SYNCHRONIZATION DEVICE FOR ANTI-JAMMING COMMUNICATIONS SYSTEM

• US 3,731,198 A
• Filed: 08/25/1966
• Issued: 05/01/1973
• Est. Priority Date: 08/25/1966
• Status: Expired due to Term

• Current Assignee: Herman L. Blasbalg
• Original Assignee: Herman L. Blasbalg
• Inventors: Blasbalg, Herman L.
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Birmiel, H. A.
• Application Number:
  US04/575,501
• Time in Patent Office: 2,441 Days
• Field of Search: 325/32,34,40,42,65 178/69.5 340/204,318,348 343/18E
• US Class Current: 375/367
• CPC Class Codes: H04K 3/25 based on characteristics of target signal or of transmission as countermeasure against surveillance H04K3/827, e.g. using direct sequence spread spectrum or fast frequency hopping spread spectrum techniques H04B1/69
• CPC Class Codes: H04L 7/043 Pseudo-noise [PN] codes variable during transmission synchronisation of spread spectrum receivers H04B1/69

Abstract

The invention is a synchronizing device for an anti-jam communications system producing at the transmitting station a synchronizing pulse formed by introducing a clock pulse into a matched filter pulse shaping network controlled by a shift register pseudo-noise sequence generator. At the receiving station a mirror image of the matched filter pulse shaping network is provided to decode the synchronizing pulse and eventually synchronize the clock at the receiving station.

Claims

1. In an anti-jam communications system, means for synchronizing the receiving station clock to the transmitting station clock comprising:

a first shift register PN sequence generator at said transmitting station for generating binary PN sequences under control of the transmitting station clock;

a signal shaping network responsive to selected stages of said first shift register PN sequence generator for producing output signals at predetermined intervals under control of the transmitting station clock, the shape of said output signals being controlled by the contents of said selected stages;

a first variable frequency oscillator responsive to selected stages of said first shift register PN sequence generator for producing an output signal, the frequency of which is controlled by the contents of said selected stages;

a modulator at said transmitting station for modulating the output signal from said first variable frequency oscillator with the output signal from said signal shaping network so as to form a transmission signal;

a second shift register PN sequence generator at said receiving station for generating PN sequences under control of the receiving station clock, said second shift register PN sequence generator being identical to said first PN sequence generator at said transmitting station;

a second variable frequency oscillator responsive to selected stages of said second shift register PN sequence generator for producing an output signal, the frequency of said output signal being controlled by the contents of said selected stages so as to correspond to the frequency of the output signal from said first variable frequency oscillator;

a demodulator at said receiving station for demodulating the transmission signal from said modulator under control of the signal from said second variable frequency oscillator so as to recover a signal corresponding to the signal produced by said signal generator at said transmitting station;

a signal decoding network controlled by selected stages of said second shift register PN sequence generator so as to respond exclusively to a demodulated signal of a particular shape to produce an output pulse for synchronizing the receiving station clock, said shape being determined by the contents of said selected stages.

2. In an anti-jam communications system, synchronizing means of the type described in claim 1 wherein the signal shaping network comprises:

a tapped delay line filter, each tap including a variable impedance device, the impedance of which is controlled by the contents of a selected stage of said first shift register PN sequence generator.

3. In an anti-jam communications system, synchronizing means of the type described in claim 1 wherein the first variable frequency oscillator comprises:

a digital-to-analog converter responsive to the contents of selected stages of said first shift register PN sequence generator; and

a voltage controlled oscillator responsive to the output from said digital-to-analog converter.

4. In an anti-jam communications system of the type wherein a shift register PN sequence generator is employed at the transmitting station for the purpose of encoding the data to be transmitted, and an identical shift register PN sequence generator is employed at the receiving station for the purpose of decoding the transmitted data, synchronizing means of the type described in claim 1 including:

means for transferring the contents of selected stages of said first shift register PN sequence generator to selected stages of the shift register PN sequence generator which is employed for the purpose of encoding the data to be transmitted.

5. In an anti-jam communications system, synchronizing means of the type described in claim 1 wherein the signal shaping network comprises:

a delay line for receiving pulses from said transmitting station clock;

a plurality of taps disposed along the length of said delay line for sensing the pulses transmitted along said delay line at successive intervals;

a variable impedance device connected to each tap, the impedance of each variable impedance device being controlled by the contents of a corresponding stage of said first shift register PN sequence generator; and

a summation device for summing the outputs from said variable impedance devices so as to form a signal, the shape of which is determined by the contents of the stages of said first shift register PN sequence generator.

6. In an anti-jam communications system, synchronizing means of the type described in claim 5 wherein each variable impedance device comprises a gate, the condition of which is controlled by the corresponding stage of said first shift register PN sequence generator.

7. In an anti-jam communications system, means for synchronizing the receiving station clock to the transmitting station clock comprising:

a first shift register PN sequence generator at said transmitting station for generating binary PN sequences under control of the transmitting station clock;

a signal shaping networK responsive to selected stages of said first shift register PN sequence generator for producing synchronizing signals at predetermined intervals under control of the transmitting station clock, the shapes of said output signals being controlled by the contents of said selected stages;

a second shift register PN sequence generator at said receiving station for generating PN sequences under control of the receiving station clock, said second shift register PN sequence generator being identical to said first PN sequence generator at said transmitting station;

a signal decoding network controlled by selected stages of said second shift register PN sequence generator so as to respond exclusively to synchronizing signals of particular shapes so as to produce an output pulse for synchronizing the receiving station clock said shapes being determined by the contents of said selected stages.