frequencies in the range from 50 KHz to 150 KHz. The controller tunes the bandpass receiver, selects its input signal source and controls the gain and frequency characteristics of the notch filters. The software commands these hardware functions.
REFERENCES:
patent: 4134117 (1979-01-01), Robinson et al.
patent: 4395779 (1983-07-01), Fujino et al.
patent: 4461036 (1984-07-01), Williamson et al.
Ho Cecil C.
Sharpe Claude A.
Bandy Alva H.
Blum Theodore M.
Heiting Leo N.
Sharp Melvin
Texas Instruments Incorporated
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