JP2003224539A - Diversity receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diversity receiver capable of substantially selecting an antenna and stably performing receiving. <P>SOLUTION: In this diversity receiver provided with a plurality of antennas for receiving a signal subjected to OFDM modulation, variable attenuators 9 to 12 respectively attenuate reception signals from the antennas 1 to 4 and synthesize respective attenuated outputs, an orthogonal detector 16 orthogonally detects a synthesized output to obtain baseband I and Q signals, a guard correlator 20 detects a correlation in a guard interval period between the baseband I and Q signals, and the attenuation quantity of variable attenuators is controlled in a period corresponding to a guard interval section under the control of a diversity control circuit 22 based on whether or not a peak level of a correlation output in a guard interval period increases. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity receiver that receives a broadcast signal modulated (OFDM modulated) by an orthogonal frequency division multiplexing system.

[0002]

2. Description of the Related Art 1OFD of OFDM modulated broadcast signal
The M transmission symbol period is composed of an effective symbol section and a section called a guard interval. The effective symbol period is a signal period required for data transmission. The guard interval is for preventing intersymbol interference such as multipath, and is a cyclic copy of the last predetermined period length portion of the effective symbol section to the beginning of the effective symbol section.

Diversity receivers for receiving OFDM modulated broadcast signals such as digital terrestrial television broadcast signals are known. A conventional diversity receiver of this type is proposed by the applicant (Japanese Patent Application No. 2000-38005).

This diversity receiver detects the received signal level in a diversity receiver in which received signals from a plurality of antennas are attenuated by variable attenuators, the attenuated outputs are combined, and the combined output is demodulated into a baseband signal. , When the attenuation amount of one variable attenuator in the variable attenuator is switched during the period corresponding to the guard interval section based on the detected reception signal level and the reception signal level rises by switching the attenuation amount, the guard interval section The attenuation amount of the one variable attenuator is changed stepwise at a timing corresponding to the period corresponding to.

It is conceivable to use a power signal based on the power of the baseband IQ signal instead of the received signal level in the diversity receiver. The diversity receiver B is configured as shown in FIG.

In the diversity receiver B, the RF signals received by the antennas 1, 2, 3, 4 are amplified by the low noise amplifiers 5, 6, 7, 8 respectively, and then the variable attenuators 9, 10, 11, respectively. After being attenuated at 12, the mixture is input to the mixer 13 for synthesis, and the output of the mixer 13 is supplied to the tuner 14.

The tuner 14, which has received the combined output from the mixer 13, amplifies the combined output, frequency-converts it, and limits the band to convert it into an intermediate-frequency signal. The intermediate frequency signal output from the tuner 14 is an AD converter 15
To a digital signal, and the converted digital signal is supplied to the quadrature detector 16 for quadrature detection,
Convert to baseband I and Q signals.

The baseband I and Q signals output from the quadrature detector 16 are supplied to the effective symbol extraction circuit 17, and based on the timing signal (FFT-WINDOW) indicating the effective symbol section output from the timing reproduction circuit 21, In the effective symbol extraction circuit 17, only the signal in the period corresponding to the effective symbol is fetched from the baseband I and Q signals, and the signal in the period corresponding to the effective symbol section is F.
The data is supplied to the FT circuit 18, FFT processing is performed in the FFT circuit 18 to demodulate the OFDM modulated signal to separate into information for each carrier, and the information is supplied to the demapper circuit 19 to be demapped and transmitted as demodulated data.

On the other hand, the baseband I and Q signals output from the quadrature detector 16 are supplied to the guard correlator 20, and the input baseband I and Q signals of the guard correlator 20 and the baseband I and Q signals are validated. The product of the delayed baseband I and Q signals delayed by the time width of the symbol period is integrated over the time width of the guard interval period, and the integration is sequentially performed for each sample period for A / D conversion in the A / D converter 15. By performing the shift, the correlation output is obtained from the integrated value, the correlation output is supplied to the timing reproduction circuit 21, the timing of the OFDM symbol is obtained from the peak position of the correlation output, and the timing signal (FFT-WINDOW) is obtained.
To the effective symbol extraction circuit 17.

The baseband IQ signal output from the quadrature detector 16 is supplied to the power detector 24, and the power detector 24 samples each sample for A / D conversion in the A / D converter 15. The baseband I and Q signals are converted into electric power and output as an electric power signal (RX-POWER).

The power signal (RX-POWER) and the timing signal (FFT-WINDOW) are supplied to the diversity control circuit 25, and the diversity control circuit 25 controls the attenuation amounts of the variable attenuators 9, 10, 11, and 12. Attenuation control signals CONT1, CONT2, CONT3,
CONT4 is connected to the variable attenuators 9, 10, 11, 12 respectively.
To the variable attenuators 9 and 1 so that the output level of the mixer 13, that is, the combined reception signal level becomes high.
The attenuation amount of 0, 11, and 12 is controlled.

The operation of the diversity control circuit 25 will be described with reference to FIG. 7, FIG. 8, FIG. 9, and FIG. 1 using the attenuation control signal CONT1 as an example.
This will be described with reference to the timing chart shown in FIG.

Here, the timing signal (FFT-WIN
DOW) indicates a period corresponding to the effective symbol period when the potential is high, and indicates a period corresponding to the guard interval period when the potential is low. The attenuation amount control signal CONT1 is a signal for controlling the attenuation amount of the variable attenuator 9. When the level of the attenuation amount control signal CONT1 is the maximum, the attenuation amount is controlled to 0, and the level of the attenuation amount control signal CONT1 is the minimum. In this case, the amount of attenuation becomes maximum. Power signal (RX-POWER
R) indicates the power of the baseband I and Q signals, and indicates that the power of the baseband I and Q signals is high when the level is high.

In FIG. 7, in order to prevent the input of the mixer 13 from disappearing, at least one or more of the variable attenuators 10, 11 and 12 are set to 0, and the attenuation is set to the initial state. The level of the control signal CONT1 is minimum, that is, the attenuation amount of the variable attenuator 9 is maximum. Here, in order to evaluate the signal received by the antenna 1,
In the section where the timing signal (FFT-WINDOW) is at a low potential (see FIG. 7A), the attenuation control signal CONT1
Of the variable attenuator 9 is maximized (see FIG. 7B).
The attenuation of is set to 0.

As a result, the signal received by the antenna 1 is also combined by the mixer 13 and input to the tuner 14. At this time, in FIG. 7, the power signal (RX-P
The figure shows a case where the level of (OWER) has risen (Fig. 7).
(See (c)). In this case, if the mixer 13 combines the signals received by the antenna 1 and combines them, the output level of the mixer 13 increases, and it is determined that the reception condition is improved. In order to avoid the change, the level of the attenuation amount control signal CONT1 is once returned to the minimum at the timing when the timing signal (FFT-WINDOW) becomes high potential, and thereafter, the timing signal (FFT-WIND) is returned to the minimum level.
The level of the attenuation control signal CONT1 is increased stepwise until it reaches its maximum in the section where DOW) is at a low potential (see FIG. 7B).

In the case of FIG. 8, the initial state is the same as in the case of FIG. 7, but the timing signal (FFT-WINDOW) is used.
In a section in which W) becomes a low potential (see FIG. 8A), the level of the attenuation control signal CONT1 is maximized (FIG. 88B).
8), the level of the power signal (RX-POWER) is lowered by setting the attenuation amount of the variable attenuator 13 to 0 (see FIG. 8C).

In this case, since the signals received by the antenna 1 are combined in the mixer 13, the level of the output signal of the mixer 13 is lowered, and the power signal (RX-P
It is considered that the OWER level has decreased, and it is determined that the reception conditions have deteriorated. Therefore, the timing signal (FF)
The level of the attenuation control signal CONT1 is returned to the minimum at the timing when (T-WINDOW) becomes a high potential (FIG. 8 (b)).
reference).

In the case of FIG. 9 as well, the variable attenuators 10, 11, 1 are used.
Among the two, at least one or more have the attenuation amount of 0, and the level of the attenuation amount control signal CONT1 is maximum, that is, the attenuation amount of the variable attenuator 9 is 0 in the initial state. Here, in order to evaluate the signal received by the antenna 1, the attenuation control signal C is applied in a section where the timing signal (FFT-WINDOW) is at a low potential (see FIG. 9A).
The level of ONT1 is minimized (see FIG. 9B), and the attenuation amount of the variable attenuator 9 is maximized.

As a result, the signals received by the antenna 1 are attenuated, combined by the mixer 13 and input to the tuner 14. As a result, FIG. 9 shows a case where the level of the power signal (RX-POWER) rises (see FIG. 9C). In this case, if the signal received by the antenna 1 is attenuated, the power signal (RX-POW
(ER) level rises, it is determined that the reception conditions are improved, and the level of the attenuation control signal CONT1 is once returned to the maximum level at the timing when the timing signal (FFT-WINDOW) becomes high potential (see FIG. 9B), After that, the timing signal (FFT-WINDOW) is sequentially changed stepwise until the level of the attenuation amount control signal CONT1 becomes minimum in the low potential section (see FIG. 9B).

In the case of FIG. 10, the initial state is as shown in FIG.
The timing signal (FFT-WI
Section where NDOW) becomes low potential (see FIG. 10 (a))
Then, the case where the level of the power signal (RX-POWER) is lowered by minimizing the level of the attenuation control signal CONT1 (see FIG. 10B) and maximizing the attenuation of the variable attenuator 9 is shown. (See FIG. 10 (c)). In this case, it is considered that the level of the output signal of the mixer 13 was decreased by combining the signals received by the antenna 1 in the mixer 13, and the level of the power signal (RX-POWER) was decreased. Since it is determined that the reception condition has deteriorated, the level of the attenuation control signal CONT1 is returned to the maximum at the timing when the timing signal (FFT-WINDOW) becomes high potential (see FIG. 10 (b)).

In this way, the variable attenuators 9, 10, 1 are maintained with the attenuation amount of one or more variable attenuators maintained at 0.
The attenuation amounts of 1 and 12 are sequentially controlled to control the signal level input to the tuner 14 to be maximum.

[0022]

However, even if the attenuation amount of the variable attenuator is controlled as described above, the power signal (RX-
Since the power of the noise component is also included in the POWER), the reception signal level of the OFDM modulation signal is low and the output of the low noise amplifier has almost no noise component under the reception condition that the reception signal level is low and the C / N is bad. If there is only one antenna, if the amount of attenuation of the variable attenuator of the system is set to 0 and the signals from other antennas are combined with the signal amplified by the low noise amplifier, the power of the noise component will be added. After that, the level of the power signal (RX-POWER) rises,
Although the diversity control circuit determines that the reception condition is good, there is a problem that the C / N actually becomes worse.

An object of the present invention is to provide a stable diversity receiver by improving the reliability of substantial selection of antennas.

[0024]

A diversity receiver of the present invention is a diversity receiver having a plurality of antennas for receiving an OFDM-modulated signal in which one symbol period includes an effective symbol section and a guard interval section. Therefore, the variable attenuating means for attenuating the received signals from the plurality of antennas, the demodulating means for synthesizing the outputs from the variable attenuating means and demodulating the synthesized output, and the baseband signal obtained by the demodulating means Correlation detection means for detecting the correlation of the period corresponding to the guard interval section of
Attenuation amount control means for changing the attenuation amount of the variable attenuation means in the period corresponding to the guard interval section based on whether or not the peak level of the correlation output in the period corresponding to the guard interval section has increased. Is characterized by.

According to the diversity receiver of the present invention,
Since the amount of attenuation in the variable attenuator is controlled based on the correlation output of the demodulated baseband signal, it is less likely to be affected by noise components, the reliability of antenna selection is substantially improved, and stable diversity control is performed. Can be done.

In the diversity receiver of the present invention,
The attenuation amount control means detects the peak level of the correlation output detected when one attenuation amount in the variable attenuation means is controlled to the minimum during the period corresponding to the guard interval section during the period corresponding to the immediately preceding guard interval section. When the peak level of the correlation output is higher than the peak level, it is desirable that the attenuation amount is sequentially changed stepwise to the minimum in each period corresponding to the guard interval section that continues from the maximum.

In the diversity receiver of the present invention,
The attenuation amount control means detects the peak level of the correlation output detected when one attenuation amount in the variable attenuation means is controlled to the minimum during the period corresponding to the guard interval section during the period corresponding to the immediately preceding guard interval section. When it is lower than the peak level of the correlation output, it is desirable to return the maximum attenuation amount from the effective symbol section following the period corresponding to the guard interval section when the attenuation amount is minimized.

In the diversity receiver of the present invention,
The attenuation amount control means detects the peak level of the correlation output detected when one attenuation amount in the variable attenuation means is controlled to the maximum during the period corresponding to the guard interval section during the period corresponding to the immediately preceding guard interval section. When the level of the correlation output is higher than the peak level, it is desirable that the attenuation amount is sequentially changed stepwise to the maximum amount in each period corresponding to the guard interval section from the minimum.

In the diversity receiver of the present invention,
The attenuation amount control means detects the peak level of the correlation output detected when one attenuation amount in the variable attenuation means is controlled to the maximum during the period corresponding to the guard interval section during the period corresponding to the immediately preceding guard interval section. When it is lower than the peak level of the correlation output, it is desirable to return the attenuation amount to the minimum from the effective symbol section following the period corresponding to the guard interval section when the attenuation amount is minimized.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION A diversity receiver according to the present invention will be described below with reference to an embodiment.

FIG. 1 is a block diagram showing the configuration of a diversity receiver according to an embodiment of the present invention, and FIG.
In order to avoid redundant description with the diversity receiver B shown in FIG. 2, in the diversity receiver A according to the embodiment of the present invention, the same components as those of the diversity receiver B are designated by the same reference numerals, and The description is omitted.

The diversity receiver A has an antenna 1,
2, 3, 4, low noise amplifiers 5, 6, 7, 8, variable attenuators 9, 10, 11, 12, mixer 13, tuner 14, A
D converter 15, quadrature detector 16, effective symbol extraction circuit 17, FFT circuit 18, demapper 19, guard correlator 2
0, a timing recovery circuit 21 is provided, which operates in the same manner as in the diversity receiver B.

Further, the diversity receiver A is provided with a diversity control circuit 22 instead of the diversity control circuit 25, and the correlation output CORR output from the guard correlator 20 and the timing signal (FFT-WINDOW).
W) is supplied to the diversity control circuit 22, and an attenuation amount control signal for controlling the attenuation amount of the variable attenuators 9, 10, 11, 12 from the diversity control circuit 22 based on the correlation output CORR and the timing signal (FFT-WINDOW). CONT1, CONT2, CONT3, and CONT4 are sent to the variable attenuators 9, 10, 11, and 12, respectively,
The variable attenuators 9, 10, 11, 1 so that the output level of the mixer 13, that is, the combined reception signal level becomes high.
Control the amount of attenuation of 2.

The operation of the diversity control circuit 22 will be described with reference to FIG. 2, FIG. 3, FIG. 4, and FIG.
This will be described with reference to the timing chart shown in FIG.

In the diversity receiver A, as in the case of the diversity receiver B, the timing signal (FFT
-WINDOW) indicates the period corresponding to the effective symbol section when the potential is high, and the period corresponding to the guard interval section when the potential is low. Attenuation control signal CON
T1 is a signal for controlling the amount of attenuation of the variable attenuator 9, and the amount of attenuation is controlled to 0 when the level of the amount of attenuation control signal CONT1 is maximum, and is the amount of attenuation when the level of the amount of attenuation control signal CONT1 is minimum. Is the maximum. Attenuation control signal CO
The case of NT2, 3, and 4 is the same as that of the attenuation amount control signal CONT1.

Here, instead of the case of the diversity control circuit 25, the diversity control circuit 22 determines whether or not the reception condition is improved by the power signal (RX-PO).
The correlation output CORR is used instead of WER). In the diversity control circuit 22, the timing signal (FFT-W
(INDOW) is at a low potential, that is, during the period corresponding to the interval of the guard interval.
Changing the attenuation amounts of 1 and 12 is the same as in the diversity control circuit 25.

In FIG. 2, in order to prevent the input of the mixer 13 from disappearing, at least one of the variable attenuators 10, 11 and 12 is set to 0, and the initial state is set to 0. The level of the control signal CONT1 is minimum, that is, the attenuation amount of the variable attenuator 9 is maximum. Here, in order to evaluate the signal received by the antenna 1,
In the section where the timing signal (FFT-WINDOW) is at a low potential (see FIG. 2A), the attenuation control signal CONT1
Of the variable attenuator 9 (see FIG. 2B).
The attenuation of is set to 0.

As a result, the signal received by the antenna 1 is also combined by the mixer 13 and input to the tuner 14. At this time, in FIG. 2, the peak level of the correlation output CORR is higher than that of the previous correlation output CORR. The figure also shows the case where the temperature also rises (see FIG. 2 (c)).
In this case, if the mixer 13 combines the signals received by the antenna 1 and combines them, the output level of the mixer 13 increases, and it is determined that the reception condition is improved. In order to avoid the change, the level of the attenuation control signal CONT1 is temporarily returned to the minimum at the timing when the timing signal (FFT-WINDOW) becomes high potential, and thereafter, as shown by the arrow in FIG. The level of the attenuation amount control signal CONT1 is increased stepwise until the maximum level in a section where FFT-WINDOW) is at a low potential.

In the case of FIG. 3, the initial state of the receiver is shown in FIG.
However, the timing signal (FFT-WI
In the section where NDOW) becomes low potential (see FIG. 3A),
Maximize the level of the attenuation control signal CONT1 (see FIG.
FIG. 3B shows a case where the level of the correlation output CORR is lowered by setting the attenuation amount of the variable attenuator 13 to 0 (see FIG. 3C).

In this case, it is considered that the level of the output signal of the mixer 13 is lowered by combining the signals received by the antenna 1 in the mixer 13, and the peak level of the correlation output CORR is lowered, Since it is determined that the reception conditions have deteriorated, the timing signal (FF
The level of the attenuation amount control signal CONT1 is returned to the minimum at the timing when (T-WINDOW) becomes high potential (FIG. 3 (b)).
reference).

When the attenuation amount of the variable attenuator 9 is set to 0 in the period corresponding to the guard interval section in the state where the attenuation amount of the variable attenuator 9 is maximum as in the case shown in FIG. When the peak level of the correlation output CORR in the period corresponding to the next guard interval section is higher than the peak level of the correlation output in the period corresponding to the preceding guard interval section, it corresponds to the next guard interval section. The maximum amount of attenuation of the variable attenuator 9 is achieved during the period corresponding to the guard interval section following the above period, that is, the original amount is restored, and the attenuation amount of the variable attenuator 9 is sequentially reduced to 0 during the period corresponding to the subsequent guard interval section. It will be reduced stepwise.
This makes it possible to set the amount of attenuation that can be stably received.

Further, as in the case shown in FIG. 3, the attenuation amount of the variable attenuator 9 is set to 0 in the period corresponding to the guard interval section in the state where the attenuation amount of the variable attenuator 9 is maximum. At this time, when the peak level of the correlation output CORR during the next guard interval period is lower than the peak level of the correlation output during the period corresponding to the preceding guard interval section, the variable attenuator 9
The attenuation amount of the variable attenuator 9 is maximized from the period corresponding to the subsequent guard interval section when the attenuation amount of 0 is set to 0, that is, the original amount is restored. This makes it possible to set the amount of attenuation that can be stably received.

In the case of FIG. 4 as well, the variable attenuators 10, 11, 1 are used.
Among the two, at least one or more have the attenuation amount of 0, and the level of the attenuation amount control signal CONT1 is maximum, that is, the attenuation amount of the variable attenuator 9 is 0 in the initial state. Here, in order to evaluate the signal received by the antenna 1, the attenuation control signal C is applied in a section where the timing signal (FFT-WINDOW) has a low potential (see FIG. 4A).
The level of ONT1 is minimized (see FIG. 4B), and the attenuation amount of the variable attenuator 9 is maximized.

As a result, the signals received by the antenna 1 are attenuated, combined by the mixer 13 and input to the tuner 14. As a result, in FIG. 4, the correlation output C
It shows a case where the peak level of the ORR is increased (see FIG. 4 (c)). In this case, if the signal received by the antenna 1 is attenuated, it is determined that the level of the correlation output CORR rises and the reception condition is improved, and then the timing signal (FFT-WINDOW) becomes high potential once. The level of the attenuation amount control signal CONT1 is returned to the maximum level (see FIG. 4B), and thereafter, as shown by the arrow in FIG. 4, the timing signal (FFT-WINDOW) of the attenuation amount control signal CONT1 is in the low potential section. The level is changed stepwise until the level becomes minimum (see FIG. 4B).

In the case of FIG. 5, the initial state is the same as that of FIG. 4, but the timing signal (FFT-WINDOW
By setting the level of the attenuation amount control signal CONT1 to the minimum level (see FIG. 5B) and the attenuation amount of the variable attenuator 9 to the maximum level in the section where W) becomes a low potential (see FIG. 5A). This shows a case where the peak level of the correlation output CORR has decreased (see FIG. 5 (c)). In this case, it is considered that the level of the output signal of the mixer 13 is decreased by combining the signals received by the antenna 1 in the mixer 13, and the peak level of the correlation output CORR is decreased, and the reception condition is Since it is determined that the timing signal (FFT-WINDOW) becomes high potential, the level of the attenuation amount control signal CONT1 is returned to the maximum (FIG. 5).
(See (b)).

When the attenuation amount of the variable attenuator 9 is maximized in the period corresponding to the guard interval section in the state where the attenuation amount of the variable attenuator 9 is 0 as in the case shown in FIG. When the peak level of the correlation output CORR in the next guard interval period is higher than the peak level of the correlation output in the period corresponding to the preceding guard interval section, the peak level of the correlation output CORR follows the period corresponding to the next guard interval section. The attenuation amount of the variable attenuator 9 is set to 0 in the period corresponding to the guard interval section,
That is, the variable amount is restored to the original value, and the attenuation amount of the variable attenuator 9 is increased stepwise to the maximum in the period corresponding to the subsequent guard interval section. This makes it possible to set the amount of attenuation that can be stably received.

Further, as in the case shown in FIG. 5, the attenuation amount of the variable attenuator 9 is maximized in the period corresponding to the guard interval section when the attenuation amount of the variable attenuator 9 is 0. At this time, when the peak level of the correlation output CORR in the period corresponding to the next guard interval section is lower than the peak level of the correlation output in the period corresponding to the preceding guard interval section, the attenuation of the variable attenuator 9 is reduced. The attenuation amount of the variable attenuator 9 is set to 0 from the period corresponding to the guard interval section that follows when the amount is maximized, that is, the original amount is restored. This makes it possible to set the amount of attenuation that can be stably received.

In this way, the variable attenuators 9, 10, 1 are maintained with the attenuation amount of one or more variable attenuators being maintained at 0.
The attenuation amounts of 1 and 12 are sequentially controlled to control the signal level input to the tuner 14 to be maximum.

As described above, the attenuation amount of the variable attenuator is controlled so that the peak level of the guard correlation output CORR is referred to detect the signal level, so that it is less susceptible to the noise component and stable diversity is achieved. Can receive.

[0050]

As described above, according to the diversity receiver of the present invention, the reliability of substantial selection of the antenna is improved, and stable diversity reception can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a diversity receiver according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the diversity receiver according to the embodiment of the present invention.

FIG. 3 is a timing chart for explaining the operation of the diversity receiver according to the embodiment of the present invention.

FIG. 4 is a timing chart for explaining the operation of the diversity receiver according to the embodiment of the present invention.

FIG. 5 is a timing diagram for explaining the operation of the diversity receiver according to the embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional diversity receiver.

FIG. 7 is a timing diagram for explaining the operation of the conventional diversity receiver.

FIG. 8 is a timing chart for explaining the operation of the conventional diversity receiver.

FIG. 9 is a timing diagram for explaining the operation of the conventional diversity receiver.

FIG. 10 is a timing diagram for explaining the operation of the conventional diversity receiver.

[Explanation of symbols]

9-12 Variable attenuator 13 Mixer 14 Tuner 15 AD converter 16 Quadrature detector 17 Effective symbol extraction circuit 18 FFT circuit 20 Guard correlator 21 Timing recovery circuit 22 Diversity control circuit

[Procedure amendment]

[Submission date] April 3, 2002 (2002.4.3)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

Diversity receivers for receiving OFDM modulated broadcast signals such as digital terrestrial television broadcast signals are known. There is a conventional diversity receiver of this type proposed by the applicant (Japanese Patent Application No. 2000-3800005 ).

Claims (5)

[Claims] 1. A diversity receiver having a plurality of antennas for receiving an OFDM-modulated signal in which one symbol period includes an effective symbol section and a guard interval section, each receiving signal from each of the plurality of antennas. The variable attenuating means for attenuating, the demodulating means for synthesizing the outputs from the variable attenuating means, demodulating and outputting the synthesized output, and the correlation of the period corresponding to the guard interval section of the baseband signal obtained by the demodulating means are detected. And a damping amount control means for changing the damping amount of the variable damping means in the period corresponding to the guard interval section based on whether or not the peak level of the correlation output in the period corresponding to the guard interval section has increased. A diversity receiver, which is provided with. 2. The diversity receiver according to claim 1, wherein the attenuation amount control means detects the correlation output detected when one attenuation amount in the variable attenuation means is controlled to a minimum during a period corresponding to the guard interval section. When the peak level is higher than the peak level of the correlation output detected in the period corresponding to the immediately preceding guard interval section, the attenuation amount is sequentially stepwise from the maximum to the subsequent guard interval section. Diversity receiver characterized by changing to a minimum. 3. The diversity receiver according to claim 1, wherein the attenuation amount control means detects the correlation output detected when one attenuation amount in the variable attenuation means is controlled to a minimum during the period corresponding to the guard interval section. When the peak level is lower than the peak level of the correlation output detected in the period corresponding to the immediately preceding guard interval period, the effective symbol period following the period corresponding to the guard interval period when the attenuation is minimized Diversity receiver characterized by returning the maximum attenuation. 4. The diversity receiver according to claim 1, wherein the attenuation amount control means detects the correlation output detected when one attenuation amount in the variable attenuation means is controlled to a maximum during a period corresponding to the guard interval section. When the peak level is higher than the peak level of the correlation output detected in the period corresponding to the immediately preceding guard interval section, the attenuation amount is sequentially stepwise for each period corresponding to the guard interval section starting from the minimum. Diversity receiver characterized by changing up to maximum. 5. The diversity receiver according to claim 1, wherein the attenuation amount control means detects the correlation output detected when one attenuation amount in the variable attenuation means is controlled to the maximum during a period corresponding to the guard interval section. When the peak level is lower than the peak level of the correlation output detected in the period corresponding to the immediately preceding guard interval period, the effective symbol period following the period corresponding to the guard interval period when the attenuation is minimized A diversity receiver characterized by reducing attenuation to a minimum.