JPS6043694B2 - Interference signal detection and removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for detecting interference signals in communication lines.
The present invention relates to an interference signal removal method that uses an interference source signal to detect and remove the amplitude and phase of the interference signal.

Methods to avoid interference in communications include making the interval between carrier frequencies larger than the bandwidth occupied by the transmission signal, removing interference signals using a Fuchika circuit, and making the antenna directionality sufficiently large. method, the degree of polarization discrimination of radio waves is maintained above the required value. Methods such as this have been implemented.

In order to improve frequency usage efficiency with the development of communications,
Frequency intervals, antenna directivity intersection angles, etc. become narrower,
In addition, the degree of polarization discrimination of radio waves in particular deteriorates significantly during heavy rainfall, and the scattering strength of radio waves is large. The interference strength increases depending on the weather conditions.

Furthermore, communication systems that make effective use of frequencies are increasingly being used in the frequency domain. This has increased the need to detect, compensate for, and eliminate interference signals during communication.
In general, when communicating by modulating two separate communication signals using two carrier waves of cross polarization in the same frequency band,
In order to detect mutual interference between two communication channels, the received wave is demodulated, the carrier wave is modulated, and this is subtracted from the received wave to extract only the interference wave component, and this interference wave component is used to receive the interference source. There is a proposal to obtain interference information through synchronous detection using waves (Japanese Patent Application No. 7803, 1983).

In this method, the interference wave detection circuit input is usually at a considerably lower level than the desired received wave after interference compensation, so after performing demodulation and modulation to extract only this interference wave component, the difference It is difficult to maintain the accuracy of the circuit to a negligible level compared to the level difference, and even if this were possible, the desired wave and interference wave would have a wide occupied bandwidth, and each would have noise. , and have a distortion spectrum, it is also difficult to perform interference detection using these.

An object of the present invention is to provide a wireless communication system that eliminates undetectable interference.

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram illustrating the interference path, in which 1, 2, 3 and 4 are transmitting and receiving devices, respectively, and 3 and 4 are devices located at the same location.

5, 6, 7, and 8 are transmitting/receiving terminals 1, 2, 3, and 4, respectively, and the transmission paths 5-7, 6-8 may be in different directions or in the same direction.

7 and 8 may be different antennas or the same antenna in wireless communication.

In the following explanation, a transmission signal from the device 1 is sent out from the transmission terminal 5, a normal reception signal is received by the receiving device of the device 3 via the reception terminal 7, and a signal sent from the terminal 5 is sent out from the reception terminal 8 by the device. A case where the interference signal is received as an interference signal by the receiver of No. 4 will be described.

In this case, the normal reception signal of the receiving device of device 4 is a signal received by the transmission signal of device 2 via 6-8. When the transmission lines 5-7 and 6-8 are in the same direction, the terminals 5 and 6 are often the same antenna. When such interference occurs, the signal sent from the terminal 6 generally also adds an interference signal to the receiving device 3 via the terminal 7. FIG. 2 is a block diagram of a removal circuit according to an embodiment of the present invention.

A signal received by the receiver 3 is applied to a terminal 10, and a signal received by the receiver 4 is applied to a terminal 11. In this case, it is assumed that the correlation between the normal received signal applied to the terminals 10 and 11 and the interference signal is the same as that at the terminals 7 and 8. Terminals 12 and 13 are each terminal 10
, 11 is an output terminal corresponding to the received signal, and 14 is a frequency converter for each received signal using the output of one local oscillator as a local input (or an amplifier, an attenuator, etc.) ), and the signal obtained at its output side is its input side. This is a buffer circuit that maintains the same correlation as the signal. 15 is a circuit for detecting an interference signal according to the present invention, and 16 is an interference signal removal circuit controlled by the output of the circuit 15.

17 and 18 are frequency converters, 19 is a local oscillator whose oscillation frequency can be controlled, 20 and 21 are wave generators, 22 and 23 are frequency converters, 24 and 25 are wave generators, 26 is an amplitude constant circuit, 27 is a demodulator (DEM) that detects only the angle modulation component.
), 28 is a door wave device, 29 is an angle modulator (MOD), 30
, 31 are narrow band door filters having the same characteristics, and 39 is a frequency phase change detector, which together with the oscillator 19 constitute an M°C circuit.

34 synchronously detects the signal of input 33 with the signal of input 32,
= amplitude ratio of input 33 to input 32 at output terminal 35;
This is a circuit that similarly extracts phase difference information from the output 36.

These signals are applied to an interference cancellation circuit 16, which branches a signal 37, adjusts its amplitude and phase, and adds it to a signal 38 so as to cancel the interference signal. Frequency converter 22, 23
If the input signals of are Sl and S2, these are terminals 10,
It holds the same state as the input signal of 11, and S1=Y1
+Y2, S2=Y2+y1.

Yl and Y2 are normal received signals of the receiving devices 3 and 4, respectively, and Yl and y2 are interference signals to the devices 4 and 3 via paths 5-8 and 6-7, respectively. Y1=Aejθ1, y1:
Aej (θ1+012), Y2 BejO2, Y2:1
11ejCθ2+021), and frequency converter 22,
The other input to 23, ie the output of MOD29, is L=FJ
OL. ．． The outputs of the Okiwave devices 24 and 25 are respectively S3=S3
Let ejO3, S4=S4ejO4. Also DEM27
The demodulation sensitivity of D. Let the modulation sensitivity of MOD29 be β, and dβ
〉〉1. The amplitude constant circuit 26 removes the amplitude change, the demodulator 27 demodulates only the angle modulation, and the wave modulator 2
8 extracts only the necessary signals, high-order cross-modulation components of Y1+Y2 are removed by oscillation, and then the local oscillation frequency is angularly modulated by MOD 29. The input signal S1 of the frequency converter 22 is S1:Y1+Y2:Aejθ1+Bej(02+
θ21) However, it can be expressed as.

Regarding the calculation of this formula, see RFM Radio Engineering, edited by Sugawara, published by Nikkan Kogyo Shimbun, pp. 526-566, 1939.
Please refer to the July 4 issue of Kui. Output signal S of door wave device 24
3 becomes .

Output L of MOD29=LeJOL=Lej(ωLt+M
22-24-26-27-28-2
9-22 forms a feedback loop for angle modulation, the angle modulation of the circuit 22-24 is constant, and the circuit 26-27-28-
If the angle modulation of the circuit No. 29 is dβ, then ω01
= ω1 - ω, Δω = ω2 - ω1, ω1 is θ1, ω2 is θ2, ω, is the carrier angular frequency of θ, M1 and M2 are the angle modulation signals of Y1 and Y2, respectively, ]1
This shows that the bandwidth is limited to the minimum necessary bandwidth corresponding to the modulated signal of M1, and cross-modulation components other than the frequency band of the modulated signal are removed.

If the modulation is compressed to 1/(1+dβ) as shown in equation (4) and then added to the filter 30 which extracts only the ω01 component, the output will have the first term ω.

one component and the other - M1's ω. Only nearby sideband waves are extracted as noise 1+dβ sound.

This signal 32 is supplied as a reference signal to the correlation detection circuit 34. In this way, the circuits 26 to 29 are connected to the frequency converter 22
The local oscillation frequency (signal) of the frequency converter 22 is ordered so as to minimize the angle modulation component of the output of the frequency converter 22. The output S4 of the frequency converter 23 and the wave generator 25 is ω.

=ω2−ω5 is shown. When the signal of equation (6) is applied to the wave generator 31 having the same characteristics as 30, the first term is removed from the output, and the second term (ω01t-θ12) component and ω.

A small number of cross-modulation wave components in the vicinity of 1 are extracted as noise.

The amplitude ratio of the first term and the second term is B/a, and the first term is large, but the first term is modulated by (M2-M1) and the sideband waves are spread. The second term is concentrated at (ω01t-θ12), and the sideband waves are only noise components. Therefore, in the output of the filter 31, the second term is dominant.

This signal 33 is applied to a correlation detection circuit 34. circuit 34
The amplitude and phase of the signal 33 are detected using the signal 32 as a reference and the noise components of the amplitude and phase removed.

In this way, output terminals 35 and 36 of circuit 34 are
1 amplitude a and phase θ1.

information can be retrieved. Since the transducers 30 and 31 that transmit only the ω01 component have an extremely narrow band, the ω01 component is transmitted only to the ω01 component.
The oscillation frequency of the local oscillator 19 is controlled through the detector 39 so that the oscillation frequency is set at their center.

FIG. 3 shows a block diagram of another embodiment for detecting information on the amplitude a and phase θ12 of the interference signal.

In the figure, an amplitude constant circuit 26, a demodulator 27, and a waveform generator 2 are used for local oscillation input of a frequency converter 22 that compresses a modulation M1 of a normal received signal Y1 and extracts its carrier wave component.
8. Instead of the modulator 29, the output of the wave generator 20 is branched, and a frequency conversion circuit 41 and a wave generator 42 are used. This circuit 41 is composed of a voltage controlled oscillator (VCO) and a phase pull-in oscillator consisting of a phase comparator that compares the phases of the output of this VCO and the output of the door converter 20 and controls the VCO based on the comparison output. The output of CO undergoes the same angle modulation as S1 and has a frequency necessary as a local oscillator for frequency converter 22.

This circuit 41 may also be a frequency converter and an amplitude limiter. The output of the circuit 41 is applied to the frequency converters 22 and 23 through a band limiting filter 472. Even if such a circuit is used, the outputs of the wave generators 24 and 25 will be almost the same as in the case of FIG. 2. In this way, the circuits 41 and 42 may be of any type as long as they generate the local frequency (signal) of the frequency converter 22 that minimizes the angular modulation of the frequency converter 22, as shown in FIG. . The input frequency ω is at the center of the narrowband p-wave generator 30.

AF'C for adjusting the frequency 1 is composed of a frequency conversion circuit 45 including a frequency reference and a frequency converter (MIX) 43.

In this case, a frequency converter 44 circuit similar to the frequency converter 43 is used for the other system. N°C is the frequency conversion circuit 41
The frequency of the oscillator included in the oscillator or local oscillator 40 may be controlled and configured. AF installed in Figures 2 and 3
C is an extremely narrow waveform generator 3 whose center frequency is ``ω0,''
It plays an important role in selecting and extracting only the carrier wave component of Y1 whose modulation is compressed by 0,31 and the carrier wave component of y1. Generally, the interference signal strength is sufficiently small compared to the normal received signal strength, so the strength of the interference signal taken out to the output of the wave filter 31, La in equation (6), is smaller than the LB to be removed by the wave filter 31. Small enough.

ω in order to effectively remove the LB component by the narrowband Oki transducer 31 and obtain only the h component in its output. And ω. Difference of 1 (Δ
ω) is selected to be large compared to the passband widths of 30 and 31.

It is more effective if the components are outside the band 31. By selecting the 5 and 6 output carrier frequencies on the transmitting side in this way, the present invention can be more effective. In this way, the interference noise components of the second and third terms of equations (4) and (5) and the first and second terms of equation (6) can also be removed, and the interference noise component is It becomes effective when the intensity of is very low. As described above, it is possible to obtain a means for detecting the relationship between the amplitude and phase of the interference signal with respect to the normal reception signal, so by using this information, part of the normal reception signal can be branched, and the signal can be controlled using this information to prevent interference. Interfering signals can be canceled by adding signals in a canceling manner.

2 and 3, circuit 16 has an output signal 35
, 36, which generates a signal for removing interference signals.

That is, the circuit 16 has an amplitude and phase variable circuit,
By controlling the amplitude and phase of signal 37 using signals 35 and 36, the controlled signal 35 is added to signal 38, and Y2+
Cancel y1 of y1. An example of a comprehensive circuit for removing interference signals is shown in FIG.

In FIG. 4, 50 and 51 are cancellation signal generation circuits, and 15-1 and 15-2 are circuits similar to 15 that detect interference signals Yl and y2 received at input terminals 11 and 10, respectively. 52, 53 and 54, 55 are respectively y
It is an output that gives amplitude and phase information for Y1 of Y1 and Y2 of Y2, and the signal 35 in FIGS. 2 and 3
, 36.

On the input side, the signals received at receiving terminals 10 and 11 are branched and applied to circuits 50 and 51, and after being controlled using this information, they are added to the signals received at receiving terminals 11 and 10.

In this way, stable operation is performed so that the Y2 and yl components included in the signals taken out to the terminals 12 and 13 are minimized. FIG. 5 shows that the receiving terminals 60 and 61 receive, for example, communication line signals of a plurality of carrier waves, and the terminals 60 and 6
FIG. 1 is a block diagram in the case of receiving radio waves in the same frequency band with radio polarizations different from those in FIG.

In this case, it is assumed that the plurality of communication lines received at the terminal 60 have the same propagation characteristics, and the lines received at the terminal 61 also have the same characteristics. 62 is a circuit for branching the receiving line and removing interference.

63 and 64 are branch reception output terminal groups corresponding to the signal groups received at the terminals 60 and 61, respectively. 15-1 is 60
15-2 receives as input a signal branched from one of the received signals received at 61, and inputs a signal branched from the received signal having the same frequency occupation band as the input of 15-1 received at 61.

15-1 and 15-2 are the same as the circuit described in FIG.

Outputs 52, 53 and 54, 55 of 15-1, 15-2
are represented by 65 and 66, respectively.

65 and 66 are used to control the interference cancellation circuit included in the circuit 62.

Reference numerals 65 and 66 indicate information indicating the relationship between one received signal received in each of the line groups 60 and 61 and the corresponding interference signal contained therein.

Using this information, the interference cancellation circuits for the received signal groups 60 and 61 are controlled. In this way, as mentioned above, 60
When the propagation characteristics are the same between the signals 63 and 61, the interference signal can be removed from the received signal group obtained at 63 and 64, and the removal can be carried out economically. FIG. 6 is a block diagram for performing preliminary interference cancellation of a transmitted signal when an interference signal generated between a received signal and a transmitted signal can be predicted. Circuit 15-1, 15
1 and 2 are circuits as shown in FIG. 4 that detect interference information from the received signal, respectively, and a second transmission device that sends out a transmission signal to a transmission path having the same transmission characteristics as that of the received signal. A circuit 72 is provided for applying interference to the signal in advance so as to compensate for interference signals generated on the transmission path. terminal 70
, 71, for example, transmit a plurality of communication signals using different polarization planes of radio waves in the same frequency band. 73, 74
are connection terminals for the second transmission signal from the second transmitter connected to 70 and 71, respectively.

15-1 and 15-2, 65 and 66 are shown in FIG. 5, respectively.

72 is a circuit that performs transmission preliminary interference and transmission signal/signal synthesis.

When the signal groups transmitted from 70 and 71 have the same propagation characteristics, an interference signal in which the transmitted signal group 73 and that of 74 interfere with each other is detected from the received signal 6
Interference is added in advance using the information of Nos. 5 and 66, and this is controlled so that it compensates for and cancels out the interference occurring on the propagation path.

In this way, effective interference cancellation is possible on the transmitting side. As explained above, only the angular modulation part of the received signal is demodulated and added to the band-limiting transducer. Interference signal information can be stably obtained by adding the output to a narrowband door filter with the same characteristics.

Using this information, it becomes possible to eliminate interference, which has the advantage of making effective use of frequencies and realizing a high-density communication network.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an interference path of a communication line, FIG. 2 is a block diagram of a first embodiment of the removal method of the present invention, FIG. 3 is a block diagram of a second embodiment of the present invention, and FIG. 6 are block diagrams of third to fifth embodiments of the present invention. In the figure, 2, 3, 4... transmitter/receiver, 5,
6, 7, 8... Transmission/reception terminal, 10, 11, 60
, 61...Reception terminal, ]2, 13, 35, 36, 5
2-55, 63-66...Output terminal, 14...
... Buffer circuit, 15 ... Interference signal detection circuit, 1
6, 62... Interference cancellation circuit, 17, 18, 22
, 23, 43, 44... frequency converter, 19...
Local oscillator (VCO), 20, 21, 24, 25, 28
, 30, 31... Door wave device, 26... Amplitude constant circuit, 27... Angle demodulator, 29...
...Angle modulator, 32, 33...Input terminal, 3
4, 50, 51... Correlation detection circuit (removal signal creation circuit), 37... Branch signal, 38...
・Removal signal, 39... Frequency phase change detector,
40... Local oscillator, 41... Frequency converter, 42... Amplitude limiting waveform generator, 45...
Frequency shift circuit, 70, 71... transmission terminal, 72...
. . . Pre-interference circuit, 73, 74 . . . Transmission connection terminals.

Claims (1)

[Claims] 1. Consisting of a plurality of transmitting and receiving devices, the transmitted signal from the first transmitting device is not only properly received by the authorized first receiving device, but also not interfered with by another second receiving device. In a wireless communication system in which the signal is received as a signal, a first frequency converter inputs the first received signal of the first receiving device, and a first frequency converter that receives the first received signal or the output of the first frequency converter. first means for generating a local frequency for the first frequency converter responsive to minimize the angular modulation component of the output of the first frequency converter; A normal reception signal detection circuit including a first narrowband filter for extracting a carrier component of the normal reception signal from the output, and a second reception signal of the second receiving device and the output of the first means are inputted. a second frequency converter for extracting a carrier component of an interference signal from the output of the second frequency converter; a signal detection circuit; a correlation detection circuit that outputs an amplitude ratio and a phase difference of an interference signal with respect to a normal reception signal from an output of the normal reception signal detection circuit and an output of the interference signal circuit; An interference signal detection and removal method comprising a circuit that controls the amplitude and phase of the first received signal to remove an interference signal contained in the second received signal. 2. In a wireless communication system in which a plurality of transmitted signals in the same frequency band are not only received by a regular first receiving device but also received as interference signals by another second receiving device, the first receiving device a first frequency converter inputting a first received signal of the first frequency converter; Minimize. a first means for generating a local frequency for the first frequency converter; and a first narrow band filter for extracting a carrier component of a normal received signal from the output of the first frequency converter. a normal received signal detection circuit; a second frequency converter inputting the second received signal of the second receiving device and the output of the first means; an interference signal detection circuit including a second narrowband filter having the same characteristics as the first filter for extracting the carrier wave component of the signal; and an output of the normal received signal detection circuit and the interference signal detection circuit. a correlation detection circuit that outputs the amplitude ratio and phase difference of the interference signal with respect to the normal reception signal from the output surface; and the output of the correlation detection circuit controls the amplitude and phase of the other reception signal of the second reception device. An interference signal detection and removal method comprising a circuit for removing an interference signal included in a received signal that is interfering with the other received signal. 3 Consisting of a plurality of transmitting and receiving devices, the first transmission signal from the first transmitting device is received by the authorized first receiving device as well as being received as an interference signal by another second receiving device. In the wireless communication system, the first frequency converter receives the first received signal of the first receiving device; first means for generating a local frequency for the first frequency converter that minimizes an angular modulation component of the output of the first frequency converter; a normal received signal detection circuit including a first narrowband filter for extracting a carrier component of the received signal; and a second receiving signal receiving circuit that receives the second received signal of the second receiving device and the output of the first means. an interference signal detection circuit including a frequency converter and a second narrowband filter having characteristics equivalent to those of the first filter for extracting a carrier wave component of the interference signal from the output of the second frequency converter. a correlation detection circuit that outputs an amplitude ratio and a phase difference of the interference signal with respect to the normal reception signal from the output of the normal reception signal detection circuit and the output of the interference signal detection circuit; An interference signal detection and removal method comprising a pre-interference circuit that controls the amplitude and phase of a second transmission signal of a transmitter and provides an interference signal to the second transmission signal.