CN102628941A - Reconstruction method of broadband ultrasonic echo signal - Google Patents

Reconstruction method of broadband ultrasonic echo signal Download PDF

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CN102628941A
CN102628941A CN2012100630859A CN201210063085A CN102628941A CN 102628941 A CN102628941 A CN 102628941A CN 2012100630859 A CN2012100630859 A CN 2012100630859A CN 201210063085 A CN201210063085 A CN 201210063085A CN 102628941 A CN102628941 A CN 102628941A
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signal
subsignal
projection
rule
frequency
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陈明霞
王茂森
王猛
陆建
董永明
杨洋
黄顺斌
曹长龙
陈伟
伍立春
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Nanjing University of Science and Technology
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Abstract

The present invention relates to a reconstruction method of a broadband ultrasonic echo signal, projection conversion of a high frequency ultrasonic echo signal to other bands linearly and nonlinearly can be realized, and a technological approach for the application of the broadband ultrasonic echo signal in aspects of sonar guide, object detection and the like is provided. Implementing steps of the related reconstruction method comprise the following steps of: firstly, using a multi-channel filter set to decompose the broadband ultrasonic echo signal into subsignals with different center frequency and finite bandwidths; secondly, determining projection rules of each subsignal amplitude, duration, and center frequency; thirdly, detecting an amplitude change rule and duration of each original subsignal, by using a standard trigonometric function, and constructing a new subsignal according to the projection rules; and finally, synthesizing all reconstructed subsignals to obtain a final echo signal.

Description

A kind of reconstructing method of broadband ultrasonic echo signal
Technical field
The invention belongs to digital signal processing and application, for broadband ultrasonic echo signal provides technological approaches to other frequency bands (like audio frequency) projection conversion.
Background technology
The broadband ultrasonic signal is common in biology " echolocation " detection system.Often use broadband ultrasound wave (FM ripple) that the place ahead environment is surveyed like bat.Many researchs show, contain the characteristic of abundant objects in front in the broadband ultrasonic echo.The echoed signal mistiming back and forth can be confirmed the distance of object, and Doppler shift can transmit the velocity information of object flight, the amplitude of echo and the size that postpones to have indicated object, and the magnitude characteristic of echoed signal has disclosed object dimensional characteristic or the like.The application of broadband ultrasonic signal in apparatus for guiding blind is the new direction of its application.It can instruct the blind person to learn the principle of biology " echolocation ", information such as the distance of abundant echoed signal characteristic help blind people know objects in front, orientation, translational speed, shape.
The frequency of broadband ultrasonic signal higher (generally at 20KHZ-100KHZ), people's ear can't directly be heard, so need carry out frequency transformation to it.Be that the echoed signal of 20KHZ-100KHZ is converted into the 0.2KHZ-10KHZ scope for example, change the audiorange that to hear for people's ear frequency range.Simultaneously, the reproduction time of general broadband ultrasonic echo signal is shorter, and people's ear is difficult to catch changing features wherein, has influenced the distinguish over judgement of user to different objects.Therefore, when broadband ultrasonic echo signal was handled, the frequency of echoed signal and duration all need be done conversion.And can keep original echoed signal characteristic (like magnitude, phase change, stack characteristic etc.) rule approximate constant also be the key that the broadband ultrasonic signal is used for guide.Current, the biosonar research field does not just see as yet that ability realizes that at frequency domain and time domain the conversion of broadband ultrasonic wave echoed signal is direct available signal reconfiguring method and the technological realization approach of people's ear simultaneously in the world.
Summary of the invention
The technical matters that the present invention solved is to provide a kind of and preserves the signal primitive character and adapt to broadband ultrasonic echo signal that user's switching signal category the requires technological approaches to other frequency range projections conversions.
The technical solution that realizes the object of the invention is: a kind of reconstructing method of broadband ultrasonic echo signal may further comprise the steps:
Step 1, utilize hyperchannel BPF. group that broadband ultrasonic echo signal is decomposed into different center frequency and band-limited original sub signal according to reconstruct resolution condition;
Step 2, confirm the projection rule of ultrasonic signal to projection signal;
Step 3, detect magnitude rule, the duration of each original sub signal, utilize projection equation afterwards, according to the new subsignal of projection rule structure of step 2;
Step 4, all subsignals that step 3 is constructed synthesize processing, obtain the echoed signal of reconstruct.
The present invention compared with prior art, its remarkable advantage is: 1) echoed signal after the reconstruct keeps most of primitive character (amplitude, phase place, stack characteristic) information; 2) frequency bandwidth of the echoed signal after the reconstruct and duration can be widened or prolong according to demand, have improved the discrimination of echo character, can be adapted to the perception of people's ear better.
Below in conjunction with accompanying drawing the present invention is described in further detail.
Description of drawings
Fig. 1 is the reconstructing method process flow diagram of broadband ultrasonic echo signal of the present invention.
The broadband ultrasonic pulse example of Fig. 2 for launching among the present invention.
Fig. 3 is the preceding broadband ultrasonic echo example of the reconstruct among the present invention.
Fig. 4 is the former ultrasonic echo i sub-signals example behind BPF. among the present invention.
Fig. 5 is the broadband ultrasonic echo signal example after the reconstruct among the present invention.
Embodiment
The present invention can keep broadband ultrasonic echo signal to convert other frequency bands under most of primitive character (amplitude, phase place, stack characteristic) situation; And the duration of change echoed signal; To improve the active zone calibration of echo character, for broadband ultrasonic echo signal application provides technological approaches in aspects such as object identification, guides.
In conjunction with Fig. 1, the reconstructing method of a kind of broadband ultrasonic echo signal of the present invention may further comprise the steps:
Step 1, utilize hyperchannel BPF. group that broadband ultrasonic echo signal is decomposed into different center frequency and band-limited original sub signal according to reconstruct resolution condition;
Step 2, confirm the projection rule of ultrasonic signal, be specially to projection signal:
(1) the magnitude rule according to the new subsignal of projection rule structure is consistent with the magnitude rule of original sub signal, and the waveform distortion rule that also can cause by hardware such as sonic propagation attenuation law, ultrasonic sensors is on this basis done compensation to amplitude;
(2) duration of new subsignal is to multiply by the time change coefficient signal duration through original sub to obtain; Said each sub-signals time corresponding conversion coefficient is identical in a same restructuring procedure;
(3) the centre frequency F of new subsignal iBe through original sub signal center frequency f iMultiply by frequency transform coefficients in video codec ξ iObtain said frequency transform coefficients in video codec ξ iBy self-defined frequency transform function F i=g (f i) provide: ξ i=F i/ f iSaid self-defined frequency transform function can be set at linear function, i.e. F according to user's demand i=ξ iF i, promptly the frequency transform coefficients in video codec of each sub-signals correspondence is identical in a same restructuring procedure; Self-defined frequency transform function also can require to be nonlinear function to the projection of different frequency range subsignal according to the user, and promptly the corresponding frequency transform coefficients in video codec of each sub-signals is with different in restructuring procedure.
Step 3, detect magnitude rule, the duration of each original sub signal, utilize projection equation afterwards, according to the new subsignal of projection rule structure of step 2; Described each original sub signal projection equation is:
Figure BDA0000142511600000031
In the formula, E i(t) be the subsignal that the conversion of i original sub signal projection obtains;
A i(t) be the amplitude rule over time of subsignal;
f *(x) be the standard trigonometric function: sine function (sin function) or cosine function (cos function);
f i' for obtain the centre frequency of new subsignal according to the projection rule of afore mentioned rules;
Figure BDA0000142511600000032
is the initial phase of standard trigonometric function;
T i' for obtain the duration of new subsignal according to the projection rule of claim 2 defined;
T is a time variable.
Step 4, all subsignals that step 3 is constructed synthesize processing, obtain the echoed signal of reconstruct.
Particularly, broadband ultrasonic echo signals sampling frequency is F s, be decomposed into a plurality of different center frequency f through hyperchannel BPF. group (like the gammatone bank of filters etc.) iWith band-limited subsignal S i(t).In decomposable process, reconstruct resolution conditional decision the bandwidth and the quantity of the subsignal after decomposing, can regulate by user's request and set.The reconstruct resolution is high more, shows that the subsignal quantity that obtains after the decomposition is many more, and the bandwidth of each subsignal is also just narrow more; Anyway, the reconstruct resolution reduces, and the subsignal quantity that obtains after the decomposition also reduces, the also corresponding increase of the bandwidth of each subsignal.At this, can set and be broken down into the N sub-signals after original echoed signals passes through the hyperchannel BPF..
The magnitude rule of original sub signal is to obtain through each crest in the detection original sub signal or the corresponding peak value of trough, and each peak value is pressed the original time order and formed a sequence A i(t)={ A I1, A I2..., A Ij..., A IN, A wherein i(t) i centre frequency of expression is f iThe magnitude sequence of original sub signal, A IjBe illustrated in i the original sub signal the corresponding peak value of j crest or trough.Magnitude rule according to the new subsignal of projection rule structure can be consistent with the magnitude rule of original sub signal, promptly the amplitude of the subsignal after the projective transformation over time rule be A i(t); Also can be at A i(t) the waveform distortion rule that causes by hardware such as sonic propagation attenuation law, ultrasonic sensors on the basis is to A i(t) do compensation deals.
According to projection rule, the duration of new subsignal is to multiply by the time change coefficient through the duration of original sub signal to obtain, and said each sub-signals time corresponding conversion coefficient is identical in a same restructuring procedure.This transformation relation can be used following formulate:
T i′＝η i·T i
In the formula, T iIt is the duration of i original sub signal;
η iBe i original sub signal time conversion coefficient;
T i' be the duration of the corresponding adaptation request for utilization of i original sub.
Can know that by projection rule if original echoed signals is broken down into N different subsignal, then each sub-signals time corresponding conversion coefficient is identical: η 1=η 2=...=η i=...=η NIf above-mentioned time change coefficient η iGreater than 1, then represent the original sub signal when time change, the duration is elongated η iDoubly.
According to projection rule, the centre frequency of new subsignal is through original sub signal center frequency f iMultiply by frequency transform coefficients in video codec obtains.The corresponding frequency transform coefficients in video codec of each sub-signals also can require different and different (frequency nonlinear transformation) to the projection of different frequency range subsignal according to the user with can identical (frequency linearity conversion) in restructuring procedure.This transformation relation can be used following formulate:
f i′＝ξ i·f i
In the formula, f iIt is the centre frequency of i original sub signal;
ξ iBe i original sub signal frequency converting coefficient;
f i' be the frequency values of the corresponding adaptation request for utilization of i original sub signal.
Utilize standard trigonometric function (sine function, cosine function) according to the frequency values f that adapts to request for utilization i', duration T i', magnitude rule A i(t) the original sub signal is carried out reconstruct.The reconstruct equation can for:
Figure BDA0000142511600000051
Perhaps do
In the formula, E i(t) be new subsignal after the projective transformation of i sub-signals.Can find out new subsignal E i(t) frequency values is f i', the duration is T i', the amplitude transformation rule is A i(t).
Each original sub signal S i(t) after the projective transformation, obtain new subsignal E i(t) after, new subsignal E i(t) through being combined into complete echoed signal after synthetic the processing.Echoed signal after the reconstruct is compared frequency content and duration change has been taken place simultaneously with original signal.This method has kept most of characteristic of original echoed signals; Improved the discrimination of magnitude and change of frequency in the echoed signal; Can be used for the sonar echo signal to other frequency range signal transition (like sound signal), for the application of broadband ultrasonic echo signal at aspects such as object identification, the exploitations of guide equipment provides technological approaches.
Below in conjunction with two embodiment the present invention is done description in further detail.Embodiment 1 is a broadband ultrasonic echo signal non-linear reconstructing method.Embodiment 2 is the linear reconstructing method of broadband ultrasonic echo signal.
Embodiment 1
The broadband ultrasonic pulse example of Fig. 2 for launching among the present invention, the centre frequency of pulse is 50KHZ, frequency range is 80KHZ-20KHZ.Echoed signal behind reflection object is as shown in Figure 3, also is the preceding broadband ultrasonic echo of reconstruct.Its SF is 1MHZ, and frequency range is about 70KHZ-30KHZ, and the duration is about 400us.The reconstructing method of a kind of broadband ultrasonic echo signal among the present invention can be so that the frequency range non-linear conversion of original broadband ultrasonic echo signal (as shown in Figure 3) be 337.5KHZ-16.25KHZ, and the duration can be elongated and be original 5 times.When the echoed signal after the reconstruct is play through the analog-digital chip of 20KHZ speed; Can produce the sound signal that 6.75KHZ-0.325KHZ, duration are about 100ms; This sound signal has most of characteristic of original echo; The mankind can be particularly suitable for the exploitation of guide blind person aid device material through listening to this sound signal environment-identification.
Specify the implementation step of the non-linear reconstructing method of a kind of broadband ultrasonic echo signal among the present invention below.
Fig. 3 is the broadband ultrasonic echo before the reconstruct.At first use one group of BPF. (using gammatone digital band-pass filter group in the present embodiment) that broadband ultrasonic echo signal shown in Figure 3 is decomposed.Wherein reconstruct resolution is related to the quantity and the bandwidth of subsignal, in the scope of hardware handles ability, according to circumstances regulates setting by the user.Resolution setting in the present embodiment can be: original echoed signals is decomposed into 8 sub-signals; The bandwidth of each subsignal equates (being 5KHZ), and centre frequency is respectively 32.5KHZ, 37.5KHZ, 42.5KHZ, 47.5KHZ, 52.5KHZ, 57.5KHZ, 62.5KHZ, 67.5KHZ.Be that the restructuring procedure of the subsignal (the 5th) of 52.5KHZ is described in detail with regard to centre frequency below, the reconstructing method of all the other subsignals is similar with it.
Fig. 4 example to separate the centre frequency that obtains through gammatone digital band-pass filter component be f 5The subsignal of=52.5KHZ.After obtaining the subsignal of Fig. 4 example, detect in this subsignal in the corresponding peak value of each crest or trough, and press original time order composition peak value sequence A to each peak value 5(t)={ A 51, A 52..., A 5j, A 5N.Centre frequency as shown in Figure 4 is that the peak value sequence that the corresponding peak value of each Wave crest and wave trough of the subsignal of 52.5KHZ is formed is A 5(t)=0.08 ,-7.5,22.8 ..., 1438,1510,1485.1 ..., 305.7}, wherein 0.08 representes first peak value (crest value) ,-7.5 expression second peak value (trough value), 22.8 expression the 3rd peak values (crest value), and the like.Detect 40 peak values altogether.Simultaneously, detect the duration T of this subsignal 5, T in the present embodiment 5=400us.
According to projection rule, the duration of new subsignal is to multiply by the time change coefficient through the duration of signal in the original sub signal to obtain, and said each sub-signals time corresponding conversion coefficient is identical in a same restructuring procedure.This transformation relation can be used following formulate:
T i′＝η i·T i (1)
Wherein, T iBe the duration of i sub-signals, η iBe i sub-signals time change coefficient, T i' be the result of i sub-signals time change.In the present embodiment, the time change coefficient of setting all subsignals is constant 5, i.e. η 1=η 2=...=η i=η N=5, then centre frequency is duration of the subsignal of 52.5KHZ to extend to 2000us by 400us, i.e. T 5'=2000us.
According to projection rule, the centre frequency of new subsignal is through original sub signal center frequency f iMultiply by frequency transform coefficients in video codec and obtain, the corresponding frequency transform coefficients in video codec of each sub-signals also can require different and different (frequency nonlinear transformation) to the projection of different frequency range subsignal according to the user with can identical (frequency linearity conversion) in restructuring procedure.Formulate below should transformation relation can using:
f i′＝ξ i·f i (2)
Wherein, ξ iBe i sub-signals frequency transform coefficients in video codec, f i' be the result of i sub-signals frequency transformation.Frequency transform coefficients in video codec ξ iCan set according to actual needs.In this embodiment, the frequency projective transformation is a nonlinear transformation, so the frequency transform coefficients in video codec of each sub-signals can be different.In the present embodiment, centre frequency is that the subsignal conversion coefficient of 32.5KHZ can be set at 0.5, and then the center frequency value that obtains after the projection is about 16.25KHZ; Centre frequency is that the conversion coefficient of 67.5KHZ can be set at 5, and the center frequency value that then obtains after the projection is about 337.5KHZ.Change of frequency coefficient at 32.5KHZ and 67.5KHZ subsignal between the two can be set between 0.5 to 5, and the echoed signal frequency after can guaranteeing so finally to synthesize is greatly between 337.5KHZ-16.25KHZ.Can set centre frequency is the frequency transform coefficients in video codec ξ of the subsignal of 52.5KHZ 5Be 1.5, then the centre frequency of 52.5KHZ is transformed to 78.75KHZ, i.e. f 5'=78.75KHZ.
Utilize standard trigonometric function (like sine function, cosine function etc.) according to the frequency values f that adapts to request for utilization i', duration T i', magnitude rule A i(t) the original sub signal is carried out the projection conversion.In the present embodiment, the canonical function equation can for:
Figure BDA0000142511600000071
E wherein i(t) be signal after the i sub-signals projection conversion.With A 5(t)=0.08 ,-7.5,22.8 ..., 1438,1510,1485.1 ..., 305.7}, T 5'=2000us, f 5'=78.75KHZ,
Figure BDA0000142511600000072
Bring formula (3) into, then can obtain the subsignal after the 5th sub-signals projection is changed.New subsignal E 5(t) frequency values is 78.75KHZ, and the duration is 2000us, and amplitude is rule and original sub signal S over time 5(t) be consistent.
Each subsignal S i(t) after the projection conversion, obtain new subsignal E i(t) after, the subsignal after these reconstruct can obtain complete echoed signal after synthesizing processing.What the synthetic processing in the present embodiment was used is simple additive operation, and the subsignal that is about to all projection conversions carries out algebraic addition:
E ( t ) = Σ i = 1 N E i ( t ) ;
In the formula, E (t) is the complete echoed signal after the reconstruct;
E i(t) be new subsignal after the projective transformation of i sub-signals;
N representes total N sub-signals, in the present embodiment, and N=8;
Complete echoed signal E (t) after the reconstruct that obtains is as shown in Figure 5.The frequency range of echoed signal shown in Figure 5 is roughly 337.5KHZ-16.25KHZ; Duration is about 2ms; SF is 1MHZ, when this signal is play through the analog-digital chip of 20KHZ speed, can produce the sound signal that 6.75KHZ～0.325KHZ, duration are about 100ms; This sound signal has most of characteristics such as the amplitude, phase place of original echo; And frequency range is wide, longer duration, can help the mankind to pass through the ear perception world as bat, is particularly suitable for the exploitation of sonar guide equipment.
Embodiment 2
Specify the implementation step of the linear reconstruction method of a kind of broadband ultrasonic echo signal among the present invention below.
Fig. 3 is the broadband ultrasonic echo before the reconstruct.At first use one group of BPF. (using gammatone digital band-pass filter group in the present embodiment) that broadband ultrasonic echo signal shown in Figure 3 is decomposed.Wherein reconstruct resolution is related to the quantity and the bandwidth of subsignal, in the scope of hardware handles ability, according to circumstances regulates setting by the user.Resolution setting in the present embodiment can be: original echoed signals is decomposed into 8 sub-signals; The bandwidth of each subsignal equates (being 5KHZ), and centre frequency is respectively 32.5KHZ, 37.5KHZ, 42.5KHZ, 47.5KHZ, 52.5KHZ, 57.5KHZ, 62.5KHZ, 67.5KHZ.Be that the restructuring procedure of the subsignal (the 5th) of 52.5KHZ is described in detail with regard to centre frequency below, the reconstructing method of all the other subsignals is similar with it.
Fig. 4 example to separate the centre frequency that obtains through gammatone digital band-pass filter component be f 5The subsignal of=52.5KHZ.After obtaining the subsignal of Fig. 4 example, detect in this subsignal in the corresponding peak value of each crest or trough, and press original time order composition peak value sequence A to each peak value 5(t)={ A 51, A 52..., A 5j, A 5N.Centre frequency as shown in Figure 4 is that the peak value sequence that the corresponding peak value of each Wave crest and wave trough of the subsignal of 52.5KHZ is formed is A 5(t)=0.08 ,-7.5,22.8 ..., 1438,1510,1485.1 ..., 305.7}, wherein 0.08 representes first peak value (crest value) ,-7.5 expression second peak value (trough value), 22.8 expression the 3rd peak values (crest value), and the like.Detect 40 peak values altogether.Simultaneously, the duration T of detection of echoes signal 5, T in the present embodiment 5=400us.
According to projection rule, the duration of new subsignal is to multiply by the time change coefficient through the duration of signal in the original sub signal to obtain, and said each sub-signals time corresponding conversion coefficient is identical in a same restructuring procedure.This transformation relation can be used following formulate:
T i′＝η i·T i (1)
Wherein, T iBe the duration of i sub-signals, η iBe i sub-signals time change coefficient, T i' be the result of i sub-signals time change.In the present embodiment, the time change coefficient of setting all subsignals is constant 5, i.e. η 1=η 2=...=η i=η N=5, then centre frequency is duration of the subsignal of 52.5KHZ to extend to 2000us by 400us, i.e. T 5'=2000us.
According to projection rule, the centre frequency of new subsignal is through original sub signal center frequency f iMultiply by frequency transform coefficients in video codec and obtain, the corresponding frequency transform coefficients in video codec of each sub-signals also can require different and different (frequency nonlinear transformation) to the projection of different frequency range subsignal according to the user with can identical (frequency linearity conversion) in restructuring procedure.This transformation relation can be used following formulate:
f i′＝ξ i·f i (2)
Wherein, ξ iBe i sub-signals frequency transform coefficients in video codec, f i' be the result of i sub-signals frequency transformation.Frequency transform coefficients in video codec ξ iCan set according to actual needs.During broadband ultrasonic echo signal linear reconstruction, promptly the frequency transform coefficients in video codec of each sub-signals is identical: set ξ 1=ξ 2=...=ξ i=ξ N=0.02.Centre frequency is that the center frequency value that the subsignal projection of 32.5KHZ is converted to is about 0.65KHZ; Centre frequency is about 1.35KHZ for the center frequency value that obtains after the 67.5KHZ projection conversion; Centre frequency is that the center frequency value that obtains after the subsignal projection conversion of 52.5KHZ is about 1.05KHZ, i.e. f 5'=1.05KHZ.
Utilize standard trigonometric function (like sine function, cosine function etc.) according to the frequency values f that adapts to request for utilization i', duration T i', magnitude rule A i(t) the original sub signal is carried out the projection conversion.In the present embodiment, the canonical function equation can for:
Figure BDA0000142511600000091
E wherein i(t) be the signal of i sub-signals projection conversion.With A 5(t)=0.08 ,-7.5,22.8 ..., 1438,1510,1485.1 ..., 305.7}, T 5'=2000us, f 5'=1.05KHZ, Bring formula (3) into, then can obtain the subsignal after the 5th sub-signals projection is changed.
Each subsignal S i(t) after the projection conversion, obtain new subsignal E i(t) after, these new subsignals can obtain complete echoed signal after synthesizing processing.What the synthetic processing in the present embodiment was used is simple additive operation, is about to all new subsignals and carries out algebraic addition:
E ( t ) = Σ i = 1 N E i ( t ) ;
In the formula, E (t) is the complete echoed signal after the reconstruct;
E i(t) be new subsignal after the projective transformation of i sub-signals;
N representes total N sub-signals, in the present embodiment, and N=8;
Through above-mentioned reconstruct, the frequency range of the new echoed signal E (t) that obtains is roughly 0.65KHZ-1.35KHZ, and the duration is about 2ms.
By on can know; The reconstructing method of broadband ultrasonic echo signal of the present invention; Can carry out reconstruct to echoed signal, the echoed signal after the reconstruct has kept most of characteristic of original echoed signals, and the frequency bandwidth of the signal after the reconstruct and duration can be widened or prolong according to demand; Improve the discrimination of echo character, can be adapted to the perception of people's ear better.

Claims (3)

1. the reconstructing method of a broadband ultrasonic echo signal is characterized in that, may further comprise the steps:
Step 1, utilize hyperchannel BPF. group that broadband ultrasonic echo signal is decomposed into different center frequency and band-limited original sub signal according to reconstruct resolution condition;
Step 2, confirm the projection rule of ultrasonic signal to projection signal;
Step 3, detect magnitude rule, the duration of each original sub signal, utilize projection equation afterwards, according to the new subsignal of projection rule structure of step 2;
Step 4, all subsignals that step 3 is constructed synthesize processing, obtain the echoed signal of reconstruct.
2. the reconstructing method of broadband ultrasonic echo signal according to claim 1 is characterized in that, step 2 ultrasonic signal is specially to the projection rule of projection signal:
(1) the magnitude rule according to the new subsignal of projection rule structure is consistent with the magnitude rule of original sub signal, and the waveform distortion rule that also can cause by sonic propagation attenuation law, hardware is on this basis done compensation deals to amplitude;
(2) duration of new subsignal is to multiply by the time change coefficient signal duration through original sub to obtain; Said each sub-signals time corresponding conversion coefficient is identical in a same restructuring procedure;
(3) the centre frequency F of new subsignal iBe through original sub signal center frequency f iMultiply by frequency transform coefficients in video codec ξ iObtain said frequency transform coefficients in video codec ξ iBy self-defined frequency transform function F i=g (f i) provide: ξ i=F i/ f i
3. the reconstructing method of broadband ultrasonic echo signal according to claim 1 is characterized in that, each the original sub signal projection equation described in the step 3 is:
In the formula, E i(t) be the subsignal that the conversion of i original sub signal projection obtains;
A i(t) be the amplitude rule over time of subsignal;
f *(x) be the standard trigonometric function: sine function (sin function) or cosine function (cos function);
f i' for obtain the centre frequency of new subsignal according to the projection rule of claim 2 defined;
Figure FDA0000142511590000012
is the initial phase of standard trigonometric function;
T i' for obtain the duration of new subsignal according to the projection rule of afore mentioned rules; T is a time variable.
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