CN102401896A - Method for calculating Doppler signal spectrum - Google Patents

Abstract

The invention discloses a method for calculating Doppler signal spectrum, which sequentially comprises the following steps that: two antennas with different launch angles are arranged in a speed measurement radar system so as to acquire the Doppler signal; the original signals are subjected to band-pass or low-pass filtering and then FFT (Fast Fourier Transform Algorithm) transform to acquire the corresponding spectrums; the two spectrums are synthetized, and points of discontinuity of the two spectrums are removed; the strength and signal to noise ratio of the signal are assessed, and the proximal frequency points are searched in the spectrum synthesis; and the spectral line of the crossed spectral line is gathered to obtain the frequency estimate as well as smooth and calculate the parameters. The method disclosed by the invention can effectively avoid the error of calculation of the single Doppler signal spectrum caused by roadbed function, so that the relative running speed of a railway locomotive with high accuracy can be acquired.

Description

A kind of method that is used to calculate Doppler signal frequency spectrum

Technical field

The present invention relates to a kind of method that is used to calculate Doppler signal frequency spectrum, especially relate to a kind of method that in railway locomotive velocity radar system, is used for the signal spectrum of computing machine vehicle speed.

Background technology

The frequency spectrum Doppler technology is widely used in auto industry as a kind of method of basis; And for rail vehicles; The rapid variation of considering track ground must cause the variation of Doppler frequency spectrum, and the center of Doppler frequency spectrum also can change simultaneously, and causes that the correction factor of speed is also changing; To this problem, we have introduced a kind of computing method of the railway locomotive travelling speed being carried out valuation according to the intersection frequency of double antenna frequency spectrum.

Summary of the invention

The purpose of this invention is to provide a kind of method that is used to calculate Doppler signal frequency spectrum; It can be according to the Doppler signal amplitude, centre frequency, the bandwidth that estimate; Utilize the singularity of Doppler frequency spectrum, calculate required parameter exactly, to overcome the various defectives that prior art exists.

The so-called a kind of method that is used to calculate Doppler signal frequency spectrum of the present invention is characterized in that it experiences following step successively:

In the velocity radar system, install emission angle be respectively 40 ° with 50 ° and two antennas that highly are 500mm are set, their distinguish radiation millimeter wave, with transmitted wave and reflection echo difference frequency, the signal that obtains is Doppler signal; Be with logical or LPF to original Doppler signal, should the filtering high frequency interference with noise in high fdrequency component, necessary anti-aliasing filter before also will accomplishing AD and sampling is to satisfy nyquist sampling theorem; Data to after the sampling are carried out the FFT conversion to obtain corresponding frequency spectrum; The frequency spectrum of two antennas is synthesized and removes catastrophe point; Intensity, signal to noise ratio (S/N ratio) to Doppler signal are assessed, immediate frequency during the search frequency spectrum is synthetic; The intersection frequency that searches is gathered the heart to obtain Frequency Estimation; Confirm filter range according to frequency change rate repeatedly, be with logical or LPF further to reduce parameter error; Calculate, two corresponding Doppler's expression formulas of antenna do

Add relational expression by two formulas arrangement gained

With $\frac{{\stackrel{\mathrm{\&iota;}}{F}}_d-{\mathrm{<figure-callout\; id="2"\; label="F\; d"\; filenames="HDA0000086643930000013.png"\; state="\{\{state\}\}">F</figure-callout>}}_d}{2}+F_d=F_k---4,$ Can obtain F from relational expression 3 and 4 _d(i.e. the Doppler frequency of 40 ° of antennas) also has

The i.e. Doppler frequency of 50 ° of antennas, substitution relational expression again 1 and 2 just can obtain corresponding railway locomotive travelling speed V, the f in the relational expression 1 ₀Be the transmission frequency of 40 ° of antennas, in the relational expression 2

Be the transmission frequency of 50 ° of antennas, the C in two formulas then is the light velocity 3 * 10 ⁸M/s.

The invention has the beneficial effects as follows: when measuring the railway locomotive travelling speed, can avoid the influence of different surface state effectively, significantly improve the accuracy of parameter estimation, thereby obtain high-precision measurement result spectrum analysis according to these computing method.

Description of drawings

Fig. 1 is radar microwave radiation areas figure;

Fig. 2 is the vertical view of Fig. 1;

Fig. 3 is the spectrogram under the two microwave antenna ideal situations of vehicle-mounted velocity radar.

Among the figure: the frequency spectrum that 1, obtains under the 2 one multidirectional same sex reflection cases, the frequency spectrum that obtains under 3, the 4 one multidirectional different in nature reflection cases, F _KThe intersection point of one frequency spectrum.

Embodiment

To measure the railway locomotive travelling speed is example, Vehicular radar system 500mm highly be provided with emission angle be respectively 40 ° with two antennas of 50 °, there is covering to a certain degree in the millimeter wave that two antennas are launched on reflecting surface.A kind of method that is used to calculate Doppler signal frequency spectrum provided by the invention experiences following step successively: with the transmitted wave of two antennas and reflection echo difference frequency to obtain Doppler signal; Be with logical or LPF to original Doppler signal, should the filtering high frequency interference and noise in high fdrequency component, also to accomplish necessary anti-aliasing filter before the sampling, to satisfy nyquist sampling theorem; Data to after the sampling are carried out the FFT conversion to obtain corresponding frequency spectrum; The frequency spectrum of two antennas is synthesized and removes catastrophe point; Intensity, signal to noise ratio (S/N ratio) to Doppler signal are assessed, immediate frequency during the search frequency spectrum is synthetic; The Frequency Estimation that obtains that the spectral line of the intersection frequency that searches is gathered the heart; Confirm filter range according to frequency change rate repeatedly, be with logical or LPF with further minimizing parameter error; Calculate, two corresponding Doppler's expression formulas of antenna are:

With

Add relational expression by two formulas arrangement gained

Also have $\frac{{\stackrel{\mathrm{\&iota;}}{F}}_d-{\mathrm{<figure-callout\; id="2"\; label="F\; d"\; filenames="HDA0000086643930000013.png"\; state="\{\{state\}\}">F</figure-callout>}}_d}{2}+F_d=F_k,$ Earlier try to achieve F from latter two relational expression _dWith

Here it is we to obtain in isotropy (ground function U _I=1) ideal and free from error Doppler frequency under the ideally-reflecting face, preceding two relational expressions of substitution just can obtain the corresponding relative travelling speed V of railway locomotive again.

Claims (1)

1. method that is used to calculate Doppler signal frequency spectrum is characterized in that it experiences following step successively:

1. in the velocity radar system, install emission angle be respectively 40 ° with 50 ° and two antennas that highly are 500mm are set, their distinguish radiation millimeter wave, with transmitted wave and reflection echo difference frequency, the signal that obtains is Doppler signal;

2. be with logical or LPF to original Doppler signal, should the filtering high frequency interference with noise in high fdrequency component, necessary anti-aliasing filter before also will accomplishing AD and sampling is to satisfy nyquist sampling theorem;

3. the data after the sampling are carried out the FFT conversion to obtain corresponding frequency spectrum;

4. the frequency spectrum of two antennas is synthesized and remove catastrophe point;

5. intensity, the signal to noise ratio (S/N ratio) of Doppler signal are assessed immediate frequency during the search frequency spectrum is synthetic;

6. the spectral line to the intersection frequency that searches gathers the heart to obtain Frequency Estimation;

7. confirm filter range based on frequency change rate repeatedly, be with logical or LPF further to reduce parameter error;

8. calculate, two corresponding Doppler's expression formulas of antenna do

Add relational expression by two formulas arrangement gained Also have $\frac{{\stackrel{\mathrm{\&iota;}}{F}}_d-F_d}{2}+F_d=F_k---4,$ Can obtain F from relational expression 3 and 4 _dPromptly the Doppler frequency of 40 ° of antennas also has

The i.e. Doppler frequency of 50 ° of antennas, substitution relational expression again 1 and 2 just can obtain corresponding rail locomotive travelling speed V, the f in the relational expression 1 ₀Be the transmission frequency of 40 ° of antennas, in the relational expression 2

Be the transmission frequency of 50 ° of antennas, the C in two formulas then is the light velocity 3 * 10 ⁸M/s.

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