The invention relates to a high-frequency receiver circuit having a frequency- selective element with a controllable tuning frequency, which picks up a received high- frequency signal and accordingly filters out unwanted signal components in accordance with the tuning frequency, a mixer which picks up the filtered high-frequency signal as a first input signal, a voltage-controlled local oscillator which supplies to the mixer a local oscillator signal as a second input signal, for converting the filtered input signal to an intermediate frequency, and a control circuit which controls the output frequency of the local oscillator and the tuning frequency of the frequency-selective element.

In high-frequency receiver circuits, modulated, high-frequency oscillations that have been picked up by an antenna are amplified and mixed with a local oscillator signal which is generated in the receiver itself. The resulting intermediate-frequency signal is then further processed, for instance amplified, demodulated and made audible using a loudspeaker.

Usually, a bandpass filter is provided before or in the first input stage as frequency-selective element, in order to protect the actual receiver circuit from unwanted input signals.

The filtered input signal is amplified and converted to an intermediate frequency with the aid of a mixer. For this purpose, the mixer receives, as a second input signal, a local oscillator signal which is typically generated using a control circuit and a voltage-controlled oscillator (VCO). Further filtering may then take place at intermediate frequency level where appropriate.

The intermediate frequency is in this case fixed so that, in order to receive signals having a different frequency, the output frequency of the voltage-controlled oscillator and hence the tuning voltage thereof must be changed.

Depending on the degree of preselection required by the bandpass filter that is connected upstream, it may be necessary also to change the tuning frequency of the bandpass filter in order to leave the reception properties at the desired signal frequency unchanged. The bandpass filter for this purpose also contains variable, voltage-controlled capacitors besides

fixed inductors and capacitors. Such voltage-controlled capacitors may for example be formed by so-called varactor diodes, pn diodes operated in the high-resistance direction.

The control circuit in this case changes, by means of its tuning voltage, besides the output frequency of the voltage-controlled oscillator, also the tuning frequency of the bandpass filter, so that the transmission curve of the filter is set precisely to the desired frequency. This procedure is referred to as in-line preselection.

However, it should be noted that, on account of the conventionally separate construction of the bandpass filter from individual components, there is no direct correlation between the setting of the voltage-controlled oscillator and the setting of the bandpass filter, so that a conversion element is required which makes the frequency setting curves of the oscillator and of the bandpass filter correspond. However, such a conversion element is often very expensive and may even require digital control. This also applies in particular for compensation in terms of manufacturing technology.

It is therefore an object of the invention to provide a high-frequency receiver circuit of the type mentioned in the introduction, in which control of the output frequency of the local oscillator and of the tuning frequency of the frequency-selective element is simplified. In particular, the circuit is also intended to be simple and cost-effective to produce.

This object is achieved by the high-frequency receiver circuit having the features defined in claim 1.

Accordingly, the invention comprises that in a generic high-frequency receiver circuit the frequency-selective element and the voltage-controlled local oscillator are made from components of the same component class or from component classes matched to one another.

Advantageous embodiments and further developments of the invention are characterized in dependent claims 2 to 8.

According to the advantageous embodiment of claim 2, the components of the frequency-selective element and of the voltage-controlled local oscillator are produced by the same manufacturing process. In particular it is advantageously provided that the components are produced in the same production run.

According to the preferred embodiment of the invention as claimed in claim 3, the frequency-selective element and the voltage-controlled local oscillator are in each case formed on an integrated module.

As claimed in claim 4, it may alternatively be advantageously provided that the frequency-selective element and the voltage-controlled local oscillator are formed on the same integrated module.

According to the measure of claim 5, the components of the frequency- selective element and of the voltage-controlled local oscillator advantageously have the same component characteristics and/or component tolerances.

Preferably, as claimed in claim 6, the high-frequency receiver circuit is designed and set up such that the components of the frequency-selective element and of the voltage-controlled local oscillator during operation are exposed to the same external influences, such as temperature, supply voltage and the like.

According to the preferred embodiment of claim 7, the control circuit controls both the output frequency of the local oscillator and the tuning frequency of the frequency- selective element by outputting a tuning voltage without the intermediate connection of a conversion element.

The advantageous measure of claim 8 provides an amplifier circuit, which picks up the filtered input signal, amplifies it, and supplies it to the mixer as an amplified, filtered high-frequency signal.

By means of the measures described, the following may be achieved - there is automatic compensation, so that the tuning voltage of the control circuit, besides the local oscillator, also sets the frequency-selective element to the correct tuning frequency without external intervention; - a separate conversion circuit is not required; and - the frequency-selective element automatically follows at a spacing from the intermediate frequency, even when the input frequency is changed.

The invention will be further described with reference to examples of embodiments shown in the drawings to which, however, the invention is not restricted.

The sole Figure shows a schematic block diagram of a high-frequency receiver circuit according to one example of embodiment of the invention.

The Figure shows a high-frequency receiver circuit 100 having an antenna 10 which picks up the high-frequency signal and supplies it to the bandpass filter 12. The

filtered high-frequency signal 14 is passed to an amplifier 16 and from there output to the mixer 20 as a filtered and amplified high-frequency signal 18.

In addition, the mixer 20 receives, from the voltage-controlled oscillator 22, a local oscillator signal as a second input signal 24 and uses the latter to convert the received high-frequency signal into an intermediate-frequency signal 26.

The output frequency of the local oscillator 22 and the tuning frequency of the bandpass filter 12 are controlled by the control circuit 28, which for this purpose outputs a tuning voltage 30 which is supplied both to the local oscillator 22 (at reference 32) and to the bandpass filter 12 (at reference 34).

In the example of embodiment, the bandpass filter 12, as a selectivity element installed in the amplifier 14, is integrated on a single IC together with the voltage-controlled oscillator 22. The bandpass filter 12 and the frequency-determining components of the voltage-controlled oscillator 12, namely its fixed and variable capacitors and inductors, are in this case made from the same class of components or from classes of components which are matched to one another and are exposed to the same tolerances or other influences, such as temperature, supply voltage and the like, these being determined by the manufacturing process.

By means of this integration of bandpass filter 12 and VCO 22, a conversion element between the control circuit 28 and the oscillator 22 or the bandpass filter 12 is not necessary, unlike in the case of conventional designs. Rather, during a change in the input frequency, the bandpass filter 12 automatically follows at a spacing from the intermediate frequency.

The embodiment outlined above makes it possible for there to be a considerable simplification of the high-frequency receiver circuit and hence a significant reduction in costs. Moreover, in the design according to the invention, influences such as tolerances or temperature changes do not lead to offsets in the compensating frequencies, since the frequency-determining components are in each case exposed to the same influences.

While the invention has been illustrated and described with reference to preferred examples of embodiments, the person skilled in the art will understand that changes can be made to the design and details without departing from the concept and scope of the invention. Accordingly, the disclosure of the present invention is not intended to be limiting in nature. Instead, the disclosure of the present invention is intended to illustrate the scope of the invention which is shown in the claims which follow.

LIST OF REFERENCES 10 antenna 12 bandpass filter 14 filtered high-frequency signal 16 amplifier 18 amplified high-frequency signal 20 mixer 22 voltage-controlled oscillator 24 local oscillator signal 26 intermediate-frequency signal 28 control circuit 30,32, 34tuning voltage 100 high-frequency receiver circuit