US 4,061,981 A · Voltage variable capacitor tuned radio receiver having delayed automatic frequency control at turn-on

Abstract

A voltage variable capacitor tuned radio receiver having a circuit which delays operation of a portion of the radio receiver circuit which includes the automatic frequency control circuit after the radio receiver is first energized until the filter capacitor at the output of the tuning voltage generator has charged to a selected tuning voltage to prevent the automatic frequency control circuit from locking the radio receiver onto an undesired RF carrier frequency.

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Drawings

Claims3

Dependent claims

A radio frequency receiver comprising:

at least one tunable stage whose tuned frequency determines the receiver response to an incoming RF carrier signal, the tunable stage including a voltage variable capacitor and having a tuned frequency determined by the value of a bias voltage across the voltage variable capacitor;
means effective upon energization of the receiver to supply a bias voltage across the voltage variable capacitor, the bias voltage increasing to a selected bias voltage value corresponding to a selected tuned frequency after a time delay determined by circuit parameters following initial energization of the radio receiver, the selected bias voltage value providing receiver response to a selected incoming RF carrier signal, the tuned frequency varying toward the selected tuned frequency as the bias voltage value increases to the selected bias voltage value;
a frequency control circuit effective to vary the bias voltage in amount and sense tending to adjust the tuned frequency to obtain a maximum receiver response condition to an incoming RF carrier signal, the frequency control circuit tending to effect adjustment of the tuned frequency to obtain a maximum receiver response condition to an incoming RF carrier signal different from the selected RF carrier signal when the tuned frequency of the tunable stage corresponds to said different incoming RF signal while the bias voltage value increases to the selected bias voltage value;
and a delay circuit effective upon energization of the receiver to inhibit operation of the frequency control circuit for a time at least equal to the time delay required for the tuning voltage to attain the selected tuning voltage value after the receiver is first energized, the frequency control circuit being rendered inoperative by the delay circuit to adjust the tuned frequency of the tunable stage to obtain maximum receiver response to an incoming RF carrier signal different from a selected RF carrier signal.

1 more element

A radio frequency receiver comprising:

at least one tunable stage whose tuned frequency determines the receiver response to an incoming RF carrier signal, the tunable stage including a voltage variable capacitor and having a tuned frequency determined by the value of a bias voltage across the voltage variable capacitor;
a filter capacitor;
means effective upon energization of the receiver to supply a bias voltage across the filter capacitor and the voltage variable capacitor, the filter capacitor charging to a selected bias voltage value corresponding to a selected tuned frequency after a time delay determined by circuit parameters following energization of the radio receiver and being effective to filter noise signals from the bias voltage, the selected bias voltage value providing receiver response to a selected incoming RF carrier signal, the tuned frequency varying toward the selected tuned frequency as the filter capacitor charges to the selected bias voltage value;
a frequency control circuit effective to vary the bias voltage in amount and sense tending to adjust the tuned frequency to obtain a maximum receiver response condition to an incoming RF carrier signal, the frequency control circuit tending to effect adjustment of the tuned frequency to obtain a maximum receiver response condition to an incoming RF carrier signal different from the selected RF carrier signal when the tuned frequency of the tunable stage corresponds to said different incoming RF signal while the filter capacitor charges to the selected bias voltage value;
and a delay circuit effective upon energization of the receiver to inhibit operation of the frequency control circuit for a time at least equal to the filter capacitor charging time delay, the frequency control circuit being rendered inoperative by the delay circuit to adjust the tuned frequency of the tunable stage to obtain maximum receiver response to an incoming RF carrier signal different from a selected RF carrier signal.

2 more elements

A radio frequency receiver comprising:

at least one tunable stage whose tuned frequency determines the receiver response to an incoming RF carrier signal, the tunable stage including a voltage variable capacitor and having a tuned frequency determined by the value of a bias voltage across the voltage variable capacitor;
a filter capacitor;
means effective upon energization of the receiver to supply a bias voltage across the filter capacitor and the voltage variable capacitor, the filter capacitor charging to a selected bias voltage value corresponding to a selected tuned frequency after a first time delay determined by circuit parameters following energization of the radio receiver and being selective to filter noise signals from the bias voltage value, the selected bias voltage value providing receiver response to a selected incoming RF carrier signal, the tuned frequency varying toward the selected tuned frequency as the filter capacitor charges to the bias voltage value;
a frequency control circuit effective when energized by a predetermined voltage value to vary the bias voltage in amount and sense tending to adjust the tuned frequency to obtain a maximum receiver response condition to an incoming RF carrier signal, the frequency control circuit tending to effect adjustment of the tuned frequency to obtain a maximum receiver response condition to an incoming RF carrier signal different from the selected RF carrier signal when the tuned frequency of the tunable stage corresponds to said different incoming RF signal while the filter capacitor charges to the bias voltage;
means effective to energize the radio receiver, said means including a voltage source and a manually operable switch means series coupled therewith, the switch means being operable to energize the radio frequency receiver;
a time delay circuit parallel coupled across the series coupled voltage source and switch means, the time delay circuit including a time delay capacitor and a resistor, the time delay capacitor being charged by the voltage source through the resistor upon operation of the switch means;
means effective to couple the voltage charge across the time delay capacitor to the frequency control circuit to effect energization thereof when said voltage charge attains the predetermined voltage value, the time delay capacitor and resistor defining a time constant so that the voltage charge attains the predetermined voltage value a second time delay after operation of the switch means, the second time delay being at least equal to the first time delay, the frequency control circuit being rendered inoperative by the time delay circuit to adjust the tuned frequency of the tunable stage to obtain maximum receiver response to an incoming RF carrier signal different from a selected RF carrier signal.

4 more elements

Dependencies are inferred from the claim text.

Description2,454 words

Summary2,454 words

#This invention relates to a radio receiver having voltage variable capacitor tuned circuits and an automatic frequency control circuit.

#Voltage tuned radio receivers are generally known where the radio is tuned to a desired RF carrier frequency by applying a selected tuning voltage to voltage variable capacitors in the tunable circuits of the receiver. To prevent noise signals from effecting the tuned frequencies of the tunable circuits, the tuning voltage is applied across a large filtering capacitor. When the voltage tuned radio receivers are first energized, a delay is experienced before the radio is tuned to a selected RF carrier frequency associated with a selected tuning voltage as a result of the time constant associated with the charging of the filter capacitor. This time constant is determined by the capacitance of the filter capacitor and the output impedance of the tuning voltage generator.

#When these voltage variable capacitor tuned circuits are used in conjunction with an automatic frequency control circuit, the automatic frequency control circuit may cause the radio receiver to temporarily or permanently lock onto an RF carrier frequency different from the RF carrier frequency associated with a selected tuning voltage if the automatic frequency control circuit is operable while the filter capacitor is being charged by the selected generated tuning voltage after the radio receiver is first energized. The receiver may be particularly susceptible to locking onto an undesired RF carrier signal after the receiver is first energized when a high strength RF carrier signal exists at a frequency just adjacent to the RF carrier frequency associated with a selected tuning voltage and through which the tuned frequency of the tunable circuits sweep as the filter capacitor is charged. As the tuned frequency of the tunable circuits sweeps to the selected frequency while the filter capacitor is being charged by the generated tuning voltage, the automatic frequency control circuit may operate to adjust the output of the tuning voltage generator so as to lock the tunable circuits onto the undesired RF carrier signal.

Facts

Application

05/715,394Filed 18 Aug 1976

Granted

6 Dec 1977

Term ended

6 Dec 1994

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification4 codes

H03J 7/023
Automatic frequency control: neutralization of the automatic frequency correction during a tuning change
H04B 1/26
Circuits: for superheterodyne receivers
H03J
Tuning resonant circuits
H04B
Transmission

Voltage variable capacitor tuned radio receiver having delayed automatic frequency control at turn-on

Life of this patent

Voltage variable capacitor tuned radio receiver having delayed automatic frequency control at turn-on

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims3

Description2,454 words

Drawings

Classification4 codes

Life of this patent

Description2,454 words