JP3462342B2 - Digital broadcast receiver with transmission mode discrimination function - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / reception system that includes a signal having information peculiar to a transmission signal, and transmits data in any one of a plurality of transmission modes specified. The present invention relates to a method and a receiver for identifying a transmission mode of a received signal in a transmission / reception system.

[0002]

2. Description of the Related Art Digital audio broadcasting (hereinafter referred to as DA
OFDM (Orth)
It is known that the Ogonal Frequency Division Multiplex method is suitable. OFDM
The method is a multicarrier modulation method that uses a large number of carriers, and the respective carriers are in an orthogonal relationship. Therefore, the OFDM method has an advantage that the frequency utilization efficiency can be maximized.

In the OFDM DAB system, on the transmitter side, input data is converted into parallel data by a serial-parallel converter, and then parallel data is converted into π / 4 shift QPSK symbols by a differential encoder. It Then, this symbol is modulated by a fast inverse Fourier transformer (IFFT) to obtain the in-phase component and the quadrature component of the baseband signal, respectively. I
Each output of the FFT is D / A converted, then quadrature-modulated by an oscillation signal from a local oscillator, further converted into a transmission signal of a desired frequency, and transmitted from an antenna.

On the other hand, the operation on the receiver side is the reverse of that on the transmitter side. That is, the signal obtained by the antenna is converted into an intermediate frequency signal, and then the in-phase component and the quadrature component of the baseband signal are extracted by the quadrature demodulator. The output signal of this quadrature demodulator is digitized by an A / D converter and Fourier transformed by a fast Fourier transformer (FFT). A signal for each carrier wave is obtained by the Fourier transform, and then differentially decoded by the differential decoder for each carrier wave.
The output signal of the differential decoder is converted into serial data by the parallel-serial converter, and this becomes the received data.
Actually, this serial data is converted into an analog signal after being subjected to data processing such as error correction.

In such a DAB system, a transmission signal is formed in a format as schematically shown in FIG. 1 on the time axis. That is, data is transmitted in frame units, and a null portion, a reference symbol (reference signal portion) and a data portion are sequentially formed in one frame. The null portion is a period in which no transmission signal exists, the reference symbol serves as a reference phase for differential decoding, and the data portion is assigned a main information signal such as a voice signal to be originally transmitted.
The reference symbol is composed of a leading guard interval and an effective symbol following the leading guard interval, and the data part is composed of a string of symbols each having a leading guard interval. The guard interval is provided to avoid the influence of intersymbol interference due to the influence of multipath.

Further, the DAB system defines four transmission modes as shown in FIG. According to this, it can be seen that the effective symbol length, the number of carriers, and the like differ depending on the transmission mode. Therefore, in the receiver, it is necessary to perform various controls such as demodulation and decoding while adapting to the transmission mode, but the control signal for identifying the transmission mode to the receiver is not included in the transmission signal. In this case, the receiver itself must identify the transmission mode or wait for the user to specify a suitable transmission mode.

As a method for the receiver to automatically identify the transmission mode on the basis of the received signal, there is a method disclosed in EP
0 666 661 A2) is known. According to this, the transmission mode is recognized by detecting and evaluating the symbol length of the received signal, the frame length, the number of carriers, and the carrier space, but the transmission mode is automatically identified without relying on such a method. It is desired to further diversify the technologies that can do this.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object thereof is to provide a new method capable of automatically identifying a transmission mode based on a received signal. And to provide a receiver.

[0009]

SUMMARY OF THE INVENTION A digital broadcast receiver according to the present invention receives a transmission signal having a reference symbol for each frame which is digitally modulated and carries peculiar information, and a signal of a desired frequency is received from the received transmission signal. For outputting as a reception signal, a demodulation means for demodulating a baseband signal from the reception signal, a frequency component constituting the baseband signal is analyzed, and then a frequency information signal is decoded according to the analysis result. A digital broadcast receiver having a decoding means, wherein information carried by the reference symbol is derived from the frequency information signal as a received reference information signal, and the received reference information signal and at least one reference reference information signal are different from each other. And a control unit that determines the transmission mode of the current reception signal based on the present reception signal.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 3 shows a schematic configuration of an OFDM DAB receiver which is an embodiment of the present invention. In FIG. 3, the RF captured by the antenna 1
The (Radio Frequency) signal is supplied to the front end 2 as a tuning means. The front end 2 converts a signal of a desired frequency in the RF signal into an intermediate frequency signal and supplies the intermediate frequency signal to the quadrature demodulator 3.

The quadrature demodulator 3 demodulates a QPSK wave, and comprises, for example, two mixers, a local oscillator and a phase shifter. One mixer mixes the oscillation signal output from the local oscillator with the intermediate frequency signal and outputs the in-phase component signal I of the baseband signal. The other mixer mixes the intermediate frequency signal with the signal obtained by phase shifting the oscillation signal output from the local oscillator by 90 ° by the phase shifter, and outputs the quadrature component signal Q of the baseband signal.

The in-phase component signal I is supplied to the A / D (analog / digital) converter 5I via the LPF (low pass filter) 4I, and the quadrature component signal Q is supplied to the A / D (analog / digital) via the LPF 4Q. ) It is supplied to the converter 5Q. Each A / D converter converts the in-phase and quadrature component signals I and Q band-limited by each LPF into digital signals and supplies them to an FFT (Fast Fourier Transform) 6.

The FFT 6 plays a role of analyzing the frequency component, and is supplied with the digital in-phase and quadrature component signals I,
Q, that is, including a holding unit that holds the data of the in-phase and quadrature component signals sampled by the A / D converters 5I and 5Q, and transforms the held data from the time axis to the frequency axis by the fast Fourier transform. To do. This conversion is a conversion regarding the number of carriers (n) according to a control signal from a system control circuit 14 described later and a period (FFT window) to be subjected to the fast Fourier transform, and the conversion result, that is, the phase information of the carrier. (I _n , q _n ) is
It is sent to the differential demodulator 7. The A / D converter 5I,
The sampling frequency of 5Q is 2.048MHz, for example.
Therefore, the FFT 6 also performs the conversion operation based on this sampling frequency.

The differential demodulator 7 performs differential demodulation based on the phase information regarding the input n carriers. In such differential demodulation, the conjugate complex of the input phase information of the previous symbol and the phase information of the current symbol are multiplied for each carrier to obtain the phase difference between the previous phase information and the current phase information. The differential demodulation output signal carrying the information of the phase difference for each carrier thus obtained is the Viterbi decoder 8
Is determined as a data sequence signal having the most probable value, and the determined data sequence signal is sent to the speech decoder 9.

The audio decoder 9 decompresses the audio compression of the data string signal from the Viterbi decoder 8 and includes an audio reproduction system including a D / A converter in the subsequent stage not shown as PCM (pulse code modulation) digital audio data. Output to. Actually, the processing subsequent to the differential demodulator 7 also includes processing for deinterleaving and error correction, but the description is omitted here.

The output signals of the LPFs 4I and 4Q are also supplied to the null detector 11. Null detector 11 is for each LP
1 depending on the in-phase and quadrature component signals I and Q obtained from F
The null part in the signal of the frame (see FIG. 1) is detected to generate a null detection signal, which is supplied to the FFT 6 and the DSP 12. In the null detector 11, null detection is performed based on the envelope of the input signal, for example. That is, I ² + Q ² is calculated from the in-phase component signal I and the quadrature component signal Q obtained from the LPFs 4I and 4Q, and when the I ² + Q ² is equal to or less than the reference value, the null detection signal is generated. To do.

The DSP 12 uses the memory 13 to perform mode discrimination processing based on the output signal of the FFT 6 in response to the null detection signal, and sends the discrimination result to the system control circuit 14. Although details of the mode determination processing will be described later, a difference between carriers obtained mainly by a predetermined value corresponding to each transmission mode stored in the memory 13, more specifically, a reference symbol (see FIG. 1) defined in each transmission mode. The correlation between the value corresponding to the motion (phase difference) and the value of the FFT output signal is obtained, and the transmission mode is determined by evaluating the obtained correlation value. Here, as shown in FIG. 2, since the symbol length and the number of symbols defined by the mode are different, the reference symbol has different information to be carried by the mode. Therefore, in the receiver, information to be carried by the reference symbol for each mode is stored in the memory 13, and it is determined whether or not the stored information and the information obtained from the received reference symbol have a high correlation. By looking at it, the transmission mode of the current reception can be determined.

The system control circuit 14 is composed of, for example, a microcomputer, and has an FFT 6 and a DSP 12.
Controls the mode discrimination process using
DSP 12 and FF according to the mode discrimination result from 12
It also controls T6, the differential demodulator 7, and other circuits.
The system control circuit 14 also controls each part according to a command from an operation part (not shown). Although the DSP 12 and the system control circuit 14 are configured as separate functional blocks here, they may be configured as a single functional block.

Next, the mode discrimination processing will be described in detail.
In FIG. 4, when the system control circuit 14 detects, for example, that the receiver has been started up (turned on), it starts executing the mode determination process. First, the system control circuit 14 causes the FFT 6 and the DSP 12 to determine whether or not a null has been detected (step S1). This processing is performed based on whether or not the null detection signal from the null detector 11 is issued. In step S1, if no null is detected, a standby state is entered.

When a null is detected, the system control circuit 1
4 causes the FFT 6 to perform a data fetching process (step S2). This processing corresponds to an operation in which the FFT 6 holds the output data of the A / D converters 5I and 5Q in a holding unit such as an internal register in response to the null detection signal. Referring to FIG. 1 for details of this holding operation, null indicates the beginning of the frame, and the FFT 6 sequentially holds the output sample data of the A / D converters 5I and 5Q in the reference symbol period following the end of the null. Since the mode has not been discriminated in step S2, the reference symbol period used here has a symbol length suitable for discriminating the mode, for example, 1.246 m defined in mode 1.
sec (see FIG. 2) is adopted. Since the symbol length stipulated in mode 1 is longer than the symbol length stipulated in any other mode, the data of the entire reference symbol can be fetched in any transmission mode.

When the data acquisition is completed, the system control circuit 14 causes the FFT 6 and the DSP 12 to perform the correlation calculation for the modes 1, 2, 3 and 4 (steps S3, S4, S5 and S6). Each of these arithmetic processes is achieved by a plurality of substeps as follows.

(1) The FFT 6 performs a fast Fourier transform on the data corresponding to the effective symbol (see FIG. 1) of the corresponding mode among the held data. More specifically, in the correlation calculation process related to mode 1 in step S3, in the correlation calculation process related to mode 2 in step S4 with respect to the retained data in the effective symbol equivalent period of 1 msec after the guard interval of 246 usec from the end of null, With respect to the retained data of the effective symbol equivalent period of 250 usec after the guard interval of 62 usec from the end of the null, in the correlation calculation process related to the mode 3 in step S5, the effective symbol equivalent period of 125 usec after the guard interval of 31 usec from the end of the null. In the correlation calculation process related to the mode 4 in step S6, the fast Fourier transform is performed on the held data of the valid symbol corresponding period of 500 usec after the guard interval of 123 usec from the end of the null. That (see Figure 2).

As a result, transform values corresponding to a plurality of frequency components including the carrier used in OFDM are obtained on the transmission side. (2) The DSP 12 has the F obtained by the above (1).
At least one phase differential (reception phase difference) between specific carriers is obtained based on the FT conversion result. (3) The DSP 12 reads from the memory 13 the differential (reference phase difference) between specific carriers obtained by the reference symbol prescribed in the corresponding mode, and the read value and the reception obtained by the above (2). Correlate with the phase difference. The calculation of this correlation is performed between the value of the received phase difference and the value of the reference phase difference respectively corresponding to the same frequency component, and the complex multiplication of the received phase difference and the conjugate complex number of the reference phase difference is performed. This is achieved by averaging the values obtained by the above, and the average value is finally output as the correlation value between the two.

When the correlation calculation is completed for all the modes, the system control circuit 14 instructs the DSP 12 to compare the obtained correlation values with each other in magnitude, and perform the mode discrimination based on the comparison result ( Step S
7). That is, the DSP 12 performs steps S3 to S
Among the correlation values obtained in step 6, the mode corresponding to the largest correlation value is determined as the transmission mode currently being received by the receiver, and the determination result is determined by the system control circuit 14
To send to.

The system control circuit 14 initializes each part of the receiver according to the sent mode judgment result, and adapts the subsequent receiver operation to the judged transmission mode.
For example, the FFT window is set to FFT6 so that FFT processing can be accurately performed on the effective symbols defined by the determined transmission mode. In the mode discrimination processing of FIG. 4, the correlation values are obtained for all modes, and the mode corresponding to the largest correlation value is determined to be the transmission mode of the current reception signal. However, the mode discrimination processing should be modified as shown in FIG. You can also

In FIG. 5, the same steps as those in FIG. 4 are designated by the same reference numerals, and detailed description of the same steps will be omitted. This mode discrimination processing is different from that in FIG. 4, and after obtaining correlation values for all modes,
It is determined whether or not the maximum correlation value exceeds a predetermined value (step S10), and if not, step S again.
The processing from 1 to S6 is performed. As a result, the mode discrimination is performed for the received data of the new frame.

When it is determined in step S10 that the maximum correlation value exceeds the predetermined value, the system control circuit 14 determines the mode corresponding to the maximum value as the transmission mode of the current reception signal (step S11). . According to such a mode determination process, since the final mode determination is made only when the maximum correlation value is larger than the predetermined value in step S10, the reliability of the mode determination result is improved.

The mode discrimination processing can be modified as shown in FIG. In FIG. 6 as well, steps similar to those in FIG. 4 are denoted by the same reference numerals, and detailed description of the equivalent steps will be omitted. This mode discrimination process is
In the first frame, the correlation value is calculated for Mode 1 and Mode 2, and for Mode 3 and Mode 4, the correlation value is calculated in the next frame. Then, the mode determination is performed based on the correlation value thus obtained over the two frames. Therefore, between step S4 and step S5, a null detection step S1A similar to step S1 and a data acquisition step S2A similar to step S2 are provided.

In FIGS. 4 to 6, the correlation calculation is always performed for all the modes to judge the mode and the mutual comparison of the correlation values is performed. However, as shown in FIG. 7, only the minimum correlation calculation is performed. It is also possible to determine the mode with. In FIG. 7 as well, steps similar to those in FIG. 4 are denoted by the same reference numerals, and detailed description of the equivalent steps will be omitted.

In this mode discriminating process, only when it is discriminated that the obtained one correlation value is larger than the predetermined value, the mode corresponding to the correlation value is immediately discriminated as the transmission mode of the present received signal. It is based on that. That is, it is determined whether or not the correlation value for mode 1 obtained in step S3 is larger than a predetermined value (step S31), and if it is determined to be large, the mode 1 is set as the transmission mode of the current reception signal. Final decision (step S32),
If not, the process proceeds to step S4 and the mode 2
Correlation calculation processing is performed. Further, it is determined whether or not the correlation value for mode 2 obtained in step S4 is also larger than a predetermined value (step S41),
If it is determined to be large, the mode 2 is finally determined to be the transmission mode of the currently received signal (step S42), and if not so, the process proceeds to step S5 and the correlation calculation process for the mode 3 is performed. Similarly, it is determined whether or not the correlation value for mode 3 obtained in step S5 is also greater than a predetermined value (step S51). If it is determined that the correlation value is greater than the predetermined value, mode 3 is transmitted for the currently received signal. The final determination is made as to the mode (step S52), and if not, the process proceeds to step S6 to perform the correlation calculation process for mode 4, and the correlation value for mode 4 obtained in step S6 is also larger than the predetermined value. Is determined (step S61), and if it is determined to be large, mode 4 is set.
Is finally determined as the transmission mode of the current received signal (step S
62).

If it is determined in step S61 that the correlation value for mode 4 does not exceed the predetermined value, the process returns to step S1 and the process of step S2 is performed again for the next frame. In this case, this corresponds to that none of the correlation values obtained for all modes exceed the predetermined value. According to such a threshold value comparison type mode determination process of the correlation value, the mode determination can be performed with a minimum correlation calculation, which contributes to shortening the time of the mode determination process.

In addition to these, various modified examples can be given. FIG. 8 shows one of them, and here also, the steps equivalent to those in FIG. 4 are denoted by the same reference numerals, and the detailed description of the equivalent steps will be omitted. In the mode determination process of FIG. 8, first, the magnitude comparison is performed between the correlation value R ₁ for mode 1 obtained in step S3 and the correlation value R ₂ for mode 2 obtained in step S4 (step S100). ), Correlation value R
_{If 1} is larger than the correlation value R ₂ , it is temporarily judged that the mode 1 is the transmission mode of the current reception signal (step S101), and conversely, if the correlation value R ₁ is less than or equal to the correlation value R ₂ . If so, it is temporarily determined that the mode 2 is the transmission mode of the current reception signal (step S102). After this temporary determination, it is determined whether or not the maximum correlation value of both of them (that is, the correlation value corresponding to the mode determined in steps S101 and S102) is larger than a predetermined value (step S103). In this case, the mode determination process is terminated, and thus the temporarily determined mode is recognized as the finally determined mode, and the DSP 12 sends information to that effect to the system control circuit 14.

On the other hand, in step S103, the correlation value R
_When it is determined that the maximum correlation value of ₁ and the correlation value R ₂ is less than or equal to the predetermined value, this mode determination processing continues.
That performs both magnitude comparison of per correlation value R ₄ for mode 4 obtained in the correlation value R ₃ and step S6 for mode 3 obtained in step S5 (step S200), the correlation value R ₃ correlation values R _Four
If it is larger than the above, it is temporarily determined that the mode 3 is the transmission mode of the current reception signal (step S20).
1) On the contrary, if the correlation value R ₃ is less than or equal to the correlation value R ₄ , it is temporarily determined that the mode 4 is the transmission mode of the current reception signal (step S202). Then, after this temporary determination, the maximum correlation value of both (that is, step S
201, it is determined whether or not the correlation value corresponding to the mode determined in S202 is larger than a predetermined value (step S203), and if it is larger, this mode determination routine is terminated, and thus a temporary determination is made. The mode is recognized as the finally determined mode, and the DSP 12 sends information to that effect to the system control circuit 14.

If it is determined in step S203 that the maximum correlation value of the correlation values R ₃ and R ₄ is less than or equal to the predetermined value, it is determined that none of the obtained correlation values exceeds the predetermined value. Then, the process shifts to step S1 to perform the mode determination again in the next frame. In the processing of FIGS. 4 to 8, the correlation calculation for the mode 1 is always performed first, but the correlation calculation for other modes may be started, and the order of performing the correlation calculation is changed. Of course, you can do that. In addition, the mode targeted by the correlation calculation first performed in the mode determination processing can be set to the mode indicated by the data read from the backup memory. For example, in response to a power-off command of the receiver, the data indicating the transmission mode that has been recognized until then is stored in the backup memory, and in response to subsequent power-on, the data is read from the backup memory and this data The mode indicated by is the mode targeted by the correlation calculation first performed in the mode discrimination processing. By doing so, the correlation calculation for the transmission modes having a high possibility is preferentially performed, so that in the processing of FIGS. 7 and 8, the time required for the mode determination processing can be further shortened.

In the correlation calculation process described above, the phase difference between the specific carriers is obtained in the sub-step (2), and then the reception positions corresponding to the same frequency components are obtained in the sub-step (3). The value of the phase difference and the value of the reference phase difference are correlated with each other. However, if there is a frequency shift in the output signal of the local oscillator for mixing with the RF signal in the front end 2 and converting it into an intermediate frequency signal, the carrier for which the phase difference is obtained in sub-step (2) also becomes real. There is a possibility of recognizing a carrier different from the one defined in the OFDM transmission / reception system. If there is such an erroneous recognition, it is conceivable that the obtained correlation value includes a considerable error or shows no correlation at all, and reliable mode determination cannot be performed.

Therefore, it is preferable to perform the mode discrimination processing so as not to cause such a problem. To this end, in each correlation calculation process (steps S3 to S6), some of the carriers specified in the sub-step (2) are changed to obtain the correlation value, and the optimum correlation value is obtained. That is, after obtaining the correlation value for the carrier specified in the initial stage, on the frequency axis, the carriers distributed in the high band and the low band side of the initial carrier are sequentially specified, and the correlation is obtained for each of the specified carriers. It asks for a value. Then, of the correlation values thus obtained for each carrier, the most probable one is adopted as the final correlation value. By doing so, the mode determination is performed based on the correct correlation value, so that the above-mentioned inconvenience does not occur.

The difference between the carrier used for obtaining the final correlation value and the initial carrier in the mode discriminating process in which the countermeasure against the trouble is taken is calculated by the local oscillator in the front end 2 after the final mode discriminating. By correcting the frequency deviation of the output signal by feeding back to the frequency of the output signal of, the accurate reception, demodulation, and decoding processes thereafter can be compensated. This is also a technology related to so-called AFC (Automatic Frequency Control).

In the above description, the mode is determined based on the correlation value, but basically, the mode is determined based on the difference between the reception phase difference and the reference phase difference from the memory 13. Is also good. For example, the mode determination may be made based on whether or not the two match, or the mode determination may be made based on how far the two are apart. Therefore, according to the present invention, in a receiver that analyzes frequency component information constituting a baseband signal (for example, in-phase and quadrature component signals I and Q) by an analyzing unit such as FFT6 and then decodes the frequency component information, the DS
The information carried by the reference symbol is derived from the frequency component information as reception reference information by P12, and the transmission mode of the current reception signal is determined based on the difference between this reception reference information and at least one reference reference information from the memory 13. Has a big feature.

In addition, although various means are limitedly described in the above-mentioned embodiment, it is possible to appropriately modify them within a range that can be designed by those skilled in the art.

[0040]

According to the present invention, it is possible to provide a new method and receiver capable of automatically identifying a transmission mode based on a received signal.

[Brief description of drawings]

FIG. 1 is a diagram showing a format of a transmission signal in a DAB system.

FIG. 2 is a chart showing transmission specifications of each transmission mode in the DAB system.

FIG. 3 is a block diagram showing a schematic configuration of an OFDM DAB receiver according to an embodiment of the present invention.

FIG. 4 is a flowchart showing an example of a procedure of transmission mode determination processing according to the present invention.

5 is a flowchart showing a modification of the transmission mode determination process of FIG.

6 is a flowchart showing another modified example of the transmission mode determination process of FIG.

FIG. 7 is a flowchart showing another example of the procedure of the transmission mode determination process according to the present invention.

FIG. 8 is a flowchart showing still another example of the procedure of the transmission mode determination process according to the present invention.

[Explanation of symbols for main parts]

1 antenna 2 front end 3 Quadrature demodulator 4I, 4Q LPF 5I, 5Q A / D converter 6 FFT 7 differential decoder 8 Viterbi decoder 9 voice decoder 11 Null detector 12 DSP 13 memory 14 System control circuit

Claims (10)

(57) [Claims] 1. Tuning means for receiving a transmission signal having a reference symbol which is digitally modulated and carrying unique information for each frame, and outputs a signal of a desired frequency from the received transmission signal as a reception signal, and the reception signal. A digital broadcast receiver having demodulation means for demodulating a baseband signal from the above, and decoding means for decoding a frequency information signal constituting the baseband signal and then decoding a frequency information signal according to the analysis result, Control means for deriving information carried by the reference symbol from the frequency information signal as a received reference information signal, and determining the transmission mode of the present received signal based on the difference between the received reference information signal and at least one reference reference information signal; A digital broadcast receiver characterized by having. 2. The control means stores storage means for storing reference reference information signals corresponding to a prescribed transmission mode, and reads the reference reference information signals from the storage means to sequentially receive the received reference information signals. And a determination means for determining the transmission mode corresponding to the reference reference information signal when the smallest difference is detected as the transmission mode of the current reception signal. Digital broadcast receiver. 3. The determination means obtains the correlation between the received reference information signal and the reference reference information signal, and detects the difference based on whether the correlation is high or low. The described digital broadcasting receiver. 4. The correlation calculating means, wherein the determining means reads out the reference reference information signal corresponding to all the defined transmission modes from the storage means and sequentially calculates a correlation value with the received reference information signal, 3. The digital broadcast receiver according to claim 2, further comprising: a mutual comparison unit that determines the transmission mode corresponding to the maximum correlation value among the calculated correlation values as the transmission mode of the current reception signal. 5. The mutual comparison means determines the transmission mode corresponding to the maximum correlation value as the transmission mode of the current received signal only when the maximum correlation value is larger than a predetermined value. Item 4. A digital broadcast receiver according to item 4. 6. The correlation calculating means, wherein the determining means reads one of the reference reference information signals corresponding to a defined transmission mode from the storage means and calculates a correlation value with the received reference information signal. A threshold value comparing means for determining the transmission mode corresponding to the calculated correlation value as the transmission mode of the current received signal when the correlation value calculated by the correlation calculating means is larger than a predetermined value. The digital broadcast receiver according to claim 2. 7. The correlation calculating means stores the other one of the reference reference information signals corresponding to a defined transmission mode when a correlation value larger than the predetermined value is not calculated. 7. A correlation value with the received reference information signal is read out from the means to calculate the correlation value.
The described digital broadcasting receiver. 8. The transmission signal is a signal subjected to multi-carrier modulation for multiplexing a plurality of digital modulation waves, and the information carried by the reference symbol is a phase difference between predetermined carriers of the digital modulation wave. Claim 1 characterized by the above.
8. The digital broadcasting receiver according to any one of 1 to 7. 9. The control means sequentially changes the recognition of the predetermined carrier to derive information carried by the reference symbol as a received reference information signal, and the derived received reference information signal and the reference reference information signal. 9. The digital broadcast receiver according to claim 8, wherein the transmission mode of the current reception signal is determined based on the most probable difference from the above. 10. The digital broadcast receiver according to claim 8, wherein the multicarrier modulation is OFDM modulation, and the digital modulation wave is a QPSK wave.