Encoding apparatus and method for a position coded pulse communication system

• US 4,668,950 A
• Filed: 10/19/1983
• Issued: 05/26/1987
• Est. Priority Date: 10/19/1983
• Status: Expired due to Term

• Current Assignee: Vega Precision Laboratories, Inc. (Ultra Electronics Holdings PLC)
• Original Assignee: Vega Precision Laboratories, Inc. (Ultra Electronics Holdings PLC)
• Inventors: Hayworth, Robert G., Russell, Ray E. Jr.
• Primary Examiner(s): YUSKO, DONALD
• Application Number:
  US06/543,421
• Time in Patent Office: 1,315 Days
• Field of Search: 340/825.63, 340/835.64, 340/825.65, 340/870.24, 340/696, 340/350, 375/23, 375/94, 375/96, 375/116, 375/23, 371/69, 371/70, 371/61, 371/62, 371/2, 370/8, 370/9, 370/10, 307/234, 307/269, 307/517, 307/518, 244/189, 244/190, 244/3.11, 244/3.14, 244/3.19, 343/171.1 PF
• US Class Current: 340/4.21
• CPC Class Codes: F41G 7/306 for transmitting guidance signals; F41G7/308 takes precedence
• CPC Class Codes: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• CPC Class Codes: G08C 19/24 using time shift of pulses
• CPC Class Codes: G08C 25/00 Arrangements for preventing or correcting errors; Monitoring arrangements

Abstract

Pulse position coding is used to transmit several channels of data from a ground radar transmitter to a receiver in an airborne, remotely-piloted vehicle. The system is designed to ignore interfering pulses, especially those which are synchronized with the transmitter'"'"'s PRF, by combining a number of noise reduction devices. These include the redundant transmission of address and channel information, the transmission of true and complemented data, the tracking of channels transmitted in a predetermined order, developing an interference count to recognize synchronous pulses, comparing data received for a given channel with data subsequently received for that channel, the use of windows around the expected positions of pulses, and the use of parity. There is also a novel programming arrangement which enables several programs to be stored in a reduced amount of memory space.

Claims

1. An encoder for encoding a plurality of channels of proportional data into a plurality of position-coded pulse trains, for transmission to a selected one of a plurality of addresses, each of said pulse trains comprising a reference pulse and four pre-reference pulses, said encoder comprising:

reference pulse generating means for generating the reference pulses at a substantially constant interval;

synchronization means responsive to the reference pulses for measuring the interval between two reference pulses and for providing a trigger signal at a predetermined time position in advance of a subsequent reference pulse;

encoder processor means for calculating, from address, channel and data information, and the predetermined time position, a first count representing the time position of the first pre-reference pulse in relation to the trigger signal, a second count representing the time position of the second pre-reference pulse in relation to the trigger signal, a third count representing the time position of the third pre-reference pulse in relation to the trigger signal, and a fourth count representing the time position of the fourth pre-reference pulse in relation to the trigger signal; and

pre-reference pulse generating means coupled to said encoder processor means for generating the four pre-reference pulses in response to the trigger signal, said pre-reference pulse generating means comprising counter means for storing the calculated counts and for generating the four pre-reference pulses at the end of counting the stored counts.

2. An encoder as claimed in claim 1 wherein said pre-reference pulse generating means comprises:

address pulse generating means activated in response to the trigger signal for generating an address pulse, said address pulse generating means comprising address counter means for storing the first count;

frame pulse generating means activated in response to the trigger signal for generating a frame pulse, said frame pulse generating means comprising frame counter means for storing the second count;

channel pulse generating means activated in resonse to the trigger signal for generating a channel pulse, said channel pulse generating means comprising channel counter means for storing the third count; and

data pulse generating means activated in response to the trigger signal for generating a data pulse, said data pulse generating means comprising data counter means for storing the fourth count.

3. An encoder as claimed in claim 1 wherein said reference pulse generating means comprises:

internal reference pulse generating means for producing internal reference pulses at a manually selected interval;

external reference pulse input means for accepting external reference pulses; and

selector means connected to said internal reference pulse generating means and said external reference pulse input means for selecting either the internal or the external reference pulses as the reference pulses.

4. An encoder for address information and data in a plurality of position-coded pulse trains having a predetermined format including a first pair of pulses spaced from each other at a first interpulse interval representing the address information, a second pair of pulses spaced from each other at a second interpulse interval representing the data, and a third pair of pulses spaced from each other at a third interpulse interval representing the address information, one of said pulses in each pulse train comprising a reference pulse, said encoder comprising:

reference pulse generating means for generating the reference pulses at a substantially constant interval;

synchronization means responsive to the reference pulses for measuring the interval between two reference pulses and for providing a trigger signal at a predetermined time position in advance of a subsequent reference pulse;

encoder processor means for calculating, from the address and data information, a count representing the time position of each pulse in the format, other than the reference pulse, in relation to the trigger signal; and

pulse generating means coupled to said encoder processor means for generating the pulses, other than the reference pulses, in response to the trigger signal, said pulse generating means comprising counter means for storing the calculated counts and for generating the pulses at the end of counting the stored counts.

5. An encoder as claimed in claim 4 for encoding a plurality of channels of data, each of said channels being encoded in a separate pulse train, wherein said format further includes a fourth pair of pulses spaced from each other at a fourth interpulse interval representing a channel, said encoder processor means calculating the counts from the address, channel, and data information.

6. An encoder as claimed in claim 5 wherein at least two of said channels contain proportional data, the data in each of said two channels being the complement of the data in the other.

7. An encoder as claimed in claim 5 wherein the plurality of channels of data are encoded in a predetermined order.

8. An encoder as claimed in claim 5 wherein said format further includes a fifth pair of pulses spaced from each other at a fifth interpulse interval representing the channel.

9. In a communication system transmitting address and channel information and data in a plurality of five-pulse, position-coded pulse trains, a method of formatting each pulse train comprising the steps of:

providing first and second pulses wherein the leading edges of the first and second pulses are separated by a first interpulse interval, the duration of the first interpulse interval being chosen to indicate the address information;

providing a third pulse wherein the leading edges of the second and third pulses are separated by a second interpulse interval, the duration of the second interpulse interval being chosen to indicate the channel information;

providing a fourth pulse wherein the leading edges of the second and fourth pulses are separated by a third interpulse interval, the duration of the third interpulse interval being chosen to indicate the data; and

providing a fifth pulse wherein the leading edges of the third and fifth pulses are separated by a fourth interpulse interval, the duration of the fourth interpulse interval being chosen to indicate and confirm the address information and wherein the leading edges of the second and fifth pulses are separated by a fifth interpulse interval, the duration of the fifth interpulse interval being chosen to indicate and confirm channel information such that the fourth and fifth interpulse intervals can be used to verify information indicated by the first and second interpulse intervals.

10. In an encoder for encoding address information and data in the interpulse intervals of a plurality of position-coded pulse trains, said encoder comprising three counters each generating a separate pulse, each of said pulse trains having a predetermined format including a reference pulse, a first non-reference pulse generated upon the counting out of a first one of said counters, a second non-reference pulse generated upon the counting out of a second one of said counters, and a third non-reference pulse generated upon the counting out of a third one of said counters, said reference pulses of said pulse trains occurring at a pulse repetition frequency (PRF), a method for encoding the address information and the data in the interpulse intervals of a pulse train, said method comprising the steps of:

measuring the PRF;

generating a trigger signal at a predetermined time position in advance of a reference pulse;

calculating from the address information a first count representing the time position of one of the non-reference pulses following the trigger signal;

loading the first counter with the first count;

calculating from the address information a second count representing the time position of another of the non-reference pulses following the trigger signal;

loading the second counter with the second count;

calculating from the data a data count representing the time position of another of the non-reference pulses following the trigger signal;

loading the third counter with the data count;

starting the counters counting in response to the trigger signal; and

combining the pulses generated by said counters with the reference pulse to produce the pulse train.

11. The method of claim 10 for encoding a plurality of channels of data, each of said channels being encoded in a separate pulse train, said encoder further comprising a fourth counter, said format further including a fourth non-reference pulse generated upon the counting out of the fourth counter, said method further comprising the steps of:

calculating from channel information a fourth count representing the time position of another of the non-reference pulses following the trigger signal; and

loading the fourth counter with the fourth count.

12. The method of claim 11 wherein at least two of said channels contain proportional data, the data in each of said two channels being the complement of the data in the other.

13. The method of claim 11 wherein the plurality of channels of data are encoded in a predetermined order.

14. A method of encoding address and channel information and data in a position-coded pulse train having a predetermined format comprising a final reference pulse, an address pulse generated by the counting out of a preloaded address counter, a frame pulse generated by the counting out of a preloaded frame counter, a channel pulse generated by the counting out of a preloaded channel counter, and a data pulse generated by the counting out of a preloaded data counter, said method comprising the steps of:

generating a trigger pulse at a predetermined time in advance of the reference pulse;

calculating from the address information a channel count representing the time position of the channel pulse following the trigger signal;

preloading the channel counter with the channel count;

calculating from the address and channel information a frame count representing the time position of the frame pulse following the trigger signal;

preloading the frame counter with the frame count

calculating from the address and channel information an address count representing the time position of the address pulse following the trigger signal;

preloading the address counter with the address count;

calculating from the frame count and the data a data count representing the time position of the data pulse following the trigger signal;

preloading the data counter with the data count;

starting the counters counting in response to the trigger signal; and

combining the address, frame, channel, data, and reference pulses into the pulse train.