Electronic tracking for tuners

Claim 2

In a multiband tuning system for providing an IF signal from RF signals residing in a signal band, apparatus comprising filter means for selecting RF signals corresponding to a selected channel in said band in response to a filter tuning control signal having a first variation range; mixing means responsive to said selected RF signals and a local oscillator signal for frequency translating said selected RF signals to develop said IF signal; oscillator means for generating said local oscillator signal in response to an oscillator tuning control signal having a second variation range for said band, said second range of variation being substantially less than said first range; and DC signal translating means including an amplifier having an input responsive to said oscillator tuning control signal and having at least first and second predetermined gain transfer characteristics for modifying said oscillator tuning control signal and for providing at an output said filter tuning control signal, and including switch means for changing the gain transfer characteristic of said amplifier from said first to said second transfer characteristic in response to one of said tuning control signals so as to derive a piecewise-linear approximation of the other of said tuning control signals.

Claim 3

The tuning system of claim 1 wherein said switch means includes a voltage establishing circuit for developing a first bias voltage and a threshold conduction device responsive to one of said oscillator and filter tuning control signals and to said first bias voltage for changing the gain of said amplifier at a predetermined level of said one tuning control signal so as to provide a break point between said first and second gain transfer characteristics.

Claim 4

The tuning system of claim 2, wherein said voltage establishing circuit develops a second bias voltage and applies said second bias voltage to said amplifier for establishing a predetermined DC offset between said oscillator and filter tuning control signals.

Claim 5

The tuning system of claim 3 wherein said amplifier comprises an operational amplifier having said oscillator tuning control signal coupled to its non-inverting input and said threshold conduction device coupled to its inverting input, said voltage establishing circuit providing said second bias voltage to said inverting input so as to establish said predetermined DC offset between said oscillator and said filter tuning control signals.

Claim 6

The tuning system of claim 4 wherein said voltage establishing circuit provides said first bias voltage to said threshold conduction device for establishing its conduction threshold point.

Claim 7

The tuning system of claim 4 wherein the output of said operational amplifier is coupled to said threshold conduction device for controlling its conduction threshold point.

Claim 8

The tuning system of claim 1 wherein said signal band comprises a first broadcast band, a first cable band, a second broadcast band and a second cable band.

Claim 9

In a multiband tuning system for producing an IF signal from RF signals corresponding to respective channels which may be selected residing in, in the order named, a first broadcast band, a first cable band, a second broadcast band, and a second cable band, apparatus comprising: a single local oscillator means for generating, without the use of switched reactive components, said local oscillator signal and controlling its frequency in a frequency range sufficient to develop said IF signal for any selected channel in any of said above named bands in response to an oscillator tuning control signal; control means for generating said oscillator tuning control signal in accordance with said selected channel; filter means for selecting the RF signal corresponding to a selected channel in response to a filter control signal; mixing means responsive to said selected RF signal and said local oscillator signal for frequency translating said selected RF signal to develop said IF signal; and DC signal translating means including amplifier means having an input responsive to said oscillator tuning control signal and having at least first and second predetermined gain transfer characteristics for modifying said oscillator tuning signal for providing at an output said filter tuning control signal and including switch means coupled to said amplifier means for changing the gain transfer characteristic of said amplifier means from said first to said second transfer characteristic in response to one of said oscillator and filter tuning control signals.

Claim 10

In a multiband tuning system for producing an IF signal from RF signals corresponding to respective channels which may be selected residing in, in the order named, a first broadcast band, a first cable band, a second broadcast band, and a second cable band, apparatus comprising: a single local oscillator means for generating, without the use of switched reactive components, said local oscillator signal and controlling its frequency in a frequency range sufficient to develop said IF signal for any selected channel in any of said above named bands in response to an oscillator tuning control signal; control means for generating said oscillator tuning control signal in accordance with said selected channel; filter means for selecting the RF signal corresponding to a selected channel in response to a filter control signal; mixing means responsive to said selected RF signal and said local oscillator signal for frequency translating said selected RF signal to develop said IF signal; and DC signal translating means including amplifier means having an input responsive to said oscillator tuning control signal and having at least first and second predetermined gain transfer characteristics for modifying said oscillator tuning signal for providing at an output said filter tuning control signal and including switch means coupled to said amplifier means for changing the gain transfer characteristic of said amplifier means from said first to said second transfer characteristic in response to one of said oscillator and filter tuning control signals.

Claim 11

The tuning system of claim 8 wherein said switch means includes a voltage establishing circuit for developing a first bias voltage and threshold conduction device responsive to one of said oscillator and filter tuning control signals and to said first bias voltage for changing the gain of said amplifier means at a predetermined level of said one tuning control signal so as to provide a break point between said first and second gain transfer characteristic.

Claim 12

The tuning system of claim 9 wherein said voltage establishing circuit develops a second bias voltage and applies said second bias voltage to said amplifier means for establishing a predetermined DC offset between said oscillator and filter tuning control signals.

Claim 13

The tuning system of claim 10 wherein said amplifier means comprises an operational amplifier having said oscillator tuning control signal coupled to its non-inverting input and said threshold conduction device coupled to its inverting input , said voltage establishing circuit providing said second bias voltage to said inverting input so as to establish said predetermined DC offset between said oscillator and said filter tuning control signals.

Claim 14

The tuning system of claim 11 wherein said voltage establishing circuit provides said first bias voltage to said threshold conduction device for establishing its conduction threshold point.

Claim 15

The tuning system of claim 11 wherein the output of said operational amplifier is coupled to said threshold conduction device for controlling its conduction threshold point.