JP2001156741A - Ofdm signal receiver and ofdm signal reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To demodulate data by automatically identifying a transmission mode where a transmission frame length is the same but a modulation bandwidth differs. SOLUTION: A reference phase signal data storage section 21 stores in advance data existing in a band not included in a band of a transmission mode with a narrow modulation bandwidth in a reference phase signal transmitted in a transmission mode with a wide modulation bandwidth. A correlation arithmetic processing section 20 executes a correlation arithmetic operation between data of the reference phase signal acquired from an FFT circuit 13 and data stored in the reference phase signal data storage section 21. A control circuit 18 discriminates whether or not there is any correlation between the data acquired from the FFT circuit 13 and data stored in the reference phase signal data, storage, section 21 on the basis of a result of the execution of the correlation arithmetic operation by the correlation arithmetic processing section 20 to identify the transmission mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an OFD for receiving and demodulating a signal transmitted by an orthogonal frequency division multiplex system.
The present invention relates to an M signal receiver, and more particularly, to an OFDM signal receiver that can automatically identify transmission modes having different modulation bandwidths and demodulate transmitted data.

[0002]

2. Description of the Related Art As a technology for digital broadcasting, I.
TU-R (International Telecommunication Union-Ra
diocommunication sector). 1114 Sys
DAB (Digital Audio Br) standardized by temA
oadcasting). In this DAB, an orthogonal frequency division multiplexing (Orthogonal Frequency Division M
ultiplex; OFDM. Hereinafter, it is called OFDM. ), And defines four transmission modes as shown in FIG. As shown in FIG. 5, in these transmission modes, the number of carriers and the frame length differ depending on the mode.

[0003] As an OFDM signal receiver for receiving a signal transmitted using one of a plurality of transmission modes and reproducing demodulated data, an OFDM signal receiver as shown in FIG. 6 is known. The OFDM signal receiver shown in FIG. 6 has four transmission mode signals shown in FIG. 5 and a mode IV-H in which the operation clock is halved by setting the transmission mode IV.
Receives ALF signal.

When the conventional OFDM signal receiver shown in FIG. 6 receives a mode I signal shown in FIG.
Specifies the modulation bandwidth of the received signal based on the band identification signal input from the outside, and switches the selectors 1 and 4 that operate in conjunction with each other according to the specified modulation bandwidth. As a result, the received intermediate frequency signal is
Alternatively, one of the bandpass filters 3 is filtered. Here, in order to receive a signal of mode I, which is a wideband transmission mode, the signal is filtered by the bandpass filter 3 for wideband.

The intermediate frequency signal whose band is limited by the band-pass filter 3 is supplied to mixers 5 and 6 and a local oscillator 7.
And a π / 2 phase shifter 8, a baseband I (In-phase) signal and a Q (Quadratu
re) converted to a signal. After this, the low-pass filter 9,
The I and Q signals whose aliasing noise has been suppressed by the ADC 10 are digitized by the ADCs 11 and 12, and then digitized by the FFs.
It is input to a T (Fast Fourier Transform) circuit 13 and subjected to fast Fourier transform.

[0006] The intermediate frequency signal filtered by the band pass filter 3 is also supplied to an envelope detector 14 and subjected to envelope detection.
It is converted to a value and sent to the control circuit 18. The control circuit 18
A non-signal section called a NULL symbol included in the signal received from the comparator 15 is detected, and the transmission frame length is specified from the period of the non-signal section.

For example, when the transmission frame length specified by the control circuit 18 is 96 ms, the transmission mode is set to the mode
Judge as I or Mode IV-HALF. Further, the modulation bandwidth of the received signal is defined by a band identification signal externally provided to the control circuit 18. Thereby, the control circuit 18 can specify the transmission mode of the received signal. The control circuit 18 defines the sampling frequency of the ADCs 11 and 12 according to the specified transmission mode,
The number of points when the FFT circuit 13 executes the fast Fourier transform is set. In this way, the baseband signal that has been subjected to the fast Fourier transform by the FFT circuit 13 is input to the delay detector 19, differentially decoded, and the transmission data is demodulated.

[0008]

In the above-mentioned conventional OFDM signal receiver, to distinguish signals in transmission modes having the same transmission frame length and different modulation bandwidths, such as mode I and mode IV-HALF, A signal (band identification signal) for selecting the modulation bandwidth of the received signal has to be supplied from the outside.

That is, a conventional OFDM signal receiver is:
Transmission modes with the same transmission frame length and different modulation bandwidths could not be automatically identified.

[0010] The present invention has been made in view of the above situation, and an OFD capable of automatically identifying transmission modes having different signal modulation bandwidths and demodulating transmission data.
It is an object to provide an M signal receiver.

[0011]

In order to achieve the above object, an OFDM signal receiver according to a first aspect of the present invention comprises an orthogonal frequency modulator having a plurality of transmission modes having the same transmission frame length and different modulation bandwidths. Receives the signal transmitted by the division multiplexing method, demodulates the data of the predetermined signal by performing a Fourier transform by converting it to a baseband signal,
A correlation operation is performed with the data of the predetermined signal stored in advance to determine whether or not there is a correlation, the transmission mode is identified based on the determination result, and the data is demodulated by a reception operation according to the identified transmission mode. To be characterized.

According to the present invention, data transmitted and received by the orthogonal frequency division multiplexing system having a plurality of transmission modes having the same transmission frame length and different modulation bandwidths is demodulated, And demodulating the data by switching the receiving operation according to whether or not there is a correlation. This makes it possible to automatically identify transmission modes having the same transmission frame but different modulation bandwidths to demodulate transmission data.

An OFD according to a second aspect of the present invention
The M signal receiver receives a signal transmitted by an orthogonal frequency division multiplexing system having a plurality of transmission modes having the same transmission frame length and different modulation bandwidths, identifies the transmission mode, and demodulates data. A demodulation means for receiving the transmitted signal and demodulating the data; and a transmission mode having a same transmission frame length and a different modulation bandwidth, and a predetermined signal transmitted in a transmission mode having a wide modulation bandwidth. Data storage means for storing data in advance, data of a predetermined signal demodulated as a setting for receiving the signal of the transmission mode having a wide modulation bandwidth with the demodulation means being stored in the data storage means A correlation calculation execution unit for performing a correlation calculation with the data, and determining whether or not there is a correlation from the calculation result of the correlation calculation execution unit. Data demodulation is continued as a setting for receiving a signal in a transmission mode having a wide modulation bandwidth, and if it is determined that there is no correlation, the demodulation means is controlled to receive a signal in a transmission mode having a narrow modulation bandwidth. Operation control means for demodulating data as setting for performing the operation.

According to the present invention, the data storage means stores in advance the data of the predetermined signal transmitted in the transmission mode having a wide modulation bandwidth, and the correlation operation executing means sets the demodulation means to the demodulation means. As a setting for receiving a signal in a wide transmission mode, a correlation operation with data of a demodulated predetermined signal is executed. The operation control means can determine whether or not there is a correlation from the calculation result of the correlation calculation execution means, identify the transmission mode, and demodulate the data by setting the demodulation means according to the transmission mode. This makes it possible to automatically identify transmission modes having the same transmission frame length and different modulation bandwidths to demodulate transmission data.

The data storage means stores in advance data of a predetermined signal transmitted in a transmission mode having a wide modulation bandwidth and which is in a band not included in a band of a transmission mode having a narrow modulation bandwidth. Correlation calculation execution means, among the data of the predetermined signal demodulated by the demodulation means, the modulation bandwidth is in a band not included in the narrow transmission mode band, and the data stored in the data storage means It is desirable to execute the correlation operation of This makes it possible to reduce the amount of calculation of the correlation operation executed by the correlation operation executing means, and to identify the transmission mode more quickly.

More specifically, the demodulating means includes first filtering means for limiting a band of a received signal to demodulate data from a transmission mode signal having a wide modulation bandwidth, and a narrow modulation bandwidth. A second filtering means for limiting a band of a received signal in order to demodulate data from a signal in a transmission mode; and selecting one of the first filtering means and the second filtering means to select a received signal. Selection means for filtering
A quadrature detection unit for receiving a signal filtered by one of the first filtering unit and the second filtering unit and performing quadrature detection, and samples and digitizes a signal quadrature detected by the quadrature detection unit Sampling means; and a Fourier transform executing means for executing a Fourier transform based on the signal digitized by the sampling means, wherein the operation control means identifies transmission modes having the same transmission frame length and different modulation bandwidths. At this time, the first filtering means is selected by the selection means, and a sampling clock signal set to a frequency for demodulating data from a signal in a transmission mode having a wide modulation bandwidth is supplied to the sampling means, The number of points of the Fourier transform executed by the transform executing means Set to a value for adjusting bandwidth to demodulate the data from a wide transmission mode of the signal, it is desirable to demodulate the data.

When the operation control means determines that there is no correlation from the calculation result of the correlation calculation execution means, the operation control means causes the selection means to select the second filtering means, and causes the sampling means to change the modulation bandwidth. A sampling clock signal set to a frequency for demodulating data from the signal in the narrow transmission mode is supplied, and the number of points of the Fourier transform executed by the Fourier transform execution unit is changed from the signal in the transmission mode having a narrow modulation bandwidth to the data. It is desirable to demodulate data by setting a value for demodulation.

[0018] Further, the demodulation means includes an envelope detection means for receiving the signal filtered by one of the first filtering means and the second filtering means and performing envelope detection, and the envelope detection means. Binarizing means for binarizing the signal detected by the method, wherein the operation control means specifies a period and a length of a non-signal section included in the signal binarized by the binarizing means. Then, the transmission mode may be identified on the basis of the specified period and length of the no-signal section, and the demodulation means may demodulate the data with settings according to the transmission mode.

An OFD according to a third aspect of the present invention
The M signal receiving method is to receive a signal transmitted by an orthogonal frequency division multiplexing method having a plurality of transmission modes having the same transmission frame length and different modulation bandwidths, convert the signal to a baseband signal, and perform a Fourier transform. Demodulates the data of the predetermined signal, performs a correlation operation with the data of the predetermined signal stored in advance, determines whether or not there is a correlation, identifies the transmission mode based on the determination result, and identifies the identified transmission mode. And demodulates data by a receiving operation corresponding to.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an OFDM signal receiver according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an OF according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration of a DM signal receiver 100. FIG. 1 shows an OFDM signal receiver 10 according to an embodiment of the present invention.
At 0, the same components as those of the conventional OFDM signal receiver shown in FIG. 6 are denoted by the same reference numerals.

An OFDM signal receiver 100 according to an embodiment of the present invention has an ITU-R (Intern
ational Telecommunication Union-Radiocommunication
sector) BS. 1114 Signals of modes I to IV standardized by System A, and mode IV-HAL which is a mode in which the operation clock is halved by setting mode IV
F signal can be received. Here, modes I to IV
Has a modulation bandwidth of 1.536 MHz. On the other hand, the mode IV-HALF signal has a modulation bandwidth of 768 kHz.
z.

In order to receive such a signal, the OFDM signal receiver 100 according to the embodiment of the present invention
As shown in FIG. 3, selectors 1, 4, bandpass filters 2, 3, mixers 5, 6, local oscillator 7, π / 2 phase shifter 8, low-pass filters 9, 10, and ADC (Anal
og / Digital Converter) 11 and 12, and FFT (FastFo)
urier Transform) circuit 13, an envelope detector 14,
A comparator 15, a system clock 16, a frequency divider 17
, A control circuit 18 and a delay detector 19.

The selectors 1 and 4 are composed of semiconductor switches and the like, switch connection destinations in conjunction with the control of the control circuit 18 and switch the received intermediate frequency signal to one of the band-pass filter 2 and the band-pass filter 3. Let it be filtered.

The band pass filters 2 and 3 are band limiting filters that pass only a predetermined band of the received intermediate frequency signal. Here, the bandpass filter 2 and the bandpass filter 3 have different signal bandwidths from each other. For example, bandpass filter 2
Is a filter for a narrow band having a pass band width of 768 kHz, and the band-pass filter 3 has a pass band width of 1.53
This is a 6 MHz wide band filter.

The mixer 5 is for multiplying a signal received from the band-pass filter 2 or the band-pass filter 3 via the selector 4 with a local oscillation signal of a constant frequency received from the local oscillator 7. The mixer 5 sends the signal obtained by the multiplication to the low-pass filter 9.

The mixer 6 includes a signal received from the bandpass filter 2 or the bandpass filter 3 via the selector 4 and a local oscillation signal generated by the local oscillator 7 and adjusted in phase by the π / 2 phase shifter 8. Is to be multiplied by The mixer 6 sends the signal obtained by the multiplication to the low-pass filter 10.

The local oscillator 7 is a local oscillation circuit that generates a local oscillation signal having a constant frequency.

The π / 2 phase shifter 8 shifts the phase of the local oscillation signal received from the local oscillator 7 by π / 2, and shifts the phase of the local oscillation signal supplied to the mixers 5 and 6. By making them different by π / 2, quadrature detection is made possible.

As described above, the mixers 5 and 6, the local oscillator 7 and the π / 2 phase shifter 8 constitute a quadrature demodulator.

The low-pass filters 9 and 10 are low-pass circuits that pass only the low-frequency components of the signals received from the mixers 5 and 6, respectively, and remove the aliasing noise of the baseband signal and supply it to the ADCs 11 and 12. It is for.

The ADCs 11 and 12 are for digitizing the baseband signals received from the low-pass filters 9 and 10, respectively, and supplying them to the FFT circuit 13.

The FFT circuit 13 receives baseband signals from the ADCs 11 and 12 and performs a fast Fourier transform.
This is for demodulating the data sent from the transmitting side. The FFT circuit 13 outputs the demodulated data to the delay detector 1
Send to 9. Further, the FFT circuit 13 outputs the ITU-R BS. 1114 System A
Reference phase signal (Phase Reference Sy)
mbol; PRS) is sent to the control circuit 18.

The envelope detector 14 is for performing envelope detection on the intermediate frequency signal received from the bandpass filter 2 or 3 via the selector 4. The envelope detector 14 sends a signal obtained by the envelope detection to the comparator 15.

The comparator 15 binarizes the signal received from the envelope detector 14, and sends the binarized signal to the control circuit 18.

The system clock 16 is an oscillating circuit for generating a clock signal defining the operation timing of the control circuit 18.

The frequency divider 17 divides the frequency of the clock signal generated by the system clock 16 to generate sampling clock signals for the ADCs 11 and 12.
Here, the frequency divider 17 changes the frequency division ratio under the control of the control circuit 18. The clock signal divided by the divider 17 is supplied to the ADCs 11 and 12 via the control circuit 18.

The control circuit 18 has a ROM (Read Only Memory)
ry) and 1 with RAM (Random Access Memory)
It is composed of a chip microcomputer and the like, and controls the operation of the entire OFDM signal receiver 100. In addition, the control circuit 18 determines a correlation operation processing unit 20 in order to identify transmission modes having the same transmission frame length and different modulation bandwidths, for example, mode I and mode IV-HALF shown in FIG.
And a reference phase signal data storage unit 21.

The correlation operation processing section 20 executes a correlation operation between the data of the reference phase signal portion received from the FFT circuit 13 and the data stored in the reference phase signal data storage section 21. That is, the correlation operation processing unit 20
Calculates a correlation between data demodulated from the received signal and data corresponding to a predetermined band of the reference phase signal.

Here, for example, the band of the reference phase signal in the transmission mode of mode I and the band of the reference phase signal in the mode IV-HALF have a relationship as shown in FIG. Band b2 is a band used by both mode I and mode IV-HALF, and band b
1 and b3 are bands used only by mode I.

The correlation operation processing section 20 includes, among the reference phase signals in the broadband transmission mode (for example, mode I), data corresponding to the bands b1 and b3 shown in FIG. Among the signals, the correlation with the data transmitted by the signals of the bands b1 and b3 is obtained. When it is determined that there is a correlation from the result of the correlation operation performed by the correlation operation processing unit 20, the control circuit 18 sets the transmission mode to mode I.
Is specified. On the other hand, if it is determined that there is no correlation from the result of the correlation operation performed by the correlation operation processing unit 20, the control circuit 18 determines that the transmission mode is the mode IV-HALF.

The reference phase signal data storage section 21 stores the reference phase signals of the broadband transmission mode (eg, mode I).
This is for preliminarily storing data corresponding to the bands b1 and b3 in FIG. That is, the reference phase signal data storage unit 21 previously stores data of a reference phase signal transmitted in the transmission mode having a wide modulation bandwidth in a band not included in the band of the transmission mode having a small modulation bandwidth. I remember. Here, the data of the reference phase signal portion is
A value is determined for each transmission mode, and the reference phase signal data storage unit 21 stores this data in advance.

The delay detector 19 is for differentially decoding and demodulating the signal subjected to the fast Fourier transform by the FFT circuit 13.

Hereinafter, an OF according to an embodiment of the present invention will be described.
The operation of the DM signal receiver 100 will be described. This OFDM
The signal receiver 100 is a receiver that can automatically identify two transmission modes having the same transmission frame length and different modulation bandwidths and demodulate the transmitted data.

The OFDM signal receiver 100 has a mode I-IV signal as shown in FIG. 2 and a mode IV-HALF which is a mode in which the operation clock is halved by setting the mode IV.
Can be received. When receiving such a signal, the OFDM signal receiver 100 executes a mode determination reception process shown in the flowchart of FIG.

When the mode discriminating reception process is started, the control circuit 18 sends a switching signal to the selectors 1 and 4 to input the received intermediate frequency signal to the bandpass filter 2 for narrow band. The band-pass filter 2 filters the received intermediate frequency signal to limit the band, and
Are sent to the mixers 5 and 6 and the envelope detector 14 (step S1). In this way, by performing the filtering by the band-pass filter 2 for the narrow band, the influence of noise is reduced, and the transmission mode can be reliably determined.

The envelope detector 14 performs envelope detection on the intermediate frequency signal received from the bandpass filter 2 via the selector 4 and sends the obtained signal to the comparator 15. Comparator 1
5 binarizes the signal received from the envelope detector 14 and sends it to the control circuit 18.

The control circuit 18 detects a non-signal section called a NULL symbol included in the transmission signal from the signal received from the comparator 15, and specifies the transmission frame length from the period of the non-signal section (step S2). ).

The control circuit 18 determines the transmission mode from the specified transmission frame length (step S3). For example, the control circuit 18 determines that the specified transmission frame length is 24 m
If the transmission mode is specified, it is determined that the transmission mode is mode II or mode III. On the other hand, when the control circuit 18 specifies that the specified transmission frame length is 48 ms,
It is determined that the transmission mode is mode IV. When the control circuit 18 specifies that the specified transmission frame length is 96 ms, the transmission mode is set to mode I or mode IV-HALF.
Is determined.

When the control circuit 18 determines that the transmission mode is mode II or mode III (mode III or III, mode IV in step S3), the control circuit 18 executes
Further, it is determined whether the transmission mode is mode II or mode III. That is, the control circuit 18 controls the comparator 15
, A NULL symbol included in the transmission signal is detected from the signal received from the base station, and a guard interval is specified based on the length of the NULL symbol. The control circuit 18 determines whether the transmission mode is mode II or mode III based on the specified guard interval. Thereafter, the control circuit 18 sends the ADCs 11, 1 according to the determined transmission mode.
2, the frequency of the sampling clock signal and the number of points of the fast Fourier transform executed by the FFT circuit 13 are set. At this time, the control circuit 18 operates the selectors 1 and 4
, A switching signal for instructing the switching of the connection destination, and the received intermediate frequency signal is transmitted to the band-pass filter 3 for a wide band.
To demodulate the transmission data (step S4).

Also, when the control circuit 18 determines that the transmission mode is the mode IV, the control circuit 18 performs A
The frequency of the sampling clock signals of the DCs 11 and 12 and the number of points of the fast Fourier transform executed by the FFT circuit 13 are set, and the connection destination of the selectors 1 and 4 is switched to the band-pass filter 3 for wide band to demodulate the transmission data. .

On the other hand, when the control circuit 18 determines that the transmission mode is mode I or mode IV-HALF (mode I or IV-HALF in step S3), it instructs the selectors 1 and 4 to switch the connection destination. A switching signal is sent, and the received intermediate frequency signal is input to the band-pass filter 3.
That is, the control circuit 18 causes the bandpass filter 3 for wide band to filter the received intermediate frequency signal (step S5).

At this time, the control circuit 18 controls the frequency divider 17 to change the frequency of the sampling clock signal supplied to the ADCs 11 and 12 to a value for receiving a signal whose transmission mode is mode I (wide band). Set. At this time, the control circuit 18 sets the number of points of the fast Fourier transform executed by the FFT circuit 13 to a value for receiving a signal whose transmission mode is mode I.

The intermediate frequency signal filtered by the band pass filter 3 is sent to the mixers 5 and 6 and the envelope detector 14 via the selector 4.

Mixers 5 and 6, local oscillator 7, π / 2
The quadrature demodulator including the phase shifter 8 converts the intermediate frequency signal received from the bandpass filter 3 via the selector 4 into a baseband I (In-phase) signal and a Q (Quad) signal.
rature (orthogonal) signal and convert them into ADC11,
Send to 12. The ADCs 11 and 12 digitize the baseband signal and send it to the FFT circuit 13.

The FFT circuit 13 receives the digitized baseband I and Q signals from the ADCs 11 and 12 and performs a fast Fourier transform. The FFT circuit 13
The data obtained as a result of the fast Fourier transform is sent to the differential detector 19.

At this time, the control circuit 18 controls the FFT circuit 13
Acquires the data of the reference phase signal portion from the data obtained as a result of executing the fast Fourier transform, and causes the correlation operation processing unit 20 to execute the correlation operation.

The correlation operation processing section 20 performs a correlation operation between the data of the reference phase signal obtained from the FFT circuit 13 and the data stored in the reference phase signal data storage section 21 (step S6).

The control circuit 18 has a correlation between the data obtained from the FFT circuit 13 and the data stored in the reference phase signal data storage unit 21 based on the result of the correlation operation performed by the correlation operation processing unit 20. It is determined whether or not this is the case (step S7).

Here, the range in which the correlation calculation processing section 20 executes the correlation calculation is a portion corresponding to the bands b1 and b3 shown in FIG. 3. When the data transmitted in the transmission mode I is received, the reference phase signal The result that there is a correlation with the data stored in the data storage unit 21 is obtained. On the other hand, when the data transmitted in the transmission mode IV-HALF is received, a result indicating that there is no correlation with the data stored in the reference phase signal data storage unit 21 is obtained.

If the control circuit 18 determines that there is a correlation (YES in step S7), the transmission mode is set to mode I,
That is, it is assumed that the transmission mode is the wideband (step S
8) The receiving operation is continued with the same setting (step S9). Here, the connection destinations of the selectors 1 and 4, ADC1
The frequency of the sampling clock signal supplied to the first and the second 12 and the number of points of the fast Fourier transform executed by the FFT circuit 13 are set to receive a signal in the transmission mode of mode I. Therefore, by continuing the reception operation as it is, it is possible to demodulate the data transmitted with the transmission mode being mode I.

On the other hand, if the control circuit 18 determines that there is no correlation (NO in step S7), the transmission mode is set to the mode
It is assumed that the transmission mode is IV-HALF, that is, a narrowband transmission mode (step S10). The control circuit 18 includes selectors 1 and 4
A switching signal for instructing switching of the connection destination is sent to the bandpass filter 2 for narrow band to filter the received intermediate frequency signal (step S11).

At this time, the control circuit 18 controls the frequency divider 17 to change the frequency of the sampling clock signal supplied to the ADCs 11 and 12 to a value for receiving a mode IV-HALF (narrow band) signal. Set. At this time, the control circuit 18 sets the number of points of the fast Fourier transform executed by the FFT circuit 13 to a value for receiving the signal of the mode IV-HALF. As described above, the control circuit 18 operates in the mode IV-HAL
By making settings to receive the F signal, the mode IV-
The operation for receiving the HALF is started, and the data transmitted in the transmission mode of the mode IV-HALF can be demodulated (step S12).

As described above, according to the present invention,
A part of the reference phase signal transmitted in the wideband transmission mode among a plurality of transmission modes having the same transmission frame length and different modulation bandwidths is stored in the reference phase signal data storage unit 21 in advance. Then, when the FFT circuit 13 demodulates the data corresponding to the reference phase signal, it determines whether there is a correlation between this data and the data stored in the reference phase signal data storage unit 21. This makes it possible to automatically identify a plurality of transmission modes having the same transmission frame length and different modulation bandwidths, perform settings according to the transmission modes, and demodulate the transmitted data.

The present invention is not limited to the above embodiment, and various modifications and applications are possible. For example, in the above embodiment, BS. 1114 Sys
The mode I-IV and the mode IV-HALF signals standardized by temA have been described as receiving and demodulating transmitted data, but the present invention is not limited to this. That is, when demodulating transmitted data in an arbitrary communication system using a plurality of transmission modes having the same transmission frame length of transmission frames formed by data transmitted using OFDM and having different bandwidths. Can be applied.

The range in which the correlation operation processing section 20 executes the correlation operation is not limited to the bands b1 and b3 shown in FIG.
The range of the band b2 may be included. Further, the signal for obtaining the correlation is not limited to the reference phase signal, and may be any signal as long as the signal can identify the transmission mode.

[0067]

As described above, according to the present invention, transmission of a received signal is performed by executing a correlation operation between data of a predetermined signal transmitted in a predetermined band and data stored in advance. The mode can be automatically identified.
This makes it possible to automatically identify transmission modes having the same transmission frame length and different bandwidths, and demodulate the transmitted data.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a transmission mode of a signal received by an OFDM signal receiver.

FIG. 3 is a diagram for explaining a range in which a correlation calculation processing unit executes a correlation calculation.

FIG. 4 is a flowchart illustrating a mode determination reception process.

FIG. 5 is a diagram showing a transmission mode defined by DAB.

FIG. 6 is a diagram showing a configuration of a conventional OFDM signal receiver.

[Explanation of symbols]

 1,4 selector 2,3 band pass filter 5,6 mixer 7 local oscillator 8 π / 2 phase shifter 9,10 low pass filter 11,12 ADC 13 FFT circuit 14 envelope detector 15 comparator 16 system clock 17 frequency division Unit 18 control circuit 19 delay detector 20 correlation operation processing unit 21 reference phase signal data storage unit 100 OFDM signal receiver b1, b2, b3 band

Claims (7)

[Claims] 1. A signal transmitted by an orthogonal frequency division multiplexing system having a plurality of transmission modes having the same transmission frame length and different modulation bandwidths is received, converted to a baseband signal, and subjected to Fourier transform. The data of the predetermined signal is demodulated, a correlation operation is performed with the data of the predetermined signal stored in advance to determine whether there is a correlation, the transmission mode is identified based on the determination result, and the identified transmission mode is set. An OFDM signal receiver, which demodulates data by a corresponding receiving operation. 2. An OFDM signal receiver for receiving a signal transmitted by an orthogonal frequency division multiplexing system having a plurality of transmission modes having the same transmission frame length and different modulation bandwidths, identifying the transmission mode, and demodulating data. A demodulating means for receiving a transmitted signal and demodulating data, and a transmission mode having a wide modulation bandwidth among transmission modes having the same transmission frame length and different modulation bandwidths. Data storage means for storing signal data in advance; data for a predetermined signal demodulated as a setting for receiving a signal in a transmission mode having a wide modulation bandwidth with the demodulation means; and data stored in the data storage means. A correlation calculation executing means for performing a correlation calculation with the data, and determining whether or not there is a correlation from the calculation result of the correlation calculation executing means. Data demodulation is continued as a setting for receiving a signal of a transmission mode having a wide modulation bandwidth without changing the demodulation means, and when it is determined that there is no correlation, the demodulation means is controlled to control the transmission mode having a narrow modulation bandwidth. And an operation control means for demodulating data as a setting for receiving the signal. 3. The data storage means stores, in advance, data of a predetermined signal transmitted in a transmission mode having a wide modulation bandwidth in a band not included in a band of a transmission mode having a narrow modulation bandwidth. The correlation calculation execution means stores the data of the predetermined signal demodulated by the demodulation means in a band not included in the transmission mode band having a narrow modulation bandwidth and the data storage means. The OFDM signal receiver according to claim 2, wherein a correlation operation with data is performed. 4. The demodulation means includes: first filtering means for limiting a band of a received signal in order to demodulate data from a signal in a transmission mode having a wide modulation bandwidth; A second filtering unit for limiting a band of a received signal to demodulate data from the signal; and selecting one of the first filtering unit and the second filtering unit to filter the received signal. Selecting means; quadrature detection means for receiving a signal filtered by one of the first filtering means and the second filtering means to perform quadrature detection; sampling the signal quadrature detected by the quadrature detection means Sampling means for digitizing by means of And a Fourier transform executing means for executing a Fourier transform. The operation control means selects the first filtering means as the selecting means when identifying transmission modes having the same transmission frame length and different modulation bandwidths. Supplying a sampling clock signal set to a frequency for demodulating data from a signal in a transmission mode having a wide modulation bandwidth to the sampling means, and changing the number of points of Fourier transform executed by the Fourier transform execution means to a modulation band. 4. The OFDM signal receiver according to claim 2, wherein a value for demodulating data from a signal in a wide transmission mode is set to demodulate data. 5. The operation control means, when judging that there is no correlation from the calculation result of the correlation calculation execution means, causes the selection means to select the second filtering means, and causes the sampling means to change the modulation bandwidth. A sampling clock signal set to a frequency for demodulating data from the signal in the narrow transmission mode is supplied, and the number of points of the Fourier transform executed by the Fourier transform execution unit is changed from the signal in the transmission mode having a narrow modulation bandwidth to the data. 5. The OFD according to claim 2, wherein the OFD is set to a value for demodulation and data is demodulated.
M signal receiver. 6. An envelope detecting means for receiving a signal filtered by one of said first filtering means and said second filtering means and performing envelope detection, and said envelope detecting means. And a binarizing unit for binarizing the signal detected by the binarizing unit, wherein the operation control unit specifies a period and a length of a non-signal section included in the signal binarized by the binarizing unit. And
The transmission mode is identified based on the specified period and length of the no-signal section, and the demodulation means demodulates data with settings according to the transmission mode. Item 5. The OFDM signal receiver according to item 1. 7. A signal transmitted by an orthogonal frequency division multiplexing method having a plurality of transmission modes having the same transmission frame length and different modulation bandwidths is received, converted to a baseband signal, and subjected to Fourier transform. The data of the predetermined signal is demodulated, a correlation operation is performed with the data of the predetermined signal stored in advance to determine whether there is a correlation, the transmission mode is identified based on the determination result, and the identified transmission mode is set. Demodulating data by a corresponding receiving operation.