Diversity receiver, and method for receiving orthogonal frequency division multiplex signal

• US 20040022215A1
• Filed: 06/11/2003
• Published: 02/05/2004
• Est. Priority Date: 12/12/2000
• Status: Active Grant

• Current Assignee: JVC Kenwood Corporation
• Original Assignee: Kabushiki Kaisha Kenwood (JVC Kenwood Corporation)
• Inventors: Shinoda, Atsushi, Okuhata, Yasuhide
• Granted Patent: US 7,801,018 B2
• Time in Patent Office: Days
• US Class Current: 370/334
• CPC Class Codes: H04B 7/08 at the receiving station
• CPC Class Codes: H04B 7/0805 with single receiver and antenna switching H04B7/0822 takes precedence
• CPC Class Codes: H04B 7/0848 Joint weighting
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

A diversity receiver capable of stably receiving an orthogonal frequency division multiplex signal, wherein a demodulator is so operated that the attenuation of the received signal is varied step by step every time a period corresponding to a guard interval section comes if it is determined that the reception level is increased by switching the attenuation in any one of variable attenuators, and the demodulator is so operated that the variable attenuator designated by an antenna control pointer is changed and the attenuation is varied if it is determined that the variable attenuator designated by an antenna control pointer is identical with the variable attenuator designated by an antenna fixing pointer.

Claims

1. A diversity receiver for receiving an orthogonal frequency division multiplex signal to by using a plurality of antennas, each of symbol periods of the signal consisting of an effective symbol section and a guard interval section, the diversity receiver comprising:

a plurality of amplification means for individually amplifying a signal received at each of the antennas;

a plurality of attenuation means each for individually attenuating each of the received signals amplified by each of said amplification means;

signal synthesis means for coupling a plurality of received signals attenuated by said attenuation means and generating a synthesized received signal;

control means for individually controlling an attenuation amount of each of said attenuation means; and

demodulation means for demodulating the synthesized received signal to obtain a digital signal,

wherein said control means operates to adjust the attenuation amount of each of said attenuation means in such a manner that said control means selectively supplies said signal synthesis means with a received signal received at least one of the antennas, and if received signals received at two or more antennas are to be supplied, said control means additionally supplies said signal synthesis means with only a received signal or signals contributing to a rise of a level of the synthesized received signal.

2. The diversity receiver according to claim 1, wherein said control means judges during a period corresponding to the guard interval section whether or not the level of the synthesized received signal rises upon an additional supply of the received signal received at a given antenna.

3. The diversity receiver according to claim 2, wherein a judgement on a rise of the level of the synthesized received signal is performed by changing the attenuation amount of said attenuation means corresponding to the given antenna during the period corresponding to the guard interval section and measuring a change in the level of the synthesized received signal.

4. The diversity receiver according to claim 3, wherein in accordance with a measurement result of the change in the level of the synthesized received signal caused by changing the attenuation amount of said attenuation means for the given antenna, said control means determines a renewal target attenuation amount of said attenuation means for the given antenna and gradually changes the attenuation amount toward the determined renewal target attenuation amount.

5. The diversity receiver according to claim 4, wherein a change in the attenuation amount toward the renewal target attenuation amount is performed stepwise each time the period corresponding to the guard interval section arrives.

6. The diversity receiver according to claim 3, wherein said control means changes the attenuation amount of said attenuation means corresponding to the given antenna during the period corresponding to the guard interval section, and after the level of the synthesized received signal is measured, changes at an end of the period the attenuation amount of said attenuation means to the attenuation amount before an attenuation amount change.

7. The diversity receiver according to claim 4, wherein said control means measures the level of the synthesized received signal by changing the attenuation amount of said attenuation means corresponding to the given antenna to a maximum value, judges whether or not the level of the synthesized received signal rises, and if it is judged that the level rises, increases stepwise the attenuation amount of said attenuation means whose attenuation amount was changed to the maximum value, each time the period corresponding to the guard interval section arrives.

8. The diversity receiver according to claim 4, wherein said control means measures the level of the synthesized received signal by changing the attenuation amount of said attenuation means corresponding to the given antenna to a minimum, judges whether or not the level of the synthesized received signal rises, and if it is judged that the level rises, decreases stepwise the attenuation amount of said attenuation means whose attenuation amount was changed to the minimum value, each time the period corresponding to the guard interval section arrives.

9. The diversity receiver according to claim 3, wherein said control means gradually changes the attenuation level of said attenuation means whose attenuation amount is to be changed, during a plurality of periods corresponding to a plurality of consecutive guard interval sections, to monitor the change in the level of the synthesized received signal during the plurality of periods.

10. The diversity receiver according to claim 9, wherein said control means measures the level of the synthesized received signal immediately before and after the attenuation amount of said attenuation means whose attenuation amount is to be changed, generates a signal indicative of a difference between levels measured immediately before and after, and accumulating the difference to judge whether or not there is a tendency that the level of the synthesized received signal rises.

11. The diversity receiver according to claim 3, wherein said control means includes a fix pointer for instructing to fix the attenuation amount of at least one of the plurality of said attenuation means corresponding to the plurality of antennas, and a variable pointer for designating an antenna for which the attenuation amount is changed.

12. The diversity receiver according to claim 11, wherein said control means judges whether said attenuation means designated by said fix pointer is the same as said attenuation means designated by said variable pointer, if it is judged that said attenuation means are the same, makes said variable pointer designate another of said attenuation means, and if it is judged that said attenuation means are different, changes the attenuation amount of said attenuation means designated by said variable pointer.

13. The diversity receiver according to claim 12, wherein said fix pointer designates said attenuation means whose the attenuation amount is zero, among the plurality of said attenuation means.

14. An orthogonal frequency division multiplex reception method for receiving an orthogonal frequency division multiplex signal by using a plurality of antennas, each of the symbol periods of the signal being consisting of an effective symbol section and a guard interval section, the method comprising steps of:

individually amplifying a signal received at each of the antennas;

individually attenuating each of the amplified received signals;

individually coupling a plurality of attenuated received signals and generating a synthesized received signal;

controlling each attenuation amount at said attenuating step; and

demodulating the synthesized received signal to obtain a digital signal,

wherein said controlling step executes signal processing to adjust each attenuation amount in such a manner that said controlling step selects a received signal received at least one of the antennas, and if received signals received at two or more antennas are to be selected, said signal synthesizing step synthesizes only a received signal or signals contributing to a rise of a level of the synthesized received signal.

15. The method according to claim 14, wherein said controlling step judges during a period corresponding to the guard interval section whether or not the level of the synthesized received signal rises upon a selection of the received signal received at a given antenna.

16. The method according to claim 15, wherein a judgement on a rise of the level of the synthesized received signal is performed by changing the attenuation amount corresponding to the given antenna during the period corresponding to the guard interval section and measuring a change in the level of the synthesized received signal.

17. The method according to claim 16, wherein in accordance with a measurement result of the change in the level of the synthesized received signal caused by changing the attenuation amount corresponding to the given antenna, said controlling step determines a renewal target attenuation amount corresponding to the given antenna and gradually changes the attenuation amount toward the determined renewal target attenuation amount.

18. The method according to claim 17, wherein a process of changing the attenuation amount toward the renewal target attenuation amount is performed stepwise each time the period corresponding to the guard interval section arrives.

19. The method according to claim 16, wherein said controlling step changes the attenuation amount corresponding to the given antenna during the period corresponding to the guard interval section, and after the level of the synthesized received signal is measured, changes at an end of the period the attenuation amount to the attenuation amount before an attenuation amount change.