Abstract: A receiver for broadcast signals, e.g. DAB, FM, DVB, and digital or analog short-wave RF broadcast signals according to the present invention includes a polyfunctional circuit (5) that can be switched into three modes and performs the digital frequency demodulation which is needed for the reception of a frequency modulated signal in a first mode A, a digital frequency adjustment of the receiver in case of the reception of a digital or analog modulated broadcast signal like DAB, DVB, DRM or AM in a second mode B and the digital frequency adjustment and the digital gain control of the receiver which is needed in case of the reception of a digitally modulated broadcast signal like DAB, DVB, DRM in a third mode C. Depending on the needed functionality not all of these modes need to be realized. Nevertheless, the same hardware will be used for different purposes although the circuit is realized with an optimized amount of hardware to realize an efficient receiver.

Abstract: A switching amplifier generates noise at its switching frequency and harmonics thereof. The noise at these harmonics, for an audio amplifier, will be generated with significant amplitude in the AM band. Thus, an AM tuner will experience interference problems if the tuner frequency is sufficiently close to one of these harmonics. To avoid this problem the switching frequency of the switching amplifier is chosen based on the tuner frequency. Thus, the switching frequency is chosen to avoid having harmonics at or too near the chosen tuner frequency. The switching amplifier is disabled when the tuner is in seek or scan mode. Instead of using the tuner frequency to determine what switching frequency should be used to avoid interference, the interference can be detected directly to cause a change in the switching frequency and thus remove the interference.

Abstract: A method for tuning a cavity filter is provided. The cavity filter includes a plurality of tuning members. The method includes selecting a stored set of positional values for the tuning members, driving the tuning members of the cavity filter to the stored set of positional values, and further adjusting the position of the tuning members as necessary to achieve a desired frequency response for the cavity filter.

Abstract: An automatic radio frequency signal switching circuit is equipped with a plurality of AV input terminals and adopts an analog/digital adapter to transform all respective input analog signals into high level digital signals and a central processor is used to memorize the sequential orders of the respective AV signals which are sequentially output in a last-in-first-out manner to a television. At the same time, the central processor shuts off the ANT/CATV signal amplifier and the RF switch thereof so as to effect automatic switching operation. When no AV signals from AV equipment are being input, the central processor will instantly transmit another set of high electric level signals to the ANT/CATV signal amplifier and a power source of the RF switch thereof and the ANT/CATV signals are delivered to a television via the RF amplifier and the RF switch thereof whereby effect automatic RF switching operation.

Abstract: A setting apparatus for setting the tuning voltage of a tunable resonant circuit has an amplification device which amplifies an oscillator tuning voltage, output by a phase locked loop, nonlinearly to produce the tuning voltage. The gain of the amplification device can be set by a digital gain control signal. The signal resolution of the setting apparatus can be controlled in different ways as a function of the gain by using two differently driven digital/analog converters.