Carrier recovery apparatus of VSB receiver and a method of recovering carrier using the same

• US 7,149,260 B2
• Filed: 01/23/2003
• Issued: 12/12/2006
• Est. Priority Date: 01/29/2002
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Joon-soo, Kim, Ki-bum
• Primary Examiner(s): VO, DON NGUYEN
• Application Number:
  US10/349,069
• Publication Number:
  US 20030142760A1
• Time in Patent Office: 1,419 Days
• Field of Search: 375/270, 375/321, 375/326, 375/327, 375/343, 375/355, 329/357, 455/47
• US Class Current: 375/321
• CPC Class Codes: H04L 2027/0057 quadrature phase
• CPC Class Codes: H04L 2027/0071 Control of loops
• CPC Class Codes: H04L 2027/0087 Out-of-band signals, (e.g. pilots)
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 27/2273 associated with quadrature demodulation, e.g. Costas loop

Abstract

A carrier recovery apparatus includes a first LPF calculating a carrier changing in accordance with a frequency offset, by using a pilot tone included in an I-signal of a VSB broadcasting signal, a limiter limiting a size of the carrier calculated by the first LPF and outputting the limited size of the carrier, a multiplier multiplying the limited size of the carrier from the limiter by a Q-signal of the VSB broadcasting signal, a second LPF extracting a DC-property corresponding to a frequency error of the carrier from a product output from the multiplier, a numerically controlled oscillator (NCO) generating a complex carrier corresponding to the DC-property from the second LPF, and a frequency error providing unit arranged between the second LPF and the NCO, storing the DC-property from the second LPF, and when the pilot tone is distorted by a damaged pilot in the I-signal, providing the NCO with the DC-property that is previously input and stored therein.

Claims

1. A carrier recovery apparatus of a Vestigial Sideband (VSB) broadcasting signal having an I-signal and a Q-signal, comprising:

a first low pass filter (LPF) calculating a carrier of the VSB broadcasting signal changing in accordance with a frequency offset of the VSB broadcasting signal by using a pilot tone included in the I-signal of the VSB broadcasting signal;

a limiter limiting a size of the carrier calculated by the first LPF;

a multiplier multiplying the limited size of the carrier from the limiter by the Q-signal of the VSB broadcasting signal to generate a product;

a second LPF extracting a DC-property signal corresponding to a frequency error of the carrier from the product from the multiplier;

a numerically-controlled oscillator (NCO) generating a complex carrier corresponding to the DC-property signal extracted from the second LPF; and

a frequency error providing unit storing the DC-property signal extracted from the second LPF, and when the pilot tone is distorted by a damaged pilot of the I-signal, providing the NCO with the stored DC-property signal.

2. The carrier recovery apparatus of claim 1, further comprising a matched filter generating the VSB broadcasting signal from the I-signal and the Q-signal which have been multiplied by the complex carrier of the NCO, and generating information representing a damage of a pilot occurring due to a change of a channel environment, wherein the frequency error providing unit comprises:

a register storing the DC-property signal from the second LPF for a predetermined time and outputting the DC-property signal;

a switching unit selectively outputting one of the stored DC-property signal from the register and a second DC-property signal newly generated by the second LPF;

a mode control unit receiving the information from the matched filter and controlling an output of the switching unit in accordance with the received information; and

a counting unit counting a control time of the mode control unit which performs controlling of the register and the switching unit in response to determining according to the received information about the pilot damage that the pilot is damaged, and providing the mode control unit with time-over information when the counted control time exceeds a reference time,

wherein the mode control unit controls the switching unit to output the second DC-property signal from the second LPF in accordance with the time-over information.

3. The carrier recovery apparatus of claim 2, wherein the mode control unit controls the switching unit to output the DC-property signal from the register in response to determining according to the received information about the pilot damage that the pilot is damaged, while controlling the switching unit to output the second DC-property signal from the second LPF in response to determining according to the received information about the pilot damage that the pilot is not damaged.

4. The carrier recovery apparatus of claim 3, wherein the NCO generates a fixed complex carrier in response to the DC-property signal from the register, when the pilot is damaged and thus the switching unit outputs the DC-property signal from the register in response to a control signal of the mode control unit.

5. The carrier recovery apparatus of claim 4, wherein the first LPF comprises an automatic frequency control low pass filter (AFC-LPF), and the second LPF comprises an automatic phase control low pass filter (APC-LPF).

6. A Vestigial Sideband (VSB) broadcasting signal receiver comprising:

an analog-to-digital converter (ADC) converting an analog VSB broadcasting signal into a digital signal;

an I/Q splitter shifting the digital signal to a baseband signal and splitting the baseband signal into an I-signal and a Q-signal constituting a VSB broadcasting signal;

a symbol timing recovery (STR) unit detecting a sampling timing error of the VSB broadcasting signal with respect to I-signal and Q-signal, respectively;

an interpolator compensating for a sampling offset of the I-signal and the Q-signal in accordance with the sampling timing error detected by the STR unit;

a carrier recovery unit generating the complex carrier corresponding to a frequency error of the VSB broadcasting signal calculated from a pilot tone of a pilot of the VSB broadcasting signal when the pilot included in the I-signal is damaged;

a multiplier multiplying each of the I-signal and the Q-signal by the complex carrier to recover a carrier of the VSB broadcasting signal based on the complex carrier to generate a product;

a matched filter generating the VSB broadcasting signal by combining the I-signal and the Q-signal in response to the product of the multiplier; and

an equalizer compensating for a distortion of the VSB broadcasting signal occurring in a transmitting channel with respect to the VSB broadcasting signal from the matched filter,

wherein the carrier recovery unit comprises;

a first low pass filter (LPF) calculating the carrier changing in accordance with a frequency offset, by using the pilot tone included in the I-signal;

a limiter limiting a size of the carrier from the first LPF and outputting the limited size of the carrier;

a second multiplier multiplying the limited size of the carrier from the limiter by the Q-signal to generate a second product;

a second low pass filter (LPF) extracting a DC-property signal corresponding to the frequency error of the carrier from the second product of the second multiplier;

a numerically-controlled oscillator (NCO) generating the complex carrier corresponding to the DC-property signal extracted from the second LPF; and

a frequency error providing unit storing the DC-property signal from the second LPF, and when the pilot tone is distorted due to a damaged pilot of the I-signal, providing the NCO with the stored DC-property signal which is previously input and stored therein.

7. The VSB broadcasting signal receiver of claim 6, wherein the frequency error providing unit comprises:

a register storing the DC-property signal from the second LPF for a predetermined time and outputting the DC-property signal;

a switching unit selectively outputting the DC-property signal from one of the register and the second LPF;

a mode control unit receiving from the matched filter information about a pilot damage of the pilot occurring due to a change of a channel environment, and controlling an output of the switching unit in accordance with the received information about the pilot damage; and

a counting unit counting a control time of the mode control unit that performs controlling the switching unit and the register upon determining according to the received information about the pilot damage that the pilot is damaged, and providing the mode control unit with time-over information when the counted control time exceeds a reference time,

wherein the mode control unit controls the switching unit to output the DC-property signal from the second LPF in accordance with the provided time-over information.

8. The VSB broadcasting signal receiver of claim 7, wherein the mode control unit controls the switching unit to output the DC-property signal from the register in response to determining according to the received information about the pilot damage that the pilot is damaged while controlling the switching unit to output the DC-property signal from the second LPF in response to determining according to the received information about the pilot damage that the pilot is not damaged.

9. The VSB broadcasting signal receiver of claim 8, wherein the NCO generates a fixed complex carrier in response to the DC-property signal from the register when the pilot is damaged and thus the switching unit outputs the DC-property signal from the register in response to a control signal of the mode control unit.

10. The VSB broadcasting signal receiver of claim 9, wherein the first LPF comprises an automatic frequency control low pass filter (AFC-LPF), and the second LPF comprises an automatic phase control low pass filter (APC-LPF).

11. The VSB broadcasting signal receiver of claim 6, further comprising:

a phase tracking loop (PTL) compensating for a remaining phase error in the VSB broadcasting signal after the distortion of the VSB broadcasting signal is compensated by the equalizer.

12. A method of recovering a carrier of a Vestigial Sideband (VSB) broadcasting signal, comprising:

calculating a carrier of the VSB broadcasting signal by using a pilot tone included in an I-signal of the VSB broadcasting signal after the carrier of the VSB broadcasting signal is changed in accordance with a frequency offset;

limiting a size of the calculated carrier and outputting the limited size of the carrier;

multiplying the limited size of the carrier by a Q-signal of the VSB broadcasting signal to generate a product;

extracting a first DC-property signal corresponding to a frequency error of the carrier from the product of the multiplication;

storing the first DC-property signal, and selectively outputting one of the stored first DC-property signal and a second DC-property signal newly generated corresponding to another frequency error of the carrier according to whether the pilot of the I-signal is damaged; and

generating a complex carrier corresponding to the one of the first DC-property signal and the second DC-property signal.

13. The carrier recovery method of claim 12, wherein the selective outputting of the one of the first DC-property signal and the second DC-property signal comprises:

storing for a predetermined time the first DC-property signal and outputting the first DC-property signal;

receiving information about a pilot damage occurring due to a change in a channel environment;

selectively outputting of the one of the first DC-property signal and the second DC-property signal in accordance with the information about the pilot damage; and

in response to determining according to the information about the pilot damage that the pilot is damaged, counting a control time for the damaged pilot, and in response to the counted control time exceeding a reference time, outputting the second DC-property signal.

14. The carrier recovery method of claim 13, wherein the outputting of the one of the first DC-property signal and the second DC-property signal comprises:

outputting the first DC-property signal in response to determining according to the information about the pilot damage that the pilot is damaged; and

outputting the second DC-property signal in response to determining according to the information about the pilot damage that the pilot is not damaged.

15. A method of recovering a carrier of a Vestigial Sideband (VSB) broadcasting signal having an I-signal and a Q-signal in a VSB receiver, comprising:

generating a first DC-property signal indicating a first frequency error of a carrier of the VSB broadcasting signal in response to the I-signal and the Q-signal;

generating a second property signal indicating a second frequency error of the carrier of the VSB broadcasting signal in response to the I-signal and the Q-signal after the first DC-property signal has been generated;

generating information representing a pilot tone of a pilot of the VSB broadcasting signal;

selectively outputting one of the first DC-property signal and the second DC-property signal in response to the information;

generating a complex carrier in response to the one of the first DC-property signal and the second DC-property signal;

multiplying each of the I-signal and the Q-signal by the complex carrier; and

combining the multiplied I-signal and the multiplied Q-signal into the VSB broadcasting signal.

16. The method of claim 15, wherein the selectively outputting of the one of the first DC-property signal and the second DC-property signal comprises:

outputting the first DC-property signal when the information represents that the pilot tone is damaged.

17. The method of claim 15, wherein the selectively outputting of the one of the first DC-property signal and the second DC-property signal comprises:

outputting the second DC-property signal when the information represents that the pilot tone is not damaged.

18. The method of claim 15, wherein the generating of the first DC-property signal comprises:

storing the first DC-property signal in a memory before the second DC-property signal is generated.

19. The method of claim 18, wherein the selectively outputting of the one of the first DC-property signal and the second DC-property signal comprises:

outputting the stored first DC-property signal when the information represents that the pilot tone is damaged.

20. The method of claim 15, wherein the VSB receiver comprises a matching filter receiving the combined VSB broadcasting signal, detecting the pilot tone of the pilot of the carrier of the VSB broadcasting signal, and generating the information indicating the pilot tone, and the selectively outputting of the one of the first DC-property signal and the second DC-property signal comprises:

outputting the second DC-property signal when the information represents that the pilot tone is not damaged; and

outputting the first DC-property signal regardless of the second DC-property signal when the information represents that the pilot tone is damaged.

21. A carrier recovery apparatus of a Vestigial Sideband (VSB) broadcasting signal having an I-signal and a Q-signal, comprising:

a filter unit generating a first DC-property signal indicating a first frequency error of a carrier of the VSB broadcasting signal in response to the I-signal and the Q-signal, and generating a second DC-property signal indicating a second frequency error of the carrier of the VSB broadcasting signal in response to the I-signal and the Q-signal after the first DC-property signal has been generated;

a frequency error providing unit outputting the first DC-property signal instead of the second DC-property in response to information representing that a pilot tone of a pilot of the VSB broadcasting signal is damaged; and

a numerically-controlled oscillator generating a complex carrier corresponding to the first DC-property signal;

a multiplier multiplying each of the I-signal and the Q-signal by the complex carrier to generate a product; and

a matched filter combining the multiplied I-signal and the multiplied Q-signal into the VSB broadcasting signal in response to the product of the multiplier and generating the information from the combined VSB broadcasting signal.

22. The carrier recovery apparatus of claim 21, wherein the frequency error providing unit stores the first DC-property signal in a memory when the filter unit generates the second DC-property signal.

23. The carrier recovery apparatus of claim 22, wherein the frequency error providing unit outputs the stored first DC-property signal regardless of the second DC-property signal when the pilot tone of the pilot of the VSB broadcasting signal is damaged.

24. The carrier recovery apparatus of claim 22, wherein the frequency error providing unit outputs the second DC-property signal when the pilot tone of the pilot of the VSB broadcasting signal is not damaged.

25. The carrier recovery apparatus of claim 22, wherein the filter unit comprises:

a first low pass filter generating a size of a carrier of the VSB broadcasting signal;

a limiter limiting the size of the carrier;

a second multiplier multiplying the limited size of the carrier by the Q-signal to generate a second product; and

a second LPF extracting the first DC-property signal and the second DC-property signal corresponding to a frequency error of the carrier from the second product from the second multiplier.

26. The carrier recovery apparatus of claim 22, wherein the frequency error providing unit comprises:

a register storing the first DC-property signal for a predetermined time;

a switching unit receiving the stored first DC-property signal from the register and the second DC-property signal from the filter unit; and

a mode control unit controlling the switching unit to output one of the stored first DC-property signal from the register and the second DC-property signal from the filter unit in accordance with the received information.

27. The carrier recovery apparatus of claim 22, wherein the control unit comprises:

a counting unit counting a control time when the information represents that the pilot tone is damaged, and providing the mode control unit with time-over information when the counted control time exceeds a reference time, wherein the mode control unit controls the switching unit to output the second DC-property signal from the second LPF in accordance with the time-over information.

28. The carrier recovery apparatus of claim 27, wherein the mode control unit controls the switching unit to output the first DC-property signal when the counted control time does not exceed the reference time.

29. A Vestigial Sideband (VSB) broadcasting signal receiver, comprising:

an analog-to-digital converter (ADC) converting an analog VSB broadcasting signal into a digital signal;

an I/Q splitter shifting the digital signal to a baseband signal and splitting the baseband signal into an I-signal and a Q-signal constituting a VSB broadcasting signal;

a symbol timing recovery (STR) unit detecting a sampling timing error of the VSB broadcasting signal with respect to I-signal and Q-signal, respectively;

an interpolator compensating for a sampling offset of the I-signal and the Q-signal in accordance with the sampling timing error detected by the STR unit;

a carrier recovery unit generating the complex carrier based on a DC-property signal which was previously input and stored therein when a pilot included in the I-signal is damaged;

a multiplier multiplying each of the I-signal and the Q-signal by the complex carrier to recover a carrier of the VSB broadcasting signal based on the complex carrier to generate a product;

a matched filter generating the VSB broadcasting signal by combining the I-signal and the Q-signal in response to the product of the multiplier; and

an equalizer compensating for a distortion of the VSB broadcasting signal occurring in a transmitting channel with respect to the VSB broadcasting signal from the matched filter.