Method and apparatus for interference cancellation at base-band

Details Method and apparatus for interference cancellation at base-band Method and apparatus for interference cancellation at base-band

1977-09-16

1980-03-04

Richardson, Robert L.

Demodulators

Amplitude modulation demodulator

Having specific distortion, noise or other interference...

325363, 325 65, 329137, H04B 110

Patent

active

041919262

ABSTRACT:
The interference components in a first composite signal are cancelled at baseband frequencies using a second composite signal. The first composite signal has a desired carrier and an interfering carrier. The desired carrier has a constant envelop and is angle modulated with baseband .phi..sub.1 (t). The interfering carrier has any type of modulation. The second composite signal has the interfering carrier. The first composite signal is angle demodulated. The first composite signal is also multiplied with the second composite signal. The product signal from the multiplier has a high and a low frequency component. The low frequency component is extracted from the product signal. The low frequency component is phase shifted by plus 90 degrees when the instantaneous frequency of the desired carrier is greater than the instantaneous frequency of the interfering carrier. When the instantaneous frequency relationship is reversed, the low frequency component is phase shifted by minus 90 degrees. The phase shifted signal is attenuated and then subtracted from the angle demodulated signal, yielding the desired signal component with the interference components cancelled or substantially attenuated. The above technique may be used with a F. M. desired carrier when the angle demodulator is a frequency demodulator.

REFERENCES:
patent: 3896385 (1975-07-01), Chitre et al.
patent: 3963990 (1976-06-01), DiFonzo
patent: 3986123 (1976-10-01), Tirro et al.

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