Abstract: A heterodyne receiver comprising a gain controllable RF mixer (14) which has a first input connected to a first local oscillator (16) and a second input connected to an RF input. The receiver comprises a peak detector (38) which detects a peak value of an input signal at the second input of the HF mixer and generates a digital control signal if it is determined that the peak value of the input signal is above a predetermined level. A digital automatic gain control circuit (34) decreases upon reception of the digital control signal the gain of the RF mixer.

Abstract: A heterodyne receiver comprising a gain controllable RF mixer (14) which has a first input connected to a first local oscillator (16) and a second input connected to an RF input. The receiver comprises a peak detector (38) which detects a peak value of an input signal at the second input of the HF mixer and generates a digital control signal if it is determined that the peak value of the input signal is above a predetermined level. A digital automatic gain control circuit (34) decreases upon reception of the digital control signal the gain of the RF mixer.

Abstract: A digital audio broadcast (DAB) receiver (10) for receiving an RF signal comprises a low noise amplifier (16), an RF mixer (24) that generates an intermediate frequency signal, and a voltage controlled oscillator (23). The receiver includes a tracking filter (18) downstream of the low noise amplifier (16) and upstream of the RF mixer (24), wherein the tracking filter is tuned to track a selected channel frequency out of the received RF signal. In a described embodiment, the tracking filter includes a bandpass filter (20) and a notch filter (22). A center frequency of the bandpass filter is tuned to track the selected channel frequency; and an attenuation notch of the notch filter is tuned to track a frequency which is separated from the selected channel frequency by a fixed frequency; the attenuation notch of the notch filter is tuned together with the center frequency of the bandpass filter, and the center frequencies of the notch filter and the bandpass filter are separated by a fixed frequency.

Abstract: A composite video signal each line of which comprises a line synchronizing pulse, a front and a back porch and a vision portion, the synchronizing pulse of which may contain a burst of pulsed additional information is applied to an input terminal (1) which is connected to the input of a first signal path (T1, T2) whose output is connected to a current source (I1) and to an output terminal (8). A second signal path (T3, T4) has its input connected to a reference voltage input (5) and its output connected to the current source (I1) and the output terminal (8). A switching circuit (T5, T6) alternately enables the first and second signal paths (T1, T2; T3, T4) under the control of a switching signal at a connection (10) such that the output terminal (8) produces a composite video signal in which the synchronizing pulse at the input terminal is replaced by a pulse or level. The replacement does not contain the burst of pulsed additional information when present in the applied signal.