Method and system for fast acquisition of pulsed signals

• US 20020018514A1
• Filed: 06/28/2001
• Published: 02/14/2002
• Est. Priority Date: 07/06/2000
• Status: Active Grant

• Current Assignee: Humatics Corporation
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Roberts, Mark D., Haynes, Leonard S.
• Granted Patent: US 6,959,031 B2
• Time in Patent Office: Days
• US Class Current: 375/130
• CPC Class Codes: H04B 1/7183 Synchronisation

Abstract

A method and system for fast acquisition of pulsed radio signals where said signals comprised uniquely-spaced pulses or symbols. The receiver searches for and detects two ore more symbols, determines the interval or intervals between the symbols, and because the intervals are unique, the symbols or symbol sequences are identified. Identification of the symbols and their respective timing within the signal allows the receiver to adjust its timing to synchronize with the full signal.

Claims

1. A method for fast acquisition of impulse radio signals, comprising the steps of:

a. receiving via an impulse radio receiver a signal, said signal comprises a plurality of symbols and an interval between each such symbol in said signal is substantially unique;

b. detecting a first detected symbol and a second detected symbol of any said symbols in said signal;

c. determining a first interval between said first detected symbol and said second detected symbol; and

d. comparing said first interval to a set of intervals, said set of intervals being a set of the intervals between each symbol in said signal to determine the timing of said first detected symbol and said second detected symbol with respect to said signal.

2. The method according to claim 1, wherein said step of detecting a first detected symbol and a second detected symbol comprises the steps of

a. searching a temporal division of the signal;

and

b. iteratively varying initiation of the search by some time equal to a fraction of the duration of said temporal division.

3. The method according to claim 2, wherein said fraction is at least ¼

.

4. The method according to claim 2, wherein said fraction is at most ¼

.

5. The method according to claim 2, wherein said fraction is at least ⅛

.

6. The method according to claim 1, further comprising the steps of

a. detecting a third detected symbol;

b. determining a second interval between said third detected symbol and said second detected symbol; and

c. comparing said second interval to said set of intervals to determine the timing of a sequence of detected symbols comprised of said first detected symbol, said second detected symbol, and said third detected symbol.

7. The method according to claim 6, wherein said step of detecting said third detected symbol comprises:

a. searching a temporal division of the signal; and

b. iteratively varying initiation of the search by some time equal to a fraction of the duration of said temporal division.

8. The method according to claim 7, wherein said fraction is at least ¼

.

9. The method according to claim 7, wherein said fraction is at most ¼

.

10. The method according to claim 9, wherein said fraction is at least ⅛

.

11. The method according to claim 6, further comprising the steps of

a. detecting an n^th detected symbol;

b. determining an n−

1^th interval between said n^th detected symbol and an n−

1^th detected symbol; and

c. comparing said n−

1^th interval to said set of intervals, to determine the timing of a sequence of detected symbols comprised of n detected symbols.

12. The method according to claim 11, wherein said step of detecting said n^th detected symbol further comprises the steps of:

a. searching for the duration of a temporal division, δ

, of said signal; and

b. iteratively varying initiation of the search by some time equal to a fraction of said δ

.

13. The method according to claim 12, wherein said fraction is at least ¼

.

14. The method according to claim 12, wherein said fraction is at most ¼

.

15. The method according to claim 14, wherein said fraction is at least ⅛

.

16. The method according to claim 12, wherein detecting said first detected symbol and said second detected symbol and said nth detected symbol comprises:

a. searching a time period approximately equal to said δ

;

b. delaying searching for a multiple of said δ

; and

c. repeating as required until said signal has been traversed.

17. The method according to claim 16, wherein said multiple occurs according to any one of a group of searching algorithms consisting of pseudo-random searching, binary searching, and N-ary searching.

18. The method according to claim 16, wherein detecting said first detected symbol comprises initiating a search for said first detected symbol at some random time, t₀.

19. The method according to claim 18, wherein detecting said second detected symbol comprises initiating a search for said second detected symbol at some time, t₀+δ

.

20. The method according to claim 19, wherein detecting said n^th detected symbol comprises initiating a search for said nth detected symbol at some time, t₀+(n−

1)*δ

.

21. The method according to claim 20, wherein said signal is comprised of 2^N symbols.

22. The method according to claim 20, wherein

a. said signal is comprised of S symbols;

b. each of said S symbols is a frame of time comprised of S subframes;

c. each of said subframes is a period of time of sufficient duration for a pulse to occur within said subframe; and

d. each of said S symbols is represented by a pulse occurring in a subframe in each frame such that no pulse occurs in corresponding subframes in any other frame in said code signal.

23. The method according to claim 22, wherein said signal is comprised of said S symbols such that an i^th symbol is represented 5 by a frame of sequentially occurring subframes and a pulse occurring in an i^th subframe of said frame.

25. The method according to claim 24, further comprising the steps of:

a. detecting an n^th pulse;

b. determining a timing value of said n^th pulse relative to t₀;

c. determining an n−

1^th interval between said n^th pulse and an n−

1^th pulse; and

d. comparing said n−

1^th interval to said set of intervals to determine the timing of a sequence of n pulses with respect to said code signal.

26. The method according to claim 25, further comprising the step of testing each possible combination of said pulses to determine a proper sequence comprised of said pulses, said sequence being defined by said code signal.

28. The system according to claim 27, wherein said means for determining said interval and comparing said interval is a processor, said processor programmed to implement data structures, said data structures being capable of receiving and storing pulse timing data with respect to said pulse train and a set of intervals, said set of intervals being comprised of the intervals between each of said pulses in said pulse train.

29. The system according to claim 27, wherein said means for determining said interval and comparing said interval is implemented with a field programmable gated array.

30. The system according to claim 27, wherein said means for determining said interval and comparing said interval is implemented with a shift register.

24. A method for acquisition of impulse radio signals, comprising the steps of:

a. transmitting via an impulse radio transmitter a pulse train, said 10 pulse train being comprised of a plurality of pulses occurring in time such that a time interval between each of said plurality of pulses is substantially unique;

b. receiving said pulse train via an impulse radio receiver;

c. detecting a first pulse and a second pulse, said detecting of said first pulse being initiated at some random time, t₀;

d. determining a timing value of said first pulse and said second pulse relative to t₀;

e. determining a first interval between said first pulse and said second pulse;

f. comparing said first interval to a set of intervals, said set of intervals being a set of the intervals between each pulse in said pulse train to determine the timing of said first pulse and said second pulse with respect to said code signal; and

g. adjusting the timing of said impulse radio receiver with respect to t₀ and said code signal.

27. A system for fast synchronization of impulse radio receiver timers, comprising:

a. a means for transmitting an impulse radio pulse train, said pulse train being comprised of a plurality of pulses occurring in time such that a time interval between each of said plurality of pulses is substantially unique;

b. a means for receiving said pulse train responsive to said transmitting means;

c. a means for detecting any of said pulses responsive to said receiving means; and

d. a means for determining an interval between any two of said pulses and comparing said interval to said set of intervals to determine the timing of a sequence of pulses in said pulse train

31. A system for synchronizing impulse radio receivers, comprising:

a. an impulse radio transmitter capable of transmitting a signal, said signal being comprised of a plurality of symbols such that an interval between each such symbol in said signal is substantially unique;

b. an impulse radio receiver responsive to said transmitter, said receiver capable of receiving said signal; and

c. a processor having an input coupled to the output of said receiver and an output coupled to said receiver forming a control loop.

32. The system according to claim 31, wherein said processor is enabled to:

a. implement a first data structure capable of receiving symbol timing data with respect to said signal;

b. implement a second data structure capable of storing a sequence of symbols defined by said signal and a set of intervals, said set of intervals being comprised of the intervals between said symbols in said signal;

c. determine an interval between of any two of said symbols and compare said interval to said set of intervals;

d. test each possible combination of symbols to determine a proper sequence of symbols with respect to said signal; and

e. transmit to said receiver timer synchronization information.

33. The system according to claim 32, wherein said processor is a field programmable gated array.

34. The system according to claim 32, wherein said processor is coupled to a shift register.