Receiver for producing phase corrected signals

• US 8,582,625 B2
• Filed: 08/24/2012
• Issued: 11/12/2013
• Est. Priority Date: 05/14/1998
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Ozluturk, Fatih M., Mesecher, David K., Jacques, Alexander M.
• Primary Examiner(s): Tran, Khai
• Application Number:
  US13/594,447
• Publication Number:
  US 20120320952A1
• Time in Patent Office: 445 Days
• Field of Search: 375/148, 375/130, 375/150, 375/152, 375/316, 375/342, 375/376, 370/230, 370/320, 370/330, 370/342, 370/411
• US Class Current: 375/148
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/70755 Setting of lock conditions, e.g. threshold
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method for receiving at least one of a plurality of channels in a communication signal includes receiving a spread spectrum communication signal, demodulating the spread spectrum communication signal using a rake receiver and a pseudo-noise pilot signal for a selected channel, despreading the demodulated signal of a selected channel, performing a QPSK hard decision in association with a complex conjugate of the despread signal to produce a correction signal, and mixing the correction signal to a rake receiver output to remove relative phase error without an absolute phase reference, to produce a corrected signal.

Claims

1. A method for receiving at least one of a plurality of channels in a communication signal, the method comprising:

receiving a spread spectrum communication signal;

demodulating the spread spectrum communication signal using a rake receiver and a pseudo-noise pilot signal for a selected channel;

despreading the demodulated signal of a selected channel;

performing a QPSK hard decision in association with a complex conjugate of the despread signal to produce a correction signal; and

mixing the correction signal to a rake receiver output to remove relative phase error without an absolute phase reference, producing a corrected signal.

2. The method of claim 1, further comprising:

using a phase-locked loop (PLL) to utilize a despread pilot signal of a pilot channel for producing a phase correction signal; and

applying the phase correction signal as feedback to the receiver to produce phase-corrected channel signals.

3. The method of claim 1, further comprising:

filtering the corrected signal by using a channel estimator and an adaptive multichannel filter to produce a filtered signal;

wherein the despreading includes despreading the filtered signal using the pseudo-noise signal generated for the selected channel to produce a despread channel signal of the selected channel, and

despreading the filtered signal using a pseudo-noise signal generator for the pilot channel to produce a despread pilot signal of the pilot channel.

4. The method of claim 3, wherein the despreading includes using a plurality of channel despreaders, each coupled to the adaptive matched filter output for despreading the filtered signal, each despreader using an associated pseudo-noise signal generator to produce a plurality of despread channel signals.

5. The method of claim 4 wherein the number of channel despreaders is three.

6. The method of claim 2 wherein the phase correction signal is at a chip level and is applied to the received spread spectrum communication signals.

7. The method of claim 4, wherein each of the plurality of channels is a complex, bi-phase modulated signal comprised of symbols including in-phase and quadrature components representing data, further comprising:

the hard decision processor comparing each despread channel signal symbol to one of four possible quadrature constellation points and assigning each of the symbols to a nearest constellation point, and

the complex conjugate processor derotating each of the symbols by determining a complex conjugate of each of the assigned points to produce the correction signal.

8. The method of claim 4, wherein the phase-locked loop uses a plurality of inputs corresponding with the plurality of channel despreaders.

9. The method of claim 4 wherein the phase correction signal is at a symbol level, further comprising applying the phase correction signal to the filter weighting signal and to the despread channel signals of the channel and pilot channel despreaders.

10. A mobile user receiver for receiving at least one of a plurality of channels in a communication signal, comprising:

a rake receiver for receiving and demodulating a spread spectrum communication signal using a pseudo-noise pilot signal for a selected channel;

a despreader for despreading the demodulated signal of a selected channel;

a hard decision processor for performing a QPSK hard decision in association with a complex conjugate processor for determining a complex conjugate of the despread signal to produce a correction signal; and

a mixer for mixing the correction signal to a rake receiver output to remove relative phase error without an absolute phase reference, producing a corrected signal.

11. The mobile user receiver of claim 10, further comprising:

using a phase-locked loop (PLL) to utilize a despread pilot signal of a pilot channel for producing a phase correction signal; and

applying the phase correction signal as feedback to the receiver to produce phase-corrected channel signals.

12. The mobile user receiver of claim 11 wherein the phase correction signal is at a chip level and is applied to the received spread spectrum communication signals.

13. The mobile user receiver of claim 10, further comprising:

a channel estimator for filtering the corrected signal and an adaptive multichannel filter to produce a filtered signal;

a channel despreader for despreading the filtered signal using the pseudo-noise signal generated for the selected channel to produce a despread channel signal of the selected channel, and

a pilot channel despreader for a pilot channel coupled to the adaptive matched filter output for despreading the filtered signal using a pseudo-noise signal generator for the pilot channel to produce a despread pilot signal of the pilot channel.

14. The mobile user receiver of claim 13, further comprising a plurality of channel despreaders, each coupled to the adaptive matched filter output for despreading the filtered signal, each despreader using an associated pseudo-noise signal generator to produce a plurality of despread channel signals.

15. The mobile user receiver of claim 14, wherein the number of channel despreaders is three.

16. The mobile user receiver of claim 14, wherein each of the plurality of channels is a complex, bi-phase modulated signal comprised of symbols including in-phase and quadrature components representing data, wherein:

the hard decision processor is further configured to compare each despread channel signal symbol to one of four possible quadrature constellation points and to assign each of the symbols to a nearest constellation point, and

the complex conjugate processor is further configured to derotate each of the symbols by determining a complex conjugate of each of the assigned points to produce the correction signal.

17. The mobile user receiver of claim 14, wherein the phase-locked loop comprises a plurality of inputs corresponding with the plurality of channel despreaders.

18. The mobile user receiver of claim 13, wherein the phase correction signal is at a symbol level, and is applied to the filter weighting signal and to the despread channel signals of the channel and pilot channel despreaders.