Signal processing apparatus and method

• US 4,868,851 A
• Filed: 01/26/1988
• Issued: 09/19/1989
• Est. Priority Date: 01/26/1988
• Status: Expired due to Term

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Buhrman, C. Wayne, Keesom, Hendrik J., Trinidad, John M., Heinrich, Dedina M.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Huseman, Marianne
• Application Number:
  US07/148,707
• Time in Patent Office: 602 Days
• Field of Search: 375/94, 375/110, 375/40, 375/100, 375/107, 375/116, 375/113, 371/36, 371/37, 455/133-135
• US Class Current: 375/267
• CPC Class Codes: H04L 1/02 by diversity reception

Abstract

Apparatus and method for processing a common digital signal received at plural receivers in which each received signal is validated and aligned in time with the other signals. A single output signal is generated from the received signals using a voting scheme such as one in which the logic state of the majority of corresponding bits in the received signals determines the logic state of the bits in the generated signal. If there is no majority, the logic state of the best performing signal is used without revoting, or the vote is retaken without the poorest performing signal.

Claims

1. Apparatus for radio frequency signal processing, comprising:

plural receivers, each receiver being mutually geographically remote and receiving a common radio signal conveying plural bits of information, said bits being carried in plural frames;

plural sub-transmitters, each sub-transmitter being operatively connected to one of said receivers and retransmitting the received radio signal;

plural collocated sub-receivers each receiving the retransmitted radio signal from one of said sub-transmitters;

plural bit transition detectors, each detector being operatively connected to one said sub-receiver, for examining the bit transitions in the received radio signal and discarding those bits with transitions falling outside of predetermined time windows;

plural character generators, each generator being operatively connected to one said bit transition detector, for generating characters from a predetermined number of said bits in said received radio signal;

plural character examiners, each examiner being operatively connected to one said character generator, for comparing said characters to predetermined characters and discarding those characters that do not match one of the predetermined characters;

a memory, operatively connected to said character examiners, for sequentially storing for each received radio signal a plurality of the bits with accepted bit transitions from accepted characters;

a bit aligner, operatively connected to said memory, for storing each of the bits by frame so that bits from said plural received radio signals are aligned in time;

a counter, operatively connected to said bit aligner, for determining the majority logic state of the bits of each frame; and

a signal generator forming an output signal carrying plural output bits of digital information with the logic state of each output bit relating frame-by-frame to the majority logic state, and if there is no majority logic state for a frame, to a second logic state.

2. The apparatus of claim 1, further comprising:

a recorder, operatively connected to said counter, for recording how frequently each of said received radio signals has bits in the logic state matching said majority state; and

a signal generator wherein, the second logic state relates to the logic state of the corresponding bit in the received radio signal that most frequently has bits matching the majority logic state.

3. The apparatus of claim 1, further comprising:

a recorder, operatively connected to said counter, for recording how frequently each of said received radio signals has bits in the logic state matching said majority state; and

a signal generator wherein, the second logic state relates to the logic state of a second majority logic state determined by said counter not including the received radio signal that least frequently has bits matching the majority logic state.

4. Apparatus for signal processing, comprising:

plural means for receiving signals carrying plural framed bits of information from a common signal;

plural means for rejecting mistimed or improperly formatted received signals;

means for time-aligning in frames, bits from the received signals;

means for determining the majority logic state of the bits in each frame; and

means for generating an output signal carrying plural output bits, wherein the logic state of each output bit relates to said majority logic state, and when there is not a majority logic state, the logic state of each output bit relates to the logic state of the corresponding bit in the received signal with the best history of having bits matching said majority logic state.

5. The apparatus of claim 4, wherein said received signals are diverse in frequency.

6. The apparatus of claim 4, wherein said means for receiving signals are collocated.

7. The apparatus of claim 4, wherein said means for receiving signals are mutually geographically remote.

8. Apparatus for signal processing, comprising:

plural means for receiving signals carrying plural framed bits of information from a common signal;

plural means for rejecting mistimed or improperly formatted received signals;

means for time-aligning in frames, bits from the received signals;

means for determining a first majority logic state of the bits in each frame;

means for determining a second majority logic state not including the signal that least frequently has bits matching said first majority logic state; and

means for generating an output signal carrying plural bits wherein the logic state of each bit relates to said first majority logic state, and when there is not a majority logic state, the logic state of each bit relates to said second majority logic state.

9. The apparatus of claim 8, wherein said received signals are diverse in frequency.

10. The apparatus of claim 8, wherein said means for receiving signals are collocated.

11. The apparatus of claim 8, wherein said means for receiving signals are mutually geographically remote.

12. Signal processing apparatus, comprising:

plural means to receive a common signal;

means to synchronize to each other signals received at said receiver means, said synchronizing meas being operatively connected to said plural receiver means; and

a processor operatively connected to said synchronizing means for generating an output signal, said processor comprising,

means for determining the majority logic state of said synchronized signals,

a first means to generate an output signal related to said majority, and p2 a second means to generate an output signal if there is no said majority.

13. A method for processing signals, comprising the steps of:

(a) receiving at plural receivers a common signal of plural bits of information, bits being carried in plural frames;

(b) detecting bit transitions in said received signals that fall outside of predetermined windows;

(c) discarding said received bits having bit transitions falling outside of said windows;

(d) generating a character from a predetermined number of said received bits;

(e) comparing the generated character to a predetermined set of characters;

f) discarding the generated character that does not match of the predetermined characters;

(g) storing sequentially, for each received signal, a plurality of the bits with accepted bit transitions from accepted characters;

(h) withdrawing bits from said storage frame-by-frame so that withdrawn bits are aligned in time;

(i) determining the majority logic state of aligned bits in each frame;

(j) recording the frequency with which each received signal has valid bits in the logic state matching said majority logic state; and

(k) forming an output signal carrying plural output bits wherein the logic state of each output bit relates to said majority logic state, and when there is not a majority logic state, to a second logic state.

14. The method of claim 13, wherein said second logic state is related to the logic state of the corresponding bit in the received signal that most frequently has bits matching the majority logic state.

15. The method of claim 13, wherein said second logic state is related to the logic state of a second majority determined as in step (i) not including the received signal that least frequently has bits matching the majority logic state.

16. The method of claim 13, wherein said plural receivers are mutually geographically remote.

17. The method of claim 13, wherein said plural receivers are mutually frequency diverse.

18. The method of claim 13, wherein said plural receivers are collocated.

19. A method for processing signals, comprising the steps of:

(a) receiving plural signals carrying plural bits of information from a common signal;

(b) retaining only the received bits having predetermined timing and format;

(c) time-aligning in frames said retained bits;

(d) determining the majority logic state of said retained bits in each frame; and

(e) generating an output signal comprising output bits with the logic state of each output bit relating frame-by-frame to the logic state of said majority state, and if there was no majority state for a frame, relating to a second logic state.

20. Signal processing method comprising the steps of:

(a) receiving at plural receivers a common signal;

(b) synchronizing to each other signals received at said plural receivers;

(c) generating an output signal related to the majority of said received signals, and

(d) generating an alternative output signal if there is no majority.

21. In a signal processor that processes signals received on plural receivers, carrying plural framed bits of information from a common signal, with means for rejecting mistimed or improperly formatted receive signals, the improvement comprising:

means for time-aligning in frames, bits in the received signals;

means for determining the majority logic state of the bits in each frame from said receive signals;

means for generating an output signal carrying plural output bits, wherein the logic state of each output bit relates to said majority logic state, and when there is not a majority logic state, the logic state of each output bit relates to a second logic state.

22. The signal processor of claim 21, further comprising:

means for recording each received signal'"'"'s history of having bits matching the logic state of the majority logic state; and

means to determine a second logic state related to the logic state of a second majority, not including the signal that least frequently has bits with a logic state matching the logic state of the majority logic state.

23. The signal processor of claim 21, further comprising:

means for recording each signal'"'"'s history of having bits matching the logic state of the majority logic state; and

means to determine a second logic state related to the logic state of the corresponding bit in the received signal with the best history of having bits matching the majority logic state.