Frequency converter and radio frequency tuner

1. A single conversion radio frequency tuner, comprising: a single conversion frequency converter including an image reject mixer and a local oscillator, the local oscillator comprising a variable frequency oscillator and a variable divider between the mixer and the variable frequency oscillator, the variable divider receiving from the variable frequency oscillator a variable frequency signal and supplying to the mixer a local oscillator signal whose frequency is equal to a frequency of the variable frequency signal divided by any selected one of a plurality of integers, each of which is greater than one.

2. The tuner as claimed in claim 1 , in which the variable divider comprises a plurality of divide-by-two stages having respective outputs and a multiplexer having inputs connected to the respective outputs of the divide-by-two stages.

3. The tuner as claimed in claim 2 , in which the variable frequency oscillator is tuneable over a frequency range which is at least one octave.

4. The tuner as claimed in claim 1 , in which the variable frequency oscillator comprises a part of a frequency synthesizer.

5. The tuner as claimed in claim 1 , comprising a non-frequency-selective signal path connecting the mixer to a signal source.

6. The tuner as claimed in claim 1 , comprising a signal input an automatic gain control circuit between the signal input and the mixer.

7. The tuner as claimed in claim 1 , comprising a signal input and a plurality of input stages between the signal input and the mixer.

8. The tuner as claimed in claim 1 , formed as a single chip integrated circuit.

9. The tuner as claimed in claim 1 , formed as a digital tuner.

10. The tuner as claimed in claim 1 , formed as a cable tuner.