Communication device

• US 20050105595A1
• Filed: 11/17/2003
• Published: 05/19/2005
• Est. Priority Date: 11/17/2003
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Gorday, Paul E., Taubenheim, David B., Martin, Frederick L., Callaway, Edgar H.
• Granted Patent: US 7,295,638 B2
• Time in Patent Office: Days
• US Class Current: 375/140
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 2201/70707 Efficiency-related aspects
• CPC Class Codes: H04L 27/22 Demodulator circuits; Receiver circuits

Abstract

A direct sequence spread spectrum (DSSS) receiver (100) consistent with certain embodiments has a frequency generator (112) that generates a local oscillator signal without use of a piezoelectric crystal. A frequency converter (108) receives the local oscillator signal and mixes the local oscillator signal with a received DSSS signal to produce a down-converted signal. The received DSSS signal is encoded using a first set of DSSS code. A differential chip detector (116) receives the down-converted signal and converts the down-converted signal to a differentially detected signal. A correlator (120) receives the differentially detected signal and correlates the detected signal with a set of DSSS codes that are time-shifted from the first set of DSSS codes. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this abstract.

Claims

1. A direct sequence spread spectrum (DSSS) communication device, comprising:

a frequency generator that generates a local oscillator signal without use of a piezoelectric crystal;

a frequency converter that receives the local oscillator signal and mixes the local oscillator signal with a received DSSS signal to produce a down-converted signal, wherein the received DSSS signal is encoded using a first set of DSSS codes;

a differential detector that receives the down-converted signal and converts the down-converted signal to a differentially detected signal; and

a correlator that receives the differentially detected signal and correlates the differentially detected signal with a differentially detected set of DSSS codes.

2. The DSSS communication device according to claim 1, wherein the differentially detected set of DSSS codes are time-shifted from the first set of DSSS codes by an integer number of chip periods.

3. The DSSS communication device according to claim 1, wherein the differentially detected-signal comprises output chips which are a function of a plurality of successive chips of the received DSSS signal.

4. The DSSS communication device according to claim 1, wherein the frequency generator has a frequency tolerance of less than approximately 0.12/T where T is the period of a chip.

5. The DSSS communication device according to claim 1, wherein the frequency generator comprises one of an LC type oscillator, an RC type oscillator, a relaxation oscillator, a ring oscillator and a voltage controlled oscillator.

6. The DSSS communication device according to claim 5, further comprising means for initial adjustment of the frequency of the local oscillator signal.

7. The DSSS communication device according to claim 5, further comprising a compensation circuit that compensates the frequency generator against changes in temperature or operating voltage.

8. The DSSS communication device according to claim 1, wherein the frequency converter comprises a multiple conversion frequency converter.

9. The DSSS communication device according to claim 1, wherein the down-converted signal comprises a baseband signal.

10. The DSSS communication device according to claim 1, wherein the down-converted signal comprises an intermediate frequency (IF) signal

11. The DSSS communication device according to claim 1, further comprising:

an RF source for generating an RF transmitter carrier signal; and

a DSSS modulator that modulates a message to be transmitted onto the transmitter carrier signal using at least one known DSSS code.

12. The DSSS communication device according to claim 11, wherein the RF source comprises an oscillator that generates the RF transmitter carrier signal without use of a piezoelectric element.

13. The DSSS communication device according to claim 1, wherein the differential detector includes a processor that receives the down-converted signal and produces output chips therefrom which are a function of a plurality of successive chips of the received DSSS signal.

14. The DSSS communication device according to claim 13, wherein the correlator correlates output chips at the output of the processor to at least one DSSS code that has been derived from the received DSSS signal.

15. A Direct Sequence Spread Spectrum (DSSS) communication device, comprising:

an RF source that generates a transmitter carrier signal, wherein the RF source comprises an oscillator that generates the RF transmitter carrier signal without use of a piezoelectric element; and

a DSSS modulator which modulates a message to be transmitted onto the transmitter carrier signal using at least one known DSSS code word.

16. The DSSS communication device according to claim 15, wherein the frequency generator comprises one of a LC type oscillator, an RC type oscillator, a relaxation oscillator, a ring oscillator and a voltage controlled oscillator.

17. The DSSS communication device according to claim 15, further comprising means for initial adjustment of the frequency of the RF transmitter carrier signal.

18. The DSSS communication device according to claim 15, further comprising a compensation circuit that compensates the RF source against changes in temperature or operating voltage.

19. A direct sequence spread spectrum (DSSS) communication method, comprising:

generating a local oscillator signal without use of a piezoelectric crystal;

mixing the local oscillator signal with a received DSSS signal to produce a down-converted signal, wherein the received DSSS signal is encoded using a first set of DSSS codes;

differentially decoding the down-converted signal to create a differentially detected signal; and

correlating the differentially detected signal with a second set of DSSS codes.

20. The DSSS communication method according to claim 19, wherein the second set of DSSS codes is time-shifted from the first set of DSSS codes by an integer number of chip periods.

21. The DSSS communication method according to claim 19, wherein the differentially detected signal comprises output chips which are a function of a plurality of successive chips of the received DSSS signal.

22. The DSSS communication method according to claim 19, wherein the local oscillator signal is generated using one of an LC type oscillator, an RC type oscillator, a relaxation oscillator, a ring oscillator and a voltage controlled oscillator.

23. The DSSS communication method according to claim 19, further comprising:

generating an RF transmitter carrier signal; and

modulating a message to be transmitted onto the transmitter carrier signal using at least one known DSSS code.

24. The DSSS communication method according to claim 23, wherein the RF transmitter carrier signal is generated without use of a piezoelectric element.