Method and Device for Increasing the Efficiency of an Emitting Antenna

Abstract

The invention relates to hydroacoustic domain, notably to methods and devices of active location. The method of controlling intercarrier frequency wave efficiency with parametric radiating antenna is based on placing electroacoustic transducer with piezoelement with given resonance frequency (f.sub.1+f.sub.2)/2=f.sub.0 and pass band corresponding to intercarrier frequency wave diapason in locating area, feeding electric signals from radiating tract output to electroacoustic transducer piezoelement, forming in locating area spatial area of collinear distribution and non-linear interaction of intense ultrasound pimp waves, generation of intercarrier frequency wave with cyclic frequency Ω=2π|f.sub.1−f.sub.2|. New features are the following: multicomponent excitation signal if formed due to generating in radiating tract N oscillations with similar amplitude and with similar initial phase at the period of time t=0), with frequencies ω.sub.v, sequentially differing from each other by Ω=2πF_ and situated in pass band of piezoelement and coming from radiating tract output to piezoelement with resonance cyclic frequency ω.sub.0=2πf.sub.0 electric multicomponent signal of escitation, presented as sum of N oscillations and regulation of generation efficiency and adjusting of field parameters (N−1) of intercarrier frequency component wave with cyclical frequencies Ω, 2Ω, . . . , (N−1)Ω formed by parametric radiating antenna, implemented by switching off of antiphase switching on of given constituents set. The method is implemented due to the device that includes reference generator, delayed pulse-shaping circuit, (N−1) coincidence circuit, N frequency dividers, analog switch, adder, amplitude modulator, impulse generator, power amplifier, electroacoustic transducer, controlling and adjustment unit.

Claims

1. A method of controlling efficiency of generation of intercarrier frequency wave by a parametric radiating antenna, the method comprising: placing an electroacoustic transducer having a piezoelement with a given resonance frequency (f.sub.1+f.sub.2)/2=f.sub.0 and a pass band corresponding to a diapason of the intercarrier frequency wave in a locating area; inputting electric signals from an output of a radiating tract to the piezoelement of the electroacoustic transducer, the electric signals having amplitudes varying according to a harmonic law and having values of oscillations frequencies f.sub.1, f.sub.2; spatial area of collinear distribution and non-linear interaction intense ultrasound pump waves, including near and far zones of formed the parametric radiating antenna, is formed in locating medium, intercarrier frequency wave with cyclic frequency Ω=2π|f.sub.1−f.sub.2| is generated, is different in the fact that: forming a multicomponent excitation signal, generating in the radiating tract N oscillations of the same amplitude and with similar initial phase at the moment of time t=0) with frequencies ω.sub.v sequentially differing from each other by Ω=2πF_ and located in piezoelement pass band, feeding from radiating tract to the piezoelement with resonance cyclic frequency ω.sub.0=2πf.sub.0 an electric multicomponent excitation signal, presents and sum of N oscillations, generating in locating area spatial domain of collinear distribution and non-linear interaction of intense N component ultrasound pump wave, including near and far zones of forms parametric radiating antenna, generating in the parametric radiating antenna (N−1) component intercarries frequency wave with cyclical waves Ω, 2Ω, . . . , (N−1)Ω defined by non-linear interaction in distribution medium of given amount of N pump waves spectral components with cyclical frequencies ω.sub.0, ω.sub.1=ω.sub.0+Ω, ω.sub.2=ω.sub.0+2Ω, . . . ω.sub.v=ω.sub.0+NΩ, Adjustment of generation efficiency and correction of field parameters (N−1) component intercarrier wave with cyclical frequencies Ω, 2Ω, . . . , (N−1)Ω of formed the parametric radiating antenna is implemented by switching off or on antiphase switching on of given compounds set of N pump wave spectral components.

2. The method according to claim 1, the method is different in the fact of implementing generation efficiency regulation and the correction of the first component field of intercarrier wave frequency with cyclic frequency Ω by antiphase switching on with respect to the rest central constituents of N pump wave the spectral components.

3. The method according to claim 1, the method is different in the fact of implementing generation efficiency regulation and the correction of the second component field of intercarrier wave frequency with cyclic frequency 2Ω by antiphase switching on central constituents of N pump wave spectral components with respect to the rest, for example, at six-component signal of pumping, the spectral constituents with numbers 3 and 4 with negative amplitudes are used, keeping positive amplitude of constituents 1, 2, 5 and 6.

4. The method according to claim 1, the method is different in the fact of implementing generation efficiency regulation and the correction of the third component field of intercarrier wave frequency with cyclic frequency 3Ω by antiphase switching on the central constituents of N pump wave spectral components with respect to the rest, for example, at six-component signal of pumping, the spectral constituents with numbers 1, 2 and 3 with positive amplitudes are used, keeping negative amplitude of constituents 4, 5 and 6.

5. The method according to claim 1, the method is different in the fact of forming intercarrier frequency wave components with frequencies Ω, 2Ω, . . . , (N−1)Ω taking into account quadratic non-linearity of locating medium and values of its properties values, i.e. non-linear parameter ε, density ρ.sub.0, sound velocity c.sub.0 and attenuation coefficient α.sub.vω and α.sub.(N-1)Ω of multicomponent pump waves and intercarrier frequency providing time and spatial coordination of intense ultrasound multicomponent pump waves.

6. The method according to claim 1, the method is different in the fact of using electroacoustic transducer containing given amount of piezoelements, forming a radiating aperture.

7. The method according to claim 1, the method is different in the fact of using piezoelement mage of piezoceramic and shaped as a bar of resonance size l.sub.bar=c.sub.bar/2f.sub.0, where c.sub.bar is sound velocity on the bar, f.sub.0 is resonance frequency of its oscillations.

8. A device to implement the method contains reference generator, delayed pulse-shaping circuit, (N−1) coincidence circuit, N frequency dividers, analog switch, adder, amplitude modulator, impulse generator, power amplifier, electroacoustic transducer, controlling and adjustment unit and the first reference generator output is connected via delayed pulse-shaping circuit with the second coincidence circuits inputs, outputs of which are connected via frequency dividers with N analog switch signal inputs; and coincidence circuits and dividers often form (N−1) switched on in parallel links, coincidence circuits outputs of previous links are connected with the first coincidence circuits inputs of following links, the first signal analog switch output is connected via frequency divider with reference generator output, connected with coincidence circuit input of the first link of (N−1) coincidence circuits, analog switch output via adder, amplitude modulator and power amplifier connected with electroacoustic transducer input, amplitude modulator control input is connected with impulse generator control output, analog switch control input is connected with the second controlling and adjustment unit output and its first and third outputs are connected respectively with reference generators and impulse generator control inputs.

9. The device according to claim 8, the device is different in the fact of electroacoustic transducer having the piezoelement and also shielding, hydro, electro and noise reduction elements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Claimed method and device is illustrated by the following drawings.

[0102] FIG. 1 presents flow diagram of device to implement the method;

[0103] FIG. 2 presents diagram of electric tension in device;

[0104] FIGS. 3 and 4 present time shape and corresponding spectrum for multicomponent pump signal (at N=5);

[0105] FIG. 5 presents experimental chart of PRA efficiency change from the figure N of used spectral components in multicomponent pumping signal;

[0106] FIG. 6 presents experimental axial distribution of levels of IFW first component sound pressure F_=16.5 kHz for different sets of spectral components in pumping signal: curve 1 stands for six phased components, curve 2 stands for two unphased components (method of initial beating);

[0107] FIG. 7 presents experimental axial distribution of levels of IFW sound pressure components F_=16.5 kHz, 2 F_=33 kHz, 3 F_=49.5 kHz, 4 F_=66 kHz, 5 F_=82.5 kHz (curves 1-5 respectively) for six-component pumping signal;

[0108] FIG. 8 presents experimental angle distribution of levels of IFW first component sound pressure F_=16.5 kHz at phased six-component pumping signal (curve 1) and two unphased components (method of initial beating, curve 2);

[0109] FIGS. 9 and 10 represent information for comparing experiment results, in particular, two sets of axial distribution of levels of IFW sound pressure are presented, generated PRA at different forming modes of pumping signal components and other equal conditions: FIG. 9 shows six phased components (claimed method) of IFW F_=16.5 kHz, 2 F_=33 kHz, 3 F_=49.5 kHz, 4 F_=66 kHz, 5 F_=82.5 kHz (curves 1-5 respectively), FIG. 10 shows two unphased components (method of initial beating), IFW F_=16.5 kHz, 2 F_=33 kHz, 3 F_=49.5 kHz, 4 F_=66 kHz and 5 F_=82.5 kHz (curves 1-5 relatively);

[0110] FIG. 11 presents two diagrams illustrating IFW component attenuation degree F_=16.5 kHz for phased six-component pumping signal from number N of so-called manipulated spectral component that in the course of experiment either switched off (f (A)—dotted line) or switched on in antiphase (f (φ)—solid line);

[0111] FIGS. 12 and 13 present information illustrating the possibility to both controlling PRA efficiency and correcting IFW forming ultrasound field parameters due to “group” manipulation of six-component pumping signal spectral components: FIG. 12 shows pumping signal spectrum S (ω) (the third and the forth spectral compounds are included in antiphase) and a picture of experimental spectrogram for IFW components in aquatic environment for PRA, FIG. 13 shows pumping signal spectrum S (ω) (the forth, the fifth and the sixth spectral components are included in antiphase) and picture of experimental spectrogram for IFW components in aquatic environment for PRA.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0112] The device for method implication (FIGS. 1 and 2) contains reference generator 1, the first output of which is connected via delayed pulse-shaping circuit 2 with second coincide circuits' outputs 3, outputs of which are connected via frequency dividers 4 with N analog switch signal inputs 5. Coincidence circuits 3 and frequency dividers 4 form the same quantity of switched on in parallel links and coincidence circuits outputs 3 from previous links are connected with coincidence circuits 3 first inputs from previous links. Reference generator 1 outputs are connected via frequency divider 4 with the first analog switch 5 signal input and with the first coincidence circuit 3 input of the first link Analog switch 5 output is connected via adder 6, impulse modulator 7, power amplifier 9 with EAT input 10, impulse modulator 7 control input is connected with impulse generator 8 contact output. Controlling and adjustment unit 11 contact outputs are connected with analog switch 5, reference generator 1 and impulse generator 8 controlling inputs.

[0113] Adjustment of PRA operation modes can be automatic and manually by operator.

[0114] Device operation to implement the method of control IFW PRA efficiency generator is following. Operator commands to launch reference generator 1, producing electric signals U1 that are continued sequence of impulses with frequency f.sub.0 at given polarity and phase relations, via control and tuning unit 11. To obtain a set of necessary pumping signal component figures and rearrangement simplicity of intercarrier frequency signal, electric signal U1 is fed to the first coincidence circuit 3 input, meanwhile electric signal U2 is fed from delayed pulse-shaping circuit 2 to coincidence circuit 3 input. Formula for desired spectrum frequency is the following: F.sub.k=[(m−k)/m]×F.sub.0, where m is amount of reference generator 1 impulses, located in carve period and k is the amount of carved impulses; F.sub.0=f.sub.0/2.sup.n, where f.sub.0 is reference generator frequency, 2.sup.n is scaling ratio, n is amount of halving. The scheme defines pumping signal multicomponent spectrum step or intercarrier frequency as F_=F.sub.0/m. Electric signal U2 is fed from delayed pulse-shaping circuit to coincidence circuits 3 second outputs (N−1), coincidence circuits' 3 outputs of which are connected via frequency divider 4 with analog switch 5 N signal inputs and coincidence schemes 3 and frequency divider 4 form the same amount of switched on in parallel links Connecting of coincidence circuits 3 first inputs in links switched in in parallel is carried taking into account that scaling of reference generator 1 should be in every link Thus, coincidence circuits 3 outputs of previous links are connected with coincidence circuits 3 first inputs of following links Electric signal U1 from reference generator 1 is fed via frequency divider 4 to analog switch first signal input and this signal U1 is also fed to coincidence circuit 3 first input from the first link described above. Thus, N oscillations with the same amplitude (U3, U4, U4′, . . . , U4″ and with the same initial phase (at the moment of time t=0) to form multicomponent excitation signal are fed to N signal inputs of analog switch 5, controlling input of which is connected with control and adjustment unit 11 second output, the first and the third outputs of which are connected with reference generator 1 and impulse generator 8 controlling inputs (this connection allows to choose impulse or continued PRA operation mode). Operator's command 12 is received via controlling and adjustment unit 11 with analog switch 5 controlling input; the command 12 sets amount of oscillations necessary to form given implementation of multicomponent excitation signal. This implementation of electric multicomponent excitation signal S (t) formed at adder 6 output is presented as sum of N oscillations by the following formula

[00005]$S\left(t\right)=\underset{v=0}{\overset{N-1}{.Math.}}\sin \left({\omega }_1+v\Omega \right)t=N\left[\sin \left(N\Omega t/2\right)/N\sin \left(\Omega t/2\right)\right]\sin t{\omega }_{m}t,\mathrm{where}{\omega }_m={\omega }_1+\left(N-1\right)\Omega /2\mathrm{and}t=2\pi /N\Omega =1/\mathrm{NF\_},$

[0115] which allows to work with separated N spectral components of excitation signal S(t), i.e. either switch off or switch on in antiphase mode any set of spectral components in radiating tract.

[0116] All oscillation are in phase and form maximum when summed when t=0. However, maximum system through time due to its frequency differences is formed, the first zero is registered at the moment of time t, defined by equality (NΩt/2)=π, where t=2π/NΩ=1/NF_. Denominator zeros define the main maximum, beats period is defined by numbers of main maximums at time unit, i.e. denominator zero values, (Ωt/2)=π.Math.n, where n=0, 1, 2, . . . , where t=n/F_; Δt=1/F_. FIGS. 3 and 4 present temporal shape and spectrum for multicomponent pumping signal (when N=5). FIG. 3 shows that five-component signal envelope curve is complicated, its cyclical basic frequency is 2πf.sub.0 main maximums period is 2π/Ω and dummy zero period is 2π/NΩ. FIG. 4 shows piezoelement pass band having five spectral components of pumping signal with frequencies ω.sub.0, ω.sub.0+Ω, ω.sub.0+2Ω, ω.sub.0+3Ω, ω.sub.0+4Ω, presence on frequency axe of each equals cyclical IFW Ω. Multicomponent pumping signal is fed from adder 6 output to impulse modulator 7, controlling input of which is connected with controlling output of impulse generator 8. Further, after power amplifier 9 signal is fed to piezoelement of acoustic transducer 10. Operation of electroacoustic transducer 10 is the following. Piezoelement fully consists of piezoceramic that can ba shaped as, for example, bar of resonance size l.sub.bar=c.sub.bar/2f (cτ ϰa bar), where c.sub.bar (cτ ϰa bar) is sound velocity in the bar, f.sub.0 is resonance frequency of its oscillations (see Ultrasound. Little encyclopedia. Edited by I. P. Golyamina, Moscow, Soviet Encyclopedia, 1979. 400 pages. Normal oscillations, pp. 237-238, Piezoelement, piezoeffect, pp. 288-289)

[0117] Powerful impulse electric multicomponent excitation signal is fed from radiating tract via hydro, electro and noise reduction elements; this signal's oscillation frequencies can be ω.sub.0, ω.sub.0+Ω, ω.sub.0+2Ω, ω.sub.0+3Ω, ω.sub.0+4Ω, . . . , and can be located in half-wave piezoelement pass band, piezoelement because of its characteristics changes its sizes, i.e. oscillates. This oscillations are transmitted to locating area that has non-linear parameter ε, density ρ.sub.0, sound velocity c.sub.0 and attenuation coefficient α.sub.vω and α.sub.(N-1)Ω of multicomponent pump waves and intercarrier frequency relatively and distributed as U5 impulses containing medium concentration and attenuation. Thus, in medium extended segment, including near and far electroacoustic transducer 10 zones, spatial area of collinear propagation and non-linear interaction of intense pump components with frequencies, for example, ω.sub.0, ω.sub.0+Ω, ω.sub.0+2Ω, ω.sub.0+3Ω, ω.sub.0+4Ω, . . . . In this way, due to quadratic non-linearity of propagation medium and when both time and spatial coordination of intense pump components are implied, spectral components of combination IFW with frequencies Ω, 2Ω, 3Ω, 4Ω, . . . , are formed. Multicomponent pump signal U5 is presented as a sequence of phased spectral constituents, frequencies of which differs from each other by small quantity of cyclical IFW Ω and it can be considered as inphase distributed oscillations in the near electroacoustic transducer 10 zone, because Ω/ω.sub.m<<1. Inphase distribution of interacting intense pump components is equivalent to energy density increase in volume of PRA, which leads to IFW components amplitude growth and energy density increases with interacting pump components amount growth. Main pump energy transfer is directed to the first IFW Ω component, which happens because it is generated by the biggest amount of spectral components of multicomponent pump signal, for example, at five-component pump its sources are formed due to four pair of non-linear interaction of components: 1-2, 2-3, 3-4, 4-5; for the second IFW 2Ω component due—to three pairs of non-linear interaction of components: 1-3, 3-5, 2-4, etc. This, efficiency increase in generation of combination IFW spectral components with frequencies Ω, 2Ω, 3Ω, 4Ω, is more significant for a component n with the lowest frequency. Command also controls analog switch 5 through control and adjustment unit 11; analog switch 5 ensures arrival of necessary amount N of used spectral components in given implication of multicomponent pump signal at adder input 6. FIG. 5 presents experimental graph of behaviour in far PRA efficiency zone on the first IFW component from amount N of used spectral compounds in given implication of multicomponent pump signals. Presented graph shows that expansion in the number of pump spectral components leads to efficiency increase of PRA (when N=3 and 4) and dynamic of efficiency increase of generation at the first IFW component decreases at six-component pumping as transfer to IFW components with higher frequencies takes place. In this way, efficiency control of the first IFW Ω component for PRA, for example, via control and adjustment unit 11 on operator's command can be carried out.

[0118] Options for adjustment IFW Ω, 2Ω, 3Ω, 4Ω, . . . component forming ultrasound field parameters are presented below.

[0119] Advantages of proposed method are verified with experimental researches, carried out in laboratory and given as example.

Example

[0120] EAT 10 with round flat piezoelement with diameter in 20 mm and resonance frequency 1.98 MHz and pass band 200 kHz was used, which allowed operator during the experiment to use 2-6 spectral constituents (consequently distant from each other at F_=16.5 kHz with rigid phase constraint, according to FIGS. 3 and 4) when multicomponent pump signal for PRA is formed. FIG. 6 presents experimental axial distributions of sound pressure levels for the first IFW harmonic F_=16.5 kHz for two given implementation of multicomponent pump signals: curve 1 presents six phased components, curve 2 presents two components (method of initial beating). In both researches radiating average pump signals power, set by operator, didn't change.

[0121] Curves comparison shows that sound pressure level of the first IFW harmonic F_=16.5 kHz at EAT 10 axe for six-component signal is 5 dB more that IFW sound pressure level for two-component. Results of measurements conclude that increase of pump wave energy generation efficiency takes place at using multicomponent signal with rigid phase constraint between its constituents. Proposed method allows operator to form in locating area wide band IFW signal that contains low-frequency harmonics, which is useful in some practical applications, for example, to classify aims, detected in hydroacoustic channel. For this purpose, operator generates a command via control and adjustment unit 11 to analog switch 5 controlling input, ensuring necessary amount N=6 of used spectral constituents sent to adder input 6 in given implementation of multicomponent pump signal. FIG. 7. shows experimental axial distribution of sound pressure levels of spectral constituents of wide band signal, containing IFW harmonics F_=16.5 kHz, 2 F_=33 kHz, 3 F_=49.5 kHz, 4 F_=66 kHz and 5 F_=82.5 kHz (curves 1-5, relatively) for six-component pump signal, measured with hydrophone in far PRA zone.

[0122] Curves show that all five have maximums of different values (from 64 dB to 54 dB) at the same distance (0.18 m) from electroacoustic transducer 10, and the highest value of maximum corresponds to the first IFW harmonic F_=16.5 kHz and the lowest corresponds to the fifth IFW harmonic 5 F_=82.5 kHz. Physical reason of this dependence is described above. Thus, wide band multicomponent IFW signal is formed as a result of non-linear interaction of six pumping signal spectral constituents, which is important when controlling PRA efficiency and adjusting IFW ultrasound forming field parameters. Mode of aims classification, detected in hydroacoustic channel, assumes the possibility to adjust antenna system angular resolution. FIG. 8 dhows experimental angular distribution of sound pressure levels for the first IFW harmonic F_=16.5 kHz at six-component pumping signal (curve 1) and IFW of the same frequency, obtained at non-linear interaction of two unphased components (method of initial beating, curve 2). Comparison of graphs shows that both main lobe angular width and side field level of PRA with multicomponent pumping signal is lower than in two-frequency mode. In this way, there is a possibility to correct IFW forming ultrasound field spatial characteristics.

[0123] FIGS. 9 and 10 show additional information to compare possibilities for operator to correct IFW forming ultrasound field spatial parameters due to the implication of commands via control and adjustment unit 11. It presents results of experimental measurements of groups of two sets of IFW sound pressure levels axial distribution with similar frequencies, generated by PRA at different modes of pumping signal components forming and other equal conditions: —FIG. 9 presents six phased pump constituents (suggested method, where IFW harmonics F_=16.5 kHz, 2 F_=33 kHz, 3 F_=49.5 kHz, 4 F_=66 kHzϰ5 F_=82.5 kHz (curves 1-5, respectively), FIG. 10 shows two pump constituents (method of initial beating, IFW F_=16.5 kHz, 2 F_=33 kHz 3 F_=49.5 kHz, 4 F_=66 kHzϰ5 F_=82.5 kHz (curves 1-5, respectively).

[0124] Analysis of data given above shows that there is a possibility in accordance with suggested method to generate in locating area IFW wide band multicomponent signal, spectrum of which simultaneously have five IFW harmonics F_=16.5 kHz, 2 F_=33 kHz, 3 F_=49.5 kHz, 4 F_=66 kHz H 5 F_=82.5 kHz (FIG. 9, curves 1-5, respectively), while at two pump components (two frequencies beating) it is possible to generate in locating area by one narrow band IFW signal the same frequencies (FIG. 10, curves 1-5 respectively). The differences in amount of interacting spectral constituents in locating area (FIG. 9 shows six pump signal constituents, FIG. 10 shoes two pump signal constituents) leads to, for example, sound pressure IFW level with frequency 16.5 kHz at six-component pumping (FIG. 9 curve 1) exceeds the same value at two-component pumping (FIG. 10 curve 1) by 15 dB (near zone) and 6 dB (far zone).

[0125] It is also possible to control generation efficiency and adjust IFW Ω first component ultrasound field parameters for PRA due to changing of initial phase and amplitude of six-components pumping signal spectral components on command via controlling and adjustment units 11. FIG. 11 presents two diagrams on one field, illustrating attenuation degree of IFW F_=16.5 kHz first component level for phased six-component pumping signal from number N spectral component, that during the experiment either switched off (f (A)—dotted line) on switched on in antiphase (f (φ)—solid line). Analysis of provided data shows: 1) amplitude of the first component IFW to a large extent depends on spectral constituents antiphase switching on than on its absence in spectrum, for example, absence of the third component causes attenuation of the first IFW component F_=16.5 kHz foe 4 dB and antiphase switching on into spectrum attenuates the first IFW harmonic F_=16.5 kHz for 14 dB; 2) Implementing this actions by operator 12, i.e. switching off or antiphase switching on of pumping spectral constituents, adjusts level of the first IFW component F_=16.5 kHz up to different degrees, actions with side components (the first, the second, the fifth and the sixth) have less influence than actions with central components (the third and the forth)

[0126] FIGS. 12 and 13 provide information illustrating the possibility to control efficiency of IFW Ω first component generation efficiency and adjusting parameters of forming ultrasound field due to so called group manipulation of six-component pumping signal spectral constituents: FIG. 12 shows spectrum S(ω) of multicomponent pumping signal (the third and the forth spectral constituencies are in antiphase) and experimental spectrogram picture foe every IFW component in locating area for PRA, FIG. 13 shows spectrum S (ω) of pumping signal (the forth, the fifth and the sixth spectral components are in antiphase) and a picture of experimental spectrogram for all IFW components in locating area.

[0127] Claimed method and device can find wide application in dredging activities, search of silted and flooded subjects, in particular, conduits ay exact profiling and echolocating of the bottom and its layers, contouring enterprises silt emissions and defying its layers thickness, etc. In theses conditions, it is relevant to use hydroacoustic signals of diapason of tens-thousands Hz, formed by PRA with increased IFW generation efficiency.