Synchronous spread-spectrum communications system and method

• US 5,228,056 A
• Filed: 12/14/1990
• Issued: 07/13/1993
• Est. Priority Date: 12/14/1990
• Status: Expired due to Term

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Schilling, Donald L.
• Primary Examiner(s): SWANN, TOD R
• Application Number:
  US07/626,109
• Time in Patent Office: 942 Days
• Field of Search: 375/1, 375/38, 375/48, 375/66, 375/89, 455/59, 455/103, 455/209, 455/216, 455/303, 380/33, 380/34, 380/40
• US Class Current: 375/144
• CPC Class Codes: G01S 13/82 wherein continuous-type signals are transmitted
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 7/18547 for geolocalisation of a station position fixing by direction or distance determination G01S5/00
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 distributing total power among users or channels

Abstract

A spread spectrum communications system for use over a communications channel, including a transmitter-generic-chip-code generator, a transmitter-message-chip-code generator, an EXCLUSIVE-OR gate, a combiner, a transmitter, a receiver-generic-chip-code generator, a receiver-generic mixer, a generic-bandpass filter, a receiver-message-chip-code generator, a receiver-message mixer, a message-bandpass filter, and a synchronous detector. The transmitter-generic-chip-code generator generates a generic-chip-code signal and the transmitter-message-chip-code generator generates a message-chip-code signal. The EXCLUSIVE-OR gate spread-spectrum processes message data with the message-chip-code signal to generate a spread-spectrum signal. The combiner combines the generic-chip-code signal with the spread-spectrum-processed signal. The transmitter transmits the combined generic-chip-code signal and spread-spectrum signal, on a carrier signal over the communications channel as a spread-spectrum-communications signal. The receiver-generic-chip-code generator generates a replica of the generic-chip-code signal. The generic mixer recovers the carrier signal from the spread-spectrum-communications signal. The receiver-message-chip-code generator generates a replica of the message-chip-code signal. The receiver-message mixer despreads the spread-spectrum-communications signal as a modulated-data signal. The tracking and acquisition circuit uses the recovered carrier signal for synchronizing the replicas of the generic-chip-code signal to the recovered carrier signal. The synchronous detector synchronously demodulates the modulated-data signal as received data.

Claims

1. A spread spectrum communications system for use over a communications channel, comprising:

a transmitter-generic-chip-code generator for generating a generic-chip-code signal;

a transmitter-message-chip-code generator for generating a message-chip-code signal;

an EXCLUSIVE-OR gate coupled to said transmitter-message-chip-code generator for spread-spectrum processing message data with the message-chip-code signal to generate a spread-spectrum-processed signal;

a combiner coupled to said transmitter-generic-chip-code generator and said EXCLUSIVE-OR gate for combining the generic-chip-code signal with the spread-spectrum-processed signal;

a transmitter coupled to said combiner for transmitting the combined generic-chip-code signal and spread-spectrum-processed signal, on a carrier signal over said communications channel as a spread-spectrum-communications signal;

a receiver-generic-chip-code generator for generating a replica of the generic-chip-code signal;

a generic mixer coupled to said receiver-generic-chip-code generator for recovering the carrier signal from the spread-spectrum-communications signal;

a receiver-message-chip-code generator coupled to said receiver-generic-chip-code generator and synchronized to the replica of the generic-chip-code signal for generating a replica of the message-chip-code signal;

a message mixer coupled to said receiver-message-chip-code generator and responsive to the replica of the message-chip-code signal for despreading the spread-spectrum-communications signal as a modulated-data signal;

a message-bandpass filter coupled to said message mixer for filtering the modulated-data signal;

a generic-bandpass filter coupled to said generic mixer for filtering the recovered-carrier signal recovered from the spread-spectrum-communications signal;

a tracking and acquisition circuit coupled to an output of said generic-bandpass filter and to said receiver-generic-chip-code generator, said tracking and acquisition circuit responsive to acquiring and tracking the recovered-carrier signal for synchronizing the generic-chip-code signal to the recovered-carrier signal;

a power splitter coupled between said communications channel, said generic mixer and said message mixer for dividing the spread-spectrum-communications signal between said generic mixer and said message mixer; and

a synchronous detector coupled to said message-bandpass filter, responsive to the recovered carrier signal recovered by the generic-mixer device for synchronously demodulating the modulated-data signal as a detected signal.

2. A spread spectrum communications system for use over a communications channel, comprising:

generic means for generating a generic-chip-code signal;

message means for generating a message-chip-code signal;

spreading means for spread-spectrum processing message data with the message-chip-code signal to generate a spread-spectrum-processed signal;

summer means for combining the generic-chip-code signal with the spread-spectrum-processed signal;

means for transmitting the combined generic-chip-code signal and spread-spectrum-processed signal, on a carrier signal over said communications channel as a spread-spectrum-communications signal;

generic-spread-spectrum-processing means for recovering the carrier signal from the spread-spectrum-communications signal and for generating a replica of the generic-chip-code signal synchronized to the recovered-carrier signal;

acquisition means responsive to acquiring and tracking the recovered-carrier signal for synchronizing said generic-spread-spectrum-processing means to the recovered-carrier signal;

message-spread-spectrum-processing means for despreading the spread-spectrum-communications signal as a modulated-data signal;

detection means for detecting the modulated-data signal as a detected signal; and

synchronous means responsive to the generic-chip-code signal for synchronously converting the detected signal to received data.

3. The spread spectrum communications system as set forth in claim 2 wherein said detection means includes a synchronous detector responsive to the recovered-carrier signal for converting the modulated-data signal to the detected signal.

4. The spread spectrum communications system as set forth in claim 2 wherein said message-spread-spectrum-processing means includes means for storing a replica of the message-chip-code signal for despreading the spread-spectrum-communications signal as a modulated-data signal.

5. The spread spectrum communications system as set forth in claim 2 wherein said generic-spread-spectrum-processing means includes means for storing a replica of the generic-chip-code signal for despreading the spread-spectrum-communications signal as the recovered-carrier signal.

6. The spread spectrum communications system as set forth in claim 2 wherein detection means includes an envelope detector for converting the modulated-data signal to the detected signal.

7. The spread spectrum communications system as set forth in claim 5 wherein detection means includes a synchronous detector responsive to the recovered-carrier signal for converting the modulated-data signal to the detected signal.

8. The spread spectrum communications system as set forth in claim 2 wherein said synchronous means further includes:

a low pass filter;

an electronic switch coupled at an output of said lowpass filter; and

bit means responsive to the received data at an input to said lowpass filter for integrating and dumping said lowpass filter and said electronic switch.

9. The spread spectrum communications system as set forth in claim 2 wherein said synchronous means further includes:

a low pass filter;

an electronic switch coupled at an output of said lowpass filter; and

bit means responsive coupled to said generic-spread-spectrum-processing means and responsive to the replica of the generic-chip-code signal for integrating and dumping said lowpass filter and said electronic switch.

10. A method for synchronously demodulating spread spectrum communications, comprising the steps of:

generating a generic-chip-code signal;

generating a message-chip-code signal;

spread-spectrum processing message data with the message-chip-code signal to generate a spread-spectrum-processed signal;

combining the generic-chip-code signal with the spread-spectrum-processed signal;

transmitting the combined generic-chip-code signal and spread-spectrum-processed signal on a carrier signal over a communications channel as a spread-spectrum-communications signal;

recovering, using a replica of the generic-chip-code signal, the carrier signal from the spread-spectrum-communications signal;

acquiring and tracking the recovered-carrier signal;

generating, synchronized to the recovered-carrier signal, the replica of the generic-chip-code signal;

generating a replica of the message-chip-code signal synchronized to the replica of the generic-chip-code signal;

despreading, using the replica of the message-chip-code signal, the spread-spectrum-communications signal as a modulated-data signal; and

demodulating the modulated-data signal as received data.

11. The method as set forth in claim 10 wherein the step of demodulating includes synchronously converting the modulated-data signal to the received data.

12. The method as set forth in claim 10 wherein the despreading step includes the step of storing a replica of the message-chip-code signal for despreading the spread-spectrum-communications signal as a modulated-data signal.

13. The method as set forth in claim 10 wherein the recovering step includes the step of storing a replica of the generic-chip-code signal for despreading the spread-spectrum-communications signal as the recovered carrier signal.

14. The method as set forth in claim 10 wherein the demodulating step includes synchronously demodulating, using the recovered-carrier signal, the modulated-data signal as a detected signal.

15. A spread spectrum communications receiver comprising:

generic-spread-spectrum-processing means for recovering a carrier signal from a spread-spectrum-communications signal;

message-spread-spectrum-processing means for despreading a spread-spectrum-communications signal as a modulated-data signal;

acquisition means responsive to acquiring and tracking the recovered-carrier signal for synchronizing said generic-spread-spectrum-processing means to the recovered carrier signal; and

detection means for converting the modulated-data signal to a detected signal.

16. The spread spectrum communications receiver as set forth in claim 15 wherein said detection means includes a synchronous detector responsive to the recovered-carrier signal for synchronously demodulating the modulated-data signal as the detected signal.

17. The spread spectrum communications receiver as set forth in claim 15 wherein said message-spread-spectrum-processing means includes means for storing a replica of the message-chip-code signal for despreading the spread-spectrum-communications signal as the modulated-data signal.

18. The spread spectrum communications receiver as set forth in claim 15 wherein said generic-spread-spectrum-processing means includes means for storing a replica of the generic-chip-code signal for despreading the spread-spectrum-communications signal as the recovered carrier signal.

19. The spread spectrum communications receiver as set forth in claim 15 wherein said detection means includes an envelope detector for converting the modulated-data signal to the detected signal.

20. The spread spectrum communications receiver as set forth in claim 18 wherein:

said generic-spread-spectrum-processing means generates a generic-chip-code signal; and

said message-spread-spectrum means, responsive to the generic-chip-code signal, generates a message-chip-code signal for despreading the spread-spectrum-communications signal as the modulated-data signal.

21. The spread spectrum communications receiver as set forth in claim 15 wherein said detection means further includes:

a low pass filter;

an electronic switch coupled at an output of said lowpass filter; and

bit means responsive to the detected signal at an input to said lowpass filter for integrating and dumping said lowpass filter with said electronic switch.

22. The spread spectrum communications receiver as set forth in claim 20 wherein said detection means further includes:

a low pass filter;

an electronic switch coupled at an output of said lowpass filter; and

bit means responsive coupled to said generic-spread-spectrum-processing means and responsive to the generic-chip-code signal for integrating and dumping said lowpass filter with said electronic switch.

23. A spread spectrum communications system for use over a communications channel, comprising:

generic means for generating a generic-chip-code signal;

a plurality of message means for generating a plurality of message-chip-code signals;

a plurality of spreading means for spread-spectrum processing a plurality of message data with the plurality of message-chip-code signals to generate a plurality of spread-spectrum-processed signals;

summer means for combining the generic-chip-code signal with the plurality of spread-spectrum-processed signals;

means for transmitting the combined generic-chip-code signal and the plurality of spread-spectrum-processed signals, on a carrier signal over said communications channel as a spread-spectrum-communications signal;

generic-spread-spectrum-processing means for recovering the carrier signal from the spread-spectrum-communications signal and for generating a replica of the generic-chip-code signal;

acquisition means responsive to acquiring and tracking the recovered carrier signal for synchronizing said generic-spread-spectrum-processing means to the recovered-carrier signal;

of message-spread-spectrum-processing means synchronized to the replica of the generic-chip-code signal for despreading the spread-spectrum-communications signal as a plurality of modulated-data signals; and

a plurality of detection means for detecting the plurality of modulated-data signals as a plurality of detected signals, respectively.

24. The spread spectrum communications system as set forth in claim 23 wherein said plurality of detection means includes a plurality of a synchronous detectors responsive to the recovered-carrier signal for synchronously detecting the plurality of modulated-data signals as the plurality of detected signals, respectively.

25. The spread spectrum communications system as set forth in claim 23 wherein said plurality of message-spread-spectrum-processing means includes means for storing a plurality of replicas of the message-chip-code signals for despreading the spread-spectrum-communications signal as the plurality of modulated-data signals.

26. The spread spectrum communications system as set forth in claim 23 wherein said generic-spread-spectrum-processing means includes means for storing a replica of the generic-chip-code signal for despreading the spread-spectrum-communications signal as the recovered-carrier signal.

27. The spread spectrum communications system as set forth in claim 23 wherein a plurality of detection means includes a plurality of envelope detectors for converting the plurality of modulated-data signals to the plurality of detected signals, respectively.

28. The spread spectrum communications system as set forth in claim 23 wherein said plurality of message means is synchronized to the generic-chip-code signal from said generic means.

29. The spread spectrum communications system as set forth in claim 23 an output of each of the plurality of detection means further includes:

a low pass filter;

an electronic switch coupled at an output of said lowpass filter; and

bit means responsive to the detected signal at an input to said lowpass filter for integrating and dumping said lowpass filter and said electronic switch.

30. The spread spectrum communications system as set forth in claim 23 further including coupled to an output of said detection means:

a low pass filter;

an electronic switch coupled at an output of said lowpass filter; and

bit means responsive coupled to said generic-spread-spectrum-processing means and responsive to the replica of the generic-chip-code signal for integrating and dumping said lowpass filter and said electronic switch.

31. A spread-spectrum transmitter system comprises of:

generic means for generating a generic-chip-code signal;

message means synchronized to the generic-chip-code signal for generating a message-chip-code signal;

spreading means for spread-spectrum processing message data with the message-chip-code signal to generate a spread-spectrum-processed signal;

summer means for combining the generic-chip-code signal with the spread-spectrum-processed signal; and

means for transmitting the combined generic-chip-code signal and spread-spectrum-processed signal on a carrier signal over a communications channel as a spread-spectrum-communications signal.

32. The spread-spectrum transmitter system as set forth in claim 31 wherein said spreading means includes an EXCLUSIVE-OR gate for processing message data with the message-chip-code signal.

33. A spread spectrum communications receiver comprising:

generic-spread-spectrum-processing means for generating a generic-chip-code signal and recovering a carrier signal from a spread-spectrum-communications signal;

a plurality of message-spread-spectrum-processing means synchronized to the generic-chip-code signal for despreading a spread-spectrum-communications signal as a plurality of modulated-data signals;

acquisition means responsive to acquiring and tracking the recovered carrier signal for synchronizing said generic-spread-spectrum-processing means to the recovered-carrier signal; and

a plurality of detection means for converting the plurality of modulated-data signals to a plurality of detected signals.

34. The spread spectrum communications receiver as set forth in claim 33 wherein each of said plurality of detection means includes a synchronous detector responsive to the recovered-carrier signal for synchronously demodulating the modulated-data signal as a detected signal.

35. The spread spectrum communications receiver as set forth in claim 33 wherein an output of each of said detection means further includes:

a low pass filter;

an electronic switch coupled at an output of said lowpass filter; and

bit means responsive to the detected signal at an input to said lowpass filter for integrating and dumping said lowpass filter with said electronic switch.

36. The spread spectrum communications receiver as set forth in claim 33 wherein an output of each of said detection means further includes:

a low pass filter;

an electronic switch coupled at an output of said lowpass filter; and

bit means responsive coupled to said generic-spread-spectrum-processing means and responsive to the generic-chip-code signal for integrating and dumping said lowpass filter with said electronic switch.

37. A method for transmitting spread spectrum communications, comprising the steps of:

generating a generic-chip-code signal;

generating a message-chip-code signal synchronously with the generic-chip-code signal;

spread-spectrum processing message data with the message-chip-code signal to generate a spread-spectrum-processed signal;

combining the generic-chip-code signal with the spread-spectrum-processed signal; and

transmitting the combined generic-chip-code signal and spread-spectrum-processed signal on a carrier signal over a communications channel as a spread-spectrum-communications signal.

38. A method for receiving spread spectrum communications comprising the steps of:

generating a generic-chip-code signal from a spread-spectrum-communications signal;

recovering a carrier signal from the spread-spectrum-communications signal;

despreading, synchronously with the generic-chip-code signal, the spread-spectrum-communications signal as a modulated-data signal;

acquiring and tracking the recovered carrier signal;

synchronizing the step of generating of the generic-chip-code signal to the recovered carrier signal; and

converting the modulated-data signal to a detected signal.

39. The method as set forth in claim 38 wherein the converting step includes the step of synchronously demodulating the modulated-data signal as a detected signal.

40. The method as set forth in claim 38 wherein the despreading step includes the step of storing a replica of the message-chip-code signal for despreading the spread-spectrum-communications signal.

41. The method as set forth in claim 38 wherein the recovering step includes the steps of:

storing a replica of the generic-chip-code signal; and

despreading the spread-spectrum-communications signal with the replica of the generic-chip-code signal as the recovered carrier signal.

42. The method as set forth in claim 38 wherein the converting step includes using an envelope detector.

43. The method as set forth in claim 41 further including the steps of:

generating a generic-chip-code signal;

generating a message-chip-code signal; and

despreading the spread-spectrum-communications signal with the message-chip-code signal as the modulated-data signal.

44. The method as set forth in claim 38 further comprising the steps of:

filtering the detected signal through a low pass filter;

passing the filtered signal through an electronic switch; and

integrating and dumping the filtered signal with the electronic switch.

45. The method as set forth in claim 38 further comprising the steps of:

filtering the detected signal through a low pass filter;

passing the filtered signal through an electronic switch; and

integrating and dumping the filtered signal with the electronic switch in response to the generic-chip-code signal.