| 摘要 |
A noise blanker which has circuitry that enables the threshold level of noise blanking to track the average background noise level is disclosed. In general, a controllable gate (20) receives an input signal and selectively passes and blocks the input signal in response to received noise blanking pulses which are generated in response to high peak magnitude noise impulses. A signal (27, Fig. 4A) related to background and impulse noise is extracted from an input signal. A controllable gain noise amplifier (31) is utilized to amplify the separated background and impulse noise and negative feedback circuitry (35, 37, 39; 50, 52, 39) is utilized to maintain the average peak output (33, 54) of the noise amplifier substantially constant except for occasional large magnitude noise impulses which do not substantially change the average peak magnitude of the background and impulse noise. The output (32, 36, 51) of the controllable noise amplifier (31) is applied to a threshold switch means (35, 40, 41, 50, 53, 41) which produces blanking pulses (47) in response to the amplified noise signal having a peak exceeding a magnitude (43; 56) which is greater than the substantially constant peak output level of the noise amplifier. This results in a blanker circuit in which the threshold level of the blanking pulses closely tracks the average peak value (33; 54) of the background and impulse noise. |
