Thomson Licensing

Thomson Licensing S.a.

Alfred Selz

Veit Armbruster

A single conversion tuner suitable for receiving RF signals having different requirements as to selectivity, linearity and image rejection is presented. Tuners of this kind are particularly useful for digital terrestrial as well as cable reception, where different modulation schemes require very high image rejection ratios on one hand and high linearity or pass band flatness on the other hand. The inventive tuner features a double-tuned tuneable filter in combination with an image reject mixer. The double-tuned filter provides excellent pass band flatness, while the image reject mixer provides a high intrinsic image rejection. The image rejection ratio of the combination of image reject mixer and tuneable filter is very high and fulfils the requirements of commonly used modulation schemes such as 8VSB, while the pass band flatness is compliant with the requirements for modulation schemes such as QAM.

Single conversion tuner

In a receiver, provision is made of a tuneable switchable bandpass filter comprising a primary resonant circuit and a first secondary resonant circuit. A second secondary resonant circuit can be switched into a part of the first primary resonant circuit, thereby producing a second primary resonant circuit. By virtue of the embodiment of the primary resonant circuit, the bandpass filter is switchable in terms of frequency range with little outlay on circuitry and, on account of the individual embodiment of a first and second secondary resonant circuit with individual coupling elements, can be optimized with regard to a constant amplitude response.

Switchable tuneable bandpass filter with optimized frequency response

In apparatuses (1, 2, 3) controlled or operated via an IC bus, it may be necessary to take measures to suppress interference signals at the data signal input/output of the respective apparatus without impairing the data transport at the same time. The data line at the data signal input/output contains an RC element, in the form of a low-pass filter, with a diode connected in parallel with the RC element, the low-pass filter action allowing the arrangement to be used to suppress interference signals acting on the data signal input/output, and, secondly, the transmissive action of the diode meaning that the arrangement does not impair a data signal leaving the data signal input/output.

Data bus

The oscillator having a tunable resonant circuit has a switch for expanding the tuning range, which is connected in series with two coils jointly determining the oscillation frequency of the resonant circuit. A further coil, which is coupled to the resonant circuit in the region of the switch, is used to supply a switching voltage for the switch. In this arrangement, the other end of this third coil is coupled to a reference potential, with a capacitor, which acts as a short circuit for radio-frequency purposes, decoupling the switching voltage from the reference potential. Since the switching voltage is in this case coupled to an oscillator circuit node which is earthed for radio-frequency purposes, it is of no significance in this case which resistor is used to couple the switching voltage. This means that the resonant circuit is not resistively damped by the connection of the switching voltage. Coupled to the other end of the switching diode is a further component, preferably a fourth coil, which has the same inductance as the third coil, in order to dissipate the switching voltage. The first two coils are advantageously of the same size, so that this circuit coil jointly determining the oscillation frequency is earthed by the third coil exactly at its center. This means that the quality factor and the oscillation properties of the resonant circuit are not adversely affected.

Growing community of inventors

Deisslingen, Germany

Alfred Selz