Method for determining a pulse position in a signal

• US 20080025386A1
• Filed: 06/29/2007
• Published: 01/31/2008
• Est. Priority Date: 06/30/2006
• Status: Active Grant

• Current Assignee: IMEC International
• Original Assignee: Interuniversitair Micro-Electronica Centrum VZW (IMEC International)
• Inventors: Badaroglu, Mustafa, Desset, Claude
• Granted Patent: US 7,885,326 B2
• Time in Patent Office: Days
• US Class Current: 375/239
• CPC Class Codes: H03K 9/04 of position-modulated pulses
• CPC Class Codes: H04B 1/7183 Synchronisation
• CPC Class Codes: H04B 14/026 using pulse time characteristics modulation, e.g. width, position, interval

Abstract

A method is presented for determining an actual pulse position in a signal. This signal comprises a plurality of successive frames, wherein each frame has length L and contains one pulse with width W, a number of discrete possible pulse positions being considered within in each frame which is at least L/W. The method comprises the steps of a) sampling the signal at a sampling rate below L/W with a varying sampling phase such that the whole frame length L is covered, b) obtaining a set of samples with at least one at each of the possible pulse positions, c) correlating this set of samples with a set of one or more predetermined values and d) determining the actual pulse position from said correlation. The method provides a low-complex signal acquisition solution in a receiver and is particularly useful for low-complexity and low-power IR-UWB transceivers.

Claims

1. A method for determining an actual pulse position in a signal, said signal comprising a plurality of successive frames, wherein each frame has length L and contains one pulse with width W, a number of discrete possible pulse positions being considered within in each frame which is at least L/W, the method comprising the steps of:

a) sampling said signal at a sampling rate below L/W with a varying sampling phase such that the whole frame length L is covered,

b) obtaining a set of samples with at least one at each of the possible pulse positions,

c) correlating said set of samples with a set of one or more predetermined values, and

d) determining said actual pulse position from said correlation.

2. The method according to claim 1, wherein said set of predetermined values forms a code, and wherein a fixed number of said successive frames forms a repeated symbol containing said code, the method further comprising the step of:

e) determining a code phase from said correlation, said code phase being an offset between said repeated symbol and said code.

3. The method according to claim 2, wherein said pulse position and said code phase are determined together by correlating said set of samples with rotated versions of said set of predetermined values.

4. The method according to claim 3, wherein said sampling rate is equal to the pulse repetition frequency of said signal.

5. The method according to claim 3, wherein said method is performed in both an I-branch and a Q-branch of a receiver, and wherein said receiver uses binary phase-shift keying (BPSK).

6. The method according to claim 3, wherein said method is performed on a common branch of a receiver, and wherein said receiver uses pulse position modulation (PPM).

7. A method according to claim 3, further comprising:

f) accumulating noise for computing a noise threshold; and

g) comparing said computed correlations with said computed noise threshold.

8. The method according to claim 7, further comprising the step of detecting the end of a preamble of said signal by:

h) accumulating signal for computing an end of preamble threshold,

i) correlating a decision variable representing processed signal with said code,

j) comparing the correlation results to the EOP threshold; and

k) determining the EOP according to said comparison.

9. A device operative to determine an actual pulse position in a signal, wherein said signal comprising a plurality of successive frames, wherein each frame has length L and contains one pulse with width W, a number of discrete possible pulse positions being considered within in each frame which is at least L/W, wherein the device is operative to perform the steps of a) sampling said signal at a sampling rate below L/W with a varying sampling phase such that the whole frame length L is covered;

b) obtaining a set of samples with at least one at each of the possible pulse positions;

c) correlating said set of samples with a set of one or more predetermined values, wherein said set of predetermined values forms a code, and wherein a fixed number of said successive frames forms a repeated symbol containing said code, d) determining said actual pulse position from said correlation, and e) determining a code phase from said correlation, said code phase being an offset between said repeated symbol and said code, wherein said pulse position and said code phase are determined together by correlating said set of samples with rotated versions of said set of predetermined values, and wherein the device comprises;

a serial-to-parallel converter for converting said set of samples from serial data to parallel data,

a correlator for correlating said set of samples with said set of predetermined values, thereby obtaining a set of correlation values,

a selector for selecting a maximum among said set of correlation values, said maximum defining the actual pulse position.

10. The device of claim 9, wherein said correlator is a sliding correlator providing rotated versions of said set of predetermined values during said correlation and computing all the rotated correlations with a throughput of one per each clock cycle and incoming decision variable.

11. The device of claim 9, wherein said device is part of an IR-UWB transceiver.