CN101642378B - Method and device for controlling emitted pulse spectrum in harmonic imaging - Google Patents

Abstract

The invention provides a method and a device for controlling an emitted pulse spectrum in harmonic imaging. The method for controlling the emitted pulse spectrum in the harmonic imaging comprises the step of calculating a time domain waveform by setting at least one target zero frequency and constructing a spectrum function F (omega) according to the set target zero frequency to obtain the waveform of the emitted pulse. On the other hand, the waveform of a special spectrum designed according to the invention embodiment can be realized on a level emission system with asymmetry and the capability for controlling the spectrum by a front emitting end is improved.

Description

The method and apparatus of the emitted pulse spectrum of control harmonic imaging

Technical field

The present invention relates to the control technology of pulse frequency spectrum, be specifically related to relevant pulse frequency spectrum control method and the device of emission with the tissue harmonic imaging (Tissue Harmonic Imaging:THI) of Medical Ultrasonic Imaging System.

Background technology

The medical ultrasound imaging diagnostic device utilizes the propagation of ultrasound wave in human body, obtains the ultrasound wave characteristic information of tissue and organ structure.Present compuscan adopts many array element probes usually.In this system, the high-voltage pulse ripple is carried on each array element of probe, excitation array element produces high-frequency ultrasonic and then forms launching beam and gets into human body.The pop one's head in echo of each array element recipient soma's structural scattering or reflection forms received beam.Compuscan extracts the information in the ultrasonic echo, utilizes various imaging patterns to show.

The THI imaging is a kind of mode of ultra sonic imaging, and it is through the fundamental signal of emission single-frequency, and the high-order harmonic wave component in the reception of echoes extracts the nonlinear characteristic of tissue, forms harmonic image at last.In the THI imaging process; Ultrasonic front end emission fundamental signal gets into tissue, because tissue is a kind of nonlinear propagation medium, first-harmonic can produce higher harmonic components in communication process; Through detecting higher harmonic components, can obtain information with the tissue non linear correlation.Because harmonic signal is produced by nonlinear effect in tissue, its sound field distribution has less secondary lobe with respect to the sound field distribution of first-harmonic, so have less pseudomorphism on the image; On the other hand, because it has shorter wavelength, so it can be higher than first-harmonic to the resolution of tissue.

Yet the non-linear various factors that waits owing to ultrasonic system hardware may comprise harmonic component in transmitting.For example, the high pressure radiating circuit may be introduced harmonic energy in the transmitted pulse before being loaded into impulse wave probe; In addition, the nonlinear effect of probe also may be introduced harmonic component in the transmitted pulse.And the quality of THI imaging depends on the image of the higher hamonic wave formation that produces according to nonlinear effect in the human body; Introduce the harmonic component of not expecting in the transmitted pulse; The downgrade that can cause the THI imaging; Because if transmitted pulse includes significant harmonic component, the harmonic image that then generates thus also will comprise with this harmonic component in the intravital linear propagation of the people information relevant with scattering, this part information will be covered the nonlinear response of tissue.

Therefore, for THI imaging, require the harmonic component in the fundamental waveform frequency spectrum of ultrasonic system emission more weak; For the imaging of emission individual pulse, hope can separate the first-harmonic harmonic in the echo simultaneously, and this just requires the frequency spectrum of transmitted waveform to reduce the main lobe width that the harmonic wave secondary lobe reduces first-harmonic simultaneously as far as possible.

THI imaging at present has dual mode, and a kind of is tissue harmonic, promptly through echo-signal is carried out filtering with the filtering fundamental signal, obtains harmonic components.Another kind is positive and negative harmonic wave, promptly through the waveform of twice anti-phase of emission, with twice echo-signal addition, offsets first-harmonic composition wherein, obtains harmonic signal.Though second method has higher signal to noise ratio than first kind, twice emitting has reduced imaging frame rate.So, still use first method in the occasion of the high frame per second of needs.And first method need reduce the harmonic component in the transmitted pulse as much as possible, thereby makes harmonic component all come from the nonlinear response of tissue.The Filtering Processing of rear end then require in the echo first-harmonic with harmonic wave as far as possible separately, what the main lobe width of first-harmonic should be less than fundamental frequency during this just required to launch is half the.

In a kind of prior art, ultrasonic image-forming system and the method for using the waveform predistortion are disclosed.This method is applicable to the front end system that can launch random waveform, and the control object of its frequency spectrum is based on the carrier signal impulse waveform of gaussian envelope.In this prior art; For the harmonic component in the transmitting of circuit and the non-linear generation of probe system; Offset through adding pre-distorted signals, just, in order to reduce in the transmitted pulse harmonic component with system's non linear correlation; The transmitted waveform that will be the center with the fundamental frequency combines with the predistortion component; Offset the harmonic component in the transmitted pulse, differ 180 degree because the distortion component amplitude of predistortion component and system non-linear generation is identical, this technology is called as the pulse precision Control Technology.Because this scheme is from the sinusoidal carrier signal of gaussian envelope, so can obtain very clean transmitted waveform frequency spectrum.But this front end system of launching random waveform costs an arm and a leg, and only is applied in the high-grade type.Then be to come exomonental in medium-grade model through the multilevel electrical level power-supply system.

According to another kind of prior art, in the multilevel electrical level emission system, a kind of method that produces the pulse signal with low harmonic component through the radiating circuit with symmetric positive negative level is disclosed.In the method, at first given initial two level pulses (" rootwaveform ") then subtract each other " root waveform " with the waveform of its phase shift 180 degree, and its result is equivalent to and on original frequency spectrum, multiply by a factor

Because this factor is at harmonic wave frequency ω=2 ω ₀Has zero point, so the harmonic component in the final waveform has obtained inhibition.Because the restriction of power-supply system, this method has only been considered to construct three level signal from single level signal.Therefore, it can only or subtract through two single level waveform adder and improve waveform, and the waveform frequency spectrum that obtains depends on primary waveform frequency spectrum, so this method has certain limitation to the control ability of frequency spectrum.According to another prior art, the spectrum control method of the carrier pulse signal of the synthetic gaussian envelope of a kind of PWM of employing is disclosed.In the method; Carrier pulse waveform adder through differing 90 degree with two suppresses the harmonic component in the original waveform frequency spectrum; Its result is equivalent to and on original frequency spectrum, multiply by its initial waveform of a factor and taked the synthetic gaussian envelope signal of PWM, and the benefit of doing like this is that Frequency spectrum ratio is cleaner near the fundamental frequency main lobe.

The method of prior art is through with the waveform linear, additive after primary waveform and the time shift or subtract each other the zero point of adjusting frequency spectrum.The waveform that relies on this method to produce, first restriction is that frequency spectrum depends on original waveform, need design original waveform preferably in advance; Second restriction is the addition of the final waveform voltage amplitude level amplitude that is original waveform or subtracts each other, can not regulate arbitrarily, thereby reduce degree of freedom in design.

On the other hand, hardware of the prior art realizes all being based on three level system, promptly have the emission system of symmetric positive and negative level and zero level, and this requirement has limited the ability that front end of emission is controlled frequency spectrum.

Summary of the invention

The present invention provides a kind of method and apparatus of controlling the emitted pulse spectrum of harmonic imaging, has overcome the defective of prior art, and can this main lobe width that suppresses the harmonic component in the transmitted pulse and reduce first-harmonic.For realizing this purpose, the present invention has taked following technical scheme.

An aspect according to the embodiment of the invention provides a kind of method of controlling the emitted pulse spectrum of harmonic imaging, and this method comprises the steps: to set at least one target zero frequency; According to said target zero frequency, structure frequency spectrum function F (ω), the zero frequency of said frequency spectrum function F (ω) comprises said target zero frequency; According to said frequency spectrum function F (ω), calculate time domain waveform, said time domain waveform is transmitted waveform.

According to another aspect of the embodiment of the invention, a kind of device of controlling the emitted pulse spectrum of harmonic imaging is provided, this device comprises: setting module is used to set at least one target zero frequency; Constructing module is used for according to said target zero frequency structure frequency spectrum function F (ω), and the zero frequency of said frequency spectrum function F (ω) comprises said target zero frequency; Computing module is used for calculating time domain waveform according to said frequency spectrum function F (ω), and said time domain waveform is transmitted waveform.

The present invention has improved the pulse method for transmitting of controlling front end of emission in the ultrasonic image-forming system under the THI imaging pattern.Under the THI of ultrasonic image-forming system imaging pattern, need improve the spectrum distribution of transmitted waveform and come to extract better the harmonic component in the echo, improve picture quality.Because the restriction of radiating circuit need be controlled the frequency spectrum of limited level pulse.Method provided by the invention through the structure frequency spectrum, is directly calculated the impulse waveform of limited level according to the pulse frequency spectrum distribution at zero point, controls all zero points of frequency spectrum then, improves frequency spectrum and no longer rely on original waveform; On the other hand; Positive negative level according to the front end of emission of embodiment of the invention design is not necessarily symmetric; On hardware designs, expanded the degree of freedom of art methods like this; Can realize having on the asymmetric level emission system according to the waveform of the particular frequency spectrum of the inventive method design, improved the ability of front end of emission control frequency spectrum.Because method provided by the invention can control all zero points of frequency spectrum, and then can suppress the harmonic component in the transmitted pulse and limit the main lobe width of first-harmonic.

To combine accompanying drawing below and the present invention will be further specified through specific embodiment.

Description of drawings

The flow chart of method shown in Fig. 1 according to the emitted pulse spectrum of the embodiment of the invention, control harmonic imaging;

Shown in Fig. 2 is the impulse waveform that obtains according to one embodiment of the invention;

Shown in Fig. 3 is the impulse waveform that obtains according to another embodiment of the present invention;

Shown in Fig. 4 is the impulse waveform that obtains according to another embodiment of the present invention;

Shown in Fig. 5 according to one embodiment of the invention, add the impulse waveform that obtains before the adjustable voltage;

Shown in Fig. 6 according to one embodiment of the invention, add the impulse waveform that obtains after the adjustable voltage;

The schematic representation of apparatus of emitted pulse spectrum shown in Fig. 7 according to the embodiment of the invention, control harmonic imaging;

Shown in Fig. 8 is seven rank binomial waveforms and corresponding frequency spectrum thereof;

Shown in Fig. 9 is nine rank binomial waveforms and corresponding frequency spectrum thereof;

Figure 10 shows through limiting the main lobe width of first-harmonic zero point;

Shown in Figure 11 is the actual spectrum of seven rank waveforms;

Shown in Figure 12 is the actual spectrum of nine rank waveforms.

The specific embodiment

Because have inhibition near frequency spectrum it zero point that exists in the signal spectrum; Therefore the position through the control spectral null just can suppress the frequency spectrum of certain section, and can limit the width of first-harmonic main lobe and also can suppressed sidelobes near the main lobe zero point through controlling.

Fig. 1 shows the flow chart according to the method for the emitted pulse spectrum embodiment of the invention, the control harmonic imaging, and this method comprises sets at least one target zero frequency (step 100); According to target zero frequency structure frequency spectrum function F (ω) (step 102); Calculate time domain waveform (step 104) according to frequency spectrum function F (ω), the time domain waveform that calculates is transmitted waveform.Frequency spectrum function wherein $F\left(\mathrm{\&omega;}\right)=\frac{M(e^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2008101427899E00061.png,H2008101427899E00062.png"\; state="\{\{state\}\}">t</figure-callout>}}_1},e^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00052.png"\; state="\{\{state\}\}">t</figure-callout>}}_2},\&CenterDot;\&CenterDot;\&CenterDot;,e^{\mathrm{J\&omega;}{t}_n})}{N\left(\mathrm{\&omega;}\right)},$ N is the natural number more than or equal to 1.

In one embodiment;

internal symbol be quantity and the symbol of the positive item that contains the factor be minus contain the factor

quantity equate; Q=1; 2; N, n are the natural number more than or equal to 1.

In another embodiment, $M(e^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2008101427899E00061.png,H2008101427899E00062.png"\; state="\{\{state\}\}">t</figure-callout>}}_1},e^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00052.png"\; state="\{\{state\}\}">t</figure-callout>}}_2},\&CenterDot;\&CenterDot;\&CenterDot;,e^{\mathrm{J\&omega;}{t}_n})$ Comprise at least one factor

1≤k≤n, n are the natural number more than or equal to 1; Wherein $M(e^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2008101427899E00061.png,H2008101427899E00062.png"\; state="\{\{state\}\}">t</figure-callout>}}_1},e^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00052.png"\; state="\{\{state\}\}">t</figure-callout>}}_2},\&CenterDot;\&CenterDot;\&CenterDot;,e^{\mathrm{J\&omega;}{t}_n})=(e^{\mathrm{J\&omega;}{t}_1}-1)\&CenterDot;\&CenterDot;\&CenterDot;(e^{\mathrm{J\&omega;}{t}_m}-1)(e^{\mathrm{J\&omega;}{t}_{m+1}}+1)\&CenterDot;\&CenterDot;\&CenterDot;(e^{\mathrm{J\&omega;}{t}_{m+p}}+1),$ M, p, n are the natural number more than or equal to 1, and m+p≤n.

In yet another embodiment, $M(e^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2008101427899E00061.png,H2008101427899E00062.png"\; state="\{\{state\}\}">t</figure-callout>}}_1},e^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00052.png"\; state="\{\{state\}\}">t</figure-callout>}}_2},\&CenterDot;\&CenterDot;\&CenterDot;,e^{\mathrm{J\&omega;}{t}_n})$ In comprise factor W (ω), $W\left(\mathrm{\&omega;}\right)=\mathrm{\&lambda;}{e}^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2008101427899E00061.png,H2008101427899E00062.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}\&PlusMinus;e^{\mathrm{J\&omega;}{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00052.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}\&PlusMinus;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&PlusMinus;e^{\mathrm{J\&omega;}{t}_h}\&PlusMinus;a,$ N is the natural number greater than 2, and h is the natural number more than or equal to 2, and h is less than n, and a is a constant.

Wherein calculating time domain waveform (step 104) according to frequency spectrum function F (ω) also comprises the steps: according to target zero frequency calculation control time parameter; According to calculation of parameter assembly time in control time parameter; Give weights respectively for the assembly time parameter; The assembly time parameter is arranged according to the order of sequence the time interval that obtains separating; According to weights, calculate the corresponding pulse amplitude of each time interval.Wherein the symbol when assembly time parameter corresponding item after frequency spectrum function F (ω) launches is correct time, for the assembly time parameter is given minus weights; The symbol that launches the corresponding item in back at frequency spectrum function F (ω) when the assembly time parameter is when negative, for the assembly time parameter is given positive weights.Wherein make the pulse amplitude on each time interval equal all the assembly time parameters corresponding weighted value sum littler, obtain the corresponding pulse amplitude of each time interval in view of the above than this time interval upper limit.

Below through the applying examples of method, come the method for the emitted pulse spectrum of the control harmonic imaging of the embodiment of the invention is carried out further detailed explanation according to the emitted pulse spectrum embodiment of the invention, the control harmonic imaging.

In one embodiment, suppose that needing to control transmitted pulse makes its frequency spectrum that arranged 3 kinds of zero points, then can construct the polynomial type frequency spectrum here to do $(e^{\mathrm{I\&omega;}{t}_1}-1)(e^{\mathrm{I\&omega;}{t}_2}-1)(e^{\mathrm{I\&omega;}{t}_3}-1)/\mathrm{\&omega;},$ T wherein ₁, t ₂, t ₃Be the control time parameter, what this frequency spectrum was corresponding is the limited level positive negative pulse stuffing form of time domain.Do all zero points of this frequency spectrum ${\mathrm{\&omega;}}_1=\frac{2\mathrm{M\&pi;}}{{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2008101427899E00061.png,H2008101427899E00062.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}$ , ${\mathrm{\&omega;}}_2=\frac{2\mathrm{N\&pi;}}{{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00052.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}$ , ${\mathrm{\&omega;}}_3=\frac{2\mathrm{L\&pi;}}{{\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00032.png"\; state="\{\{state\}\}">t</figure-callout>}}_3}$ , wherein m, n, 1 are integer, ω ₁, ω ₂, ω ₃The corresponding spectral null frequency of three series can calculate the control time parametric t thus ₁, t ₂, t ₃As long as to t ₁, t ₂, t ₃Carry out reasonable combination, just the position at all zero points in the ability control impuls frequency spectrum.In the present embodiment, suppose t ₁, t ₂, t ₃Putting in order of the assembly time point that produces is t ₁<t ₂<t ₃<t ₁+ t ₂<t ₁+ t ₃<t ₂+ t ₃<t ₁+ t ₂+ t ₃, then 0, t ₁, t ₂, t ₃, t ₁+ t ₂, t ₁+ t ₃, t ₂+ t ₃, t ₁+ t ₂+ t ₃These 8 points are separated 7 time intervals.The symbol that launches pairing of each assembly time parameter of back according to above-mentioned polynomial type frequency spectrum is a plus or minus, comes to give negative or positive weight for this assembly time parameter, and for example above-mentioned polynomial type frequency spectrum launches back t ₁, t ₂, t ₃, t ₁+ t ₂+ t ₃Pairing symbol is for just, so its weight all is-1; And 0, t ₁+ t ₂, t ₁+ t ₃, t ₂+ t ₃Pairing symbol is for negative, thus its weight all be+1, so just can verify in the pulse that pairing pulse amplitude on the above-mentioned time interval equals the weighted value sum that all assembly times littler than this time interval upper limit put, for example, t ₃To t ₁+ t ₂Time interval on pairing pulse amplitude be less than t ₁+ t ₂All point 0 assembly times, t ₁, t ₂, t ₃The weighted value sum that these four time points are corresponding, its result is-2.For less situation of counting, can find that pulse amplitude only gets limited several values.So, can obtain the limited level signal of time domain generally speaking from this polynomial type frequency spectrum.The frequency spectrum positive negative pulse stuffing form that present embodiment obtains is as shown in Figure 2.As shown in the present embodiment,, can calculate corresponding time domain waveform according to the The Distribution of Zeros of frequency spectrum purely, and need not go out to send to improve frequency spectrum from original waveform according to this building method.

Can also design the polynomial type frequency spectrum makes it have the formula of the adding factor simultaneously and for example subtracts the formula factor

; In one embodiment, the polynomial type frequency spectrum is got

$(e^{\mathrm{I\&omega;}{t}_1}-1)(e^{\mathrm{I\&omega;}{t}_2}-1)(e^{\mathrm{I\&omega;}{\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00032.png"\; state="\{\{state\}\}">t</figure-callout>}}_3}+1)/\mathrm{\&omega;},$ All zero points of this frequency spectrum then

For: ${\mathrm{\&omega;}}_1=\frac{2\mathrm{M\&pi;}}{{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2008101427899E00061.png,H2008101427899E00062.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}$ , ${\mathrm{\&omega;}}_2=\frac{(2n+1)\mathrm{\&pi;}}{{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00052.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}$ , ${\mathrm{\&omega;}}_3=\frac{(2l+1)\mathrm{\&pi;}}{{\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00032.png"\; state="\{\{state\}\}">t</figure-callout>}}_3}$ , method that can be same derives the corresponding finite impulse waveform of this frequency spectrum.Same hypothesis t ₁, t ₂, t ₃Putting in order of the assembly time point that produces is t ₁<t ₂<t ₃<t ₁+ t ₂<t ₁+ t ₃<t ₂+ t ₃<t ₁+ t ₂+ t ₃, then 0, t ₁, t ₂, t ₃, t ₁+ t ₂, t ₁+ t ₃, t ₂+ t ₃, t ₁+ t ₂+ t ₃These 8 points are separated 7 time intervals.The symbol that depends on pairing of each assembly time parameter of above-mentioned multinomial frequency spectrum expansion back is a plus or minus, comes to give negative or positive weight for this assembly time parameter, for example, t after above-mentioned multinomial frequency spectrum launches ₁, t ₂, t ₁+ t ₃, t ₂+ t ₃Pairing symbol is for negative, thus its weight all be+1; And 0, t ₁+ t ₂, t ₃, t ₁+ t ₂+ t ₃Pairing symbol is for just, so its weight all is-1.Can verify equally in the pulse that pairing pulse amplitude on these time intervals equals the weighted value sum of all assembly times points littler than this time interval upper limit.The distributed wave of the polynomial type frequency spectrum that present embodiment obtains is as shown in Figure 3.

Can also verify top polynomial type frequency spectrum, as long as contain one

Subtract the formula factor, it just has pairing time domain waveform, because can the polynomial expansion item be combined in twos, every all has

Form, its corresponding center is at (t ₁+ t ₂)/2, width are (t ₁-t ₂) rectangular pulse, the impulse waveform that then whole polynomial type frequency spectrum is corresponding is the stack of these rectangular pulses.When the polynomial type frequency spectrum only contains one

when subtracting the formula factor; What it was corresponding is single-phase many level (all being positive level) pulse, as shown in Figure 4; If the multinomial frequency spectrum contains two or above

and subtracts the formula factor; Its corresponding time domain pulse is positive negative level, shown in Fig. 2 and 3.

If the level value in the power-supply system of multilevel electrical level can be regulated continuously,, can frequency spectrum be designed to following form in order to utilize the continuously adjustable degree of freedom of level

wherein w (ω) factor is the waveform of known frequency spectrum, for example top polynomial type frequency spectrum of being constructed.Add after

factor by the set out method that obtains impulse waveform of frequency spectrum constant; And the weight factor of calculating waveform is-1 with value; + 1, λ and-λ.Because Spectral null satisfies λ=2cos (ω t ₃/ 2), ω t ₂=ω t ₃/ 2+2k π is so λ also can know the control of spectral null.Satisfy and have only limited level; The factor and other level that just need to contain λ in the polynomial expansion do not overlap,

corresponding waveform be that w (t) adds the translation of itself on time domain.For the level that guarantees last signal is only got limited several values; Requirement moves to the zero level zone with the level zone that has of w (t), and can take such method, lets the dutycycle of w (t) be 1/3; Be divided into three class intervals to the time of w (t); Be labeled as 0,1,2 intervals, let the time interval that there is level in w (t) all in 0 interval, 1, the 2 type of time interval that is available lets translation t ₂, t ₃After w (t) occupy, make

Let w (t) be displaced to the 2nd class interval, make

Let w (t) be displaced to the 3rd class interval, like this waveform and original waveform are not overlapping after the translation, and the waveform after the addition just has only fewer level.One of them example such as Fig. 5 and shown in Figure 6; Fig. 5 is for adding the impulse waveform that obtains before

factor, the impulse waveform of Fig. 6 for obtaining through this method after adding

factor.The dutycycle in level zone is 1/3 in Fig. 5, if each pulse width is T/6 in Fig. 5, then gets t ₂=3/6T, t ₁=5/6T adds

Spectral change is as shown in Figure 6 after the factor.Introducing λ can move zero point to a great extent, makes the spectral null skewness, helps controlling the The Distribution of Zeros of local frequency spectrum, thereby has realized adjusting the waveform frequency spectrum effect at zero point through the adjustment voltage amplitude.

More than be to be example, the method according to the embodiment of the invention is illustrated with n=3 (promptly set spectral null 3 situation is arranged).But the present invention is not limited to this, and wherein n can also be 1,2,4,5 or the like.For more general situation, when the spectral null of hypothesis needs had n, then the polynomial type frequency spectrum did

$(e^{\mathrm{I\&omega;}{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2008101427899E00061.png,H2008101427899E00062.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}\&PlusMinus;1)(e^{\mathrm{I\&omega;}{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00052.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}\&PlusMinus;1)......(e^{\mathrm{I\&omega;}{t}_j}\&PlusMinus;1)......(e^{\mathrm{I\&omega;}{t}_n}\&PlusMinus;1)/\mathrm{\&omega;}$ Or

$(e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2008101427899E00061.png,H2008101427899E00062.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}\&PlusMinus;1)(e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2008101427899E00031.png,H2008101427899E00052.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}\&PlusMinus;1)......(e^{\mathrm{i\&omega;}{t}_j}\&PlusMinus;1)......(e^{\mathrm{i\&omega;}{t}_{n-2}}\&PlusMinus;1)(\mathrm{\&lambda;}{e}^{\mathrm{i\&omega;}{t}_{n-1}}-e^{\mathrm{i\&omega;}{t}_n}-1)/\mathrm{\&omega;},$

Wherein

For adding the formula factor,

For subtracting the formula factor, the control time parametric t in each factor of multinomial ₁, t ₂, t ₃... have nothing in common with each other, the assembly time parameter is 0, t ₁, t ₂, t ₃, t ₁+ t ₂, t ₁+ t ₃, t ₂+ t ₃, t ₁+ t ₂+ t ₃..., t ₁+ ...+t _n, other steps can be analogized according to above-described method.

In a word, for general frequency spectrum design, can calculate pairing limited level pulse waveform according to the dead-center position of given frequency spectrum.

Can see that from top description the method for the utilization embodiment of the invention can be through systematically controlling zero point, thereby control the spectrum distribution of limited level pulse signal.And spectral null can be regulated through time and voltage simultaneously, thereby has enlarged the degree of freedom of method of the prior art.

Fig. 7 shows the structured flowchart according to the device of the emitted pulse spectrum embodiment of the invention, the control harmonic imaging, and this device comprises setting module 700, constructing module 702 and computing module 704.Wherein setting module 700 is used to set at least one target zero frequency; Constructing module 702 is used for according to target zero frequency structure frequency spectrum function F (ω), and the zero frequency of said frequency spectrum function F (ω) comprises the target zero frequency; Computing module 704 is used for calculating time domain waveform according to frequency spectrum function F (ω), and the time domain waveform that calculates is transmitted waveform.Computing module 704 also comprises first computing unit 706, second computing unit 708, assignment unit 710, separating element 712 and the 3rd calculating unit 714.Wherein first computing unit 706 is used for according to said target zero frequency calculation control time parameter; Second computing unit 708 is used for according to said calculation of parameter assembly time in control time parameter; Assignment unit 710 is used for giving weights respectively to said assembly time parameter; Separating element 712 is used for said assembly time parameter is arranged the time interval that obtains separating according to the order of sequence; The 3rd calculating unit 714 is used for calculating the corresponding pulse amplitude of each time interval according to said weights.This device can be used for adopting pulse to launch in the system of measuring and forming images.

At last, with combine practical application set forth according to zero point of embodiment of the invention design in the result of practical application that suppresses aspect harmonic wave and the minimizing first-harmonic main lobe width.

1, the progression through zeroing comes harmonic wave is suppressed

If be present in humorous wave point two above zero points simultaneously, then near the frequency spectrum the harmonic frequency can obtain bigger inhibition.Fig. 8 shows frequency spectrum and its corresponding waveform of the humorous wave point existence of control during 7 zero points.On the ultrasonic system that has the variable Pyatyi level system of generating positive and negative voltage, can realize this kind transmitted waveform.

Above limited level waveform be the binomial waveform, the frequency spectrum of binomial waveform can be relatively near Gaussian spectrum, its benefit is that frequency spectrum is clean near the mid frequency main lobe, thereby helps in the THI imaging extraction to harmonic component.

Among Fig. 8 represented be seven rank binomial waveforms with its corresponding frequency spectrum, the coefficient of its waveform from left to right is respectively { 1 ,-6; 15 ,-20,15;-6,1}, this waveform has asymmetric generating positive and negative voltage; Can be through having the front end system emission of asymmetric launching electrical level, the frequency spectrum that in actual transmission, obtains is shown in figure 11.

Another shortcoming of binomial waveform is near triple-frequency harmonics, have than higher frequency spectrum.This shortcoming can be improved through the width of adjusting the rectangular pulse that constitutes the binomial waveform.For the binomial waveform, the rectangular pulse width that constitutes waveform is τ=T ₀/ 2, T ₀Be the cycle of first-harmonic, ${\mathrm{\&omega;}}_0=\frac{2\mathrm{\&pi;}}{{\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="H2008101427899E00022.png,H2008101427899E00031.png"\; state="\{\{state\}\}">T</figure-callout>}}_0}$ Be fundamental frequency,

First (minimum) non-zero-frequency do zero point $\mathrm{\&omega;}=\frac{2\mathrm{\&pi;}}{\mathrm{\&tau;}}=\frac{4\mathrm{\&pi;}}{{\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="H2008101427899E00022.png,H2008101427899E00031.png"\; state="\{\{state\}\}">T</figure-callout>}}_0},$ Just the zero point of harmonic frequency point (all zero points of binomial waveform are all at the second harmonic point),, make first (minimum) be displaced to the triple-frequency harmonics point zero point, just make if adjust the width of rectangular pulse simultaneously $\mathrm{\&omega;}=\frac{2\mathrm{\&pi;}}{\mathrm{\&tau;}}=\frac{6\mathrm{\&pi;}}{{\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="H2008101427899E00022.png,H2008101427899E00031.png"\; state="\{\{state\}\}">T</figure-callout>}}_0},$ Promptly $\mathrm{\&tau;}=\frac{{\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="H2008101427899E00022.png,H2008101427899E00031.png"\; state="\{\{state\}\}">T</figure-callout>}}_0}{3},$ So the rectangular pulse width all is adjusted to $\mathrm{\&tau;}=\frac{{\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="H2008101427899E00022.png,H2008101427899E00031.png"\; state="\{\{state\}\}">T</figure-callout>}}_0}{3},$ Can make move on to the triple-frequency harmonics frequency zero point of frequency spectrum, thereby suppress third-harmonic component.And the n rank binomial waveform frequency spectrum after regulating by this method will become

by

thus through reducing the width of all rectangular pulses simultaneously, can suppress triple-frequency harmonics.And this change is very little near the influence of the frequency spectrum the fundamental frequency.Shown in Figure 9 is that the amplitude of its crest is a binomial coefficient { 1 ,-8,28 through above-mentioned improved nine rank binomial waveforms;-56,70 ,-56,28;-81}, the width at its rectangle peak are reduced so that suppress near the spectrum peak of triple-frequency harmonics, and the frequency spectrum of the actual transmission waveform that it is corresponding is shown in figure 12.

2, through two zero point skinny main lobe

Launch for THI, for the convenience of back Filtering Processing, need reduce first-harmonic and second harmonic overlapping in the echo, this just needs the width of control first-harmonic frequency spectrum main lobe.To this point, can be through near the width that limits main lobe zero point the control main lobe, scheme shown in Figure 10 is passed through ω ₀+ Δ ω, ω ₀-Δ ω limits ω two zero points ₀The main lobe width at place, then the main lobe width among the result equals 2 Δ ω.Say that in principle main lobe width depends on pulse length, and through artificial control, the pulse of design has only under two half period situation in length, its main lobe width can be compared with the square-wave waveform in three cycles.

More than through the specific embodiment the present invention is specified, can not think that the present invention is confined to these specific embodiments.For a person skilled in the art, under the prerequisite that does not break away from essence of the present invention and spirit, can also make amendment and change it, these all should belong to the protection domain of being confirmed by claims of the present invention.

Claims (16)

1. a method of controlling the emitted pulse spectrum of harmonic imaging comprises the steps:

Set at least one target zero frequency;

According to said target zero frequency; Structure frequency spectrum function F (ω); The zero frequency of said frequency spectrum function F (ω) comprises said target zero frequency; Wherein frequency spectrum function

wherein n be natural number more than or equal to 1, ω represents frequency

T is the control time parameter;

According to said frequency spectrum function F (ω), calculate time domain waveform, said time domain waveform is transmitted waveform, wherein calculates corresponding time domain waveform and comprises:

According to said target zero frequency calculation control time parameter;

According to said calculation of parameter assembly time in control time parameter;

Give weights respectively for said assembly time parameter;

Said assembly time parameter is arranged according to the order of sequence the time interval that obtains separating;

Based on said weights, calculate the corresponding pulse amplitude of each time interval.

2. the method for the emitted pulse spectrum of control harmonic imaging as claimed in claim 1; It is characterized in that; In said

; Symbol be quantity and the symbol of the positive item that contains the factor

be minus contain the factor

quantity equate; Q=1 wherein; 2; N, n are the natural number more than or equal to 1.

3. the method for the emitted pulse spectrum of control harmonic imaging as claimed in claim 1; It is characterized in that; Wherein

comprises wherein 1≤k≤n of at least one factor

, and n is the natural number more than or equal to 1.

4. the method for the emitted pulse spectrum of control harmonic imaging as claimed in claim 3 is characterized in that,

$M(e^{j{\mathrm{\&omega;t}}_1},e^{{\mathrm{j\&omega;t}}_2},...,e^{{\mathrm{j\&omega;t}}_n})=(e^{{\mathrm{j\&omega;t}}_1}-1)\&CenterDot;\&CenterDot;\&CenterDot;(e^{j{\mathrm{\&omega;t}}_m}-1)(e^{{\mathrm{j\&omega;t}}_{m+1}}+1)\&CenterDot;\&CenterDot;\&CenterDot;(e^{{\mathrm{j\&omega;t}}_{m+p}}+1),$

Wherein m, p, n are the natural number more than or equal to 1, and m+p≤n.

5. the method for the emitted pulse spectrum of control harmonic imaging as claimed in claim 2 is characterized in that, wherein

In comprise factor W (ω), wherein $W\left(\mathrm{\&omega;}\right)={\mathrm{\&lambda;\; e}}^{{\mathrm{J\&omega;\; t}}_1}\&PlusMinus;e^{\mathrm{J\&omega;}{t}_2}\&PlusMinus;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;e^{{\mathrm{J\&omega;\; t}}_h}\&PlusMinus;a,$ Wherein n is the natural number greater than 2, and h is the natural number more than or equal to 2, and h is less than n, and a is a constant.

6. the method for the emitted pulse spectrum of control harmonic imaging as claimed in claim 1 is characterized in that, wherein N (ω)=ω.

7. the method for the emitted pulse spectrum of control harmonic imaging as claimed in claim 1 is characterized in that, the symbol of said assembly time parameter corresponding item after said frequency spectrum function F (ω) launches is then given minus weights for said assembly time parameter for just; Said assembly time parameter is negative at the symbol that said frequency spectrum function F (ω) launches the corresponding item in back, then gives positive weights for said assembly time parameter.

8. the method for the emitted pulse spectrum of control harmonic imaging as claimed in claim 1; It is characterized in that; Make the pulse amplitude on said each time interval equal all the assembly time parameters corresponding weighted value sum littler, obtain the corresponding pulse amplitude of each time interval in view of the above than this time interval upper limit.

9. device of controlling the emitted pulse spectrum of harmonic imaging comprises:

Setting module is used to set at least one target zero frequency;

Constructing module; Be used for according to said target zero frequency structure frequency spectrum function F (ω); The zero frequency of said frequency spectrum function F (ω) comprises said target zero frequency; Wherein

wherein n be natural number more than or equal to 1; ω represents frequency, and t is the control time parameter;

Computing module is used for calculating time domain waveform according to said frequency spectrum function F (ω), and said time domain waveform is transmitted waveform, and wherein said computing module comprises:

First computing unit is used for according to said target zero frequency calculation control time parameter;

Second computing unit is used for according to said calculation of parameter assembly time in control time parameter;

The assignment unit is used for giving weights respectively to said assembly time parameter;

Separating element is used for said assembly time parameter is arranged the time interval that obtains separating according to the order of sequence;

The 3rd calculating unit is used for calculating the corresponding pulse amplitude of each time interval according to said weights.

10. the device of the emitted pulse spectrum of control harmonic imaging as claimed in claim 9; It is characterized in that; In said

; Symbol be quantity and the symbol of the positive item that contains the factor be minus contain the factor quantity equate; Q=1 wherein; 2; N, n are the natural number more than or equal to 1.

11. the device of the emitted pulse spectrum of control harmonic imaging as claimed in claim 9; It is characterized in that; Wherein

comprises wherein 1≤k≤n of at least one factor

, and n is the natural number more than or equal to 1.

12. the device of the emitted pulse spectrum of control harmonic imaging as claimed in claim 11 is characterized in that,

$M(e^{j{\mathrm{\&omega;t}}_1},e^{{\mathrm{j\&omega;t}}_2},...,e^{{\mathrm{j\&omega;t}}_n})=(e^{{\mathrm{j\&omega;t}}_1}-1)\&CenterDot;\&CenterDot;\&CenterDot;(e^{j{\mathrm{\&omega;t}}_m}-1)(e^{{\mathrm{j\&omega;t}}_{m+1}}+1)\&CenterDot;\&CenterDot;\&CenterDot;(e^{{\mathrm{j\&omega;t}}_{m+p}}+1),$

Wherein m, p, n are the natural number more than or equal to 1, and m+p≤n.

13. the device of the emitted pulse spectrum of control harmonic imaging as claimed in claim 10 is characterized in that, wherein

In comprise factor W (ω), wherein $W\left(\mathrm{\&omega;}\right)={\mathrm{\&lambda;\; e}}^{{\mathrm{J\&omega;\; t}}_1}\&PlusMinus;e^{\mathrm{J\&omega;}{t}_2}\&PlusMinus;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;e^{{\mathrm{J\&omega;\; t}}_h}\&PlusMinus;a,$ Wherein n is the natural number greater than 2, and h is the natural number more than or equal to 2, and h is less than n, and a is a constant.

14. the device of the emitted pulse spectrum of control harmonic imaging as claimed in claim 9 is characterized in that, wherein N (ω)=ω.

15. the device of the emitted pulse spectrum of control harmonic imaging as claimed in claim 9 is characterized in that, the symbol of said assembly time parameter corresponding item after said frequency spectrum function F (ω) launches is then given minus weights for said assembly time parameter for just; Said assembly time parameter is negative at the symbol that said frequency spectrum function F (ω) launches the corresponding item in back, then gives positive weights for said assembly time parameter.

16. the device of the emitted pulse spectrum of control harmonic imaging as claimed in claim 9; It is characterized in that; Make the pulse amplitude on said each time interval equal all the assembly time parameters corresponding weighted value sum littler, obtain the corresponding pulse amplitude of each time interval in view of the above than this time interval upper limit.

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