Timing reproducer and demodulator comprising this

• US 6,650,718 B1
• Filed: 08/28/2001
• Issued: 11/18/2003
• Est. Priority Date: 12/28/1999
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Okubo, Seiji, Fujimura, Akinori, Kojima, Toshiharu
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US09/926,091
• Time in Patent Office: 812 Days
• Field of Search: 375/371, 375/355, 375/373, 327/144, 327/156, 327/162, 327/163, 327/147
• US Class Current: 375/355
• CPC Class Codes: H04L 2027/0028 at passband only
• CPC Class Codes: H04L 2027/0036 using a recovered symbol clock
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 2027/0095 in a preamble or similar structure
• CPC Class Codes: H04L 27/2273 associated with quadrature demodulation, e.g. Costas loop
• CPC Class Codes: H04L 7/0029 interpolation of received data signal
• CPC Class Codes: H04L 7/0334 Processing of samples having at least three levels, e.g. soft decisions
• CPC Class Codes: H04L 7/041 using special codes as synchronising signal

Abstract

A timing recovery device and demodulator. An adding device adds together an in-phase component and a quadrature component of a base band signal. A subtracting device subtracts the in-phase component and the quadrature component of the base band signal from each other. Then, the correlation between the added signal and a ½ symbol frequency component generated at the receiver side and the correlation between the subtracted value and the ½ symbol frequency component are calculated. A vector selector compares the added value correlation signal and the subtracted value correlation signal, and selects the larger one of the correlation signals. A timing phase difference calculator then calculates a timing phase difference, using the vector angle indicated by the selected correlation signal.

Claims

1. A timing recovery device characterized by the provision of:

adding means for adding together an in-phase component of a base band signal and a quadrature component of the base band signal and for outputting a signal after the addition as an added signal;

subtracting means for subtracting the in-phase component of the base band signal and the quadrature component of the base band signal from each other and for outputting a signal after the subtraction as a subtracted signal;

added value correlation calculating means for calculating the correlation between said added signal and a ½

symbol frequency component generated at the receiver side, and for outputting the calculated correlation value as an added correlation signal;

subtracted value correlation calculating means for calculating the correlation between said subtracted signal and said ½

symbol frequency component, and for outputting the calculated correlation value as a subtracted correlation signal;

vector selecting means for comparing the magnitude of said added correlation signal and the magnitude of said subtracted correlation signal, for selecting the correlation signal of the larger magnitude, and for outputting the selected correlation signal as a selected correlation signal; and

timing phase difference calculating means for calculating a timing phase difference through utilization of the vector angle indicated by said selected correlation signal.

2. The timing recovery device as claimed in claim 1, characterized in that said timing phase difference calculating means calculates the vector angle and the vector length indicated by said selected correlation signal, and when said vector length is large, decides that said preamble signal is detected, and calculates the timing phase difference through utilization of the vector angle indicated by said selected correlation signal at that time.

3. The timing recovery device as claimed in claim 1, characterized by further provision of recovered sample clock oscillating means for outputting a recovered sample clock for sampling said base band signal and a recovered ½

symbol frequency component, and for effecting phase control to reduce a timing error down to “

0”

through utilization of said timing phase difference information.

4. The timing recovery device as claimed in claim 3, characterized in that:

said added value correlation calculating means, said subtracted value correlation calculating means, said vector selecting means, said timing phase difference calculating means and said recovered sample clock oscillating means use, for their processing, a base band signal sampled by said recovered sample clock; and

said added value correlation calculating means and said subtracted value correlation calculating means render said ½

symbol frequency component to said recovered ½

symbol frequency component.

5. A demodulator is characterized by the provision of:

the timing recovery device as claimed in claim 4;

an antenna for receiving a radio signal;

frequency converting means for frequency converting said radio signal received by said antenna to a base band signal;

A/D converting means for sampling said base band signal converted by said frequency converting means at a rate twice higher than a symbol rate through the use of said recovered sample clock for conversion to a digital base band signal for application to said timing recovery device; and

data decision means for extracting Nyquist point data from said digital base band signal through the use of a recovered symbol clock output from said timing recovery device, for making a decision on said extracted Nyquist point data and for outputting said decided Nyquist point data as demodulated data.

6. The timing recovery device as claimed in claim 3, characterized by further provision of:

phase detecting means for detecting the timing phase through the use of said base band signal sampled by said recovered sample clock and for outputting the detected signal as a phase detected signal; and

phase detected signal averaging means for averaging said phase detected signal and for outputting the average as a phase lead/lag signal;

wherein said recovered sample clock oscillating means uses both of said timing phase difference information and said phase lead/lag signal to effect phase control to reduce the timing error down to “

0”

.

7. A demodulator is characterized by the provision of:

the timing recovery device as claimed in claim 6;

an antenna for receiving a radio signal;

frequency converting means for frequency converting said radio signal received by said antenna to a base band signal;

A/D converting means for sampling said base band signal converted by said frequency converting means at a rate twice higher than a symbol rate through the use of said recovered sample clock for conversion to a digital base band signal for application to said timing recovery device; and

data decision means for extracting Nyquist point data from said digital base band signal through the use of a recovered symbol clock output from said timing recovery device, for making a decision on said extracted Nyquist point data and for outputting said decided Nyquist point data as demodulated data.

8. A demodulator is characterized by the provision of:

the timing recovery device as claimed in claim 3;

an antenna for receiving a radio signal;

frequency converting means for frequency converting said radio signal received by said antenna to a base band signal;

A/D converting means for sampling said base band signal converted by said frequency converting means at a rate twice higher than a symbol rate through the use of said recovered sample clock for conversion to a digital base band signal for application to said timing recovery device; and

data decision means for extracting Nyquist point data from said digital base band signal through the use of a recovered symbol clock output from said timing recovery device, for making a decision on said extracted Nyquist point data and for outputting said decided Nyquist point data as demodulated data.

9. The timing recovery device as claimed in claim 1, characterized by further provision of asynchronous sample clock oscillating means for outputting an asynchronous sample clock for sampling said base band signal and an asynchronous ½

symbol frequency component.

10. The timing recovery device as claimed in claim 9, characterized in that:

said added value correlation calculating means, said subtracted value correlation calculating means, said vector selecting means, said timing phase difference calculating means and said asynchronous sample clock oscillating means use, for their processing, the base band signal sampled by said asynchronous sample clock; and

the added value correlation calculating means; and

said added value correlation calculating means and said subtracted value correlation calculating means render said ½

symbol frequency component to said asynchronous ½

symbol frequency component.

11. A demodulator characterized by the provision of:

the timing recovery device as claimed in claim 10;

an antenna for receiving a radio signal;

frequency converting means for frequency converting said radio signal received by said antenna to a base band signal;

A/D converting means for sampling the base band signal converted by said frequency converting means at a rate twice higher than a symbol rate through the use of said asynchronous sample clock for conversion to a digital base band signal for application to said timing recovery device;

data interpolating means for interpolating said digital base band signal sampled by the asynchronous sample clock output from said timing recovery device, and for outputting the interpolated data as an interpolated base band signal; and

data decision means for extracting a Nyquist point of the interpolated digital base band signal output from said data interpolating means based on said timing phase difference, for making a decision on said extracted Nyquist point data and for outputting the decided Nyquist point data as demodulated data.

12. A demodulator characterized by the provision of:

the timing recovery device as claimed in claim 9;

an antenna for receiving a radio signal;

frequency converting means for frequency converting said radio signal received by said antenna to a base band signal;

A/D converting means for sampling the base band signal converted by said frequency converting means at a rate twice higher than a symbol rate through the use of said asynchronous sample clock for conversion to a digital base band signal for application to said timing recovery device;

data interpolating means for interpolating said digital base band signal sampled by the asynchronous sample clock output from said timing recovery device, and for outputting the interpolated data as an interpolated base band signal; and

data decision means for extracting a Nyquist point of the interpolated digital base band signal output from said data interpolating means based on said timing phase difference, for making a decision on said extracted Nyquist point data and for outputting the decided Nyquist point data as demodulated data.

13. A timing recovery device characterized by the provision of:

adding means for adding together an in-phase component of a base band signal and a quadrature component of the base band signal and for outputting a signal after the addition as an added signal;

subtracting means for subtracting the in-phase component of the base band signal and the quadrature component of the base band signal from each other and for outputting a signal after the subtraction as a subtracted signal;

added value correlation calculating means for calculating the correlation between said added signal and a ½

symbol frequency component generated at the receiver side, and for outputting the calculated correlation value as an added correlation signal;

subtracted value correlation calculating means for calculating the correlation between said subtracted signal and said ½

symbol frequency component, and for outputting the calculated correlation value as a subtracted correlation signal;

vector selecting means for comparing the magnitude of said added correlation signal and the magnitude of said subtracted correlation signal, for selecting the correlation signal of the larger magnitude, and for outputting the selected correlation signal as a selected correlation signal;

weighting means for weighting said selected correlation signal in accordance with the magnitude of the vector length indicated by said selected correlation signal, and for outputting said weighted selected correlation signal as a weighted correlation signal;

weighted signal averaging means for averaging said weighted correlation signal and for outputting the average as a weighted average correlation signal; and

timing phase difference calculating means for calculating a timing phase difference through utilization of the vector angle indicated by said averaged correlation signal.

14. The timing recovery device as claimed in claim 13, characterized in that said timing phase difference calculating means calculates the vector angle and vector length indicated by said weighted average correlation signal, and when said vector length is large, detects that said preamble signal is detected, and calculates the timing difference through utilization of the vector angle indicated by said selected correlation signal at that time.

15. The timing recovery device as claimed in claim 13, characterized by further provision of recovered sample clock oscillating means for outputting a recovered sample clock for sampling said base band signal and a recovered ½

symbol frequency component, and for effecting phase control to reduce a timing error down to “

0”

through utilization of said timing phase difference information.

16. The timing recovery device as claimed in claim 15, characterized in that:

said added value correlation calculating means, said subtracted value correlation calculating means, said vector selecting means, said weighting means, said weighted signal averaging means, said timing phase difference calculating means and said recovered sample clock oscillating means use, for their processing, a base band signal sampled by said recovered sample clock; and

said added value correlation calculating means and said subtracted value correlation calculating means render said, ½

symbol frequency component to said recovered ½

symbol frequency component.

17. A demodulator is characterized by the provision of:

the timing recovery device as claimed in claim 16;

an antenna for receiving a radio signal;

frequency converting means for frequency converting said radio signal received by said antenna to a base band signal;

A/D converting means for sampling said base band signal converted by said frequency converting means at a rate twice higher than a symbol rate through the use of said recovered sample clock for conversion to a digital base band signal for application to said timing recovery device; and

data decision means for extracting Nyquist point data from said digital base band signal through the use of a recovered symbol clock output from said timing recovery device, for making a decision on said extracted Nyquist point data and for outputting said decided Nyquist point data as demodulated data.

18. The timing recovery device as claimed in claim 15, characterized in that:

said weighted signal averaging means comprises a first low-pass filter of a small time constant and a second low-pass filter of a large time constant which are supplied with said weighted correlation signal and at the time of phase control, sets “

0”

in a quadrature component and (in-phase component²+quadrature component²)^½

prior to the phase control in an in-phase component in each of said first and second low-pass filters;

said timing phase difference calculating means calculates a first vector angle and a first vector length indicated by said first low-pass filter, and when said vector length is large, decides that said preamble signal is detected, calculates an initial timing phase difference through the use of said first vector angle, calculates a second vector angle and a second vector length indicated by said second low-pass filter, and when said second vector length is large after said first phase control, periodically calculates a timing phase difference for phase following use through the use of said second vector angle; and

said recovered sample clock oscillating means uses both of said initial timing phase difference and said phase-following timing phase difference as said timing phase difference information to effect phase control to reduce the timing error down to “

0”

.

19. A demodulator is characterized by the provision of:

the timing recovery device as claimed in claim 18;

an antenna for receiving a radio signal;

frequency converting means for frequency converting said radio signal received by said antenna to a base band signal;

A/D converting means for sampling said base band signal converted by said frequency converting means at a rate twice higher than a symbol rate through the use of said recovered sample clock for conversion to a digital base band signal for application to said timing recovery device; and

data decision means for extracting Nyquist point data from said digital base band signal through the use of a recovered symbol clock output from said timing recovery device, for making a decision on said extracted Nyquist point data and for outputting said decided Nyquist point data as demodulated data.

20. A demodulator is characterized by the provision of:

the timing recovery device as claimed in claim 15;

an antenna for receiving a radio signal;

frequency converting means for frequency converting said radio signal received by said antenna to a base band signal;

A/D converting means for sampling said base band signal converted by said frequency converting means at a rate twice higher than a symbol rate through the use of said recovered sample clock for conversion to a digital base band signal for application to said timing recovery device; and

data decision means for extracting Nyquist point data from said digital base band signal through the use of a recovered symbol clock output from said timing recovery device, for making a decision on said extracted Nyquist point data and for outputting said decided Nyquist point data as demodulated data.

21. The timing recovery device as claimed in claim 13, characterized by further provision of asynchronous sample clock oscillating means for outputting an asynchronous sample clock for sampling said base band signal and an asynchronous ½

symbol frequency component.

22. The timing recovery device as claimed in claim 21, characterized in that:

said added value correlation calculating means, said subtracted value correlation calculating means, said vector selecting means, said weighting means, said weighted signal averaging means, said timing phase difference calculating means and said asynchronous sample clock oscillating means use, for their processing, a base band signal sampled by said asynchronous sample clock; and

said added value correlation calculating means and said subtracted value correlation calculating means render said ½

symbol frequency component to said asynchronous ½

symbol frequency component.

23. The timing recovery device as claimed in claim 21, characterized in that:

said weighted signal averaging means further comprises a first low-pass filter of a small time constant and a second low-pass filter of a large time constant which are supplied with said weighted correlation signal; and

said timing phase difference calculating means calculates a first vector angle and a first vector length indicated by said first low-pass filter, and when said first vector length is large, decides that said preamble signal is detected, calculates an initial timing phase difference through the use of said first vector angle, calculates a second vector angle and a second vector length indicated by said second low-pass filter, and when said second vector length is large after said first phase control, periodically calculates a timing phase difference for phase following use through the use of said second vector angle.

24. A demodulator characterized by the provision of:

the timing recovery device as claimed in claim 15;

an antenna for receiving a radio signal;

frequency converting means for frequency converting the radio signal received by said antenna to a base band signal;

A/D converting means for sampling the base band signal converted by said frequency converting means at a rate twice higher than a symbol rate through the use of an asynchronous sample clock for conversion to a digital base band signal for application to said timing recovery device;

data interpolating means for interpolating said digital base band signal sampled by the asynchronous sample clock output from the timing recovery device, and for outputting the interpolated data as an interpolated base band signal; and

data decision means for extracting a Nyquist point of the interpolated digital base band signal output from said data interpolating means based on both of said initial timing phase difference and said timing phase difference for phase following use, for making a decision on said extracted Nyquist point data and for outputting the decided Nyquist point data as demodulated data.