JP2007006219A - Adaptive antenna device - Google Patents

Abstract

An adaptive antenna device that performs interference cancellation before performing fast Fourier transform and realizes synthesis of a desired signal for each subcarrier to obtain frequency diversity gain.
An interference extraction unit that extracts an interference signal component based on a plurality of reception signals of an array antenna, and a plurality of interference signal components extracted by the interference extraction unit from each of the plurality of reception signals are removed. 1 is provided with an interference canceling unit 30 that generates a plurality of interference cancellation signals corresponding to the received signal and a combining unit 40 that combines the plurality of interference cancellation signals generated by the interference cancellation unit 30.

Description

  The present invention relates to an adaptive antenna device, and more particularly to an adaptive antenna device applied to a multicarrier communication system.

  There is multi-carrier transmission as a high-speed data transmission system. In particular, OFDM (Orthogonal Frequency Division Multiplexing) in which subcarriers are arranged at orthogonal frequency intervals is employed in many wireless systems such as wireless LANs and terrestrial digital broadcasting.

  In multi-carrier transmission such as OFDM, it is well known that waveform distortion due to a delayed wave can be reduced by inserting a guard interval. However, characteristics are significantly deteriorated for a delayed wave exceeding the guard interval.

  Therefore, application of an adaptive antenna that spatially removes these using an array antenna has been studied. As a method for realizing an adaptive antenna for OFDM, mainly a method of performing interference removal before FFT (Fast Fourier Transform) (see, for example, Patent Document 1), and performing interference removal for each subcarrier after FFT. There is a method (for example, see Non-Patent Document 1).

Japanese Patent Laid-Open No. 11-312991 (first page, FIG. 1) Imai, Ogawa, Ogane, “Study on Adaptive Array in OFDM Communication Systems” IEICE Tech. AP2001-115, 2001

  However, the prior art has the following problems. In the conventional technique described above, the former method synthesizes the reception signals of the respective antenna elements before the FFT, so that there is a problem that diversity combining in the frequency domain cannot be performed for each subcarrier. The latter method has a problem that the amount of calculation increases in proportion to the increase in the number of subcarriers, although the delayed wave within the guard interval can be successfully captured by the synthesis processing for each subcarrier.

  The present invention has been made to solve the above-described problems, and obtains an adaptive antenna apparatus that performs interference cancellation before FFT and realizes synthesis of desired signals for each subcarrier in order to obtain frequency diversity gain. For the purpose.

  An adaptive antenna apparatus according to the present invention includes an interference extraction unit that extracts an interference signal component based on a plurality of reception signals of an array antenna, and an interference signal component extracted by the interference extraction unit from each of the plurality of reception signals. The apparatus includes an interference removal unit that generates a plurality of interference removal signals corresponding to the plurality of received signals, and a synthesis unit that combines the plurality of interference removal signals generated by the interference removal unit.

  According to the present invention, interference signal components are extracted based on a plurality of received signals, a plurality of interference removal signals are generated by removing the interference signal components from the respective received signals, and a plurality of interferences corresponding to the plurality of received signals are generated. By enabling the removal signal to be combined, it is possible to obtain an adaptive antenna apparatus that can perform interference removal before FFT and can combine desired signals for each subcarrier in order to obtain frequency diversity gain.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an adaptive antenna device of the invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of an adaptive antenna device according to Embodiment 1 of the present invention. In addition, in each figure, the same code | symbol shows the same or an equivalent part. The adaptive antenna apparatus includes an array antenna 10, an interference extraction unit 20, an interference removal unit 30, and a synthesis unit 40.

  FIG. 1 shows a configuration with four elements, and the array antenna 10 includes four antenna elements # 1 to # 4. The number of elements is not limited to this, and the same applies to any number of elements.

  The interference extraction unit 20 performs a process of extracting an interference signal component based on a plurality of reception signals of the array antenna 10. The interference removal unit 30 generates a plurality of interference removal signals corresponding to the plurality of reception signals by performing processing for removing the extracted interference signal component from each of the plurality of reception signals. Furthermore, the synthesis unit 40 synthesizes a plurality of interference removal signals generated by the plurality of interference removal units 30.

  Next, the operation of the adaptive antenna device according to the first embodiment will be described with reference to the drawings. The reception signals of each antenna element of the array antenna 10 are distributed by the number of elements and input to the interference extraction unit 20. FIG. 1 illustrates the case where N = 4 received signals are used. The interference extraction unit 20 performs a process of extracting only the interference signal component included in the received signal.

  FIG. 2 is a diagram illustrating a configuration example of the interference extraction unit 20 according to Embodiment 1 of the present invention, and includes a weighting unit 21 and a combiner 22. The weighting unit 21 has a function of multiplying the reception signal input to the interference extraction unit 20 by a complex weighting factor that controls amplitude and phase. Thereafter, a signal whose amplitude and phase are adjusted by the combiner 22 is combined. As a method for calculating the weighting factor, for example, a known signal such as a pilot symbol may be used, or a waveform periodically inserted into a transmission signal such as a guard interval may be used.

  If sufficient performance cannot be obtained with a degree of freedom corresponding to the number of elements, such as a broadband interference signal or a large number of incoming waves, the configuration of the interference extraction unit 20 is a tap corresponding to a delay line filter. It is effective to use an attached delay line configuration. FIG. 3 is a configuration diagram of the interference extraction unit 20 having the tapped delay line configuration according to the first embodiment of the present invention.

  The interference extraction unit 20 in FIG. 3 includes a weighting unit 21, a combiner 22, and a delay unit 23. Here, the weighting unit 21 and the combiner 22 have the same functions as those described with reference to FIG. The delay unit 23 is a delay element that gives a fixed time delay, and the configuration of FIG. 3 operates as a composite filter in the space domain and the time domain. Note that the number of the delay devices 23 can be arbitrary, and is not limited to the figure.

  Next, the interference removal unit 30 performs a process of removing the interference signal component that is the output of the interference extraction unit 20 from the reception signal, and generates a plurality of interference removal signals corresponding to the plurality of reception signals. FIG. 4 is a diagram illustrating a configuration example of the interference removal unit 30 according to the first embodiment of the present invention, and includes a weighting unit 31 and a subtracter 32. The received signal of each antenna element that is an input to the interference removing unit 30 includes an interference signal component in addition to the desired signal. Therefore, even if demodulation is performed as it is, it is difficult to restore the original information.

  Accordingly, the interference removal unit 30 controls the amplitude / phase of the interference signal component obtained by the interference extraction unit 20 by the weighting unit 31 so as to match the interference signal component included in the received signal. As a result, the subtracter 32 performs a subtraction process on both, thereby generating an interference removal signal obtained by removing the interference signal component from the reception signal of the antenna element. The interference cancellation unit 30 generates N interference cancellation signals corresponding to each of the reception signals of the N antenna elements, and outputs the N interference cancellation signals to the synthesis unit 40.

  Here, when the amplitude / phase of the weighting unit 31 is controlled so that the phase of the interference signal component obtained from the interference extraction unit 20 is opposite in phase to the interference signal included in the reception signal by 180 degrees. The subtracter 32 can be replaced with the combiner 22 shown in FIG.

  Note that, as described in the explanation of the interference extraction unit 20, in order to cope with a wideband signal or the like, the interference removal unit 30 can also have a tapped delay line configuration corresponding to a delay line filter. FIG. 5 is a configuration diagram of the interference canceller 30 having the tapped delay line configuration according to the first embodiment of the present invention. In FIG. 5, both the reception signal side and the interference signal component side have a tapped delay line configuration, but only one of them may have a tapped delay line configuration. Further, the number of both delay units 33 may be different.

  Next, combining section 40 combines the interference cancellation signals corresponding to the plurality of received signals from interference cancellation section 30 to improve the SNR (Signal to Noise Ratio). FIG. 6 is a specific configuration diagram of the synthesis unit 40 according to the first embodiment of the present invention. The synthesizer 40 includes a serial / parallel converter 41, an FFT converter 42, a weighting unit 43, a synthesizer 44, a demodulator 45, and a parallel / serial converter 46.

  OFDM, which is multicarrier transmission, enables high-speed transmission by assigning different data to subcarriers having different frequencies. Therefore, the receiver needs a function of a demultiplexer that separates each subcarrier. In FIG. 6, the function is realized by the series-parallel converter 41 and the FFT converter 42.

  The serial / parallel converter 41 has a function of cutting out data of a certain length, and performs FFT window control. Next, the FFT converter 42 performs frequency conversion by performing FFT on the cut-out data, and cuts each subcarrier data in the orthogonal frequency arrangement.

  In FIG. 6, the output of each FFT converter 42 shows four cases, but in an actual system, the output has a size of tens to thousands. The weighting unit 43 calculates a weighting factor for each of these subcarriers to control the amplitude and phase, and the synthesizer 44 synthesizes each subcarrier data whose amplitude and phase are controlled.

  In this way, by performing a combining process based on a plurality of interference removal signals corresponding to a plurality of received signals, the combining unit 40 can optimally combine a desired signal for each subcarrier data, and in the frequency domain Diversity gain is obtained. Thereafter, each subcarrier data is subjected to demodulation processing including error correction in the demodulator 45, and then the original information sequence is restored by the parallel-serial converter 46.

  As the operation of the weighting unit 43 in the combining unit 40, since the interference removal signal from which the interference signal has already been removed is combined, it is only necessary to perform diversity control for combining the desired signals with the maximum ratio. Therefore, in the receiver according to the first embodiment, the combining unit 40 can be replaced with an existing diversity receiver, and can be practically used by newly adding the interference extracting unit 20 and the interference removing unit 30. .

  As described above, according to the first embodiment, it is possible to obtain an interference cancellation signal corresponding to a plurality of reception signals by using only the configuration of performing interference cancellation before FFT, and using the interference cancellation signal. Thus, it is possible to perform diversity combining for each subcarrier after FFT. In addition, as described above, there is a feature that the compatibility with the existing diversity receiver is also good.

Embodiment 2. FIG.
FIG. 7 is a configuration diagram of the adaptive antenna device according to the second embodiment of the present invention. In addition, in each figure, the same code | symbol shows the same or an equivalent part. This adaptive antenna apparatus includes an array antenna 10, an interference extraction unit 20, an interference removal unit 30, and a synthesis unit 40, similarly to the configuration of FIG.

  In the first embodiment, the reception signals of all the antenna elements are input to the respective interference extraction units 20. However, in the second embodiment, reception of the antenna elements that are input signals to the interference removal unit 30 is performed. The difference is that a signal other than the signal is input to each interference extraction unit 20.

  Specifically, in FIG. 7, when four interference signal components are generated based on the reception signals of four antenna elements, each of the four interference extraction units 20 is nth (n is 1). The nth interference signal component is extracted using three received signals other than the received signal (integer of 4 to 4).

  On the other hand, when the four interference cancellation units 30 generate four interference cancellation signals, the nth interference signals extracted by the respective interference extraction units 20 from the nth reception signal. The nth interference cancellation signal is generated by removing the component.

  With this configuration, the interference removal unit 30 can generate an interference removal signal by removing an interference signal component generated based on reception signals of different antenna elements. As a result, the desired signal can be generated. Can be reduced, and the correlation between the interference cancellation signals captured by the synthesizer 40 can be reduced. Also, the amount of calculation is reduced.

  According to the second embodiment, interference obtained corresponding to a plurality of reception signals is generated by generating an interference cancellation signal by removing an interference cancellation component extracted from a reception signal other than its own reception signal from its own reception signal. The possibility that the desired signal is suppressed from the cancellation signal can be reduced, and the correlation of each interference cancellation signal can be reduced.

  In the above-described embodiment, the interference removing unit 30 is prepared for the reception signals of all the antenna elements. However, the antenna elements having a poor reception state (such as low reception power and high interference level). It is possible to use a configuration that is not used. Further, as an input to the interference removal unit 30, a signal with improved SNR may be used by arranging beam forming means such as a BFN (Beam forming Network) instead of the reception signal of the antenna element. Good.

It is a block diagram of the adaptive antenna apparatus in Embodiment 1 of this invention. It is the figure which showed the structural example of the interference extraction part in Embodiment 1 of this invention. It is a block diagram of the interference extraction part provided with the delay line structure with a tap in Embodiment 1 of this invention. It is the figure which showed the structural example of the interference removal part in Embodiment 1 of this invention. It is a block diagram of the interference removal part provided with the delay line structure with a tap in Embodiment 1 of this invention. It is a specific block diagram of the combiner | synthesizer in Embodiment 1 of this invention. It is a block diagram of the adaptive antenna apparatus in Embodiment 2 of this invention.

Explanation of symbols

  10 array antennas, 20 interference extraction units, 21 weighting units, 22 combiners, 23 delay units, 30 interference cancellation units, 31 weighting units, 32 subtractors, 33 delay units, 40 combining units, 41 series-parallel converters, 42 conversions , 43 weighting unit, 45 demodulator, 46 parallel-serial converter.

Claims (10)

An interference extraction unit for extracting interference signal components based on a plurality of received signals of the array antenna;
An interference removal unit that generates a plurality of interference removal signals corresponding to the plurality of reception signals by removing the interference signal component extracted by the interference extraction unit from each of the plurality of reception signals;
An adaptive antenna apparatus comprising: a combining unit that combines the plurality of interference cancellation signals generated by the interference cancellation unit. The adaptive antenna device according to claim 1,
The interference extraction unit extracts the interference signal component by combining a plurality of reception signals of the array antenna. The adaptive antenna device according to claim 1 or 2,
The interference removal unit generates an interference removal signal corresponding to the reception signal of the arbitrary antenna element by removing the interference signal component from the reception signal of the arbitrary antenna element. . In the adaptive antenna device according to any one of claims 1 to 3,
The said interference removal part produces | generates the interference removal signal corresponding to the received signal of all the antenna elements by removing the said interference signal component from each of the received signal of all the antenna elements, The adaptive antenna apparatus characterized by the above-mentioned. In the adaptive antenna device according to any one of claims 1 to 4,
When the interference extraction unit generates N interference signal components based on reception signals of N antenna elements (N is an integer equal to or greater than 3), the n th (n is an integer from 1 to N) Extracting the nth interference signal component using N−1 received signals other than the received signal,
The interference cancellation unit generates the nth interference cancellation signal by removing the nth interference signal component from the nth received signal when generating N interference cancellation signals. A characteristic adaptive antenna device. In the adaptive antenna device according to any one of claims 1 to 4,
The interference extraction unit extracts one interference signal component using reception signals of N antenna elements (N is an integer of 3 or more),
The adaptive antenna apparatus, wherein the interference cancellation unit generates N interference cancellation signals by removing the one interference signal component from each of the reception signals of the N antenna elements. In the adaptive antenna device according to any one of claims 1 to 6,
The said interference extraction part has a delay line filter, and extracts an interference signal component based on each received signal after passing through the said delay line filter, The adaptive antenna apparatus characterized by the above-mentioned. The adaptive antenna device according to any one of claims 1 to 7,
The interference removal unit includes a delay line filter, and generates a plurality of interference removal signals by removing an interference signal component after passing through the delay line filter from each of the received signals after passing through the delay line filter. An adaptive antenna device characterized by the above.   The adaptive antenna device according to any one of claims 1 to 8, wherein the adaptive antenna device is applied to a radio receiver used in a multicarrier transmission system. The adaptive antenna device according to claim 9,
The said combining part isolate | separates into the subcarrier from which a frequency differs, respectively by carrying out the Fourier transform of the some interference removal signal produced | generated by the said interference removal part, The adaptive antenna apparatus characterized by the above-mentioned.

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