Method and apparatus for multi-level phase shift keying communications

• US 20030103583A1
• Filed: 03/11/2002
• Published: 06/05/2003
• Est. Priority Date: 12/04/2001
• Status: Abandoned Application

• Current Assignee: National University of Singapore
• Original Assignee: National University of Singapore
• Inventors: Lye, Kin Mun, Low, Kay Soon, Ho, Paul Kar Ming
• Application Number:
  US10/096,150
• Publication Number:
  US 20030103583A1
• Time in Patent Office: Days
• US Class Current: 375/329
• CPC Class Codes: H04L 27/22 Demodulator circuits; Receiver circuits

Abstract

Methods and apparatus for detecting multiple-level phase shift keying (MPSK) signals based on detectors that have nonlinear dynamics transfer characteristics are disclosed. The receiver circuit can be implemented easily using devices such as the op-amps to provide the required dynamic characteristics. The performance is enhanced by transmitting multiple cycles of the PSK signals and gating of the received waveforms.

Claims

1. A method for detection of a phase shift keying (PSK) signal comprising:

for each cycle of said PSK signal (i) producing a first group of at least one pulse based on a positive portion of said cycle and (ii) producing a second group of at least one pulse based on a negative portion of said cycle;

applying at least one gating window to said first and second groups to retain at least one pulse within said at least one gating window and disregard at least one pulse outside of said at least one gating window; and

producing an information symbol on the basis of at least one pulse retained by said at least one gating window.

2. The method of claim 1 wherein said at least one gating window comprises a portion of a gating window waveform that is time-aligned to said PSK signal.

3. The method of claim 1 wherein said at least one gating window has a zero value near the beginning and near the end of said at least one gating window and wherein said at least one gating window is non-zero elsewhere.

4. The method of claim 1 further including providing a first circuit configured to produce said first group in response to detecting said positive portion of said cycle and providing a second circuit configured to produce said second group in response to detecting said negative portion of said cycle.

5. The method of claim 4 wherein said first and second circuits each has a transfer function characterized by an unstable region bounded by stable regions.

6. The method of claim 1 wherein said information symbol producing step includes counting pulses retained by said at least one gating window from said first and second groups to respectively produce first and second pulse counts, said information symbol being produced based on said pulse counts.

7. The method of claim 6 wherein said counting includes weighting the contribution of said pulses to a pulse count depending on which portion of said PSK signal said pulses were produced.

8. The method of claim 6 wherein for said first group, some of said pulses contribute more than one count to said first pulse count.

9. The method of claim 1 wherein said first group producing step includes limiting a maximum positive amplitude of said positive portion of said cycle to a first value.

10. The method of claim 9 wherein said limiting is a step of clamping said PSK signal.

11. The method of claim 1 wherein said first group of has positive-going pulses and said second group has negative-going pulses.

12. The method of claim 1 further including combining said first and second groups prior to said producing an information symbol.

13. The method of claim 1 further including producing a synchronization signal from said PSK signal, said step of producing an information signal including detecting said first group and said second group based on said synchronization signal.

14. The method of claim 13 wherein said synchronization signal is a sinusoidal signal having a frequency substantially equal to the frequency of a sinusoidal waveform used to represent a PSK symbol.

15. The method of claim 1 wherein said PSK signal is a binary phase shift keying (BPSK) signal.

16. The method of claim 1 wherein said PSK signal is a quaternary phase shift keying (QPSK) signal.

17. The method of claim 1 further including receiving a transmitted signal and producing said PSK signal from said transmitted signal.

18. The method of claim 1 wherein said information symbol is produced from multiple cycles of said PSK signal, on the basis of at least one pulse retained by said at least one gating window from said first and second groups corresponding to said multiple cycles of said PSK signal.

19. A circuit system for detecting a phase shift keying (PSK) signal comprising:

a first circuit configured to produce a plurality of groups of at least one positive pulse in response to detecting first portions of said PSK signal;

a second circuit configured to produce a plurality of groups of at least one negative pulse in response to detecting second portions of said PSK signal;

a windowing circuit configured to receive said plurality of groups of at least one positive pulse and said plurality of groups of at least one negative pulse, said windowing circuit also configured to retain at least one pulse within at least one gating window and disregard at least one pulse outside of said at least one gating window; and

a decoder configured to produce a plurality of information symbols based said at least one pulse retained by said at least one gating window.

20. A phase shift keying (PSK) detection system comprising:

means for receiving a transmitted PSK signal;

first means for producing a plurality of positive pulses from said received signal;

second means for producing a plurality of negative pulses from said received signal;

windowing means for applying at least one gating window to said plurality of positive pulses and said plurality of negative pulses to retain at least one pulse within said at least one gating window and disregard at least one pulse outside of said at least one gating window; and

symbol means for producing information symbols from said at least one pulse retained by said at least one gating window.