JP2014199996A - Receiver and reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver and a reception method capable of detecting a carrier having a superposed spurious noise with high accuracy.SOLUTION: The receiver according to one aspect in an embodiment includes a receiver unit, an MER calculation unit and a detector unit. The receiver unit receives an OFDM modulated broadcast signal. The MER calculation unit calculates an MER value of the broadcast signal received by the receiver unit on a carrier-by-carrier basis. The detector unit calculates an estimated value of the MER value carrier-by-carrier, on the basis of power that varies according to a broadcast signal transmission path estimated from power of an SP signal included in the broadcast signal, to detect a carrier having a spurious noise superposed thereon, on the basis of the estimated value and the MER value.

Description

  Embodiments disclosed herein relate to a receiving apparatus and a receiving method.

  Conventionally, broadcast signals of DTV (digital television) comply with the OFDM (Orthogonal Frequency Division Multiplexing) system. The OFDM scheme is a signal modulation scheme that improves communication efficiency by transmitting a plurality of data in parallel using a plurality of carriers orthogonal to each other.

  In addition, diversity reception is widely known as a reception method for receiving a DTV broadcast signal by a mobile reception device. A receiving apparatus that performs diversity reception receives broadcast signals in parallel by a plurality of antennas, and synthesizes each broadcast signal so that a larger number of components of the broadcast signal in a good reception state are included. It enables stable signal reception.

  As a method for evaluating whether or not the reception state of a broadcast signal is good, for example, a method of evaluating based on a MER (Modulation Error Ratio) value of a received broadcast signal is known (see, for example, Patent Document 1). .

  The MER value is the distance from the origin to the ideal point corresponding to the reception point of each carrier, the reception point and the corresponding point in the constellation in which the phase and amplitude of each carrier included in the broadcast signal are represented by the I axis and Q axis. It is obtained by the ratio with the vector error of each ideal point.

  Since such a MER value is higher for a carrier having a better reception state, for example, by comparing the MER value with a predetermined threshold for each carrier, it is easily determined whether or not the reception state of the broadcast signal is good. can do.

JP 2009-239750 A

  However, it is difficult to detect a carrier on which spurious noise is superimposed with high accuracy by simply comparing the MER value and the threshold value for each carrier. Specifically, spurious noise is noise that is not intended in design and is generated by harmonics, subharmonics, parasitic vibrations, and the like.

  In such spurious noise, the carrier band to be superimposed varies irregularly depending on the situation. Also, the carrier with spurious noise superimposed has various MER values depending on the situation. Therefore, when the MER value and the threshold value are simply compared for each carrier, there is a risk of detection failure of the carrier on which spurious noise is superimposed.

  One aspect of the embodiments has been made in view of the above, and an object of the present invention is to provide a receiving apparatus and a receiving method that can detect a carrier on which spurious noise is superimposed with high accuracy.

  A receiving device according to an aspect of an embodiment includes a receiving unit, a MER calculating unit, and a detecting unit. The receiving unit receives an OFDM-modulated broadcast signal. The MER calculator calculates the MER value of the broadcast signal received by the receiver for each carrier of the broadcast signal. The detection unit calculates the estimated value of the MER value for each carrier based on the power that changes according to the transmission path of the broadcast signal estimated from the power of the SP signal included in the broadcast signal, and the estimated value And a carrier on which spurious noise is superimposed is detected based on the MER value.

  According to one aspect of the embodiment, a carrier on which spurious noise is superimposed can be detected with high accuracy.

FIG. 1 is an explanatory diagram illustrating a receiving device according to the embodiment. FIG. 2 is an explanatory diagram illustrating a second branch according to the embodiment. FIG. 3 is an explanatory diagram of a MER value calculation method according to the embodiment. FIG. 4 is an explanatory diagram illustrating an example of the MER value for each carrier calculated by the MER calculation unit according to the embodiment. FIG. 5 is an explanatory diagram illustrating a relationship between the transmission line power and the MER value according to the embodiment. FIG. 6 is an explanatory diagram showing fluctuation of the MER value due to fluctuation of IFAGC according to the embodiment. FIG. 7 is an explanatory diagram of a carrier detection method in which spurious noise is superimposed by the detection unit according to the embodiment.

  Hereinafter, embodiments of a receiving device and a receiving method disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  FIG. 1 is an explanatory diagram illustrating a receiving device 1 according to the embodiment, and FIG. 2 is an explanatory diagram illustrating a second branch 2b according to the embodiment. 2 that have the same functions as those shown in FIG. 1 are assigned the same reference numerals as those shown in FIG.

  As shown in FIG. 1, the receiving device 1 according to the embodiment includes a first branch 2a, a second branch 2b, a third branch 2c, which receive broadcast signals of OFDM (Orthogonal Frequency Division Multiplexing) modulated DTV broadcasts, respectively. And a fourth branch 2d.

  The second branch 2b, the third branch 2c, and the fourth branch 2d output the received broadcast signal to the first branch 2a, as indicated by a dashed line arrow in FIG. The first branch 2a combines and outputs the received broadcast signal and the broadcast signals received by the second branch 2b, the third branch 2c, and the fourth branch 2d. That is, the receiving device 1 is a device that receives a broadcast signal with diversity using four receiving systems.

  Each of the first branch 2a, the second branch 2b, the third branch 2c, and the fourth branch 2d includes a detection unit 12 that detects a carrier on which spurious noise is superimposed in the received broadcast signal.

  Then, the second branch 2b, the third branch 2c, and the fourth branch 2d output a signal indicating a carrier on which the detected spurious noise is superimposed to the first branch 2a, as indicated by a dotted arrow in FIG.

  The first branch 2a broadcasts by reducing the influence of the carrier on which the detected spurious noise is superimposed and the carrier on which the spurious noise detected by the second branch 2b, the third branch 2c, and the fourth branch 2d is superimposed. Improve signal reproducibility. Hereinafter, an example of the configuration of the first branch 2a, the second branch 2b, the third branch 2c, and the fourth branch 2d will be described.

  As shown in FIG. 1, the first branch 2 a includes an antenna 3, a receiver 4, an analog / digital converter (hereinafter referred to as “A / D5”), a guard adder 6, and an AGC (Automatic Gain Controller) 7. And a fast Fourier transform unit (hereinafter referred to as “FFT unit 8”). Further, the first branch 2 a includes an equalization unit 9, a transmission path calculation unit 10, a synthesis unit 11, a detection unit 12, a hard decision unit 13, a MER calculation unit 14, an error correction unit 15, and a decoder 16.

  2, the second branch 2b includes an antenna 3, a receiving unit 4, an A / D 5, a guard adding unit 6, an AGC 7, an FFT unit 8, an equalizing unit 9, a transmission path calculating unit 10, and a detecting unit. 12, Hard decision part 13 and MER calculation part 14 are provided. Since the third branch 2c and the fourth branch 2d have the same configuration as the second branch 2b, illustration is omitted here.

  As can be seen by comparing FIG. 1 with FIG. 2, the second branch 2b does not include the synthesis unit 11, the error correction unit 15, and the decoder 16, and the signal output by the equalization unit 9 and the detection unit 12 Except for the point different from the first branch 2a, the configuration is the same as that of the first branch 2a.

  For this reason, the components of the first branch 2a are specifically described here, and the detailed descriptions of the components of the second branch 2b, the third branch 2c, and the fourth branch 2d are omitted.

  The receiving unit 4 is a processing unit that detects a high frequency (RF: Radio Frequency) broadcast signal received by the antenna 3, converts it to an intermediate frequency (IF) broadcast signal, and outputs the broadcast signal to the A / D 5. is there. The A / D 5 is a processing unit that converts an analog broadcast signal from the receiving unit 4 into a digital broadcast signal and outputs the digital broadcast signal to the guard adding unit 6 and the AGC 7.

  The AGC 7 is a processing unit that performs automatic gain adjustment, and automatically adjusts the gain (amplification level) so that the output falls within a predetermined range according to the strength of the broadcast signal of the intermediate frequency input from the A / D 5. The AGC 7 feeds back a value indicating the adjusted amplification level (hereinafter referred to as “IFAGC: Intermediate Frequency Automatic Gain Control”) to the receiving unit 4 and outputs the IFAGC to the detecting unit 12.

  The guard adder 6 adds a guard interval added to the head of the effective symbol included in the broadcast signal input from the A / D 5 to the tail part of the effective symbol and averages (1/2 times) the guard addition. It is a processing part to perform.

  Here, the guard interval is data added by duplicating the tail part of the effective symbol and added to the head of the effective symbol. Therefore, the guard addition unit 6 can restore the data by performing such guard addition even if the data in the tail portion of the effective symbol is damaged due to some cause. The guard addition unit 6 outputs the broadcast signal after the guard addition to the FFT unit 8.

  The FFT unit 8 is a processing unit that converts a time domain broadcast signal input from the guard adder unit 6 into a frequency domain broadcast signal by performing FFT (Fast Fourier Transform). The FFT unit 8 outputs the converted frequency domain broadcast signal to the transmission path calculation unit 10 and the equalization unit 9.

  The transmission path calculation unit 10 has a power value (hereinafter referred to as “transmission path power”) that varies depending on the influence of each carrier on the transmission path for each carrier of the broadcast signal input from the FFT section 8. Is a processing unit for calculating The transmission path calculation unit 10 estimates the transmission path power of each carrier based on an SP (Scattered Pilot) signal having a known phase and amplitude at the time of transmission included in the broadcast signal.

  Specifically, an SP signal at the time of transmission (herein referred to as “transmission SP”) is a signal inserted into a broadcast signal for each carrier of a predetermined frequency, and when expressed in a complex number, an I (real number) component Is a signal known to be “1” and the Q (imaginary number) component is “0”.

  Such a transmission SP is affected by noise, reflection or the like during transmission through the transmission path. For this reason, the SP signal at the time of reception (herein referred to as “reception SP”) has different values for the I component and the Q component from the transmission SP. Here, when the transmission SP is Xsp = asp + ibsp and the transmission path response is H, the reception SP is obtained by H (asp + ibsp).

  At this time, since the I component of the transmission SP is known as asp = 1 and the Q component is known as bsp = 0, the transmission path calculation unit 10 assumes that the I component of the reception SP is A and the Q component is B. The transmission line response of the reception SP can be calculated from the equation H (1 + i × 0) = A + iB. The transmission path calculation unit 10 calculates transmission path power based on the transmission path response thus calculated.

  Further, the transmission path calculation unit 10 calculates the transmission path response of each reception SP, estimates the transmission path response of each carrier based on a function interpolated between the reception SPs, and based on the estimated transmission path response The transmission line power of each carrier is calculated. Then, the transmission path calculation unit 10 outputs the calculated transmission path power to the equalization unit 9 and the detection unit 12.

  The equalization unit 9 performs an equalization process for correcting the broadcast signal input from the FFT unit 8 based on the transmission line power input from the transmission line calculation unit 10, and combines the broadcast signal after the equalization process. 11 is a processing unit that outputs the data to 11.

  Note that the processing up to the equalization processing is also performed in parallel in the second branch 2b, the third branch 2c, and the fourth branch 2d. Then, the equalization unit 9 of the second branch 2b, the third branch 2c, and the fourth branch 2d outputs the broadcast signal after the equalization processing to the hard decision unit 13, and to the synthesis unit 11 of the first branch 2a. Output.

  The combining unit 11 is a processing unit that combines the broadcast signal input from the equalization unit 9 of the first branch 2a and the broadcast signal input from the second branch 2b, the third branch 2c, and the fourth branch 2d. is there.

  Specifically, the synthesis unit 11 outputs the broadcast signal input from the equalization unit 9 to the hard decision unit 13 while holding the broadcast signal for a predetermined holding period. Thereafter, a signal indicating the detection result of the carrier on which spurious noise is superimposed is input from the detection unit 12 to the synthesis unit 11 during the holding period.

  Further, a signal indicating the detection result of the carrier on which the spurious noise is superimposed is also input to the combining unit 11 from the detection units 12 of the second branch 2b, the third branch 2c, and the fourth branch 2d. In addition, the detection method of the carrier on which the spurious noise is superimposed by the detection unit 12 will be described later with reference to FIGS.

  When the combining unit 11 combines a plurality of broadcast signals for each carrier after the retention period has elapsed, a broadcast signal including a carrier on which spurious noise is superimposed based on the signals input from the four detection units 12. Reduces the proportion of the combined broadcast signal. For example, when the broadcast signal input from the second branch 2b includes a carrier in which spurious noise is superimposed, the combining unit 11 determines the ratio of the broadcast signal input from the second branch 2b to the combined broadcast signal. It is reduced more than broadcast signals received by other branches.

  That is, the synthesizing unit 11 synthesizes four broadcast signals by preferentially using a carrier on which spurious noise is not superimposed. Therefore, the synthesizing unit 11 can improve the reproducibility of the broadcast signal by suppressing the deterioration of the broadcast signal due to spurious noise. The combining unit 11 outputs the combined broadcast signal to the hard decision unit 13.

  The hard decision unit 13 is a processing unit that performs a hard decision process on the broadcast signal input from the synthesis unit 11. Specifically, the hard decision unit 13 demaps the reception point corresponding to each carrier of the broadcast signal onto the frequency domain constellation represented by the in-phase component axis (I axis) and the quadrature component axis (Q axis). .

  Each reception point of such a broadcast signal is demapped to a position closer to the ideal point of each mapping frame on the constellation as the influence of noise, reflection, spurious noise, etc. received on the transmission path is lower. The hard decision processing unit 13 outputs the broadcast signal after the hard decision to the error correction unit 15, and outputs position information in the constellation of each demapped reception point to the MER calculation unit 14.

  The MER calculation unit 14 calculates a MER (Modulation Error Ratio) value of the broadcast signal for each carrier based on the position information in the constellation of each reception point input from the hard decision unit 13.

  Here, with reference to FIG. 3 and FIG. 4, an example of a MER value calculation method by the MER calculation unit 14 will be described. FIG. 3 is an explanatory diagram of a MER value calculation method according to the embodiment, and FIG. 4 is an explanatory diagram illustrating an example of a MER value for each carrier calculated by the MER calculation unit 14 according to the embodiment.

  Here, as shown in FIG. 3, the coordinates in the constellation of the reception point P of a certain carrier are (I1, Q1), and the coordinates in the constellation of the ideal point Pi corresponding to the reception point P are (Iid, Qid). The case will be described.

  In such a case, the MER calculation unit 14 calculates the length of the position vector pi of the ideal point Pi in the constellation, that is, the distance from the origin to the ideal point Pi in the constellation. The distance from the origin to the ideal point Pi can be obtained by the following formula (1).

  Subsequently, the MER calculation unit 14 calculates the length of an error vector δ: (δI, δQ) between the position vector p of the reception point P and the position vector pi of the ideal point Pi in the constellation. Here, δI = I1-Iid and δQ = Q1-Qid. Then, the length of the error vector δ is obtained by the following formula (2).

  And the MER calculation part 14 calculates a MER value for every carrier using the calculation result of above-mentioned Numerical formula (1) and Numerical formula (2). The MER value is obtained by the following mathematical formula (3).

  The MER value calculated in this way indicates that the larger the value, the better the reception state of the broadcast signal. Accordingly, the MER value of the carrier whose reception state is deteriorated due to the influence of the transmission path and spurious noise becomes smaller.

  However, the MER value of a carrier on which spurious noise is superimposed varies depending on the situation. Moreover, the spurious noise causes the carrier band to be superimposed to vary irregularly depending on the situation.

  For this reason, for example, the MER value for each carrier as shown in FIG. 4 may be calculated by the MER calculation unit 14. In FIG. 4, from the viewpoint of easily recognizing a carrier whose broadcast signal reception state has deteriorated, the vertical axis represents − (minus) MER value, and the horizontal axis represents the carrier number corresponding to each carrier. ing. That is, FIG. 4 shows that the higher the wave height of the waveform indicating the MER value, the smaller the MER value and the worse the reception state. Similarly, in FIGS. 5 to 7 to be described later, the vertical axis represents −MER value and the horizontal axis represents carrier number.

  Here, it is assumed that a portion surrounded by a dotted line frame in FIG. 4 is a waveform portion of a MER value whose value is reduced due to the influence of spurious noise. In such a case, for example, when detecting the carrier on which the spurious noise is superimposed using the threshold value th indicated by the alternate long and short dash line in FIG. 4, the part surrounded by the dotted line frame on the right side in FIG. 4 is detected. Can do. However, in the part surrounded by the other two dotted line frames, detection failure of the carrier on which spurious noise is superimposed occurs.

  Further, when the threshold value th is increased (lower in FIG. 4) so that all of the portions surrounded by the three dotted frames can be detected, spurious noises up to carriers that are not affected by the spurious noises are also detected. Will be erroneously detected as a carrier affected by. Therefore, the receiving device 1 outputs the calculated MER value from the MER calculation unit 14 to the detection unit 12, and causes the detection unit 12 to detect the carrier affected by the spurious noise with high accuracy.

  The detecting unit 12 calculates an estimated value of the MER value (hereinafter referred to as “estimated MER value”) in which the influence of the transmission path is reflected and the influence of the spurious noise is excluded. Then, the detection unit 12 detects a carrier affected by spurious noise based on the difference between the MER value input from the MER calculation unit 14 and the estimated MER value.

  Hereinafter, a method for detecting a carrier on which spurious noise is superimposed by the detection unit 12 will be described with reference to FIGS. FIG. 5 is an explanatory diagram showing the relationship between the transmission line power and the MER value according to the embodiment, and FIG. 6 is an explanatory diagram showing the fluctuation of the MER value due to the fluctuation of the IFAGC according to the embodiment. FIG. 7 is an explanatory diagram of a carrier detection method in which spurious noise is superimposed by the detection unit 12 according to the embodiment.

  The detection unit 12 calculates an estimated MER value according to the following mathematical formula (4).

  A, B, and C in the above formula (4) are constants determined by conducting a test in advance. For example, when the constant A is determined, a test for receiving a broadcast signal by the receiving apparatus 1 is performed while changing the reception conditions in various ways, and the transmission line power and the MER value calculated under each reception condition are acquired.

  Then, as shown in FIG. 5, the MER value corresponding to the calculated transmission line power is plotted as a point on a coordinate system in which the vertical axis represents −MER value and the horizontal axis represents transmission line power. From FIG. 5, it can be seen that the MER value tends to deteriorate (decrease) as the transmission line power decreases due to the influence of the transmission line.

  Further, in the set of points plotted with the MER values shown in FIG. 5, the point of the MER value plotted at positions far away from the set of points is the MER value of the carrier affected by the spurious noise. Probability is high.

  Therefore, as shown in FIG. 5, a straight line approximating the set of points is calculated after excluding the points plotted at positions far away from the set of points plotted in the coordinate system. And the negative coefficient used as the inclination of the calculated straight line is determined as the constant A of Formula (4). Thereby, the following numerical formula (5) that can calculate the MER value excluding the influence of spurious noise can be obtained.

  Here, if there is no fluctuation of IFAGC, the influence of the transmission path is reflected and the influence of spurious noise is eliminated by substituting the transmission path power estimated from the power of the SP signal into the above formula (5). The estimated MER value obtained can be calculated.

  However, when the receiving apparatus 1 is actually used, IFAGC varies depending on the reception state. When IFAGC fluctuates, transmission line power estimated based on the SP signal fluctuates with fluctuations in IFAGC even if there is no change in transmission line power of the received broadcast signal itself.

Therefore, for example, when a broadcast signal is amplified by AGC 7, as shown in FIG.
When the waveform indicating the accurate MER value of the broadcast signal is a waveform indicated by a solid line, the waveform indicating the estimated MER value has a smaller wave height than the waveform of the solid line, as illustrated by the dotted line. That is, as the estimated MER value, a value with a better reception state than the actual value is calculated.

  Therefore, the detection unit 12 calculates the estimated MER value by the above formula (4) in consideration of the variation of IFAGC. When determining the constant B to be multiplied by IFAGC in Equation (4), for example, during reception of a broadcast signal by the receiving device 1, a test for calculating the MER value by sequentially changing the value of IFAGC is performed. Then, an appropriate value is determined as the constant B based on the correlation between the variation amount of IFAGC and the variation amount of the MER value. For the constant C in the equation (4), the above-described test is performed while sequentially changing the value of the constant C, and the value used in the test in which the accuracy of the estimated MER value is most improved is adopted as the constant C.

  The detection unit 12 uses the mathematical formula (4) to calculate an estimated MER value in which the influence of the transmission path is reflected and the influence of the spurious noise is eliminated. The formula (4) is an example of a formula for calculating the estimated MER value, and may be calculated by the following formula (6), for example.

  Then, the detection unit 12 detects a carrier on which spurious noise is superimposed based on the difference between the MER value input from the MER calculation unit 14 and the estimated MER value.

  For example, the MER value calculated for each carrier as shown in FIG. 7A is input to the detection unit 12 from the MER calculation unit 14. The MER value input from the MER calculation unit 14 is a MER value in which the influence of the transmission path and the influence of spurious noise are reflected. Here, in the waveform of the MER value shown in FIG. 7A, the portion surrounded by a dotted frame is a waveform portion whose value is reduced (the wave height is increased) due to the effect of spurious noise. .

  When the MER value is input from the MER calculation unit 14, the detection unit 12 substitutes the transmission path power input from the transmission path calculation unit 10 and the IFAGC input from the AGC 7 into the above equation (4). The estimated MER value is calculated for each carrier.

  Accordingly, as illustrated in FIG. 7B, the detection unit 12 can calculate, for each carrier, an estimated MER value in which the influence of the transmission path is reflected and the influence of the spurious noise is eliminated. And the detection part 12 correct | amends a MER value by performing the process which takes the difference of the MER value input from the MER calculation part 14, and an estimated MER value.

  As a result, the corrected MER value of the carrier affected by the spurious noise is corrected by other carriers not affected by the spurious noise, as shown by the waveform in the dotted frame in FIG. 7C. It becomes smaller (the wave height is higher) than the later MER value.

  Therefore, the detection unit 12 compares the corrected MER value with the threshold value Th indicated by a dashed line in FIG. 7C, and the corrected MER value is smaller than the threshold value Th (in FIG. 7C). The carrier whose wave height is higher than the threshold value Th is detected as a carrier on which spurious noise is superimposed.

  That is, the detection unit 12 detects the carrier on which the spurious noise is superimposed by comparing the corrected MER value in which the influence of the spurious noise is reflected and the influence of the transmission path is excluded with the threshold Th. Therefore, the detector 12 can detect the carrier on which spurious noise is superimposed with high accuracy.

  When the detection unit 12 detects a carrier on which spurious noise is superimposed, the detection unit 12 outputs a signal indicating the carrier to the synthesis unit 11 and the error correction unit 15. As described above, when the combining unit 11 combines a plurality of broadcast signals for each carrier, based on the signal input from the detection unit 12, a broadcast signal including a carrier on which spurious noise is superimposed is combined. Reduce the percentage of the signal. Here, returning to FIG. 1, the description of the receiving device 1 is continued.

  The error correction unit 15 performs error correction processing such as Viterbi decoding and Reed-Solomon decoding on the broadcast signal after the hard decision input from the hard decision unit 13. A processing unit for each carrier.

  The error correction unit 15 calculates the likelihood of each carrier for each carrier of the broadcast signal, and performs error correction processing based on the likelihood of each carrier. Here, when a signal indicating a carrier on which spurious noise is superimposed is input from the detection unit 12, the error correction unit 15 performs error correction by lowering the likelihood of the carrier on which spurious noise is superimposed compared to other carriers. Then, the error correction unit 15 outputs the broadcast signal subjected to error correction to the decoder 16.

  In this way, the error correction unit 15 performs error correction processing with a lower likelihood than other carriers for carriers that are likely to have data corrupted due to spurious noise, so the accuracy of error correction processing is improved. Can be improved.

  The decoder 16 OFDM-demodulates the broadcast signal input from the error correction unit 15, converts it into a TS (Transport Stream) signal, and outputs it to a predetermined output device. The output device here is, for example, a display that outputs DTV broadcast video, a speaker that outputs DTV broadcast audio, or the like.

  As described above, the receiving apparatus according to the embodiment includes a receiving unit that receives an OFDM-modulated broadcast signal, and a broadcast signal based on the position in the frequency domain of an SP signal included in the broadcast signal received by the receiving unit. A MER calculation unit that calculates the MER value of each carrier.

  Further, the receiving device calculates an estimated value of the MER value for each carrier based on the power that changes in accordance with the transmission path of the broadcast signal estimated from the power of the SP signal, and calculates the estimated value of the MER value and the MER value. Based on this, a detection unit for detecting a carrier on which spurious noise is superimposed is provided.

  In such a receiving apparatus, the MER value reflecting the influence of the transmission path and the influence of the spurious noise and the estimated value of the MER value reflecting the influence of the transmission path and excluding the influence of the spurious noise are calculated. Can do. Thereby, for example, the receiving apparatus calculates a MER value in which the influence of the spurious noise is reflected and the influence of the transmission path is eliminated by taking a difference between the MER value and the estimated value of the MER value. it can.

  Therefore, according to the receiving apparatus, for example, by comparing the MER value in which the influence of the spurious noise is reflected and the influence of the transmission path is excluded with a predetermined threshold value, the carrier on which the spurious noise is superimposed can be accurately detected. Can be detected.

  In addition, the receiving device includes an AGC that automatically adjusts the gain of the power of the received broadcast signal so that the power of the broadcast signal received by the receiving unit is within an appropriate range. When the gain is automatically adjusted by AGC, the detection unit detects a carrier on which spurious noise is superimposed based on the MER value, the estimated value of the MER value, and the gain.

  Therefore, the receiving device can detect the carrier on which the spurious noise is superimposed with high accuracy even if the power changing according to the transmission path of the broadcast signal fluctuates by automatic gain adjustment by AGC.

  The receiving device includes an error correction unit that calculates the likelihood of the broadcast signal for each carrier and performs error correction of the broadcast signal for each carrier based on the likelihood. Then, when the detection unit detects a carrier on which spurious noise is superimposed, the error correction unit performs error correction by lowering the likelihood of the carrier on which spurious noise is superimposed compared to other carriers.

  Therefore, according to the receiving apparatus, it is possible to perform error correction with a lower likelihood than other carriers for carriers that are highly likely to have data corrupted due to spurious noise. Can be improved.

  In addition, the reception device includes a plurality of branches having a reception unit, a MER calculation unit, and a detection unit, and a combining unit that combines broadcast signals received by the plurality of branches. Then, when the detection unit detects a carrier on which spurious noise is superimposed, the combining unit reduces the proportion of the broadcast signal including the carrier on which spurious noise is superimposed in the combined broadcast signal.

  Thereby, the receiving apparatus can synthesize a plurality of broadcast signals by preferentially using a carrier on which spurious noise is not superimposed. Therefore, according to the receiving apparatus, the reproducibility of the broadcast signal can be improved by suppressing the deterioration of the broadcast signal due to spurious noise.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 Receiver 2a 1st branch 2b 2nd branch 2c 3rd branch 2d 4th branch 3 Antenna 4 Receiving part 5 A / D
6 Guard adder 7 AGC
8 FFT unit 9 Equalization unit 10 Transmission path calculation unit 11 Combining unit 12 Detection unit 13 Hard decision unit 14 MER calculation unit 15 Error correction unit 16 Decoder

Claims (5)

A receiving unit that receives an OFDM (Orthogonal Frequency Division Multiplexing) modulated broadcast signal;
A MER calculator that calculates a MER (Modulation Error Ratio) value of the broadcast signal received by the receiver for each carrier of the broadcast signal;
An estimated value of the MER value is calculated for each carrier based on the power that changes in accordance with the transmission path of the broadcast signal estimated from the power of an SP (Scattered Pilot) signal included in the broadcast signal, and the estimated value And a detection unit that detects a carrier on which spurious noise is superimposed based on the MER value. AGC (Automatic Gain Controller) that automatically adjusts the gain of the power so that the power of the broadcast signal received by the receiver falls within an appropriate range.
Further comprising
The detector is
The carrier in which the spurious noise is superimposed is detected based on the MER value, the estimated value of the MER value, and the gain when the gain is automatically adjusted by the AGC. The receiving device described. An error correction unit that calculates the likelihood of the broadcast signal for each carrier, and performs error correction of the broadcast signal for each carrier based on the likelihood; and
The error correction unit is
3. The error correction is performed according to claim 1, wherein when the carrier on which the spurious noise is superimposed is detected by the detection unit, the error correction is performed with a lower likelihood of the carrier than other carriers. Receiver. A plurality of branches having the receiving unit, the MER calculating unit, and the detecting unit;
And a combining unit that combines the broadcast signals received by the plurality of branches,
The synthesis unit is
The ratio of the broadcast signal including the carrier to the combined broadcast signal is reduced when the detection unit detects the carrier on which the spurious noise is superimposed. The receiving device described in 1. Receiving an OFDM modulated broadcast signal;
Calculating a MER value of the received broadcast signal for each carrier of the broadcast signal;
An estimated value of the MER value is calculated for each of the carriers based on the power that changes in accordance with the transmission path of the broadcast signal estimated from the power of the SP signal included in the broadcast signal, and the estimated value and the MER value And a step of detecting a carrier on which spurious noise is superimposed based on the above.

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