| 摘要 |
In order to generate a signal for canceling a chirped signal, a transmitter generates a cancellation signal along with the transmitted signal, using a single term variable complex gain multiplier adapted to cancel the chirped signal only at its instantaneous frequency, rather than attempting to cancel it with a complex FIR filter that works over the entire bandwidth of the chirped signal. The cancellation signal is varied in amplitude and phase as a function of the frequency of the chirped transmit signal for which it is intended to compensate. Since the signal that is to be cancelled is essentially sinusoidal but swept through a frequency range, the cancellation signal for the instantaneous transmit signal needs to be swept in both amplitude and phase in unison with the change in frequency of the transmit signal in order to accommodate gain and phase changes in the transmitted signal as a function of frequency. Particularly, the gain as well as the phase of the transmit signal generally will vary as a function of frequency due to limitations of the signal generation circuitry. Therefore, the cancellation signal must be varied in both amplitude and phase as a function of frequency. The necessary algorithm for changing the amplitude and/or phase of the cancellation signal as a function of frequency of the transmit signal can be readily determined by conventional techniques during a training session.
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