Automatic tuning circuit arrangement with switched impedances
First Claim
1. A tuning circuit arrangement for a receiving loop antenna of a receiver having a tuning system comprising:
- first and second input signal terminals to which said loop antenna is coupled and an output signal terminal for coupling said tuning circuit arrangement to said tuning system;
resonance circuit means coupled to said first and second input signal terminals for tuning said loop antenna over a range of frequencies responsive to a first control potential, which first control potential is of first polarity at selected times and which is of second polarity opposite to the first polarity at times other than said selected times, includingvariable capacitance means for developing a variable capacitance responsive to said first control potential at said selected times when said first control potential is of said first polarity, and for developing a low impedance compared to that of its variable capacitance at said times when said first control potential is of said second polarity, said variable capacitance means being coupled in circuit with said first and second input signal terminals,at least one other impedance means for exhibiting an impedance, andswitch means for coupling said other impedance means to said resonance circuit means at least at selected times; and
amplifying means having an input connection to which said resonance circuit means is coupled, and having an output connection coupled to said output signal terminal.
2 Assignments
0 Petitions
Accused Products
Abstract
Tuning circuitry for a VHF television (TV) antenna tunes such antenna for signals corresponding to the TV channel selected and couples those signals to the tuning system of a television receiver. An antenna has a pair of signal terminals across which the tuning circuitry connects to form a resonance circuit therewith for tuning the antenna. A variable capacitance responds to a control voltage to develop the appropriate value of tuning capacitance. Impedances, e.g. inductors or capacitors or resistors, are coupled to the resonance circuit at least at selected times by switches. An amplifier couples signals from the resonance circuit to the tuning system of the TV receiver.
49 Citations
25 Claims
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1. A tuning circuit arrangement for a receiving loop antenna of a receiver having a tuning system comprising:
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first and second input signal terminals to which said loop antenna is coupled and an output signal terminal for coupling said tuning circuit arrangement to said tuning system; resonance circuit means coupled to said first and second input signal terminals for tuning said loop antenna over a range of frequencies responsive to a first control potential, which first control potential is of first polarity at selected times and which is of second polarity opposite to the first polarity at times other than said selected times, including variable capacitance means for developing a variable capacitance responsive to said first control potential at said selected times when said first control potential is of said first polarity, and for developing a low impedance compared to that of its variable capacitance at said times when said first control potential is of said second polarity, said variable capacitance means being coupled in circuit with said first and second input signal terminals, at least one other impedance means for exhibiting an impedance, and switch means for coupling said other impedance means to said resonance circuit means at least at selected times; and amplifying means having an input connection to which said resonance circuit means is coupled, and having an output connection coupled to said output signal terminal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A tuning circuit arrangement for a receiving loop antenna of a receiver having a tuning system comprising:
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first and second input signal terminals to which said loop antenna is coupled and an output signal terminal for coupling said tuning circuit arrangement to said tuning system; resonance circuit means coupled to said first and second input signal terminals for tuning said loop antenna over a range of frequencies responsive to a first control potential including variable capacitance means for developing a variable capacitance responsive to said first control potential when said first control potential is of first polarity, and for developing a low impedance compared to that of its variable capacitance when said first control potential is of second polarity opposite to the first, said variable capacitance means being coupled in circuit with said first and second input signal terminals, at least one other impedance means for exhibiting an impedance, impedance transformation means having first and second output circuits for exhibiting first and second transformation ratios, respectively, with respect to an input circuit thereof, and switch means for coupling said other impedance means to said first and second output circuits at least at selected times responsive to a second control potential; and amplifying means having an input connection to which said resonance circuit means is coupled, and having an output connection coupled to said output signal terminal. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A tuning circuit arrangement for a VHF frequency-band loop antenna of a television receiver having a tuning system comprising:
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a loop antenna having first and second signal terminals; amplifying means having an input connection, and having an output connection for coupling to said tuning system; variable capacitance means for developing a variable capacitance responsive to a first control potential when said first control potential is of first polarity, and for developing a low impedance compared to that of its variable capacitance when said first control potential is of second polarity opposite to the first, said variable capacitance means being coupled between said first signal terminal and the input connection of said amplifying means; an inductance; first switch means for selectively coupling said inductance between said first and second signal terminals responsive to said tuning system; a capacitance; and second switch means for selectively coupling said capacitance between the input connection of said amplifying means and said second signal terminal responsive to said tuning system. - View Dependent Claims (18, 19, 20)
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21. A tuning circuit arrangement for a VHF frequency band loop antenna of a television receiver having a tuning system comprising:
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a loop antenna having first and second signal terminals; amplifying means having an input connection, and having an output connection for coupling to said tuning system; a transformer having first, second and third windings; variable capacitance means for developing a variable capacitance responsive to a first control potential when said first control potential is of first polarity, and for developing a low impedance compared to that of its variable capacitance when said first control potential is of second polarity opposite to the first, said variable capacitance means being coupled serially with said first winding between said first and second signal terminals; first diode means for coupling said second winding to the input connection of said amplifying means, which first diode means is poled for conduction in a first direction sense with respect to said input connection; second diode means for coupling said third winding to the input connection of said amplifying means, which second diode means is poled in a second direction sense opposite to the first; and means for applying a second control potential to said input connection, which second control potential is of first and second respective values at selected times for rendering a respective one of said first and second diode means conductive, and the other one thereof nonconductive, respectively. - View Dependent Claims (22, 23, 24, 25)
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Specification