Automatic frequency control system or an SSB receiver

Claim 2

An automatic frequency control system for a single sideband radio receiver having a local oscillator, mixer, and IF bandpass and receiving a signal containing, inter alia, squelch activation information transmitted by a transmitter comprising: first means for varying the local oscillator frequency of the radio receiver at a first given rate; means, responsive to the local oscillator frequency, for acquiring the transmitted signal and indicating a direction in which said local oscillator frequency should be varied to essentially center the transmitted signal in the radio receiver IF bandpass; means, coupled to said means for acquiring, for detecting the squelch activation information; second means, coupled to said means for acquiring, for varying said local oscillator frequency of the radio receiver at a second given rate in said indicated direction; and means, coupled to said squelch activation information detection means, for ceasing variation of said local oscillator frequency by said first and second varying means and maintaining said frequency essentially constant.

Claim 3

An automatic frequency control system in accordance with claim 1 wherein said means for detecting the squelch activation information further comprises means for commencing detection of squelch activation information before the transmitted signal is centered.

Claim 4

An automatic frequency control system in accordance with claim 2 wherein said means for commencing detection of squelch activation information further comprises means for cancelling said second given rate local oscillator variation therein.

Claim 5

An automatic frequency control system in accordance with claim 1 wherein said means for acquiring the transmitted signal further comprises means for providing a beat note output when the transmitted signal is acquired.

Claim 6

An automatic frequency control system in accordance with claim 4 wherein said means for acquiring the transmitted signal further comprises means for full wave rectification of said beat-note output.

Claim 7

An automatic frequency control system in accordance with claim 5 wherein said means for acquiring the transmitted signal further comprises means for generating a unitary output when said beat-note rectification reaches a predetermined level thereby activating said means for detecting the squelch activation information.

Claim 8

An automatic frequency control system in accordance with claim 6 wherein said means for acquiring the transmitted signal further comprises means for maintaining said unitary output for a predetermined period of time after said beat-note rectification falls below said predetermined level thereby providing hysteresis in said unitary output.

Claim 9

An automatic frequency control system in accordance with claim 7 wherein said means for maintaining said unitary output further comprises means, sensitive to impulse noise received with the transmitted signal, for modifying said predetermined unitary output maintainance time.

Claim 10

An automatic frequency control circuit for a single sideband radio receiver having a local oscillator, mixer, and IF bandpass and which receives a signal transmitted by a transmitter and detects squelch information in the transmitted signal comprising: means for varying the local oscillator frequency of the radio receiver; means, responsive to the local oscillator frequency, for acquiring the transmitted signal and indicating a direction in which the local oscillator frequency should be varied to essentially center the transmitted signal in the radio receiver IF bandpass; means, coupled to said means for acquiring, for commencing detection of squelch information from the transmitted signal when the signal is acquired and for removing said local oscillator frequency variation from the squelch information; and means for deactivating said local oscillator frequency varying means in response to said squelch detection.

Claim 11

An automatic frequency control circuit for a single sideband radio receiver having a local oscillator, mixer, and IF bandpass and which receives a signal transmitted by a transmitter and detects squelch information in the transmitted signal comprising: means for varying the local oscillator frequency of the radio receiver; means, responsive to the local oscillator frequency, for acquiring the transmitted signal and indicating a direction in which the local oscillator frequency should be varied to essentially center the transmitted signal in the radio receiver IF bandpass; means, coupled to said means for acquiring, for commencing detection of squelch information from the transmitted signal when the signal is acquired and for removing said local oscillator frequency variation from the squelch information; and means for deactivating said local oscillator frequency varying means in response to said squelch detection.

Claim 12

An automatic frequency control circuit in accordance with claim 9 wherein said means for acquiring the transmitted signal further comprises means for providing a beat note output when the signal is acquired.

Claim 13

An automatic frequency control circuit in accordance with claim 10 wherein said means for acquiring the transmitted signal further comprises means for full-wave rectification of said beat-note output.

Claim 14

An automatic frequency control circuit in accordance with claim 11 wherein said means for acquiring the transmitted signal further comprises means for generating a unitary output when said beat-note rectification reaches a predetermined value and maintaining said unitary output for a predetermined period of time after said beat-note rectification falls below said predetermined value.

Claim 15

An automatic frequency control circuit in accordance with claim 12 wherein said means for acquiring the transmitted signal further comprises means, sensitive to impulse noise received with the transmitted signal, for modifying said unitary output maintainance time.

Claim 16

An automatic frequency control circuit for a single sideband radio receiver in which a local oscillator is varied in frequency to acquire a transmitted signal containing, inter alia, squelch activation information, the automatic frequency control circuit comprising: means for varying the local oscillator frequency of the radio receiver at a first given rate; means, responsive to the local oscillator frequency, for determining the acquisition of the transmitted signal and providing a beat-note output when the signal is acquired; means for full-wave rectification of said beat-note output; means for providing a unitary output when said beat-note rectification reaches a predetermined value; means, responsive to said unitary output, for varying the local oscillator frequency at a second given rate; and means for maintaining said unitary output for a predetermined period of time after said beat-note rectification falls below said predetermined value thereby providing hysteresis in said unitary output.

Claim 17

An automatic frequency control circuit for a single sideband radio receiver in which a local oscillator is varied in frequency to acquire a transmitted signal containing, inter alia, squelch activation information, the automatic frequency control circuit comprising: means for varying the local oscillator frequency of the radio receiver at a first given rate; means, responsive to the local oscillator frequency, for determining the acquisition of the transmitted signal and providing a beat-note output when the signal is acquired; means for full-wave rectification of said beat-note output; means for providing a unitary output when said beat-note rectification reaches a predetermined value; means, responsive to said unitary output, for varying the local oscillator frequency at a second given rate; and means for maintaining said unitary output for a predetermined period of time after said beat-note rectification falls below said predetermined value thereby providing hysteresis in said unitary output.

Claim 18

An automatic frequency control circuit in accordance with claim 14 wherein said automatic frequency control circuit further comprises means for commencing detection of squelch activation information from the transmitted signal when the signal is acquired.

Claim 19

An automatic frequency control circuit in accordance with claim 14 wherein said automatic frequency control circuit further comprises means, sensitive to impulse noise received with the transmitted signal, for modifying said predetermined period of unitary output maintainance time.

Claim 20

An automatic frequency control circuit for a single sideband radio receiver having a local oscillator, mixer, and IF bandpass and receiving a signal transmitted by a transmitter, comprising: first means for varying the local oscillator frequency of the radio receiver at a first given rate; means, responsive to the local oscillator frequency, for acquiring the transmitted signal and providing a beat-note output in response thereto; means for full-wave rectification of said beat-note output; means for providing a unitary output when said beat-note rectification reaches a predetermined value; means responsive to said unitary output for ceasing said first local oscillator variation at a first rate, and for indicating a direction the local ocsillator frequency should be varied to essentially center the transmitted signal in the radio receiver IF bandpass; second means, responsive to said unitary output and indicated direction, for varying said local oscillator frequency of the radio receiver at a second given rate in said indicated direction; means, coupled to said means for acquiring, for commencing detection of squelch information from the transmitted signal before the signal is centered; and means for deactivating said second varying means in response to said squelch detection.

Claim 21

An automatic frequency control circuit for a single sideband radio receiver having a local oscillator, mixer, and IF bandpass and receiving a signal transmitted by a transmitter, comprising: first means for varying the local oscillator frequency of the radio receiver at a first given rate; means, responsive to the local oscillator frequency, for acquiring the transmitted signal and providing a beat-note output in response thereto; means for full-wave rectification of said beat-note output; means for providing a unitary output when said beat-note rectification reaches a predetermined value; means responsive to said unitary output for ceasing said first local oscillator variation at a first rate, and for indicating a direction the local ocsillator frequency should be varied to essentially center the transmitted signal in the radio receiver IF bandpass; second means, responsive to said unitary output and indicated direction, for varying said local oscillator frequency of the radio receiver at a second given rate in said indicated direction; means, coupled to said means for acquiring, for commencing detection of squelch information from the transmitted signal before the signal is centered; and means for deactivating said second varying means in response to said squelch detection.

Claim 22

An automatic frequency control circuit in accordance with claim 17 wherein said frequency control circuit further comprises means for maintaining unitary output for a predetermined period of time after said beat-note rectification falls below said predetermined value.

Claim 23

An automatic frequency control circuit in accordance with claim 18 wherein said automatic frequency control circuit further comprises means, sensitive to impulse noise received with the transmitted signal, for modifying said predetermined period of unitary maintainance time.

Claim 26

A method for controlling frequency in accordance with the method of claim 20 further comprising the step of commencing detection of squelch activation information before the transmitted signal is centered.

Claim 27

A method of controlling frequency in accordance with the method of claim 20 wherein the step of acquiring the transmitted signal further comprises the steps of providing a beat-note, rectifying said beat-note, and generating a unitary output when said beat-note rectification reaches a predetermined value.

Claim 28

A method of controlling frequency in accordance with the method of claim 22 wherein the step of acquiring the transmitted signal further comprises the step of maintaining said unitary output for a predetermined period of time.

Claim 29

A method of controlling frequency in accordance with claim 23 wherein the step of acquiring the transmitted signal further comprises the step of modifying said predetermined unitary output maintainance time in response to impulse noise received with the transmitted signal.