JP2003046485A - Interference wave suppression system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interference wave suppression system that reduces an adjacent frequency interference wave without causing characteristic deterioration by filter processing. SOLUTION: The interference wave suppression system of this invention includes variable gain amplifiers 4, 7 and phase shifters 5, 8 that change signals received by two antennas 1, 3 or more, power combiners 11, 12 that combine output signals from the phase shifters 5, 8 with the same signal components received by another antenna 2, desired wave level detectors 16, 19 that detect a desired wave level from the outputs of the power combiners 11, 12, interference wave level detectors 14, 21 that detect the interference wave level from the output of the power combiners 11, 12, control sections 6, 9 that controls the phase shifters 5, 8 and the variable gain amplifiers 4, 7 according to the interference wave level, differential arithmetic units 17, 22 that obtain a difference between the desired wave level and the interference wave level, and a changeover device 24 that selects an output path of the power combiners 11, 12 according to an output of a comparator 24 for comparing the results of the results of the differences of the differential arithmetic units 17, 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of suppressing an adjacent frequency interference wave in a narrow band wireless receiver using a digital modulation method.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, a device of this type has a receiving antenna 27 for receiving a received wave and a desired wave pass filter 2 for extracting only a desired signal wave from the received wave.
8. The demodulator 26 demodulates this signal wave. This device requires a steep cutoff characteristic in order to remove an interference wave located at an adjacent frequency. In digital modulation wireless communication, in order to reduce intersymbol interference of a desired signal, a filter used here usually has a roll-off characteristic. However, it is difficult to reproduce an accurate roll-off characteristic in the frequency band of the filter provided before demodulation, which causes waveform deterioration. Therefore, in order to solve this problem, as shown in FIG. 3, roll-off filtering processing may be performed by the A / D converter 29 and the desired wave passing digital filter 30 in a band after demodulation that facilitates accurate filter characteristics. is there. Generally, the desired wave passing digital filter 30 performs digital filtering processing after being taken in by the A / D converter 29. Therefore, when the level of the interfering wave is higher than the level of the desired wave, the desired wave is passed through by saturation of the A / D converter 29. In some cases, it is difficult to limit the band without damaging the signal component of the wave.

[0003]

As described above, in the above-mentioned conventional apparatus, the filtering process is performed to remove the adjacent frequency interference wave. However, when the band is limited before demodulation, the approximation accuracy of the roll-off characteristic is reduced. However, if the band is limited after demodulation, there is a problem that the expected interference wave removing effect cannot be obtained depending on the level of the interference wave.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an interference wave suppressing method for reducing an adjacent frequency interference wave without giving a characteristic deterioration due to a filtering process.

[0005]

In order to achieve the above object, the present invention provides at least three or more receiving antennas and at least one of the receiving antennas in the interference wave suppressing method of a radio receiving apparatus using a digital modulation method. A variable gain amplifier that changes the amplitude of a signal received by two or more reception antennas, a phase shifter that changes the phase, a signal of the phase shifter output, and another reception whose phase is different from the phase shifter output. A plurality of power combiners that combine the same received signal components received by the antenna, a desired wave pass filter that passes only desired frequency components from the output of the power combiner, and an interfering wave frequency from the output of the power combiner An interference wave pass filter that passes only the component, a desired wave level detector that detects the level of the desired wave extracted by the desired wave pass filter,
An interference wave level detector that detects the level of the interference wave extracted by the interference wave pass filter, and a control unit that controls the phase shifter and the variable gain amplifier according to the level detected by the interference wave level detector. A difference calculator for obtaining the difference between the level detected by the desired wave level detector and the level detected by the interfering wave level detector, a comparator for comparing the results of the difference calculators, and the comparator And a switching device that selects the output path of the power combiner according to the result of (1).

According to the present invention, in the interference wave suppression system, the receiving antennas are arranged so that the arrival phases of the interference waves are different from each other, and the phases of the received waves received by at least three or more receiving antennas are different from each other. As shown in the above figure, the interference wave frequency components are detected from each combined wave, the amplitude and phase amount of the signal before combining are controlled to cancel the interference wave frequency components after combining, and It is characterized in that a desired wave-to-interference wave power ratio is detected by detecting a desired wave frequency component and an interfering wave frequency component, and a composite wave having a larger desired wave-to-interference wave power ratio is selected.

According to the present invention, three or more receiving antennas are installed in a spatial arrangement having no correlation with each other, and among the paths of the receiving waves received by the respective receiving antennas, the phase of the interfering wave passing through at least three paths is Make each different. The composite wave is generated by using two or more paths among the respective paths. Here, the composite wave is two or more, and the composite paths are combined so that the respective composite phases are different. At this time, at least one path before combining includes a phase shifter so that the phase of each combined wave can be changed, and at least one path includes a variable gain amplifier so that the signal amplitude of the interfering wave before combining can be changed. Let's assume.

From each composite wave, only the frequency component of the interfering wave whose frequency is known is detected, and the phase shifter and the variable gain amplifier are controlled so that this component is suppressed.
In general, the desired wave and the interfering wave are emitted from different transmitting antennas, so there is no spatial correlation, and the phase difference between the receiving waves arriving at the respective receiving antennas is different between the desired wave and the interfering wave. Therefore, if interfering waves of the same amplitude are combined in anti-phase, it is possible to make the post-combining power ratio larger than the desired wave-to-interfering wave power ratio before combining, so the phase and amplitude control suppresses the interfering wave components. can do.

When the arrival phase difference between the desired wave and the disturbing wave with respect to each receiving antenna is small, the level of the receiving wave is also lowered by synthesizing the disturbing wave components in anti-phase, and the degree of suppression of the disturbing wave is greatly improved. Without doing so, the desired wave-to-noise power ratio also deteriorates. Therefore, the desired wave component and the disturbing wave component of which the frequency is known are detected from each of the synthesized waves, the desired wave to the disturbing wave power ratio of each synthesized wave is obtained, and the desired wave pair is calculated by comparing them. Select a composite wave with a larger interference wave power ratio.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a first receiving antenna, 2 is a second receiving antenna, 3 is a third receiving antenna, and 4 is the above-mentioned first receiving antenna. A first variable gain amplifier 5 for varying the level of the signal received by one reception antenna 1 is a first phase shifter (φ) for changing the phase of the signal output by the first variable gain amplifier 4. :
Phase shifter 6 is a first control unit (CNT: Controller) for controlling the first variable gain amplifier 4 and the first phase shifter 5, and 7 is the third receiving antenna 3. A second variable gain amplifier for changing the level of the received signal, 8 is a second phase shifter (φ: Phase shifter) for changing the phase of the signal output from the second variable gain amplifier 7, and 9 is A second control unit (CNT) for controlling the second variable gain amplifier 7 and the second phase shifter 8;
Reference numeral 10 denotes a power divider (DIV) for distributing a signal received by the second reception antenna 2.
der), 11 is a first power combiner (CMB) for combining the output of the first phase shifter 5 and the output of the power distributor 10, and 12 is the second phase shifter. 8 and the output of the power divider 10 are combined into a second power combiner (CMB: Power).
combiner), 13 is the first power combiner 1
1st interference wave pass filter (U: Undesired) which passes only an interference wave frequency component from the output signal of 1.
Reference numeral 4 denotes a first interfering wave level detector for detecting the output signal level of the first interfering wave passing filter 13, and 15 passes only the desired wave frequency component from the output signal of the first power combiner 11. First desired wave pass filter (D:
Desire), 16 is a first desired wave level detector for detecting an output signal component of the first desired wave pass filter 15, and 17 is an output level of the first desired wave level detector 16 and the first desired wave level detector 16. A first difference calculator 18 for calculating the difference level of the output levels of one interference wave level detector 14,
Is a second desired wave pass filter (D: Desire) that passes only the desired wave frequency component from the output signal of the second power combiner 12, and 19 is the output signal component of the second desired wave pass filter 18. A second desired wave level detector for detecting, 20 is a second undesired wave pass filter (U: Undesired) which passes only undesired wave frequency components from the output signal of the second power combiner 12, and 21 is A second interfering wave level detector for detecting the output signal level of the second interfering wave pass filter 20, and 22 an output level of the second desired wave level detector 19 and the second interfering wave level. A second difference calculator for calculating the difference level of the output level of the detector 21, and a comparator 23 for comparing the output of the first difference calculator 17 and the output of the second difference calculator 22 ( CM : Comparator), 2
Reference numeral 4 denotes a switch (SW) for selecting the output signal of the first power combiner 11 or the second power combiner 12 using the output signal of the comparator 23.
Reference numeral 25 is a third variable gain amplifier for changing the level of the output signal of the switch 24, and 26 is a demodulator (DE) for demodulating the output signal of the third variable gain amplifier 25.
M: Demodulator).

This device utilizes the fact that the phase difference between the reception waves arriving at the first reception antenna 1, the second reception antenna 2, and the third reception antenna 3 is different between the desired wave and the interfering wave frequency. It is a thing. The reception wave received from the second reception antenna 2 is guided to the power distributor 10, and one reception wave distributed by the power distributor 10 passes through the variable gain amplifier 4 and the phase shifter 5, and the first reception The received wave received from the antenna 1 is combined with the first power combiner 11, and the power distributor 1
The other received wave distributed by 0 is combined with the received wave received from the third receiving antenna 3 that has passed through the variable gain amplifier 7 and the phase shifter 8 by the second power combiner 12.

In the initial state, the first power combiner 11
The composite wave output from the device includes a desired wave frequency component and an interfering wave frequency component. Of these, the level of the interfering wave is detected by the first interfering wave pass filter 13 and the first interfering wave level detector 14, and the first variable gain amplifier 4 and the first interfering wave amplifier 4 are provided so as to minimize the level of the interfering wave. Phase shifter 5
Is controlled by the first controller 6. That is, the output of the power distributor 10 and the first phase shifter 5 for the interference wave frequency component
Of the first control unit 6 so that the outputs of
The interference wave component appearing in the output of the first power combiner 11 is canceled by controlling by.

Similarly, the composite wave output from the second power combiner 12 contains a desired wave frequency component and an interfering wave frequency component. Of these, the level of the interfering wave is set to the second interfering wave pass filter 20 and the second interfering wave level detector 21.
The second control unit 9 controls the second variable gain amplifier 7 and the second phase shifter 8 so that the interference wave level is minimized. That is, by controlling the output of the power distributor 10 and the output of the second phase shifter 8 with respect to the interference wave frequency component by the second control unit 9 so as to have the same amplitude and opposite phase, the second power combining is performed. The interference wave component appearing at the output of the container 12 is canceled.

When the phase difference between the desired wave and the interfering wave is small, the level of the desired wave is lowered by synthesizing the interfering wave components in reverse phase, and the degree of suppression of the interfering wave is not improved so much. Therefore, the output of the first difference calculator 17 that calculates the difference between the output of the first desired wave level detector 16 and the output of the first interfering wave level detector 14 and the second desired wave level detection The second difference calculator 22 which calculates the difference between the output of the device 19 and the output of the second interfering wave level detector 21.
Of the desired wave pair by selecting the output of the power combiner 11 or 12 having the larger difference amount, that is, the one having the larger phase difference between the desired wave and the interfering wave by the switch 24. Expand the interference wave power ratio.

The output of the switch 24 is amplified by a third variable gain amplifier 25 to a specified level, and this signal is demodulated by a demodulator 26.
By demodulating with, the signal can be reproduced without suppressing the transmission characteristics of the desired wave while suppressing the interfering wave.

Although the embodiment shown in FIG. 1 describes the case where three antennas are used, when the number of antennas is four or more and the number of antennas is increased and the number of reception wave synthesis and detection paths is increased. In some cases, it may be possible to select a path in which the phase difference between the desired wave and the interfering wave becomes larger, so that the desired wave to interfering wave power ratio may be further improved.

Further, when the system from the antenna to the switch and the detection system are installed in parallel, it is possible to cope with a plurality of interfering waves.

Further, by limiting the gain control amount of the first variable gain amplifier 4 and the second variable gain amplifier 7, it is possible to suppress the reduction of the signal-to-noise power ratio for the desired wave. .

[0020]

As described above, according to the present invention, it is possible to suppress the interfering wave without installing a filter in the main signal transmission system, so that the transmission characteristics of the filter device may be deteriorated. Lost.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an interference wave suppression system according to the present invention.

FIG. 2 is a configuration block diagram showing an example of a conventional interference wave suppression method.

FIG. 3 is a configuration block diagram showing another example of a conventional interference wave suppression method.

[Explanation of symbols]

1 First receiving antenna 2 Second receiving antenna 3 Third receiving antenna 4 First variable gain amplifier 5 First phase shifter 6 First control unit 7 Second variable gain amplifier 8 Second phase shifter 9 Second control unit 10 Power distributor 11 First power combiner 12 Second power combiner 13 First interference pass filter 14 First disturbance level detector 15 First desired wave pass filter 16 First desired wave level detector 17 First difference calculator 18 Second desired wave pass filter 19 Second desired wave level detector 20 Second interference wave pass filter 21 Second interference level detector 22 Second difference calculator 23 Comparator 24 switch 25 Third Variable Gain Amplifier 26 Demodulator 27 Reception antenna 28 Desired wave pass filter 29 A / D converter 30 Desired wave pass digital filter

Claims (2)

[Claims] 1. A method of suppressing an interference wave of a radio receiving apparatus using a digital modulation method, wherein the amplitude of a signal received by at least three or more receiving antennas and at least two or more receiving antennas of the receiving antennas is changed. A variable gain amplifier and a phase shifter that changes the phase, a signal of the phase shifter output, and a plurality of signals that combine the same reception signal component received by another reception antenna whose phase is different from that of the phase shifter output. A power combiner, a desired wave pass filter that passes only a desired frequency component from the output of the power combiner, an interference wave pass filter that passes only an interference wave frequency component from the output of the power combiner, and the desired wave pass filter A desired wave level detector that detects the level of the desired wave extracted by the filter, and a level of the interference wave extracted by the interference wave pass filter A harmful wave level detector, a control unit for controlling the phase shifter and the variable gain amplifier according to the level detected by the disturbing wave level detector, a level detected by the desired wave level detector and the disturbing wave A difference calculator that obtains the difference between the levels detected by the level detector, a comparator that compares the results of the difference calculators, and a switch that selects the output path of the power combiner according to the results of the comparators. An interference wave suppression system characterized by comprising: 2. The receiving antennas are arranged so that the arrival phases of the interfering waves are different from each other, and the receiving waves received by at least three or more receiving antennas are:
Multiple signals are synthesized with different phases, the interference wave frequency component is detected from each synthesized wave, and the amplitude and phase amount of the signal before synthesis are controlled to cancel the interference wave frequency component after synthesis. The desired wave-to-interference wave power ratio is expanded by detecting the desired-wave frequency component and the interfering-wave frequency component from each of the waves and selecting the composite wave with the larger desired-to-interference wave power ratio. The interference wave suppression method according to claim 1.