JP4516489B2 - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide techniques with which frequency characteristics can be estimated more accurately in a mobile reception environment. <P>SOLUTION: The reception apparatus for receiving a transmission signal of a digital transmission scheme in which an SP (Scattered Pilot) is inserted using an OFDM modulation scheme, comprises: a frequency characteristic estimation unit 110 including a frequency characteristic estimation section 1 for estimating frequency characteristics using SPs of preceding and following three symbols and a frequency characteristic estimation section 2 for estimating frequency characteristics symbol by symbol; an amplitude variation detection unit 112 for detecting the amplitude variation of a carrier sent out for each symbol with a fixed amplitude; and a switcher 114 for switching the frequency characteristics resulting from the frequency characteristic estimation sections 1, 2 in accordance with a variation speed resulting from the amplitude variation detection unit 112. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a receiving apparatus of a radio communication system using OFDM (Orthogonal Frequency Division Multiplexing), which is a multicarrier modulation system, such as terrestrial digital television broadcasting or terrestrial digital audio broadcasting, and particularly mobile This is a receiving apparatus that can receive high-quality information even in a poor radio propagation environment such as reception.

  In the Japanese terrestrial digital broadcasting system, as shown in FIG. 4, a pilot signal (SP: Scattered Pilot) is inserted every 12 carriers in each OFDM symbol, and the position of the pilot carrier is shifted by 3 carriers between the preceding and following symbols. It is arranged. Since SP is a known value on the receiving side, it is possible to estimate the channel characteristics at the frequency of the carrier position from the received SP value and the true SP value. The channel characteristics of carriers other than the SP carrier are obtained by interpolation processing, and the received signal is equalized by complex division of the received signal using the frequency characteristics of the channel thus obtained. As a method of interpolating the transmission line characteristics, a method of performing interpolation processing in the frequency direction for each symbol, or an interpolation processing in the time axis direction using SP for three symbols before and after, as shown in FIG. After that, there is a method of performing interpolation processing in the frequency direction. For example, Patent Document 1 describes a method of performing only interpolation processing in the frequency direction for each symbol. Patent Document 2 describes a technique for performing interpolation in the frequency axis direction after performing interpolation in the time axis direction.

Japanese Patent Laid-Open No. 2002-9724 JP 2003-174427 A

  In the method of performing interpolation in the frequency direction after performing the interpolation processing in the time axis direction using SPs of three symbols before and after (hereinafter, time interpolation + frequency interpolation method), the resolution in the frequency direction can be increased. Therefore, the frequency characteristic can be estimated even in the presence of a longer delayed wave, but there is a problem that the estimation accuracy is lowered in a reception environment where the frequency characteristic is constantly changing, such as a high-speed mobile reception environment. On the other hand, in the method of performing only frequency direction interpolation processing for each symbol (hereinafter referred to as frequency interpolation method for each symbol), there is a long delay wave although it is strong against time changes such as a high-speed mobile reception environment. In such an environment, there is a problem that the estimation accuracy is lowered.

  The present invention has been made in view of such problems, and an object of the present invention is to change the transmission line characteristics constantly by selectively switching these interpolation processes in accordance with changes in the mobile reception environment. It is an object of the present invention to provide a technique capable of performing frequency characteristic estimation with higher accuracy even in a receiving environment.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

(1) A first frequency characteristic estimator that estimates frequency characteristics using SPs of three symbols before and after, in a receiving apparatus that receives a transmission signal of a digital transmission scheme in which an SP (Scattered Pilot) is inserted using the OFDM modulation scheme And a second frequency characteristic estimator for estimating frequency characteristics in units of one symbol, amplitude fluctuation detecting means for detecting an amplitude fluctuation of a carrier transmitted every symbol with a constant amplitude, and the amplitude Switching means for switching the frequency characteristics obtained from the first frequency characteristic estimation unit or the second frequency characteristic estimation unit according to the fluctuation speed obtained by the fluctuation detection means, the amplitude fluctuation detection means, a carrier that is delivered every symbol by the constant amplitude, CP, TMCC, among AC, to detect the amplitude variation with at least one carrier, It demodulates the OFDM signal by switching the frequency characteristic in serial switching means.

(2) In a diversity reception system receiver that receives a transmission signal of a digital transmission system in which an SP is inserted using an OFDM modulation system, a frequency characteristic is estimated using SPs of three symbols before and after each branch. Frequency characteristic estimator having a frequency characteristic estimator and a second frequency characteristic estimator for estimating frequency characteristics in units of one symbol, and amplitude fluctuation detection for detecting amplitude fluctuation of a carrier transmitted at a constant amplitude every symbol and means, in response to said variation rate obtained by the amplitude fluctuation detection means and a switching means for switching the frequency characteristic obtained from the first frequency characteristic estimation unit or the second frequency characteristic estimation unit, the amplitude The fluctuation detecting means detects at least one carrier of CP, TMCC, and AC, which is a carrier transmitted at every symbol with the constant amplitude. There detects the amplitude variation, demodulates the OFDM signal subjected to calculation to diversity synthesizing synthesis coefficients from the frequency characteristics of each branch output from the switching means of each branch.

(3) A first frequency characteristic estimator that estimates frequency characteristics using SPs of three symbols before and after, in a receiving apparatus that receives a transmission signal of a digital transmission scheme in which an SP (Scattered Pilot) is inserted using the OFDM modulation scheme And a second frequency characteristic estimator for estimating frequency characteristics in units of one symbol, amplitude fluctuation detecting means for detecting an amplitude fluctuation of a carrier transmitted every symbol with a constant amplitude, and the amplitude Switching means for switching the frequency characteristic obtained from the first frequency characteristic estimation unit or the second frequency characteristic estimation unit according to the fluctuation speed obtained by the fluctuation detection means, and the second frequency characteristic estimation When the carrier at the band edge of the symbol is not SP or CP, the part is interpolated from the SP at the band edge of the preceding and following symbols, and S at the band edge of the preceding and following symbols. By using P, or by using SP or CP having the closest frequency in the symbol, the amplitude phase reference of the band edge carrier of the symbol is obtained, and the amplitude phase reference of the band edge carrier is used. When the SP is extrapolated outside the symbol band and the carrier at the end of the symbol band is SP or CP, the SP is extrapolated outside the band of the symbol using the value of the SP or CP, and is extrapolated outside the band. The inserted SP is also used to estimate the frequency characteristic of the symbol, and the switching means switches the frequency characteristic to demodulate the OFDM signal .

(4) In a diversity reception system reception apparatus that receives a transmission signal of a digital transmission system in which an SP is inserted using an OFDM modulation system, a frequency characteristic is estimated using an SP of 3 symbols before and after each branch . Frequency characteristic estimator having a frequency characteristic estimator and a second frequency characteristic estimator for estimating frequency characteristics in units of one symbol, and amplitude fluctuation detection for detecting amplitude fluctuation of a carrier transmitted at a constant amplitude every symbol and means, in response to said variation rate obtained by the amplitude fluctuation detection means and a switching means for switching the frequency characteristic obtained from the first frequency characteristic estimation unit or the second frequency characteristic estimation unit, said first If the carrier at the band edge of the symbol is not SP or CP, the frequency characteristic estimation unit 2 interpolates from the SP at the band edge of the preceding and following symbols. By using the SP at the band edge of the symbol, or the SP or CP having the closest frequency in the symbol, the amplitude phase reference of the carrier at the band edge of the symbol is obtained, and the amplitude of the carrier at the band edge SP is extrapolated outside the band of the symbol using the phase reference, and if the carrier at the band edge of the symbol is SP or CP, the SP is extrapolated outside the band of the symbol using the value of SP or CP. Then, using the SP extrapolated outside the band, the frequency characteristic of the symbol is estimated, and the synthesis coefficient is calculated from the frequency characteristic of each branch output from the switching unit of each branch, and diversity combining is performed. It demodulates the OFDM signal.

(5) In the reception device that will receive the transmission signal of a digital transmission system SP is inserted with OFDM modulation scheme, the first frequency characteristic estimation unit for estimating the frequency characteristics using the SP before after 3 symbols Frequency characteristic estimation means having a second frequency characteristic estimation unit that estimates frequency characteristics in units of one symbol, and the speed of the moving object is measured by GPS, or the traveling speed measured by the speedometer provided in the moving object is captured. According to the moving speed detecting means, the amplitude fluctuation estimating means for estimating the amplitude fluctuation from the speed of the moving body obtained by the moving speed detecting means, and the first fluctuation according to the fluctuation speed obtained by the amplitude fluctuation estimating means. and a switching means for switching the frequency characteristics obtained from the frequency characteristic estimation unit or the second frequency characteristic estimating unit, the second frequency characteristic estimation unit, a band of the symbol If the carrier at the end is not SP or CP, the SP at the band edge of the preceding and following symbols is interpolated from the SP at the band edge of the preceding and following symbols, or the SP or CP having the closest frequency in the symbol is used. Thus, the amplitude phase reference of the carrier at the band end of the symbol is obtained, and the SP is extrapolated outside the band of the symbol using the amplitude phase reference of the carrier at the band end, and the carrier at the band end of the symbol is SP or If it is a CP, extrapolate the SP outside the band of the symbol using the SP or CP value, estimate the frequency characteristic of the symbol using the SP extrapolated outside the band, and The switching means switches the frequency characteristics and demodulates the OFDM signal.

(6) In a diversity reception system receiver that receives a transmission signal of a digital transmission system in which an SP is inserted using an OFDM modulation system, a frequency characteristic is estimated using SPs of three symbols before and after each branch. Frequency characteristic estimation means having a second frequency characteristic estimation unit for estimating frequency characteristics in units of one symbol and a frequency characteristic estimation unit that measures the speed of the moving object with GPS, or measures with a speedometer provided in the moving object According to the fluctuation speed obtained by the amplitude fluctuation estimation means for estimating the amplitude fluctuation from the speed of the moving body obtained by the movement speed detection means, Switching means for switching the frequency characteristic obtained from the first frequency characteristic estimation unit or the second frequency characteristic estimation unit, If the carrier at the band edge of the symbol is not SP or CP, the second frequency characteristic estimation unit interpolates from the SP at the band edge of the preceding or following symbol, uses the SP at the band edge of the preceding or following symbol, or By using the SP or CP having the closest frequency in the symbol, the amplitude phase reference of the carrier at the band end of the symbol is obtained, and the SP outside the band of the symbol is obtained using the amplitude phase reference of the carrier at the band end. Extrapolate,
When the carrier at the band edge of the symbol is SP or CP, the SP is extrapolated outside the band of the symbol using the value of SP or CP, and the SP extrapolated outside the band is also used. The frequency characteristics of the symbols are estimated , the synthesis coefficient is calculated from the frequency characteristics of each branch output from the switching means of each branch, and diversity combining is performed to demodulate the OFDM signal .

  According to the present invention, the state of the received signal is grasped from the moving speed of the moving body and the fluctuation cycle of the received signal level, and the above-described time interpolation + frequency interpolation method and frequency interpolation method for each symbol are selectively performed. Since switching is performed, in a reception environment where transmission path characteristics are constantly changing, such as a mobile reception environment, it is possible to perform more accurate frequency characteristic equalization according to the moving speed of the moving body, and to improve reception characteristics. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration example of a receiving apparatus according to an embodiment of the present invention. The configuration and operation of the receiving apparatus of this embodiment will be described with reference to this figure.

  100 is a receiving antenna that receives an RF frequency signal, 102 is a tuner that tunes to an RF frequency signal and converts it to an intermediate frequency band signal, 104 is an A / D converter that converts an analog signal to a digital signal, 106 Is a quadrature demodulating unit, which can obtain a complex baseband signal of digital I- and Q-axis signals. Reference numeral 108 denotes a complex FFT unit that obtains a frequency-axis signal by performing discrete Fourier transform on a complex baseband signal (time waveform), and obtains complex data of several thousand carriers. Reference numeral 110 denotes a frequency characteristic estimator that estimates frequency characteristics generated in the transmission path, and has two types of equalization methods: a time interpolation + frequency interpolation method and a frequency interpolation method for each symbol. Reference numeral 112 denotes an amplitude variation of a specific carrier such as CP (Continual Pilot), AC (Auxiliary Channel), and TMCC (Transmission and Multiplexing Configuration Control), and two types of processing methods in the frequency characteristic estimation unit 110 according to the variation speed. It is an amplitude fluctuation | variation detection part which performs control which switches by the switch 114. FIG. The frequency characteristic equalization unit 116 performs frequency equalization by performing complex division on the carrier data using the frequency characteristic of the transmission path obtained in this way. Reference numeral 118 denotes a demodulating unit that demodulates the signal obtained by the frequency characteristic equalizing unit 116. For example, digital signals 0 and 1 are output from a constellation of 64QAM.

  As described above, the receiving apparatus according to the present embodiment includes the frequency characteristic estimating unit 110, the frequency characteristic estimating unit 1 using the time interpolation + frequency interpolation method, and the frequency characteristic estimating unit 2 using the frequency interpolation method for each symbol. Prepare. The SP output from the complex FFT unit 108 is input to each of the frequency characteristic estimation units 1 and 2. The frequency characteristic estimator 1 calculates the channel characteristics of carriers other than the SP carrier by performing the interpolation process in the frequency direction after performing the interpolation process in the time axis direction using the SPs of the three symbols before and after, and the switch To 114. The frequency characteristic estimator 2 calculates the transmission line characteristics of carriers other than the SP carrier and outputs them to the switch 114 only by interpolation in the frequency direction for each symbol. The switch 114 switches between the output of the frequency characteristic estimator 1 and the output of the frequency characteristic estimator 2 under the control of the amplitude fluctuation detector 112 and outputs the result to the frequency characteristic equalizer 116.

The frequency characteristic estimation unit 2 will be described in more detail. The arrangement of SPs and CPs for terrestrial digital broadcasting is shown in FIG. In terrestrial digital broadcasting, when the transmission mode is 3, digital signals are transmitted using 5617 (k = 0 to 5616) carriers. Assuming that the carrier position of the SP inserted for estimating the transmission path characteristics is kp, the arrangement is as follows.
kp = 3 × mod (i, 4) + 12p
Here, i is a symbol number, p is 0 to 467 (when the transmission mode is 3), and mod (i, 4) indicates a remainder when i is divided by 4. However, the maximum carrier number in mode 3 is 5616, and a CP is always assigned to this carrier (see ● on the right end of FIG. 6).

  The frequency characteristic estimation unit 2 performs an interpolation process in the frequency direction from the SP and CP for each symbol in order to estimate the transmission path characteristic in the frequency direction. At this time, an OFDM signal band edge (a plurality of k = 0 or more) The transmission characteristics of the carrier and a plurality of carriers of k = 5616 or less) are disturbed. This is because there are no pilot symbols such as SP and CP for estimating transmission path characteristics outside the OFDM signal band.

  Therefore, in order to reduce the disturbance of the transmission characteristics at the end of the OFDM signal band, the frequency characteristic estimation unit 2 interpolates or extrapolates using SP or CP as shown in FIG. The channel characteristics of all carriers are estimated using the amplitude phase values obtained by interpolation or extrapolation.

  The transmission path estimation in FIG. 7 will be described in detail. The carrier of k = 5616 at the right end of the band (the band end on the higher frequency side) is a CP, and this CP value is extrapolated as it is outside the band on the right side of the band. On the other hand, the carrier with k = 0 at the left end of the band (the band end on the lower frequency side) may be an SP or a data carrier. In the case of SP, the amplitude phase value is extrapolated outside the band on the left side of the band using the value. In the case of the data carrier, the SP value of k = 0 of the preceding and following symbols is used as the amplitude phase reference of k = 0 of the current symbol (i). Outside the band on the left side of the band, the value of the amplitude phase reference of k = 0 is extrapolated as it is. Hereinafter, the amplitude phase value extrapolated outside the band will be referred to as SP for convenience.

  The carrier number of the amplitude phase reference extrapolated outside the OFDM signal band (outside the left side and right side) is a carrier number that is continuous with the SP for every 12 carriers in the band. That is, as shown in FIG. 7, when mod (i, 4) = 0, the SP carrier numbers extrapolated to the lower frequency side are k = -12, k = -24,. The carrier numbers of the SP extrapolated to the higher side are k = 5616 + 12 = 5628, k = 5616 + 24 = 5640,. When mod (i, 4) = 1, the carrier number of the SP extrapolated to the low frequency side is k = -9, k = -21,... and extrapolated to the high frequency side. It is assumed that the carrier number of the SP is k = 5616 + 3 = 5619, k = 5616 + 15 = 5631,. The same applies to mod (i, 4) = 2 and mod (i, 4) = 3.

  More specifically, regarding the amplitude phase reference at the left end of the band, when mod (i, 4) = 0, the SP value of k = 0 (left end of the band) is used as it is, and mod (i, 4) = 1. In this case, the SP value of k = 0 of the previous symbol (i−1) is used as the amplitude phase reference of k = 0 of the current symbol (i). Note that the amplitude phase reference may be obtained by linear interpolation from the two values of the SP value of k = 0 one symbol before (i−1) and the SP value of k = 0 three symbols later (i + 3). . Further, the SP value of k = 3 of the current symbol (i), that is, the SP value closest to the left end of the band may be used as it is. Similarly, in the case of mod (i, 4) = 2 and 3, the SP of k = 0 before 2 symbols and 3 symbols is used, the SP of k = 0 after 2 symbols and 1 symbol is used, and before and after It is also possible to use a straight line interpolation from the symbols or use the SP value of k = 6 or k = 9 of the current symbol (i) as it is. The SP is extrapolated to the left side of the band using the amplitude phase reference of the carrier at the left end of the band thus obtained.

  The above example is the case of mode 3, but in the case of mode 2, the total number of carriers is 2809 and k = 2808 is CP. The same is true if k = 2808 instead of k = 5616.

  As can be seen from the above description, the frequency characteristic estimation unit 2 of the present embodiment estimates the frequency characteristic in units of one symbol as follows. If the carrier at the band edge of the symbol is not SP or CP, the SP at the band edge of the preceding or following symbol is interpolated from the SP at the band edge of the preceding or following symbol, or the SP or CP having the closest frequency in the symbol Is used to obtain the amplitude phase reference of the carrier at the band edge of the symbol, and extrapolate the SP outside the band of the symbol using the amplitude phase reference of the carrier at the band edge. When the carrier of the symbol is SP or CP, the SP is extrapolated outside the band of the symbol using the SP or CP value. Thus, the frequency characteristic of the symbol is estimated using the SP extrapolated outside the band. That is, the frequency characteristic estimation unit 2 estimates the frequency characteristic in units of one symbol by using the extrapolated SP outside the band and the SP and CP within the band. Further, when the amplitude phase reference of the carrier at the band end of the symbol is obtained from another SP or CP, the frequency characteristic may be estimated in units of one symbol using the amplitude phase reference of the carrier at the band end.

  In addition, although the frequency characteristic estimation part 2 of this Embodiment was demonstrated above, generally the frequency characteristic estimation part 2 should just estimate a frequency characteristic per symbol.

  The amplitude fluctuation detection unit 112 will be described in more detail. The amplitude fluctuation detection unit 112 calculates the speed of amplitude fluctuation on the receiving side using a carrier that is always transmitted with a constant amplitude, such as CP, TMCC, and AC of terrestrial digital broadcasting, and the frequency characteristic estimation unit 110 This is a circuit that performs control to switch two frequency characteristic estimation circuits with a switch 114. One CP is arranged on the highest frequency carrier of the OFDM signal. When the fluctuation speed of the amplitude is equal to or higher than a preset value, control is performed to switch the circuit of the frequency characteristic estimation unit 110 to the frequency interpolation method for each symbol. When the amplitude fluctuation speed is equal to or lower than the set value, time interpolation + Switch to frequency interpolation.

  That is, the amplitude fluctuation detection unit 112 can increase the resolution in the frequency direction by controlling the switch 114 according to the speed of amplitude fluctuation on the receiving side, and the frequency characteristics can be obtained even when a longer delayed wave exists. One of the output of the frequency characteristic estimator 1 that can be estimated and the output of the frequency characteristic estimator 2 that is superior to time changes such as a high-speed mobile reception environment is selected, and the frequency characteristic equalizer 116 It is the structure to output. As a result, even in a reception environment where the transmission path characteristics are constantly changing, such as a mobile reception environment, more accurate frequency characteristics equalization is performed according to the speed of amplitude fluctuation on the receiving side accompanying the moving speed of the moving body. Therefore, it is possible to improve the reception characteristics of the reception device.

  As described above, in the receiving apparatus according to the present embodiment, the amplitude variation detection unit 112 detects the frequency characteristic of the amplitude variation using the carrier such as CP, TMCC, and AC obtained by the complex FFT unit 108. Originally, carriers such as CP, TMCC, AC, etc. are transmitted only with a constant amplitude, so there is no frequency characteristic and only a DC component. However, due to fading interference due to mobile reception, a time variation is added to the waveform after FFT. A spread in the frequency direction appears. Therefore, it is possible to detect the amplitude fluctuation speed by detecting this range of spread. Here, instead of using only one carrier such as CP, TMCC, AC, etc., it is possible to increase the reliability by referring to detection results from a plurality of carriers.

  The amplitude fluctuation detection unit 112 may detect the fluctuation speed by counting the number of valleys of the amplitude of CP (or TMCC, AC) within a certain time. That is, generally, when a terrestrial wave is received and received, fading interference occurs, and as a result, time fluctuation occurs in the amplitude of the received signal. Originally, carriers such as CP, TMCC, and AC are transmitted at a constant amplitude, but periodic amplitude fluctuations appear in the received carrier due to the influence of fading interference. Therefore, it is possible to detect the amplitude fluctuation speed by counting the number of the amplitudes that become the minimum (the number of valleys of the amplitude).

  In addition, the amplitude fluctuation detection unit 112 may improve detection accuracy by using a plurality of CP (or TMCC, AC) carriers.

  Further, instead of switching the two frequency characteristic estimation circuits in the amplitude fluctuation detection unit 112 and the switch 114, correction in the time direction is performed using SPs of three symbols before and after to calculate transmission path characteristics for every three carriers, and the frequency direction When performing interpolation, a method of performing interpolation in the frequency direction using transmission path characteristics for every three carriers and an inner frequency direction using only transmission path characteristics for every 12 carriers obtained from the SP of the symbol. The method of inserting may be switched.

  2 includes a reception antenna 200, a tuner unit 202, an A / D conversion unit 204, an orthogonal demodulation unit 206, a complex FFT unit 208, two frequency characteristic estimation units 210, and an amplitude variation estimation unit 212. , A moving speed detection unit 214, a switch 216, a frequency characteristic equalization unit 218, and a demodulation unit 220. In the receiving apparatus according to the embodiment of FIG. 2, the configuration other than the amplitude fluctuation estimating unit 212 and the moving speed detecting unit 214 performs the same processing as that of the receiving apparatus of FIG.

  The receiving apparatus of the embodiment of FIG. 2 detects the moving speed of the moving body by the moving speed detecting unit 214 using GPS data, a car speedometer or the like instead of the amplitude fluctuation detecting unit 112, and estimates the amplitude fluctuation period. In this configuration, switching of the switch 216 is controlled using the fluctuation estimation unit 212. That is, the amplitude fluctuation is proportional to the speed of the moving body and the signal transmission frequency, and the faster the moving body, the faster the fluctuation period. If the velocity of the moving body is v and the wavelength of the signal is λ, the amplitude fluctuation speed (frequency) fd can be calculated by fd = v / λ. Therefore, it is possible to estimate the amplitude fluctuation period from the moving speed of the moving body.

  1 and 2, frequency characteristic estimation units 110 and 210 having two different frequency characteristic estimation units 1 and 2, an amplitude variation detection unit 112, an amplitude variation estimation unit 212, and switches 114 and 216. Except for, the configuration is the same as that of a conventional OFDM receiver.

  FIG. 3 is a configuration example of a digital reception apparatus using the diversity reception method according to the embodiment of the present invention. A technique for performing compensation and synthesis of transmission path characteristics collectively using a frequency domain received signal obtained from a complex FFT unit arranged for each branch and a synthesis coefficient calculated from this received signal is, for example, This is described in Japanese Patent No. 3377361 “Diversity Receiver”.

  3 includes a reception antenna 300, a tuner unit 302, an A / D conversion unit 304, an orthogonal demodulation unit 306, a complex FFT unit 308, two frequency characteristic estimation units 310, an amplitude variation detection unit 312, and A switch 314 is provided for each branch of the L system, and a carrier coefficient and a composite coefficient calculation from the synthesis coefficient calculation unit 316 and the complex FFT unit 308 to which a signal from each switch 314 for each branch of the L system is input. A diversity combining unit 318 to which a signal from the unit 316 is input, and a demodulation unit 320 to which a signal from the diversity combining unit 318 is input.

The receiving apparatus of the embodiment of FIG. 3 configured as described above has L antenna inputs, and the processing of the frequency characteristic estimation unit 310 is switched from the receiving antenna 300 by the switch 314 independently for each branch. The same processing as that of a normal receiving apparatus is performed. Reference numeral 316 denotes a synthesis coefficient calculation unit that calculates a synthesis coefficient at the time of diversity synthesis from the frequency characteristics of the received signal of each branch. For the frequency characteristics H _l (k) of the L system, for each carrier for diversity synthesis of the L system. Assuming that the synthesis coefficient is W _l (k), it is calculated by any one of the following formulas (1) to (3), and is output to the diversity combining unit 318. In the following formulas (1) to (3), l is an antenna branch number, k is a carrier number, and H _{l *} (k) is a complex conjugate of the frequency characteristic H _l (k).

式（１）の分母合成係数Σ｜Ｈ_ｌ（ｋ）｜^２は規格化係数である。

The denominator synthesis coefficient Σ | H _l (k) | ² in equation (1) is a normalization coefficient.

式（２）の分母｜Ｈ_ｌ（ｋ）｜Σ｜Ｈ_ｌ（ｋ）｜は規格化係数である。

The denominator | H _l (k) | Σ | H _l (k) | in the equation (2) is a normalization coefficient.

式（３）の分母｜Ｈ_ｌ（ｋ）｜^２は規格化係数である。

The denominator | H _l (k) | ^{2 in} equation (3) is a normalization factor.

The diversity combining unit 318 combines the complex data Y _l (i, k) of the carrier of each branch output from the complex FFT unit 308 and the combined coefficient W _l (i, k) obtained from the combined coefficient calculating unit 316. The output Z (i, k) is obtained by the calculation of the following equation (4) and output to the demodulator 320. In Expression (4), i is a symbol number, and the combined output Z (i, k) is a signal specified by the symbol number i and the carrier number k. The complex data Y _l (i, k) and the combined coefficient W _l (i, k) is a signal specified by the antenna branch number l, symbol number i, and carrier number k.

３２０はダイバシティ合成部３１８で得られた信号を復調する復調部であり、例えば６４ＱＡＭのコンスタレーションから０，１のデジタル信号が出力される。

Reference numeral 320 denotes a demodulator that demodulates the signal obtained by the diversity combiner 318. For example, 0 and 1 digital signals are output from a constellation of 64QAM.

As described above, in the diversity receiver of FIG. 3, the complex data Y _l (i, k) of the carrier that is the received signal on the frequency axis obtained from the complex FFT unit 308 arranged for each branch, and the composite coefficient calculation Using the synthesis coefficient W _l (i, k) obtained from the unit 316, the diversity synthesis unit 318 performs compensation and synthesis collectively. Next, when demodulating section 320 demodulates the signal obtained from diversity combining section 318, in addition to the effect of the receiving apparatus of FIG. 1, an OFDM RF signal is received in a multipath or fading environment. In addition, stable reception is possible.

  In the diversity receiver of FIG. 3, the amplitude fluctuation detection unit 312 may use only the branch 1, and the branches 2 to L may control the switch 314 using the amplitude fluctuation detection unit of the branch 1.

  3, the amplitude fluctuation detection unit 312 for each branch is configured by the movement speed detection unit 214 and the amplitude fluctuation estimation unit 212 illustrated in FIG. 2, and the movement detected by the movement speed detection unit 214. The amplitude variation estimation unit 212 may switch the output of the switch 216 based on the moving speed of the body.

  The invention made by the present inventor has been specifically described based on the embodiment of the invention, but the invention is not limited to the embodiment of the invention and does not depart from the gist of the invention. Of course, various changes can be made.

It is a figure which shows the structural example of the receiver by embodiment of this invention. It is a figure which shows the structural example of the receiver which used the amplitude fluctuation | variation estimation part by GPS data etc. instead of the amplitude fluctuation | variation estimation part in the receiver of embodiment shown in FIG. It is a figure which shows the structural example of the digital receiver using the space diversity receiving system by embodiment of this invention. It is a figure which shows the pilot signal of terrestrial digital broadcasting. It is a figure which shows the interpolation process system of a transmission line characteristic. It is a figure which shows arrangement | positioning of SP and CP of terrestrial digital broadcasting (mode 3). It is a figure for demonstrating the insertion and extrapolation of a band edge and a band outside in 1 symbol transmission path estimation.

Explanation of symbols

100, 200, 300 ... receiving antennas 102, 202, 302 ... tuners 104, 204, 304 ... A / D converters 106, 206, 306 ... quadrature demodulation units 108, 208, 308 ... complex FFT units 110, 210, 310 ... frequency characteristic estimation unit 112, 312 ... amplitude fluctuation detection unit 114, 216, 314 ... switch 116, 218 ... frequency characteristic equalization unit 118, 220, 320 ... demodulation unit 212 ... amplitude fluctuation estimation unit 214 ... movement speed detection unit 316 ... Synthesis coefficient calculation unit 318 ... Diversity synthesis unit

Claims (6)

In a receiving apparatus that receives a transmission signal of a digital transmission scheme in which an SP (Scattered Pilot) is inserted using an OFDM modulation scheme,
Frequency characteristic estimation means having a first frequency characteristic estimation unit that estimates frequency characteristics using SPs of three symbols before and after, and a second frequency characteristic estimation unit that estimates frequency characteristics in units of one symbol;
Amplitude fluctuation detecting means for detecting the amplitude fluctuation of the carrier transmitted at a constant amplitude every symbol;
Switching means for switching the frequency characteristics obtained from the first frequency characteristic estimation unit or the second frequency characteristic estimation unit according to the fluctuation speed obtained by the amplitude fluctuation detection unit,
The amplitude fluctuation detecting means detects amplitude fluctuation using at least one carrier of CP, TMCC, and AC, which is a carrier transmitted every symbol with the constant amplitude,
A receiving apparatus, wherein the switching means demodulates an OFDM signal by switching frequency characteristics. In a diversity reception system receiving apparatus that receives a transmission signal of a digital transmission system in which an SP is inserted using an OFDM modulation system,
For each branch,
Frequency characteristic estimation means having a first frequency characteristic estimation unit that estimates frequency characteristics using SPs of three symbols before and after, and a second frequency characteristic estimation unit that estimates frequency characteristics in units of one symbol;
Amplitude fluctuation detecting means for detecting the amplitude fluctuation of the carrier transmitted at a constant amplitude every symbol;
Switching means for switching the frequency characteristics obtained from the first frequency characteristic estimation unit or the second frequency characteristic estimation unit according to the fluctuation speed obtained by the amplitude fluctuation detection unit,
The amplitude fluctuation detecting means detects amplitude fluctuation using at least one carrier of CP, TMCC, and AC, which is a carrier transmitted every symbol with the constant amplitude,
A receiving apparatus, wherein a combining coefficient is calculated from frequency characteristics of each branch output from the switching means of each branch, and diversity combining is performed to demodulate an OFDM signal. In a receiving apparatus that receives a transmission signal of a digital transmission scheme in which an SP (Scattered Pilot) is inserted using an OFDM modulation scheme,
Frequency characteristic estimation means having a first frequency characteristic estimation unit that estimates frequency characteristics using SPs of three symbols before and after, and a second frequency characteristic estimation unit that estimates frequency characteristics in units of one symbol;
Amplitude fluctuation detecting means for detecting the amplitude fluctuation of the carrier transmitted at a constant amplitude every symbol;
Switching means for switching the frequency characteristics obtained from the first frequency characteristic estimation section or the second frequency characteristic estimation section in accordance with the fluctuation speed obtained by the amplitude fluctuation detection means;
With
The second frequency characteristic estimator is
If the carrier at the band edge of the symbol is not SP or CP, the SP at the band edge of the preceding or following symbol is interpolated from the SP at the band edge of the preceding or following symbol, or the SP or CP having the closest frequency in the symbol To obtain the amplitude phase reference of the carrier at the band edge of the symbol, and extrapolate the SP outside the band of the symbol using the amplitude phase reference of the carrier at the band edge,
If the carrier at the band edge of the symbol is SP or CP, extrapolate SP outside the band of the symbol using the value of SP or CP,
Using the SP extrapolated outside the band, the frequency characteristic of the symbol is estimated,
A receiving apparatus, wherein the switching means demodulates an OFDM signal by switching frequency characteristics . In a diversity reception system receiving apparatus that receives a transmission signal of a digital transmission system in which an SP is inserted using an OFDM modulation system,
For each branch,
Frequency characteristic estimation means having a first frequency characteristic estimation unit that estimates frequency characteristics using SPs of three symbols before and after, and a second frequency characteristic estimation unit that estimates frequency characteristics in units of one symbol;
Amplitude fluctuation detecting means for detecting the amplitude fluctuation of the carrier transmitted at a constant amplitude every symbol ;
Switching means for switching the frequency characteristics obtained from the first frequency characteristic estimation unit or the second frequency characteristic estimation unit according to the fluctuation speed obtained by the amplitude fluctuation detection unit,
The second frequency characteristic estimator is
If the carrier at the band edge of the symbol is not SP or CP, the SP at the band edge of the preceding or following symbol is interpolated from the SP at the band edge of the preceding or following symbol, or the SP or CP having the closest frequency in the symbol To obtain the amplitude phase reference of the carrier at the band edge of the symbol, and extrapolate the SP outside the band of the symbol using the amplitude phase reference of the carrier at the band edge,
If the carrier at the band edge of the symbol is SP or CP, extrapolate SP outside the band of the symbol using the value of SP or CP,
Using the SP extrapolated outside the band, the frequency characteristic of the symbol is estimated,
A receiving apparatus , wherein a combining coefficient is calculated from frequency characteristics of each branch output from the switching means of each branch, and diversity combining is performed to demodulate an OFDM signal. In receiving apparatus that will receive the transmission signal of a digital transmission system SP is inserted with OFDM modulation scheme,
A frequency characteristic estimation means and a second frequency characteristic estimation unit for estimating a frequency characteristic in the first frequency characteristic estimation unit and a symbol unit for estimating the frequency characteristics using the SP before after 3 symbols,
A moving speed detecting means for measuring the speed of the moving body with GPS or taking in the traveling speed measured by the speedometer provided in the moving body;
Amplitude fluctuation estimating means for estimating amplitude fluctuation from the speed of the moving body obtained by the moving speed detecting means;
Switching means for switching the frequency characteristic obtained from the first frequency characteristic estimation unit or the second frequency characteristic estimation unit according to the fluctuation speed obtained by the amplitude fluctuation estimation unit,
The second frequency characteristic estimator is
If the carrier at the band edge of the symbol is not SP or CP, the SP at the band edge of the preceding or following symbol is interpolated from the SP at the band edge of the preceding or following symbol, or the SP or CP having the closest frequency in the symbol To obtain the amplitude phase reference of the carrier at the band edge of the symbol, and extrapolate the SP outside the band of the symbol using the amplitude phase reference of the carrier at the band edge,
If the carrier at the band edge of the symbol is SP or CP, extrapolate SP outside the band of the symbol using the value of SP or CP,
Using the SP extrapolated outside the band, the frequency characteristic of the symbol is estimated,
A receiving apparatus, wherein the switching means demodulates an OFDM signal by switching frequency characteristics . In a diversity reception system receiving apparatus that receives a transmission signal of a digital transmission system in which an SP is inserted using an OFDM modulation system,
For each branch,
Frequency characteristic estimation means having a first frequency characteristic estimation unit that estimates frequency characteristics using SPs of three symbols before and after, and a second frequency characteristic estimation unit that estimates frequency characteristics in units of one symbol;
A moving speed detecting means for measuring the speed of the moving body with GPS or taking in the traveling speed measured by the speedometer provided in the moving body;
Amplitude fluctuation estimating means for estimating amplitude fluctuation from the speed of the moving body obtained by the moving speed detecting means;
Switching means for switching the frequency characteristics obtained from the first frequency characteristic estimation section or the second frequency characteristic estimation section in accordance with the fluctuation speed obtained by the amplitude fluctuation estimation means;
With
The second frequency characteristic estimator is
If the carrier at the band edge of the symbol is not SP or CP, the SP at the band edge of the preceding or following symbol is interpolated from the SP at the band edge of the preceding or following symbol, or the SP or CP having the closest frequency in the symbol To obtain the amplitude phase reference of the carrier at the band edge of the symbol, and extrapolate the SP outside the band of the symbol using the amplitude phase reference of the carrier at the band edge,
If the carrier at the band edge of the symbol is SP or CP, extrapolate SP outside the band of the symbol using the value of SP or CP,
Using the SP extrapolated outside the band, the frequency characteristic of the symbol is estimated ,
A receiving apparatus , wherein a combining coefficient is calculated from frequency characteristics of each branch output from the switching means of each branch, and diversity combining is performed to demodulate an OFDM signal .

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