System and method for despreading in a spread spectrum matched filter

• US 20050025222A1
• Filed: 06/16/2004
• Published: 02/03/2005
• Est. Priority Date: 09/01/1998
• Status: Active Grant

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Inventors: Underbrink, Paul A., Gronemyer, Steven A.
• Granted Patent: US 7,852,905 B2
• Time in Patent Office: Days
• US Class Current: 375/141
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04L 2027/0028 at passband only
• CPC Class Codes: H04L 2027/0046 Open loops

Abstract

Implementation of an improved matched filter system for despreading a PN code from a spread spectrum signal utilizes a matched filter system that may be broadly conceptualized as a system that optimizes the number of multipliers and adders utilized by the system in despreading a PN code from a spread spectrum signal. This lowers the power consumption of the improved matched filter system and increases the speed at which the system despreads the PN code from the spread spectrum signal.

Claims

1. A method for measuring time related to satellite data messages for use with a satellite positioning system (SPS), the method comprising:

receiving in a mobile SPS receiver at least a portion of a satellite data message;

determining a first record of the at least a portion of the satellite data message by despreading a PN code from the satellite data message, wherein the satellite data message comprises a plurality of signal samples, each signal sample having an in-phase portion and a quadrature-phase portion, and wherein the PN code comprises a plurality of chips, the despreading step comprising;

selecting one of the in-phase portion and the quadrature-phase portion; and

multiplying the selected portion of one of the plurality of signal samples with one of the plurality of PN code chips; and

transmitting from the mobile SPS receiver the first record to a remote basestation for the purpose of determining a time indicating when the first record was received at the mobile SPS receiver.

2. A method for measuring time related to satellite data messages for use with a satellite positioning system (SPS), the method comprising:

receiving in a mobile SPS receiver at least a portion of a satellite data message;

determining a first record of the at least a portion of the satellite data message by despreading a PN code from the satellite data message, wherein the satellite data message comprises a plurality of signal sample pairs, each pair comprising an even signal sample and an odd signal sample, each signal sample having an in-phase portion and a quadrature-phase portion, and wherein the PN code comprises a plurality of chips, the despreading step comprising;

selecting one of the in-phase portion and the quadrature-phase portion;

selecting one of the even sample and the odd sample; and

multiplying the selected portion of the selected sample of one of the plurality of signal sample pairs with one of the plurality of PN code chips; and

transmitting from the mobile SPS receiver the first record to a remote basestation for the purpose of determining a time indicating when the first record was received at the mobile SPS receiver.

3. A satellite positioning system (SPS) receiver comprising:

an antenna for receiving SPS signals;

a demodulator coupled to the antenna, the demodulator removing a PN code from the SPS signals, wherein each SPS signal comprises a plurality of signal samples, each signal sample having an in-phase portion and a quadrature-phase portion and wherein the PN code comprises a plurality of chips, the demodulator comprising;

a switch for selecting one of the in-phase portion and the quadrature-phase portion; and

a first multiplier coupled to the switch for multiplying the selected portion of one of the plurality of signal samples with one of the plurality of PN code chips;

a processor coupled to the demodulator, the processor determining a first record of at least a portion of a satellite data message received from the demodulator; and

a transmitter coupled to the processor, the transmitter transmitting the first record to a remote basestation for the purpose of determining a time indicating when the first record was received at the SPS receiver.

4. A satellite positioning system (SPS) receiver comprising:

an antenna for receiving SPS signals;

a demodulator coupled to the antenna, the demodulator removing a PN code from the SPS signals, wherein each SPS signal comprises a plurality of signal sample pairs, each pair comprising an even signal sample and an odd signal sample, each signal sample having an in-phase portion and a quadrature-phase portion, and wherein the PN code comprises a plurality of chips, the demodulator comprising;

a first switch for selecting one of the in-phase portion and the quadrature-phase portion;

a second switch coupled to the first switch for selecting one of the even sample and the odd sample; and

a first multiplier coupled to the second switch for multiplying the selected portion of the selected sample of one of the plurality of signal sample pairs with one of the plurality of PN code chips;

a processor coupled to the demodulator, the processor determining a first record of at least a portion of a satellite data message received from the demodulator; and

a transmitter coupled to the processor, the transmitter transmitting the first record to a remote basestation for the purpose of determining a time indicating when the first record was received at the SPS receiver.

5. A satellite positioning system (SPS) receiver comprising:

a SPS antenna for receiving SPS signals;

a digitizer coupled to the SPS antenna;

a digital memory coupled to the digitizer, the digital memory storing a digital representation of the SPS signals;

a digital processor coupled to the digital memory, the digital processor processing the SPS signals and determining at least one pseudorange from the SPS signals, the digital processor removing a PN code from the SPS signals to provide a first record of at least a portion of a satellite data message in the SPS signals, wherein each SPS signal comprises a plurality of signal samples, each signal sample having an in-phase portion and a quadrature-phase portion, and wherein the PN code comprises a plurality of chips, the digital processor comprising;

a switch for selecting one of the in-phase portion and the quadrature-phase portion; and

a first multiplier coupled to the switch for multiplying the selected portion of one of the plurality of signal samples with one of the plurality of PN code chips; and

a transmitter coupled to the digital processor, the transmitter transmitting the first record to a remote basestation.

6. A satellite positioning system (SPS) receiver comprising:

a SPS antenna for receiving SPS signals;

a digitizer coupled to the SPS antenna;

a digital memory coupled to the digitizer, the digital memory storing a digital representation of the SPS signals;

a digital processor coupled to the digital memory, the digital processor processing the SPS signals and determining at least one pseudorange from the SPS signals, the digital processor removing a PN code from the SPS signals to provide a first record of at least a portion of a satellite data message in the SPS signals, wherein each SPS signal comprises a plurality of signal sample pairs, each pair comprising an even signal sample and an odd signal sample, each signal sample having an in-phase portion and a quadrature-phase portion, and wherein the PN code comprises a plurality of chips, the digital processor comprising;

a first switch for selecting one of the in-phase portion and the quadrature-phase portion;

a second switch coupled to the first switch for selecting one of the even sample and the odd sample; and

a first multiplier coupled to the second switch for multiplying the selected portion of the selected sample of one of the plurality of signal sample pairs with one of the plurality of PN code chips; and

a transmitter coupled to the digital processor, the transmitter transmitting the first record to a remote basestation.

7. A system of a mobile satellite positioning system (SPS) receiver and a basestation remotely positioned relative to the mobile SPS receiver, the system comprising:

the mobile SPS receiver comprising;

an antenna for receiving SPS signals;

a processor coupled to the antenna, the processor despreading a PN code from the SPS signals to determine a first record of at least a portion of a satellite data message in the SPS signals, wherein each SPS signal comprises a plurality of signal samples, each signal sample having an in-phase portion and a quadrature-phase portion, and wherein the PN code comprises a plurality of chips, the processor comprising;

a switch for selecting one of the in-phase portion and the quadrature-phase portion; and

a first multiplier coupled to the switch for multiplying the selected portion of one of the plurality of signal samples with one of the plurality of PN code chips;

a transmitter coupled to the processor, the transmitter transmitting the first record to the basestation;

the basestation comprising;

a receiver for receiving the first record;

a data processor coupled to the receiver, the data processor performing a comparison of the first record with a second record of the satellite data message, wherein the first record and the second record overlap at least partially in time, the data processor determining a time from the comparison, the time indicating when the first record was received at the mobile SPS receiver.

8. A system of a mobile satellite positioning system (SPS) receiver and a basestation remotely positioned relative to the mobile SPS receiver, the system comprising:

the mobile SPS receiver comprising;

an antenna for receiving SPS signals;

a processor coupled to the antenna, the processor despreading a PN code from the SPS signals to determine a first record of at least a portion of a satellite data message in the SPS signals, wherein each SPS signal comprises a plurality of signal sample pairs, each pair comprising an even signal sample and an odd signal sample, each signal sample having an in-phase portion and a quadrature-phase portion, and wherein the PN code comprises a plurality of chips, the processor comprising;

a first switch for selecting one of the in-phase portion and the quadrature-phase portion;

a second switch coupled to the first switch for selecting one of the even sample and the odd sample; and

a first multiplier coupled to the second switch for multiplying the selected portion of the selected sample of one of the plurality of signal sample pairs with one of the plurality of PN code chips

a transmitter coupled to the processor, the transmitter transmitting the first record to the basestation;

the basestation comprising;

a receiver for receiving the first record;

a data processor coupled to the receiver, the data processor performing a comparison of the first record with a second record of the satellite data message, wherein the first record and the second record overlap at least partially in time, the data processor determining a time from the comparison, the time indicating when the first record was received at the mobile SPS receiver.

9. A mobile satellite positioning system (SPS) receiver comprising:

an antenna for receiving SPS signals;

a demodulator coupled to the antenna, the demodulator removing a PN code from the SPS signals, wherein each SPS signal comprises a plurality of signal samples, each signal sample having an in-phase portion and a quadrature-phase portion and wherein the PN code comprises a plurality of chips, the demodulator comprising;

a switch for selecting one of the in-phase portion and the quadrature-phase portion; and

a first multiplier coupled to the switch for multiplying the selected portion of one of the plurality of signal samples with one of the plurality of PN code chips;

a processor coupled to the demodulator, the processor determining a first record of at least a portion of a satellite data message received from the demodulator;

a communication antenna;

a communication receiver coupled to the communication antenna and to the processor, the communication receiver receiving a second record of the satellite data message, wherein the first record and the second record overlap at least partially in time, the processor comparing the first record and the second record and determining a time indicating when the first record was received.

10. A mobile satellite positioning system (SPS) receiver comprising:

an antenna for receiving SPS signals;

a demodulator coupled to the antenna, the demodulator removing a PN code from the SPS signals, wherein each SPS signal comprises a plurality of signal sample pairs, each pair comprising an even signal sample and an odd signal sample, each signal sample having an in-phase portion and a quadrature-phase portion, and wherein the PN code comprises a plurality of chips, the demodulator comprising;

a first switch for selecting one of the in-phase portion and the quadrature-phase portion;

a second switch coupled to the first switch for selecting one of the even sample and the odd sample; and

a first multiplier coupled to the second switch for multiplying the selected portion of the selected sample of one of the plurality of signal sample pairs with one of the plurality of PN code chips;

a processor coupled to the demodulator, the processor determining a first record of at least a portion of a satellite data message received from the demodulator;

a communication antenna;

a communication receiver coupled to the communication antenna and to the processor, the communication receiver receiving a second record of the satellite data message, wherein the first record and the second record overlap at least partially in time, the processor comparing the first record and the second record and determining a time indicating when the first record was received.

11. A method of controlling a communication link and processing data representative of GPS signals from at least one satellite in a GPS receiver, the method comprising:

processing the data representative of GPS signals from at least one satellite in a processing unit, including performing a correlation function to determine a pseudorange based on the data representative of GPS signals, wherein the data representative of GPS signals comprises a plurality of signal samples, each signal sample having an in-phase portion and a quadrature-phase portion, the performing a correlation function step comprising;

selecting one of the in-phase portion and the quadrature-phase portion; and

multiplying the selected portion of one of the plurality of signal samples with one of a plurality of PN code chips;

controlling communication signals through the communication link by using the processing unit to perform the controlling and wherein the processing unit performs demodulation of communication signals sent to the GPS receiver.

12. A method of controlling a communication link and processing data representative of GPS signals from at least one satellite in a GPS receiver, the method comprising:

processing the data representative of GPS signals from at least one satellite in a processing unit, including performing a correlation function to determine a pseudorange based on the data representative of GPS signals, wherein the data representative of GPS signals comprises a plurality of signal sample pairs, each pair comprising an even signal sample and an odd signal sample, each signal sample having an in-phase portion and a quadrature-phase portion, the performing a correlation function step comprising;

selecting one of the in-phase portion and the quadrature-phase portion;

selecting one of the even sample and the odd sample; and

multiplying the selected portion of the selected sample of one of the plurality of signal sample pairs with one of a plurality of PN code chips; and

controlling communication signals through the communication link by using the processing unit to perform the controlling and wherein the processing unit performs demodulation of communication signals sent to the GPS receiver.

13. A GPS receiver comprising:

a GPS antenna for receiving data representative of GPS signals from at least one satellite;

a digital processor coupled to the GPS antenna, the digital processor processing the data representative of GPS signals from at least one satellite, including performing a matched filtering operation to determine a pseudorange based on the data representative of GPS signals, wherein the data representative of GPS signals comprises a plurality of signal samples, each signal sample having an in-phase portion and a quadrature-phase portion, the matched filter operation comprising;

a switch for selecting one of the in-phase portion and the quadrature-phase portion; and

a first multiplier coupled to the switch for multiplying the selected portion of one of the plurality of signal samples with one of a plurality of PN code chips;

the digital processor also processing communication signals received through a communication link, the processing of communication signals comprising demodulation of communication signals sent to the GPS receiver.

14. A GPS receiver comprising:

a GPS antenna for receiving data representative of GPS signals from at least one satellite;

a digital processor coupled to the GPS antenna, the digital processor processing the data representative of GPS signals from at least one satellite, including performing a matched filtering operation to determine a pseudorange based on the data representative of GPS signals, wherein the data representative of GPS signals comprises a plurality of signal sample pairs, each pair comprising an even signal sample and an odd signal sample, each signal sample having an in-phase portion and a quadrature-phase portion, the matched filter operation comprising;

a first switch for selecting one of the in-phase portion and the quadrature-phase portion;

a second switch coupled to the first switch for selecting one of the even sample and the odd sample; and

a first multiplier coupled to the second switch for multiplying the selected portion of the selected sample of one of the plurality of signal sample pairs with one of the plurality of PN code chips;

the digital processor also processing communication signals received through a communication link, the processing of communication signals comprising demodulation of communication signals sent to the GPS receiver.