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Wave filtering method

A filter and pulse echo technology, which is applied in the field of filters, can solve the problems of small calculation amount, achieve the effect of small calculation amount, improve signal-to-noise ratio, and realize convenience

Active Publication Date: 2009-10-28
OFT OPTOELECTRONICS TECH
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Problems solved by technology

[0005] The purpose of the present invention is to provide a filtering method based on digital signal processing for the problem of pulse echo signal being interfered by noise.

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Embodiment Construction

[0031] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0032] 1. Principle analysis

[0033] Suppose the transmitted pulsed ultrasonic signal is f(t), its spectrum is F(jω), the echo signal modulated by the measured parameter is x(t), its spectrum is X(jω), and the additive noise is n( t), its spectrum is N(jω), then the echo signal received by the instrument is y(t), and its corresponding spectrum is Y(jω). There is the following relationship between them

[0034] y(t)=x(t)+n(t) (1)

[0035] Y(jω)=X(jω)+N(jω) (2)

[0036] In the formula, ω is the angular frequency, the unit is rad / s, and the common frequency f, the unit is Hz, the relationship is ω=2πf. Here the frequency band of the signal x(t) is limited, while the noise n(t) is broadband. The two frequency bands can be overlapping or separate.

[0037] Assuming that the transmitted pulsed ultrasonic signal has a Gaussian...

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Abstract

The invention relates to a wave filtering method, which solves the problem of noise filtration when a pulse echo signal is intervened by noise from the view of signal processing. The method comprises the following steps: acquiring a transmitted pulse signal, and obtaining a frequency spectrum of the transmitted pulse signal through Fourier transformation; performing waveform analysis on the frequency spectrum of the transmitted pulse signal, and determining a geometrical structure of the waveform of the frequency spectrum; determining effective bandwidth of the frequency spectrum of the transmitted pulse signal; determining central frequency of the frequency spectrum of the transmitted pulse signal; designing a wave filter; acquiring an actually-measured pulse echo signal, and obtaining a frequency spectrum of the actually-measured pulse echo signal by Fourier transformation; multiplying the frequency spectrum of the actually-measured pulse echo signal by a frequency response function of the wave filter in a frequency domain to obtain a frequency spectrum of a detection echo signal after wave filtration; and performing Fourier transformation on the frequency spectrum of the echo signal in the step, and multiplying the transformed frequency spectrum of the echo signal by a shifted factor to obtain a filtered detection echo signal. The method is particularly applicable to detecting a weak pulse echo signal.

Description

Technical field: [0001] The invention relates to a filter method, which is suitable for removing noise in an echo signal when a pulse wave signal is used for detection. Background technique: [0002] The pulse echo signal can be used for parameter detection and material property detection. This type of detection is mostly used in military, industrial, agricultural, medical and other fields. The filtering problem of the echo signal is a traditional and typical research topic. According to the data (RajaKumar.R.V., Palr.N., Tracking of bandpass signals using center-frequency adaptive filters, IEEE transactions on acoustics, speech, and signal processing, 1990, vol.38, no10, pp.1710-1721) such There are many methods of filtering the echo signal. At present, the representative ones are the low-pass, high-pass, band-pass and band-stop technologies based on classical filtering techniques. These technologies are relatively mature and easy to apply. Their biggest feature is that th...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03H17/02
Inventor 宋寿鹏李骁斐任博路欣徐琳潘海彬
Owner OFT OPTOELECTRONICS TECH
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