JP2000134141A - Radio receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of the radio receiver employing the spatial division multiplex system by demultiplexing received signals in every incoming direction, based on a signal resulting from A/D-conversion a sum signal based on a signal synchronously with a period of orthogonal signals from an orthogonal signal generating means. SOLUTION: A received signal by antenna x1-x4 is given to weighting circuits 5-8 via frequency selection means 1-4 that select a desired frequency band signal. An antenna control signal generating means 10 receives weighted vectors Wa-Wc, which are used to make antenna beams coincide with each of received signals a-c received from different directions and direct a null point in an incoming direction of the other signals, modulate orthogonal signals Ca-Cc from an orthogonal signal generating means 19, outputs antenna control signals W1-W4 to the weighting circuits 5-8, where the received signals are weighted by the antenna control signals W1-W4. A signal combining means 15 combines the weighted signals, the sum signal is via an analog signal processing means 16 and an A/D converter 17 to an orthogonal signal demultiplexer means 18, where the orthogonal signals from the orthogonal signal generating means 19 via a delay circuit 20 are multiplied with the sum signal to extract low-frequency components and to demultiplex the received signals a-c in each arrived direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radio receiver using an adaptive array antenna, and more particularly to a radio receiver used for space division multiplex communication.

[0002]

2. Description of the Related Art As a radio receiver used for space division multiplex communication, one having a configuration as shown in FIGS. 5 and 6 is known. First, the wireless receiver shown in FIG. 5 will be described.
This radio receiver has a plurality of antenna elements x1, x2, x
3, x4. Individual antenna elements x1, x2, x
3, x4, a plurality of signals a, b, and c having different arrival directions from each other arrive and are received. The outputs of the individual antenna elements x1, x2, x3, and x4 are input to analog signal processing means 61 that performs signal amplification, frequency conversion, channel selection, and the like. Each analog signal processing means 6
The outputs of 1 are analog-to-digital converters (hereinafter, referred to as
ADC) 62 converts it into a digital signal,
Each of the converted digital signals is subjected to phase and amplitude weighting in the digital signal processing unit 63 and then combined. Thereby, the signals a, b, and c in the respective directions of arrival are obtained.
Are separated.

A signal Sa = [sa1, sa2, sa3, sa] in which signals arriving in three directions a, b and c excite the respective antenna elements X1, X2, X3 and X4.
4] ^T , Sb = [sb1, sb2, sb3, sb
4] ^T , Sc = [sc1, sc2, sc3, sc4] ^T
Then, the antenna output X is X = [x1, x2, x3,
x4] ^T = Sa + Sb + Sc When a predetermined weighting vector W = [w1, w2, w3, w4] is added to each received signal in the digital signal processing unit 43,
The weighted signal y can be expressed as y = WX. Here, if a value that satisfies WaSb = 0 and WaSc = 0 is selected as the weighting vector Wa in order to receive the signal a,
y = Wa {Sa + Sb + Sc} = WaSa, the incoming signals b and c are not output, and only the incoming signal a is output.

In this example, there are four antennas and two unnecessary signals, so that WaSb = 0 and WaSc = 0 are satisfied.
Are plural and not unique, but a Wa that maximizes the desired signal a is selected. At this time, the main lobe of the beam pattern of the antenna is directed to the arrival direction of the signal a. Similarly, b
Only the weight vector that outputs only c can be Wb and Wc, and can be output separately from other signals.

In a radio receiver having another configuration shown in FIG. 6, signals a, b and c having different directions of arrival received by a plurality of antenna elements x1, x2, x3 and x4 are respectively subjected to frequency separation. The signal is frequency-divided by means 71 and transmitted to a plurality of signal processing units 72. In each signal processing unit 72, each signal input from each frequency separation unit 71 is weighted by a weight vector Wa and synthesized,
The signal is input to an analog signal processing unit 73 that performs signal amplification, frequency conversion, channel selection, and the like. Then, the output of each analog signal processing means 73 is converted into a digital signal by an analog / digital converter (ADC) 74, and signals a, b, and c in the respective incoming directions are separated.

[0006]

In each of the above radio receivers, even when the signal received by each antenna element is smaller than the noise level, the result of the weighted combination satisfies the required signal-to-noise power ratio. Something like that. Therefore, the ADC in the radio receiver shown in FIG. 5 must be able to convert a signal smaller than the noise level into a digital signal, and is required to have a higher resolution. In the radio receiver shown in FIG. 5, expensive ADCs having such a high resolution are required for the number of antenna elements.
For this reason, there is a problem that the cost of the wireless receiver is increased.

On the other hand, in the radio receiver shown in FIG. 6, it is necessary to provide circuits such as weighting circuits and ADCs independently for the number of multiplexed signals, which also necessitates many expensive ADCs having high resolution. Therefore, the overall cost increases.

The present invention has been made to solve such a problem. A weighting circuit for weighting a received signal and an expensive A / D converter having a high resolution for A / D converting the received signal are provided.
An object of the present invention is to provide an inexpensive radio receiver of the space division multiplex system by reducing the number of D converters.

[0009]

In order to achieve the above object, a radio receiver according to the present invention comprises a plurality of antenna elements for receiving a plurality of signals having different directions of arrival, and a plurality of antenna elements for receiving a plurality of signals from the respective antenna elements. Frequency selecting means for selecting and outputting a signal of a predetermined frequency band from each signal, orthogonal signal generating means for generating a plurality of periodic orthogonal signals orthogonal to each other, and a signal selected by the frequency selecting means. Weight signal modulating means for modulating, by the quadrature signal, a weight signal to be given to a received signal for each antenna element; and a weight modulation signal output from the weight signal modulating means, wherein each of the antennas selected by the frequency selecting means Weighting means for weighting the received signal of each element, and receiving signals weighted by the weighting means. Synthesizing means, an A / D converting means for A / D converting the synthesized signal, and a signal synchronized with a cycle of an orthogonal signal generated by the orthogonal signal generating means from an output signal of the A / D converting means. Separating means for separating the received signal for each direction of arrival based on the received signal.

[0010] Signals a, b, and c having different directions of arrival are signals that excite the respective antenna elements by a vector Sa =
[Sa1, sa2, sa3, sa4] ^T , Sb = [sb
1, sb2, sb3, sb4] ^T , Sc = [sc1, s
c2, sc3, sc4] ^T , the output X of the antenna element is X = [x1, x2, x3, x4] ^T = Sa + Sb
+ Sc. When the weight vector W given to the output X of each antenna element is represented by W = [w1, w2, w3, w4], the weighted signal y can be represented by y = WX. When a value satisfying WaSb = 0 and WaSc = 0 is selected as Wa, y = Wa {Sa + Sb + Sc} = W
aSa, the incoming signals b and c are not output and the incoming signal a
Only received. Similarly, only the incoming signal a, the incoming signal b
Weighting vectors that output only the signals can be expressed as Wb and Wc. However, depending on the number of antenna elements and the number of received signals, these weighting vectors Wa, Wb, and Wc may not be unique, but in that case, a value that maximizes the desired signal is selected.

Each weight vector is multiplied by a periodic orthogonal signal Ca, Cb, Cc orthogonal to each other. Here, that the orthogonal signal Ca (t) and the orthogonal signal Cb (t) are orthogonal to each other means that the result of integrating the product of the orthogonal signal Ca (t) and the orthogonal signal Cb (t) for a certain period of time becomes zero. W
= WaC + WbCb + WcCc multiplied by the antenna output X, the signal y after weighting becomes y = WX = WaSaC
a + WbSbCb + WcScCc.

The weighted signal y is converted into a digital signal by A / D conversion means, multiplied by the quadrature signal Ca, and integrated for a certain period of time to obtain yCa = WXCa = WaSaCaCa
+ WbSbCbCa + WcScCcCa, so Wa
Only Sa can be taken out. Similarly, the orthogonal signal Cb,
By multiplying and integrating Cc, WbSb and WcSc can be respectively extracted.

However, since the signal y after weighting passes through a circuit as A / D conversion means and other circuits, the signal y is subjected to signal delay by these circuits. Therefore, it is necessary to synchronize the respective signals by, for example, delaying the orthogonal signal by which the weighted signal y is multiplied. It should be noted that the integration over a certain period of time can be approximated by passing the signal through a low-pass filter. In order that the information of the desired signal is not lost in the low-pass filter, the frequency component of the desired signal needs to be within the pass band. That is, since it is necessary to separate the signals by a low-pass filter having a pass band through which the desired signal can pass, the period of the orthogonal signals Ca, Cb, and Cc is compared with the code interval (reciprocal of the code rate) of the desired signal. Must be shorter.

According to the radio receiver of the present invention, a circuit for weighting a received signal only requires the number of antenna elements, and an expensive A / D converter having a high resolution for A / D converting the received signal. Only one. When the weight signal is generated digitally, the increase in the number of multiplexes can be handled by changing the software. Therefore, a space-division multiplex wireless receiver can be provided at low cost.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a radio receiver according to a first embodiment of the present invention.

This radio receiver has a plurality of antenna elements x1, x2 for receiving a plurality of signals a, b, c having different directions of arrival.
x2, x3, and x4. Each antenna element x1, x
2, x3, and x4 are frequency selecting means 1, 2, 2, and 3, respectively, for selecting a signal in a desired frequency band.
The signals are input to the corresponding weighting circuits 5, 6, 7 and 8 through the circuits 3 and 4.

Each of the weighting circuits 5, 6, 7, 8 respectively converts the received signal selected by the corresponding frequency selecting means 1, 2, 3, 4 into an antenna control signal W1, generated by the antenna control signal generating means 10. Weighting is performed according to W2, W3, and W4 (modulated weighting vectors).

The antenna control signal generating means 10 matches the beam of the antenna with the arrival direction of the received signal for each of the weighting vectors set in advance, that is, for each of the received signals a, b, and c having different arrival directions. Weighting vectors Wa, Wb, which point the null point in the signal arrival direction,
The antenna control signals W1, W2, W3, and W4 (modulated weighting vectors) are generated by inputting Wc and modulating the input signals with the orthogonal signals Ca, Cb, and Cc generated by the orthogonal signal generating means 19, The signals are transmitted to the weighting circuits 5, 6, 7, and 8, respectively. The antenna control signal generating means 10 outputs, for example, a weight vector W
a, Wb, and Wc are multiplied by quadrature signals Ca, Cb, and Cc, and the number of antenna control signal generating circuits 11, 12, and 13 and 14.

Each of the received signals weighted by each of the weighting circuits 5, 6, 7, and 8 is added to a signal combining means (adder) 15
And then input to the analog signal processing means 16. The analog signal processing means 16 performs amplification, frequency conversion, channel selection, and the like on the synthesized signal, and inputs the result to an analog / digital converter (hereinafter, referred to as ACD) 17. The ACD 17 converts the output signal of the analog signal processing unit 16 into a digital signal and outputs the digital signal to the orthogonal signal separation unit 18.

The orthogonal signal separating means 18 multiplies the output of the ACD 17 by the orthogonal signal input from the orthogonal signal generating means 19 via the delay means 20, and extracts a low-frequency component from the signal resulting from the multiplication. It separates and outputs the received signals a, b, and c for each direction of arrival.

Next, the operation of the radio receiver according to the present embodiment will be described with reference to FIG.

FIG. 2 shows signal waveforms at various parts of the radio receiver when a signal in which values of 0 and 1 change as an orthogonal signal is used. However, the same signal waveform diagram schematically shows a change in the envelope of the high-frequency signal.

The antenna elements x1, x2, x3, x4 are:
For example, as shown in FIG.
Consider the case where two signals a, b and c arrive. In this case, for example, a signal having an envelope as shown in FIG. 2B is obtained as the output of the antenna elements x1, x2, x3, x4.

On the other hand, the orthogonal signal generator 19 generates orthogonal signals Ca, Cb and Cc as shown in FIG. 2C for each of the received signals a, b and c having different arrival directions. You. The orthogonal signal Ca is a repetition signal of 1,0,0, the orthogonal signal Cb is a repetition signal of 0,1,0, and the orthogonal signal Cb is a repetition signal of 0,0,1. Here, since the products of the orthogonal signals Ca and Cb are 0, they are orthogonal to each other. Similarly, the orthogonal signals Ca and Cc are orthogonal to each other, and the orthogonal signals Cb and Cc are also orthogonal to each other.

The antenna control signal generating means 10 matches predetermined antenna weight vectors Wa, Wb, Wc (that is, for each of the received signals a, b, c, the beam of the antenna with the arrival direction of the signal, and other signals). By inputting a weighting vector that directs a null point in the direction of arrival of the signal) and by switching it with each of the orthogonal signals Ca, Cb, and Cc, a modulated antenna such as that shown in FIG. It generates control signals W1, W2, W3, and W4.

However, the periods of the orthogonal signals Ca, Cb, Cc and the antenna control signals W1, W2, W3, W4 modulated by the orthogonal signals Ca, Cb, Cc are the periods of the changes of the received signals a, b, c. Should be short enough.

Each of the weighting circuits 5, 6, 7, and 8 respectively outputs the signals from the frequency selecting means 1, 2, 3, and 4 shown in FIG.
The received signals as shown in FIG. 2B are converted into the antenna control signals W1 and W given by the antenna control signal generating means 10.
2, W3, and W4. Note that the weighting method to be performed at this time includes a method of controlling only the phase of the signal and a method of controlling both the amplitude and the phase of the signal. It is shown schematically.

As shown in FIG. 2E, the outputs from the weighting circuits 5, 6, 7, and 8 are pulse trains whose amplitude (or the phase of the carrier wave) changes at the period of the orthogonal signals Ca, Cb, and Cc. Becomes Each pulse is a mixture of the received signals a, b, and c in each arrival direction, as shown in FIG. The outputs of the weighting circuits 5, 6, 7, and 8 are combined in a signal combining unit 15. As a result of this signal synthesis, as shown in FIG.
5, the signal a at the timing when the orthogonal signal Ca becomes 1
However, the signal b is output when the orthogonal signal Cb becomes 1 and the signal c is output when the orthogonal signal Cc becomes 1.

The above operation corresponds to converting the space division multiplexed signal to the time division multiplexed signal by switching the beam direction of the antenna at the cycle of the orthogonal signals Ca, Cb, Cc. In the time division method, when the signal a in a certain direction of arrival is received, the signals b and c in the other directions of arrival are not received, but the quadrature signal is generated at a frequency higher than the occupied frequency band of the received signal (thus a shorter period). When repeated, the number of samples per time increases, and signals a, b, and c in substantially all incoming directions can be received simultaneously.

The combined signals are orthogonal signals Ca, Cb, C
Since it is a time-division multiplexed signal switched at a period of c, the received signal can be separated by opening and closing the gate with a signal synchronized with the orthogonal signals Ca, Cb, and Cc.

FIG. 3 shows an example of the configuration of the orthogonal signal separating means 18 adopting the signal separating method by opening and closing the gate.
In the orthogonal signal separating means 18, the orthogonal signals Ca, Cb, and Cc delayed and output from the delay means 20 are output by the sequential circuit 3.
The received signal is separated by outputting the signal to the gate 32 as a gate opening / closing signal via 1. The orthogonal signal Ca,
Since Cb and Cc are 0 or 1, these orthogonal signals C
Opening and closing the gate 31 by a, Cb, and Cc is equivalent to multiplication of signals. The separated signals are equivalent to pulse trains obtained by sampling the received signals a, b, and c, respectively. When this pulse train is passed through a low-pass filter, the original signal can be restored.

As described above, the space division multiplexed signal is converted into the time division multiplexed signal and demodulated as the time division multiplexed signal in the receiver, so that the space division multiplexed signal can be separated. Thus, the high-frequency analog circuit can be simplified, and a cheaper radio receiver can be realized.

Incidentally, signals having different frequencies can be used as the orthogonal signals Ca, Cb, Cc. For example, by allocating a frequency of 1 MHz to the received signal a, 2 MHz to the received signal b, and 3 MHz to the received signal c, the spatial multiplexed signal is converted into a frequency multiplexed signal. The frequency multiplexed signal is synchronously detected by the orthogonal signal separating means 18 using the orthogonal signal delayed by the delay means 20, so that signals a, b, and c for each direction of arrival are separated. Note that the orthogonal signals Ca, Cb, and Cc need not be sine waves, but may be approximated by, for example, square waves.

Further, pseudo random numbers can be used as the orthogonal signals Ca, Cb, Cc. In this case, the space division signal is converted into a code division multiplex signal.

The weighting can be performed with the frequency of the received signal, but the weighting can also be performed after the received signal is once converted to the intermediate frequency. In this case, an image removal filter, a frequency conversion circuit, and the like are required for each antenna element. An accurate weighting circuit can be realized.

When only the beam direction is controlled and the null point is not controlled, a phase shift circuit can be used as a weighting circuit. In this case, the cost can be further reduced because no variable gain circuit is required.

In time division multiplex communication used for wireless communication, it is usual that the slot is longer than the code interval of the transmission signal. For example, 256 symbols are transmitted per slot. When such time division multiplexing communication and space division multiplexing communication are used together, for example, if 16 slots are assigned per symbol and the time division slot inside the receiver is made shorter than one symbol, both multiplexing systems can be used together.

FIG. 4 shows an example of a radio receiver using both space division multiplexing and frequency division multiplexing.

In this radio receiver, each signal received by a plurality of antenna elements x1, x2, x3, x4 is divided on the frequency axis by frequency separation means 41, 42, 43, 44, respectively, and The weighting circuits 48 in the signal processing circuits 45, 46, 47 provided in accordance with the number
49, 50 and 51 respectively. Subsequent operations are the same as those of the wireless receiver of the embodiment shown in FIG.
That is, each of the weighting circuits 48, 49, 50, and 51 respectively converts the input received signal into an antenna control signal W1, W2, W generated by the antenna control signal generating means 52.
3, weighting according to W4 (modulated weighting vector). The signals weighted by the respective weighting circuits 48, 49, 50, 51 are combined by a signal combining unit 53 and then input to an analog signal processing unit 54.
The analog signal processing means 54 amplifies the synthesized signal,
Frequency conversion, channel selection, and the like are performed, and the results are input to an analog / digital converter (ACD) 55. ACD
55 converts the output signal of the analog signal processing means 54 into a digital signal and outputs the digital signal to the orthogonal signal separation means 56. The orthogonal signal separating means 56 outputs the orthogonal signals Ca, Cb, Cc inputted from the orthogonal signal generating means 58 through the delay means 57.
Is multiplied by the output signal of the ACD 55, a low-frequency component is extracted from the signal resulting from the multiplication, and the signals a, b, and
Separate and output c.

[0041]

As described above, according to the radio receiver of the present invention, a circuit for weighting a received signal requires only the number of antenna elements and has a high resolution for A / D converting the received signal. Only one expensive A / D converter is required. Therefore, a space-division multiplex wireless receiver can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a wireless receiver according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an operation of the wireless receiver in FIG. 1;

FIG. 3 is a diagram illustrating a configuration example of a quadrature signal separation unit.

FIG. 4 is a diagram illustrating a configuration of a wireless receiver using a space division multiplexing system and a frequency division multiplexing system according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration of a conventional wireless receiver.

FIG. 6 is a diagram illustrating a configuration of another conventional wireless receiver.

[Explanation of symbols]

 x1, x2, x3, x4 Antenna elements 1, 2, 3, 4 Frequency selection means 5, 6, 7, 8 Weighting circuit 10 Antenna control signal generation means 11, 12, 13, 14 Antenna control signal generation circuit 16 Analog signal processing Means 17 Analog / digital converter (ACD) 18 Quadrature signal separation means 19 Quadrature signal generation means 20 Delay means

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasushi Murakami 1-term, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in the Toshiba R & D Center (reference) 5K052 AA14 BB02 BB15 BB21 CC04 CC06 DD03 EE19 EE38 EE40 FF05 GG31 GG32 GG41 GG48 5K059 BB01 CC03 CC04 CC09 DD32 DD37 DD39 EE02

Claims (5)

[Claims] 1. A plurality of antenna elements for receiving a plurality of signals having different directions of arrival, respectively, and a frequency selection for selecting and outputting a signal of a predetermined frequency band from each signal received by each of the antenna elements. Means, orthogonal signal generating means for generating a plurality of periodic orthogonal signals orthogonal to each other, and a weighting signal to be given to a reception signal for each antenna element selected by the frequency selection means, respectively, is modulated by the orthogonal signal. Weight signal modulation means, and a weight modulation signal output from the weight signal modulation means,
Weighting means for weighting the reception signal for each antenna element selected by the frequency selection means; synthesis means for synthesizing the reception signals weighted by the weighting means; and A / D conversion of the synthesized signal A / D conversion means, and separation means for separating the received signal for each direction of arrival from an output signal of the A / D conversion means based on a signal synchronized with a cycle of the orthogonal signal generated by the orthogonal signal generation means. And a wireless receiver. 2. A plurality of antenna elements for receiving a plurality of frequency division multiplex signals each having a different direction of arrival, and frequency separation for separating each frequency division multiplex signal received by each antenna element into a desired frequency band. Means, orthogonal signal generating means for generating a plurality of periodic orthogonal signals orthogonal to each other, and a weighting signal to be given to a reception signal for each antenna element separated by the frequency separation means, respectively, is modulated by the orthogonal signal. Weight signal modulation means, and a weight modulation signal output from the weight signal modulation means,
Weighting means for weighting the received signals for each antenna element separated by the frequency separating means; combining means for combining the received signals weighted by the weighting means; and A / D conversion of the combined signal A / D conversion means, and separation means for separating the received signal for each direction of arrival from an output signal of the A / D conversion means based on a signal synchronized with a cycle of the orthogonal signal generated by the orthogonal signal generation means. And a wireless receiver. 3. The radio receiver according to claim 1, wherein the orthogonal signal is a signal having values of 0 and 1. 4. The radio receiver according to claim 1, wherein the quadrature signal is a sine wave having a different frequency. 5. The radio receiver according to claim 1, wherein the orthogonal signal is a pseudo random number.