JP5327745B2 - Interference wave canceling apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interference wave remover for removing interference waves so as to be suitable to each of OFDM signals depending on the presence or absence of large power interference. <P>SOLUTION: The interference wave remover has: an output power minimizing section for optimizing a weighting coefficient of each of a plurality of antenna elements on the basis of an output power minimum reference algorithm; a D/U estimating section for detecting the strength of interference waves out of the band of a used channel and performing D/U estimation; and a reception signal generation control section which, when the strength is less than a predetermined threshold value, optimizes the weighting coefficient of an antenna element for receiving a signal with respect to the output power minimizing section, and when the strength is not less than the threshold, holds the weighting coefficient of the antenna element. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an interference wave removing apparatus and method for receiving a desired wave by removing an interference wave from an adjacent channel on a frequency axis in an OFDM (Orthogonal Frequency Division Multiplexing) system.

In the OFDM system, the symbol synchronization timing of each OFDM symbol in the OFDM signal is detected from the received signal received by the antenna element, using a preamble provided at the front end of the OFDM signal packet. At this symbol synchronization timing, the received signal is decoded by synchronizing the timing of performing the FFT on the OFDM symbol with high accuracy (see, for example, Patent Document 1).
However, a high-power spurious interference wave (D / U = about −20 dB from a channel existing adjacent on the frequency axis, which is an interference wave caused by an unnecessary component such as an unnecessary wave, If there is a large power interference wave), the symbol synchronization timing described above cannot be detected, and interference removal by MMSE (Minimum Mean Square Error) using a reference signal cannot be performed.

JP 2006-186421 A

Therefore, in order to suppress high power interference without using a reference signal, an output power minimization method that can invert SIR (Signal to Interference Ratio) between input and output, for example, PIAA (Power Inversion Adaptive Array) is applied. To do is one effective means.
If the output power minimization method described above is applied unnecessarily, only the desired wave arrives, and if the interference wave does not exist or is at a very low level, the incoming desired wave is suppressed. There is a problem that it ends up.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an interference wave removing apparatus that removes interference waves suitable for each OFDM signal depending on the presence or absence of high power interference.
That is, an object of the present invention is to provide an interference wave removal apparatus that performs interference wave removal on a received signal based on the output power minimization method when MMSE cannot be applied due to interference.

The interference wave canceling apparatus of the present invention detects the intensity of an interference wave outside the band of the channel being used, and an output power minimizing unit that optimizes the weighting coefficient of each of the plurality of antenna elements, using the minimum output power reference algorithm. and a D / U estimation unit for obtaining the D / U estimation value by performing a D / U estimation, the case of less than the threshold set D / U estimate in advance, with respect to the output power minimizing section, receives a signal to optimize the weighting coefficients of the antenna elements, whereas if the D / U estimation value is not less than the threshold, have a received signal generation control portion for holding a weighting coefficient of the antenna elements, the plurality of antenna elements A plurality of diversity branches are configured by combination, the D / U estimation unit obtains the D / U estimation value for each diversity branch, and the reception signal generation control unit includes each of the diversity branches. The estimated value of D / U is compared with the preset threshold value. When the estimated D / U value is equal to or greater than the threshold value, the weight of the corresponding diversity branch is constrained, and the estimated D / U value is the threshold value. If the D / U estimation value of all the diversity branches is less than the threshold, the constraint on the weight of the corresponding diversity branch is released, the output power minimization unit generates a reception signal, and the D / U estimation value of all the diversity branches is less than the threshold. Only the weight of the diversity branch having the maximum U estimation value is constrained, and the weights of the other diversity branches are released .

In the interference wave canceling apparatus of the present invention, the D / U estimator samples a signal using a time window function having a length that is a preset integer multiple of the OFDM symbol length, and performs frequency conversion of the sampled signal. Thus, the interference signal strength that is the strength of the interference signal outside the band that is outside the frequency band that is being used as the carrier, and the data signal strength that is the strength of the data signal within the band that is being used as the carrier, The D / U estimated value is obtained using the interference signal strength and the data signal strength.

In the interference wave canceling apparatus of the present invention, the D / U estimation unit obtains a first frequency average that is an average value of the interference signal intensity in the frequency range outside the band, and the data signal intensity in the frequency range within the band. A second frequency average that is an average value of the first frequency average is obtained, the first frequency average is subtracted from the second frequency average, and the subtraction result is divided by the first frequency average. Is output as the estimated D / U value.

In the interference wave canceling apparatus of the present invention, the D / U estimation unit associates the first frequency conversion pattern of the signal sampled by the time window function measured in advance with the value of D / U. A storage unit for storing an estimation table; a second frequency pattern obtained by sampling the received signal using the time window function is searched for a first frequency conversion pattern that is most similar; The D / U value stored in the storage unit corresponding to the frequency pattern of 2 is output as the D / U estimated value of D / U.

In the interference wave elimination method of the present invention, the output power minimization unit uses the output power minimization process in which the weight coefficient of each of the plurality of antenna elements is optimized by the output power minimum reference algorithm, and the D / U estimation unit uses the output power minimization process. The D / U estimation process for detecting the intensity of the interference wave outside the band of the current channel and performing D / U estimation; and the received signal generation control unit, when the intensity is less than a preset threshold, to unit, the signal is optimized weighting coefficients of the antenna elements for receiving, whereas if the intensity is greater than or equal to the threshold value, have a received signal generation control step of holding the weight coefficients of the antenna elements, the D A / U estimation unit obtains a D / U estimate value of D / U for each diversity branch configured by the combination of the plurality of antenna elements, and the reception signal generation control unit determines the D / U of each of the diversity branches. The estimated value of U is compared with the preset threshold value. When the estimated D / U value is equal to or greater than the threshold value, the weight of the corresponding diversity branch is constrained, and the estimated D / U value is less than the threshold value. In the case, the constraint on the weight of the corresponding diversity branch is released, the reception power is generated by the output power minimization unit, and the D / U estimation is performed when the D / U estimation values of all the diversity branches are less than the threshold value. Only the weight of the diversity branch having the maximum value is constrained, and the weights of the other diversity branches are released .

  According to the present invention, a technique for measuring the magnitude of a D / U between a desired wave for transmitting necessary data and an interference wave caused by an unnecessary unnecessary wave component by a simple method and removing the interference wave By selecting whether or not to perform the output power minimization method, when the D / U is small (when the interference wave is large), weighting synthesis of each antenna signal is performed by the output power minimization method. When the value is large, the output power minimization method is not performed, the symbol synchronization timing is obtained, the FFT is performed with the OFDM symbol length, and the weighting synthesis by MMSE is performed for each subcarrier of each antenna signal. Because interference waves are removed, interference waves can be easily removed with higher accuracy than in the past, and symbol synchronization in OFDM signals can be acquired. .

It is a block diagram which shows the structural example of the OFDM receiver using the interference wave removal apparatus by the 1st and 2nd embodiment of this invention. It is a conceptual diagram which shows the concept of the pattern which consists of the spectrum intensity | strength for every frequency which carried out the Fourier transform of the OFDM signal of the time width cut out by the time window function. It is a block diagram which shows the structural example of the interference wave removal part 5 in FIG. 5 is a flowchart illustrating an operation example of the OFDM receiver using the interference wave canceller according to the first embodiment of the present invention.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing a configuration example of an OFDM receiver using an interference wave canceller according to an embodiment of the present invention. The OFDM receiving apparatus of this embodiment includes a frequency filter unit 1, a quadrature detection unit 2, an A / D conversion unit 3, an FFT unit 4, an interference wave removal unit 5, and a demodulation unit 6.

The frequency filter unit 1 extracts only the frequency components of a preset frequency band from the received signal received from the antenna element, that is, extracts the OFDM signal transmission band and sends the OFDM signal to the next-stage quadrature detection unit 2 Output as. Here, due to the characteristics of the frequency filter unit 1, a part of the adjacent frequency band outside the OFDM signal transmission band is included and extracted.
In addition, since the frequency band outside the OFDM signal transmission band adjacent to the OFDM signal transmission band is used for the calculation described later, the frequency to be filtered by the frequency filter unit 1 may be set so as to be included to some extent.
The quadrature detection unit 2 converts the input OFDM signal from a real-time signal to a complex time signal composed of an I signal (Ich) and a Q signal (Qch), and outputs the complex signal to the A / D conversion unit 3 at the next stage.
The A / D conversion unit 3 performs A / D conversion on the I signal and the Q signal, and outputs the A / D converted signal to the FFT unit 4 in the next stage in order to determine whether or not interference removal is necessary. .

  The FFT unit 4 performs Fourier transformation on the OFDM signal, that is, performs transformation from the time domain to the frequency domain, and outputs the transformation result to the interference wave removing unit 5 at the next stage. Here, the FFT unit 4 performs Fourier transform not only on the OFDM signal transmission band but also on a range including a frequency band outside the adjacent OFDM signal transmission band. Here, when sampling the time width for Fourier transform, the FFT unit 4 samples the OFDM signal by applying a preset time window function. This time window function uses a Gaussian window, a Hamming window, or the like so that it is not affected by signals in the band as much as possible when measuring signals outside the band. Further, the time width of the time window function is set as a plurality of symbol lengths, for example, four symbol lengths, as time intervals for performing the Fourier transform in order to improve the Fourier transform resolution.

Therefore, the FFT unit 4 cuts out sections of time widths of a plurality of symbols in the region of the pilot of the OFDM signal packet (the preamble in the packet and the Same symbol pattern), and, as shown in FIG. As the intensity pattern, a spectrum intensity pattern at each frequency of the OFDM signal transmission band and the outside of the OFDM signal transmission band adjacent to this band is output.
Further, after the D / U is improved by an interference wave removing unit 5 described later, the FFT unit 4 acquires symbol synchronization timing by the remaining preamble pilots in the OFDM signal packet, and each symbol is synchronized with this symbol synchronization timing. Are synchronized with each other, Fourier-transformed for each symbol of the I signal and Q signal, and output to the demodulator 6.

The interference wave removal unit 5 performs D / U estimation based on the spectrum intensity for each frequency subjected to Fourier transform, determines whether or not to perform interference wave removal by the output power minimization method based on the D / U value, and performs OFDM In order to remove the interference wave included in the signal, a weighting factor for multiplying the output of each antenna element is calculated based on the output power minimization criterion. A multiplier (not shown) multiplies the output of each antenna element by this weight coefficient, and the multiplication result is input to the FFT unit 4.
The demodulation unit 6 performs demodulation processing by performing FFT on the OFDM signal from which the interference wave has been removed by the FFT unit 4 at symbol synchronization timing, and outputs a demodulated signal.

Next, the interference wave removing unit 5 will be described in detail with reference to FIG. FIG. 3 is a conceptual diagram showing a configuration example of the interference wave removing unit 5 in FIG.
The interference wave removal unit 5 includes an output power minimization unit 51, a reception signal generation control unit 52, a D / U estimation unit 53, and a storage unit 54.

The D / U estimator 53 receives a desired signal (undesired signal) and an unnecessary signal (undesired signal) according to the spectrum intensity for each frequency within the OFDM signal transmission band and outside the OFDM signal transmission band input from the FFT unit 4. D / U, which is the ratio of
That is, for example, the D / U estimation unit 53 causes the storage unit 54 to temporarily store the spectrum intensity for each frequency.
Then, the D / U estimation unit 53 sequentially reads the spectrum intensity for each frequency from the storage unit 54, obtains a first average value of the spectrum intensity at each frequency outside the OFDM signal transmission band, and determines the OFDM signal transmission band. A second average value of the spectrum intensity at each frequency is obtained. Here, the spectrum intensities of all the antenna elements for each frequency are added, and the first and second average values are obtained as the average values between all the antenna elements.

The first average value indicates the average value of the interference wave, that is, the value of U, and the second average value is the value of U + D in which the interference wave is superimposed on the desired wave. Therefore, if the first average value is subtracted from the second average value, and the subtraction result is divided by the first average value,
{(D + U) -U} / U = D / U can be calculated.
Accordingly, the D / U estimation unit 53 calculates the first average value and the second average value, and calculates the numerical value of D / U by calculating the expression {(D + U) −U} / U. To do.

The reception signal generation control unit 52 determines whether or not the D / U value obtained by the D / U estimation unit 53 is greater than or equal to a preset threshold value. If the D / U value is greater than or equal to this threshold value, In order to achieve synchronization, the weights (weighting coefficients) for the antenna elements remain in the current state, that is, all are set to 1, and the signal input from the FFT unit 4 is output to the demodulation unit.
On the other hand, the received signal generation control unit 52 activates the output power minimizing unit 51 because symbol synchronization cannot be achieved when the D / U value obtained by the D / U estimating unit 53 is less than a preset threshold value. The weight for the antenna element is optimized by the output power minimizing unit 51.
Here, the output power minimizing unit 51 performs a calculation for optimizing the weight of each antenna element according to the output power minimization criterion, and performs the process of removing the interference wave.

The output power minimization criterion is performed by a blind algorithm (which does not require a reference signal), and one weight of an antenna element is set to 1 so that a solution for minimizing a predetermined evaluation function does not become 0. ing. Here, it is assumed that the total number of input signals is equal to the number of antenna elements, the desired wave is one wave, and the relationship is interference power >> desired wave power.
For this reason, the solution of the evaluation function is set to a value other than 0, and the output of each antenna element is multiplied by the weight under the constraint for obtaining the output of the desired wave so that the output power is minimized. Set the weighting factor. When this output power is minimized, the output power of the desired signal can be secured, the output power of unnecessary interference waves can be reduced, and unnecessary waves can be removed.

  The above-described interference wave removal processing is performed within the time range of the pilot signal added to the OFDM signal composed of a plurality of symbols, and after symbol synchronization is acquired, the FFT unit 4 has a time width corresponding to the symbol length. Using the time window function, the OFDM signal is sampled and frequency conversion is performed for each symbol length.

In the D / U estimation unit 53 described above, the first average value of the spectrum intensity at each frequency in the OFDM signal transmission band and the second average value of the spectrum intensity at each frequency outside the OFDM signal transmission band are obtained, and D Although / U estimation is performed, D / U estimation may be performed by the following processing.
A reference pattern of spectrum intensity for each frequency, which has been subjected to Fourier transform in a time range of a plurality of symbols, is stored in advance in correspondence with the D / U value at that time.

  Then, the reception signal generation control unit 52 searches the storage unit 54 for the reference pattern similar to the spectrum intensity pattern for each frequency input from the FFT unit 4, and determines the D / U corresponding to the most similar reference pattern. A numerical value is output as an estimated value of D / U. Here, the spectral intensity pattern for each frequency input from the reference pattern and the FFT unit is divided by the maximum value of the spectral intensity in each pattern and standardized for comparison. For the detection of similarities, for example, it is assumed that the differences in the spectral intensities of the corresponding frequencies are obtained and the patterns having the smallest sum of the differences are similar to each other.

Next, the operation of the OFDM receiver of this embodiment will be described with reference to FIGS. Here, FIG. 4 is a flowchart showing an operation example of the OFDM receiver according to the present embodiment.
The frequency filter unit 1 filters the received OFDM signal with a preset frequency band (an OFDM signal transmission band and a frequency band outside the OFDM signal transmission band in a certain frequency range adjacent thereto), and a quadrature detection unit at the next stage 2 (step S1).
The quadrature detection unit 2 converts the input OFDM signal from a real time signal to a complex time signal composed of an I signal (Ich) and a Q signal (Qch), and outputs the complex signal to the A / D conversion unit in the next stage.
When the OFDM signal is input, the A / D conversion unit 2 performs A / D conversion on the OFDM signal, and outputs the A / D converted and digitized OFDM signal to the FFT 4 at the next stage. (Step S2).

The FFT unit 4 samples a time window function having a time width of a plurality of symbol lengths over the detected OFDM signal, performs a Fourier transform on the sampled OFDM signal (step S3), and obtains each frequency obtained A pattern composed of the spectrum intensity is output to the interference wave removing unit 5 at the next stage.
When the above pattern is input, in the interference wave removal unit, the D / U estimation unit 53 adds the spectrum intensity of each pattern for each frequency in the pattern of all antenna elements, and then the spectrum intensity outside the OFDM signal transmission band. A first average value (U) and a second average value (D + U) of the spectrum intensity in the OFDM signal transmission band are obtained, and D (U) / U = D / U The numerical value of / U is calculated (step S4), and the calculated numerical value is output to the reception signal generation control unit 52 as the estimated value of D / U.

  Then, the reception signal generation control unit 52 reads a threshold value set in advance in the storage unit 54, and compares this threshold value (set value) with the input estimated value of D / U (step S5). If the estimated value of D / U is less than the threshold value, the process proceeds to step S6. If the estimated value of D / U is equal to or greater than the threshold value, the process proceeds to step S7.

When the estimated value of D / U is less than the threshold value, the output power minimizing unit 51 optimizes the weight of each antenna element and removes interference waves based on the processing described above corresponding to the output power minimization criterion ( Step S6).
The processing from step S2 to step S6 described above is performed in the range of the region where the pilot symbols in the preamble of the OFDM signal packet are arranged, and the D / U is improved in the data symbols of the subsequent packets. In this state, the FFT unit 4 performs symbol synchronization, performs Fourier transform for each symbol in its time width, generates a spectrum intensity pattern (subcarrier) for each frequency, and sends the symbol pattern to the demodulator 6. Output sequentially.

  Then, the demodulator 6 performs symbol demodulation processing using the pattern for each symbol input from the FFT unit 4 (step S7).

<Second Embodiment>
The second embodiment of the present invention will be described below with reference to the drawings. The configuration of the OFDM receiver using the interference wave canceller in the second embodiment is the same as that of the first embodiment.
The configuration and operation of the second embodiment different from those of the first embodiment will be described below.
In the first embodiment, when the fading correlation between antenna elements is high (the antenna elements are arranged at half-wavelength intervals as in an adaptive array), the output power antenna minimization method described above is used to perform D / The U value is inverted between the input and output, that is, the interference wave can be effectively removed from the OFDM signal received from the antenna element.

  However, when diversity branch (for example, in the case of space diversity, the antenna element interval is set so that the fading correlation between branches is low), the fading correlation between antenna elements is low. For example, assuming two branches, the weight of a branch having a large D / U is constrained to be 1, and the weight of a branch having a small D / U is not constrained. The SIR of the branch is reversed to become the weighted combined output SIR. Hereinafter, in the present embodiment, a description will be given assuming that the branch is composed of one antenna element.

For this reason, the D / U estimation unit 53 performs the D / U estimation performed in the first embodiment for each antenna element.
Further, the reception signal generation control unit 52 constrains the weight of an antenna element having a D / U value greater than or equal to a threshold value, and does not constrain the weight of an antenna element that has a D / U value less than the threshold value. The minimizing process is performed by the output power minimizing unit 51.
Also, when all antenna elements are D / U less than the threshold value, as described above, only the weight of the antenna element with the maximum D / U is constrained, and the restraints of the weights of the other antenna elements are released. Minimize output power.
Then, the output power minimizing unit 51 obtains only the weight of the unconstrained antenna element by the output power minimization method, and the constraint condition for obtaining the desired wave output (the restricted antenna element changes the weight). Without changing the weight factor of the unconstrained antenna elements), and multiplying the output of each antenna element by the weight, the weight factor of the unconstrained antenna element is Set.
Subsequent processing is performed in the same manner as in the first embodiment.

As described above, in a configuration in which antenna elements are arranged at half-wavelength intervals as in an adaptive array, when the D / U value is not so bad, for example, the spectral intensity of the interference wave is near the threshold value. Is high, the fading correlation between the antenna elements is high. Therefore, even if the weight of the antenna element is optimized by the output power minimization method, it is assumed that the numerical value of D / U cannot be improved.
For this reason, when optimizing the weight of antenna elements by arranging the antenna elements to be diversity branches and reducing the fading correlation between the antenna elements, there is no fading correlation between the antenna elements. The probability that the numerical value of D / U of an element improves will become high, and the numerical value of D / U in all the diversity branches can be improved more. Furthermore, when the intensity of the interference wave is low, a diversity gain can be obtained as a general effect.

  Further, a program for realizing the functions of the antenna output power minimizing unit 51, the D / U estimating unit 53, and the received signal generation control unit 52 in FIG. 1 is recorded on a computer-readable recording medium. The interference wave removal processing may be performed by causing the computer system to read and execute the program recorded in the above. Here, the “computer system” includes an OS and hardware such as peripheral devices.

Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within a scope not departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Frequency filter part 2 ... Quadrature detection part 3 ... A / D conversion part 4 ... FFT part 5 ... Interference wave removal part 6 ... Demodulation part 51 ... Output power minimization part 52 ... Received signal generation control part 53 ... D / U Estimating unit 54 ... storage unit

Claims (5)

An output power minimizing unit that optimizes a weighting factor of each of the plurality of antenna elements by an output power minimum reference algorithm;
A D / U estimator that detects the intensity of an interference wave outside the band of the channel being used and performs D / U estimation to obtain a D / U estimation value ;
When the estimated D / U value is less than a preset threshold value, the output power minimizing unit optimizes the weighting factor of the antenna element that receives the signal, while the estimated D / U value is equal to or greater than the threshold value. If, have a received signal generation control portion for holding a weighting coefficient of the antenna elements,
A plurality of diversity branches are configured by a combination of the plurality of antenna elements,
The D / U estimation unit obtains the D / U estimation value for each diversity branch,
The reception signal generation control unit is
The estimated D / U value of each diversity branch is compared with the preset threshold value. When the estimated D / U value is equal to or greater than the threshold value, the weight of the corresponding diversity branch is constrained, and the D / U When the estimated value is less than the threshold value, the constraint on the weight of the corresponding diversity branch is released, the reception power minimizing unit is generated, and the D / U estimated values of all the diversity branches are less than the threshold value. In this case, the interference wave removing device is characterized in that only the weight of the diversity branch having the maximum D / U estimation value is constrained and the constraint of the weight of the other diversity branch is released . The D / U estimation unit samples a signal using a time window function having a predetermined integer multiple of the OFDM symbol length, and uses the sampled signal as a carrier by performing frequency conversion. The interference signal strength that is the strength of the interference signal outside the frequency band that is outside the frequency band, and the data signal strength that is the strength of the data signal within the band used as the carrier, and the interference signal strength and the data signal strength The interference wave canceling apparatus according to claim 1, wherein the estimated D / U value is obtained by using. The D / U estimator obtains a first frequency average that is an average value of the interference signal intensity in a frequency range outside the band, and a second frequency that is an average value of the data signal intensity in the frequency range within the band. An average is obtained, the first frequency average is subtracted from the second frequency average, the subtraction result is divided by the first frequency average, and the division result is output as the D / U estimate value of D / U. The interference wave removing device according to claim 2, wherein The D / U estimation unit is
A storage unit that stores a D / U estimation table in which a first frequency conversion pattern of a signal sampled by the time window function measured in advance and a D / U value are associated with each other; For the second frequency pattern obtained by sampling with the window function, the most similar first frequency conversion pattern is searched, and the D / D stored in the storage unit corresponding to the searched second frequency pattern. The interference wave canceling apparatus according to claim 2, wherein the value of U is output as the D / U estimated value of D / U. The output power minimizing unit optimizes the weighting factor of each of the plurality of antenna elements by the output power minimum reference algorithm, and
A D / U estimation process for detecting the intensity of interference waves outside the band of the channel used by the D / U estimation unit and performing D / U estimation;
When the received signal generation control unit optimizes the weighting factor of the antenna element that receives the signal when the strength is less than a preset threshold value, while the strength is equal to or greater than the threshold value , have a received signal generation control step of holding the weight coefficients of the antenna elements,
The D / U estimation unit obtains a D / U estimation value of D / U for each diversity branch configured by a combination of the plurality of antenna elements,
The reception signal generation control unit is
The estimated D / U value of each diversity branch is compared with the preset threshold value. When the estimated D / U value is equal to or greater than the threshold value, the weight of the corresponding diversity branch is constrained, and the D / U When the estimated value is less than the threshold value, the constraint on the weight of the corresponding diversity branch is released, the reception power minimizing unit is generated, and the D / U estimated values of all the diversity branches are less than the threshold value. In this case, only the weight of the diversity branch having the largest D / U estimation value is constrained, and the constraint of the weight of the other diversity branch is released .

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