PSEUDO TONE-BASED SYMBOL TIMING RECOVERY AND CARRIER TRACKING LOOP DETECTORS FOR VESTIGIAL SIDEBAND RECEIVERS

• US 20100283903A1
• Filed: 01/14/2008
• Published: 11/11/2010
• Est. Priority Date: 01/14/2008
• Status: Active Grant

• Current Assignee: InterDigital Madison Patent Holdings (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Belotserkovsky, Maxim
• Granted Patent: US 8,559,563 B2
• Time in Patent Office: Days
• US Class Current: 348/725
• CPC Class Codes: H04L 27/066 Carrier recovery circuits H04L27/2271 takes precedence
• CPC Class Codes: H04L 27/3863 Compensation for quadrature error in the received signal
• CPC Class Codes: H04L 7/0029 interpolation of received data signal
• CPC Class Codes: H04L 7/0278 Band edge detection
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence

Abstract

A receiver is an ATSC (Advanced Television Systems Committee)-receiver and comprises a pseudo-tone based carrier tracking loop and symbol timing recovery loop comprising one, or more, detectors for providing at least two pseudo tone (PST) signals. The first PST signal drives the carrier tracking loop and the second PST signal drives the symbol timing recovery loop. The detector provides the first PST signal such that the first PST signal is determined as a function of carrier offset excluding symbol-timing offset; and provides the second PST signal such that the second PST signal is determined as a function of symbol timing offset excluding carrier offset.

Claims

1. Apparatus for use in a receiver, the apparatus comprising:

a carrier tracking loop for tracking a carrier in a received signal; and

a symbol timing recovery loop for tracking symbol timing in the received signal;

wherein the carrier tracking loop and the symbol timing recovery loop are driven as a function of pseudo-tones developed from both edges of a staggered quadrature amplitude modulated version of the received signal.

2. The apparatus of claim 1,

wherein the pseudo-tones are provided by a detector that filters a lower edge and an upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a first pseudo tone for use in the carrier tracking loop and a second pseudo tone for use in the symbol timing recovery loop such that the first pseudo tone is determined as a function of carrier offset excluding symbol-timing offset;

and the second pseudo tone is determined as a function of symbol timing offset excluding carrier offset.

3. The apparatus of claim 2, the detector further comprising:

an upper filter for filtering the upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered upper signal;

a lower filter for filtering the lower edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered lower signal;

a squarer for squaring the filtered upper signal for providing a squared upper signal;

a squarer for squaring the filtered lower signal for providing a squared lower signal;

a multiplier for providing the first pseudo tone representing a product of the squared upper signal and the squared lower signal; and

a multiplier for providing the second pseudo tone representing a product of the squared upper signal and a conjugate of the squared lower signal.

4. The apparatus of claim 3, the detector further comprising:

additional filters for further filtering the squared lower signal and the squared upper signal.

5. The apparatus of claim 1, the carrier track loop further comprising

a detector for filtering a lower edge and an upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a pseudo tone for use in driving the carrier tracking loop.

6. The apparatus of claim 5, wherein the detector further comprises:

an upper filter for filtering the upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered upper signal;

a lower filter for filtering the lower edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered lower signal;

a squarer for squaring the filtered upper signal for providing a squared upper signal;

a squarer for squaring the filtered lower signal for providing a squared lower signal;

a multiplier for providing the pseudo tone representing a product of the squared upper signal and the squared lower signal.

7. The apparatus of claim 6, the detector further comprising:

additional filters for further filtering the squared lower signal and the squared upper signal.

8. The apparatus of claim 1, the symbol timing recovery loop further comprising

a detector for filtering a lower edge and an upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a pseudo tone for use in driving the symbol recovery tracking loop.

9. The apparatus of claim 8, wherein the detector further comprises:

an upper filter for filtering the upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered upper signal;

an lower filter for filtering the lower edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered lower signal;

a squarer for squaring the filtered upper signal for providing a squared upper signal;

a squarer for squaring the filtered lower signal for providing a squared lower signal; and

a multiplier for providing the second pseudo tone representing a product of the squared upper signal and a conjugate of the squared lower signal.

10. The apparatus of claim 9, the detector further comprising:

additional filters for further filtering the squared lower signal and the squared upper signal.

11. The apparatus of claim 1, wherein the received signal is an ATSC (Advanced Television Systems Committee) VSB (Vestigial Sideband) modulated signal.

12. A method for use in a receiver, the method comprising:

tracking a carrier in a received signal;

tracking symbol timing in the received signal; and

wherein the carrier tracking and the symbol timing tracking are driven as a function of pseudo-tones developed from both edges of a staggered quadrature amplitude modulated version of the received signal.

13. The method of claim 12, wherein the pseudo-tones are provided by:

filtering a lower edge and an upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a first pseudo tone for use in the carrier tracking loop and a second pseudo tone for use in the symbol timing recovery loop such that the first pseudo tone is determined as a function of carrier offset excluding symbol-timing offset; and

the second pseudo tone is determined as a function of symbol timing offset excluding carrier offset.

14. The method of claim 13, the filtering step comprising:

filtering the upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered upper signal;

filtering the lower edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered lower signal;

squaring the filtered upper signal for providing a squared upper signal;

squaring the filtered lower signal for providing a squared lower signal;

providing the first pseudo tone representing a product of the squared upper signal and the squared lower signal; and

providing the second pseudo tone representing a product of the squared upper signal and a conjugate of the squared lower signal.

15. The method of claim 14 further comprising:

further filtering the squared lower signal and the squared upper signal before providing the pseudo tones.

16. The method of claim 12, the carrier tracking step comprising

filtering a lower edge and an upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a pseudo tone for use in driving the carrier tracking loop.

17. The method of claim 16, the filtering step comprising:

filtering the upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered upper signal;

filtering the lower edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered lower signal;

squaring the filtered upper signal for providing a squared upper signal;

squaring the filtered lower signal for providing a squared lower signal;

providing the pseudo tone representing a product of the squared upper signal and the squared lower signal.

18. The method of claim 17, further comprising:

further filtering the squared lower signal and the squared upper signal before providing the pseudo tone.

19. The method of claim 12, the symbol timing recovery step further comprising

filtering a lower edge and an upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a pseudo tone for use in driving the symbol recovery tracking loop.

20. The method of claim 19, filtering step comprising:

filtering the upper edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered upper signal;

filtering the lower edge of the staggered quadrature amplitude modulated version of the received signal for providing a filtered lower signal;

squaring the filtered upper signal for providing a squared upper signal;

squaring the filtered lower signal for providing a squared lower signal; and

providing the second pseudo tone representing a product of the squared upper signal and a conjugate of the squared lower signal.

21. The method of claim 20, further comprising:

further filtering the squared lower signal and the squared upper signal before providing the pseudo tone.

22. The apparatus of claim 12, wherein the received signal is an ATSC (Advanced Television Systems Committee) VSB (Vestigial Sideband) modulation signal.