JPS6357985B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a reception method for eliminating interference waves when interference waves are added to a communication path in digital transmission in wireless communication, and particularly to interference waves when interference waves with a narrow band compared to the signal are added to the communication path. This relates to a cancellation reception method. In recent years, especially in the field of military communications, there has been a demand for communication systems or reception systems that can continue communications even in the face of strong radio wave interference. this is
ECCM (Electronic Counter Counter Measure)
Also known as anti-jamming communications, it is considered a strategically essential function in electronic warfare. The ultimate form of such anti-jamming communication is SS (Spread
Although it is generally believed that the SS method will become a method for communicating multiplexed high-speed (approximately 1 Mbps or more) data signals in real time, it is currently or in the near future that the SS method cannot be effectively applied. , is considered to be quite difficult. Therefore, it is an object of the present invention to provide a method to ensure good communication by removing interference waves, especially when interference waves having a narrow band compared to the signal transmission bandwidth are added to a wireless communication channel. The aim is to obtain a receiving system that eliminates interference waves. According to the present invention, in a communication method for transmitting and receiving a digital signal through a wireless communication channel, there is provided a means for keeping constant the average value of the amplitude of a received input signal including interference waves, and a means for keeping the average value of the amplitude constant. means for demodulating a received input signal that has been dropped and obtaining an estimated value of transmission data using a determiner; and estimating and reproducing interference waves contained in the received input signal from the input signal to the determiner and the output signal of the determiner. means for keeping the average value of the estimated reproduced interference wave constant; and means for determining the interference wave included in the received input signal from the correlation between the estimated reproduced interference wave whose average value is kept constant and the received input signal. means for detecting the amplitude and phase of the detected interference wave, and controlling the amplitude and phase of the estimated reproduced interference wave, which is kept constant at the average value from the amplitude and phase of the detected interference wave, and the average value of the amplitude of the received input signal. means for subtracting the estimated reproduced interference wave whose amplitude and phase is controlled from the interference wave contained in the received input signal in a negative feedback manner, the apparatus being disposed before the means for keeping it constant; An interference wave removal reception method is obtained in which reception is performed while removing interference waves. Next, a detailed explanation will be given with reference to the drawings. FIG. 1 shows an example of a configuration in which the interference wave removal reception method according to the present invention is applied to a polyphase phase modulation synchronous detection method. In FIG. 1, 1 is a passband subtracter, 2 is a passband variable gain amplifier, and the gain is controlled by an automatic gain control amplifier (hereinafter referred to as an AGC amplifier) shown in 3. 4 is a PSK demodulator which includes a carrier recovery and a passband-to-baseband converter (not shown). 5 is a determiner (a type of waveform shaper, e.g. a comparator or threshold high gain amplifier whose value voltage is the voltage at the positive decision point),
Reference numeral 6 denotes a low-pass filter having an equivalent impulse response in the baseband of the total transmission and reception; 7 is a delay circuit that provides a delay time D equivalent to the delay time of the low-pass filter 6; 8 is a baseband subtracter; 9 is a linear modulator that converts the baseband output of the subtracter 8 into a passband using the reproduced carrier in the PSK demodulator 4; 10 is a variable gain amplifier for the passband; and 11 is an AGC amplifier. Gain controlled. Furthermore, 12 is a passband conjugate circuit for obtaining a complex conjugate signal, and 13 is a subtracter 1.
a multiplier (passband x passband) for obtaining a correlation output between the input signal to the conjugate circuit 12 and the output signal of the conjugate circuit 12; 14 is a low frequency generator that provides a time constant for integration;
15 is a baseband variable amplifier, and 16 is a multiplier (baseband×passband) for controlling the amplitude and phase of the output of the variable gain amplifier 10 using the output of the variable amplifier 15. Next, the operation of this device will be explained. Since the received input signal Sr to the subtracter 1 is the sum of the signal and the interference wave, it is expressed as Sr=√2αA(t) e ^j 〓〓 ^t +√2βB(t) e ^j 〓〓 ^t ...(1) be able to. However, both signal waves and interference waves are expressed as analytical signals. In equation (1), α represents the amplitude (effective value) of the signal wave, β represents the amplitude (effective value) of the interference wave, and A(t) is the baseband modulation signal (complex number) of the signal wave. <|A(t)| ² >, which represents the average value, is normalized to 1,
It is assumed that B(t) is a baseband modulation signal (complex number) of an interfering wave, and <|B(t)| ² > is normalized to 1.
However, between the two baseband modulation signals, B(t)
It is assumed that the time fluctuation of is extremely slow compared to A(t), and that B(t)B(t-D) holds true. Furthermore, ω〓 represents the angular frequency of the signal wave, and ω〓 represents the angular frequency of the interference wave. In FIG. 1, if we consider a state in which the subtracter 1 and the multiplier 16 are disconnected and the output Sf of the multiplier 16 is not added to the subtracter 1, the output of the variable gain amplifier 2 is output by the AGC amplifier 3. Normalizing the level to 1 gives us becomes. The demodulation function of the PSK demodulator 4 is to multiply the signal in equation (2) by γ・e ^-j 〓〓 ^t (γ is a constant) and extract a signal proportional to the baseband modulation signal, so the PSK demodulator 4 The output of

As [formula] becomes. Assuming that the interference wave is initially very small and α≫β ...(4) holds, equation (3) can be approximately expressed as A(t)+β/αB(t)e ^j( 〓〓 ^- 〓〓 ^)t ...(5). This formula (5) means that the received data is the transmitted data A
(t) component and the interference wave component β/αB(t) e ^j( 〓〓 ^- 〓〓 ^)t , which varies variously depending on the amplitude, phase, and frequency with this transmission data A(t) as a reference. Indicates that it is a composite vector. Part of equation (5) is determined by the determiner 5
A portion of the signal is input to the delay device 7. The determiner 5 determines the absolute value of the noise component of the vector in equation (5) |
If it is determined that β/αB(t)| is not larger than the absolute value of the transmitted data |A(t)|, that is, the input voltage is positive (or 0), as explained earlier, it is determined on the positive side. A point, that is, estimated reproduction data A^(t) (determination point) is output. In this case, it is necessary to use two determiners 5, one each for the real part and the imaginary part. Since the output of the delay device 7 is the signal of Equation 5 delayed by the delay time D in the equivalent impulse response of the low frequency device 6, A(t-D)+β/αB(t-D) e ^j( 〓〓 ^- 〓〓 ^)(t-
D) ...(6) Then, the low-band transmitter 6 receives the estimated transmission data A^(t)
Since it has an equivalent impulse response in the baseband of transmitting and receiving, the output through it is approximately A(t-D)...(7). Therefore, the output of the subtractor 8 is expressed as Equation (6) to Equation (7).
By subtracting β/αB(t-D) e ^j( 〓〓 ^- 〓〓 ⁾ (t-D)...(8) is obtained. Since the output of the linear modulator 9 is the product of the reproduced carrier e ^j 〓〓 ^t from the PSK demodulator 4 and equation (8), β/αB(t-D) e ^j( 〓〓 ^t- 〓 ⁾ ...(9) becomes. However, it is assumed that φ=(ω〓−ω〓)D. The output of the variable gain amplifier 10 is the output of the linear modulator 9, which is equation (9), normalized to 1, so B(t-D)e ^j( 〓〓 ^t- 〓 ⁾ ...(10 ) becomes. Also, since the output of the conjugate circuit 12 is the complex conjugate signal of equation (10), B ^* (t-D)e ^-j( 〓〓 ^t- 〓 ⁾ ...(11). However, * means complex conjugate. Since the output of the multiplier 13 is the product of the signal in equation (11) and the received input signal Sr, {√2αA(t) e ^j 〓〓 ^t +√2βB(t) e ^j 〓〓 ^t } ・B ^* (t-D)e ^-j( 〓〓 ^t- 〓 ⁾ ...(12) Under the initial assumption, A(t) and B
(t) are mutually uncorrelated, and B(t)B
(t-D) is assumed to hold, so if equation (12) is integrated through the low-frequency transducer 14, approximately √2βB(t)B ^* (t-D)e ^j 〓 √2βe ^j 〓 …… (13) becomes. The open loop gain K is added to this by variable amplifier 1.
Multiplying by 5 and multiplying equation (10) by multiplier 16, we get
The open loop value Sfo of the output Sf of the multiplier 16 is K・√2βe ^j 〓・B(t−D)e ^j( 〓〓 ^t− 〓 ⁾・√2βB(t)e ^j 〓〓 ^t ……(14 ) becomes. Next, in FIG. 1, by connecting the subtracter 1 and the multiplier 16, a negative feedback loop is constructed as a whole, and the closed loop value Sfc of the output Sf of the multiplier 16 is K/1+K・√2βB(t)e ^j 〓〓 ^t ……(15). Therefore, if the amplification factor K of the amplifier 15 is set sufficiently large, it is possible to synchronously detect the multiphase phase modulated wave while removing the interference wave component contained in the received input signal Sr. As explained above, in the reception method according to the present invention, interference waves having a narrow band compared to the signal transmission bandwidth, that is, unmodulated interference waves, and modulated signals having a low speed compared to the transmission speed of the digital signal to be transmitted Even if amplitude and phase modulated interference waves are added to the received input signal, the interference waves are estimated and subtracted from the reception input to remove the interference waves and maintain good communication can do.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of an interference wave cancellation receiving system according to the present invention. Explanation of symbols: 1 is a subtracter, 2 is a variable gain amplifier, 3 is an AGC amplifier, 4 is a PSK demodulator, 5 is a judger, 6 is a low frequency filter, 7 is a delay circuit, 8 is a subtracter, 9 is a Linear modulator, 10 variable gain amplifier, 1
1 is an AGC amplifier, 12 is a conjugate circuit, 13 is a multiplier, 14 is a low frequency amplifier, 15 is a variable amplifier, 1
6 represents a multiplier.

Claims (1)

[Claims] 1 Transmit a digital signal through a wireless communication channel,
In the receiving communication system, there is a means for keeping the average value of the amplitude of the received input signal including the interference wave constant, and a means for demodulating the received input signal whose average value of the amplitude is kept constant and using a determiner to determine the value of the transmitted data. means for obtaining an estimated value; means for estimating and reproducing interference waves included in the received input signal from an input signal to the determiner and an output signal of the determiner; and keeping an average value of the estimated reproduced interference waves constant. and detecting the amplitude and phase of the interference wave contained in the received input signal from the correlation between the estimated reproduced interference wave whose average value is kept constant and the received input signal, and the amplitude and phase of the detected interference wave. means for controlling the amplitude and phase of the estimated reproduced disturbance wave whose average value is kept constant from the above, and means for keeping the average value of the amplitude of the received input signal constant,
means for subtracting the estimated reproduced interference wave whose amplitude and phase are controlled from the interference wave contained in the reception input signal in a negative feedback manner, so as to receive the reception input signal while removing the interference wave contained in the reception input signal. A reception method that eliminates interference waves.