JPH0775326B2 - Receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver equipped with interference wave suppressing means.

[0002]

2. Description of the Related Art Conventionally, for example, B. Widrow, "Adaptive Noise Can" has been used as a receiver provided with an interference wave suppressing means.
celling "Proc. IEEE, vol.63, No.12
(1975).

FIG. 4 is a block diagram of a receiving device to which the contents disclosed in the above-mentioned document are applied. 1 is a receiving means and 2 is an interference wave suppressing means. The receiving means 1 receives the desired signal S (t) and simultaneously receives the strong interference wave I (t) from the main signal X.
(t) and the reference signal r (t), which is a signal of only an interference wave containing almost no desired wave component as compared with the main signal X (t), are received. ) And an interference wave I (t), an auxiliary antenna 7b which receives only an interference wave I (t) containing almost no desired wave component as compared with the main antenna 7a, and the main antenna 7a. The receiver 6 receives the main signal X (t) including the desired wave and the interference wave from the auxiliary antenna 7b and the reference signal r (t) from the auxiliary antenna 7b containing only the interference wave. Usually, the main signal uses the main antenna 7a with a large antenna gain, and the reference signal uses the auxiliary antenna 7b with a small antenna gain. Further, the interference wave suppressing means 2 outputs the receiver output for the main signal X (t) to A
A / D converter 5a for A / D conversion and A / D converter 5b for A / D converting the receiver output for the reference signal r (t)
, An adaptive filter 3 that approximately synthesizes the reference signal r (t) with an interference wave included in the main signal X (t), and an output signal e by subtracting the adaptive filter output signal j (t) from the main signal X (t). and a complex subtractor 4 for obtaining (t). Such an interference wave suppressing means 2 is known as a noise canceller.

Assuming that the difference between the propagation paths of the reference signal r (t) and the main signal X (t) is represented by a transfer function H (t), the transfer function W (t) of the adaptive filter 3 is H (t). When controlled so as to match t), the output signal e (t) of the interference wave suppressing means 2 becomes the desired wave signal S (t) in which the interference wave is suppressed from the main signal X (t).

The adaptive filter 3 is composed of a digital filter having M stages, and the transfer function W thereof is controlled by sequentially controlling M loads corresponding to the impulse response values of the filter based on an adaptive algorithm of the least square method.
Although (t) is brought close to the transfer function H (t) described above, the convergence time of the adaptive algorithm is required, and the convergence time increases as the required number M of stages of the adaptive filter increases. When the reception environment changes rapidly, the convergence time is hindered and the interference wave remains unremoved. Therefore, the desired wave S
It was an obstacle to the observation of (t).

[0006]

The conventional receiving apparatus provided with the interference wave suppressing means does not follow the filter optimum value due to the convergence time with respect to the rapid change of the receiving environment as described above, and thus the interference wave is suppressed. However, there was a problem that the remaining part of the wave disappeared, which hindered the observation of the desired wave.

The present invention has been made to solve the above problem, and provides an interference wave suppressing means capable of instantaneously removing an interference wave and observing a desired wave by a method that does not use an adaptive filter as described above. An object of the present invention is to provide a receiving device provided with the device.

[0008]

In order to achieve the above object, a receiving apparatus of the present invention is an envelope of a first received signal containing almost only interference waves and a second received signal containing a desired wave and an interference wave. A detector for detecting each of the lines, a signal processor having the outputs of these detectors as inputs, a high-pass filter for removing low-frequency components of the output of the signal processor, and an output of the high-pass filter. An interference wave suppressing unit having a multiplier or a mixer for multiplying the second received signal is provided. The signal processor is capable of performing a division process for receiving both detection outputs and dropping an interference wave component to a low frequency, and for example, a device including a divider can be adopted.

[0009]

In the receiver of the present invention, the main interference wave component contained in the envelope detection signal of the main signal is divided by the envelope detection waveform of the reference wave or a process substantially equivalent thereto is executed. By doing so, it is possible to suppress the interference wave instantaneously by band-compressing to almost direct current and removing by the high-pass filter, and then multiplying the output of the high-pass filter with the original main signal by the multiplier or mixer. Is.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a receiving apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the receiving apparatus of the present invention. In this figure, the receiving means 1 is the same as in the conventional case of FIG. 4, and the main signal X (t) and the reference signal r (t) are used.
The main antenna 7a which receives both the desired wave S (t) and the interference wave I (t) and the interference wave I which contains almost no desired wave component as compared with the main antenna 7a.
It has an auxiliary antenna 7b that receives only (t), and a receiver 6 that receives the main signal X (t) from the main antenna 7a and the reference signal r (t) from the auxiliary antenna 7b. Further, the interference wave suppressing means 2 has a square-law detector (envelope detector) 8 for envelope-detecting the receiver output for the main signal X (t).
a, a square-law detector (envelope detector) 8b for envelope-detecting the receiver output for the reference signal r (t), and a divider 9
And a high pass filter (HPF) 10 and a multiplier or mixer 11.

The main signal X (t) is the sum of the desired wave S (t) and the interference wave I (t) and can be expressed by the following equation. X (t) = I (t) cos {ω ₁ t + θ ₁ (t)} + S (t) cos {ωst + θs (t)} (1) where S (t), ωst and θs (t) are The amplitude, angular frequency and phase of the desired wave are respectively represented, and I (t), ω ₁ and θ ₁ (t) are respectively the amplitude, angular frequency and phase of the interference wave. θ ₁ (t) is uniformly distributed from 0 to 2π, the desired wave and the interference wave are independent of each other, and the phases and amplitudes of the desired wave and the interference wave are independent from each other. . The above equation can be further written as

[Equation 1] In the case of the present invention, the target is a case where the interference wave generation source is specified, not unspecified, and since the signal waveform of the interference wave can be obtained as known information, the reference signal r (t)
Is r (t) = k · Ia (t) cos {ω ₁ t + θ ₁ (t) + θ} (3) Here, k and θ represent the amplitude ratio and the phase difference between the interference wave and the reference signal included in the main signal X (t), respectively, and I
It can be considered that a (t) has almost the same waveform as I (t). The envelope waveform of the interference wave is the output k ² of the square-law detector 8b of the reference signal.
It can be obtained from Ia ² (t) / 2. And the divider 9
Is used to divide the output A ² of the square detector 8a for the main signal X (t) by the output of the square detector 8b for the reference signal. At this time, the output of the divider 9 is A ₁ (t) = 2A ² (t) / k ² Ia ² (t) = 2I ² (t) / k ² Ia ² (t) + 2S ² (t) / k ² Ia ² (t) +2 {2S (t) I (t) / k ² Ia ² (t)} cos {Δωt + θ ₁ (t) −θs (t)} (4) However, kIa (t) ≠ 0. Here, since I (t) and Ia (t) have almost the same waveform, the square-law detection signal A ² (t)
Since the I ² (t) term of is almost band-compressed to the DC component,
It can be removed by blocking the DC component of A ₁ (t) by the high-pass filter 10. Assuming that the amplitude of the interference wave is much larger than that of the desired wave, the output A ₂ (t) of the high pass filter 10 in FIG. 1 can be approximated as follows. A ₂ (t) = {4S (t) / k ² I (t)} cos {Δωt + θ ₁ (t) −θs (t)} (5)

Next, when this is multiplied by the main signal X (t) using the multiplier or mixer 11, the output Ya (t) is Ya (t) = {2S (t) / k} [cos {ωst + θs ( t)} + cos {ω ₁ t + Δωt + 2θ ₁ (t) −θs (t)}] (6) The first term in the above equation is the desired wave component, and the second term is the noise component. From the above equation, it can be seen that the output signal-to-interference ratio is close to 1 and shows a very large interference rejection. This is essentially because the high-pass filter 10 removes the square-law detection signal of the main signal band-compressed with the amplitude waveform of the reference signal.

Generally, when the modulation format of a desired wave is known as in radar and communication, the desired wave is converted into a spread spectrum signal, and the desired spectrum is extracted from the interference wave by demodulating the spread spectrum signal. You can Therefore, there is no practical problem that the output signal-to-interference ratio of FIG. 1 is 1.

Further, when the value of the ratio k of the amplitude magnitudes of the interference wave component of the main signal and the reference signal of the circuit of FIG. 1 suddenly changes, the first term 2I ^{2 of} A ₁ (t). (t) / k ² Ia ² (t) is not completely removed by the high-pass filter 10, and a transiently large value passes. This transient response depends on the characteristics of the high-pass filter 10 through which A ₁ (t) passes. However, even if the value of the phase difference θ between the interference wave component of the main signal and the reference signal of the circuit of FIG. 1 suddenly changes, there is no transient change. This is A
_{Since 1} (t) is a function irrelevant to θ, the interference wave rejection characteristic does not show transient deterioration with respect to changes in the phase θ.
As a result, the proposed circuit can remove the interference wave instantly even if the magnitude of the interference wave changes and the phase difference θ changes if the amplitude ratio k is constant.

FIGS. 2 and 3 show an example of the experimental results by microwaves in order to qualitatively prove the above-mentioned analysis results. However, FIG. 2 shows the main signal X (t), and FIG. 3 shows the output Ya (t) of the interference wave suppressing means. In this experiment, the desired wave gives a stable signal with a center frequency of 9000 MHz, a pulse width of 4 μS, and a repetition frequency of 50 kHz, and the interference wave has a center frequency of 900.01 MHz, which is very close to the center frequency of the desired wave. And is included in the pulse band of the desired wave. Part of the interference wave is received as a reference signal.
The center frequency of the main signal and the reference signal is 5 MHz depending on the receiver.
It is converted to an intermediate frequency of and becomes the input of the interference wave suppressing means.
The signals of these two channels were recorded as digital signals and a computer simulated the interference wave suppressing means. 2 shows that the interference wave has a modulation frequency of 10 kHz and a modulation degree of 20.
% Amplitude modulated wave, input signal-to-interference ratio is -3
X (t) at 0 dB, and FIG. 3 shows the waveform of the output Ya (t) of the interference wave suppressing means at that time. This waveform shows the same waveform even if the phase of the recorded reference signal is changed by 180 ° on the way. From this, it is understood that the present invention can almost instantaneously suppress the interference wave.

It should be noted that, instead of the antenna 7b for receiving the reference signal of the receiving means 1 of FIG. 1, the reference signal may be obtained from an interfering transmission source as a system mutually connected by a cable or wirelessly. Show the effect.

Further, it goes without saying that the interference wave suppressing means of the present invention can be implemented by digital processing, and the present invention can be applied not only to radio wave applications but also to sound wave applications.

[0019]

As described above, according to the present invention,
As the interference wave suppressing means, a detector for detecting the envelope of the main signal and the reference signal, and a signal processor such as a divider for processing the detection output of the main signal and the reference signal to reduce the interference wave component to a low frequency. And a high-pass filter that removes low-frequency components of the output of the signal processor, and an interference wave suppression unit having a multiplier (or mixer) that multiplies the filter output and the main signal, and the main signal By band-compressing the square-law detection signal of the reference signal with the amplitude waveform of the reference signal and removing by the high-pass filter what has been converted to almost a direct-current component, by multiplying this with the original main signal by a multiplier (or mixer), It is possible to obtain a receiving device equipped with an interference wave suppressing means capable of suppressing the interference wave instantaneously. The present invention also has an advantage that the circuit configuration is simple because no phase processing is required.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an embodiment of a receiving apparatus according to the present invention.

FIG. 2 is a waveform diagram showing a main signal X (t), which is an experimental result in the case of the embodiment of FIG.

3 is a waveform diagram showing an output Ya (t) of the interference wave suppressing means, which is an experimental result in the case of the embodiment of FIG.

FIG. 4 is a configuration block diagram of a conventional receiving device.

[Explanation of symbols]

 1 Receiving means 2 Interference suppressing means 3 Adaptive filter 4 Complex subtractor 8 Square detector 9 Divider 10 High-pass filter 11 Multiplier

Claims (1)

[Claims] 1. A receiver provided with an interference wave suppression means, comprising a detector for detecting an envelope of a first received signal containing almost only an interference wave and a second received signal containing a desired wave and an interference wave. , One of the detectors with the output of these detectors as input
Signal processor for dividing the output of the other detector by the output of the other detector, a high pass filter for removing low frequency components of the output of the signal processor, an output of the high pass filter and the second received signal A receiver comprising an interference wave suppressing unit having a multiplier or a mixer for multiplying by.