AFT summing circuit for varactor-type tuning systems
First Claim
1. In a receiver having tuner means for selectively detecting and processing a transmitted signal, an AFT circuit for providing a correction signal, and channel selection means for providing a tuning signal whose amplitude is indicative of the channel to be tuned by said tuning means, an AFT summing circuit comprising:
- amplifier means having first and second inputs for receiving, respectively, the correction signal and the tuning signal, for providing a composite output signal, to be applied to said tuning means and having a tuning signal component and a correction component, said amplifier means including first means for providing a substantially predetermined gain to the tuning signal component, and second means for varying the correction signal component of the composite output signal.
0 Assignments
0 Petitions
Accused Products
Abstract
There is disclosed an AFT summing circuit for a varactor-type tuning system and in particular for such a tuning system including a UHF tuner and a VHF tuner. A tuning voltage derived from a suitable source indicative of the desired channel or station to be tuned is applied to one input of the AFT summing circuit, while an error signal as derived from an AFT circuit is applied to the other input, to be summed together in a manner whereby the effect of the AFT signal may be adjusted without affecting the tuning voltage. The AFT circuit output is applied at a first level when the VHF tuner is operative, and at a second attenuated level when the UHF tuner is operative. In particular, the AFT summing circuit includes first and second impedance elements for applying the AFT circuit output to first and second input terminals of an operational amplifier, and a third impedance element for applying the tuning voltage to the second input terminal. A fourth impedance element is connected in a feedback loop from the output of the operational amplifier to the first input terminal. The values of the first, second, third and fourth impedances Z1 , Z2, Z3 and Z4 are selected to satisfy the following equation in order that a substantially predetermined gain is provided to the tuning voltage, regardless of the adjustments made to the AFT circuit output: ##EQU1## Further, there is included means for applying a variable control or gain to the correction signal component of the output of the operational amplifier.
-
Citations
16 Claims
-
1. In a receiver having tuner means for selectively detecting and processing a transmitted signal, an AFT circuit for providing a correction signal, and channel selection means for providing a tuning signal whose amplitude is indicative of the channel to be tuned by said tuning means, an AFT summing circuit comprising:
amplifier means having first and second inputs for receiving, respectively, the correction signal and the tuning signal, for providing a composite output signal, to be applied to said tuning means and having a tuning signal component and a correction component, said amplifier means including first means for providing a substantially predetermined gain to the tuning signal component, and second means for varying the correction signal component of the composite output signal. - View Dependent Claims (2, 3, 4, 5)
-
6. In a television receiver having first and second tuner means for selectively detecting and processing transmitted signals within different frequency ranges, an AFT circuit for providing a correction signal for adjusting the tuning of said first and second tuner means, and channel selection means for providing a tuning signal whose amplitude is indicative of the channel to be tuned by one of said first and second tuner means, an AFT summing circuit comprising:
amplifier means having first and second inputs for receiving, respectively, the correction signal and the tuning signal, for providing a composite output signal having a tuning signal component and a correction signal component, said amplifier means including first means for providing a substantially predetermined gain to the tuning signal component and second means for varying the correction signal component of the composite output signal. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
-
15. In a television receiver having tuner means for selectively detecting and processing a transmitted signal, an AFT circuit for providing a correction signal, means for setting a channel to be tuned by said tuner means, variable divider means responsive to the output of said setting means for providing an output in accordance with a factor corresponding to the channel selected by said setting means, reference oscillator means for providing a reference frequency signal which may be adjusted, and means for comparing the output of said reference oscillator means with the output of said variable divider means for applying a tuning signal to said tuner means, an AFT summing circuit comprising:
amplifier means having first and second inputs for receiving, respectively, the correction signal and the tuning signal, for providing a composite output signal to said reference oscillator and having a tuning signal component and a correction component, said amplifier means including first means for providing a substantially predetermined gain to the tuning signal component, and second means for varying the correction signal component of the composite output signal. - View Dependent Claims (16)
Specification