CN102707275A - Digital processing method of altimeter of linear frequency modulation continuous wave radar - Google Patents

Abstract

The invention discloses a digital processing method of an altimeter of a linear frequency modulation continuous wave radar, which belongs to the field of the radio altimeters. The digital processing method comprises the following steps: step 1, obtaining beating signals from an orthogonal mixer arranged at the front end of the altimeter of the radar, and carrying out A/D (analog-to-digital) sampling to obtain a digital signal sequence; step 2, performing Fourier transform on the digital signal sequence, and calculating the amplitude of a spectral line; step 3, judging according to the amplitude of the spectral line of an amplitude spectrum, and measuring the beating frequency of the digital signal sequence; step 4, refining the frequency spectrum, calculating the slope correction of saw-tooth wave, and correcting the slope of the voltage signals of the saw-tooth wave; and step 5, calculating the high value of the current altimeter according to the slope of the voltage signals of the saw-tooth wave. The FFT-CZT method adopted by the invention is insensitive to noises and can perfectly work at lower signal-to-noise ratio, but the measurement precision is reduced. Because of having no limit on the properties of the targets, the digital processing method can be applied to the measurement and the analysis of point targets or surface targets.

Description

A kind of digitalized processing method of linear frequency modulation continuous wave radar altimeter

Technical field

The present invention relates to a kind of digitalized processing method of linear frequency modulation continuous wave radar altimeter, belong to the radio altimeter field.

Background technology

The linear frequency modulation continuous wave radar altimeter; It is the LFMCW radar altimeter; It is a kind of height finder operator's section that obtains height value through echoed signal and the Beat Signal that transmits; Radiation power is little, measuring accuracy is high, equipment is simple relatively, good electron is resisted advantages such as performance and low probability of intercept owing to have, and has been widely used in various aircraft such as unmanned plane at present.LFMCW radar altimeter early adopts the mode of average frequency counting to obtain the elevation information in the Beat Signal; Afterwards; Arrived the eighties mid-term, because the especially application of microprocessor in height indicator of digital technology makes CW with frequency modulation system radar altimeter obtain remarkable progress.Be different from previous time domain processing mode; Begin to adopt Digital Signal Processing to realize extraction for the Beat Signal that obtains to elevation information; Wherein the most frequently used algorithm is FFT, but because FFT is the spectrum analysis of on the whole unit circle in Z territory, carrying out, so its frequency resolution is f _s/ N, wherein f _sBe SF, N is the effective length of signal x (n), wants to improve frequency resolution and then realizes that high altimetry precision need increase the intercepted length to signal x (n), but calculated amount is increased greatly.Simultaneously; When adopting traditional FFT that signal is carried out spectrum analysis; Can receive the influence of aliasing effect, quantization error, leakage effect and fence effect, " fence effect " of FFT especially, the distance spectrum that directly adopts FFT and obtained has fixed distance Δ R (range resolution of radar); Thereby produce the range error of Δ R/2, this relative error that makes radar altimeter under low clearance, measure is bigger.

Summary of the invention

To the problem that exists in the prior art, the present invention proposes a kind of digitalized processing method of linear frequency modulation continuous wave radar altimeter, in permanent beat system LFMCW radar altimeter system, uses the FFT-CZT method and improves measuring accuracy.The FFT-CZT method is a kind of method that both combine with FFT and Chirp-Z; Basic ideas are to utilize FFT that the beat frequency spectrum of echoed signal is carried out bigness scale earlier; The frequency band that uses the Chirp-Z transfer pair to set then carries out local refinement; Reduce the SI on the beat frequency spectrum, reach the purpose that improves measuring accuracy.The calculated amount of the method is compared with the FFT method of direct increase sampling number and is wanted much less.Replace traditional frequency discriminator that Beat Signal is handled with the FFT-CZT method; Calculate the output height value after the tracking attitude of proofreading and correct through bigness scale search and to the cycle of modulation sawtooth wave, simulation result shows that this kind signal processing method can realize high-acruracy survey.

The present invention proposes a kind of digitalized processing method of linear frequency modulation continuous wave radar altimeter, mainly comprises following step:

Step 1: obtain Beat Signal from the front end orthogonal mixer of radar altimeter, the difference frequency ratings is f _P, Beat Signal is carried out the A/D sampling, obtain digital signal sequences x (n);

Step 2: digital signal sequences is carried out Fast Fourier Transform (FFT) and calculates the amplitude of each bar spectral line;

Obtain the Fourier transform of digital signal sequences according to the discrete Fourier transformation formula, the transformation relation formula is following:

$\left\{\begin{array}{c}X\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)W_N^{\mathrm{kn}},k=\mathrm{0,1,2},...,N-1\\ x\left(n\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}X\left(k\right)W_N^{-\mathrm{kn}},n=\mathrm{0,1,2},...,N-1\end{array}\right.---\left(1\right)$

Wherein: x (n) is a digital signal sequences, and this sequence length is N, and X (k) is the plural expression-form of the Fourier transform of digital signal sequences x (n), W _NBe the Fourier transform factor,

N and k represent the position of the middle each point of Fourier transform sequence X (k) of digital signal sequences x (n) and x (n) sequence respectively; The Fourier transform sequence X (k) that obtains digital signal sequences x (n) afterwards; Through Fourier transform sequence X (k) delivery is obtained amplitude spectrum; And the amplitude of each bar spectral line in the calculating amplitude spectrum, the amplitude threshold value is set simultaneously;

Step 3: adjudicate and measure the difference frequency of digital signal sequences x (n) according to amplitude spectrum spectral line amplitude, if difference frequency is at [f _P-Δ f _P, f _P+ Δ f _P] in the scope, write down spectral line positions in Fourier transform sequence X (k) that all surpass the amplitude threshold value, get into step 4; Otherwise the slope of the sawtooth voltage signal that the adjustment saw-toothed wave generator produces is specially: in amplitude spectrum, surpass the corresponding frequency of the spectral line of amplitude threshold value less than f _P-Δ f _P, then increase the slope of sawtooth wave, in amplitude spectrum, surpass the corresponding frequency of the spectral line of amplitude threshold value greater than f _P+ Δ f _P, then reduce the slope of sawtooth wave, return step 1 and search for again, until the spectral line difference frequency that in amplitude spectrum, surpasses the amplitude threshold value can search at least one spectral line in this specified hunting zone till;

Step 4: through Chirp-Z transfer pair frequency band [f _P-Δ f _P, f _P+ Δ f _P] carry out the frequency spectrum refinement, calculate sawtooth wave slope correction, the slope of the sawtooth voltage signal that current saw-toothed wave generator is produced is revised, and makes difference frequency stable to difference frequency ratings f _P

Difference frequency is at specified hunting zone [f _P-Δ f _P, f _P+ Δ f _P] in, do the frequency spectrum refinement through this frequency band of Chirp-Z transfer pair and analyze, obtain the exact value of difference frequency; Chirp-Z transformation relation formula is:

$X\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right){z_k}^{-n}---\left(2\right)$

z _k＝AW ^-k,0≤k≤M-1（3）

Wherein: x (n) is a digital signal sequences, and sequence length is N, and X (k) is the plural expression-form of the transform of digital signal sequences x (n), and M is that the frequency sampling in the frequency band of being analyzed is counted, and A is the starting point of Chirp-Z conversion, and W is the ratio between X (k) each point, z _kBe the sampled point of Chirp-Z conversion, k representes the position of X (k) sequence each point, and n representes the position of each point among the digital signal sequences x (n), and A and W are expressed as with polar form:

A wherein ₀Vector radius for the sampling starting point; W ₀Be the inside still bandy parameter of control sampling wheel profile; The transform path of Chirp-Z conversion is one section circular arc on the unit circle, θ ₀Phase angle for starting point;

Be the angular frequency rate variance of adjacent spots, following relation arranged with difference frequency:

F wherein ₁Be the initial frequency of refinement analysis frequency band, f ₂For stopping frequency, f ₁=f _P-Δ f _P, f ₂=f _P+ Δ f _P, by (5) formula, in this refinement frequency band, frequency resolution does

Obtain finding the maximum spectral line of amplitude in its amplitude spectrum behind the X (k), the k value that spectral line is corresponding, the exact value that obtains difference frequency is Δ f,

Ratings f with Δ f and difference frequency _PCompare, if the exact value Δ f of difference frequency equals f _P, or the exact value Δ f of difference frequency and ratings f _PThe absolute value of difference less than frequency resolution, the slope of record sawtooth voltage signal this moment; If the exact value Δ f of difference frequency is not equal to f _P, the exact value Δ f and the ratings f of while difference frequency _PThe absolute value of difference more than or equal to frequency resolution, the correction that then calculates the sawtooth voltage signal slope does The slope of the sawtooth voltage signal that the adjustment saw-toothed wave generator produces carries out step 4 again and proofreaies and correct, until meeting the demands record sawtooth voltage signal slope γ ₀

Step 5: the height value that calculates current height indicator according to the sawtooth voltage signal slope:

The sawtooth voltage signal γ that utilizes step 4 to obtain ₀, go out the height value h of height indicator through computes ₀:

$h_0=\frac{f_p}{{\mathrm{\γ}}_0}\·\frac{c}{2}---\left(6\right)$

Wherein, c is a radio wave propagation speed.

The invention has the advantages that:

(1) the present invention proposes a kind of digitalized processing method of linear frequency modulation continuous wave radar altimeter, and the FFT-CZT method of employing is the basis with FFT, and Fast Fourier Transform (FFT) is quite ripe, and a large amount of general, special-purpose software and hardware supports is arranged;

(2) the present invention proposes a kind of digitalized processing method of linear frequency modulation continuous wave radar altimeter, and the FFT-CZT method that the present invention adopts still can be worked under lower signal to noise ratio (S/N ratio) to insensitive for noise preferably, and just measuring accuracy can descend to some extent;

(3) the present invention proposes a kind of digitalized processing method of linear frequency modulation continuous wave radar altimeter, and to the not restriction of characteristic of target, therefore both can be used for point target also can be used for appearance target Measurement and analysis.

Description of drawings

Fig. 1: the process flow diagram of the digitalized processing method of a kind of linear frequency modulation continuous wave radar altimeter that the present invention proposes;

Fig. 2: the signal flow diagram of the digitalized processing method of a kind of linear frequency modulation continuous wave radar altimeter that the present invention proposes.

Among the figure: the 1-saw-toothed wave generator; The 2-radio frequency source; 3-power amplifier A; The 4-circulator;

The 5-antenna; The 6-receiving front-end offsets processing module; 7-power amplifier B;

The 8-orthogonal mixer; The 9-low-frequency amplifier; The 10-correcting circuit.

Embodiment

To combine accompanying drawing that the present invention is done further detailed description below.

The present invention proposes a kind of digitalized processing method of linear frequency modulation continuous wave radar altimeter, and is as shown in Figure 1, comprises following step:

Step 1: obtain Beat Signal from the front end orthogonal mixer of radar altimeter, and Beat Signal is carried out obtaining digital signal sequences x (n) after A/D sampling, the quantification;

Obtain Beat Signal x (t) from the front end orthogonal mixer of radar altimeter, the difference frequency ratings of this Beat Signal is f _p, for continuous permanent Beat Signal, carry random noise signal, this Beat Signal is carried out the A/D sampling, SF is f _s, after over-sampling, obtain digital signal sequences x (n).

The procurement process of described Beat Signal: as shown in Figure 2; The sawtooth voltage signal controlling radio frequency source 2 that is produced by saw-toothed wave generator 1 produces the linear frequency modulation continuous wave signal; This linear frequency modulation continuous wave signal a part of signal after power amplifier A3 power amplification is fed to antenna 5 through circulator 4; By antenna 5 signal radiation is gone out; The signal that receives by antenna 5 again; Signal inputs to receiving front-end through circulator 4 and offsets processing module 6, offsets processing with another part signal from power amplifier A3, after offseting processing, carries out power amplification through power amplifier B7 again; Signal after amplifying gets into orthogonal mixer 8 and carries out Frequency mixing processing; The signal of this Frequency mixing processing is that signal and the radio frequency source 2 after power amplifier B7 power amplification produces the linear frequency modulation continuous wave signal, exports Beat Signal after orthogonal mixer 8 Frequency mixing processing, and this Beat Signal is amplified into the digital signal processing link through low-frequency amplifier 9 and handles; Be specially in order through the Fourier transform of step 2, the search of step 3 Beat Signal frequency, the processes such as tracking processing of step 4, produce the slope that correction signals are controlled the sawtooth voltage signal that saw-toothed wave generator produces through control correcting circuit 10 at last.

Step 2: digital signal sequences is carried out Fast Fourier Transform (FFT) and calculates the amplitude of each bar spectral line;

Obtain the Fourier transform of digital signal sequences according to the discrete Fourier transformation formula, the transformation relation formula is following

$\left\{\begin{array}{c}X\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)W_N^{\mathrm{kn}},k=\mathrm{0,1,2},...,N-1\\ x\left(n\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}X\left(k\right)W_N^{-\mathrm{kn}},n=\mathrm{0,1,2},...,N-1\end{array}\right.---\left(1\right)$

Wherein: x (n) is a digital signal sequences, and this sequence length is N, and X (k) is the plural expression-form of the Fourier transform of digital signal sequences x (n), W _NBe the Fourier transform factor,

N and k represent the position of each point among digital signal sequences x (n) and its Fourier transform X (k) respectively.The Fourier transform sequence X (k) that obtains digital signal sequences x (n) through Fourier transform sequence X (k) delivery is obtained amplitude spectrum, and is calculated the amplitude of each bar spectral line in the amplitude spectrum afterwards, and the amplitude threshold value is set simultaneously.

Step 3: adjudicate and measure the difference frequency of digital signal sequences x (n) according to amplitude spectrum spectral line amplitude, if difference frequency is at difference frequency ratings f _PNear, promptly at [f _P-Δ f _P, f _P+ Δ f _P] in the scope, then get into step 4, get into tracking mode; Otherwise the slope of the sawtooth voltage signal that the adjustment saw-toothed wave generator produces returns step 1; Difference frequency ratings f _PDesign parameter by system provides, generally much smaller than SF f _s, Δ f _PFor the difference frequency float value, be generally 20%f _P

Make comparisons the amplitude threshold value of the amplitude of every spectral line in the amplitude spectrum and setting, write down the position of spectral line in Fourier transform sequence X (k) that all surpass the amplitude threshold value, these spectral lines that surpass the amplitude threshold value are concentrated in the i.e. [f of one section narrower frequency band _P-Δ f _P, f _P+ Δ f _P] in the scope, if be in the spectral line in this scope, the slope of the sawtooth voltage signal that the adjustment saw-toothed wave generator produces returns step 1, searches for next time.According to the character of Fast Fourier Transform (FFT), N bar spectral line is to be evenly distributed in 0 on the frequency axis, f _sBetween, f _sBe the SF of A/D sampling in the step 1, therefore the position by each bar spectral line place just can obtain the corresponding difference frequency of each bar spectral line.If be not in [f _P-Δ f _P, f _P+ Δ f _P] spectral line of scope, two kinds of situation are then arranged, in amplitude spectrum, surpass the corresponding frequency of the spectral line of amplitude threshold value less than f _P-Δ f _P, then increase the slope of sawtooth wave; In amplitude spectrum, surpass the corresponding frequency of the spectral line of amplitude threshold value greater than f _P+ Δ f _P, then reduce the slope of sawtooth wave; Return step 1 and search for again, until the spectral line difference frequency that in amplitude spectrum, surpasses the amplitude threshold value at this specified hunting zone [f _P-Δ f _P, f _P+ Δ f _P] interior can institute searching till at least one spectral line.

Step 4: be in [f through the Chirp-Z transfer pair _P-Δ f _P, f _P+ Δ f _P] spectral line frequency band in the scope carries out the frequency spectrum refinement, calculates sawtooth wave slope correction, the sawtooth voltage signal that current saw-toothed wave generator is produced is revised and is made difference frequency stable to difference frequency ratings f _P

Search procedure finishes the back and gets into tracing process.This moment, difference frequency was at specified hunting zone [f _P-Δ f _P, f _P+ Δ f _P] in, do the frequency spectrum refinement through this frequency band of Chirp-Z transfer pair and analyze, obtain the exact value of difference frequency.Chirp-Z transformation relation formula is following:

$X\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right){z_k}^{-n}---\left(2\right)$

z _k＝AW ^-k,0≤k≤M-1（3）

Wherein: x (n) is a digital signal sequences, and sequence length is N, and X (k) is the plural expression-form of the transform of digital signal sequences x (n).M is that the frequency sampling in the frequency band of being analyzed is counted.A and W are plural arbitrarily, and A is the starting point of Chirp-Z conversion, and W is the ratio between X (k) each point.z _kBe the sampled point of Chirp-Z conversion, k representes the position of each point in X (k) sequence, and n representes the position of each point among the digital signal sequences x (n).A and W are expressed as with polar form

Wherein: A ₀Vector radius for the sampling starting point; W ₀Be the inside still bandy parameter of control sampling wheel profile; Get A among the present invention ₀=W ₀=1, this moment, the transform path of Chirp-Z conversion was one section circular arc on the unit circle.θ ₀Phase angle for starting point;

Be the angular frequency rate variance of adjacent spots, following relation arranged with difference frequency,

In the formula, f ₁Be the initial frequency of refinement analysis frequency band, f ₂For stopping frequency, in the present invention, f ₁=f _P-Δ f _P, f ₂=f _P+ Δ f _PCan know by (5) formula; In this refinement frequency band, frequency resolution is

Obtain finding the maximum spectral line of amplitude in its amplitude spectrum behind the X (k), the k value that spectral line is corresponding, the exact value that obtains difference frequency is Δ f,

Ratings f with Δ f and difference frequency _PCompare, if the exact value Δ f of difference frequency equals f _P, or the exact value Δ f of difference frequency and ratings f _PThe absolute value of difference less than frequency resolution, the slope of record sawtooth voltage signal this moment; If the exact value Δ f of difference frequency is not equal to f _P, the exact value Δ f and the ratings f of while difference frequency _PThe absolute value of difference more than or equal to frequency resolution, the correction that then calculates the sawtooth voltage signal slope does

The slope of the sawtooth voltage signal that the adjustment saw-toothed wave generator produces carries out step 4 again and proofreaies and correct, until meeting the demands record sawtooth voltage signal slope γ ₀

Step 5: the height value that calculates current height indicator according to the sawtooth voltage signal slope.

The sawtooth voltage signal γ that utilizes step 4 to obtain ₀, can calculate the height value h of height indicator through following formula ₀

$h_0=\frac{f_p}{{\mathrm{\γ}}_0}\·\frac{c}{2}---\left(6\right)$

Wherein, c is a radio wave propagation speed.

Claims (3)

1. the digitalized processing method of a linear frequency modulation continuous wave radar altimeter is characterized in that: comprise following step:

Step 1: obtain Beat Signal from the front end orthogonal mixer of radar altimeter, the difference frequency ratings is f _P, Beat Signal is carried out the A/D sampling, obtain digital signal sequences x (n);

Step 2: digital signal sequences is carried out Fast Fourier Transform (FFT) and calculates the amplitude of each bar spectral line;

Obtain the Fourier transform of digital signal sequences according to the discrete Fourier transformation formula, the transformation relation formula is following

$\left\{\begin{array}{c}X\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)W_N^{\mathrm{kn}},k=\mathrm{0,1,2},...,N-1\\ x\left(n\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}X\left(k\right)W_N^{-\mathrm{kn}},n=\mathrm{0,1,2},...,N-1\end{array}\right.---\left(1\right)$

Wherein: x (n) is a digital signal sequences, and this sequence length is N, and X (k) is the plural expression-form of the Fourier transform of digital signal sequences x (n), W _NBe the Fourier transform factor,

N and k represent the position of the middle each point of Fourier transform sequence X (k) of digital signal sequences x (n) and x (n) sequence respectively; The Fourier transform sequence X (k) that obtains digital signal sequences x (n) afterwards; Through Fourier transform sequence X (k) delivery is obtained amplitude spectrum; And the amplitude of each bar spectral line in the calculating amplitude spectrum, the amplitude threshold value is set simultaneously;

Step 3: adjudicate and measure the difference frequency of digital signal sequences x (n) according to amplitude spectrum spectral line amplitude, if difference frequency is at [f _P-Δ f _P, f _P+ Δ f _P] in the scope, write down spectral line positions in Fourier transform sequence X (k) that all surpass the amplitude threshold value, get into step 4; Otherwise the slope of the sawtooth voltage signal that the adjustment saw-toothed wave generator produces is specially: in amplitude spectrum, surpass the corresponding frequency of the spectral line of amplitude threshold value less than f _P-Δ f _P, then increase the slope of sawtooth wave, in amplitude spectrum, surpass the corresponding frequency of the spectral line of amplitude threshold value greater than f _P+ Δ f _P, then reduce the slope of sawtooth wave, return step 1 and search for again, until the spectral line difference frequency that in amplitude spectrum, surpasses the amplitude threshold value can search at least one spectral line in this specified hunting zone till;

Step 4: be in [f through the Chirp-Z transfer pair _P-Δ f _P, f _P+ Δ f _P] spectral line frequency band in the scope carries out the frequency spectrum refinement, calculates sawtooth wave slope correction, the slope of the sawtooth voltage signal that current saw-toothed wave generator is produced is revised, and makes difference frequency stable to difference frequency ratings f _P

Difference frequency is at specified hunting zone [f _P-Δ f _P, f _P+ Δ f _P] in, do the frequency spectrum refinement through this frequency band of Chirp-Z transfer pair and analyze, obtain the exact value of difference frequency; Chirp-Z transformation relation formula is:

$X\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right){z_k}^{-n}---\left(2\right)$

z _k＝AW ^-k,0≤k≤M-1（3）

Wherein: x (n) is a digital signal sequences, and sequence length is N, and X (k) is the plural expression-form of the transform of digital signal sequences x (n), and M is that the frequency sampling in the frequency band of being analyzed is counted, and A is the starting point of Chirp-Z conversion, and W is the ratio between X (k) each point, z _kBe the sampled point of Chirp-Z conversion, k representes the position of X (k) sequence each point, and n representes the position of each point among the digital signal sequences x (n), and A and W are expressed as with polar form:

A wherein ₀Vector radius for the sampling starting point; W ₀Be the inside still bandy parameter of control sampling wheel profile; The transform path of Chirp-Z conversion is one section circular arc on the unit circle, θ ₀Phase angle for starting point;

Be the angular frequency rate variance of adjacent spots, following relation arranged with difference frequency:

F wherein ₁Be the initial frequency of refinement analysis frequency band, f ₂For stopping frequency, f ₁=f _P-Δ f _P, f ₂=f _P+ Δ f _P, by (5) formula, in this refinement frequency band, frequency resolution does

Obtain finding the maximum spectral line of amplitude in its amplitude spectrum behind the X (k), the k value that spectral line is corresponding, the exact value that obtains difference frequency is Δ f, Ratings f with Δ f and difference frequency _PCompare, if the exact value Δ f of difference frequency equals f _P, or the exact value Δ f of difference frequency and ratings f _PThe absolute value of difference less than frequency resolution, the slope of record sawtooth voltage signal this moment; If the exact value Δ f of difference frequency is not equal to f _P, the exact value Δ f and the ratings f of while difference frequency _PThe absolute value of difference more than or equal to frequency resolution, the correction that then calculates the sawtooth voltage signal slope does

The slope of the sawtooth voltage signal that the adjustment saw-toothed wave generator produces carries out step 4 again and proofreaies and correct, until meeting the demands record sawtooth voltage signal slope γ ₀

Step 5: the height value that calculates current height indicator according to the sawtooth voltage signal slope:

The sawtooth voltage signal γ that utilizes step 4 to obtain ₀, go out the height value h of height indicator through computes ₀:

$h_0=\frac{f_p}{{\mathrm{\γ}}_0}\·\frac{c}{2}---\left(6\right)$

Wherein, c is a radio wave propagation speed.

2. the digitalized processing method of a kind of linear frequency modulation continuous wave radar altimeter according to claim 1; It is characterized in that: the concrete procurement process of the Beat Signal in the step 1 is: the sawtooth voltage signal controlling radio frequency source that is produced by saw-toothed wave generator produces the linear frequency modulation continuous wave signal; This linear frequency modulation continuous wave signal a part of signal after power amplifier A power amplification is fed to antenna through circulator; By antenna signal radiation is gone out; By antenna receiving signal, signal inputs to receiving front-end through circulator and offsets processing module again, offsets processing with another part signal from power amplifier A; Handle after power amplifier B carries out power amplification through offseting; Signal after amplifying gets into orthogonal mixer and carries out Frequency mixing processing, and the signal of this Frequency mixing processing is that signal and the radio frequency source after power amplifier B power amplification produces the linear frequency modulation continuous wave signal, exports Beat Signal after the orthogonal mixer Frequency mixing processing.

3. the digitalized processing method of a kind of linear frequency modulation continuous wave radar altimeter according to claim 1 is characterized in that: described difference frequency float value Δ f _pBe 20%f _p

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