JPH02149022A - Adaptive antenna system - Google Patents

Abstract

PURPOSE:To improve communication quality independently of relation between desired signal power and disturbing wave power by providing a synchronization circuit and a control circuit to establish synchronism with a reception signal, and controlling the operation of an adaptive antenna according especially to the synchronizing state of spread spectrum communication. CONSTITUTION:The synchronization circuit 7 is connected to the output terminal of a synthesizer 4, and the synchronizing signal of the spread spectrum communication is extracted by this synchronization circuit 7. The control circuit 6 generates the control signal of a switch 3 according to the binary information of the synchronization circuit 7. Then, when the synchronism is not established, the ON/OFF operation of the switch 3 is repeated at time intervals over twice longer than the time to establish the synchronism. On the other hand, when the synchronism is established, this repeating operation is stopped, and the ON/OFF state of the control signal at this moment is selected, and this state of the control signal is held during this period. Accordingly, the loss of the desired signal can be avoided, and SINR can be improved.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention is directed to automatically orient an antenna in a spread spectrum communication system even if the arrival direction of interference waves is unknown. The present invention relates to an adaptive antenna device that can form a zero point of signal strength, suppress the interference waves, and improve communication quality.

(Prior Art) As the radio wave environment becomes more complex, adaptive antenna devices that automatically remove interference waves mixed into a desired communication band are attracting attention. Adaptive antenna equipment is a spatial adaptation that eliminates interference waves by learning the surrounding radio wave environment and automatically forming the zero point of antenna directivity in that direction, even if the direction of arrival of interference waves is unknown. It's a filter.

On the other hand, spread spectrum communication spreads the information signal using a certain predetermined code, for example, a PN code (Direct 5e
(hereinafter abbreviated as DS0) shift, hopping (Frequency) in which the RF frequency conforms to the above code.
This is a communication method that uses a band wider than the information band and has improved anti-jamming properties by flopping (hereinafter abbreviated as FH).

When the above-mentioned adaptive antenna device is applied to a communication system using a spread spectrum communication system, the interference suppression performance of both can be used synergistically, and a communication system with better anti-jamming performance can be constructed. Regarding the operation of the adaptive antenna device under such a spread spectrum communication system, for example, r R, T, Compto
n, “The Power Inversion ar
ry: Concept and Perform
anceIEEE Trans, vol AES-15
, No [i, I) p803. There is a document called Nov, 1979J.

FIG. 4 is a diagram showing the general configuration of the above-described adaptive antenna device.

As shown in the figure, the adaptive antenna device includes a weight circuit 11 that weights amplitude and phase of signals received by a plurality of antenna elements 10, a combiner 12 that combines these weighted signals, and a signal received by the antenna elements 10. It is comprised of a signal processing circuit 13 that determines the antenna weight of the weight circuit 11 from the obtained signal and the output signal of the combiner 12.

Various algorithms for determining antenna weights have been reported. An example of this is the power inversion array (hereinafter abbreviated as PIAA) described in the above-mentioned document. In PIAA, antenna weights are determined to minimize the power of the combiner 12 output signal. This means that signals with high power are easily removed.

Now, suppose that the desired signal and the interference wave are arriving from different directions, and the desired signal power Ps received by the antenna element 10 is sufficiently smaller than the interference wave power Pi, that is, Ps<<P
Let it be i. In such a situation, the antenna weight is almost determined by the interference wave with a large power, and an antenna directivity having a zero point in the direction of the interference wave is obtained. That is, at the output end of the combiner 12, the relationship p s >> p i holds.

As described above, a feature of PIAA is that the relationship between the power of the desired signal and the interference wave is reversed between the input end and the output end.

In other words, power inversion holds true.

As described above, due to the power inversion property of PIAA, when the desired signal power received by the antenna element 10 is sufficiently smaller than the interference wave power, the desired signal effect is exhibited. Conversely, if the desired signal power is larger than the interference wave power, the desired signal will be suppressed and the use of PIAA will have the opposite effect.

FIG. 5 shows the operating characteristics of the PIAA with respect to changes in the desired signal power when the interference wave power is kept constant.

Here, the horizontal axis represents the desired signal power received by the antenna element 10, and the vertical axis represents the S I N at the output end of the combiner 12.
R (Signal to Interf'erl'e
nce andNolse Ratio). The solid line shows 5INR when PIAA is used, and the broken line shows 5INR when PIAA is used.

As is clear from the figure, when the desired signal power Ps is small, the interference waves are sufficiently suppressed and 5INR is proportional to Ps. As Ps increases, 5INR gradually begins to saturate, and as Ps increases further, 5INR becomes inversely proportional to Ps. In other words, in such a state, the PIAA operates to suppress the desired signal more than the interfering waves. The most extreme example is a state in which there are no interfering waves and only the desired signal. In such cases, PIAA
operates to further suppress the desired signal, resulting in desired signal deterioration greater than that shown in FIG.

For example, if the 5 INR output of the PIAA required to operate the synchronization circuit of the spread spectrum communication receiver connected to the output end of the synthesizer 12 of the PIAA is shown as a dashed line in FIG. Communication is possible on the left side of the intersection of the dashed-dotted lines, but synchronization cannot be achieved on the right side, making communication impossible. In communications by mobile bodies, etc., the dynamic range of a desired signal is generally as large as 60 dB or more, and a situation as shown in FIG. 5 occurs in which the desired signal is larger than the interference wave.

In 22, PI is used as an example of an adaptive antenna device.
Although the explanation has been made using AA, similar desired signal degradation occurs when the desired signal power increases, for example, in an MSN adaptive antenna device that determines the antenna weight based on the maximum SN ratio. In the MSN adaptive antenna device, it is necessary to completely know the arrival direction of the desired signal and to incorporate this information into the signal processing circuit in the form of a steering vector. However, in reality, the direction of arrival of the desired signal itself may be different, or due to mechanical directivity errors of the antenna and electrical errors of the receiver.
This is equivalent to an error in the arrival direction of the desired signal, and as the desired signal power increases, the desired signal loss also increases, a phenomenon similar to PIAA.

(Problems to be Solved by the Invention) As described above, in the conventional adaptive antenna, when the desired signal power becomes larger than the interference wave power, the desired signal loss increases and the SN ratio decreases. Also,
A problem arises in that a wide dynamic range of desired signal power that can be used for communication cannot be obtained.

The present invention has been made in view of the problems of the above-mentioned conventional example.
The purpose is to have interference wave suppression performance comparable to that of conventional adaptive antenna devices when the desired signal is small compared to the interference waves, and when the desired signal is large compared to the interference waves. Another object of the present invention is to provide an adaptive antenna device that can improve desired signal loss and expand the dynamic range of interference wave power that can be used for communication.

[Structure of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention provides synchronization between an adaptive antenna into which a received signal is introduced and the received signal introduced by this adaptive antenna. The adaptive antenna is activated or deactivated depending on the synchronization circuit to be established and the synchronization established state or synchronization non-established state of this synchronization circuit, and when synchronization is not established, the time is twice or more the synchronization establishment time. The apparatus further includes a control circuit that repeats the operation or non-operation of the adaptive antenna at intervals and fixes the adaptive antenna to either the operating or non-operating state when synchronization is established.

Further, a second invention is the above invention used under a spread spectrum communication system.

(Function) In the present invention, by controlling the operation of the adaptive antenna particularly by the synchronization state of spread spectrum communication, when the desired signal power is small compared to the interference wave power, the adaptive antenna is finally turned on. When the desired signal power is large compared to the interference wave power, the adaptive antenna is finally turned off to reduce the desired signal loss. . Also, if synchronization is not established,
By repeating ON and OFF of the adaptive antenna at a time interval that is twice or more the synchronization establishment time, it is possible to stably receive a desired signal. Therefore, in the present invention, communication quality can be improved regardless of the relationship between desired signal power and interference wave power.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram showing the configuration of an adaptive antenna device according to an embodiment of the present invention. Here, the adaptive antenna device will be described as a PIAA.

In FIG. 1, an antenna element 1, a weight circuit 2, a combiner 4, and a signal processing circuit 5 are the same as those shown in the conventional example. The switch 3 is inserted between the weight circuit 2 and the combiner 4, and turns the adaptive antenna device on or off according to a control signal from the control circuit 6. However, in the OFF state, the switch 3 is not inserted between one element of the antenna cable 1 and the combiner 4 in order to ensure at least a receiving state.

With such a configuration, the adaptive function can be set to an active state and a non-active state, respectively.

A synchronous circuit 7 is connected to the output end of the synthesizer 4,
This synchronization circuit 7 extracts the synchronization signal of spread spectrum communication (-i).The synchronization signal extraction of the synchronization circuit 7 is
In the case of the S method, a sliding correlator and a SAW convolver are used, and in the case of the FH method, a frequency synthesizer is used. The time it takes to establish synchronization is determined by the circuit configuration of the synchronization circuit, the length of the code used in spread spectrum communication, and the like. Further, the synchronization circuit 7 generates a binary synchronization establishment state signal indicating whether synchronization is established or not, and supplies it to the control circuit 6.

The control circuit 6 generates a control signal for the switch 3 in accordance with the time chart shown in FIG. 2 based on the binary information of the synchronization establishment state signal of the synchronization circuit 7.

In the figure, (a) shows a synchronization establishment state signal, (b) shows a control signal, and T shows a time interval that is twice or more the synchronization establishment time. Here, for convenience of explanation, the binary logic of the synchronization establishment state signal and the control signal is defined as follows.

Synchronization establishment state signal H: Synchronization is established. Synchronization establishment state signal L: Control signal where synchronization is not established.
H: Control signal to turn on switch 3 L
...When the synchronization establishment state signal that turns off the switch 3 is L, the control circuit 6 generates a control signal that repeats H and L at a time interval that is twice or more the synchronization establishment time. On the other hand, when the synchronization establishment state signal transitions from L to H, the control circuit 6 stops this repetitive operation, selects either the state H or L of the control signal at this moment, and outputs the synchronization establishment state signal. The state of this control signal is maintained during the period when is H. Furthermore, the synchronization establishment state signal changes from H to L.
When the transition occurs, the repeating operation of H and L of the control signal is started again. The control circuit 6 that performs the above operation is
It can be easily configured using digital circuits.

Hereinafter, the operating principle of the embodiment of the present invention will be explained in detail. First, consider a situation where synchronization has not been established.

In this case, the following two situations are possible.

(1) When the desired signal does not exist In this state, there is no need for communication, so the adaptive antenna device is turned on regardless of the interference wave.
There is no problem whether it is in the OFF state or the OFF state.

However, it is of course necessary to wait for the desired signal.

In this standby state, the operation of the adaptive antenna device is turned ON and OFF at a time interval of more than twice the synchronization establishment time.
F is given. The reason for setting the ON or OFF time interval to be more than twice the synchronization establishment time is that in the adaptive antenna device, the starting point of the code used for spreading in spread spectrum communication is unknown, and the synchronization signal input operation is Turn the adaptive antenna device ON or OFF until the end.
This is because it is desired to maintain the state of , keep the input signal of the synchronization circuit 7 as constant as possible, and perform the synchronization pull-in operation stably.

(2) When the desired signal exists In the situation where the desired signal has arrived, there are four cases in total: whether the desired signal power is greater than the interference wave power, and whether the adaptive antenna device is in the ON state deaf or OFF state. is possible.

First, consider a case 1 in which the desired signal power is smaller than the interference wave power and the adaptive antenna is in the ON state. In this case, since the adaptive antenna suppresses interference waves, synchronization establishment ends during the ON state. At the end of synchronization establishment, the synchronization circuit 7 sets the synchronization establishment state signal to H, and the control circuit 6 keeps the control signal ON.

This state is maintained until the desired signal that terminates the communication is not present.

Next, as case 2, the desired signal power is similarly smaller than the interference wave power, but the adaptive antenna device is
Consider the case of F state. In this case, since the interference wave power is large and the adaptive antenna device is off, the output of the synthesizer 4 is dominated by interference waves, making it difficult to establish synchronization. Therefore, the synchronization establishment state signal remains at L. However, since a synchronization establishment state signal is provided, in the worst case, the control signal changes from high to high after twice the synchronization establishment time. In other words, the adaptive antenna device is turned on. Since this is the same as in case 1, it is possible to suppress the interference waves and receive the desired signal from now on. The subsequent operation is similar to case 1.

As case 3, consider a case where the desired signal power is greater than the interference wave power and the adaptive antenna device is in the ON state. In this case, the adaptive antenna device suppresses the desired signal, making it difficult to establish synchronization. Therefore, the synchronization establishment state signal remains at L. However, since the synchronization establishment state signal remains at L, the control signal transitions from H to L after more than twice the synchronization establishment time. In other words,
Since the adaptive antenna device is in the OFF state, the desired signal is not suppressed from now on, and the desired signal becomes dominant in the output of the combiner 4, and synchronization establishment is achieved. Accordingly, since the synchronization establishment signal and the H1 control signal remain at L, the OFF state of the adaptive antenna device is maintained. From then on,
It can be seen that the desired signal loss due to the adaptive antenna arrangement is avoided.

Finally, as Case 4, the desired signal power is similarly larger than the interference wave power, but the adaptive antenna device is
Consider the case of F state. At this time, the desired signal is dominant in the output of the synthesizer 4, there is no equivalence problem, and communication is possible. This OFF state is maintained until communication is completed.

As described above, according to the adaptive antenna device of this embodiment, if a desired signal is applied before synchronization has been established, depending on the situation, in the worst case, communication may be interrupted for a period twice as long as the synchronization establishment time. possible, but the desired signal loss is avoided thereafter.

Next, consider a situation where synchronization has already been established.

In this state, there is no problem whether the adaptive antenna device is in the ON or OFF state.

However, if a large power interference wave is newly applied while the adaptive antenna device is in the OFF state, communication becomes temporarily impossible. However, by the same operation as described above, the adaptive antenna automatically shifts to the ON state, so that the interference wave suppression function is exhibited in the next phase.

In this way, according to the adaptive antenna device of this embodiment, the adaptive antenna device automatically operates to a state where communication is possible, regardless of the relationship between the desired signal power and the interference wave power or the 0N10FF state of the adaptive antenna device. mode can be set. The 5INR at the output end of the adaptive antenna device at the time when it is turned ON or OFF and the operating state of the adaptive antenna device is fixed is as shown in FIG. The definitions of the horizontal and vertical axes are the same as in the case of FIG. 5 shown in the description of the conventional example. Comparing FIG. 3 and FIG. 5, it is found that when the desired signal power is small compared to the interference wave power, the present embodiment and the conventional example are equivalent, but conversely, when the desired signal power is large, The present invention avoids desired signal loss and improves 5 INR.

Note that the present invention is not limited to the above embodiments.

For example, in the configuration example of the embodiment shown in FIG. 1, the switch 3 is inserted between the weight circuit 2 and the synthesizer 4 in order to set the adaptive antenna device to the OFF state. A similar operation is achieved by setting the antenna weights of the weight circuit 2 to zero for all elements except one element in the case of PIAA, and by setting the antenna weights of the weight circuit 2 to zero in the case of the MSN algorithm in accordance with the desired signal direction. This can be realized by using a vector.

Furthermore, the 0N-OFF operation of the present invention can be performed by converting the received signal into an A/D
After conversion, it may be implemented in software in a computer or digital circuit.

As described above, the present invention can be modified and used in various ways without departing from the gist thereof.

[Effects of the Invention] As explained above, according to the present invention, the operation mode of the adaptive antenna device can be automatically set to a state in which communication is possible, regardless of the relationship between the desired signal power and the interference wave power. can. As a result, when the desired signal power is small compared to the interference wave power, the present invention exhibits an interference wave suppression function equivalent to that of the conventional example, and when the desired signal power is large, the desired signal loss is reduced. This can be avoided and the INR can be improved by 5.

As described above, the present invention is capable of enabling an adaptive antenna device to operate in a wide dynamic range of desired signals with a simple configuration, and at the same time, it is possible to improve the communication quality of spread spectrum communication in particular. It is possible to achieve sufficient effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an adaptive antenna device according to an embodiment of the present invention, FIG. 2 is a time chart showing the relationship between a synchronization establishment state signal and a control signal, and FIG. 3 is a diagram showing a case where the present invention is used. 5INR characteristics at the output end of the adaptive antenna device of FIG. 4 is a block diagram of the adaptive antenna device used to explain the operation of the conventional example, and FIG. 5 is a diagram showing the 5INR characteristics of the conventional adaptive antenna device. be. DESCRIPTION OF SYMBOLS 1... Antenna, 2... Weight circuit, 3... Switch, 4... Combiner, 5... Signal processing circuit, 6...
...Control circuit, 7...Synchronization circuit. Applicant: Toshiba Corporation

Claims (2)

[Claims] (1) an adaptive antenna into which a received signal is introduced; a synchronization circuit that establishes synchronization with the received signal introduced by this adaptive antenna; When the adaptive antenna is activated or deactivated, and synchronization is not established, the adaptive antenna is activated or deactivated repeatedly at a time interval of twice or more the synchronization establishment time, and when synchronization is established, the adaptive antenna is activated or deactivated. 1. An adaptive antenna device comprising: a control circuit that fixes an antenna in either an operating or non-operating state. (2) The adaptive antenna device according to claim 1, wherein the adaptive antenna device is used under a spread spectrum communication system.