Digital broadcasting receiver

• US 5,959,965 A
• Filed: 04/25/1997
• Issued: 09/28/1999
• Est. Priority Date: 05/17/1996
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Taura, Kenichi, Ohkubo, Tadatoshi, Tsujishita, Masahiro, Ohsuga, Yoshiharu
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US08/840,724
• Time in Patent Office: 886 Days
• Field of Search: 370/206, 370/208, 370/203, 370/210, 370/211, 370/450, 370/481, 370/482, 370/215, 370/320, 370/478, 370/484, 375/362, 375/260, 375/200, 375/316, 455/42, 455/59
• US Class Current: 370/203
• CPC Class Codes: H04H 2201/20 digital audio broadcasting [DAB]
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2679 Decision-aided

Abstract

It is an object to correct a frequency deviation at the time of reception of a digital signal in which each carrier is subjected to phase modulation and orthogonal frequency division multiplexing (OFDM). A vector of fixed pattern symbols for reference of received carriers is multiplied by a vector of conjugate complex numbers of the defined values for each element. In the result, elements separated by the same numbers forward and backward from an element at a particular carrier frequency are multiplied together and the results are added. The same processing is applied to cases in which the elements of the vectors are mutually shifted by a plurality of elements from a certain correspondence and synchronization control to the broadcasting frequency is provided on the basis of a value which maximizes the absolute value in the results of the addition and the correspondence at that time.

Claims

1. A digital broadcasting receiver for receiving a digital broadcast transmitted by an orthogonal frequency division multiplexing OFDM transmission system in which each of a plurality of carriers is phase-modulated, comprising:

FFT processing means for converting an OFDM signal expressed in the time domain into demodulation data expressed in the frequency domain; and

frequency deviation detecting means for detecting a phase error for each of the plurality of carriers by first multiplying, for each element, a demodulation data vector of phase reference symbols with a defined complex conjugate vector of the phase reference symbols, then multiplying elements in a vector obtained by the first multiplication which are equally separated from a center element at a particular carrier frequency, and adding the results of the latter multiplication;

wherein solutions obtained by said frequency deviation detecting means for a correspondence in a particular relation between said demodulation data vector of phase reference symbols and said defined complex conjugate vector of phase reference symbols and correspondence in which elements of said demodulation data vector of phase reference symbols and of said defined complex conjugate vector of phase reference symbols are mutually shifted from said particular relation by a plurality of elements, a correspondence which provides a maximum absolute value is obtained, and synchronization control is provided based on a difference of an obtained correspondence from said particular relation and said carrier frequency for said center element.

2. The digital broadcasting receiver according to claim 1, wherein said frequency deviation detecting means includes,

phase correcting means for multiplying, for each element, said demodulation data vector of phase reference symbols with said defined complex conjugate vector of phase reference symbols, and

product-sum operation means for multiplying elements equally separated from said center element at said particular carrier frequency in the output vector of said phase correcting means and adding the multiplication results.

3. The digital broadcasting receiver according to claim 1, further comprising:

integrating means for multiplying elements equally separated from a center element at a particular carrier frequency in the demodulation data vector of phase reference symbols,

phase correcting means for multiplying, for each element, a vector result of said integrating means with each of vectors obtained by multiplying elements equally separated from said center element at said particular carrier frequency and elements separated by a plurality of elements from said element at said particular carrier frequency in said defined complex conjugate vector of phase reference symbols, and

adding means for adding the results of said phase correcting means.

4. The digital broadcasting receiver according to claim 2, further comprising:

carrier shift means for shifting a correspondence between elements of said demodulation data vector and carrier frequencies,

wherein said phase correcting means and said product-sum operation means function when said correspondence between said demodulation data vector of phase reference symbols and said defined complex conjugate vector of phase reference symbols has a particular relation, and when elements of said demodulation data vector of phase reference symbols and of said defined complex conjugate vector of phase reference symbols are mutually shifted from said particular relation by a plurality of elements, a correspondence which provides a maximum absolute value is obtained, and said carrier shift means shifts said demodulation data vector based on said difference of said obtained correspondence from said particular relation and said carrier frequency for said element used as said center in said product-sum operation means.

5. The digital broadcasting receiver according to claim 2, wherein said synchronization control is further based on a phase given by the product-sum operation result which maximizes said absolute value.

6. The digital broadcasting receiver according to claim 5, further comprising;

carrier shift means for shifting a correspondence between elements of said demodulation data vector and carrier frequencies,

wherein said phase correcting means and said product-sum operation means operate when said correspondence between said demodulation data vector of phase reference symbols and said defined complex conjugate vector of phase reference has a particular relation, and when elements of said demodulation data vector of phase reference symbols and of said defined complex conjugate vector of phase reference symbols are mutually shifted from said particular relation by a plurality of elements, a correspondence which provides a maximum absolute value is obtained, and said carrier shift means shifts said vector based on a difference of said obtained correspondence from said particular relation and said carrier frequency for said element used as said center in said product-sum operation means.

7. The digital broadcasting receiver according to claim 1, further comprising;

differential demodulation means for obtaining, for each carrier, a phase difference between demodulation data output by said FFT processing means and the preceding demodulation data, and

phase error detecting means for multiplying a result of differential demodulation of said each carrier output by said differential demodulation means by itself a number of times corresponding to the number of phases of phase modulation on a transmitting side, and obtaining the average,

wherein said synchronization control is further based on an output of said phase error detecting means.

8. The digital broadcasting receiver according to claim 1, wherein said frequency deviation detecting means obtains vectors by first multiplying, for each element, said demodulation data vector of phase reference symbols by said defined complex conjugate vector of phase reference symbols, then multiplying elements in said vectors obtained by the first multiplication which are equally separated from a center element corresponding to a band of baseband frequency of zero of said OFDM signal, adding the results of the latter multiplication and obtaining a correspondence which provides a maximum absolute value of said adding solutions.

9. The digital broadcasting receiver according to claim 1, wherein said frequency deviation detecting means uses limited components of said demodulation data vector of phase reference symbols and said defined complex conjugate vector of phase reference symbols.

10. A digital broadcasting receiver for receiving a digital broadcast transmitted by an orthogonal frequency division multiplexing OFDM transmission system in which each of a plurality of carriers is phase-modulated, comprising:

symbol selecting means for partitioning a received digital signal represented in the time domain into symbols;

region converting means for obtaining demodulation data represented in the frequency domain based on said symbols partitioned by said symbol selecting means;

phase correcting means for multiplying, for each element, a demodulation data vector of phase reference symbols by a defined complex conjugate vector of phase reference symbols;

inverse FFT processing means for applying inverse FFT processing to an output of said phase correcting means;

timing variation detecting means for detecting a peak result of said inverse FFT processing means and detecting a timing shift at which said symbol selecting means partitions symbols according to a position of said peak;

timing control means for controlling timing at which said symbol selecting means partitions symbols according to a timing shift detected by said timing variation detecting means; and

product-sum operation means for multiplying elements equally separated from a center element at a particular carrier frequency in an output vector of said phase correcting means and adding the results;

wherein said phase correcting means provides, to said inverse FFT processing means, an output based on a correspondence between said demodulation data vector of phase reference symbols and said defined complex conjugate vector of phase reference symbols which provides a maximum absolute value solution of the solutions provided by said phase correcting means and said product-sum operation means for a correspondence in a particular relation, and correspondences in which elements of said demodulation data vector of phase reference symbols and of said defined complex conjugate vector of phase reference symbols are mutually shifted from said particular relation by a plurality of elements.

11. The digital broadcasting receiver according to claim 10, wherein said phase correcting means and said product-sum operation means operate when a correspondence between said demodulation data vector of phase reference symbols and said defined complex conjugate vector of phase reference symbols has a particular relation, and when said elements of said demodulation data vector of phase reference symbols and of said defined complex conjugate vector of phase reference symbols are shifted from said particular relation by a plurality of elements, a correspondence which provides a maximum absolute value result is obtained, and synchronization control to said broadcasting frequency is provided based on a difference of an obtained correspondence from said particular relation and said carrier frequency for said element used as said center in said product-sum operation means.

12. The digital broadcasting receiver according to claim 11, wherein said synchronization control is achieved in accordance with the phase given by a result of the product-sum operation which maximizes said absolute value.

13. The digital broadcasting receiver according to claim 10, further comprising;

differential demodulation means for obtaining, for each carrier, a phase difference between demodulation data output by said region converting means and demodulation data immediately preceding said demodulation data, and

phase error detecting means for multiplying a result of differential demodulation for said each carrier output by said differential demodulation means by itself a number of times corresponding to the number of phase modulation phases on a transmitting side, and obtaining the average,

wherein said synchronization control is based on an output of said phase error detecting means.

14. The digital broadcasting receiver according to claim 10, further comprising:

carrier shift means for shifting a correspondence between elements of said demodulation data vector and carrier frequencies,

wherein said phase correcting means and said product-sum operation means function when a correspondence between said demodulation data vector of phase reference symbols and said defined complex conjugate vector of phase reference symbols has a particular relation, and when said elements of said demodulation data vector of phase reference symbol and said defined complex conjugate vector of phase reference symbols are mutually shifted from said particular relation by a plurality of elements, a correspondence which provides a maximum absolute value result is, and said carrier shift means shifts said demodulation data vector based on a difference of said obtained correspondence from said particular relation and said carrier frequency for said center element.

15. The digital broadcasting receiver according to claim 10, wherein said phase correcting means multiples, for each element, said demodulation data vector of phase reference symbols by said defined complex conjugate vector of phase reference symbols, and said product-sum operation means multiplies elements in an output vector from said phase correcting means equally separated from an element corresponding to a band of baseband frequency of zero of said OFDM signal and adds the results.

16. The digital broadcasting receiver according to claim 10, wherein said phase correcting means and said product-sum operation means use limited parts of said demodulation data vector of phase reference symbols and said defined complex conjugate vector of phase reference symbols.

17. A digital broadcasting receiver for receiving a digital broadcast transmitted by an orthogonal frequency division multiplexing OFDM transmission system in which each of a plurality of carriers is phase-modulated, comprising:

FFT processing means for converting a received OFDM signal expressed in the time domain into demodulation data expressed in the frequency domain;

phase correcting means for multiplying, for each element, a demodulation data vector of phase reference symbols output by said FFT processing means by a defined complex conjugate vector of phase reference symbols;

product-sum operation means for multiplying elements equally separated from a center element at a particular carrier frequency in an output vector of said phase correcting means, and adding the results of multiplication;

carrier shift means for shifting correspondence between elements of said demodulation data vector and carrier frequencies; and

control means for controlling said carrier shift means, wherein said phase correcting means and said product-sum operation means function when a correspondence between said demodulation data vector of phase reference symbols and said defined complex conjugate vector of phase reference symbols has a particular relation, and when elements of said demodulation data vector of phase reference symbols and defined complex conjugate vector of phase reference symbols are mutually shifted from the particular relation by a plurality of elements, a correspondence which provides a maximum absolute value result is obtained, and said control means controls said carrier shift means based on a difference of an obtained correspondence from said particular relation and said carrier frequency for said center element.

18. The digital broadcasting receiver according to claim 17, wherein said control means also provides synchronization control based on said carrier frequency for said element used as said center.

19. The digital broadcasting receiver according to claim 18, wherein said synchronization control is also based on a phase given by the product-sum operation result which maximizes said absolute value.