Spread spectrum demodulator

• US 5,280,538 A
• Filed: 02/18/1992
• Issued: 01/18/1994
• Est. Priority Date: 02/22/1991
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kataoka, Nobuhisa, Kojima, Toshiharu
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US07/838,503
• Time in Patent Office: 700 Days
• Field of Search: 375/1, 375/83-87, 380/34, 329/304, 329/306, 329/307
• US Class Current: 375/149
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop

Abstract

A spread spectrum demodulator for use with a phase-shift-keying modulated spread spectrum signal used in mobile satellite communications. An objective of the spread spectrum demodulator is to perform tracking by producing from a correlation pulse signal an error signal having a time discrimination characteristic. The spread spectrum demodulator generates from the correlation pulse signal an error signal whose level varies in response to a phase difference between a pseudonoise signal contained in a received signal and a reference pseudonoise signal. A clock in synchronism with the received signal is generated from this error signal, thereby demodulating the received signal.

Claims

1. A spread spectrum demodulator for use with a phase-shift-keying modulated spread spectrum signal for demodulating data from a received signal, said spread spectrum demodulator comprising:

a) means for generating a correlation pulse signal in response to a received signal whose spectrum is spread by a pseudonoise signal; and

b) means for effecting tracking, responsive to the means for generating, including a means for generating an error signal having a time discrimination characteristic, said means for generating the error signal further including;

i) a transversal filter wherein the error signal output from said transversal filter is derived from filtering a plurality of correlation pulse signals which are each weighted by a coefficient for weighting use and wherein said coefficient for weighting use is derived from integrating a correlation pulse signal for a predetermined period.

9. A spread spectrum demodulator according to claim 1, wherein a coefficient for weighting use is derived from the correlation pulse signals which were integrated for a predetermined period.

2. A spread spectrum demodulator for use with a phase-shift-keying modulated spread spectrum signal for demodulating data from a received signal whose spectrum is spread by a pseudonoise signal, the spread spectrum demodulator comprising:

a) base band signal generator means for outputting a base band signal, including a means for receiving the received signal and for waveform-shaping the received signal into the base band signal;

b) sampled signal generator means for outputting a sampled signal, including a means for receiving the base band signal and for sampling the base band signal into the sampled signal;

c) correlator signal generator means for outputting a correlation signal, responsive to a means for generating a reference pseudonoise signal, said first generator means including a means for receiving the sampled signal and for comparing the phases of a pseudonoise component of the sampled signal and the reference pseudonoise signal, and means for generating the correlation signal when the signals are in phase;

d) correlation pulse signal generator means for outputting a correlation pulse signal, including a means for receiving the correlation signal and means for removing the data component from the correlation signal thereby producing the correlation pulse signal, each cycle of the pseudonoise signal;

e) error signal generator means for outputting an error signal, including a means for receiving the correlation pulse signal and for generating the output error signal whose level aries in response to the phase difference between the pseudonoise component of the sampled signal and the reference pseudonoise signal;

f) clock generator means, including a means for receiving the error signal and a means for generating and outputting a chip clock signal, in response to the error signal, in synchronism with the received signal; and

g) data extracting means for outputting demodulated data, including a means for receiving the correlation signal and means for extracting data from the correlation signal thereby producing demodulated data.

3. A spread spectrum demodulator according to claim 2, wherein the error signal generator means comprises a filter, and the output error signal from said filter is derived from filtering a plurality of correlation pulse signals.

4. A spread spectrum demodulator according to claim 3, wherein a coefficient for weighting use is derived from the correlation pulse signal which was integrated for a predetermined period.

5. A spread spectrum demodulator according to claim 3, wherein the filter performs weighting by means of a changeover switch, said changeover switch consisting of a switch and an inverter.

6. A spread spectrum demodulator according to claim 3, wherein a coefficient for weighting use is derived from the correlation pulse signal which was integrated for a predetermined period, and wherein the filter performs weighting by means of a changeover switch, said change over switch consisting of a switch and an inverter.

7. A spread spectrum demodulator according to claim 2, wherein the means for extracting data is comprised of a carrier wave control circuit for generating and outputting, from the correlation signal, a signal including information about the phase of a carrier wave of the received signal and a voltage controlled carrier wave generator for generating and outputting, from the signal including the information about the phase of the carrier wave, a carrier wave in phase with the carrier wave of the received signal.

8. A spread spectrum demodulator according to claim 2, wherein the error signal generator means comprises a transversal filter, and the output error signal from said filter is derived from filtering a plurality of correlation pulse signals.

10. A spread spectrum demodulator according to claim 8, wherein the transversal filter performs weighting by means of a changeover switch, said changeover switch consisting of a switch and an inverter.

11. A spread spectrum demodulator according to claim 8, wherein a coefficient for weighting use is derived from the correlation pulse signal which was integrated for a predetermined period, and wherein the transversed filter performs weighting by means of a changeover switch, said changeover switch consisting of a switch and an inverter.