JP2008167479A - Array antenna control apparatus and array antenna control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adaptively limit the number of antennas when receiving a high level signal at the time of multi-antenna reception, reduce calculation error, and increase calculation accuracy.
In an array antenna control apparatus for controlling the directivity of an array antenna having a plurality of antenna elements, received signal strength calculation means for calculating the signal strength of a signal received by the antenna element, and weighting for each antenna element A reception control means for calculating and synthesizing the received signals and an antenna number changing means for changing the number of the antenna elements when the reception level is high are provided.
[Selection] Figure 1

Description

  The present invention relates to an array antenna control apparatus and an array antenna control method for controlling an array antenna having a plurality of antenna elements.

  A time division multi-carrier transmission system has been proposed as a wireless communication system for transmitting data at high speed and in large quantities. The time division multi-carrier transmission scheme is a scheme for dividing data to be transmitted in time series and transmitting the data. At this time, when a reference signal is inserted for each time-division data and reception is performed using a plurality of antennas, a signal can be obtained using an antenna weight calculated based on a correlation between the reception signal and the reference signal. .

  A block diagram of such an array antenna control apparatus is shown in FIG. Signals received by the antennas (Antenna 1 to M) are processed in a radio frequency band such as amplification and frequency conversion by a radio unit (RF Block) and a digital downsampling converter (DDC). The signal processed in the radio frequency band is input to the DSP via the synthesis control means (Path Control). In the DSP, the received signal strength calculation means (Power Combiner) calculates the signal strength of a certain section, and the correlation calculation means (MxM Matrix Processing) calculates the correlation between the signal strength and the noise strength by matrix calculation of the signal strength and the noise strength. To do. A compensation coefficient for compensating the deviation of the frequency and time characteristics is calculated for the received signal subjected to the matrix calculation by the frequency compensator (Frequency Estimator) and the time compensator (Timing Estimator). Then, the reception control means (Rx Compensator) weights the reception signal using the calculated compensation coefficient, thereby extracting a desired signal from the reception signal. Then, the signal is demodulated by a demodulating means (Decoding) and output to a data bus via a logical circuit (Physical to Logical).

In addition, as a prior art technique for reducing the amount of computation for such an adaptive array antenna, vector multiplication processing is performed by multiplying a transmission signal used in an adaptive transmission diversity array by a complex weight coefficient, and a transmission information sequence at the time of modulation is converted into amplitude and phase. A technique has been proposed in which a transmission process of an adaptive array antenna and a complex weight coefficient are operated with a small amount of processing by performing an operation of mapping in a two-dimensional signal space represented by (for example, Patent Document 1). reference.).
JP-A-11-32028

  As described above, when separating signals mixed in the same space in the time division multi-carrier transmission method, matrix calculation is performed by reception of the multi-antenna, and signal components and noise components (including interference wave components) are calculated from the values. Performs weighting to be estimated. However, in the processing, when the signal power is extremely higher than the noise power, the error (overflow, underflow) caused by the matrix calculation increases as the number of antennas increases.

  The present invention has been made to solve the above-described problems. When a high-level signal is received at the time of multi-antenna reception, the number of antennas is adaptively limited to reduce calculation error, and calculation is performed. The purpose is to increase accuracy.

  In a first aspect of the present invention, there is provided an array antenna control apparatus for controlling directivity of an array antenna having a plurality of antenna elements, a received signal strength calculation means for calculating a signal strength of a signal received by the antenna element, and the received signal strength. Antenna number changing means for suppressing an antenna element that gives a relatively large signal strength when the signal strength calculated by the calculating means is larger than a predetermined threshold and changing the number to reduce the number of antenna elements; It is characterized by.

  According to a second invention, in the first invention, a time compensation unit that calculates a coefficient for compensating a time axis characteristic of the received signal in a state where the antenna element is suppressed by the antenna number changing unit, and The received signal is weighted by using a frequency compensator for calculating a coefficient for compensating a frequency characteristic of the received signal, and a coefficient calculated by the time compensator and the frequency compensator. And a reception control means for extracting a desired signal from the receiver.

  A third invention is an array antenna control method for controlling the directivity of an array antenna having a plurality of antenna elements, the step of calculating the signal strength of a signal received by the antenna element, and the calculated signal strength And controlling to reduce the number of antenna elements by suppressing antenna elements that provide a relatively large signal strength when is greater than a predetermined threshold value.

  According to the present invention, when transmission / reception is performed using two or more multi-antennas, when the reception level is high, the number of reception antennas is logically limited, whereby the matrix generated in the matrix calculator of the reception signal Calculation errors can be reduced, signal reception performance can be maintained, and resources can be used effectively.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of an antenna control apparatus according to the present invention.

  A plurality (M) of antenna elements (Antenna 1 to M) for transmitting and receiving radio signals are provided. A radio unit (RF Block) is connected to each antenna element. The radio unit includes radio means for generating a radio signal in a radio communication frequency band and reference signal means for providing a modulation frequency to the radio means.

  A digital downsampling converter (DDC) that converts the frequency of the received signal output from the wireless unit is connected to the wireless unit. The received signal output from the DDC is input to the DSP via the synthesis control means (Path Control).

  The radio unit is connected to a digital upsampling converter (DUC) that converts the frequency of a transmission signal input to the radio unit. The transmission signal input to the DUC is supplied from the DSP via the synthesis control means (Path Control).

  The combination control means (Path Control) is constituted by a distributor, and inputs the received signal to the received signal intensity calculating means (Power Combiner) and the reception control means (Rx Compensator). Further, the burst signal generated by the transmission signal synthesis means (Tx Burst Builder) is weighted based on the control signal generated by the transmission parameter generation means (Tx Parametor) and distributed to each antenna.

  Further, a central processing unit (CPU) (not shown) is connected to the DSP. The CPU exchanges data with a plurality of DSPs and performs control for realizing high-speed data transmission. In addition to the DSP, the CPU controls the entire array antenna control apparatus of the present embodiment by setting operation parameters of the DUC and DDC and performing wireless control.

  The DSP performs time processing on the received signal output from the DDC and performs signal processing in units of frequency. That is, a modulated signal discretized at a predetermined sampling time sent from the DDC is received, and the received signal strength calculation means (Power Combiner) calculates the signal strength (RSSI) of a certain section (for example, a reference signal in a burst signal). Then, the reception level adjusting means (Power Combiner) adjusts the signal strength (reception level) of the received signal. The correlation calculation means (MxM Matrix Processing) obtains the covariance from the received signal, normalizes the received signal, and calculates the correlation between the signal strength and the noise strength.

  The antenna number changing means (Array Position Controller) logically changes the number of receiving antennas. That is, when the reception level is high, a matrix from which high-level signal components are excluded is generated (see FIG. 3B), so that overflow or underflow does not occur at the time of matrix calculation. Reduce the error that occurs and increase the calculation accuracy.

  The frequency compensation means (Frequency Estimator) calculates a compensation coefficient for compensating the frequency characteristic of the received signal from which the high level signal component has been removed. The time compensation means (Timing Estimator) calculates a compensation coefficient for compensating the time characteristic (time axis deviation) of the received signal from which the high level signal component has been removed.

  The reception control means (Rx Compensator) extracts a desired signal from the reception signal by weighting the reception signal using the compensation coefficient calculated by the time compensation means and the frequency compensation means. Further, the reception control means corrects the reception signal so that the difference between the reference signals included in the two locations in the burst signal is eliminated. That is, when the reference signal having the same content is provided at the beginning and end of the burst signal, a difference occurs in the reference signal due to expansion or contraction of the burst signal itself due to delay or phase shift, so that the difference is eliminated. Correct the burst signal to improve the quality of the received signal.

  The demodulating means (Decoding) demodulates the received signal. A logical circuit (Physical to Logical) outputs data from the DSP to the data bus.

  The DSP also has a transmission function. A logical circuit (Physical to Logical) inputs data from the data bus to the DSP. The modulation means (Encoding) modulates a signal input from the data bus. The transmission signal synthesis means (Tx Burst Builder) generates a burst signal for transmission using the modulated signal.

  The transmission parameter generation means (Tx Parametor) generates a weighting coefficient for distributing the transmission signal based on the compensation coefficient used by the reception control means (Rx Compensator).

  Next, the operation of the array antenna control apparatus according to the embodiment of the present invention will be described.

  Signals received by the antennas (Antenna 1 to M) are processed in a radio frequency band such as amplification and frequency conversion by a radio unit (RF Block) and a digital downsampling converter (DDC). The signal processed in the radio frequency band is input to the DSP via the synthesis control means (Path Control).

  In the DSP, the received signal strength calculation means (Power Combiner) calculates the signal strength of a certain interval (for example, the reference signal in the burst signal), and the correlation calculation means (MxM Matrix Processing) calculates the correlation between the signal strength and the noise strength. To do. Based on the matrix calculation result, the antenna number changing means (Array Position Controller) logically reduces the number of reception antennas by eliminating signal components having a high reception level.

  The received signal from which the high-level signal component has been removed is subjected to frequency compensation means (Frequency Estimator) to calculate a compensation coefficient for compensating the frequency characteristic, and the time compensation means (Timing Estimator) is used to calculate the time characteristic (time axis deviation). ) Is calculated. And a reception control means (Rx Compensator) weights a received signal by matrix calculation using the calculated compensation coefficient, and extracts a desired signal.

  The extracted signal is demodulated by a demodulating means (Decoding) and output to a data bus via a logical circuit (Physical to Logical).

  On the other hand, a transmission signal input from the data bus to the DSP is input to a modulation means (Encoding) via a logical circuit (Physical to Logical) and modulated. Then, a transmission burst signal is generated in the transmission signal combining means (Tx Burst Builder), weighted using the weighting coefficient generated by the transmission parameter generating means (Tx Parametor) in the combining control means (Path Control), Distributed to the antenna. Then, processing in a radio frequency band such as amplification and frequency conversion is performed by a digital up-sampling converter (DUC) and a radio unit (RF Block), and is radiated from antenna elements (Antenna 1 to M).

  FIG. 2 is a flowchart of the best mode array antenna control apparatus for carrying out the present invention.

  First, the received signal strength (RSSI) is compared with a predetermined threshold δ to determine whether the RSSI is greater than the threshold δ (S101). If the RSSI is not larger than the threshold value δ as a result of the comparison determination, there is a low possibility that an error such as overflow or underflow will occur in the matrix operation, so the matrix elements are not masked (without limiting the number of antennas). Proceeding to S107, a weighting operation is performed (S107), and this process ends. Here, L is a Cholesky factor of a corrected matrix of signals input from a plurality of antennas.

  Subsequently, the maximum value (Max (SINRu)) for each user of the signal-to-interference power ratio is compared with a predetermined threshold γ to determine whether Max (SINRu) is larger than the threshold γ (S102). If Max (SINRu) is not greater than the threshold γ as a result of the comparison determination, it is unlikely that errors such as overflow or underflow will occur in the matrix operation. Therefore, without masking the matrix elements (without limiting the number of antennas) ), The process proceeds to step S107, a weighting operation is performed (S107), and this process is terminated.

  Subsequently, n (number of repetitions) is compared with the number of antennas M to determine whether n is smaller than M (S103). If n is not smaller than M (if n ≧ M) as a result of the comparison determination, it is determined that the number of repetitions corresponding to the number of antennas has been completed, the process proceeds to step S107, and a weighting operation is performed (S107). This process is terminated.

  Subsequently, trace (L) n, which is a diagonal element of the L matrix of the Cholesky factor, is compared with a predetermined threshold value α, and it is determined whether or not trace (L) n is larger than the threshold value α (S104). As a result of the comparison determination, if trace (L) n is larger than the threshold value α, there is a high possibility that an error will occur in the matrix operation, so the value of trace (L) n is set to “0” (S105). That is, a matrix that is masked so that the matrix elements of L rows and L columns are set to “0” is generated (the number of antennas is limited), and the process proceeds to step S106. On the other hand, if trace (L) n is not greater than the threshold value, the process proceeds to step S106 without performing any processing.

  Then, “1” is added to the number of repetitions n until n ≧ M (S106), the process returns to step S103, and the processes of S103 to S106 are repeated.

  FIG. 3 is an explanatory diagram of matrix calculation in the array antenna control apparatus of the best mode for carrying out the present invention. This matrix calculation is executed in correlation calculation means (MxM Matrix Processing).

  FIG. 3A shows a matrix operation expression before masking the high level signal component. w is a reception weighting vector, x is a covariance matrix of the Cholesky factor, and y is a cross-correlation vector.

  In FIG. 3, the product of the covariance matrix (lower triangular matrix and upper triangular matrix) on the right side is calculated as the correlation between the signal intensity and the noise intensity in the correlation calculation means (MxM Matrix Processing). The product of the covariance matrix and the cross-correlation vector is calculated as a weighting operation in the reception control means (Rx Compensator).

  FIG. 3B shows a matrix operation expression after masking the high level signal component. The values in the fourth row and the fourth column are “0”, which is not used for matrix calculation and is masked.

  As described above, in the embodiment of the present invention, the received signal strength calculating means (Power Combiner) for calculating the signal strength of the signals received by the plurality of antenna elements, and the calculated signal strength and noise strength. Correlation calculation means (MxM Matrix Processing) for calculating correlation, reception control means (Rx Compensator) for weighting calculation for each antenna element, and logically changing the number of antenna elements when the reception level is high Since antenna number changing means (Array Position Controller) is provided, signal reception performance can be maintained and resources can be used effectively. Therefore, the reception state can be optimized and the communication quality can be improved. In addition, a certain communication quality can be maintained, and the data transmission performance can be improved.

  Moreover, since the number-of-antennas changing means suppresses the received signal from the antenna element that gives a large reception level and changes the number of antenna elements, it is possible to improve the calculation accuracy.

  In addition, a reception level adjusting means (Power Combiner) for adjusting the reception level is provided, and the antenna number changing means relatively compares the normalized received signals, selects an antenna element that gives a large reception level, and Since the number of antenna elements is changed, it is possible to easily recognize an antenna element having a large reception level and to suppress a reception signal by comparing the normalized signals relative to each other. As a result, the calculation accuracy can be improved.

  Further, a frequency compensation means (Frequency Estimator) for calculating a coefficient for compensating the frequency characteristics of the received signal, a time compensation means (Timing Estimator) for calculating a coefficient for compensating for a time axis shift of the received signal, A reception control means (Rx Compensator) for extracting a desired signal from the received signal by weighting the received signal using the coefficients calculated by the frequency compensation means and the time compensation means, so that time compensation and frequency compensation are provided. Therefore, the quality of the restored received signal can be improved.

  The correlation calculation means changes the number of antenna elements used to synthesize the received signal by changing the signal intensity and noise intensity matrix, so that the number of matrix calculation items can be reduced and the calculation load can be reduced. Can do.

[BRIEF DESCRIPTION OF THE DRAWINGS] It is a block diagram of the array antenna control apparatus of the best form for implementing this invention. It is a flowchart of the array antenna control apparatus of the best form for implementing this invention. It is explanatory drawing of the matrix calculation in the array antenna control apparatus of the best form for implementing this invention. It is a block diagram of the conventional array antenna control apparatus.

Explanation of symbols

Antenna: Antenna, RF Block: Radio unit, DDC: Digital downsampling converter, DUC: Digital upsampling converter, Path Control: Synthesis control means, DSP: Digital signal processor, Power combiner: Received signal strength calculation Means, reception level adjustment means, MxM Matrix Processing: correlation calculation means, Array Position Controller: antenna number changing means, Frequency Estimator: frequency compensation means, Timing Estimator: time compensation means, Rx Compensator: demodulation control means, Demodulation control means, Dex control means Physical to Logical: Logic circuit, Encoding Modulating means, Tx Burst Builder: transmitting signal combining means, Tx Parametor: transmission parameter generating means.

Claims (3)

In an array antenna control apparatus for controlling the directivity of an array antenna having a plurality of antenna elements,
Received signal strength calculating means for calculating the signal strength of the signal received by the antenna element;
When the signal strength calculated by the received signal strength calculating means is larger than a predetermined threshold, the antenna number changing means for suppressing the antenna elements giving a relatively large signal strength and changing the number of the antenna elements. When,
An array antenna control device comprising: Time compensation means for calculating a coefficient for compensating the time axis characteristic of the received signal in a state where the antenna elements are suppressed by the antenna number changing means, and a coefficient for compensating the frequency characteristic of the received signal A frequency compensation means for calculating
Receiving control means for extracting a desired signal from the received signal by weighting the received signal using a coefficient calculated by the time compensating means and the frequency compensating means; The array antenna control apparatus according to claim 1. An array antenna control method for controlling the directivity of an array antenna having a plurality of antenna elements,
Calculating the signal strength of the signal received by the antenna element;
And controlling to reduce the number of the antenna elements by suppressing antenna elements that give a relatively large signal strength when the calculated signal strength is larger than a predetermined threshold value. Array antenna control method.