RU58731U1 - RADIODALMER WITH CONTINUOUS RADIATION OF FREQUENCY-MODULATED RADIO WAVES - Google Patents

Abstract

The invention relates to the field of measurement technology, in particular, to measuring distance, for example, in closed tanks, and is based on the principle of continuous-wave radar and frequency modulation of the probe signal.

The technical result of the utility model is to reduce the error of distance measurement by reducing the influence of the AFC signal distortions, transients and due to the possibility of reducing the influence of interference.

A radio range finder with continuous emission of frequency-modulated radio waves contains an antenna, a microwave transmitting and receiving module with a controlled sounding signal source (UISS) made with one input and two outputs, the first and second directional couplers (NO) and a mixer (SM), an analogue preliminary processing circuit (SPAO), which includes a differential frequency signal amplifier, a frequency synthesizer (MF) with two inputs and two outputs, and a digital signal processing circuit (SCOS) with two inputs and two outputs. The first UIZS output is connected to the antenna input through the first and second BUT, the second UISS output is connected to the first MF input, and the input is connected to the first MF output, the second outputs of the first and second BUT are connected, respectively, to the first and second SM inputs, and the SM output It is connected to the input of the secondary open source system, the output of the secondary open source is connected to the first input of the center, the second input of the center is connected to the second output of the midrange, and the first output of the center is connected to the second input of the middle, while the second output of the center is the output of the device.

Description

The invention relates to the field of measurement technology, in particular, to measuring distance, for example, in closed tanks, and is based on the principle of continuous-wave radar and frequency modulation of the probe signal.

Known radar distance meter with continuous frequency-modulated radiation of the probe signal, comprising an ultra-high frequency (microwave) generator, a modulator, a transmitting and receiving antenna, a mixer, a differential frequency signal amplifier (RFM), a frequency meter and a distance calculator [1, p. 95, 96]. The operation of the meter is based on counting the number of periods of the differential frequency signal (RMS) on the modulation period. The disadvantage of this meter is the low accuracy of distance measurement.

Known radar distance meter with continuous frequency-modulated radiation of the probe signal [2, p. 324; 3], in which the operation of the calculator is based on spectral analysis of the RF signal. For some cases, the specified radar distance meter also has insufficient accuracy of distance measurement.

Known radar distance meters with parametric methods for processing signals by a computer [4]. The disadvantage of these meters is the high sensitivity to signal distortion due to transients.

All known radar distance meters have common interconnected disadvantages that are caused by periodic frequency modulation in a limited range. The first drawback is

in that at the moment of crossing the frequency dependence of the received echo of the signal of the frequency dependence of the probing signal in the RF, phase jumps occur. At these moments (they are usually called the “circulation zone”), the derivative of the RMS has a gap. Due to the fact that the RFM processing circuits have frequency-dependent circuits or reactive elements, amplitude and phase-frequency (AFC) signal distortions and transients occur in them. Transients in correctly executed circuits quickly decay, but inevitably present and distort the processed passive frequency response and, accordingly, lead to measurement errors for any signal processing methods and a decrease in resolution. Distortion of the RFS due to transients is manifested, in particular, in the inconstancy of the periods of the RFI. Influence of interference also leads to inconsistency of the RF periods. Thus, transients make it difficult to determine the cause of distortion. Decrease in resolution, i.e. the ability to isolate the signal of the sensed surface from interference, such as structural elements of the material, in turn increases the error. In spectral processing of the RMS, a decrease in resolution is caused by the expansion of the signal spectrum, and when using well-known high-resolution methods based on linear models, for example, the maximum likelihood method (MMP) [4; 5; 6, p. 483] and others, a decrease in resolution and an increase in error are due to the mismatch between the really allocated RMS and the idealized mathematical models of signals used as standards.

Errors caused by transients cannot be distinguished in the form of systematic ones, because transient parameters depend on input actions, which in turn depend on changing distances to reflectors.

The second drawback, due to the limited modulation range, the presence of frequency-dependent circuits and, therefore, the AFC distortion of the signal, is that the generated frequency

the modulated signal is accompanied by spurious amplitude modulation (PAM). As a result, the RFS is also modulated in amplitude. The passage of an amplitude-modulated signal along frequency-dependent circuits leads to a shift in the position of the spectrum maximum. As a result, a measurement error arises, which also cannot be taken into account as systematic, because PAM parameters change with temperature, aging elements and other factors.

There is a radio range finder that is not sensitive to APS signal distortions with continuous emission of frequency-modulated radio waves [7] (prototype), which contains a microwave transmit-receive module with an antenna, a symmetric triangular voltage driver, a RF amplifier and a frequency meter, a modulator, a frequency label generator, and an analog multiplier, time interval discriminator, integrator, extremum extraction scheme, and control scheme. The operation of the specified radio range finder includes generating a radio frequency signal with symmetric periodic frequency modulation, emitting radio waves in the direction of the probed material, extracting a part of the generated signal, receiving an echo of the signal and mixing it with the extracted part of the generated signal, isolating the low-frequency components of the resulting difference frequency signal (RFM), amplifying the extracted RF system for processing the RF system, calculating the propagation time of radio waves, calculating the distance and adapting the range odulyatsii for APS without phase jumps in the "treatment zone". As a result, transient exclusions should be expected. However, echo signals from a plurality of reflectors and, inter alia, from inhomogeneities of the antenna-waveguide system, usually come to the input of the receiver of the range finder. The parameters of most reflectors change over time. Obviously, one modulation range can be adapted for several reflectors only if they are located exactly at the same electrodynamic distance from the phase center of the radio range finder antenna, which is never done. Another source

excitation of transients is the probe signal generator itself, part of the power of which is allocated for mixing with the echo signal. Transients occur due to the frequency dependence of the generated power of the probe signal.

The technical result of the utility model is to reduce the error of distance measurement by reducing the influence of the AFC signal distortions, transients and due to the possibility of reducing the influence of interference.

The specified technical result is achieved by the fact that, in a radio range finder with continuous emission of frequency - modulated radio waves, containing an antenna, a microwave transmitting and receiving module, including a controlled sounding signal source (UISS), the first and second directional couplers (BUT) (or circulator) and a mixer (SM), a pre-analog processing circuit (SAW), and a frequency meter are additionally introduced; a frequency synthesizer (MF) with two inputs and two outputs and a digital signal processing circuit (DSP) with two inputs and two outputs, and a controlled sounding signal source (UIZS) is made with one input and two outputs. In this case, the first output of the UIZS is connected to the input of the antenna through the first and second BUT. The second UIZS output is connected to the first midrange input, and the input is connected to the first midrange output. The second outputs of the first and second BUT are connected, respectively, with the first and second inputs of the SM, and the output of the SM is connected to the input of the SPAO. The output of the SPAO is connected to the first input of the center. The second input of the center is connected to the second output of the midrange, and the first output of the center is connected to the second input of the midrange. The second output of the alarm system is the output of the device.

SECS can be performed standard, containing a synchronization pulse generator, an analog-to-digital converter (ADC) and a digital processor, including a memory device, an arithmetic device, and to measure the frequency.

The presence of a connection between the first output of the center of reference and the second input of the midrange allows you to change the modulation range to reduce the effect of interference.

The analysis of the prior art, including a search by patent and scientific and technical sources of information and identification of sources containing information about analogues of the claimed invention, allows us to establish that the applicant has not found technical solutions characterized by features identical to all the essential features of the claimed invention. The definition from the list of identified analogues of the prototype made it possible to identify a set of essential (in relation to the technical result perceived by the applicant) distinctive features in the claimed object set forth in the claims. Therefore, the claimed invention meets the requirement of "novelty" under applicable law. Information about the fame of the distinguishing features in the totality of the characteristics of the known technical solutions with the achievement of the same as the claimed device, there is no positive effect. Based on this, it was concluded that the proposed technical solution meets the criterion of "inventive step".

The operation of the proposed device depicted in figure 1 is explained using the diagrams depicted in figure 2, figure 3.

Figure 2 shows the frequency dependence of the probing signal.

Figure 3 shows a variant of the formation of PSRCH with stepwise increasing amplitude factor.

The device contains a circuit for digital signal processing (SES) 1 with two inputs and two outputs, a circuit for preliminary analog processing (SPAO) 2, a mixer (SM) 3, a first directional coupler (BUT) 4, a second, BUT 5 (or circulator), an antenna 6, a frequency synthesizer (MF) 7 with two inputs and two outputs, a controlled sounding signal source (UISS) 8 with one input and two outputs. The first output of the UIZS 8 is connected to the input of the antenna 6 through the first 4, second 5 BUT. The second output of the UIZS 8 is connected to the first input of the midrange 7, and the input is connected to the first output of the midrange 7. The second outputs of the first 4 and second 5 NO are connected, respectively, to the first and second inputs of SM 3, and the output of SM 3 is connected to the input of the SPAO 2.

The output of the SPAO 2 is connected to the first input of the MSC 1. The second input of the MSC 1 is connected to the second output of the MF 7, and the first output of MSC 1 is connected to the second input of the MF 7. The second output of MSC 1 is the output of the device. STSOS 1 can be performed standard, containing a synchronization pulse generator, an analog-to-digital converter (ADC) and a digital processor, including a memory device and an arithmetic device.

The practical implementation of the device is not difficult and is carried out on the basis of widely distributed electronic elements, for example, manufactured by ANALOG DEVICES, MOTOROLA, MICRONETICS, PEREGRINE, etc.

A radio range finder with continuous emission of frequency-modulated radio waves operates as follows.

The generated radio frequency signal with symmetric periodic frequency modulation F (t) according to the linear law (Figure 2) from the UIZS 8 (Figure 1), controlled by the frequency synthesizer 7, through the first HO 4, the second HO 5, enters the antenna 6, is radiated, and after reflection from the sensed surface, it is received by antenna 6 and fed through mixer 5 to the input of mixer 3. As a reference, the allocated part 4 of the power of the generated signal is used. The output signal of the mixer U _{cfcm is} processed by the _SDAO 2 with a gain of k (j Ω) (where Ω is the current frequency value) and is fed to the first input of the SCNS 1. The second input of the SCNS 1 receives the frequency values from the midrange 7. Using SCOS 1, all actions on the HRE. The input signal of the center 1 is multiplied by the factor A (j Ω) = A ₀ / k (j Ω), which is inversely proportional to the gain of the SPAO 2 (A ₀ is a constant coefficient). (In Fig. 3, curve 9 shows the processed signal with A ₀ = 1 and k (j Ω) independent of frequency). During the operation of the radio range finder, the formation of the factor A (j Ω) is possible inversely proportional to the amplification factor of the SDAO 2k (j Ω) only in the main frequency band of the input signal. Outside the main frequency band of the input signal, the generated factor A (j Ω) may be equal to zero. From the resulting PSRCH U _{srrsm cpp} = U k (j Ω) A ₀ / k (j Ω) in STSOS 1 comprising

a memory unit 10 (FIG. 3), form a PSRCH 11 corresponding to one half-period of T / 2 modulation. To do this, additionally multiply the PSRCH obtained at each half-period of modulation by a factor in the form of a function that increases from the beginning to the end of the half-period of modulation, summarize the PSRCH obtained for the second half-period of modulation with a reversed copy of the PSRCH obtained for the first half-period of modulation. Multiplication of the input signal by the factor A (j Ω) is performed, for example, in a known manner [8, p. 174]. The RMS readings from the output of the SPAO 2 are fed to the input of the SRMS 1. Using the SCLS 1, a discrete Fourier transform (DFT) is performed, as a result of which the spectrum of the SRMS 1 input for the SRS is obtained. The samples of the factor A (j Ω) are formed, which are multiplied with the spectrum of the input signal and perform the inverse discrete Fourier transform (ODPF). As a result, PSRCH readings are obtained.

Discrete samples of the PSRCH of the first half-period of modulation are multiplied by a factor in the form of a function that grows from the beginning to the end of the half-period of modulation. The function, which is the amplitude multiplier of the PSRCH, must meet the condition that the sum of the amplitudes of the additionally multiplied PSRCH obtained at the second half-period of modulation is equal to the inverse copy of the PSRCh obtained at the first half-period of modulation, the amplitude of the PSRCh. It is advisable to use, for example, a function that linearly increases within each half-period of modulation, or sin ² (2πt / T), where T is the period of modulation, t is the current time inside the half-period of modulation, or 1-sign [sin [4πt / T)] , where sign [sin (4πt / T)] is the signal function, unity at [sin (4πt / T)]> 0 and equal to minus unity at [sin (4πt / T)] <0.

When using the latter function, the amplitude of half of the additionally multiplied PSRCH samples is zero and the implementation of the distance measurement method is simplified. In this case, the formation of the PSRCH 11 is carried out by replacing a part of the PSRCH (distorted fragment 12 of the PSRCH in the interval T _1.2 obtained in the first half of the second half-period of modulation, the inverse copy of the part of PSRCH (undistorted fragment 13 of the PSRCH in the interval T _2.1 ) obtained for the second half of the first half-cycle

modulation. These actions are performed, for example, as follows. Discrete samples of the PSRCH of the second half of the first half-period of modulation on the interval T _2,1 with numbers 1, 2, ..., n-1, n are recorded in the cells of the memory block 10 of SEC 1, respectively, with numbers n, n-1, .. ., 2, 1. Thus, the first sample of the PSRCH fragment in the interval T _{2.1 is} recorded in the last cell of half of the memory block 10, and the last sample of the PSRCH fragment in the interval T _{2.1 is} recorded in the first cell of the memory block. Accordingly, the readings of the PSRCH over the entire interval T _2,1 are recorded. Discrete samples of the PSRCH of the second half of the second half-period of modulation on the interval T _2.2 with numbers n + 1, n + 2, ..., 2n-1, 2n are recorded in the cells of memory block 10 SSC 1, respectively, with numbers n + 1, n + 2, ..., 2n-1, 2n. Thus, the numbers of the recorded samples of the undistorted fragment 13 of the PSRCH in the interval T _2.2 coincide with the cell numbers of the memory block. After recording the PSRCH samples on two halves of the modulation half-cycle, discrete samples are used in the order of memory cell numbers. The result is a formed PSRCH at a half-period of modulation, in which the AFC distortions and transients are reduced (Figure 3, curve 11). If necessary, to increase the signal-to-noise ratio, the signal can be accumulated by recording samples with the same numbers for many periods of modulation (Fig. 3 - dashed arrows 14, 15, 16, 17).

In the general case, the number of discrete samples used for each half-period of modulation is 2n. Therefore, all discrete samples of both the first and second half-periods of modulation are recorded in 2n memory cells, but with different weights. Discrete samples of the PSRCH of the first half-period of modulation with numbers 1, 2, ..., 2n-1, 2n are multiplied by a factor in the form of a function that grows from the beginning to the end of the half-period of modulation and recorded in the cells of the memory block 10 of SEC 1, respectively, with numbers 2n , 2n-1, ..., 2, 1. Thus, the first multiplied sample of the first half-period of modulation is recorded in the last cell of the memory block 10, and the last sample of the first half-period of modulation is recorded in the first cell of the memory block. Discrete samples of the PSRCH of the second modulation half-cycle with numbers 1, 2,

..., 2n-1, 2n are multiplied by a factor in the form of a function that grows from the beginning to the end of the half-period of modulation and is written into the cells of the memory block 10 of SCE 1, respectively, with numbers 1, 2, ..., 2n-1, 2n . Thus, the numbers of the recorded samples of the PSRCH fragment of the second modulation half-cycle coincide with the cell numbers of the memory block. As a result, the formed PSRCH at the half-period of modulation is also obtained, in which the AFC distortions and transients are reduced.

Then, the correspondence of the parameters of the PSRCH thus formed to the reference parameters is determined and, when the parameters of the generated signal correspond to the reference parameters, they are used to calculate the distance. In this case, you can use any method of processing PSRCH. For example, the maximum likelihood method [6, p. 483], the Prony method [5], counting and other methods. Obviously, by performing such actions with the PSRCH, it is possible to obtain an undistorted signal at any (increasing or decreasing in frequency) half-period of modulation, and also, if necessary, form a continuous and undistorted PSRCH,

If the parameters of the generated PSRCH do not correspond to the reference, then two PSRCH, PSRCH1 and PSRCH2, corresponding to one half-period of modulation, are formed. In this case, PSRCH1 is formed as described above with the recording of the generated samples in 2n cells of the part of the memory block containing 8n cells. And to obtain PSRCH2 summarize PSRCH obtained at the first half-cycle of modulation with a reversed copy of PSRCH obtained for the second half-period of modulation and write the generated samples to other cells of the memory block. From the PSRCH1 and PSRCH2 thus formed, the total and difference TPS, the TPSS and the RFRS are calculated, 2n cells of the memory block are used to record each of them. A measure of the difference in the parameters of the obtained MIFS and RFRS from the reference parameters is determined, and if a measure of the difference in the parameters of one of them from the reference parameters is below the control level, use this MIF or the MIFR to calculate the distance. And if the measure of difference between the parameters of both the HFRS and the RFRS from the reference parameters exceeds the control level, the central frequency is changed

modulation range and perform new measurements until the measure reaches the difference in the control level. In this case, you can also use any method of signal processing.

Since the undistorted (reference) MFR must have constant periods at the half-period of modulation, the deviation of the durations of the periods of the generated MHD or MHD from the constant value at the half-period of the modulation during signal processing using a method based on counting the number of periods of the generated signal at the half-period of modulation can serve as a measure of difference . In the spectral processing of the SSSR and RFRS, a measure of the difference from the reference parameters can be the magnitude of the asymmetry of the spectrum and the width of the main lobe of the spectrum.

The difference between the RMS parameters from the reference ones, one of which can be the constancy of periods, is caused by two reasons. The first reason - the effect of transients - is ruled out by the formation of the PSRCH. The second reason - the influence of the interfering signal - is excluded by the formation of the RF system and RFRS and by changing the center frequency of the modulation range. The latter is explained as follows. As a result of the considered actions on the UHF, two undistorted PSRCH1 signals - u _n (t) and PSRCH2 - u _cn (t), respectively, are obtained for the increasing and decreasing law of change in the frequency of the probe waves at the half-period of modulation

,

,

where U _s , φ _s , τ _c is the amplitude, phase and delay of the signal for the double propagation time of the radio waves to the probed surface, U _n , φ _n , τ _c is the amplitude, phase and delay for the double propagation time of the radio waves to the noise, ω ₀ , Δω, T is the center frequency, the modulation range, and the modulation period.

From the PSRCH1 and PSRCH2 thus formed, the total and difference signals are calculated, for the SIRS - u _src (t) and for the RFRS - u _src (t).

Then, a measure of the difference in the parameters of the obtained HFRS and RFRS from the reference parameters is determined, and if the measure of the difference in the parameters of one of them from the reference parameters is below the control level, use this HFRS or the RFRS to calculate the distance. And if the measure of the difference between the parameters of the MHD and RFRS from the reference exceeds the control level, then the central frequency of the modulation range is changed. As follows from the expressions for u _ccpch (t) and u _pccr (t), the relations between the terms , and, accordingly, between the terms , , which determine the level of the useful and interfering component in the HFRS and RFHR. When one of the terms becomes equal to zero, the duration of the periods u _cfd (t) or u _pfd (t) becomes constant, and the spectrum becomes symmetrical. Then the distance to the source of the echo waves is determined from the frequency of this signal (the frequency of the signal is the reciprocal of the period). Then, in a similar way, you can determine the distance to the second source of echo waves.

The proposed radio range finder with continuous emission of frequency - modulated radio waves during implementation provides high measurement accuracy. Computer processing of the RF system recorded in bench conditions without interference allowed to reduce the measurement error from 2 to 1.2 mm in the range

measured ranges from 1 to 16 meters with frequency modulation in the range of 500 M Hz. In the presence of an interfering reflector creating an interfering signal with an amplitude of 50% of the useful, the measurement error decreases from 90 to 25 mm.

Information sources

1. Viktorov V.L., Lunkin B.V., Sovlukov A.S. “Radio wave measurements of technological process parameters” M .: Energoizdat. 1989.

2. Vinitsky A.S. "Essay on the fundamentals of radar in the continuous emission of radio waves" M.: Publishing house "Soviet radio", 1961.

3. US patent No. 5546088. 08/13/1996

4. US Patent No. 5504490. 04/02/1996

5. Marple ml. S.L. “Digital spectral analysis and its applications” M .: Mir; 1990.

6. Tikhonov V. I. Statistical radio engineering. M., publishing house "Soviet Radio", 1966.

7. RF patent No. 2152408, G 01 S 13/14 06/30/1999.

8. Gonorovsky I. S. Radio engineering circuits and signals: Textbook for universities. - 4th ed., Revised. and add. - M., Radio and Communications, 1986.

Claims (2)

1. A radio range finder with continuous emission of frequency-modulated radio waves, comprising an antenna, a microwave transmitting and receiving module with a controlled probing signal source (UISS), first and second directional couplers (BUTs) and a mixer (SM), an analogue preliminary processing circuit (SPAO) with an amplifier a differential frequency signal and a frequency meter, characterized in that a frequency synthesizer (MF) with two inputs and two outputs is additionally introduced, and including a frequency meter, a digital processing circuit signals (SCOS) with two inputs and two outputs, and a controlled source of the probing signal (UIZS) is made with one input and two outputs, while the first UISS output is connected to the antenna input through the first and second BUT, the second UISS output is connected to the first input MF, and the input is connected to the first MF output, the second outputs of the first and second BUT are connected, respectively, to the first and second SM inputs, and the SM output is connected to the input of the SPAO, the output of the SPAO is connected to the first input of the MSC, the second input of the MSC is connected to the second output Midrange, and the first output It is connected with the second input of the midrange, while the second output of the center is the output of the device. 2. The radio range finder according to claim 1, characterized in that the DSP comprises a synchronization pulse generator, an analog-to-digital converter and a digital processor, including a memory device and an arithmetic device forming a frequency meter.