A satellite tuner stage

Claim 2

A tuner stage according to claim 1, characterised in that it further comprises: a second summer for summing said sixth signal and the inverse signal of said seventh signal; and a means for controlling said first and second summers such that only one of said summers provides summed signals.

Claim 3

A tuner stage according to claims 1 or 2, characterised in that it further comprises: a first amplifier (12) for amplifying said first signals (S1); a second amplifier (14) for amplifying said fourth signal (S6); and a third amplifier (16) for amplifying said fifth signal (S7).

Claim 4

A tuner stage according to claim 3, characterised in that it further comprises: a first low pass filter placed between said first mixer (18a) and said second amplifier (14); and a second low pass filter placed between said second mixer (18b) and said third amplifier (16).

Claim 5

A tuner stage according to any of the above claims, characterised in that: the means (22) for introducing a further phase shift between said fifth and sixth signals (S6, S7) comprises a means (22b) for introducing a phase-lag of substantially 45° into one of said fifth or sixth signals and a means (22c) for introducing a phase-lead of substantially 45° into the other of said fifth or sixth signals.

Claim 6

A tuner stage according to any of the above claims, characterised in that all of the signals, with the exception of said summed signals, are differential signals.

Claim 7

A tuner stage according to any of the above claims, characterised in that: said first amplifier (12) is a transconductance amplifier; and said second and third amplifiers (14, 16) are transimpedance amplifiers.

Claim 8

A tuner stage according to any of the above claims, characterised in that said oscillator (20) provides limited amplitude output signals (S4, S5) that each have a duty cycle of one.

Claim 9

A tuner stage according to any of the claims 5-8, characterised in that said means (22b) for introducing a phase-lag of substantially 45° and said means for introducing a phase-lead of substantially 45° are Hilbert filters.

Claim 10

A tuner stage according to any of the above claims, characterised in that said first filter is a surface acoustic wave filter.

Claim 11

A tuner stage according to any of the above claims, characterised in that it is implemented on a single semiconductor substrate, with the exception of said oscillator (20) and said first filter.

Claim 12

A tuner stage according to any of the above claims, characterised in that it is incorporated within a television set and/or a video recorder.

Claim 14

A method according to claim 13, characterised in that it further comprises the following steps: summing, with a second summer, said first signal and the inverse of said second signal; and controlling said first and second summers such that only one summer provides summed signals.

Claim 17

A tuner stage (10) for selecting a channel at a required carrier frequency from an incoming signal (S1) comprising a plurality of different carrier frequencies, the tuner stage comprising: a terminal for receiving said incoming signal (S1); first and second mixer circuits (18a,18b) connected to said terminal for mixing said incoming signal with respective mixer signals (S4,S5) which are at the same selected frequency and which have a phase shift of substantially 90° between them, for generating respective mixer output signals (S6,S7); a phase shift circuit (22) connected to receive said mixer output signals and arranged to introduce a phase shift of substantially 90° between them at an intermediate frequency that is equal to the difference between said selected frequency and said required carrier frequency, to generate first and second signals (S10,S11); a summing circuit (24) for summing said first and second signals to generate a combined signal (28); and a filter (26) with a centre frequency matching said intermediate frequency, for filtering said combined signal to select said channel.