JP4584756B2 - Pilot signal detection apparatus and method - Google Patents

Description

  The present invention relates to a technique for detecting a pilot signal of a receiving device, a measuring device, a compensating device, a relay device, etc. for digital broadcasting and digital transmission using an OFDM (Orthogonal Frequency Division Mutiplexing) signal, and in particular, a propagation path. The present invention relates to a symbol timing detection apparatus and method in an SP (Scattered Pilot) arrangement pattern arranged for the purpose of characteristic estimation and equalization.

  In general, a receiving apparatus that receives terrestrial digital broadcasting of ISDB-T (Terrestrial Integrated Services Digital Broadcasting) system uses TMCC (Transmission Multiplexing Configuration) from a carrier symbol that is a frequency domain signal obtained by performing FFT (Fast Fourier Transform) on an input signal. Control: transmission control) is extracted and decoded, and the synchronization signal multiplexed in TMCC is detected to reproduce the frame synchronization timing. At the same time, the symbol timing of the SP arrangement pattern of the 4-symbol period synchronized with the frame synchronization timing is also reproduced. is doing. FIG. 1 is a diagram illustrating an example of a conventional technique for detecting a symbol timing in an SP arrangement pattern having a 4-symbol period by detecting frame synchronization multiplexed in TMCC (see, for example, Non-Patent Document 1). As shown in FIG. 1, the FFT unit 101 performs FFT on the input signal, the TMCC extraction unit 102 extracts TMCC, the TMCC differential demodulation unit 103 performs TMCC demodulation, and the frame synchronization detection unit 104 detects the frame synchronization signal. Then, the SP4 symbol sequence timing detection unit 105 detects the symbol timing of the SP arrangement pattern having a 4-symbol period and outputs it to the compensator signal processing unit 106. In addition, carrier symbol and frequency domain obtained by FFT processing of input signal by preparing symbol data of known SP corresponding to each SP arrangement pattern of four symbols having different arrangement timings in the carrier direction. There is also a method for detecting the symbol timing of the SP arrangement pattern by performing a correlation calculation (see, for example, Patent Document 1). In this case, in order to use the amplitude / phase information of the SPs of the four arrangement patterns, a memory device for storing and holding them and an arithmetic device for performing correlation calculation with the input signal are required.

NHK Giken R & D, May 1999, page 35 JP 2002-335226 A

  The method of detecting the symbol timing of the SP arrangement pattern using frame synchronization multiplexed on the TMCC requires a circuit for extracting and demodulating the TMCC and a circuit for detecting the frame synchronization. At the same time, signal observation and signal processing time are required to demodulate and decode TMCC to detect frame synchronization, and there is a disadvantage that the time required to detect the symbol timing of the SP arrangement pattern becomes long. On the other hand, as in Patent Document 1, a carrier symbol of a frequency domain signal obtained by preparing known SP symbol data of four arrangement patterns corresponding to each symbol of four symbol periods in advance in the receiving apparatus and performing FFT on the input signal The method of performing the correlation calculation with the receiver increases the scale of hardware such as a memory circuit and an arithmetic circuit of the receiving device, and thus hinders cost reduction of the receiving device. In addition, since it is not necessary to demodulate data symbols in a delay profile or propagation characteristic measurement device, circuit elements that are essential for demodulation of data symbols such as TMCC demodulation circuits but are not necessarily required for measurement of propagation path characteristics are used. A simple method is not desired.

  Further, as means for detecting and correcting a frequency error equal to or greater than the subcarrier interval of the ISDB-T OFDM signal, the carrier after FFT is squared and then passed through an inter-symbol filter to correlate with AC, CP, and TMCC arrangement information. There is known a means for detecting a frequency error in units of subcarrier intervals from an arrangement position where the largest correlation coefficient is obtained by calculating the above, but the hardware scale such as a memory circuit and a cross-correlation arithmetic circuit of the receiving device becomes large For this reason, a range of frequency errors that can be detected is not so wide, but a simple method that can be realized with small-scale hardware has been desired. The present invention has been made to answer such a demand.

  An object of the present invention is to provide a technique for detecting a pilot signal that can reduce the amount of hardware and arithmetic processing. Another object of the present invention is to provide a technique that can simultaneously detect and correct a frequency error in units of subcarrier intervals.

  The outline of the invention disclosed in the present application will be briefly described as follows.

  (1) An apparatus for detecting a pilot signal from an OFDM signal in which a pilot signal having a power larger than the average power of a data symbol is arranged in pilot signal arrangement patterns in a plurality of carrier directions in the symbol-carrier space of the OFDM signal. Means for converting the OFDM signal into a carrier symbol which is a signal in the frequency domain, and a carrier at the position of the pilot signal of the pilot signal arrangement pattern for each of the plurality of pilot signal arrangement patterns for one OFDM symbol. Means for calculating the total power of the symbols, and means for detecting the pilot signal arrangement pattern in which the largest power is obtained from the total power of the carrier symbols at the position of the pilot signal of each pilot signal arrangement pattern. is there.

  (2) An apparatus for detecting a pilot signal from an OFDM signal in which a pilot signal having a power larger than the average power of a data symbol is arranged in a symbol-carrier space of the OFDM signal according to a pilot signal arrangement pattern in one or more carrier directions Means for converting the OFDM signal into a carrier symbol that is a frequency domain signal, the one or more pilot signal arrangement patterns, and the one or more pilot signal arrangements for one OFDM symbol. The pilot signal for each of the pilot signal arrangement patterns for the range in which the frequency error is detected, in which the position of the pilot signal is offset to the frequency region corresponding to the case where the signal has a frequency error in units of subcarrier intervals. Of placement pattern Means for calculating the power sum of the carrier symbols at the position of the pilot signal, and means for detecting a pattern in which the maximum value is obtained among the power sums of the carrier symbols of each pilot signal arrangement pattern. Both are detected simultaneously.

  (3) The pilot signal detection apparatus according to (1) or (2), wherein the OFDM signal is arranged for every 12 carriers in the carrier direction, and the insertion position in the carrier direction is set for each OFDM symbol. This is an ISDB-T OFDM signal that is offset by 3 carriers and makes a round with 4 OFDM symbols.

  (4) Pilot of an apparatus for detecting a pilot signal from an OFDM signal in which a pilot signal having a power larger than the average power of a data symbol is arranged in a symbol-carrier space of the OFDM signal according to a pilot signal arrangement pattern in a plurality of carrier directions A signal detection method, the step of converting the OFDM signal into a carrier symbol that is a frequency domain signal, and a pilot of the pilot signal arrangement pattern for each of the plurality of pilot signal arrangement patterns for one OFDM symbol Calculating the total power of the carrier symbols at the signal position, and detecting the pilot signal arrangement pattern with the highest power among the total power of the carrier symbols at the pilot signal positions of each pilot signal arrangement pattern A step, and has a.

  As in the prior art, a method of obtaining the symbol timing of the SP arrangement pattern having a 4-symbol period by detecting the frame synchronization multiplexed in the TMCC, the SP arrangement pattern and the known amplitude / phase data of the SP are previously stored in the receiving apparatus. Compared with the method of preparing and obtaining the symbol timing of the SP arrangement pattern having a 4-symbol period by correlation calculation, the present invention enables reduction of hardware and calculation processing amount. Furthermore, detection and correction of frequency errors in units of subcarrier intervals can be realized at the same time.

(Embodiment 1)
The first embodiment will be described below.

  For example, in the case of an ISDB-T signal, pilot signals called SPs are distributed and arranged according to pilot signal arrangement patterns in four carrier directions in the symbol-carrier space of the OFDM signal. FIG. 2 shows the arrangement of SPs in the synchronization segment of the ISDB-T signal (mode 3). The SP has a known amplitude and phase, and as shown in FIG. 2, in the carrier-symbol space, the insertion position in the carrier direction is offset by 3 carriers for each symbol in the carrier direction every 12 carriers in the carrier direction. An arrangement pattern that makes a round with 4 symbols is used. In order to extract the SP from the received signal in the receiving apparatus, it is necessary to detect which timing symbol of the SP arrangement pattern in the carrier direction of the 4-symbol period is the current symbol.

In addition, the average power per carrier of a carrier symbol for transmitting video / audio data compressed by the MPEG system, that is, a data symbol, depends on the modulation system by standardizing the amplitude with a constant according to the modulation system. It becomes constant (1.0) without doing. On the other hand, the SP amplitude is 4/3 times the average amplitude of the data symbols. Therefore, considering the power per subcarrier, the power of SP is (4/3) ² times (= about 1.78 times) the average power of data symbols. The “carrier symbol” here is used in the description of “3.12.2 OFDM segment configuration of synchronous modulation unit” in ARIB STD-B31, and is a term for distinguishing each subcarrier. .

In the case of an ISDB-T signal, the SP arrangement position in each segment is a carrier number: (12N + MN: a positive number of 0 or more) as shown in FIG. 2, and the SP arrangement pattern is M = 0, 3, 6, 9 In terms of
When arranged in the carrier number (0, 12, 24, 36,...): Pattern A,
When arranged in the carrier number (3, 15, 27, 39,...): Pattern B,
When arranged in the carrier number (6, 18, 30, 42, ...): pattern C,
When arranged in the carrier number (9, 21, 33, 45, ...): pattern D,
There are four SP arrangement patterns in the carrier direction, and the pattern changes from A to D for each symbol and is repeated in a cycle of 4 symbols. In FIG. 2, OFDM symbol number 0 is pattern A, OFDM symbol number 1 is pattern B, OFDM symbol number 2 is pattern C, OFDM symbol number 3 is pattern D, and OFDM symbol number 4 is pattern. A,..., OFDM symbol number 203 is pattern D. In order to detect which pattern A to D corresponds to the SP arrangement pattern of the OFDM symbol of the input signal, first, the carrier symbol at the arrangement position indicated by each pattern is regarded as an SP, and the power sum is calculated for each pattern. To do. For example, if the OFDM symbol of the input signal is OFDM symbol number 0 in FIG. 2, the power of carrier numbers 0, 12, 24, 36,... Is added to OFDM symbol number 0 in FIG. The power is summed, the powers of carrier numbers 3, 15, 27, 39,... Are added to obtain the power sum in pattern B, and the powers of carrier numbers 6, 18, 30, 42,. The power sum in C is added, and the powers of carrier numbers 9, 21, 33, 45. Next, the power sums in the patterns are compared, and if the pattern with the largest power sum is selected, the pattern indicates the correct SP arrangement pattern of the OFDM symbol. This is because the power of the SP is about 1.78 times larger than the average power of the data symbols, and any one of the four patterns matches all the SP placement positions. This is because there is no coincidence with the SP arrangement position. For example, if the OFDM symbol of the input signal is OFDM symbol number 0 in FIG. 2, pattern A is selected.

  FIG. 3 shows a block diagram of a signal processing circuit according to this embodiment. In the embodiment of FIG. 3, the symbol timing in the SP arrangement pattern of the 4-symbol period of the ISDB-T OFDM signal is detected, and the frequency characteristic of the transmission path is calculated using the SP extracted based on the detection result. Is. As shown in FIG. 3, an ISDB-T OFDM signal input to the receiving apparatus is converted into a carrier symbol which is a frequency domain signal by an FFT unit 301. FIG. 4 shows a state in which the time domain OFDM signal is converted into a frequency domain signal by the FFT unit 301.

  FIG. 4 shows a waveform in the time domain before FFT, an image of carrier symbols in the frequency domain after FFT, and patterns A to D for the OFDM signal. Reference numeral 401 denotes a waveform before FFT (the horizontal axis is the time axis, and the vertical axis is the amplitude). Reference numeral 402 denotes an image of the carrier symbol after FFT (the horizontal axis is the frequency axis, and the vertical axis is the amplitude). The long arrow indicates the SP amplitude, and the short arrow indicates the data symbol amplitude. In FIG. 4, as indicated by 403, the SP arrangement of each symbol (the position of the carrier symbol for calculating the power sum) in the SP arrangement of the 4-symbol period is also shown.

  In the case of the ISDB-T system, in order to detect the SP arrangement pattern of the current OFDM symbol, four arrangement patterns (1) to (4) represented by the following equations (1) to (4) are detected for this carrier symbol in the frequency domain. The sum of the power of the carrier symbols of the subcarrier numbers A to D) is calculated.

However, N is a positive number of 0 or more.

  Assuming that the total power of the carrier symbols of the subcarrier numbers of the patterns (A to D) is Ap to Dp, Ap to Dp can be expressed by the following equations (5) to (8).

Where P (m) is the power of the carrier symbol with the subcarrier number m, k is a positive number greater than or equal to 0, N is the number of SPs included in one OFDM symbol, and in the case of mode 3 in the ISDB-T system 468.

  This calculation is performed by the carrier symbol power adding section 302 shown in FIG. That is, the pattern A power addition unit of the carrier symbol power addition unit 302 performs calculation of Equation (5), the pattern B power addition unit performs calculation of Equation (6), and the pattern C power addition unit performs calculation of Equation (7). The pattern D power adding unit performs the calculation of equation (8), and outputs the result of the addition of each power adding unit to the maximum value determining / pattern detecting unit 303.

Note that if F (ω _m ) is the result of FFT of the input signal of the receiving device, P (m) can be expressed by equation (9).

Here, F ^* (ω _m ) represents a complex conjugate of F (ω _m ), m represents a subcarrier number, and ω _m represents an angular frequency of the mth subcarrier.

  That is, since Ap to Dp can be calculated by multiplication and addition of complex numbers, the circuit scale can be relatively small.

In any case, in the patterns A to D, when the SP arrangement position designated by each pattern matches the actual SP arrangement position, the total power of the carrier symbol is maximized.
When Ap reaches the maximum value, the SP arrangement is pattern A,
When Bp reaches the maximum value, the arrangement of SP is pattern B,
When Cp reaches the maximum value, the SP arrangement is pattern C,
When Dp reaches the maximum value, the arrangement of SP is pattern D,
Then, the maximum value determination / pattern detection unit 303 determines and the pattern number from which the maximum value is obtained is output to the SP arrangement pattern generation unit.

  Next, the SP arrangement pattern generation unit 304 needs any one of the patterns A to D when the SP separation extraction unit 305 extracts SP from the pattern number input from the maximum value determination / pattern detection unit 303. Information is generated and output to the SP separation / extraction unit 305.

  The SP separation / extraction unit 305 separates and extracts SP symbol data (amplitude / phase) based on the SP arrangement pattern information input from the SP arrangement pattern generation unit 304.

  Since the SP has known amplitude and phase at the time of signal generation (at the time of transmission) as described above, the received SP supplied from the SP separation / extraction unit 305 in the transmission line characteristic calculation unit 306 as shown in FIG. The carrier symbol S (n, k) is complex-divided by the carrier symbol X (n, k) of the SP (transmission SP) at the time of signal generation generated and supplied by the transmission SP generation unit 307 (formula (10)) The frequency characteristic F (n, k) of the propagation path is calculated and output to the compensator signal processing unit 308.

Here, n represents a carrier number, and k represents a symbol number.

  In the case of a receiver, the frequency characteristics of the propagation path obtained here are used for the compensation of fading of the transmission path and the distortion of the frequency characteristics due to multipath in the transmission path equalization unit, and for the broadcast wave relay etc. In the case of various compensators, it is used to remove various interferences in signal processing.

  In the above description, an ISDB-T OFDM signal having an SP arrangement pattern of 4 OFDM symbol periods has been described. However, a plurality of pilot signals having a power higher than the average power of data symbols are present in the symbol-carrier space of the OFDM signal. The same applies to OFDM signals arranged according to the pilot signal arrangement pattern in the carrier direction. That is, generally speaking, the apparatus for detecting a pilot signal according to the present embodiment includes a means for converting a received OFDM signal into a carrier symbol which is a frequency domain signal, and a plurality of OFDM symbols for one OFDM symbol. Means for calculating the total power of the carrier symbols at the pilot signal positions of the pilot signal arrangement pattern for each of the pilot signal arrangement patterns of And a means for detecting a pilot signal arrangement pattern from which large electric power is obtained.

(Embodiment 2)
The second embodiment will be described below.

  The frequency accuracy of the local signal transmitter of the frequency converter of the transmission apparatus is poor, the carrier symbol after FFT has a frequency error greater than or equal to the subcarrier interval of the OFDM signal, and each carrier symbol is not at a specified sample position in the frequency domain In this case, a plurality of patterns of carrier symbol power sum calculators for calculating the power sum of carrier symbols with SP arrangement patterns having a frequency offset in units of subcarrier intervals are prepared, and each carrier symbol power sum calculator is The output power sum is input to the maximum value detection unit, and the carrier symbol power sum calculation unit that outputs the largest power sum is determined and detected. Next, the number of the carrier symbol power sum calculation unit that has calculated the largest carrier symbol power sum output by the maximum detection unit is input to the frequency error detection unit, and the carrier symbol power sum calculation unit uses the frequency error detection unit. A frequency error amount is detected from the SP arrangement pattern, and the detected frequency error amount is supplied to the frequency error correction unit. The frequency error correcting unit corrects the frequency error based on the supplied frequency error information, thereby realizing correct demodulation processing. However, it is assumed that the frequency error within the subcarrier interval is detected and corrected in advance by a frequency error detection method using guard interval correlation. Since the frequency error detection / correction technique using the guard interval correlation is a known technique, a detailed description thereof will be omitted.

  FIGS. 5 and 6 show examples in which the technique for detecting and correcting the frequency error in units of subcarrier intervals according to the present embodiment is applied to an ISDB-T signal. The patterns A, B, C, and D shown on the upper side of FIG. 5 are the same as the patterns A, B, C, and D shown in 403 of FIG. 4 described in the first embodiment, and the carrier number at the position of ● It is shown that the power sum is calculated for. In this example, it is unknown whether the current OFDM symbol of the input signal corresponds to the number of symbols in the SP arrangement pattern having a 4-symbol period, and as shown in the lower diagram of FIG. 5, a total of 12 (A (− 1), A (0), A (+1), B (-1)... C (+1), D (-1), D (0), D (+1)) SP arrangement patterns in the carrier direction. Prepare the power sum of the carrier symbols in each pattern. The x position in the lower diagram of FIG. 5 is the position where the power sum is calculated. The X position of A (0) coincides with the position of ● in the upper figure, and A (0) is an SP arrangement pattern for detecting a case where there is no frequency error. A (-1) is a pattern in which A (0) is offset to the lower frequency by one subcarrier interval, and is an SP arrangement pattern for detecting a case where the frequency is shifted to the lower side. A (+1) is a pattern in which A (0) is offset to the higher frequency by one subcarrier interval, and is an SP arrangement pattern for detecting a case where the frequency is shifted to the higher side. The same applies to B (-1) to D (+1). When the SP arrangement patterns A (−1) to D (+1) in FIG. 5 are expressed as equations, equations (11) to (22) are obtained.

However, N is a positive number of 0 or more.

  Assuming that the sum of the power in each pattern of the carrier symbol of the subcarrier number indicated by each pattern (A (−1) to D (+1)) is Ap (−1) to Dp (+1), Ap (−1) ) To Dp (+1) can be expressed by the following equations (23) to (34).

Where P (m) is the power of the carrier symbol with the subcarrier number m, k is a positive number greater than or equal to 0, N is the number of SPs included in one OFDM symbol, and in the case of mode 3 in the ISDB-T system 468.

  FIG. 6 shows a block diagram when the frequency error is detected and corrected by the ISDB-T method. In FIG. 6, FFT section 601 converts an input signal into a frequency domain signal and outputs the signal to carrier symbol power sum calculation section 602. The pattern A (-1) power sum calculation unit to the pattern D (+1) power sum calculation unit of the carrier symbol power sum calculation unit 602 calculate the power sum of each SP arrangement pattern using Equations (23) to (34). And output to the maximum value detection unit 603. Maximum value detecting section 603 detects the maximum value from the power sums in the respective SP arrangement patterns, and outputs the number of the carrier symbol power sum calculating section that has calculated the largest carrier symbol power sum to frequency error amount detecting section 604. To do. The frequency error amount detection unit 604 detects a frequency error from the SP arrangement pattern used by the carrier symbol power sum calculation unit of the input number, and outputs the detected frequency error information to the frequency error correction unit 605. The frequency error correction unit 605 corrects the frequency error based on the frequency error information.

  According to the present embodiment, it is possible to simultaneously detect the frequency error and the symbol number in the SP arrangement pattern of the 4-symbol period by detecting the pattern of the carrier symbol power sum calculation unit 602 from which the maximum value is obtained. For example, if the output of the pattern detection unit A (-1) power sum calculation unit is maximum, the frequency error whose frequency is shifted by one subcarrier interval and the symbol number in the pattern A can be detected at the same time. If the output of the unit A (0) power sum calculation unit is maximum, it is possible to detect the frequency error and the symbol number in the pattern A at the same time, and if the output of the pattern detection unit A (+1) power sum calculation unit is maximum. The frequency error in which the frequency is shifted higher by one subcarrier interval and the symbol number in the pattern A can be detected simultaneously. The same applies when the outputs of the pattern B (-1) power sum calculation unit to the pattern D (+1) power sum calculation unit are maximum. In the case of the ISDB-T system, the frequency error range of the subcarrier interval that can be detected is ± 1 subcarrier since there are 3 subcarrier intervals in the carrier direction as seen in the entire SP symbol pattern of 4 symbol periods. On the other hand, when the symbol number in the SP arrangement pattern of the 4-symbol period of the observed OFDM symbol is known, the frequency error in the range of +5 to −6 subcarrier or +6 to −5 subcarrier is detected and corrected. it can.

  Further, in the present embodiment, the frequency of CP (Continual Pilot) used in the OFDM signal of the frame configuration using the portable OFDM digital radio transmission system for transmitting television broadcast program material defined in ARIB STD-B33. It can also be applied when detecting and correcting errors. FIG. 7 shows an example of an OFDM frame configuration for FPU in the 2K full mode. In the case of FIG. 7, the pilot signal is CP. In the case of FIG. 5 which has already been described, there are four types of SP arrangement patterns in the carrier direction: patterns A, B, C and D, but in the case of FIG. 7, there is one type of CP arrangement pattern in the carrier direction. In the case of the present embodiment, a pilot signal arrangement pattern obtained by offsetting the OFDM signal pilot signal to higher and lower frequencies is used together with the pilot signal arrangement pattern of the OFDM signal. Even in an OFDM signal arranged according to an arrangement pattern, it is possible to detect a CP position and frequency error by detecting a pattern in which the maximum value is obtained from the power sum of carrier symbols of a plurality of CP arrangement patterns. is there.

  In the present embodiment, in the OFDM signal, pilot signals having a power higher than the average power of data symbols may be arranged in a pilot signal arrangement pattern in one or more carrier directions in the symbol-carrier space of the OFDM signal. Generally speaking, an apparatus for detecting a pilot signal according to the present embodiment includes means for converting an OFDM signal into a carrier symbol that is a frequency domain signal, and one or more of the one or more OFDM symbols for one OFDM symbol. With respect to the pilot signal arrangement pattern and the one or more pilot signal arrangement patterns, a frequency error in which the position of the pilot signal is offset in a frequency region corresponding to a case where the signal has a frequency error in units of subcarrier intervals. Means for calculating the power sum of carrier symbols at the pilot signal positions of the pilot signal arrangement pattern for each of the pilot signal arrangement patterns for the range to be detected, and the maximum value among the power sums of the carrier symbols of each pilot signal arrangement pattern Means for detecting a pattern obtained from It is sufficient. In the present embodiment, both the pilot signal and the frequency error can be detected simultaneously.

  As described above, the first and second embodiments have been described in detail. In any of the embodiments, the pilot signal is detected by using the difference between the pilot signal power and the average power of the data symbols.

  In the embodiment using the pilot signal arrangement pattern, it is not necessary to store all the arrangement positions of the pilot signal arrangement patterns of the carrier symbols for calculating the power sum. It should be added that since the three pieces of information “number of carrier symbols” can be generated, the scale of the memory circuit required for the apparatus is extremely small.

  In the description of each embodiment, the receiving apparatus has been described as an example. However, as long as the apparatus detects a pilot signal, the measuring apparatus, the compensating apparatus, the relay apparatus, or another apparatus that processes OFDM signals. It may be.

  The apparatus according to each embodiment can be configured by an electronic circuit, and a part or all of the apparatus may be configured by a CPU or DSP (Digital Signal Processor) and a program stored in a storage device.

  Although the invention made by the present inventor has been specifically described based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. Of course.

It is a figure which shows an example of a prior art. It is a figure which shows the symbol-carrier space display in the case of ISDB-T system OFDM segment structure mode 3. FIG. It is a block diagram of the signal processing circuit of Embodiment 1 (in the case of ISDB-T system) of the present invention. It is a figure which shows the signal image before and behind the FFT process of OFDM signal, and pattern AD. It is a figure which shows the example of the electric power addition pattern in the case of detecting and correct | amending a frequency error in an ISDB-T system. It is a block diagram of the signal processing circuit of Embodiment 3 (Frequency error detection / correction in ISDB-T system) of the present invention. It is a figure which shows the OFDM frame structure in the case of 2K full mode of the portable OFDM system digital radio transmission system for television broadcast program material transmission prescribed | regulated by ARIB STD-B33.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... FFT part 102 ... TMCC extraction part 103 ... TMCC differential demodulation part 104 ... Frame synchronization detection part 105 ... SP4 symbol sequence timing detection part 106 ... Compensator signal processing part 301 ... FFT part 302 ... Carrier symbol power addition unit, 303... Maximum value determination / pattern detection unit, 304... SP arrangement pattern generation unit, 305. SP separation extraction unit, 306... Transmission path characteristic detection unit (division unit), 307. 308: Compensator signal processing unit 401: Waveform before FFT, 402 ... Image of carrier symbol after FFT, 403 ... Position of carrier symbol for calculating power sum, 601 ... FFT unit, 602 ... Carrier symbol power sum calculation unit 603 ... Maximum value detection unit 604 ... Frequency error amount detection unit 605 ... Frequency error correction unit

Claims (4)

An apparatus for detecting a pilot signal from an OFDM signal in which a pilot signal having a power greater than the average power of a data symbol is arranged in a pilot signal arrangement pattern in a plurality of carrier directions in a symbol-carrier space of the OFDM signal,
Means for converting the OFDM signal into a carrier symbol which is a frequency domain signal;
Means for calculating a total power of carrier symbols at positions of pilot signals of the pilot signal arrangement pattern for each of the plurality of pilot signal arrangement patterns for one OFDM symbol;
Means for detecting a pilot signal arrangement pattern in which the largest power is obtained from the total power of carrier symbols at the position of the pilot signal of each pilot signal arrangement pattern;
A pilot signal detection apparatus comprising: An apparatus for detecting a pilot signal from an OFDM signal in which a pilot signal having a power larger than an average power of a data symbol is arranged in a symbol-carrier space of the OFDM signal according to a pilot signal arrangement pattern in one or more carrier directions. ,
Means for converting the OFDM signal into a carrier symbol which is a frequency domain signal;
A frequency region corresponding to a case where a signal has a frequency error in units of subcarrier intervals with respect to one or more pilot signal arrangement patterns and one or more pilot signal arrangement patterns for one OFDM symbol. Means for calculating the power sum of the carrier symbols at the pilot signal positions of the pilot signal arrangement pattern for each of the pilot signal arrangement patterns for the range in which the frequency error is detected, the position of the pilot signal being offset to
Means for detecting a pattern in which the maximum value is obtained among the power sums of carrier symbols of each pilot signal arrangement pattern;
And a pilot signal detecting device for simultaneously detecting both a pilot signal and a frequency error. In the pilot signal detection device according to claim 1 or 2,
The OFDM signal is an OFDM signal of the ISDB-T system in which a pilot signal is arranged every 12 carriers in the carrier direction, and the insertion position in the carrier direction is offset by 3 carriers for each OFDM symbol and makes a round of 4 OFDM symbols. Pilot signal detection device. Pilot signal detection method for an apparatus for detecting a pilot signal from an OFDM signal in which a pilot signal having a power greater than the average power of a data symbol is arranged in pilot signal arrangement patterns in a plurality of carrier directions in a symbol-carrier space of the OFDM signal Because
Transforming the OFDM signal into a carrier symbol that is a frequency domain signal;
Calculating a total power of carrier symbols at positions of pilot signals of the pilot signal arrangement pattern for each of the plurality of pilot signal arrangement patterns for one OFDM symbol;
Detecting a pilot signal arrangement pattern in which the largest power is obtained from the total power of carrier symbols at the position of the pilot signal of each pilot signal arrangement pattern;
A pilot signal detection method comprising:

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