JPS6216581B2 - - 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 channel in digital transmission in wireless communication. BACKGROUND ART Recently, especially in the field of military communications, there has been a need for a communication system or a reception system that can continue communication even in the face of strong radio wave interference. this is
ECCM (Electronic Counter Counter)
It is also called anti-jamming communication (measure) or anti-jamming communication and is considered a strategically essential function in electronic warfare.
The ultimate form of such anti-jamming communication is SS.
(Spread Spectrum) method, but currently or in the near future,
It is considered to be quite difficult to effectively apply the SS method to a method for communicating multiplexed high-speed (approximately 1 Mbps or higher) data signals in real time. Therefore, an object of the present invention is to reduce as much as possible the probability of communication failure due to interference, regardless of the communication method used for digital transmission, even when strong damage prevention radio waves are applied to a wireless communication path. It is about providing the means. According to the present invention, in digital transmission in wireless communication, a first antenna that mainly receives desired waves, a second antenna that mainly receives interfering waves, and the amplitude of the signal received by the first antenna are automatically adjusted. a first automatic amplitude control means that automatically controls the amplitude of the signal received by the second antenna to emit a first output having a constant average amplitude; and a second automatic amplitude control means for emitting a constant second output; and an amplitude for emitting a third output by controlling the phase and amplitude of the second output by a control signal related to the interference wave to be removed. a phase control means, the first output and the third output;
a subtraction means for taking a difference between the outputs of and outputting a fourth output; a synchronous detection demodulation means for synchronously detecting and demodulating the generated fourth output to generate a fifth output; and a base for the fifth output. an interference wave reproducing unit that detects an interference wave component included in a band signal and reproduces an estimated interference wave; and a correlation that obtains a correlation between the reproduced estimated interference wave and the second output, and issues the output as the control signal. A calculation means is provided, and an interference wave removal reception system is obtained in which the fifth output is used as a device data output. Next, a detailed explanation will be given with reference to the drawings. FIG. 1 is a block diagram of the basic configuration of the interference wave removal reception system according to the present invention. The basic configuration and operation of this system will be explained below based on FIG. In FIG. 1, 1 is a main antenna provided mainly for the purpose of receiving the desired wave _S1 , and 2 is a sub antenna provided mainly for the purpose of receiving the interference wave _X2 . The antennas 1 and 2 have their respective directional characteristics adjusted to achieve the above purpose, and are installed with an appropriate spatial distance between them. However, in reality, despite the above purpose, the main antenna 1 receives the interference wave X ₁ and the sub antenna 2 receives the desired wave S ₂ . 3 corresponds to the high frequency section of a normal heterodyne receiver, and internal 4 and 5
These are all so-called reception frequency converters composed of a high frequency converter, a frequency converter, an intermediate frequency converter, etc., and 6 is a local oscillator. Although the high frequency section 3 needs to have sufficient linearity with respect to the expected intensity of disturbance waves and has a protection function against destruction and saturation phenomena as necessary, it is essentially not directly related to the present invention. Since this is an unrelated part, the details will be omitted. Further, 7 is an automatic gain control circuit (hereinafter referred to as AGC circuit) that amplifies the intermediate frequency output (s ₁ + x ₁ ) of the receiving frequency converter 4 to a required constant level, and 8 is also the intermediate frequency output of the receiving frequency converter 5. This is an AGC circuit that amplifies (s ₂ + x ₂ ) to a required constant level.
A subtraction (or addition) circuit 9 is used to remove interference wave components from the output of the AGC circuit 7. 1
0 is an amplitude and phase control circuit for controlling the amplitude and phase of the output of the AGC circuit 8 using a control signal a representing a correlation output, which will be described later. Reference numeral 11 denotes a demodulation section using a synchronous detection method, which includes an AGC circuit, a carrier recovery circuit, a clock recovery circuit, a baseband converter (synchronous detector), an identification circuit, and the like. Reference numeral 12 denotes an interference wave reproducing section that detects and reproduces interference wave components contained in the output of the demodulator 11. 13 is AGC
This is a correlation calculation unit that detects the correlation between the output of the circuit 8 and the estimated regenerated wave output of the circuit 12 and generates the control signal a (described above) for controlling the amplitude and phase control unit 10. To explain the basics of the operation in the above configuration, the AGC circuit 7 receives the signal from the main antenna 1.
The interference wave component included in the output of After being controlled by the correlation output with the interference component contained in the output of the AGC circuit 8, the amplitude and phase controlled output is automatically removed by subtracting it from the output of the AGC circuit 7 in the subtracter 9. . Figure 2 shows the interference wave removal circuit in Figure 1 (reference numbers 7, 8, 9, 10, 11, 1).
2 and 13) is a diagram showing a more specific configuration, and the operation of this system will be explained in detail below with reference to FIG. 2. In Figure 2, s ₁ , x ₁ , s ₂ , x ₂ are the same as in Figure 1, and s ₁ is the main antenna (1 in Figure 1).
s ₂ is the desired wave received by the auxiliary antenna ( ₂ in Figure 1) and converted to the intermediate frequency, x ₂ is the desired wave that is also the interference wave, It is showing. Now, if these signals are specifically expressed using analytical signals, they can be expressed as follows. However, in formula (1), a ₁ is the amplitude of s ₁ (effective value, the same applies hereinafter), b ₁ is the amplitude of x ₁ , a ₂ is the amplitude of s ₂ , b ₂ is the amplitude of x ₂ , and A(t) is the baseband modulation signal (complex number) of s ₁ and s ₂ and represents the average value. <|A(t)| ² > is normalized to 1,
B(t) is the baseband modulation signal (complex number) of x ₁ and x ₂ , <|B(t)| ² > is normalized to 1, and ω _a is the central angular frequency of s ₁ and s ₂ , ω _b is
The central angular frequency of x ₁ and x ₂ , θ represents the phase difference between s ₁ and s ₂ , and φ represents the phase difference between x ₁ and x ₂ . First, a case will be considered in which the subtracter 25 and the multiplier circuit 26 (=passband×control signal) are separated (open loop). Assuming that the average value of the output of the intermediate frequency (passband) variable gain amplifier 21 is normalized to 1 by the AGC amplifier 22, becomes. Here, the second term on the right side represents the interference wave component. The signal of this equation (2) is applied to an intermediate frequency (passband) variable gain amplifier 27 through a subtracter 25, and its output is normalized by an AGC amplifier 28 so that the average value is 1. Consider that in the case of an open loop, the form is the same as equation (2) without changing, and it is added to the demodulator 29 of the coherent detection method. This demodulation section includes a carrier recovery circuit, a clock recovery circuit, a baseband converter (synchronous detector), and the like. For convenience of explanation, an open loop state in which no negative feedback operation is performed, that is, a state in which the connection between the subtracter 25 and the multiplier circuit 26 is opened in FIG. 2 will be described first. Since there is no negative feedback effect at this time, assuming that the interference wave is initially very small and that a ₁ ≫ b ₁ ...(3) holds, that is, the amplitude of s ₁ is sufficiently larger than the amplitude of x ₁ , and the demodulation Consider the case where the function of section 29 is not disturbed by x ₁ . Note that the relationship in equation (3) is automatically established in a closed loop state in which the subtracter 25 and the multiplier circuit 26 are connected because negative feedback is performed (described later). Demodulator 29
The carrier playback and baseband conversion functions of
Since the input signal in (2) is multiplied by γe ^-j 〓 ^at (γ: proportionality constant), the output is, for convenience,

As [formula], Then, using the relationship of equation (3), approximately becomes. This equation (5) is determined by the identification circuit 30 as A^(t) [estimated transmission data]...(6). Based on the assumption of equation (3), A^(t) is the sampling point t=nT (T is the transmission data interval,
n is an integer, n=-∞, ......, 0, ......+∞)
almost coincides with A(t). Since the output of the subtractor 31 is the difference between equation (5) and equation (6), becomes. Using equation (7) as a baseband signal, the linear modulation circuit 3 uses the carrier reproduced by the demodulation section 29.
When converted to a passband signal in step 2, the output is The resultant signal is added to the multiplication circuit 33 (=passband×passband). On the other hand, the intermediate frequency variable gain amplifier 23
If s ₂ + x ₂ is normalized to 1 by the AGC amplifier 24, then the output of the amplifier 23 is This equation (9) is applied to the multiplication circuit 26 and at the same time is applied to the multiplication circuit 33 via the delay circuit 34 and the complex conjugate circuit 35. The delay amount of the delay circuit 34 is to equalize the difference in electrical delay time between the circuit groups 27, 29, 30, 31, 32 and the complex conjugate circuit 35, but in calculation, the delay time difference is not equalized. It has been omitted as such. Therefore, the output of the complex conjugate circuit 35 becomes the complex conjugate of equation (9). becomes. However, * means complex conjugate. The correlation calculation in the multiplication circuit 33 is expressed as equation (10) x equation (8), that is, becomes. As explained earlier, if there is a relationship such that a ₁ ≫ b ₁ in equation (3), the received data in equation (4) is correctly determined, and the estimated transmission data A^(t) in equation (6) is the transmission data. A
It almost coincides with (t). Also, the gate circuit 36
In this case, the output of the multiplier circuit 33 is passed only in the vicinity of t=nt, and is blocked except in the vicinity of t=nT.
It has the function of Therefore, Equation (11) is sampled by the gate circuit 36 only in the vicinity of t = nT, and becomes A(t) - A^(t) = 0 [in the vicinity of t = nT] ...(12) Therefore, the output of the gate circuit 36 is in the vicinity of t=nt and other than in the vicinity of this t=nT. and are integrated by the integrating circuit 37 (=low frequency generator). Assumptions in formula (1) and A
Since (t) and B(t) are generally considered to be uncorrelated, holds true, and the output of the integrating circuit 37 is It takes the form of However, α is a proportionality constant. Equation (15) is multiplied by K/α (constant multiplication) by the DC amplifier circuit 38, The result is multiplied by the multiplication circuit 26. Multiplier circuit 2
Since the output of 6 is equation (16) x equation (9),
in open loop becomes. It can be seen that the second term in equation (17) is a multiple of the second term (interference wave component) on the right side of equation (2) that is added to the subtracter 25. In equation (17), K'=K·b ₂ ² /a ₂ ² +b ₂ ² (18), then K' can be considered as an open-loop gain related to interference wave removal. Next, considering the state of the closed loop connected between the subtracter 25 and the multiplier circuit 26, if the value of K can be selected so that K'≫1...(19) is satisfied, then Equation (18) If the value of K can be selected so that K≫1+a ₂ ² /b ₂ ² (19a), negative feedback is generated in the subtracter 25 in the direction of removing the interference wave component x ₁ from the input signal s ₁ + x ₁ . It takes. At that time, the output of the multiplier circuit 26 corresponding to equation (17), that is, the product of equation (16) and equation (9) in the closed loop is becomes. Since the second term of equation (20) becomes K'/1+K'→1 when the condition of equation (19) is satisfied, it is almost equal to the second term of equation (2), and the interference wave is removed. be done. For example, if we try to guarantee the operation of the present invention until the interference wave and the signal wave are almost equal in the sub antenna 2 in Fig. 2, a ₂ ² /b ₂ ² = 1, so K = 200 (times)
Then, K' = 200 x 1/2 = 100 (times), so the interference wave will be compressed to 1/100 by negative feedback. After such negative feedback is applied, the condition of equation (3) that a ₁ ≫ b ₁ is canceled, and it is possible to continue communication while removing the interference waves. The discussion up to this point has been based on the assumption that the directivity characteristics of the main antenna 1 in FIG. 1 are adjusted to mainly receive desired waves, and the auxiliary antenna 2 in FIG. 1 is adjusted to mainly receive interference waves. In particular, relatively sophisticated beam control technology is required to adjust the directivity characteristics of the sub-antenna so that the interference waves are always maximized. FIG. 3 is a diagram showing the basic configuration of the interference wave removal reception method according to the present invention when the roles of the main antenna and sub-antenna in FIG. 1 are replaced by space diversity antennas conventionally used in the field of diversity communication. It is. In FIG. 3, 41 and 42 are antennas similar to those conventionally used for space diversity. The desired wave received by the antenna 41 is S′ ₁ and the interference wave is S′ 1 .
Let X' ₁ be the desired wave received by the antenna 42, S' ₂ be the desired wave, and X' ₂ be the interference wave. 43 is the same high frequency section as 3 in FIG. 44 and 45 are 7 in Figure 1,
This is an interference wave removal circuit corresponding to 8, 9, 10, 11, 12, and 13, and is shown as a specific embodiment in FIG. 46 and 47 are monitoring circuits that monitor the quality of demodulated data, and output analog or digital amounts depending on the quality. 48 is a data selection circuit that compares and determines the outputs of the monitoring circuits 46 and 47 and outputs data of better quality. Monitoring circuit 4
6 and 47 and the data selection circuit 48 in terms of circuits, the monitoring circuit may be an eye monitor circuit that monitors the eye pattern of the demodulated output and outputs a route with a low probability that the eye will collapse (close). , a frame synchronization circuit that detects frame bits periodically inserted into transmitted data on the receiving side and outputs the route with a high probability of being detected, or quality monitors one of the multiplexed PCM channels. bit error rate BER (Bit
A BER monitoring circuit is used that measures the Error Rate) and outputs the route with the best BER as data (the circuits become more complex in the order of description, but the judgment becomes more accurate), and as the data selection circuit 48, for example, determining the two inputs and selecting the output of the interference wave removal circuit section 44 or 45 corresponding to the better input;
An IC switch circuit is used that issues a selection output as a data output. Note that s′ ₁ , x′ ₁ , s′ ₂ , x′ ₂ are
It represents S' ₁ , X' ₁ , S' ₂ , and X' ₂ converted into intermediate frequencies by the high frequency section 43, respectively. The operating principle of the device shown in FIG. 3 will be explained below. The interference wave removal circuit section 44 uses s' ₁ +x' ₁ as an input to the AGC circuit 7 in FIG. 1 (21 in FIG. 2) and s' ₂ +x ' ₂ is AGC circuit 8 in Figure 1
(23 in Figure 2), and the interference wave elimination circuit section 45 receives s' ₂ + x' ₂ as an input to the AGC circuit 7 in Figure 1, and s' ₁ + x' ₁
receive interference waves as inputs to the AGC circuit 8 in FIG. 1, and supply data outputs to the data selection circuit 48, respectively. The data selection circuit 48 determines the quality monitoring outputs of the monitoring circuits 46 and 47 and outputs data with good quality. In other words, the configuration shown in FIG. 3 can also be interpreted as a space diversity reception system with an interference wave removal function. In this configuration,
Even if the signal processing in the interference wave removal circuit section 44 cannot be performed due to a decrease in _x'2 , the interference wave removal circuit section 45
Even if the signal processing in the interference wave removal circuit section 45 cannot be performed due to a decrease in x' ₁ , the signal processing in the interference wave removal circuit section 44 is performed, and communication is carried out while removing interference waves. It is possible to continue. Figure 3 shows the case of double space diversity, but it can be easily extended to the case of quadruple diversity combining frequency diversity by using space diversity sets and data selection circuits for each frequency. be able to. As explained above, by using the reception method according to the present invention, even when strong jamming radio waves are applied to a wireless communication channel, communication becomes impossible due to interference compared to a reception method to which the present invention is not applied. It becomes possible to perform digital transmission that dramatically reduces the probability that this will occur.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the basic configuration of the interference wave elimination reception system according to the present invention, FIG. 2 is a diagram showing the configuration of a specific embodiment of the interference wave elimination circuit section in FIG. 1, and FIG. FIG. 1 is a basic configuration diagram of an interference wave removal reception method using a space diversity antenna according to the present invention. Explanation of symbols: 1 is the main antenna, 2 is the auxiliary antenna, 3 is the part corresponding to the high frequency part of the heterodyne receiver, 4 and 5 are the reception frequency conversion part, 6 is the local oscillator, 7 and 8 are the AGC circuit, 9 is the part corresponding to the high frequency part of the heterodyne receiver Subtraction (or addition) circuit, 10 is an amplitude phase control circuit, 11 is a synchronous detection demodulation section, 12 is an interference wave regeneration section, 13 is a correlation calculation section, 43 is a high frequency section, 44 and 45 are both interference wave removal circuit section, 46 and 47 are monitoring circuits;
48 represents data selection circuits.

Claims (1)

[Claims] 1. In digital transmission in wireless communication, a first antenna that mainly receives desired waves, a second antenna that mainly receives interfering waves, and an amplitude of the signal received by the first antenna are used. a first automatic amplitude control means for automatically controlling and emitting a first output having a constant average value of amplitude; and a first automatic amplitude control means for automatically controlling the amplitude of the signal received by the second antenna to generate a first output having a constant average value of amplitude. a second automatic amplitude control means for emitting a second output with a constant value, and controlling the phase and amplitude of the second output;
amplitude and phase control means that outputs a third output under control using a control signal related to the interference wave to be removed; and subtraction means that calculates the difference between the first output and the third output and generates a fourth output. and synchronous detection and demodulation means for synchronously detecting and demodulating the emitted fourth output to generate a fifth output, and detecting an interference wave component included in the baseband signal of the fifth output and generating an estimated interference wave. an interference wave reproducing unit that reproduces the estimated interference wave, and a correlation calculation unit that obtains a correlation between the reproduced estimated interference wave and the second output and issues the output as the control signal, Interference wave removal reception method for output. 2. In digital communication in wireless communication, the amplitude of a signal received by a first antenna, a second antenna, and the first antenna is automatically controlled to produce a first output with a constant average value of the amplitude. The first thing to emit
automatic amplitude control means, a second automatic amplitude control means for automatically controlling the amplitude of the signal received by the second antenna and emitting a second output having a constant average value of amplitude; and the second output. amplitude phase control means for controlling the phase and amplitude of the signal by a control signal related to the interference wave to be removed to generate a third output; subtraction means for generating an output; synchronous detection and demodulation means for synchronously detecting and demodulating the generated fourth output to generate a fifth output; and detecting an interference wave component contained in the baseband signal of the fifth output. a first interference wave removal circuit section having an interference wave reproducing means for reproducing the estimated interference wave; and a correlation calculation means for obtaining a correlation between the reproduced estimated interference wave and the second output and emitting the output as the control signal; and has substantially the same configuration as this first interference wave removal circuit section, but the first automatic amplitude control means is arranged to control the amplitude of the signal received by the second antenna, and the first automatic amplitude control means is arranged to control the amplitude of the signal received by the second antenna. 2
a second automatic amplitude control means arranged to control the amplitude of the signal received by the first antenna;
and monitoring means for monitoring the quality of a fifth output of the first interference removal circuit and a sixth output corresponding to the fifth output of the second interference removal circuit. , data selection means for selecting an output with better quality from the monitored fifth and sixth outputs, and an interference wave removal reception in which the selected output with better quality is used as the device data output. method.