JP5791107B2 - Received signal judgment device - Google Patents

Description

  The present invention relates to a received signal determination device that determines whether a received signal is a television signal.

  With the shift from analog TV to digital TV, some frequencies are released and those frequency bands are used for mobile communications. In particular, in recent years when new communication services and various applications are put into practical use one after another, the allocation of the radio band is subdivided and complicated. While the communication services allocated in this way are mixed in the radio band, it is gradually becoming difficult to allocate new communication services to the radio band.

  For this reason, in recent years, standardization of a wireless communication network using TV White Space (TVWS) has been promoted, and standardization of a method for allowing the IEEE 802 standard to coexist in TVWS has also been promoted. For this reason, it becomes particularly important how these different IEEE 802 standard communication systems coexist in the same frequency band, and in particular, the importance has increased with the recent dramatic increase in radio communication opportunities.

  Further, in this TVWS, there are actually a wider range of TV bands that can be freely used in a license-free manner. In particular, ECMA, IEEE SCC41, and the like are being studied as wireless communication standards that can be operated without a license, in addition to the above-described IEEE802, and in these standards, a television broadcaster is a first user. Only when the first user is not broadcasting using the TV band, the TV band is released for wireless communication by the secondary user. Thereby, it is possible to promote efficient use of the TV band.

  When the secondary user actually wants to start communication in the TV band, it is necessary to first determine whether or not the first user is using the TV band. When it is determined that the first user is not using the TV band, the secondary user can communicate using the TV band for the first time. In order to actually perform the determination, a technique for determining the presence or absence of a TV signal at the present time in the TV band is required.

  A conventional reception signal determination device for determining the presence or absence of a TV signal, particularly in DVB-T which is a digital TV standard such as Europe, discloses a technique shown in Non-Patent Document 1. The disclosed technology of Non-Patent Document 1 determines whether or not a received signal is a TV signal by previously setting a reference sequence corresponding to a TV signal and referring to the set reference sequence. Actually, a correlation value is obtained between the received signal to be discriminated and the reference sequence, and the presence or absence of the TV signal is discriminated based on the obtained correlation value. In particular, Non-Patent Document 1 describes a method for improving the reliability of the correlation value itself by performing frequency offset estimation and signal power flattening before acquiring the correlation value.

  Conventionally, for example, a technique disclosed in Patent Document 1 has also been proposed. This technology has found a new sliding correlation method for the purpose of detecting a TV signal having a very low power level at a low SNR while maintaining a reduction in processing time and low cost. .

  Prior to the proposal of the technology disclosed in Patent Document 1, a method for determining the presence / absence of a TV signal at the present time in a TV band using a correlation value obtained with a reference sequence has already been generalized. ing.

  FIG. 11 shows an example of a conventional general received signal determination device 7. The reception signal determination device 7 includes a TV channel BPF 71, a specific band extraction filter 72, a baseband conversion unit 73, an AD converter (ADC) 74, a time offset correction unit 75, a frequency offset correction unit 76, and a buffer. 77, a correlation unit 78, a buffer 79, an averaging unit 80, and a determination unit 81.

  The reception signal determination device 7 first filters a reception signal received as a determination target in the TV channel BPF 71 to a desired pass band, and filters it in a specific band extraction filter 72 to a narrower specific pass band. Accordingly, it is possible to substantially cut a band that is not necessary for determining the received signal. The received signal is frequency-converted into a baseband signal by the baseband converter 73, subjected to analog-digital conversion at the ADC 74, and further, there is no time difference with respect to a reference sequence described later in the time offset corrector 75. The frequency offset correction unit 76 corrects the frequency offset.

The received signal that has undergone these processes is temporarily stored in the buffer 77, and then a correlation value is obtained with the reference sequence in the correlation unit 78. FIG. 12 shows the received signal in time series. For the received signal, samples rx having a length T of one OFDM symbol are sequentially extracted. The samples rx are sequentially extracted with rx ₁ , rx ₂ ,..., Rx _k sequentially shifted from each other, assuming that the intervals between the samples rx are separated from each other by Δτ. Yes. This interval Δτ is not necessarily the same interval, and may be different from Δτ ₁ , Δτ ₂ ,..., Δτ _k-1 shown in the drawing. Incidentally, the entire extraction period of this sample is represented by kT + ΣΔτ _i .

  A correlation value is obtained between each sample extracted in this way and the reference sequence in the correlation unit 78. The obtained correlation value is temporarily stored in the buffer 79 and averaged in the averaging unit 80.

Wherein each sample _{rx 1, rx 2, ···,} Rx 1 correlation values for rx _k, Rx _2, ···, when the Rx _k, the average value of the correlation values obtained in the averaging section 80 Is obtained by the following equation.

That is, a correlation value obtained by dividing the sum of absolute values of Rx ₁ , Rx ₂ ,..., Rx _{k by} the number of samples k is used as the average of the correlation values.

  The determination unit 81 compares the average value of the correlation values obtained by the averaging unit 80 with a preset threshold value. If it is greater than this threshold, it can be determined that the received signal is a TV signal, and if it is less than or equal to the threshold, it can be determined that the received signal is not a TV signal.

  FIG. 13 shows an example of another conventional received signal determination device 8. The received signal determination device 8 determines whether or not the received signal is a TV signal by using sliding correlation, and includes a TV channel BPF 71, a specific band extraction filter 72, a baseband converter 73, and an AD converter. (ADC) 74, time offset correction unit 75, frequency offset correction unit 76, buffer 77, averaging unit 91, sliding correlation unit 92, buffer 79, averaging unit 92, and absolute value calculation unit 93, a peak detection unit 94, and a determination unit 81.

The reception signal determination device 8 performs the same processing as the reception signal determination unit 8 described above in the TV channel BPF 71 to the buffer 77. The averaging unit 91 performs an averaging process on the received signal stored in the buffer 77. The sliding correlation unit 92 performs the sliding correlation process described below. FIG. 14 shows received signals displayed in time series. For the received signal, samples rx _i (j) having a length T of one OFDM symbol are sequentially extracted. This sample rx _i (j) is extracted within the unit detection period having a length twice as long as the first symbol period T, rx ₁ (1), rx ₂ (1), rx ₃ (1),. Extract a sample of rx _k (1). This sample extraction is performed so as to overlap each other on the time axis. In the example of FIG. 14, the extraction time differences between samples are τ ₁ , τ ₂ ,..., Τ _k−1, and extraction from the first sample rx ₁ (1) to the last sample rx _k (1) is performed. The time difference is Στ _i . That is, the sliding correlation is extracted by shifting the sample extraction start time over a plurality of steps. After extracting the sample within the first unit detection period, the sample is similarly extracted during the subsequent unit detection period. Such sample extraction processing is performed until the last unit detection period.

  A correlation value is obtained for each sample extracted in this manner from the reference sequence in the sliding correlation unit 92. The obtained correlation value is temporarily stored in the buffer 79 and averaged in the averaging unit 93.

Here, the respective samples rx ₁ (1), rx ₂ (1),... Rx _L (1), rx ₁ (2), rx ₂ (2),... Rx _L (2),. , Rx ₁ (k), rx ₂ (k),... Rx _L (k)) are represented as Rx ₁ (1), Rx ₂ (1),... Rx _L (1), Rx _{1 (2), Rx 2 (2} ), ··· Rx L (2), ···, Rx 1 (k), when the _{Rx 2 (k), ··· Rx} L (k), the averaging unit The average value of correlation values obtained in 93 is obtained by the following equation.

These formulas mean that the average is first obtained for correlation values Rx ₁ (1), Rx ₁ (2), Rx ₁ (3),... Rx ₁ (L). Next, an average value is obtained for the correlation values Rx ₂ (1), Rx ₂ (2), Rx ₂ (3),... Rx ₂ (L). In the same manner, by changing i in Rx _i (j) (j = 1, 2,... L), averages are obtained until k is reached. In the absolute value calculation unit 94, the absolute value of the obtained average value is obtained based on the above-described formula. Next, in the peak detection unit 95, the largest value is specified by the following formula from the absolute values of the obtained average values.

The largest value is defined as an Rx ^max value. Finally, the determination unit 81 compares the Rx ^max value with a preset threshold value to determine whether or not the received signal is a TV signal.

Japanese Patent Application No. 2010-245331

Gaddam and M. Ghosh, "Robust sensing of DVB-T signals," Proc. IEEE DySPAN 2010, April 2010, pp1-pp8

  However, since the above-described conventional received signal determination device 7 obtains a correlation value at a random timing, it may be averaged including a very small correlation value at a certain timing. As a result, there is a problem in terms of accuracy with respect to the average value of the correlation values compared with the threshold value. In addition, the received signal determination device 7 has a problem that when samples are extracted, the samples do not overlap in time, so that the time for actually detecting all the samples increases. there were.

  Further, in the conventional received signal determination device 8 described above, when the value of k is set larger, a large amount of processing capability is required for the hardware, and the increase in the cost of hardware resources can be avoided. Can not. On the other hand, when the value of k is set smaller, the maximum value of k changes on a case-by-case basis, and the detection performance is limited.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is, in particular, in a received signal determination device that determines whether a received signal is a television signal. It is an object of the present invention to provide a received signal determining apparatus capable of improving the determination accuracy and improving the cost performance of the apparatus itself.

The received signal determination apparatus according to claim 1 , in a time-series manner, samples a predetermined-length symbol period from a received signal to be determined over a plurality of unit detection periods each having an integral multiple of the symbol period. Steps (L is an integer of 2 or more) are sequentially shifted and extracted, and for each extracted sample, a correlation value is obtained with a pre-defined reference sequence, and K processing (K is 2 or more) is obtained. Sliding correlation calculation means repeatedly executed in an integer) unit detection period, step-by-step average calculation means for obtaining an average of sample correlation values during all the unit detection periods for each step, and step-by-step average calculation means Correlation average computing means for obtaining an average between all the above steps with respect to the average of correlation values obtained at each step by And determining means for determining whether or not the received signal is a desired signal by comparing an average of correlation values between steps calculated by the means and a preset threshold value. To do.

  According to a second aspect of the present invention, in the reception signal determination device according to the first aspect, the correlation average calculation means selects only some correlation values from all correlation values to be averaged and averages the correlation values. It is characterized by calculating | requiring.

  According to a third aspect of the present invention, there is provided the received signal determining apparatus according to the first aspect, wherein the correlation average calculating means includes an absolute value of the sum of the obtained positive correlation values and an absolute value of the sum of the obtained negative correlation values. An average is obtained by dividing the sum of the values by the number of correlation values.

  The reception signal determination device having the above-described configuration can improve the accuracy of determination in the reception signal determination device that determines whether or not the reception signal is a television signal, and can improve the cost performance of the device itself. It becomes possible.

It is a figure which shows the block structural example of the received signal determination apparatus as 1st Embodiment to which this invention is applied. It is a figure which shows the block structural example of a frequency offset correction part. It is a figure which shows the example which extracts sequentially the sample which consists of the length T of 1 OFDM symbol in the selection sliding correlation process. It is a figure which shows the block structural example of the received signal determination apparatus as 2nd Embodiment to which this invention is applied. It is a figure which shows the other example which extracts a sample sequentially in the selection sliding correlation process. It is a figure which shows the block structural example of the received signal determination apparatus as 3rd Embodiment to which this invention is applied. It is a figure for demonstrating the detail of the processing operation in 3rd Embodiment to which this invention is applied. It is a figure which shows the block structural example of the received signal determination apparatus as 4th Embodiment to which this invention is applied. It is a figure which shows the block structural example of the received signal determination apparatus as 5th Embodiment to which this invention is applied. It is a figure which shows the block structural example of the received signal determination apparatus as 6th Embodiment to which this invention is applied. It is a figure which shows the block structural example of the conventional received signal determination apparatus. It is a figure for demonstrating the detail of the processing operation of the received signal determination apparatus in the past. It is a figure which shows the block structural example of the other received signal determination apparatus in the past. It is another figure for demonstrating the detail of the processing operation of the received signal determination apparatus in the past.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 shows a block configuration example of a received signal determination apparatus 1 as a first embodiment to which the present invention is applied. The reception signal determination device 1 includes a TV channel BPF 11 that receives a radio signal as a determination target, a baseband conversion unit 12 connected to the TV channel BPF 11, and an AD converter (ADC) connected to the baseband conversion unit 12. ) 13, a time offset correction unit 14 and a frequency offset correction unit 15 connected to the ADC 13, a buffer 16 connected to the time offset correction unit 14 and the frequency offset correction unit 15, and a buffer 16, respectively. The selected sliding correlation unit 17, the buffer 18 connected to the selected sliding correlation unit 17, the absolute value calculation unit 19 connected to the buffer 18, the average value calculation unit 20 connected to the absolute value calculation unit 19, And a determination unit 21 connected to the average value calculation unit 20.

  The TV channel BPF 11 receives, as an input, an RF signal having a pass characteristic in a predetermined frequency band when a reception signal as a discrimination target is received. That is, the TV channel BPF 12 is configured as a band pass filter for filtering the received signal into the predetermined frequency band. Incidentally, the bandwidth may be set to 6 MHz, 7 MHz, 8 MHz, or the like, for example, according to the standard of each TV signal. The TV channel BPF 11 outputs the reception signal subjected to the above-described processing to the baseband conversion unit 12.

  The baseband conversion unit 12 converts the received signal as the RF signal supplied from the TV channel BPF 11 into a baseband signal. The baseband conversion unit 12 performs corresponding to the fact that the RF signal input to the TV channel BPF 11 is a signal modulated for transmission, but it is not essential to provide this. Of course, subsequent signal processing may be performed in the RF band.

  The ADC 13 samples an input reception signal as an analog signal at a predetermined frequency and converts it into a digital signal. By performing AD conversion by the ADC 13, it is possible to efficiently perform the subsequent signal processing, particularly the processing in the time offset correction unit 14.

  The time offset correction unit 14 receives a digital signal so as to remove a time difference (time offset) from the reference sequence as a pre-stage of a correlation calculation operation with a reference sequence in the selective sliding correlation unit 17 described later. Correction is performed by time-shifting the signal. The time offset unit 14 corrects the received signal as a digital signal so that there is no time difference with respect to the reference sequence. Thereby, the calculation result of the correlation value in the selective sliding correlation unit 17 described later becomes a larger value compared with the case where the time offset is not performed, and is more suitable for detection and determination from the viewpoint of the S / N ratio. Become.

  The frequency offset correction unit 15 corrects the frequency offset of the reception signal input from the ADC 13. That is, since the received signal is propagated through the air by the time it is received by the TV channel BPF 11, its frequency component may be affected in some way during the propagation process. Therefore, by applying the frequency offset performed by the frequency offset correction unit 15, it is possible to further improve the calculation accuracy when performing the selective sliding correlation process described later.

  Each processing of the time offset correction unit 14 and the frequency offset correction unit 15 may not be performed, or only one or both of them may be performed.

  FIG. 2 shows a block configuration example of the frequency offset correction unit 15. The frequency offset unit 15 includes an FFT unit 41, a frequency offset estimation unit 45 and a buffer 42 connected to the FFT unit 41, a frequency correction unit 43 connected to the buffer 42 and the frequency offset estimation unit 45, and a frequency correction unit 43. And an inverse FFT unit connected to the.

  The FFT unit 41 performs fast Fourier transform (FFT) on the received signal input from the ADC 13 and converts the received signal into spectrum information on the frequency axis. The buffer 42 buffers information output from the FFT unit 41. The frequency offset estimating unit 45 compares the spectrum information given from the FFT unit 41 with predetermined frequency information to perform matching, and estimates the frequency offset of the spectrum information given from the FFT unit 41. Here, the predetermined frequency information to be matched is frequency information for each subcarrier of the OFDM system in which the discriminating symmetric signal is defined in a signal such as DVB-T.

  Information on the main fraction offset obtained by the estimation by the frequency offset estimation unit 45 is transmitted to the frequency correction unit 43. The frequency correction unit 43 corrects the frequency offset on the frequency axis based on the estimated value of the frequency offset supplied from the frequency offset estimation unit 45. The inverse FFT unit 44 converts the signal supplied from the frequency correction unit 43 into a time domain signal and outputs it to the buffer 16.

  The buffer 16 is supplied with the reception signal subjected to the time offset described above by the time offset correction unit 14 or the reception signal subjected to the frequency offset described above by the frequency offset correction unit 15. The buffer 16 temporarily stores the supplied reception signals.

  The selective sliding correlation unit 17 reads the received signal stored in the buffer 16 and performs a selective sliding correlation process described later. The selected sliding correlation unit 17 calculates a correlation value between the read reception signal and the reference sequence. The received signal and the reference sequence read here are already in a state in which the time offset between them is almost corrected by the action of the time offset correction unit 14. Incidentally, the selection sliding correlation unit 17 may determine the calculation range based on the range estimated by the time offset correction unit 15 described above. The correlation value obtained by the selected sliding correlation unit 17 is temporarily stored in the buffer 18.

  The absolute value calculator 19 reads the correlation value from the buffer 18 and calculates the absolute value. The absolute value of the correlation value calculated by the absolute value calculation unit 19 is sent to the average value calculation unit 20. The average value calculator 20 calculates an average value for the absolute value of the correlation value. Details of the processing by the absolute value calculator 19 and the average value calculator 20 will be described later.

  The determination unit 21 compares the average value of the correlation values obtained by the average value calculation unit 20 with a preset threshold value. If it is greater than this threshold, it is determined that the received signal is a TV signal, and if it is less than or equal to the threshold, it is determined that the received signal is not a TV signal.

  Next, the operation of the received signal determination apparatus 1 as the first embodiment configured as described above will be described.

  First, a received signal received as a determination target is first filtered to a desired passband in the TV channel BPF11. Accordingly, it is possible to substantially cut a band that is not necessary for determining the received signal. The received signal is frequency-converted into a baseband signal by the baseband converter 12 and analog / digital converted by the ADC 13. Then, the received signal as a digital signal is corrected by the time offset correction unit 14 so that there is no time difference with respect to the reference sequence, and the frequency offset correction unit 15 performs the above-described frequency offset processing. Incidentally, each process in the time offset correction unit 14 and the frequency offset correction unit 15 may be performed only in one of them.

  Next, the received signal subjected to the offset processing is temporarily stored in the buffer 16, and then the selective sliding correlation processing by the selective sliding correlation unit 17 is performed.

In the selected sliding correlation process, as shown in FIG. 3, the received signal sequentially extracts samples rx _i having a length T of one OFDM symbol. This sample rx _i is extracted within a unit detection period having a length twice as long as the first symbol period T (which may be an integer multiple), rx ₁ , rx ₂ , rx ₃ ,. Extract _k samples. This sample extraction is performed so as to overlap each other on the time axis. In the example of FIG. 3, the extraction time differences between samples are τ ₁ , τ ₂ ,..., Τ _k−1, and the extraction time difference from the first sample rx ₁ to the last sample rx _k is Στ _i . . That is, the sliding correlation is extracted by shifting the sample extraction start time over a plurality of steps.

  Incidentally, in the first embodiment, it is premised that samples are extracted within one unit detection period. When the sample detection is completed in one unit detection period, the sample extraction process is terminated.

A correlation value is obtained for each sample extracted in this manner from the reference sequence in the selected sliding correlation unit 17. Wherein each sample _{rx 1, rx 2, ···,} Rx 1 correlation values for rx _k, Rx _2, ···, and Rx _k. Next, in the calculated correlation value, the absolute value calculation unit 19 obtains an absolute value. As a result, absolute values | Rx ₁ |, | Rx ₂ |,..., | Rx _k |

  Next, the average value calculation unit 20 calculates the average of the absolute values of these correlation values. Specifically, the average value is obtained by the following formula.

Finally, the obtained average value of | Rx _i | is compared with a threshold value.

  In the first embodiment to which the present invention having the above-described configuration is applied, samples of a predetermined symbol period are extracted from a determination target received signal by sequentially shifting a plurality of samples in a unit detection period in a time-series manner. Then, for each extracted sample, a correlation value is obtained with the reference sequence. Then, an average of the obtained correlation values for each sample is obtained, and it is determined whether or not the received signal is a desired signal by comparing the average with a preset threshold value.

  Thereby, compared with the prior art which determines a received signal based on the maximum value of the correlation value, since the present invention makes a determination based on the average value of the correlation values, the determination accuracy can be further improved. .

  FIG. 4 shows a block configuration example of a received signal determination apparatus 2 as a second embodiment to which the present invention is applied. The received signal determination device 2 includes the TV channel BPF 11, the baseband converter 12, the ADC 13, the time offset corrector 14, the frequency offset corrector 15, the buffer 16, the selected sliding correlator 17, and the buffer. 18, and further includes an averaging unit 31 connected to the buffer 18, an absolute value calculation unit 19 connected to the averaging unit 31, an average value calculation unit 20, and a determination unit 21.

  In the second embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof will be omitted.

  The averaging unit 31 performs an averaging process to be described later on the correlation values recorded in the buffer 18. The averaging unit 31 calculates the average of the correlation values, and then outputs this to the absolute value calculation unit.

  Next, the operation of the received signal determination apparatus 2 as the second embodiment having the above-described configuration will be described.

  Filtering to the pass band by the TV channel BPF 11, frequency conversion to baseband signal by the baseband conversion unit 12, analog-to-digital conversion by the ADC 13, correction by the time offset correction unit 14 so as not to have a time difference, frequency offset correction Each process by the unit 15 and the storage process by the buffer 16 are the same as the operation of the first embodiment described above.

Next, in the selected sliding correlation process, as shown in FIG. 5, samples rx _i (j) having a length T of one OFDM symbol are sequentially extracted. This sample rx _i (j) is extracted within the unit detection period having a length twice as long as the first symbol period T, rx ₁ (1), rx ₂ (1), rx ₃ (1),. Extract a sample of rx _k (1). This sample extraction is performed so as to overlap each other on the time axis. In the example of FIG. 5, the extraction time differences between samples are τ ₁ , τ ₂ ,..., Τ _k−1, and extraction from the first sample rx ₁ (1) to the last sample rx _k (1) is performed. The time difference is Στ _i . That is, the sliding correlation is extracted by shifting the sample extraction start time over a plurality of steps. After extracting the sample within the first unit detection period, the sample is similarly extracted during the subsequent unit detection period. Such sample extraction processing is performed until the last unit detection period.

  A correlation value is obtained for each sample extracted in this manner from the reference sequence in the selected sliding correlation unit 17. The obtained correlation value is temporarily stored in the buffer 18 and averaged in the averaging unit 31.

Here, the respective samples rx ₁ (1), rx ₂ (1),... Rx _L (1), rx ₁ (2), rx ₂ (2),... Rx _L (2),. , Rx ₁ (k), rx ₂ (k),... Rx _L (k)) are represented as Rx ₁ (1), Rx ₂ (1),... Rx _L (1), Rx _{1 (2), Rx 2 (2} ), ··· Rx L (2), ···, Rx 1 (k), when the _{Rx 2 (k), ··· Rx} L (k), the averaging unit The average value of the correlation values obtained at 31 is obtained by the following equation.

These formulas mean that the average is first obtained for correlation values Rx ₁ (1), Rx ₁ (2), Rx ₁ (3),... Rx ₁ (L). Next, an average value is obtained for the correlation values Rx ₂ (1), Rx ₂ (2), Rx ₂ (3),... Rx ₂ (L). In the same manner, by changing i in Rx _i (j) (j = 1, 2,... L), averages are obtained until k is reached. These averages are calculated by the averaging unit 31. As a result, in the averaging unit 31, the average value of Rx _1, the average value of Rx _2, the average value of Rx _3, the average value of · · Rx _i are obtained, respectively.

Further, the absolute value calculation unit 19 obtains the absolute value of the obtained average value based on the above-described formula. As a result, in the absolute value calculating unit 19, the absolute value of the average value of Rx _1, the absolute value of the average value of Rx _2, the absolute value of the average value of Rx _3, the absolute value of the average value of · · Rx _k respectively Desired.

Then in the mean value calculator 20, the absolute value of the absolute value average of the calculated Rx ₁ in the calculation unit 19, the absolute value of the average value of Rx _2, the absolute value of the average value of Rx _3, the · · Rx _k With respect to the absolute value of the average value, the average of these is further obtained by the following formula.

  That is, in the second embodiment, a sample of a predetermined symbol period is time-sequentially divided into L steps (L is 2 or more) within a unit detection period having an integral multiple of the symbol period. (Integer) and sequentially shifted. Then, for each extracted sample, a correlation value is obtained with a predetermined reference sequence, and this processing is repeatedly executed in K unit detection periods (K is an integer of 2 or more). And the average of the correlation value of a sample is calculated | required between the corresponding steps between all these K unit detection periods. Next, the average of the correlation values obtained for each step is obtained among all L steps.

  Finally, the determination unit 21 compares the obtained average value with a threshold value.

  FIG. 6 shows a block configuration example of a reception signal determination device 3 as a third embodiment to which the present invention is applied. The reception signal determination device 2 includes the TV channel BPF 11, the baseband conversion unit 12, the ADC 13, the time offset correction unit 14 and the frequency offset correction unit 15, the buffer 16, and the averaging connected to the buffer 16. And a selection sliding correlation unit 17 connected to the averaging unit 32, a buffer 18, an absolute value calculation unit 19, an average value calculation unit 20, and a determination unit 21.

  In the third embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof will be omitted.

  The averaging unit 32 performs an averaging process to be described later on the reception signal recorded in the buffer 16. The averaging unit 32 calculates the average and then outputs the average to the selected sliding correlation unit 17.

  Next, the operation of the reception signal determination device 3 as the third embodiment having the above-described configuration will be described.

  Filtering to the pass band by the TV channel BPF 11, frequency conversion to baseband signal by the baseband conversion unit 12, analog-to-digital conversion by the ADC 13, correction so that there is no time difference with respect to the reference sequence by the time offset correction unit 14, frequency offset correction Each process by the unit 15 and the storage process by the buffer 16 are the same as the operation of the first embodiment described above.

  As shown in FIG. 7, the averaging unit 32 cuts out a signal including a unit detection period. Incidentally, the unit detection period may be configured with any length as long as it has an integral multiple of a predetermined symbol period. Next, the averaging unit 32 obtains an average value for the cut unit detection period as shown in FIG.

  Next, the selected sliding correlation unit 17 extracts a sample having a symbol period length within the averaged unit detection period by sequentially shifting a plurality of samples in a time-series manner, and preliminarily defines for each of the extracted samples. A correlation value is obtained from the reference sequence. Since the details are the same as those of the first embodiment of the present invention, the following description is omitted by citing the description.

  In addition, each processing of the buffer 18, the absolute value calculation unit 19, the average value calculation unit 20, and the determination unit 21 subsequent to the selected sliding correlation unit 17 is the same as that of the first embodiment of the present invention.

  As mentioned above, although the structure and operation | movement were demonstrated about Embodiment 2, 3, since it determines also based on the average value of a correlation value by these, it becomes possible to improve determination accuracy more.

  In addition, this invention is not limited to Embodiment 1-3 mentioned above, You may implement by Embodiment 4-6 demonstrated below.

  FIG. 8 shows a block configuration of the fourth embodiment. The fourth embodiment is a received signal determination device 1 ′ as a modification of the first embodiment.

  The received signal determination device 1 ′ includes the TV channel BPF 11, the baseband conversion unit 12, the ADC 13, the time offset correction unit 14, the frequency offset correction unit 15, the buffer 16, the selected sliding correlation unit 17, and the buffer. 18, an absolute value calculation unit 19, an average value calculation unit 20, and a determination unit 21, and an output selection unit 35 is provided between the absolute value calculation unit 19 and the average value calculation unit 20. .

  In the reception signal determination device 1 ′, the same components as those of the reception signal determination device 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The output selection unit 35 selects an arbitrary value or a predetermined condition among the absolute values of the correlation values output from the absolute value calculation unit 19. The output selection unit 35 sends only the absolute value of the selected correlation value to the average value calculation unit 20.

  Whereas the received signal determination device 1 calculates the average of the absolute values of all the correlation values, such a received signal determination device 1 ′ provides only a part of the absolute values of the calculated correlation values. Is selected, and an average is obtained for this.

  FIG. 9 shows a block configuration of the fifth embodiment. The fifth embodiment is a received signal determination device 2 ′ as a modification of the second embodiment.

  The received signal determination device 2 ′ includes a TV channel BPF 11, a baseband conversion unit 12, an ADC 13, a time offset correction unit 14 and a frequency offset correction unit 15, a buffer 16, a selected sliding correlation unit 17, and a buffer 18. , An averaging unit 31, an absolute value calculation unit 19, an average value calculation unit 20, and a determination unit 21, and an output selection unit 35 is provided between the absolute value calculation unit 19 and the average value calculation unit 20. It has been.

  In this reception signal determination device 2 ′, the same components as those of the reception signal determination device 2 are denoted by the same reference numerals, and the description thereof will be omitted.

  Whereas the received signal determination device 2 calculates the average of the absolute values of all the correlation values, such a received signal determination device 2 ′ only provides a part of the absolute values of the calculated correlation values. Is selected, and an average is obtained for this.

  FIG. 10 shows a block configuration of the sixth embodiment. The sixth embodiment is a received signal determination device 3 ′ as a modification of the third embodiment.

  The received signal determination device 3 ′ includes a TV channel BPF 11, a baseband conversion unit 12, an ADC 13, a time offset correction unit 14 and a frequency offset correction unit 15, a buffer 16, an averaging unit 32, and a selective sliding correlation unit. 17, a buffer 18, an absolute value calculation unit 19, an average value calculation unit 20, and a determination unit 21, and an output selection unit 35 is provided between the absolute value calculation unit 19 and the average value calculation unit 20. It has been.

  In the reception signal determination device 3 ′, the same components as those of the reception signal determination device 3 are denoted by the same reference numerals, and the description thereof is omitted below.

  Whereas the received signal determination device 3 calculates the average of the absolute values of all the correlation values, such a received signal determination device 3 ′ provides only a part of the absolute values of the calculated correlation values. Is selected, and an average is obtained for this.

  The processing in the fourth to sixth embodiments described above is expressed by the following formula.

  Here, N is an integer satisfying N ≧ 1 and N ≦ k, and indicates the number of absolute values of the correlation values selected by the output selection unit 35. Rx_sel (j) represents the absolute value of the selected correlation value.

  In Embodiments 4 to 6 described above, the same effects as in Examples 1 to 3 are obtained, and the output selection unit 35 selects only a part of the absolute value of the correlation value. The burden can be reduced, and the cost performance of the apparatus itself can be improved.

1-3 Received signal determination device 11 TV channel BPF
12 Baseband converter 13 ADC
14 time offset correction unit 15 frequency offset correction unit 16 buffer 17 selective sliding correlation unit 18 buffer 19 absolute value calculation unit 20 average value calculation unit 21 determination units 31 and 32 averaging unit

Claims (3)

A sample of a predetermined symbol period from the received signal to be determined is subjected to L steps (L is an integer of 2 or more) over a plurality of unit detection periods having a length that is an integral multiple of the symbol period. Sliding by sequentially shifting and extracting, obtaining a correlation value with a predetermined reference sequence for each extracted sample, and repeatedly executing such processing in K unit detection periods (K is an integer of 2 or more) Correlation calculation means;
For each of the above steps, an average calculating means for each step for obtaining the average of the correlation values of the samples during all the unit detection periods
Correlation average calculation means for obtaining an average between all the steps, with respect to the average of the correlation values obtained for each step by the step average calculation means;
A determination unit that determines whether or not the received signal is a desired signal by comparing an average of correlation values between steps calculated by the correlation average calculation unit and a preset threshold value; A received signal judging device characterized by the above. The received signal determination apparatus according to claim 1, wherein the correlation average calculation means selects only a part of correlation values from all correlation values to be averaged and calculates the average. The correlation average calculating means adds the absolute value of the sum of the obtained positive correlation values and the absolute value of the sum of the obtained negative correlation values, and divides it by the number of correlation values to obtain the average. The received signal determination device according to claim 1, wherein

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