JPS63240226A - Reception system for spread spectrum signal - Google Patents

Abstract

PURPOSE:To keep the S/N to >=0dB over a wide range of a disturbance wave level and a desired wave level by weighting each output of an array antenna, obtaining all added outputs and subtracted outputs, synthesizing them while making the level of the both nearly equal to each other and inputting the result to a spread spectrum receiver. CONSTITUTION:Outputs of omnidirectional antenna elements 1, 1' arranged at a prescribed interval are branched into weighting circuits 2, 2' and weight control circuits 3, 3' based on the PI (power inversion)algorithm, outputs of the control circuits 3, 3' are added by an adder 4 while the amplitude and phase are controlled by the weighting circuits 2, 2', and subtracted by a subtractor 5. The signals are amplified to be in nearly equal level by automatic gain control amplifiers 6, 6', synthesized by an adder 7 and inputted to a spread spectrum receiver 8. Through the constitution above, a signal with a smaller level among the signal received by the antenna is outputted while its level is increased and a signal with a larger level is outputted while its level is decreased from the adder 4, and a signal received by the antenna larger in level is increased at the subtractor 5.

Description

[Detailed Description of the Invention] (Field to which the invention pertains) The present invention relates to a method for receiving spread spectrum radio waves,
In particular, it relates to a spread spectrum signal reception method using an adaptive antenna.

(Prior art) In recent years, spread spectrum (ss: 5spread sp.
ectrum) method is being put into practical use.

The spread spectrum communication method is a method of transmitting or receiving electromagnetic energy by spreading it within a relatively wide frequency band, and the desired wave level is below the noise label, that is, S/
Even if N is less than odB, the so-called processing gain
Therefore, it is possible to improve the S/N ratio to more than odB, and in a noisy and malicious communication channel, much better speech quality can be obtained compared to the conventional narrowband communication method. .

On the other hand, the amplitude of the output signals of array antennas arranged at predetermined intervals as a means for suppressing and eliminating interference waves of the same frequency arriving from different directions.

A so-called adaptive antenna that extracts only incoming radio waves from a desired direction by performing weighting processing to control the phase (or delay time), etc. is being researched.

Therefore, it has been proposed in the past to further improve the S/N ratio by using both of the above-mentioned means in combination.

However, the conventionally proposed method mainly uses LM8
This is an adaptive antenna that uses the (Lpast Mean 5quare) method.In this case, the prerequisite is to be able to distinguish between the desired wave and the interference wave, such as by adding some special signal to the desired wave, but in reality, this is not possible. As such, it is rare and difficult to clearly distinguish between the two.

When it is difficult to distinguish between desired waves and interference waves.

It is possible to use a power inversion adaptive antenna (PI) as the adaptive antenna, but since the PI has the function of suppressing the higher level, the level of the desired signal and the interference signal will be different. If the interference wave level is large, it is effective to suppress the interference wave and improve the S/N ratio, but on the other hand, if the desired signal level is higher than the interference wave level, the desired wave will be attenuated and killed. /
Degrades N.

In this way, even if an interfering wave and a desired signal with a lower level are input to the SS receiver, it is possible to improve the 8/N ratio and perform 1 communication due to the processing gain of the SS system. be. However, as is well known, the PI has the characteristic of suppressing a signal with a high input level to a large extent, so if the level of the desired signal input to the antenna is very high compared to the interference signal, the output terminal of the PI In this case, the level of the desired signal is much lower than that of the interference signal, and - this signal is ss
Even with the processing gain of this method, it is not possible to improve the S/N ratio to more than OdB, and there is a problem that a telephone conversation becomes impossible.

(Object of the Invention) The present invention has been made in view of the circumstances explained above, and is based on PIK, which allows the desired signal level to be SS compared to the interference signal level.
Even if the S/N is suppressed below the processing gain of the method,
It is an object of the present invention to provide a reception method for spread spectrum signals that can be improved more than B and is easy to implement.

(Summary of the Invention) In order to achieve this object, in the present invention, each output of the array antenna is weighted to obtain all of these addition outputs and subtraction outputs, and the levels of both are made equal to y and combined. After that, it is configured to input to a spread spectrum receiver.

(Example) The present invention will be described in detail below based on the illustrated example. FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, reference numerals 1 and 1' are omnidirectional antenna elements arranged at predetermined intervals, and weighting circuits 2 and 2' and a weight control circuit 3 based on the PI algorithm are used to weight the respective outputs.
3′ and 2-weight control circuit 3.3.
The outputs of ' are input to the weighting circuits 2 and 2', and the signals whose amplitudes and phases are controlled are added by the adder 4, while
Subtraction is performed using subtractor 5. Automatic gain control (A
GC) Amplifiers 6 and 6' adjust the gains to amplify the signals to the same level, combine the signals in adder 7, and input the signals to spread spectrum receiver 8.

In the system configured in this manner, the function of the PI adaptive antenna causes the adder 4 to output the signal that has arrived at the antenna with a lower level as a larger signal, and a signal with a larger level as a smaller signal.

On the other hand, in the subtracter 5, the signal suppressed in the adder 4 is amplified, so that among the signals arriving at the antenna, the one with a higher level is not thicker, and the level ratio is expanded. Finally, the main component of the output signal of the adder circuit 4 is the signal with a lower level among the signals arriving at the antenna.

The main component of the output signal of the subtraction circuit 5 is the one with a higher level among the signals arriving at the antenna.
It is important to note that the signal that has been made equal in level by ' and combined in an adder 7 contains the higher and lower levels of the signals received at the antenna at approximately equal levels. Regardless of the 8/N ratio of the signal arriving at the antenna, the signal from the adder 7 always has an S/N ratio of 0 dB.

The spread spectrum receiver 8 has an input signal S/N ratio of OdB.
If it is about 8/N, the processing gain will be better, and the output 8/N will be higher than that, so if the configuration of this embodiment is adopted, the S/N of the incoming signal will be reduced.
It becomes possible to always demodulate the spread spectrum signal over a wide range of ratios.

The above embodiment shows an example of a configuration for maintaining the S/N ratio of the signal input to the SS receiver at OdB, and the method of implementing the present invention is not limited to that shown in FIG. Further, the antenna used may be a directional antenna.

(Effects of the Invention) Since the present invention is configured and functions as explained above, it is possible to take advantage of each feature of the spread spectrum communication method and to spread the signal across a wide range of interference wave level and desired wave level.
It is very effective in keeping the /N ratio above OdB and obtaining good call quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. 1.1'-1...Antenna element, 2
, 2' -9°...The weighting is based on the circuit,
3, 3' song...PI amplifier, 7
・・・・・・・・・Adder. 8...Spread spectrum receiver.

Claims (3)

[Claims] (1) A spread spectrum signal reception method characterized in that the levels of a desired wave and an interfering wave are made approximately equal using an adaptive antenna and then input to a spread spectrum receiver. (2) Control the amplitude and phase of the signals induced in multiple antenna elements arranged at predetermined intervals, find all the added signals and subtracted signals, equalize their levels, combine them, and spread the spectrum. 2. A method for receiving a spread spectrum signal according to claim 1, wherein the spread spectrum signal is input to a receiver. (3) The spread spectrum signal reception method according to claim (2), wherein the amplitude and phase of only some of the plurality of antenna elements are controlled.