JPH04356824A - Transmitter/receiver - Google Patents

Abstract

PURPOSE:To exclude the observation fault of a desired received signal caused by reception interference waves interfering from the transmission side to the reception side at the transmitter/receiver to simultaneously transmit/receive pulse signals. CONSTITUTION:While providing an adaptive filter 7 to approximately synthesize the reception interference wave signal for interfering from the transmission side to the reception side, subtracting means 8 to subtract the output signal of the adaptive filter from the output signal of the receiver and median filter 12 to define the output of the subtracting means 8 as input data and to output the central value, for the carrier frequency component of the pulse signal transmitted to the adaptive filter, the other interference wave frequency component received to the median filter is suppressed. Thus, the configuration of the adaptive filter is simplified, and the suppressing performance of the reception interference waves interfering from the transmission side to the reception side is improved without increasing the convergent time of an adaptive algorithm.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art Conventionally, as a receiving apparatus equipped with an interference wave suppressing means, for example, B. Widrow: “Adaptive
e Noise Canceling “Proc.
IEEE, vol. 63, No. 12. (1975)
There are some that have been disclosed. FIG. 7 is a block diagram of a transmitting/receiving device to which the content disclosed in the above-mentioned document is applied, in which 1 is a transmitting device, 2 is a receiving device, and 10 is an interference wave suppressing means. The definitions of the signal symbols shown in the figure are as follows. Jo(
t) is a transmitted wave radiated from the transmitting element 9a of the transmitting device 1, and J(t) is a received interference wave S(t) in which a part of the transmitted wave is received by the receiving element 9b of the receiving device 2 via an unknown propagation path. ) is the desired received wave, H(z) is the transfer function of the unknown propagation path of the received interference wave, W(z) is the transfer function of the adaptive filter 7, and jo(t
) is the output signal of the transmission signal generation means 11, jo(k) is the digital signal of the transmission signal, jf(k) is the output signal of the adaptive filter 7, c(k) is the pulse timing signal of the transmission signal generation means 11, d(k) is the output signal of the receiving device 2, and e(k) is the output signal of the interference wave suppressing means 10. Note that t is a time factor, and k is a factor representing discrete time of the digital signal. In the transmitter/receiver of FIG. 7, there is a received interference wave J(t) (=unwanted wave) in which a part of the transmitted wave Jo(t) is received by the receiver via an unknown propagation path, and a desired received wave S( t) is difficult to observe, the receiver output signal d(k) is the desired received wave signal s(k) and the received interference wave signal j
(k), so the receiving device output signal d(k)
An interference wave suppression means is required for suppressing the received interference wave signal j(k) from the received interference wave signal j(k) to obtain the desired received interference wave signal s(k). As shown in FIG. 7, there is an adaptive filter 7 that approximately synthesizes received interference wave signals that interfere from the transmitting side to the receiving side, and an adaptive filter output signal jf (k) from the receiving device output signal d(k).
) and a complex subtracter 8 for subtracting the interference wave suppression means 10.
is known as a noise canceller. If we consider the unknown interference wave propagation path from the transmitting side to the receiving side as one unknown filter, and let its transfer function be H(z), then the transfer function W(z) of the adaptive filter 7 is the unknown interference wave propagation path. When the output signal e(k) of the interference wave suppressing means 10 is controlled to match the transfer function H(z) of the receiving device output signal d(
k), the desired received wave signal s(k) is obtained by suppressing the received interference wave signal j(k).

The adaptive filter 7 is composed of a digital filter with M stages, and its transfer function W ( z
) is brought close to the transfer function H(z) of the unknown interference wave propagation path, but in general, the transfer function H(z) of the interference wave propagation path is
The number of adaptive filter stages M required to simulate z) is unknown. Even if the required number of stages M of this adaptive filter is known in advance, if the number of stages M increases, the structure of the adaptive filter becomes complicated and the convergence time of the adaptive algorithm becomes longer, so there is a restriction on the number of stages M of the adaptive filter. be. In particular, when a pulse signal is used as the transmission signal, even after performing load control many times, the transfer function W(z) of the adaptive filter is the same as the transfer function H(z) of the unknown propagation path, as shown in FIG. (Figure 5 illustrates the amplitude response of the transfer function of the adaptive filter and the unknown propagation path, but the situation is similar for the phase response), and the carrier frequency f0 of the transmitted pulse signal The values of the transfer function are made to match. At this time, the output signal e(
As shown in FIG. 4(b), the received interference wave J(k) is compared with the receiver output signal d(k) shown in FIG.
The received interference wave signal j(k) is almost suppressed at times other than the time corresponding to the pulse edge of t), but at the time corresponding to the pulse edge, a large amount of the received interference wave signal remains (
(residual interference waves) were present and were an obstacle to observation of the desired received wave signal s(k).

0004

[Problems to be Solved by the Invention] In a conventional transmitting/receiving device equipped with an interference wave suppressing means, when the transmitting device and the receiving device operate simultaneously as described above and a pulse signal is used for the transmitted signal, it is difficult to receive signals from the transmitting side. There is a problem in that a large residual interference wave (residual interference wave) of the received interference wave signal interfering with the other side exists at the output of the interference wave suppression means, and this becomes an obstacle to observation of the desired received interference wave signal s(k). This invention was made to solve the above-mentioned problems, and it improves reception interference wave suppression performance without increasing the number of stages M of the adaptive filter and increasing the convergence time of the adaptive algorithm. It is an object of the present invention to provide a transmitting/receiving device equipped with an interference wave suppressing means capable of eliminating observation interference of a desired received wave signal s(k) due to received interference waves interfering from one side to the receiving side.

[0005]

[Means for Solving the Problems] In order to achieve the above object, a transmitting/receiving device according to the present invention includes an adaptive filter that approximately synthesizes received interference wave signals that interfere from a transmitting side to a receiving side, and a receiving device output signal. The present invention is characterized in that it is comprised of interference wave suppression means having subtraction means for subtracting the adaptive filter output signal, and a median filter that takes the output of the subtraction means as input data and outputs its median value.

[0006]

[Operation] In the transmitting/receiving device configured as described above, an adaptive filter is used as an interference wave suppression means to approximately synthesize received interference wave signals interfering from the transmitting side to the receiving side, and the adaptive filter output signal is converted from the receiving device output signal to the adaptive filter output signal. and a median filter that takes the output of the subtraction means as input data and outputs its median value. By suppressing components other than f0 of the received interference wave, the configuration of the adaptive filter can be simplified and the reception interference wave suppression performance can be improved without increasing the convergence time of the adaptive algorithm.

[0007]

[Embodiment] An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a transmitting/receiving device according to the present invention. 1 is a transmitting device, 2 is a receiving device, and 3 is an interference wave suppression means with a new configuration, which includes an adaptive filter 7 and subtracts the adaptive filter output signal jf (k) from the receiving device output signal d(k). A median filter 12 and an output switching means 13 are added to the conventional interference wave suppression means having a complex subtracter 8. Jo(t) is a transmission wave emitted from the transmission element 9a of the transmitting device 1 (for example, a jamming wave for the other party), while the receiving device 2 operating at the same time transmits the desired received wave through the receiving element 9b as S(t). ) (for example, communications and radar waves emitted by the other party) and controls the transmitted waves based on that information. Now, a pulse signal is used as a transmission signal, and FIG.
The receiving device output signal d(k) shown in (a) is the desired received wave signal s(k) and a received interference wave signal j(k) which is received by the receiving device through a part of the transmitted wave through an unknown propagation path. As explained in the related art, the value of the transfer function W(z) of the adaptive filter 7 is set to the carrier frequency f of the transmission pulse signal.
0 If the above is made to match the transfer function H(z) of the interference wave propagation path, e(k) of the output signal of the interference wave suppression means of the conventional configuration is
), as shown in FIG. 4(b), the received interference wave J(t)
At the time corresponding to the pulse edge of the received interference wave signal j (
k) There is a large residual interference wave. In the newly configured interference wave suppression means, the adaptive filter 7 is responsible for suppressing the carrier frequency f0 component of the received interference wave, and the newly added median filter 12 is responsible for suppressing components other than f0 of the received interference wave. As shown in FIG. 4(c), the reception interference wave suppression performance of the final output signal y(k) is improved. f(k) is the output signal of the median filter 12, y(k
) is the final output signal of the interference wave suppression means 3 of the transmitter/receiver.

FIG. 2 is a diagram showing an example of the internal configuration of the median filter 12 of FIG. 1. The median filter is a filter that outputs the number in the middle when input data (observed values a1, a2, . . . , aN) are arranged in order of magnitude, that is, the median value. 31 is an envelope detector; 32 is a divider that divides the output signal e(k) of the conventional interference wave suppression means, which is input to the median filter, by the absolute value of the output signal e(k) of the envelope detector 31; , 33 is a shift register connected to the envelope detector, 34 is a register with the same number of stages as the shift register, and 35 is a multiplier that multiplies the output value of the divider by the value in the center stage of the register. Next, the operation of the median filter 12 will be explained. When the output signal e(k) of the conventional interference wave suppression means is envelope-detected and the absolute value of the detector output signal e(k) is input to the first shift register, the contents of the i-th shift register are as follows. They are each shifted to the i+1th position. Next, the contents of the shift register 33 are rearranged in ascending order, stored in the register 34, and the value (median value) in the center stage of the register is output. As illustrated in FIG. 2, the values of the shift register 33 are 4, 2, 9, 4, 5.
When , 9, 5, 4, 4, 2 is written in the register 34.
The value in the middle row of the register, that is, 9, is sorted in ascending order.
, 5, 4, 4, 2, the median value 4 is transferred to the multiplier 35. Then, the output signal e(k) of the interference wave suppression means of the conventional configuration
When Ae exp[jφe], the output signal of the divider 32 can be expressed by the following equation. e(k)/|e(k)| =Ae exp[jφe]/|Ae exp[
jφe]|=exp[jφe] If the output value of the register 34 is Am, the output signal f(k) of the multiplier 35 is A
Since m exp[jφe], this median filter 12 preserves the phase of the input signal e(k), and at the time corresponding to the pulse edge of the transmitted wave Jo(t), e(k
) The amplitude values of the input data (each of the observed values a1, a2,..., aN output the median value (absolute value of ).

Next, the output switching means 13 of the interference wave suppression means
An example of this will be described with reference to FIGS. 1 and 3. The output switching means 13 is located at the output part of the interference wave suppressing means 3 of the transmitting/receiving apparatus of this embodiment, and is configured to change τ from the time corresponding to the pulse edge based on the pulse timing c(k) of the transmitted wave Jo(t). The switch 15 is operated for the time width, and the output signal e(k) of the complex subtracter 8 is passed through the median filter 12 to obtain the final output signal y(k). This means that the desired received wave signal s(k
) in order to minimize the distortion caused by the median filter 12. FIG. 3 is a timing chart illustrating the operation of the switch 15 of the output switching means 13 in FIG. The switch control unit 14 receives a timing signal c(k
) to generate a drive signal for the switch 15. Assuming that the output signal jo(t) of the transmission signal generation means 11 is a pulse signal, the timing signal c(k) extracted from the transmission signal generation means 11 can be expressed by the following equation.

0010

[Math 1]

c(k−n) is expressed as the above timing signal c(
Assuming that the signal is delayed by n hours (time normalized to the discrete point period) from k), the switch control unit 14 calculates the exclusive OR of the two signals c(k) and c(k−n), that is, the following Only when SW(k), which can be expressed by the formula, takes a value of 1, switch 1
5 is connected to the A side and when SW(k) takes a value of 0,
Connect the switch 15 to the B side.

0012

[Math 2]

As described above, in the interference wave suppression means 3 having a new configuration in which the median filter 12 is added to the interference wave suppression means having a conventional configuration, the adaptive filter 7 widens its transfer function W(z). It is not necessary to match the transfer function H(z) of the unknown interference wave propagation path over the frequency band, and it is only necessary to match the carrier frequency f0 of the transmitted pulse. Therefore, even if the number of stages M of the adaptive filter 7 is one, as shown in FIG. It becomes possible to match the function H(z). That is, in the interference wave suppression means 3 having a new configuration, the adaptive filter suppresses the carrier frequency f0 component of the received interference wave, and the median filter suppresses components other than f0 of the received interference wave, thereby changing the configuration of the adaptive filter 7. without increasing the convergence time of the adaptive algorithm.
In a transmitting/receiving device that improves reception interference wave suppression performance and performs simultaneous transmission and reception, it is possible to eliminate observation interference of the desired reception wave signal s(k) due to reception interference waves that interfere from the transmission side to the reception side. As shown in FIG. 1, in this embodiment, the residual feedback for calculating the weight of the adaptive filter 7 is obtained from the output signal e(k) of the complex subtracter, but interference wave suppression with a new configuration A similar effect can be achieved even if the signal is obtained from the final output signal y(k) of the means 3. Furthermore, the transmitting device 1 shown in FIG.
The and receiving device 2 are not limited to integrated transmitting and receiving devices, and the same effect can be obtained in the case of a system in which the transmitting device 1 and the receiving device 2 are separated and connected to each other by cable or wirelessly. play. Further, the transmitting/receiving device of the present invention has similar effects not only in radio wave applications but also in sound wave applications.

[0014]

According to the present invention as described above, the interference wave suppressing means includes an adaptive filter that approximately synthesizes received interference wave signals interfering from the transmitting side to the receiving side, and an adaptive filter output from the receiving device output signal. It comprises a subtraction means for subtracting a signal, and a median filter that receives the output of the subtraction means as input and outputs the median value of the input data, and shares the frequency components of the received interference waves suppressed by the adaptive filter and the median filter. This simplifies the configuration of the adaptive filter and does not increase the convergence time of the adaptive algorithm.
It is possible to obtain a transmitting/receiving device equipped with an interference wave suppressing means that can eliminate observation disturbances caused by received interference waves that interfere from the transmitting side to the receiving side.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram of an embodiment of a transmitting/receiving device of the present invention.

FIG. 2 is a diagram showing an example of the internal configuration of the median filter in FIG. 1;

FIG. 3 is a timing chart illustrating the operation of the switch in FIG. 1;

FIG. 4 is a signal waveform diagram of a main part of interference wave suppressing means of the prior art and the present invention.

FIG. 5 is a diagram showing an example of the amplitude response of a transfer function of an adaptive filter and an interference wave propagation path.

FIG. 6 is a diagram showing an example of the amplitude response of a transfer function of an adaptive filter with the number of stages M=1 and an interference wave propagation path.

FIG. 7 is a configuration block diagram of a conventional transmitting/receiving device.

[Explanation of symbols]

1 Transmitting device 2 Receiving device 3 Interference wave suppression means 7 Adaptive filter 8 Complex subtractor 9a Transmission element 9b Receiving element 11 Transmission signal generation means 12 Median filter

Claims (1)

[Claims] 1. A transmitting/receiving device equipped with interference wave suppression means, comprising: an adaptive filter that approximately synthesizes received interference wave signals interfering from the transmitting side to the receiving side; and a subtracting device that subtracts the adaptive filter output signal from the receiving device output signal. and a median filter that takes the output of the subtraction means as input data and outputs the median value thereof.