JP4929481B2 - Diversity receiver - Google Patents

Description

  The present invention relates to a diversity receiver used in an orthogonal frequency division multiplexing (OFDM) wireless communication system.

  In Japanese terrestrial digital television broadcasting, by adopting OFDM as a modulation method, the information transmission speed is increased, and at the same time, it is robust against delayed interference waves such as ghost waves. In OFDM, modulation is performed by assigning data to a plurality of subcarriers orthogonal to each other on the frequency axis. On the transmitting side of the OFDM wireless communication system, inverse fast Fourier transform (IFFT) processing is performed to convert a frequency domain signal into a time domain signal, and on the receiving side, a time domain signal is converted back to a frequency domain signal. Performs a fast Fourier transform (FFT) process.

  In OFDM, an arbitrary modulation scheme can be used for modulation of each subcarrier. For example, transmission by synchronous detection or transmission by delay detection is possible. In synchronous detection, a pilot signal having a known amplitude and phase is inserted at a predetermined position on the frequency axis and time axis on the transmission side. On the receiving side, the pilot signal is extracted, the amplitude and phase are measured, and an error from the known amplitude and phase is obtained. In accordance with this error detection result, equalization of the amplitude and phase of the received signal is performed in units of subcarriers. In the delay detection, the received signal is demodulated by differential decoding between received symbols for the signal differentially encoded on the transmitting side.

  In order to improve the reception quality in OFDM, spatial diversity using multiple antennas is very effective. One type of spatial diversity is combining diversity in which signals received by antennas are combined in phase.

In this regard, Patent Document 1 discloses a method in which a digital filter is provided before the FFT, the delay spread of the received signal is equivalently reduced to increase diversity gain, and the circuit scale is reduced. Yes.
JP 2007-6264 A

  However, the method in Patent Document 1 assumes a delay spread within a preset guard interval period, and does not deal with a delayed wave exceeding the guard interval period (hereinafter referred to as a guard over delayed wave).

  In general, synthesis diversity techniques include MMSE (Minimum Mean Square Error) synthesis that minimizes the mean square error and MRC (Maximum Ratio Combining) synthesis that is maximum ratio synthesis.

  When combining diversity is used, if there is no delayed wave exceeding the guard, MRC combining is advantageous in that the diversity gain and the circuit scale are simple. However, if there is a delayed wave exceeding the guard, the delay is delayed. It is desirable to perform MMSE synthesis that is advantageous in terms of suppressing the influence of interference waves.

  Therefore, in order to suppress the over-guard delay wave, it is conceivable that the receiver has both functions and switches based on the presence / absence of the over-guard delay wave. There is a problem of becoming.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a diversity receiver that effectively suppresses over-guard delay waves and has a small circuit scale.

A diversity receiver according to the present invention includes a plurality of antennas that receive an orthogonal frequency division multiplex signal and output a received signal, and a delayed wave of the received signal according to the presence or absence of a delayed wave that exceeds the guard interval period with respect to the received signal. Are provided corresponding to a plurality of antennas, a plurality of FFTs for performing Fourier transform on the output signal of the delay wave suppression circuit, and a plurality of FFTs, respectively. A plurality of propagation path estimation means for outputting propagation path estimation information based on output signals from a plurality of FFTs, and a plurality of FFT output signals that have passed through the plurality of propagation path estimation means, Combining means for performing. The delay wave suppression means includes weight coefficient calculation means for calculating a weight coefficient for received signals from a plurality of antennas based on propagation path estimation information from the plurality of propagation path estimation means, and a weight coefficient calculated by a weight coefficient calculation section. And combining means for combining received signals from a plurality of antennas in order to suppress a delayed wave of the received signal.

Preferably, the delay wave suppressing means determines the presence / absence of a delayed wave exceeding the guard interval period for the received signal based on the propagation path estimation information of the plurality of propagation path estimating means, and the number of delayed waves to be suppressed (K) And a selection means for selecting a plurality (N) of different combinations composed of at least (K + 1) antennas out of the plurality (N) antennas in order to suppress K delayed waves. And further including. The weighting factor calculation unit is provided corresponding to each of a plurality (N) of antennas, and each of the channel estimation information from the channel estimation means respectively corresponding to the received signals of at least (K + 1) antennas selected. A plurality of weighting calculation units for calculating weighting coefficients for received signals from at least (K + 1) antennas. The combining means is provided corresponding to each of the plurality of weighting calculation units, and each of the combining means combines a reception signal from at least (K + 1) antennas based on the weighting coefficient calculated by the corresponding weighting calculation unit. Of synthesis units.

  In particular, the selection means has a large combined signal of received signals received by at least (K + 1) antennas from among different combinations composed of at least (K + 1) antennas among a plurality of (N) antennas. A plurality of (N) combinations are selected.

Preferably, based on the channel estimation information of the plurality of channel estimation means, further Ru comprising a determining unit whether a delayed wave exceeding the guard interval period of the received signal. The delayed wave suppression unit is activated based on the determination result of the determination unit.

Another diversity receiver according to the present invention includes a plurality of antennas that receive orthogonal frequency division multiplexed signals and output reception signals, and are provided corresponding to the plurality of antennas, respectively, with respect to the reception signals of the corresponding antennas A plurality of FFTs that perform Fourier transform, a plurality of propagation path estimation units that are respectively provided corresponding to the plurality of FFTs and that output propagation path estimation information based on output signals from the plurality of FFTs, and a plurality of FFTs A delay wave suppression means for suppressing a delay wave in accordance with the presence or absence of a delay wave exceeding the guard interval period, and a combination for demodulating the output signal that has passed through the delay wave suppression means Means. The delay wave suppressing means includes weight coefficient calculating means for calculating weight coefficients for output signals from the plurality of FFTs based on propagation path estimation information from the plurality of propagation path estimating means, and weights calculated by the weight coefficient calculating section. Combining means for combining output signals from the plurality of FFTs to suppress the delayed wave based on the coefficient.

Preferably, each of output signals from the plurality of FFTs corresponds to an output signal group corresponding to the number of subcarriers. Delay wave suppressing means, based on the channel estimation information of the plurality of channel estimation means, thereby determining the presence or absence of a delayed wave exceeding the guard interval period against the output signals from the plurality of FFT, the delay wave suppressing A determination unit for determining the number (K), and a plurality of different combinations of at least (K + 1) output signal groups from among the plurality of output signal groups in order to suppress K delayed waves; Selecting means. The weighting factor calculation unit is provided corresponding to each of a plurality (N) of propagation path estimation means, each of which is a propagation path from the propagation path estimation means corresponding to at least (K + 1) selected output signal groups. A plurality of weighting calculation units for calculating weighting coefficients for at least (K + 1) output signal groups based on the estimation information are included. The combining means is provided corresponding to each of the plurality of weight calculation units, and each of the plurality of combinations combines at least (K + 1) output signal groups based on the weight coefficients calculated by the corresponding weight calculation units. Includes units.

  In particular, the selection means has a large combined signal of at least (K + 1) output signal groups from among different combinations composed of at least (K + 1) output signal groups among a plurality (N) of output signal groups. A plurality (N) of combinations are selected.

Preferably, the information processing apparatus further includes a determination unit that determines presence / absence of a delayed wave exceeding a guard interval period for output signals from the plurality of FFTs based on propagation path estimation information of the plurality of propagation path estimation units. The delayed wave suppression unit is activated based on the determination result of the determination unit.

  A diversity receiver according to the present invention includes a plurality of antennas that receive orthogonal frequency division multiplexed signals and output the received signals, and delay wave suppression means that performs filtering processing on the received signals according to the presence or absence of delay spread. . The delay wave suppression means includes weight coefficient calculation means for calculating a weight coefficient for received signals from a plurality of antennas based on propagation path estimation information from the plurality of propagation path estimation means, and a weight coefficient calculated by a weight coefficient calculation section. And combining means for combining received signals from a plurality of antennas in order to suppress a delayed wave of the received signal.

  By providing the configuration, that is, the delay wave suppression means, a weighting factor is calculated based on the propagation path estimation information, and the received signal is synthesized to suppress the delay wave. In other words, since the over-guard delay wave is suppressed and the received signal in which the over-guard delay wave is suppressed is input to the subsequent combining means, it is possible to use MRC combining and reduce the circuit scale of the diversity receiver. It becomes possible. In addition, as a diversity receiver, by adding delay wave suppression means as an add-on to MRC synthesis that has been used in the past, it is possible to suppress over-guard delay waves, which eliminates the need for complicated design changes and the like. This is also advantageous.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

(Embodiment 1)
FIG. 1 is a schematic functional block diagram of a diversity receiver 1 according to the first embodiment of the present invention.

  Referring to FIG. 1, diversity receiver 1 according to the first embodiment of the present invention shows a case where antennas 5-1 to 5-N are provided. Antennas 5-1 to 5-N are connected to guard excess delay wave suppressor 50 according to the first embodiment of the present invention. The over-guard delay wave suppressor 50 outputs a signal that has been subjected to filter processing to suppress the over-guard delay wave that is the delay spread of the received signal received from the antennas 5-1 to 5-N.

  And it outputs to FFT10-1-10-N provided corresponding to each of the antennas 5-1 to 5-N.

  Then, output signals from the FFTs 10-1 to 10-N that return the time domain signal to the frequency domain signal are output to the propagation path estimation unit.

  Corresponding to the FFTs 10-1 to 10-N, respectively, propagation path estimation units 15-1 to 15-N (hereinafter collectively referred to as propagation path estimation unit 15) and equalizers 20-1 to 20-N ( Hereinafter, they are also collectively referred to as an equalizer 20).

  The propagation path estimation unit 15 estimates the propagation path of the received signal based on the output signal output from the FFT, and the equalizer 20 uses the propagation path estimation value for the output signal output from the FFT. The equalization process is executed.

  The signals output from the equalizers 20-1 to 20-N are combined by a maximum ratio combining circuit (Maximum Ratio Combining: MRC) and output.

  Note that the guard excess delay wave suppressor 50 according to 1 according to the present embodiment receives input of propagation path estimation information from the propagation path estimation unit 15.

  FIG. 2 is a functional block diagram of the over-guard delay wave suppressor 50 according to the first embodiment of the present invention.

  Referring to FIG. 2, the over-guard delay wave suppressor 50 according to the first embodiment of the present invention includes a weight coefficient calculator 55 and a combiner 60.

  The weight coefficient calculator 55 operates based on an input of a control signal Aon / Aoff for activating / deactivating the delay wave suppressor 50. It is assumed that the control signal Aon / Aff is output from a determination circuit (not shown) based on the presence / absence of a delayed wave exceeding the guard.

  Specifically, it is determined whether there is a delayed wave exceeding the guard period based on the propagation path estimation information h output from the propagation path estimation unit 15, and the control signal Aon / Aoff is determined based on the determination result. It is possible to provide a determination circuit for outputting.

  Specifically, the delay wave suppressor 50 is activated based on the input of the control signal Aon, and the weight coefficient calculator 55 calculates the weight coefficient w based on the propagation path estimation information h. Then, the calculated weighting coefficient w is output to the synthesizer 60.

  The synthesizer 60 receives the weighting factor w calculated by the weighting factor calculator 55, multiplies the received signal r received from the antenna by the calculated weighting factor w, and suppresses the delay wave exceeding the guard. r # is output.

  On the other hand, the delay wave suppressor 50 is deactivated based on the input of the control signal Aoff, and the weight coefficient calculator 55 outputs a predetermined weight coefficient w determined in advance as a default to the synthesizer 60.

  When the delay wave suppressor 50 is deactivated, a weight coefficient w that passes through the received signal input to the combiner 60 without being combined is input to the combiner 60.

  Here, as an example, a case where N received signals r are input from N antennas 5-1 to 5-N to the over-guard delay wave suppressor 50 is shown. Also, N pieces of propagation path estimation information h provided corresponding to the N antennas are input. Then, the weight coefficient calculator 55 outputs N sets of different weight coefficient groups (weight coefficient vectors) composed of the N weight coefficients w to the synthesizer 60 based on the N propagation path estimation information h. Is done. Then, in the synthesizer 60, the N received signals r are multiplied and synthesized by N weighting factors w included in each set of weighting factor groups (weighting factor vectors), and the received signal r # is output. The case to be shown is shown. As a result of multiplication with each set of weight coefficient groups, N received signals r # are output. Therefore, the N received signals r # that have passed through the over-guard delay wave suppressor 50 can be regarded as signals received by the respective antennas 5-1 to 5-N in a pseudo manner.

FIG. 3 is a diagram for explaining a delayed wave suppression method according to the first embodiment of the present invention.
Referring to FIG. 3, the delayed wave suppression method according to the first embodiment of the present invention is a weighting factor w suitable for a received signal between antennas with respect to a delayed wave exceeding the guard of the received signal received by each antenna. In this method, only the delayed wave exceeding the guard is suppressed by combining.

  As shown here, assuming that there are K guard over delayed wave vectors v, the guard over delayed wave vectors of each antenna are expressed by the following equations.

  And the guard over delay wave matrix V based on the guard over delay wave vector of each antenna is expressed by the following equation.

Note that here, a guard-crossing delay wave matrix up to N antennas is shown.
In this example, the weight vector that suppresses the over-guard delay wave is calculated by multiplying the over-guard delay wave matrix V by the weight vector W.

  That is, a weight vector that satisfies the following equation is calculated.

  The weight vector W is composed of N weighting factors. Then, N weight vectors W are calculated. In this example, N weight vectors are represented as Wa1, Wa2,. A weight matrix X composed of the weight vectors Wa1, Wa2,... WaN is expressed by the following equation.

  Each of the weight vectors wa1, wa2,..., WaN calculated by the weight coefficient calculator 55 is output to the synthesizer 60, and the synthesizer 60 synthesizes N received signals to guard according to each weight vector. The over-delay wave is suppressed, and the received signal r # in which the over-guard delay wave is suppressed is output.

  FIG. 4 is a diagram for explaining the configuration of the over-guard delay wave suppressor 50 when the number of over-guard delay waves K = 1 when two antennas are used.

  Referring to FIG. 4, antennas # 1 and # 2 are provided here, corresponding to antennas # 1 and # 2, respectively, FFTs 10-1 and 10-2, propagation path estimation units 15-1, A case where 15-2 and equalizers 20-1 and 20-2 are provided is shown.

  Then, the propagation path estimators 15-1 and 15-2 output the propagation path estimation information h1 and h2, which are propagation path estimation results, to the over-guard delay wave suppressor 50.

  The over-guard delay wave suppressor 50 includes a weight coefficient calculator 55 that receives the input of propagation path estimation information from the propagation path estimation units 15-1 and 15-2, and a weight coefficient calculator for received signals from each antenna. And a synthesizer 60 that synthesizes by multiplying the weighting coefficient from 55.

Here, the weight coefficient calculator 55 of the over-guard delay wave suppressor 50 uses two sets of weight coefficients (w ₁ ¹ , w) based on the propagation path estimation information from the propagation path estimators 15-1 and 15-2. ₂ ¹ ) and (w ₁ ² , w ₂ ² ) are calculated. The subscript number indicates a weighting factor to be multiplied corresponding to the antenna number. The superscript number indicates a set of weighting coefficient groups (weight vectors) used in the case of being synthesized and output as an output signal r # in a pseudo manner corresponding to the antenna number.

The weighting coefficient is calculated by calculating the weight vector W for suppressing the guard over delayed wave with K = 1 in accordance with the above-described method. Specifically, two sets of weighting coefficients (w ₁ ¹ , w ₂ ¹ ) that become 0 by multiplying the delayed wave vector (v ₁ , v ₂ ) of the antennas # 1 and # 2 by the weight vector W are multiplied. ), (W ₁ ² , w ₂ ² ).

  With this method, the output signal r # in which the over-guard delay wave is suppressed is output from the over-guard delay wave suppressor 50 to the FFT, and is combined and output using a maximum ratio combining circuit (MRC) at the subsequent stage.

  Therefore, by providing the over-guard delay wave suppressor 50, it is possible to realize combining diversity using only MRC without providing MMSE, and it is possible to reduce the circuit scale. In addition, as a diversity receiver, by adding delay wave suppression means as an add-on to MRC synthesis that has been used in the past, it is possible to suppress over-guard delay waves, which eliminates the need for complicated design changes and the like. This is also advantageous.

  Note that it is possible to provide a determination circuit that determines whether there is a delayed wave exceeding the guard period based on the propagation path estimation information h and outputs the control signal Aon / Aoff based on the determination result. As explained above, in the case of this configuration, when using propagation path estimation information based on a signal that suppresses the over-guard delay wave, it is determined that the over-guard delay wave does not exist after the over-guard delay wave is suppressed. There is a possibility that Therefore, for example, once it is determined that there is a delayed wave, it is possible to set so that the determination state is maintained until the device is stopped. Alternatively, it is possible to adopt a method of resetting and determining again after maintaining the determination state for a certain period. It is also possible to provide a determination circuit that outputs the control signal Aon / Aoff based on propagation path estimation information based on a signal that does not suppress the over-guard delay wave.

  As another method, the weighting coefficient calculator 55 can be provided in advance with a matrix (delayed wave suppression matrix) for suppressing the guard over delayed wave composed of N × N. For example, the matrix is appropriately set in advance so that an appropriate weight vector that suppresses the over-guard delay wave is calculated according to the input of the propagation path estimation information h based on profiling of the over-guard delay wave and the like. It is assumed that it is set.

  Therefore, it is possible to suppress the over-guard delay wave by using the delay wave suppression matrix (N × N).

  In the configuration of FIG. 2, N−1 ≧ K is established when the number K of guard-delayed delayed waves is compared with received signals from N antennas. The same applies to the following.

(Modification 1 of Embodiment 1)
In the first embodiment described above, N weighting factors (weights) for suppressing the guard over delay waves by combining the received signals received by the N antennas with the K guard over delay waves, respectively. A method for calculating (vector) has been described.

  In the modification of the first embodiment of the present invention, a method of suppressing the guard over delay wave by combining the received signals received by K + 1 antennas with respect to K guard over delay waves will be described.

  FIG. 5 is a diagram illustrating a configuration of the over-guard delay wave suppressor 50a according to the first modification of the first embodiment of the present invention.

  Referring to FIG. 5, here, antenna combination selector 70 activated in response to control signal Aon / Aoff, and N weighting factor calculation units 56- activated in response to control signal Aon / Aoff. 1-56-N (hereinafter collectively referred to as weight coefficient calculation unit 56) and N synthesis units 62-1 to 62-N (collectively also referred to as synthesis unit 62).

  Here, the antenna combination selector 70 is activated in response to the control signal Aon, receives the input of the suppression delay wave number K, and suppresses the K + 1 delay signals for the received signal r from the antenna to suppress the over-guard delay wave. N different groups of received signals composed of received signals r are selected. The suppression delay wave number K is fixedly input from the outside.

  The antenna combination selector 70 is deactivated according to the control signal Aoff, and outputs it to the N combining units 62-1 to 62-N corresponding to the received signal r from the antenna.

  Each weight coefficient calculation unit 56 is activated according to the control signal Aon, and propagation path estimation information h from a propagation path estimation unit provided corresponding to each of the antennas that receives the input of the selected K + 1 received signals. The weighting factor w is calculated based on Specifically, a weighting coefficient group including K + 1 weighting coefficients w is calculated based on K + 1 pieces of propagation path estimation information h.

  The combining unit 62 multiplies and combines the selected K + 1 received signals based on the weighting factor w calculated by the corresponding weighting factor calculating unit 56, and outputs the received signal r #.

  Each weighting factor calculation unit 56 is deactivated in response to the control signal Aoff, and a weighting factor w is input to the combining unit 62 so that the received signal input to the combining unit 62 passes without being combined. The Therefore, in this case, the same output signal r # as the received signal r input to the over-guard delay wave suppressor 50a is output from the over-guard delay wave suppressor 50a.

  FIG. 6 is a diagram illustrating a delayed wave suppression method according to the first modification of the first embodiment of the present invention.

  Referring to FIG. 6, the delayed wave suppression method according to the first modification of the first embodiment of the present invention is the same as that described above, with respect to the delayed wave exceeding the guard of the received signal received by each antenna. In this method, only a delay wave exceeding the guard is suppressed by applying an appropriate weighting factor w to the received signal between them and combining them.

  As shown here, assuming that there are K guard over delayed wave vectors v, the guard over delayed wave vectors of each antenna are expressed by the above-described equation (1).

  And the guard over delay wave matrix V based on the guard over delay wave vector of K + 1 antennas is expressed by the following equation.

Here, a guard-excluded delay wave matrix up to K + 1 antennas is shown.
In this example, the weight vector that suppresses the over-guard delay wave is calculated by multiplying the over-guard delay wave matrix V by the weight vector W.

That is, a weight vector that satisfies the above-described equation (3) is calculated.
The weight vector W is expressed by the following equation.

That is, the weight vector W is configured as K + 1 weighting factors w.
FIG. 7 is a diagram for explaining a case where a weight vector composed of K + 1 weight coefficients is developed.

  As shown in FIG. 7, it is necessary to calculate a weight vector W such that a value obtained by multiplying the guard excess delay wave matrix V by the weight vector W becomes zero.

  As shown here, the solution becomes indefinite because there are K simultaneous equations with K + 1 weighting factors w as variables.

  Therefore, in the present embodiment, a condition of the following equation is added so that the signal power before synthesis and after synthesis are equal.

  Based on this equation, it is possible to calculate a weight vector W that is K + 1 weighting factors w.

  In this example, the antenna combination selector 70 selects N sets of (K + 1) different received signals from the N antenna received signals according to the suppression delay wave number K.

Then, the selected (K + 1) received signals are output to the synthesis unit 62.
Further, propagation path estimation information from a propagation path estimation unit provided corresponding to each of the antennas that receives the input of the selected (K + 1) received signals is output to the weight coefficient calculation unit 56.

  In each weight coefficient calculation unit 56, propagation path estimation information corresponding to (K + 1) different received signals is input, and a weight vector W is calculated according to the above method.

  Then, in combining unit 62, (K + 1) received signals input according to the weight vector calculated by weight coefficient calculating unit 56 are combined to output received signal r #.

  In this configuration, the weighting coefficient calculation unit 56 according to the suppression delay wave number K and the weighting coefficient calculation in the combining unit 62 are performed, and a weight vector composed of K + 1 weighting coefficients is calculated. The amount of calculation can be reduced as compared with the configuration of the first form. Accordingly, the hardware scale can be reduced and the number of parts can be reduced.

  In the above description, the case where K + 1 weighting coefficients are calculated when it is assumed that there are K guard-extended delay wave vectors has been described. However, when it is assumed that there are K guard-extended delay wave vectors. In addition, it is possible to calculate K + 1 or more weighting factors according to a similar method.

(Modification 2 of Embodiment 1)
In the configuration according to the second modification of the first embodiment of the present invention, a case will be described in which an optimum selection is performed in the antenna combination selector.

  FIG. 8 is a diagram for explaining the configuration of the over-guard delay wave suppressor 50b according to the second modification of the first embodiment of the present invention.

  Referring to FIG. 8, guard over delayed wave suppressor 50b according to the second modification of the first embodiment of the present invention includes antenna combination selector 70 as compared with guard over delayed wave suppressor 50a. The difference is that it is replaced with 70 #. Specifically, the antenna combination selector 70 # is different in that a temporary combining unit 65 and a combination determination unit 66 are provided inside. The other points are the same, and detailed description thereof will not be repeated.

  The provisional synthesis unit 65 performs provisional synthesis by multiplying all different combinations of K + 1 received signals from the N received signals by weight vectors.

  In addition, the combination determination unit 66 selects an optimal combination that increases the signal power of the output signal temporarily combined by the temporary combining unit 65 for all the different combinations of the K + 1 received signals from the N received signals. The combination is determined so that

  In this example, N sets of (K + 1) different received signals are selected from the N antenna received signals according to the suppression delay wave number K.

  In this example, the antenna combination selector 70 selects the optimum combination that increases the combined signal power for the combination of K + 1 received signals from the N received signals. / N can be improved.

  In this example, before selecting the optimum combination, provisional synthesis is performed in the provisional synthesis unit 65, and the combination determination unit 66 determines the optimum combination that increases the signal power after provisional synthesis.

  The signal vector r # after provisional synthesis in the provisional synthesis unit 65 is expressed by the following equation.

  Here, patterns of all combinations of weight vectors Wa that select only K + 1 out of N received signals are listed.

As an example, there are _N C _{(K + 1) = 4} C ₂ = 6 combinations for N = 4 and K = 1.

Specifically, the weight vectors Wa1 to Wa6 are considered as candidates.
The weighting factor constituting the weight vector W is expressed as the following equation.

  Then, for each of the above six weight vectors Wa, an output signal r # after provisional synthesis is calculated as in the following equation.

  The signal energy E after provisional synthesis is expressed by the following equation.

  Note that this expression is an expression for obtaining an expected value, and is calculated by approximation with an expression replaced with a time average.

  Then, four signals having high signal power are selected from the six temporarily synthesized output signals, and a final weight vector W is calculated.

  By comparing the signal energies E based on the equations, it is possible to determine which received signal group has the higher signal level, and it is possible to select the signal level having the higher signal level.

  Specifically, the combination determination unit 66 receives the output signal after provisional synthesis from the provisional synthesis unit 65 according to each combination, and compares the signal energy. Then, K + 1 signals of a combination having a large signal level are output to the weight coefficient calculation unit 56.

  For example, the signal energies of the respective output signals when the six weight vectors Wa1 to Wa6 are used in the above example are set as signal energies E1 to E6.

The signal energy is assumed to be E2>E1>E4>E6>E5> E3.
In this case, E2, E1, E4, and E6 have large signal energy.

  Therefore, the weight vectors that increase the signal energy are the weight vectors Wa2, Wa1, Wa4, and Wa6.

  Therefore, the weight matrix X composed of the weight vector W is expressed as the following equation.

  In other words, based on the determination result of the combination determination unit 66, the signal energy of the signal output by selecting K + 1 out of the N reception signals output from the antenna combination selector 70 to each weighting coefficient calculation unit 56 is output. The increasing weight coefficient vector is output so as to be a combination calculated by the weight coefficient calculation unit 56.

  Thereby, as described above, the S / N can be improved by selecting an optimal combination that increases the combined signal power in the antenna combination selector 70.

(Modification 3 of Embodiment 1)
FIG. 9 is a diagram illustrating a configuration of the over-guard delay wave suppressor 50c according to the third modification of the first embodiment of the present invention.

  Referring to FIG. 9, the over-guard delay wave suppressor 50c according to the second modification of the first embodiment of the present invention further includes a delayed wave suppression determiner 80 as compared with the over-guard delay wave suppressor 50a. The point is different. The other points are the same, and detailed description thereof will not be repeated.

  The delayed wave suppression determiner 80 outputs the number K of guard-delayed delayed waves and the control signal Aon / Aoff for activation / deactivation based on the input of N pieces of propagation path estimation information h. .

  In the configuration of FIG. 5, the case of inputting the number K of guard-delayed delayed waves by a fixed input from the outside has been described. In this example, based on the input of N pieces of propagation path estimation information h, This is a method for determining the number K of over-guard delay waves, and the number of over-guard delay waves to be suppressed can be made variable.

  Therefore, it is possible to adjust the load of the weighting coefficient calculation process and the synthesis process in accordance with the number of delay waves exceeding the guard, so that it is possible to realize an efficient guard-over delay wave suppressor.

  In the configuration of the present application, the case where the delay wave suppression determiner 80 is provided inside the over-guard delay wave suppressor 50c has been described. It is also possible to provide it outside.

  In this configuration, the delayed wave suppression determiner 80 outputs the number K of guard-delayed delayed waves and the control signal Aon / Aoff for activation / deactivation based on the propagation path estimation information h. Although the case is described, a circuit that calculates the number K of over-guard delay waves based on the propagation path estimation information h and a circuit that outputs the control signal Aon / Aoff based on the propagation path estimation information h are separately provided. It is also possible to provide it.

(Embodiment 2)
In the first embodiment described above, the configuration in which the guard excess delay wave suppressor is provided before the FFT has been described. However, it is also possible to provide the guard excess delay wave suppressor after the FFT.

  FIG. 10 is a diagram for explaining a circuit equivalent to a circuit that synthesizes a received signal by multiplying it with a weighting coefficient before the FFT.

Referring to FIG. 10, here, in the upper, by multiplying the weighting coefficients w ₁ with respect to the received signal r in the preceding stage, for example, antenna 5-1 than FFT, the weight to the received signal r of the antenna 5-2 The case where the synthesized signal synthesized by multiplying by the coefficient w ₂ is converted into a frequency signal for each subcarrier by FFT is shown.

In the lower stage, the received signal of the antenna 5-1 is converted into a frequency signal for each subcarrier by FFT, and then multiplied by the weighting factor w ₁ . It shows a case where the signal is converted into a frequency signal, then multiplied by a weighting factor w ₂ and combined, and the upper configuration and the lower configuration are equivalent. That is, it is shown that the case where the received signal r is multiplied and combined by a weighting factor is equivalent to the case where the weighting factor is multiplied for each subcarrier and combined for each subcarrier. .

  FIG. 11 is a schematic functional block diagram of diversity receiver 1 # according to the second embodiment of the present invention.

  Referring to FIG. 11, diversity receiver 1 # according to the second embodiment of the present invention differs from diversity receiver 1 described in the first embodiment in the arrangement of guard excess delay wave suppressor 50.

  Specifically, a guard excess delay wave suppressor 50 # is provided between the FFT 10 and the equalizer 20 in place of the guard excess delay wave suppressor 50.

  Guard over delayed wave suppressor 50 # receives an output signal for each subcarrier from FFTs 10-1 to 10-N and propagation path estimation information from propagation path estimation units 15-1 to 15-N.

  FIG. 12 is a functional block diagram of guard excess delay wave suppressor 50 # according to the second embodiment of the present invention.

  Referring to FIG. 12, guard over delayed wave suppressor 50 # according to the second embodiment of the present invention includes a weight coefficient calculator 55 # and a synthesizer 60 #.

  Weight coefficient calculator 55 # operates based on an input of control signal Aon / Aoff for activating / deactivating delay wave suppressor 50.

  It is assumed that the control signal Aon / Aff is output from a determination circuit (not shown) based on the presence / absence of a delayed wave exceeding the guard. Specifically, it is possible to provide a determination circuit that determines whether there is a delayed wave exceeding the guard period based on the propagation path estimation information h and outputs the control signal Aon / Aoff based on the determination result. It is.

  Delay wave suppressor 50 # is activated based on the input of control signal Aon, and weighting factor calculator 55 calculates weighting factor w based on propagation path estimation information h. Then, the calculated weighting coefficient w is output to the synthesizer 60 #.

  The combiner 60 # receives the weighting coefficient calculated by the weighting coefficient calculator 55 # and multiplies the output signal for each subcarrier from the FFTs 10-1 to 10-N by the calculated weighting coefficient w. Then, a signal in which the delay wave exceeding the guard is suppressed is output. Here, the number of subcarriers is m.

  On the other hand, the guard excess delay wave suppressor 50 # is deactivated based on the input of the control signal Aoff, and the weighting factor calculator 55 # uses a predetermined weighting factor w determined in advance as a synthesizer 60. Output to #.

  When delay wave suppressor 50 # is deactivated, weighting coefficient w that passes through the output signal for each subcarrier input to combiner 60 # without being combined is combined with combiner 60 #. Is input.

  Here, as an example, a case where an output signal of the number of subcarriers m is input from each of FFTs 10-1 to 10-N to guard excess delay wave suppressor 50 # is shown. Further, the case where N pieces of propagation path estimation information h are input from the propagation path estimation units provided corresponding to the FFTs 10-1 to 10-N is shown.

  Then, weight coefficient calculator 55 # outputs N sets of different weight coefficient groups composed of N weight coefficients w to synthesizer 60 # based on N pieces of propagation path estimation information h. Then, in the combiner 60 #, there may be a case where each of the subcarriers included in each set of output signals is multiplied and combined with N weighting factors w included in each set of weighting factor groups and output. It is shown. As a result of multiplication with each set of weight coefficient groups, N sets of signals composed of the number of subcarriers m in which the over-guard delay wave is suppressed are output.

  Therefore, the output signals of the N sets of FFTs 10-1 to 10-N that have passed through the over-guard delay-wave suppressor 50 # are the signals of the number of subcarriers m received by the antennas 5-1 to 5-N in a pseudo manner. Can be considered.

  In this example, the case where the over-guard delay wave suppressor 50 having the configuration shown in FIG. 1 according to the first embodiment is replaced with the over-guard delay wave suppressor 55 is described. However, the present invention is not limited to this. In the configuration of the over-guard delay wave suppressor described in the first to third modifications, the replacement can be similarly performed.

  In this example, in the case of fixed reception, a method of calculating a weight vector in which a product obtained by multiplying the guard excess delay wave matrix V and the weight vector W is 0 has been described. However, in the case of mobile reception, Therefore, the delayed wave exceeding the guard changes with time, and the weight vector also needs to change with time.

  In the case of mobile reception, the weight vector may be calculated so as to satisfy the following equation.

  Here, V (t) and W (t) indicate a delayed wave matrix and a weight vector that change depending on time.

  As a method for calculating the above equation, it is also possible to calculate by applying an LMS (Least Mean Square), NLMS (Normalized LMS), or RLS (Recursive Least Squares) algorithm.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic functional block diagram of the diversity receiver 1 according to Embodiment 1 of this invention. It is a functional block diagram of the guard excess delay wave suppressor 50 according to Embodiment 1 of the present invention. It is a figure explaining the delayed wave suppression system according to Embodiment 1 of the present invention. It is a figure explaining the structure of the guard excess delay wave suppressor 50 when the number K of guard excess delay waves is set to 1 when there are two antennas. It is a figure explaining the structure of the guard excess delay wave suppressor 50a according to the modification 1 of Embodiment 1 of this invention. It is a figure explaining the system of the delay wave suppression according to the modification 1 of Embodiment 1 of this invention. It is a figure explaining the case where the weight vector comprised by K + 1 weight coefficient is expand | deployed. It is a figure explaining the structure of the guard excess delay wave suppressor 50b in the modification 2 of Embodiment 1 of this invention. It is a figure explaining the structure of the guard excess delay wave suppressor 50c according to the modification 3 of Embodiment 1 of this invention. It is a figure explaining the circuit equivalent to the circuit which multiplies a weighting coefficient with respect to a received signal and synthesize | combines before FFT. It is a schematic functional block diagram of diversity receiver 1 # according to the second embodiment of the present invention. It is a functional block diagram of guard excess delay wave suppressor 50 # according to Embodiment 2 of the present invention.

Explanation of symbols

  1, 1 # diversity receiver, 5-1 to 5-N antenna, 10-1 to 10-N FFT 15-1 to 15-N propagation path estimation unit, 20-1 to 20-N equalizer, 30 MRC , 50, 50a, 50b, 50c, 50 # Over guard delay wave suppressor, 55, 55 # combiner, 56-1 to 56-N Weight coefficient calculation unit, 60, 60 # combiner, 62-1 to 62- N combining unit, 70 antenna combination selector.

Claims (6)

A plurality of antennas for receiving orthogonal frequency division multiplexed signals and outputting received signals;
Delay wave suppression means for suppressing the delay wave of the reception signal according to the presence or absence of a delay wave exceeding the guard interval period for the reception signal;
A plurality of FFTs provided corresponding to the plurality of antennas, respectively, for performing a Fourier transform on the output signal of the delay wave suppressing means;
A plurality of propagation path estimation means provided corresponding to each of the plurality of FFTs, each of which outputs propagation path estimation information based on output signals from the plurality of FFTs;
Demodulating means for performing demodulation by synthesizing output signals of the plurality of FFTs that have passed through the plurality of propagation path estimating means;
The delayed wave suppression means includes
Weighting factor calculating means for calculating weighting factors for received signals from the plurality of antennas based on propagation path estimation information from the plurality of propagation path estimating means;
Combining means for combining received signals from the plurality of antennas in order to suppress a delayed wave of the received signal based on the weighting coefficient calculated by the weighting coefficient calculating means;
The weighting factor calculation means is a delay wave vector according to the delay wave when there is a delay wave exceeding the guard interval period for the received signal based on the propagation path estimation information from the plurality of propagation path estimation means. The weighting factor is calculated so that the value obtained by multiplying the constructed delay wave matrix and the weighting vector consisting of the weighting factor becomes 0 ,
The delayed wave suppression means includes
A determination unit for determining the presence or absence of a delayed wave exceeding a guard interval period for the received signal based on propagation path estimation information of the plurality of propagation path estimation means, and for determining the number (K) of delayed waves to be suppressed;
Selecting means for selecting a plurality of (N) different combinations composed of at least (K + 1) antennas among the plurality of (N) antennas in order to suppress K delayed waves;
The weighting factor calculating means is provided corresponding to each of the plurality (N) of different antenna combinations, each of which is a propagation path corresponding to the selected received signal of the at least (K + 1) antennas. A plurality of weight calculation units for calculating weight coefficients for the received signals from the at least (K + 1) antennas based on propagation path estimation information from the estimation means;
The synthesizing unit is provided corresponding to each of the plurality of weight calculation units, and each receives the reception signals from the at least (K + 1) antennas based on the weight coefficients calculated by the corresponding weight calculation units. A diversity receiver including a plurality of combining units to combine . The selection means is configured to generate a composite signal of received signals received by the at least (K + 1) antennas from among different combinations composed of the at least (K + 1) antennas among the plurality (N) of antennas. The diversity receiver according to claim 1 , wherein a plurality (N) of combinations are selected from the largest . Based on the propagation path estimation information of the plurality of propagation path estimation means, further comprising a determination unit that determines the presence or absence of a delayed wave exceeding the guard interval period for the received signal,
The diversity receiver according to claim 1, wherein the delay wave suppression unit is activated based on a determination result of the determination unit . A plurality of antennas for receiving orthogonal frequency division multiplexed signals and outputting received signals;
A plurality of FFTs provided corresponding to the plurality of antennas, respectively, and performing a Fourier transform on the reception signals of the corresponding antennas;
A plurality of propagation path estimation means provided corresponding to each of the plurality of FFTs, each of which outputs propagation path estimation information based on output signals from the plurality of FFTs;
Delay wave suppression means for suppressing a delay wave according to the presence or absence of a delay wave exceeding a guard interval period with respect to output signals from the plurality of FFTs;
Demodulating means for performing demodulation by synthesizing the output signal that has passed through the delay wave suppressing means,
The delayed wave suppression means includes
Weighting factor calculating means for calculating weighting factors for output signals from the plurality of FFTs based on propagation path estimation information from the plurality of propagation path estimating means;
Combining means for combining output signals from the plurality of FFTs to suppress delayed waves based on the weighting coefficient calculated by the weighting coefficient calculating means;
The weighting factor calculating means is a delay wave vector according to the delay wave when there is a delay wave exceeding the guard interval period for the output signal based on the propagation path estimation information from the plurality of propagation path estimating means. The weighting factor is calculated so that the value obtained by multiplying the constructed delay wave matrix and the weighting vector consisting of the weighting factor becomes 0,
Each of the output signals from the plurality of FFTs corresponds to an output signal group corresponding to the number of subcarriers,
The delayed wave suppression means includes
Based on the propagation path estimation information of the plurality of propagation path estimation means, the presence / absence of a delay wave exceeding the guard interval period for the output signals from the plurality of FFTs is determined, and the number (K) of delay waves to be suppressed is determined. A determination unit to perform,
Selecting means for selecting a plurality of different combinations composed of at least (K + 1) output signal groups from among the plurality of output signal groups in order to suppress K delayed waves;
The weighting factor calculating means is provided corresponding to different combinations of the plurality (N) of propagation path estimating means, each corresponding to the selected (K + 1) output signal groups. A plurality of weight calculation units for calculating weight coefficients for the at least (K + 1) output signal groups based on propagation path estimation information from the propagation path estimation means;
The synthesizing unit is provided corresponding to each of the plurality of weight calculation units, and each synthesizes the at least (K + 1) output signal groups based on the weight coefficients calculated by the corresponding weight calculation units. Diversity receiver including multiple combining units . The selecting means is a composite signal of the at least (K + 1) output signal groups from among different combinations composed of the at least (K + 1) output signal groups among the plurality (N) of output signal groups. The diversity receiver according to claim 4, wherein a plurality (N) of combinations having a larger value are selected . Based on the propagation path estimation information of the plurality of propagation path estimation means, further comprising a determination unit for determining the presence or absence of a delayed wave exceeding the guard interval period for the output signals from the plurality of FFTs,
The diversity receiver according to claim 4, wherein the delay wave suppression unit is activated based on a determination result of the determination unit .

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