Digital filtering system and method for long-term interference signals

Abstract

The application discloses a digital filtering system and method for long-time interference signals, which comprises a clock unit, a synchronization unit, a window sampling unit, a window width setting unit, a consistency judging unit and an output unit, wherein the synchronization unit, the window sampling unit, the consistency judging unit and the output unit are sequentially connected, and the clock unit is connected with the synchronization unit, the window sampling unit, the consistency judging unit and the output unit respectively. The application has the advantages that the long-time interference signals can be filtered, the interference signals with specific duration can be filtered without affecting normal signals, the filtering accuracy is high, and the filtering time can be accurately adjusted.

Description

TECHNICAL FIELD

[0001] The present application relates to the interference processing during the signal transmission between avionics, in particular, a digital filtering system and method for long-time interference signal. BACKGROUND

[0002] In the field of avionics, the avionics usually communicate by using discrete switch signals, and the signal format is generally "28V / open circuit" or "ground / open circuit", in which "28V" or "ground" is the effective signal, and "open circuit" is the invalid signal. When the signal is in the "open circuit" state, the signal line is extremely easy to pick up the electric field interference because the source end and the receiving end are both high resistance. Moreover, if the signal line is bundled together with other conductors to form a cable bundle, the inductive coupling between the lines makes the signal line easy to induce interference voltage. When there is a signal with large current rate of change (such as a relay, contactor or motor starting or stopping) in the cable bundle, a sharp pulse voltage will be induced on the signal line, which has a peak value much larger than 28V and a duration of tens of milliseconds, interfering with the normal signal. In order to ensure the normal operation of the equipment, the interference signal needs to be filtered.

[0003] The interference is reflected in two aspects: voltage amplitude and duration. Generally, for amplitude interference, clamping measures can be used to reduce the amplitude of the interference signal, but clamping cannot suppress the amplitude of the interference signal below the amplitude of the normal signal. When the interference signal arrives, the interference signal and the effective signal cannot be distinguished in terms of voltage amplitude. Therefore, filtering needs to be performed in terms of time: since the duration of the interference signal is shorter than that of the effective signal, filtering the signal with short duration can filter out the interference. The traditional method is to use RC integration circuit with comparator or Schmidt trigger, which is realized by using an analog scheme, and the integration time is determined by the parameters of the resistor and capacitor. Due to the large error and drift of the capacitor, the analog scheme has the problems of inaccurate timing, large drift, difficult parameter adjustment, high circuit complexity, especially for long-time interference signals, the RC time constant must be set very large, the component selection is difficult, the error is huge, and the normal signal is seriously delayed. In addition, for the case where the duration of the interference signal is close to that of the effective signal, the analog scheme is almost unable to accurately filter the interference, and digital filtering can solve the above problems. SUMMARY

[0004] The purpose of the present application is to overcome the problems in the prior art and propose a digital filtering method for long-time interference signal.

[0005] In order to achieve the purpose, the technical scheme of the present application is as follows: a long-time interference signal digital filtering system, comprising a clock unit, a synchronization unit, a window sampling unit, a window width setting unit, a consistency judgment unit and an output unit, the synchronization unit, the window sampling unit, the consistency judgment unit and the output unit are sequentially connected, and the clock unit is connected with the synchronization unit, the window sampling unit, the consistency judgment unit and the output unit respectively.

[0006] The present application also provides a long-time interference signal digital filtering method, comprising the following steps:

[0007] The present application provides a long-time interference signal digital filtering system.

[0008] Under the clock period of the clock unit, the synchronization unit synchronizes the input signal to output the synchronized input signal; the window sampling unit performs window sampling on the synchronized input signal, and writes the sampling data into the memory according to the first-in first-out order; the consistency judgment unit performs consistency judgment on all the sampling data in the window sampling unit and outputs a judgment result signal; if the sampling data are all the same, the judgment result signal is high; if not, the judgment result signal is low; and the output unit outputs according to the judgment result signal of the consistency judgment unit; if the judgment result signal is high, the output of the output unit is equal to the output of the synchronization unit; if the judgment result signal is low, the output of the output unit remains unchanged.

[0009] The method for adjusting the filtering time width changes the clock frequency of the clock unit and the window width of the window sampling unit.

[0010] Compared with the prior art, the present application has the beneficial effects that: the long-time continuous interference signal can be filtered, the interference signal of a specific duration can be filtered without affecting the normal signal, the filtering accuracy is high, and the filtering time can be accurately adjusted.

[0011] The present application can be used for interference filtering during signal transmission between avionics, and can also be used for any other device requiring interference filtering.

[0012] In addition to the technical problems solved by the present application, the technical features constituting the technical scheme and the beneficial effects brought by these technical features described above, other technical problems solved by the present application, other technical features included in the technical scheme and the beneficial effects brought by these technical features will be further described in detail in combination with the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1Structure diagram of an embodiment of the present application.

[0014] Figure 2 Working principle diagram of an embodiment of the present application. DETAILED DESCRIPTION

[0015] The present application will be further described below in detail with specific embodiments and accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present application, but does not constitute a limitation on the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0016] Please refer to Figure 1 , which shows a digital filtering system of long-time interference signal. It contains clock unit 1, synchronization unit 2, window sampling unit 3, window width setting unit 4, consistency judgment unit 5 and output unit 6. The synchronization unit 2, the window sampling unit 3, the consistency judgment unit 5 and the output unit 6 are sequentially connected, and the clock unit 1 is connected with the synchronization unit 2, the window sampling unit 3, the consistency judgment unit 5 and the output unit 6 respectively.

[0017] Please refer to Figure 2 , the working principle of the digital filtering system of long-time interference signal is as follows: after the input signal passes through the synchronization unit 2, it is synchronized with the clock A output by the clock unit 1, and the synchronized signal B enters the window sampling unit 3 for sampling. The window sampling unit 3 writes the sampling data C into the memory according to the first-in first-out order. The storage depth is equal to the window width. The consistency judgment unit 5 judges the consistency of all the data stored by the window sampling unit 3 in the clock cycle. If all the data are the same (all 0 or all 1), the judgment result D outputs 1, otherwise the judgment result D outputs 0. The output unit 6 decides its output according to the judgment result D. If the judgment result D is 1, the output of the output unit 6 is equal to the synchronized signal B output by the synchronization unit 2, and if the judgment result D is 0, the output of the output unit 6 remains unchanged.

[0018] In this way, the long-time continuous interference signal can be filtered, the interference signal of a specific duration can be filtered without affecting the normal signal, the filtering accuracy is high, and the filtering time can be accurately adjusted.

[0019] The above merely expresses the embodiments of the present application, the description is more specific and detailed, but cannot be understood as the limitation of the patent scope of the application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A method of digital filtering of long-term interference signals, characterized in that, The method comprises the following steps, The digital filter system for long-time interference signal comprises a clock unit, a synchronization unit, a window sampling unit, a window width setting unit, a consistency judgment unit and an output unit. The synchronization unit, the window sampling unit, the consistency judgment unit and the output unit are sequentially connected, and the clock unit is connected with the synchronization unit, the window sampling unit, the consistency judgment unit and the output unit respectively. In the clock cycle of the clock unit, the synchronization unit synchronizes the input signal to output the synchronized input signal; the window sampling unit performs window sampling on the synchronized input signal, and writes the sampling data into the memory in the order of first-in first-out; the consistency judgment unit judges the consistency of all the sampling data in the window sampling unit and outputs a judgment result signal; if the sampling data are all the same, the judgment result signal is high; if not, the judgment result signal is low; and the output unit outputs according to the judgment result signal of the consistency judgment unit; if the judgment result signal is high, the output of the output unit is equal to the output of the synchronization unit; if the judgment result signal is low, the output of the output unit remains unchanged.

2. The system for digital filtering of long-duration jamming signals according to claim 1, characterized in that, The method for adjusting the filtering time width is achieved by changing the clock frequency of the clock unit and the window width of the window sampling unit.

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