DECOUPLED DATA-AIDED CARRIER TRACKING LOOP AND SYMBOL TIMING RECOVERY LOOP

• US 20100283909A1
• 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 8,761,310 B2
• Time in Patent Office: Days
• US Class Current: 348/726
• CPC Class Codes: H04L 2025/03382 Single of vestigal sideband
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 27/3854 using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
• CPC Class Codes: H04L 7/0029 interpolation of received data signal
• CPC Class Codes: H04L 7/0062 detection of error based on data decision error, e.g. Mueller type detection
• CPC Class Codes: H04L 7/02 Speed or phase control by the received code signals, the signals containing no special synchronisation information H04L7/0075 takes precedence

Abstract

A receiver is an ATSC (Advanced Television Systems Committee)-receiver and comprises a staggered quadrature amplitude modulator for providing an staggered quadrature amplitude modulated (SQAM) signal from a received signal; an equalizer and a data-aided symbol timing recovery (STR) loop. The equalizer operates outside of the data-aided symbol timing recover loop.

Claims

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

a staggered quadrature amplitude modulator for providing a staggered quadrature amplitude modulated signal from a received signal;

an equalizer for equalizing a demodulated signal derived from the staggered quadrature amplitude modulated signal; and

a data-aided symbol timing recovery loop for tracking symbol timing in the staggered quadrature amplitude modulated signal, wherein the data-aided symbol timing recovery loop operates on the demodulated signal.

2. The apparatus of claim 1, wherein the data-aided symbol timing recovery loop comprises:

a filter for removing a phase response symmetry in a signal derived from the demodulated signal for providing a filter output signal; and

a timing phase detector responsive to the filter output signal for driving the data-aided symbol timing recovery loop.

3. The apparatus of claim 2, wherein the data-aided symbol timing recovery loop further comprises:

a multiplier for derotating the staggered quadrature amplitude modulated signal for providing a derotated staggered quadrature amplitude modulated signal;

an interpolator responsive to the derotated staggered quadrature amplitude modulated signal for providing an interpolated signal;

a demodulator for demodulating the interpolated signal for providing a demodulated signal; and

an equalizer for equalizing the demodulated signal for providing an equalized signal and a training signal;

wherein the filter removes a phase response symmetry from the demodulated signal.

4. The apparatus of claim 3, wherein the demodulator translates the interpolated signal back to a vestigial sideband modulated signal before providing the demodulated signal.

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

6. The apparatus of claim 1, further comprising a data-aided carrier tracking loop.

7. The apparatus of claim 6, wherein the data-aided carrier tracking loop comprises:

a multiplier for derotating the staggered quadrature amplitude modulated signal for providing a derotated staggered quadrature amplitude modulated signal;

an interpolator responsive to the derotated staggered quadrature amplitude modulated signal for providing an interpolated signal;

a demodulator for demodulating the interpolated signal for providing a demodulated signal;

an equalizer for equalizing the demodulated signal for providing an equalized signal and a training signal; and

a carrier phase detector responsive to the signal derived from the staggered quadrature amplitude modulated signal for driving the carrier recovery loop.

8. The apparatus of claim 7, wherein the carrier phase detector is responsive to demodulated signal and the training signal.

9. The apparatus of claim 7, wherein the demodulator translates the interpolated signal back to a vestigial sideband modulated signal before providing the demodulated signal.

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

staggered quadrature amplitude modulating a received signal for providing a staggered quadrature amplitude modulated signal;

equalizing a demodulated signal derived from the staggered quadrature amplitude modulated signal; and

tracking symbol timing in the staggered quadrature amplitude modulated signal by using the demodulated signal.

11. The method of claim 10, wherein the tracking step includes;

removing a phase response symmetry in the demodulated signal for providing a filter output signal; and

detecting timing phase differences as a function of the filter output signal for driving a symbol timing recovery loop;

12. The method of claim 10, further comprising:

derotating the staggered quadrature amplitude modulated signal for providing a derotated staggered quadrature amplitude modulated signal;

interpolating the derotated staggered quadrature amplitude modulated signal for providing an interpolated signal;

demodulating the interpolated signal for providing a demodulated signal; and

equalizing the demodulated signal for providing an equalized signal and a training signal;

wherein the removing step removes a phase response symmetry from the demodulated signal.

13. The method of claim 12, wherein the demodulating step comprises:

converting the interpolated signal back to a vestigial sideband modulated signal before providing the demodulated signal.

14. The method of claim 10, further comprising

tracking carrier phase differences as a function of the demodulated signal for driving a carrier recovery loop.

15. The method of claim 10, wherein the received signal is an ATSC (Advanced Television Systems Committee) VSB (Vestigial Sideband) modulation signal.