Synchronizing system

• US 4,361,890 A
• Filed: 06/17/1958
• Issued: 11/30/1982
• Est. Priority Date: 06/17/1958
• Status: Expired due to Term

• Current Assignee: GTE Government Systems Corporation (General Dynamics Corporation)
• Original Assignee: GTE Products Corporation
• Inventors: Green, James H. Jr., Nicholson, Madison G. Jr.
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US03/744,034
• Time in Patent Office: 8,932 Days
• Field of Search: 250/6.6, 250/9 S, 250/20.41, 178/43.5, 178/22.17, 179/1.5, 179/15.5, 179/15.6, 179/15, 340/349, 340/351, 340/147 SY, 235/181, 235/121, 343/100.7, 343/100 CL, 325/32, 371/1, 371/111, 371/118, 371/119, 371/120, 371/106, 371/108, 371/25, 371/96, 364/728, 364/604, 364/819, 370/106, 370/108, 370/12, 367/41
• US Class Current: 375/142
• CPC Class Codes: H04B 1/69 Spread spectrum techniques

Abstract

1. In a communication system utilizing at least two independent binary coded pulse signal sequences, means for achieving and holding time synchronism between said two sequences which comprises the combination of pulse recurrence frequency searching means for controlling the pulse recurrence frequency of one of said signals relative to the other to bring said signal into synchronism with the other, and phase locking means including a periodic phase checking circuit and a phase variation correcting circuit responsive to the searching means bringing the signals into synchronism to operate on one of said signals for holding said signals in synchronism.

Claims

1. In a communication system utilizing at least two independent binary coded pulse signal sequences, means for achieving and holding time synchronism between said two sequences which comprises the combination of pulse recurrence frequency searching means for controlling the pulse recurrence frequency of one of said signals relative to the other to bring said signal into synchronism with the other, and phase locking means including a periodic phase checking circuit and a phase variation correcting circuit responsive to the searching means bringing the signals into synchronism to operate on one of said signals for holding said signals in synchronism.

2. In an electronic signal system, means for synchronizing a first sequence of binary coded signal pulses having a multiple frequency content with a second sequence of similarly coded pulses having a similar frequency content which comprises:

for the pulses of said first sequence, a pulse frequency content shifting circuit and a pulse phase shifting circuit;

a mixer circuit for comparing the frequency and phase components of the pulses of said first sequence with the pulses of said second sequence; and

, first and second control circuits responsive to said comparison for controlling the frequency content and phase respectively of the pulses of said first sequence said first control circuit including means independent of said signal sequences for changing the frequency content of said pulse shifting circuit in discrete increments and means for measuring the effect of said changes and said second control circuit including means independent of said signal sequences for periodically shifting the phase of said pulse shifting circuit and means for measuring the effect of said phase shifting.

3. In an electronic signal system utilizing at least two binary coded pulse sequences, means for achieving and holding correlated synchronism between said sequences which comprises the combination of:

means for comparing said sequences;

means for changing the pulse recurrence frequency of one of said sequences to search for correlation; and

, means responsive to said comparison for adjusting the phase of one of said sequences to maintain correlation.

4. The invention according to claim 3 and wherein said means for changing frequency includes a pulse recurrence frequency control circuit having a search and a basic mode of operation, each characterized by a different output frequency, and means responsive to said code sequence comparison for changing from one mode to another.

5. For a communication system, a self-synchronizing receiver which comprises:

means for providing a received binary coded pulse signal sequence;

a comparison circuit;

means for applying said received signal to said comparison circuit;

means for providing a local binary coded pulse signal having frequency and phase components;

means for applying said local signal to said comparison circuit;

means independent of said received signal for varying the frequency and the phase of said local pulse coded signal; and

, means responsive to the output of said comparison circuit for controlling the frequency and phase components of said local pulse code.

6. A radio communication system which comprises:

at a transmitter, means for producing an rf carrier signal, pulse code sequence modulating means for binary pulse code modulating said signal; and

, at a receiver, means for intercepting said carrier signal, means for providing a local rf signal, pulse code sequence providing means for binary pulse code modulating said local signal, means for comparing said intercepted and locally modulated signals in in a common mixer circuit, and frequency sensitive means for synchronizing the period of said coded intercepted and local signals, said frequency sensitive means including means for gradually changing the pulse recurrence frequency of said local pulse code signal sequence, means for detecting maximum correlation between the modulation frequency of said intercepted and locally generated signals and means for periodically shifting the relative phase of said received and locally generated signal sequences into and out of correlation and controlling the operation of said means for changing the pulse recurrence frequency of said local pulse code signal sequence by feed-back connection from said shifting means.

7. A communication system which comprises:

at a transmitting station, means for generating an rf signal, means for providing a sequence of pulses, means for modulating said rf signal with said pulse sequence, and means for transmitting said modulated signal; and

, at a receiving station, means for intercepting said modulated signal, means for generating a local rf signal, means including a periodic timing circuit for providing a local sequence of pulses, means for modulating said local rf signal with said local pulse sequence, a common mixer circuit connected to said intercepting and said local modulating means, an IF amplifying and detecting circuit connected to said mixer circuit, a pulse frequency control circuit for varying the frequency of said local pulse sequence, means responsive to the output of said IF detection circuit for controlling the operation of said frequency control circuit, a phase control circuit for shifting the phase of said local pulse sequence, means responsive to the output of said IF detection circuit for measuring the effect of said phase shifting, and means responsive to said measuring for adjusting the period of said timing circuit.

8. A carrier dispersal communication system which comprises:

at a transmitting station, means for generating an rf carrier signal, a first pulse shifting register with regenerative feed-back connections for providing a sequence of pulses, means for modulating said rf signal with said pulse sequence to disperse the energy of said carrier over a relatively broad rf spectrum, means for pulsing said modulated signal further to disperse said energy, and means for transmitting said modulated signal; and

, at a receiving station, means for intercepting said transmitted signal, means for generating a local rf signal, means including a periodic timing circuit and a second pulse shifting register with regenerative feed-back connections for providing a local sequence of pulses identical to the sequence at the transmitter, means for modulating said local rf signal with said local pulse sequence, means for pulsing said signal so modulated similarly to the pulsing of the modulated signal at the transmitter, a common mixer circuit, means for connecting said intercepted signal and modulated and pulsed local signal to said mixer circuit, an IF amplifying and detecting circuit connected to said mixer, a pulse frequency control circuit for varying the frequency of said local pulse sequence, means responsive to the output of said IF detection circuit for controlling the operation of said frequency control circuit, a phase control circuit for shifting the phase of said local pulse sequence, means responsive to the output of said IF detection circuit for measuring the effect of said phase shifting, and means responsive to said measuring for adjusting the phase of said local pulse sequence.

9. A carrier dispersal communication system which comprises:

at a transmitting station, means for generating an rf carrier signal, first means for modulating said carrier with message intelligence, means including a first pulse shifting register with regenerative feed-back connections for providing a sequence of pulses, second means for modulating said carrier with said pulse sequence to disperse the energy of said carrier over a relatively broad rf spectrum, means for pulsing said modulated signal further to disperse said energy, and means for transmitting said modulated signal; and

, at a receiving station, means for intercepting said modulated signal, means for generating a local rf signal, means including a periodic timing circuit and a second pulse shifting register with regenerative feed-back connections for providing a local sequence of pulses identical to the sequence at the transmitter, means for modulating said local rf signal with said local pulse sequence, means for pulsing said local signal so modulated similarly to the pulsing of the modulated signal at the transmitter, a mixer circuit, means connecting said intercepted signal and said modulated and pulsed local signal to said mixer circuit, an IF amplifying circuit connected to said mixer, a pulse frequency control circuit for varying the frequency of said local pulse sequence, means responsive to the output of said IF circuit for controlling the operation of said frequency control circuit, a phase control circuit for shifting the phase of said local pulse sequence, means responsive to the output of said IF detection circuit for measuring the effect of said phase shifting, means responsive to said measuring circuit for adjusting the phase of said local pulse sequence, and means connected to said IF amplifying circuit for detecting said message intelligence.

10. For a communication system employing a binary code pulsed carrier, a self-synchronizing receiver which comprises:

an rf energy reception circuit, a mixer circuit connected to said reception circuit;

an IF amplifying circuit connected to said mixer;

a local oscillator;

a local binary code pulse generator;

a modulator;

means connecting said local oscillator and pulse generator to said modulator;

means connecting the output of said modulator to said mixer;

a source of timing pulses for controlling the pulse recurrence frequency of the output of said pulse generator;

a frequency shifting circuit for effecting a change in the frequency of said pulses independently of the frequency content of said received energy;

an IF signal amplitude detector connected to said IF amplifier;

a frequency control circuit for controlling the operation of said frequency shifting circuit responsive to the output of said IF amplitude detector; and

, means responsive to the output signal of said IF amplifier for further adjusting the frequency of said modulating pulses.

11. For a communication system employing a binary code pulsed carrier, a self-synchronizing receiver which comprises:

an rf energy reception circuit;

a mixer circuit connected to said reception circuit;

an IF amplifying circuit connected to said mixer;

a local oscillator;

a local binary code pulse generator;

a modulator;

means connecting said local oscillator and pulse generator to said modulator;

means connecting the output of said modulator to said mixer;

a source of timing pulses for controlling the pulse recurrence frequency of the output of said pulse generator;

frequency shifting means responsive to the output of said IF amplifier for synchronizing said local pulse code with said received pulse code;

a phase shift circuit adapted to change periodically the phase timing of the output of said pulse generator;

a phase sensitive circuit for detecting the effect of said phase changes on the output of said IF amplifier; and

, a control circuit for adjusting the output of said timing pulse source responsive to signals from said phase sensitive circuit.

12. A dispersed carrier communication system which comprises:

a transmitter including an rf generator, a pulse generator including a pulse shifting register with regeneration feed-back connections, a message modulating circuit, a balanced modulator, means modulating the output of said rf generator with the output of said pulse generator in said balanced modulator to disperse said rf energy over a broad band of the frequency spectrum, and means for transmitting said energy so modulated and dispersed; and

, a receiver including an rf reception circuit to receive said transmitted energy, a mixer circuit connected to said rf reception circuit, a tuned IF amplifying circuit connected to the output of said mixer circuit, a local rf generator having an output signal frequency which is removed from the output frequency of the rf generator in said transmitter by the frequency to which said IF amplifying circuit is tuned, a local pulse generator including a pulse shifting register with regenerative feed-back connections for providing the same pulse sequence as that provided by the corresponding pulse generator in the transmitter, a balanced modulator, means connecting the output signals from said local rf and pulse code generators to said modulator whereby the rf energy of said local generator is dispersed in a pattern having substantially identical frequency and phase components with those of the transmitted signal, means connecting the output of said local balanced modulator to said mixer, a local source of timing pulses for controlling the signal frequency of said local code generator, a frequency shifting circuit for changing the frequency of the pulses from said timing source as applied to said code generator, an amplitude detector connected to said IF amplifier, a frequency control circuit for controlling the operation of said frequency shifting circuit responsive to the output of said IF amplitude detector, a phase shift circuit adapted to change periodically the phase timing of the output of said local pulse generator, a phase sensitive circuit for detecting the effect of said phase changes on the output of said IF amplifier, a control circuit for adjusting the output of said timing pulse source in response to signals from said phase sensitive circuit, and means for detecting the message modulation from the output of said IF amplifier.