The noise suppression device for satellite communication systems with code division multiplexing

 

(57) Abstract:

The device relates to electrical engineering and can be used in communication systems with code division multiplexing. Technical result achieved a high degree of suppression of interference from nearby satellite to the receiver input of the earth station with multistation access. The noise suppression device for satellite communication systems with code division of channels contains two constraints, two bandpass filters, three delay elements, four multiplier, notch filter, peak detector, the deciding unit, the control unit search unit generators reference signals. 2 Il.

The present invention relates to electrical engineering and can be applied in communication systems with code division of channels.

The known device suppressing structural interference to receivers wideband signals is described in U.S. Pat. RF N 2000662, H 04 B 1/10, N 20001525, H 04 B 1/10 and others, the lack of which is a low immunity to structural interference.

The closest in technical essence to the present invention is a device for suppressing a powerful signal in close proximity of the satellite to the receiver input earthly mill is the remote signal of the satellite, described in the article by B. N. Efimov, "evaluation of the effect of the nonlinear Converter on the robustness of reception of broadband signals in satellite networks, "Electromagnetic waves and electromagnetic systems", N 1, T. 3, 1998, page 95) adopted for the prototype.

Structural diagram of the prototype is shown in Fig. 1, where indicated:

1 - amplifier

2 - myCitadel,

3 - stop,

4 - band-pass filter.

Ustroistvo prototype contains the amplifier 1, the output of which is connected to one of inputs of vicites 2, terminator 3, the entrance of which is combined with the input of the amplifier 1 and an input device, and the output of the limiter 3 through band-pass filter 4 is connected to another input of vicites 2 whose output is the output device.

The device prototype works as follows.

The input mixture containing powerful structural interference from neighboring satellites and weak useful signal from the remote satellite passes through the amplifier 1 to one input of vicites 2 and connected in series through the limiter 3 and the band-pass filter 4 on the other input vicites 2. The amplitude of the interference at the output of the limiter 3 is equal to Uabout. In the bandpass filter 4 is the suppression of the powerful is by the limiter 3 times, resulting interference is compensated.

The disadvantage of the prototype is the low degree of suppression in the earth station interference from a nearby companion.

To eliminate this drawback in the device containing the serially connected first stop and the first bandpass filter and the input of the first limiter is an input device, connected in series introduced the first delay element, the first multiplier, the notch filter and the second multiplier, the output of which is the output device and the input of the first delay element connected to the input of the first limiter; connected in series, a third multiplier, a second band-pass filter, peak detector, the deciding unit, the control unit search unit generators reference signals, a second delay element, a fourth multiplier, a second limiter and a third delay element, the output of which is connected to another input of the second multiplier.

In addition, the output of the first bandpass filter connected to one of inputs of the third multiplier, another input connected to the output of unit generators reference signals. The output of the second bandpass filter simultaneously multiplier.

The structural scheme of the device is shown in Fig. 2, where indicated:

1, 15, the first and second limiter,

2, 8, the first and second band-pass filter,

3, 13, 16 - first, second and third delay element,

4, 6, 7, 14 - first, second, third and fourth multiplier,

5 - rejection filter,

9 is the amplitude detector

10 - the decisive block,

11 is a control block search,

12 - unit generators reference signals.

The inventive device comprises a first limiter 1 and the first delay element 3, the inputs of which are combined and input device, the output of the delay element 3 connected in series through the first multiplier 4 and the notch filter 5 is connected to one of the outputs of the second multiplier 6, the output of which is the output device.

The output of the first limiter 1 connected in series through the first band-pass filter 2, the third multiplier 7, the second band-pass filter 8, a detector 9 is connected to the input of the decision making unit 10, the output of which is connected in series through the control unit search 11 and generator unit of the reference signal 12 is connected with another input of the third multiplier 7 and at the same time through the follower of the support 16 - another input of the second multiplier 6. Thus the output of the second bandpass filter 8 is connected to another input of the fourth multiplier 14. The output of the second limiter 15 is connected both to the other input of the first multiplier 4.

The proposed device operates as follows.

The input mixture containing useful broadband signal from the remote satellite and powerful structural interference from the nearby companion, is fed to the limiter 1, where is the hard limit with subsequent filtering in the band-pass filter 2 with bandwidth equal to the width of the spectrum of the signals, code-division multiplexing. As a result, the output of filter 2 is the hindrance and depressed (by approximately 6 dB) the signal that arrives at the third multiplier 7, where the mixture is multiplied by the reference signal unit 12, which represents a code sequence similar to the code sequence used to generate broadband interfering signal in the middle of the satellite. The result of the multiplication is filtered by narrow-band filter 8, is detected by the detector 9, the result of the detection is compared with ish 11, which provides scanning the delay unit 12 in the absence of excess in the block 10 and stops it when the threshold is exceeded in block 10. In case of excess in block 10 of the reference code sequence generated by the block 12, is in synchronism with the obstacle, the output unit 8 is allocated rolled filtered obstacle, which in the block 14 again becomes broadband due to manipulation by the same reference phase code sequence block 12 is supplied to the unit 14 through the delay element 13. At the same time, the signal from the remote satellite unit 7 is not turned off, because its code sequence does not match the code sequence block 12. This means that due to the correlation processing in blocks 7,8 useful signal is suppressed in B times, where B is the base of the wideband signal.

Thus the output of block 14 estimation of the interfering signal in the middle of the satellite, and the signal of the remote satellite almost depressed. Formed evaluation of interference through the stopper 15, which provides stability of its level, is supplied to the multiplier 4, where by multiplying it with the input mixture flowing from the input device through the first element detention is e passes.

At the same time, the useful signal by multiplying the unit 4 with the assessment of the interference gets an additional phase shift keying, which is then removed in block 6 by multiplication with the same reference signal on the reference input of the unit 6 from the output unit 15 through a delay element 16. Part of extended spectrum registereda in block 5, which may lead to the loss of power of the useful signal. However, that evaluation of the interference is completely analogous to the structure of the interference in the input mix, the band rejectee unit 5 is significantly less than the bandwidth of the block 8. This means that the power loss of the output signal C<<B, where B is the base used broadband signals.

Thus the output device is allocated a useful signal from a remote satellite, and interference from nearby satellite fails.

Consider the hardware implementation of the block.

The block 12 may be made in the form of a set of generators of code similar to the code generators used on the satellites of this system. According to the equipment software guidance (NPA), has information about the location of the satellites at any given point in time to the input unit 7 podkluchili 3, 13, 16 aligns the signals in time, given the delay in the path of their processing.

In the prototype, the degree of suppression of the interference is determined by the ratio:

Up= Up-Uo,

where Upthe amplitude of the noise in the input mix,

Uabout- level limiter,

Up- - residual voltage noise at the input of myCitadel.

Due to the fact that in the prototype level has a constant value with increasing amplitude noise when approaching a decisive satellite U-value ofpgrows, that is, the degree of suppression of the interference is reduced. In addition, the use of the limiter in path formation evaluation interference suppresses weak signal no more than 6 dB. This means that part of the useful signal passes through the path of formation evaluation interference and myCitadel compensated signal in the input mixture, which leads to energy losses of the useful signal.

In addition, the effectiveness of compensation schemes decreases sharply with the increase of the spectrum of the compensated signals because of increased hardware complexity equalization signals in amplitude and time, the degree of suppression in the m correlation processing interference is the restoration of the interference, this restored the obstacle is used as the reference signal in the multiplier products 4 and 6. The multiplier is convolution noise, which registereda notch filter that provides its suppression by approximately (60 - 80) dB, the degree of suppression of the interference does not depend on the width of the spectrum of the signals.

In the proposed device are excluded energy loss of the useful signal, as in path formation evaluation interference suppression signal is not only due to the use restrictions of the input mixture, but also through the use of correlation processing interference, providing additional suppression of the signal in B times, where B is the base of the wideband signal.

The noise suppression device for satellite communication systems with code division of channels containing serially connected first stop and the first band-pass filter, the input of the first limiter is an input device, wherein the entered serially connected first delay element, the first multiplier, the notch filter and the second multiplier, the output of which is the output device and the input of the first al second band-pass filter, the amplitude detector, the deciding unit, the control unit search unit generators reference signals, a second delay element, a fourth multiplier, a second limiter and a third delay element, the output of which is connected to another input of the second multiplier and the output of the first bandpass filter connected to one of inputs of the third multiplier, another input connected to the output of unit generators reference signals, the output of the second bandpass filter at the same time is connected with one input of the fourth multiplier and the output of the second limiter - with another input of the first multiplier.

 

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FIELD: radio engineering; construction of radio communication, radio navigation, and control systems using broadband signals.

SUBSTANCE: proposed device depends for its operation on comparison of read-out signal with two thresholds, probability of exceeding these thresholds being enhanced during search interval with the result that search is continued. This broadband signal search device has linear part 1, matched filter 2, clock generator 19, channel selection control unit 13, inverter 12, fourth adder 15, two detectors 8, 17, two threshold comparison units 9, 18, NOT gates 16, as well as AND gate 14. Matched filter has pre-filter 3, delay line 4, n attenuators, n phase shifters, and three adders 7, 10, 11.

EFFECT: enhanced noise immunity under structural noise impact.

1 cl, 3 dwg

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