RU2058561C1 - Method of calibration of parametric radiating antennas and device for its realization - Google Patents

Abstract

FIELD: underwater acoustics. SUBSTANCE: in compliance with this method of calibration of parametric radiating antennas high-frequency pumping signal is emitted on frequencies ω₁ and ω₂ simultaneously with continuous HF signal on frequency ω₃. Amplitudes of discrete components U_Ω1, U_Ω2, U_Ω3 are measured on frequencies Ω₁= ω₁-ω₂,, Ω₂= ω₃-ω₁,, Ω₃= ω₃-ω₂. at reception point. Device for realization of method has radiator 1 of HF pumping signal, measuring hydrophone 2, platform 3 and radiator 4 of HF calibrating signal which is made fast to platform together with measuring hydrophone. Due to positioning of radiator of calibrating signal in close vicinity to measuring hydrophone there is no zone of interaction of acoustic signals on frequencies ω₁, ω₃ и ω₂, ω₃.. If U_Ω1> U_Ω2= U_Ω3,> then there is made conclusion on acoustic origin of received signal on frequency ω₁. If U_Ω1= U_Ω2= U_Ω3,, then there is made conclusion that parasitic signal is registered. EFFECT: enhanced authenticity of method and reliability of device. 2 cl, 4 dwg

Description

 The invention relates to hydroacoustics, in particular to the measurement of parameters of parametric emitting antennas (PIA).

 A feature of the measurement procedures for FIA parameters is that, in addition to the difference frequency, the measuring hydrophone is affected by signals at pump frequencies and parasitic modulation is possible in the receiving path, which does not allow a sufficient degree of accuracy to judge the nature of the received signal (acoustic signal or spurious).

 A known method for calibrating PIA, which implements using measuring paths with a low intrinsic harmonic distortion coefficient, consists in measuring the level of spurious modulation at the output of the path, measuring the amplitude of the difference frequency signal, comparing the measured signal amplitudes and deciding on the acoustic nature of the signal at the difference frequency in the case of excess of its amplitude over the level of spurious modulation.

 The disadvantage of this method is the significant complexity of the calibration, consisting in the fact that this procedure should be carried out for each of the calibrated antennas, taking into account the values of the frequencies and pump levels at which they operate. In addition, the best samples of measuring equipment have a nonlinear distortion coefficient of about 1%, which is often not enough for a correct estimate of the amplitude of the difference frequency against the background of spurious modulation in the receive path.

There is a known method for calibrating PIA, which consists in emitting high-frequency (HF) pump waves at close frequencies ω ₁ and ω ₂ , receiving signals at frequencies ω ₁ , ω ₂ and differential frequency waves (TFC), suppressing pump signals by band-pass filtering at difference frequency ω ₁ ω ₂ Ω measuring the amplitude of the HFG, 0 assuming at the same time that it has an acoustic origin.

 The disadvantage of this method is the low accuracy of the measurements, since the nonlinearity of the hydrophone and the input amplifiers of the measuring path is not taken into account.

The closest in technical essence to the invention is a method for calibrating PIA, which consists in emitting high-frequency acoustic pump waves at frequencies ω ₁ and ω ₂ , absorbing acoustic pump waves to a level that does not cause overloading of the receiving path with an acoustic screen, receiving a difference frequency signal Ω and measuring the amplitude of a difference frequency wave (TFC). It is believed that the received signal has an acoustic origin, since the pump waves ω ₁ and ω ₂ do not affect the measuring hydrophone.

 The method is carried out using a measuring stand containing pump emitters, a measuring hydrophone, between which there is an acoustic screen that absorbs pump waves and transmits the RF.

 The disadvantage of this method is that the degree of attenuation of acoustic waves by the screen is largely dependent on the pump frequency. If the pump frequency is units of megahertz (emitters like NAI), then using a screen of a certain thickness can be quite effective. If the pump frequency lies in the region of tens of kilohertz (sonar type PGL, fish finders like Peskar and Sargan-M), then for the complete absorption of pump waves (≈ 180 dB) it is necessary to significantly increase the thickness of the screen (t. e. its dimensions), which sometimes completely eliminates the use of the screen.

 The disadvantage is that for each individual type of measured PIA, it is necessary to calculate, manufacture and calibrate your screen, which entails unreasonably high costs of time and material resources.

 The purpose of the invention is to improve the accuracy of the calibration of the FIA and reduce material and time costs.

 In FIG. 1 shows a diagram of a device for implementing the proposed method.

 The device for calibrating the PIA contains an emitter of the RF pump signal 1, a measuring receiving hydrophone 2, located on the rotary device 3, an RF radiator of the calibration signal 4, spatially combined with the measuring hydrophone 2.

 The calibration method of the PIA is as follows.

)
Ω₂ ω₃ ω ₁ (U

)
Ω₃= ω₃ ω ₂ (U

), сравнивают полученные величины и если U_Ω1 > U_Ω2=U_Ω3, делают вывод об акустическом происхождении принимаемого сигнала, а при U_Ω1 U_Ω2=U_Ω3 делают вывод о том, что регистрируется паразитный сигнал.Using the emitter of the RF pump signal 1 in the direction of the measuring hydrophone 2 emit the RF pump waves at frequencies ω ₁ and ω ₂ , using the measuring hydrophone 2 receive the wave of the difference frequency (VCR) Ω ₁ ≈ ω ₁ ω ₂ and measure its amplitude . Simultaneously with the emission of the pump signal using the emitter 4, a continuous high-frequency calibration signal is emitted at a frequency of ω ₃ , which is selected from the condition that the sensitivity of the hydrophone is equal at frequencies of ω ₁ , ω ₂ and ω ₃ , and the signal amplitude at a frequency of ω ₃ is set equal to the amplitude of the signals at frequencies ω ₁ and ω ₂ at the location of the measuring hydrophone, measure the amplitudes of the discrete components at frequencies
Ω ₁ = ω ₁ ω 2 (U

)
Ω ₂ ω ₃ ω ₁ (U

)
Ω ₃ = ω ₃ ω ₂ (U

), compare the obtained values and if U _Ω1 > U _Ω2 = U _Ω3 , draw a conclusion about the acoustic origin of the received signal, and at U _Ω1 U _Ω2 = U _Ω3 conclude that a stray signal is detected.

In the spectral representation at the hydrophone output are observed (see figure 2):
discrete components (DS) at frequencies ω ₁ and ω ₂ pump signals;
DS at a frequency of Ω _{1 is a} difference frequency signal resulting from the nonlinear interaction of acoustic pump waves in the volume of an aqueous medium from a pump emitter to a measuring hydrophone; a useful signal for FIA;
DS at a frequency of ω ₃ HF calibration signal;
DS at frequencies Ω ₂ and Ω ₃ , with Ω ₂ ω ₃ ω ₁ and Ω ₃ ω ₃ ω ₂ calibration differential-frequency signals arising due to spurious interaction of signals in the receiving measuring path, since the calibration emitter is combined with the measuring hydrophone and the acoustic zone there is no signal interaction.

, U

), обусловленных паразитным взаимодействием в приемном тракте.When calibrating the PIA, the amplitude of the DS at the frequency Ω ₁ , due to the interaction of acoustic waves, and the amplitude of the DS at frequencies of Ω ₂ and Ω ₃ (U

, U

) due to spurious interaction in the receiving tract.

> >U

принимают решение о том, что ДС на частоте 1 имеет акустическое происхождение и производят измерение параметров ПИА (звукового давления и пространственного распределения его амплитуд).If condition U

>> U

decide that the DS at frequency 1 has an acoustic origin and measure the PIA parameters (sound pressure and spatial distribution of its amplitudes).

If U _Ω1 U _Ω2 = U _Ω3 , then it is obvious that he is dealing with a spurious acoustic signal that does not allow a qualitative assessment of the acoustic parameters of the FIA. In this case, the measurements are stopped.

), Ω₂ ω₃ ω ₁ (U

)Ω₃= ω₃ ω ₂ (U

),
Отличительными признакам предложенного устройства являются: наличие высокочастотного излучателя калибровочного сигнала; конструктивно излучатель калибровочного сигнала совмещен с измерительным гидрофоном.Distinctive features of the proposed method are: the radiation of a continuous calibration RF signal at the location of the measuring hydrophone; the radiation of the calibration signal simultaneously with the radiation of the pump signal; radiation of the calibration signal at a frequency of ω ₃ , which is selected from the condition of equality of sensitivity of the hydrophone at frequencies ω ₁ , ω ₂ and ω ₃ ; the amplitude of the calibration RF signal at a frequency of ω _{3 is} set equal to the amplitudes of the signals at frequencies ω ₁ and ω ₂ at the location of the measuring hydrophone by adjusting the radiation level; measurement of the amplitudes of the PM at frequencies Ω ₁ = ω ₁ ω 2 (U

), Ω ₂ ω ₃ ω ₁ (U

) Ω ₃ = ω ₃ ω ₂ (U

),
Distinctive features of the proposed device are: the presence of a high-frequency emitter of the calibration signal; structurally, the emitter of the calibration signal is combined with a measuring hydrophone.

 The presence of distinctive features from the prototype signs allows us to conclude that the claimed device meets the criterion of "novelty."

 PRI me R. Using a pump emitter in the direction of the measuring hydrophone, pump waves were emitted at close frequencies of 17 and 18 kHz. The frequency dependence of the sensitivity of the measuring hydrophone is presented in figure 3.

Simultaneously with the pump signal, a calibration signal was emitted using the RF emitter of the calibration signal, the frequency of which was chosen from the condition that the sensitivity of the measuring hydrophone was equal at frequencies ω ₁ ω ₂ ω ₃ and was 19 kHz (see Fig. 3). The difference frequency signal was received by a measuring hydrophone, which is combined with a calibration emitter.

 Due to the fact that the procedure for measuring the nonlinearity parameter of the aquatic environment is difficult, this process was simulated by changing the coefficient of nonlinear distortion of the measuring path connected to the measuring hydrophone. In the first case, a path with a nonlinear distortion coefficient of ≈1% was used, and in the second ≈3%, the measurement results were recorded using a t2031 spectrum analyzer. The results of two experiments are presented in figure 4.

An analysis of the results allows us to conclude that in the first case, U _Ω1 > U _Ω2 = U _Ω3 (see _Fig. 4, a) and the DS at a frequency of 1 kHz has an acoustic origin, and in the second case, U _Ω1 U _Ω2 = U _Ω3 (see _Fig. 4, b) and a DS at a frequency of 1 kHz is parasitic and further measurements of the acoustic parameters of the FIA are impractical.

Claims (2)

1. A method for calibrating parametric radiating antennas, which consists in emitting high-frequency acoustic pump waves at close frequencies ω ₁ and ω ₂ , receiving differential frequency signals Ω = ω ₁ -ω _{2 by a} measuring hydrophone, measuring the amplitude of the differential frequency signal Ω ₁ , characterized in that at the point of location of the measuring hydrophone, simultaneously with the radiation of the pump signal, a continuous calibration high-frequency signal is additionally emitted at a frequency of ω ₃ , which is chosen from the condition that the sensitivity of the hydrophonic at frequencies ω ₁ , ω ₂ and ω ₃ , and the signal amplitude at frequency ω ₃ by adjusting the radiation level is set equal to the amplitude of signals at frequencies ω ₁ and ω ₂ , at the location of the measuring hydrophone, the amplitudes of the discrete components UΩ ₁ , UΩ _{2 are} measured , UΩ ₃ at frequencies
Ω ₁ = ω ₁ -ω ₂ , Ω ₂ = ω ₃ -ω ₁ , Ω ₃ = ω ₃ -ω ₂ ,
compare the obtained values and, if UΩ ₁ > UΩ ₂ = UΩ ₃ , conclude the acoustic origin of the received signal, and if UΩ ₁ = UΩ ₂ = UΩ ₃ , conclude that a stray signal is detected.  2. A device for calibrating parametric emitting antennas containing high-frequency pump emitters, a measuring hydrophone located on the antenna rotator, characterized in that it is additionally equipped with a high-frequency emitter of the calibration signal, which is combined with the measuring receiving hydrophone.

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