RU2158937C2 - Method and device to measure range - Google Patents

Abstract

FIELD: radio engineering, radiolocation, radio navigation, radio measurement, acoustics and optics. SUBSTANCE: method measuring range by measurement of difference of phases of emitted and received periodic signals lies in setting of specified phase difference φ₀ of emitted and received signals by change of frequency of emitted signal, in measurement of set value of frequency of generator, in multiple change of specified phase difference for certain values Δφ_i, in measurement of specified values f_i of frequency of generator and in computation of total phase difference ф_i per each value of frequency f_i ( phase and frequency characteristic ) by formula ф_i= 2πn+φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{0}}$ , where n is value

rounded off to integral number and φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{i}}$ is main value of specified phase difference preset per i-th measurement. Linear component

Description

 The proposed group of inventions relates to radio engineering, namely to the areas of radar, radio navigation, and can be used in the technique of radio measurements, acoustics and optics.

 There are three main methods for measuring distance, which use the measurement of the delay time of a periodic signal propagating in a particular medium. The pulse method determines the distance by directly measuring the time between the transmission of a short pulse and its reception. The frequency method uses a continuous frequency-modulated signal, for example, according to the linear law, and the delay time is determined by the instantaneous difference in the frequencies of the transmitted and received signals.

где l - измеряемое расстояние,
V - скорость сигнала в среде,
ω - круговая частота сигнала.The phase method (see I. E. Kinkulkin et al. "Phase method for determining coordinates", M., "Soviet Radio" 1979) determines the distance traveled by a signal through measuring the phase difference φ of the transmitted and received signals:

where l is the measured distance
V is the signal speed in the medium,
ω is the circular frequency of the signal.

It is generally recognized that the greatest accuracy in distance measurement is provided by the phase method, which, however, is rarely used, due to its main disadvantages:
a) All known phase difference meters are based on the use of a phase detector (PD) having a periodic dependence of the output voltage on the phase difference of the signals at the inputs, for example:
U _fd = U _offd • cosφ, (1)
where U _fd - output voltage FD,
U _off - the maximum voltage of the PD,
φ is the phase difference of the signals at the inputs of the PD.

It follows from (1) that the total phase difference is defined as
φ = φ ¹ + 2πn (2)
where φ ¹ = arccos (U _fd / U _off ) for 0 <φ ¹ <2π; n = 0, 1, 2, .... is an integer.

(3)
где l_max - максимальное измеряемое расстояние,
V - скорость распространения колебания в среде,
ω - круговая частота сигнала.Strictly speaking, the arccos function (U _fd / U _off ) has two values in the interval 0 <φ <2π, but this uncertainty is easily removed if we take into account the sign of the derivative dU _fd / dt, for example, using a quadrature phase detector. Thus, to uniquely determine the distance, it is necessary to fulfill the condition:

(3)
where l _max is the maximum measured distance,
V is the propagation velocity of the oscillations in the medium,
ω is the circular frequency of the signal.

 The fulfillment of condition (3) by reducing the frequency leads to a decrease in the measurement accuracy. In most real-world tasks, the values of the unknown "n" can be hundreds or thousands. Determining the value of n has become the main problem of the phase method.

является достаточно сложной задачей, не имеющей стандартных технических решений.b) Accurate measurement of the phase difference of the oscillations in the interval

is a rather difficult task that does not have standard technical solutions.

 c) The phase method is considered to be "single-object", i.e. allowing to conduct location of only one object. The component of the received signal caused by reflection from another object is superimposed on the useful signal, changes its phase, thereby distorting the measurement result, and is not distinguished by obvious methods.

 For the above reasons, the phase method of measuring distance is rarely used, either in complex multi-frequency radio navigation systems, or in combination with other methods.

An example of such a combination and an analogue of the present invention is US patent 4503433 "Measurement of the target range in a radar with a frequency-modulated continuous signal", G 01 S 13/34, 13/26, publ. 1985 In this invention, a coarse distance measurement is made by the frequency method using linear frequency modulation of the generator signal. The exact value of the distance is determined by the phase method according to formula (2), and the value of the parameter n was calculated from the result of a rough measurement. This device allows to increase the measurement accuracy with respect to devices using the classical frequency method, but does not realize the potential capabilities of the phase method, having the following disadvantages:
- determination of the exact value of n requires high linearity of the chirp signal, accurate determination of frequency deviation and short periods of time,
- high accuracy of measuring the main value of the initial phase difference in this device cannot be implemented.

 A common drawback of such combined devices is the presence in one device of technical means of two or more methods, which complicates it and increases the cost.

 The closest analogue of the present invention is the "Method and system for measuring small distances" (see US patent 4829305, G 01 S 13/08, publ. 1989 g). The proposed method consists in the fact that the frequency of the emitted signal is adjusted until the specified phase difference of the received and emitted signals is achieved. The problem of measurement ambiguity is removed by using only the main value of the phase difference, i.e. n = 0. To improve the measurement accuracy, it is proposed to set the phase difference by comparing the received signal with the harmonic of the emitted signal. The distance is calculated from the value determined by the generator frequency meter according to the formula (3). A block diagram of a device for implementing the method is shown in FIG. 1. The device contains a generator 1 with a frequency controlled by voltage, the subharmonic signal of which from the output of the frequency divider 2 is transmitted by the emitter 3 to the side of the measured object and in the rough measurement mode is fed to the reference input of the phase comparison means 5 (phase detector), to the second input of which the signal reflected from the object through the receiver 4. The output voltage of the phase detector, being a criterion when setting a certain value of the phase difference of the transmitted and received signals, passes through the filter 6 to the input control the frequency of the generator 1. The system is a ring for automatically adjusting the frequency (AFC) of the generator to the discriminator frequency, which is determined by the propagation time of the signal to the object and back. To increase the accuracy, a mode is provided in which the harmonic of the transmitted signal is fed to the reference input of the phase detector, i.e. generator signal 1. The value of the steady-state frequency is determined by the frequency meter 7, and the computing means 8 connected to it calculates the distance and displays the result on the display 9. The main disadvantage of the method and system is the ambiguity of the measurement result, i.e. the inability to determine the parameter n, which predetermines its use only at small distances, that is, at n = 0. The system is not able to separate the useful reflected signal from spurious reflections, which limits the accuracy of measuring the distance.

 This proposal is aimed at solving the problem of realizing the potentially high accuracy of the phase method of measuring distance while simplifying and, therefore, reducing the cost of technical means of measurement, as well as achieving the possibility of simultaneously determining the distance to two or more objects.

, a φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{i}}$ - главное значение установленной для i-го измерения заданной разности фаз, выделяют из фазочастотной характеристики линейную составляющую

из крутизны которой определяют расстояние (l), пройденное энергетически большей частью сигнала по основной траектории, и периодические составляющие, из параметров которых вычисляют разности расстояний, пройденные сигналом по основной и другим траекториям, причем для определения абсолютных координат объекта или объектов на пути излучаемого сигнала устанавливают репер (например, отражатель), абсолютные координаты которого известны, принимают возвращенный им сигнал и вычисляют по фазочастотной характеристике расстояния между объектами и репером, а устройство для осуществления способа измерения расстояния, содержащее генератор с частотой, управляемой напряжением, подключенный к выходу устройства, средство сравнения фаз (фазовый детектор), первый вход которого подключен к выходу генератора, а второй - к входу устройства, измеритель частоты, подключенный к выходу генератора и вычислительное средство, подключенное к измерителю частоты и определяющее расстояние, дополнительно содержит многофункциональное программируемое управляющее средство (контроллер), с которым соединены шиной приема и передачи информации измеритель частоты и вычислительное средство; аналоговый вход контроллера соединен с выходом фазового детектора, а аналоговый выход - с входом управления частотой генератора, причем контроллер и вычислительное средство наделены программой, обеспечивающей реализацию алгоритма измерения фазочастотной характеристики и вычисления расстояний с использованием, например, операций подключения и отключения входа генератора к выходу фазового детектора, изменения начальной частоты генератора, изменения знака коэффициента передачи сигнала с выхода фазового детектора на вход генератора, а также изменения величины сдвига фазы фазовращателя, включенного либо между выходом генератора и фазовым детектором, либо между входом устройства и фазовым детектором, а дополнительно устройство может содержать линию задержки, включенную между генератором и фазовым детектором, а также включенные в передающий канал между управляемым генератором и выходом устройства и в приемный канал между входом устройства и фазовым детектором соединенные с командными выходами контроллера ключевые устройства.The problem is solved in that according to the invention in a method of measuring the distance by measuring the phase difference of the emitted with a frequency f and the received periodic signals, consisting in the fact that by changing the frequency of the emitted signal f set a given phase difference φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{0}}$ emitted and received signals, measure the set value of the generator frequency f ₀ calculate the distance from the measured frequency value and the set phase difference, measure the dependence of the total phase difference of the emitted and received signals on the frequency, for which the set phase difference is changed repeatedly to certain values Δφ _i , steady-state measurements generator frequency values f _i , calculate the total phase difference for each value of f _i (phase-frequency characteristic) according to the formula φ _i = 2πn + φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{i}}$ where n is a value rounded to an integer

, a φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{i}}$ - the main value of the specified phase difference set for the i-th measurement, isolate the linear component from the phase-frequency characteristic

from the steepness of which the distance (l) is determined, which is traveled energetically by most of the signal along the main path, and the periodic components, from the parameters of which the difference in distances traveled by the signal along the main and other paths is calculated, and to determine the absolute coordinates of the object or objects on the path of the emitted signal a reference point (for example, a reflector), the absolute coordinates of which are known, receive the signal returned by it and calculate by the phase-frequency characteristic of the distance between objects and a benchmark, and a device for implementing a distance measuring method, comprising a generator with a frequency controlled by voltage connected to the output of the device, phase comparison means (phase detector), the first input of which is connected to the output of the generator, and the second to the input of the device, a frequency meter, connected to the output of the generator and computing means connected to the frequency meter and determining the distance, further comprises a multifunctional programmable control means (controller), which is connected inens with a bus for receiving and transmitting information, a frequency meter and computing means; the analogue input of the controller is connected to the output of the phase detector, and the analogue output is connected to the input of the frequency control of the generator, and the controller and computing means are endowed with a program that implements an algorithm for measuring the phase-frequency characteristic and calculating distances using, for example, the operations of connecting and disconnecting the input of the generator to the phase output detector, changes in the initial frequency of the generator, changes in the sign of the transmission coefficient of the signal from the output of the phase detector to the input of the generator, also changes in the phase shift of the phase shifter included either between the output of the generator and the phase detector, or between the input of the device and the phase detector, and the device may further comprise a delay line connected between the generator and the phase detector, as well as included in the transmitting channel between the controlled generator and the output devices and into the receiving channel between the input of the device and the phase detector key devices connected to the command outputs of the controller.

 Five figures of drawings and two text materials are attached to the present description.

 In FIG. 1 shows a structural diagram of a prototype device.

 In FIG. 2 shows a structural diagram of the proposed device.

 In FIG. 3 shows a structural diagram of a level meter of oil products in a tank, built on the principles of the invention.

 In FIG. 4 shows the characteristics of a multi-frequency discriminator, illustrating one of the algorithms for measuring the phase-frequency characteristic.

 In FIG. 5 shows timing diagrams illustrating the operation of the proposed device in continuous and quasi-continuous mode.

 Appendix 1, "Phase-frequency method for measuring distance," shows the derivation of the main theoretical relationships justifying the proposed method.

 Appendix 2 shows the algorithm of the main subroutine of the device controller for measuring distance.

Как показано в "Приложении 1" к настоящему описанию, полученные данные позволяют вычислить ФЧХ по формуле: φ_i= 2πn+φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{i}}$ , где n - округленное до целого числа значение

а φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{i}}$ - главное значение установленной для i-го измерения заданной разности фаз φ_i. Из полученной фазочастотной характеристики выделяют линейную составляющую

из крутизны которой определяют расстояние l, пройденное энергетически большей частью сигнала, и периодические составляющие, позволяющие вычислить расстояния, пройденные сигналом по другим траекториям.In contrast to the prototype method, which determines the distance from one value of the phase difference of the emitted and received signals at one of the frequencies, the basis of the present invention is the accurate measurement of a complete phase-frequency characteristic (PFC) of an object in a certain frequency range, the slope of the linear component of which is equal to the signal delay time and therefore, it uniquely determines the distance from the device to the main object, i.e., the length of the path that the energetically large part of the signal has passed. The periodic component of the phase-frequency characteristic carries information on the length of other trajectories, in particular, on the differences in the distance to the main object and the distances to other objects that are in the coverage area of the device. To obtain the phase response in the proposed method after measuring the frequency f ₀ , established upon reaching a predetermined value of the phase difference of the emitted and received signals φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{0}}$ , the value of f _{0 is} stored and, unlike the prototype, a new value of the phase difference φ ₁ = φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{0}}$ + Δφ ₁ .. The frequency f, corresponding to the new value of the phase difference, is also remembered. Repeating this procedure repeatedly in a given frequency range, a series of frequencies f _i corresponding to a consecutive series of phase difference is measured

As shown in "Appendix 1" to the present description, the obtained data allow us to calculate the phase response according to the formula: φ _i = 2πn + φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{i}}$ where n is a value rounded to an integer

and φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{i}}$ - the main value set for the i-th measurement of the given phase difference φ _i . From the obtained phase-frequency characteristic, a linear component is isolated

the slope of which determines the distance l traveled energetically by the most part of the signal, and the periodic components that allow you to calculate the distance traveled by the signal along other paths.

 The block diagram of the device for implementing the proposed method is shown in FIG. 2. Like the closest prototype, the device contains a generator 1 with a frequency controlled by voltage (VCO), which transmits a signal through an emitter 3 to an object, and a phase detector 2, to the reference input of which a signal from generator 1 is supplied, and to a second input, a signal from an object through the receiver 4. The output signal of the phase detector (PD) is used to adjust the frequency of the generator 1, the frequency meter 7 determines the steady-state frequency of the generator 1 and transmits this information to the computing tool 8, which determines the distance and displays this information is on display 9. In contrast to the prototype, the proposed device contains a multifunctional programmable control tool (controller) 10, which is connected by digital information exchange buses with a frequency meter 7 and computing tool 8. The input of the analog signal of controller 10 is connected to the output of PD 5, and the output - to the VCO frequency control input 1. The controller design provides for the availability of technical means for implementing the algorithm for measuring the phase response, for example, the possibilities in accordance with the plug-in program of switching and disconnecting the input of the generator 1 from the phase detector 2, setting the desired frequency of the VCO 1 by changing the voltage at its input, reversing (inverting) the sign of the transfer coefficient of the output signal PD 5 to the input of the VCO 1. The controller and computing tool are endowed with programs that provide implementation phase response algorithms and distance calculation.

To measure a number of frequencies f _i , the properties of a multi-frequency discriminator are used, which is a combination of a phase detector and a delay line (see Kaplanov MR, Levin VA, "Automatic frequency control", Moscow, Gosenergoizdat, 1962). The characteristic of such a discriminator has the form of a cosine wave, as a result of which the AFC system using it has many stability frequencies, the frequency interval between which corresponds to the phase difference of the signals at the inputs of the PD 2π and in the proposed device is Δf _i = f _i -f _(1-2) = V / l. The technical means used in the invention provide opportunities for many variants of the algorithm for measuring the series f _i .

- главное значение начальной разности фаз, соответствующей нулевому напряжению на выходе ФД, а α - поправка на погрешности измерения (асимметрия ФД, статическая ошибка АПЧ и т.п.), алгоритмы вычисления которой приведены в "Приложении 1".For example, the AFC is turned off, the frequency characteristic of the discriminator is determined, for which the voltage at the VCO input is varied discretely, while measuring the VCO frequency and the output voltage of the PD, the approximate frequencies f _i corresponding to the points of the zero output voltage of the PD and the negative derivative dU _fd / df are determined and stored (odd values i), set providing resistance AFC at these points mark ratio transmission feedback circuit is set close to the VCO frequency f _i, include AFC, is measured and stored exact value of f _1, AFC disable is set near the frequency f VCO ₃ include AFT is measured and the stored current value of the frequency f ₃ and t. d. This process is repeatedly reproduced for all odd values of i in a predetermined frequency range. To improve the accuracy of distance measurement, the process is repeated and a plurality of frequencies f _i are measured for odd values of i, setting the opposite sign of the transfer coefficient of the feedback circuit. From a number of values of f _i calculate the phase-frequency characteristic according to the formula φ _i = 2πn + φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{0}}$ + α, where n is the ratio rounded to an integer

is the main value of the initial phase difference corresponding to the zero voltage at the output of the PD, and α is the correction for measurement errors (PD asymmetry, AFC static error, etc.), the calculation algorithms of which are given in "Appendix 1".

The total phase response is the sum of three components: linear φ ^(lin) = 2πfl / V determined energetically by most of the received signal, periodic φ ^(~) , which carries information about the distance traveled by parts of the signal along other paths, and aperiodic φ ^(an) , due to the presence of other factors, including measurement errors of the phase response. An analysis in order to isolate the linear and periodic components of interest, as well as to determine the spectrum of the periodic component in order to determine the length of the secondary trajectories, is a mathematical task, for the solution of which a wide range of methods can be applied from simple averaging to correlation analysis and solving systems of transcendental equations.

 The starting point of the measured distance is usually a device for measuring distance, which is not always acceptable, since this reference point is not geometrically attached to the absolute coordinates. The proposed method and device solve this problem by installing a benchmark whose absolute coordinates are known. The benchmark reflects or returns part of the emitted signal to the input of the device, providing the ability to determine the distance between the objects and the benchmark, thereby setting the absolute coordinates of the objects. As shown in "Appendix 1", the obtained relations are valid if there is a main signal path along which the predominant part of the received signal power passes. If in the real case such a trajectory is absent, it can be created artificially by setting a benchmark.

The structure of the device between the output of the generator and the reference input of the phase detector or between the input of the device and the signal input of the PD can include a controlled phase shifter 11, the control input of which is connected to the controller. The use of a phase shifter expands the capabilities of the device, in particular:
1. allows you to reduce the discrete changes in phase and frequency and thereby increase the accuracy of the phase response measurement,
2. allows you to implement the algorithm for measuring the phase response, which does not require turning off the AFC when changing the set phase difference,
3. allows you to implement the simplest version of the device using two frequencies and a minimum measurement duration.

 The inclusion of a delay line 14 between the generator and the reference input of the phase detector, the delay time of which is equal to the time it takes for the signal to pass from the generator to a close source of spurious reflection and back to the phase detector, can significantly reduce the measurement error due to this reflection, but increases the frequency discretion by “approximating” object to device.

 Introduction to the device for measuring the distance of the key elements 12 and 13 controlled by the controller between the generator and the output of the device, as well as between the input of the device and the phase detector, can improve the measurement accuracy by eliminating the reception of reflections from interfering objects.

 An example of one of the many possible implementations of the invention is a radar level meter of oil products in the tank. A block diagram of this device is shown in FIG. 3.

The output of the generator (VCO) ultra-high frequency 1 is connected to a directional coupler 15, dividing the signal of the generator 1 into three channels. A key element 12 and a ferrite circulator 17 connected to the antenna 18 are connected in series with the main output of the coupler 15. The antenna 18 is installed in the neck 19 of the tank 21. A delay line 14, a controlled phase shifter 11 and a reference input of the phase detector 5 are connected in series to the second output of the directional coupler 15. (FD). A frequency meter 7 is connected to the third output of the coupler 15. A key element 13, an amplifier 16 with an automatic gain control (AGC) system and a signal input of the phase detector 5 are connected in series to the third arm of the circulator. The inputs of the controller 10, which includes computing means 8, are connected with the output of the phase detector 5 and the output of the frequency meter 7. The outputs of the control commands of the controller 10 are connected to key elements 12 and 13, the phase shifter 11, the frequency control circuit 23 and the frequency control input generator 1. The measuring results are output from the output 24 of the controller 10 and displayed on the display 9. In the reservoir between the antenna 18 and the measuring surface of the product 22 is mounted fiducial reflector 20 at a distance H _p from the tank bottom.

 The generator 1, the directional coupler 15, the key element 12, the ferrite circulator 17, the antenna 18, the reference reflector 20 and the surface of the product 22 form a path of the emitted signal.

 The surface of the product 22, antenna 18, circulator 17, key element 13, amplifier 16 and phase detector 5 form a reflected signal path.

 The generator 1, the directional coupler 15, the delay line 14, the controlled phase shifter 11 and the phase detector 5 form the path of the reference signal.

 A controller 10 with computing means 9 and a frequency control circuit 23 together with a controlled generator 1, a phase shifter 11 and key elements 12 and 13 comprise a complex of information management and processing.

As a generator, a transistor oscillator or a generator on a Gunn diode can be used, the frequency of the generator is controlled by changing the voltage on the varactor diode. Phase detector 5 (see A.A. Shakhgildyan, V.V. Lyakhovkin "Phase-frequency locked loop" Ed. Svyaz, 1966) is a microwave range mixer with a zero intermediate frequency. As a frequency meter 7, a combination of digital frequency dividers and a pulse counter can be applied. The delay line 14 is a segment of the microwave transmission line (coaxial cable, strip line, etc.), the delay time of which is equal to the transit time of the signal reflected from the antenna, from the coupler 15 to the signal input of the phase detector 5 along the path: key 12, circulator 17, antenna 18, circulator 17, key 13, amplifier 16. The controlled phase shifter 11 is a microwave circuit of two switches and a phase-shifting circuit included in the path at a given position of the switches. The phase shifter has two states - Δφ $\genfrac{}{}{0ex}{}{\text{0}}{\text{fv}}$ = 0 with the controller command "m = 0" and Δφ $\genfrac{}{}{0ex}{}{\text{l}}{\text{fv}}$ ≈ π / 2 with the command "m = 1". Key elements 12 and 13 can be made on GaAs PIN diodes and should have a short switching time (on the order of a few nanoseconds). The amplifier 16 may be equipped with an AGC circuit to compensate for changes in the power of the received signal. The frequency control circuit 23 performs the functions of amplification and integration of the AFC error signal, filtering the components of the carrier frequency and pulse modulation, as well as (on the controller's instructions) turning the AFC on and off, and reversing the sign of the transmission coefficient. The controller command "l = 0" sets the sign of the transfer coefficient "minus", and the command "l = 1" sets the plus sign. The controller 10, based on the microprocessor, performs the functions of both controlling the measurement process and calculating the phase-frequency characteristic and distances, for which it is endowed with appropriate programs.

(см. фиг. 4а), где L - расстояние между устройством и поверхностью продукта, причем частотный интервал между соседними переходными частотами с одинаковым знаком производной dU_фд/df однозначно определяется расстоянием до измеряемого объекта и равен: f_k - f_k-1 = c/2L. Генератор и многочастотный дискриминатор образуют систему АПЧ, устанавливающую частоту генератора на одну из переходных частот. Установившееся значение частоты обозначается f_klm, где k - порядковый номер периода характеристики дискриминатора. По команде контроллера АПЧ может отключаться, а частота генератора 1 управляться контроллером.When the device is operating, the signal of the generator 1 through the coupler 2, the public key 12 and the circulator 17 is fed to the antenna 18 and emitted by it in the direction of the product surface 22. The reflected signal is received by the antenna 18 and through the circulator 17, the public key 13 and the amplifier 16 are fed to the signal input of the phase detector 5. At the second input of the phase detector 5, a reference signal is supplied from the generator 1 through the coupler 15, the delay line 17 and the controlled phase shifter 11. The output signal of the phase detector 5 is fed to the input of the control circuit 23, de enhanced and integrated. The voltage received at the output of the control circuit 23 is supplied to the frequency control input of the generator 1. The phase detector with a delay line, the role of which is the signal path from the coupler 15 to the surface 22 and back to the phase detector 5, is a multi-frequency discriminator, the characteristic of which is of the form

(see Fig. 4a), where L is the distance between the device and the product surface, and the frequency interval between adjacent transition frequencies with the same sign of the derivative dU _fd / df is uniquely determined by the distance to the measured object and is equal to: f _k - f _k-1 = c / 2L. The generator and the multi-frequency discriminator form an AFC system that sets the generator frequency to one of the transition frequencies. The _steady-state frequency value is denoted by f _klm , where k is the sequence number of the discriminator characteristic period. At the command of the controller, the AFC can be turned off, and the frequency of the generator 1 is controlled by the controller.

The device can operate in two modes: continuous (H) and quasi-continuous pulsed (SOI) radiation depending on the distance L _x between the benchmark and the level of the product. At low product levels, H _x , i.e. relatively weak received signal, the SOI mode is used, when the product level increases, the received signal power increases, but L _x decreases. At a certain value of L _{x, the} device switches to mode H. In mode H, the key elements 12 and 13 are constantly in the "open" state. Temporal plots of the SOI mode are shown in FIG. 5. The key 12 conducts pulse modulation of the transmitted signal with a small duty cycle (for example, 3-10), pulse duration t _u and repetition period T _u (Fig. 5 a). The key 13 opens the receiving channel either at the time of arrival of the reflection pulse from the reference 20 (Fig. 5 b), or at the time of arrival of the reflection pulse from the surface of the product 22 (Fig. 5 c). At the output of the phase detector in the SOI mode, there is a pulsed video signal whose amplitude is determined by the phase difference of the signals at its inputs. If the frequency of pulse modulation is much higher than the cut-off frequency of the low-pass filter at the output of the phase detector, then the pulse component is suppressed by the filter and the output signal of the phase detector becomes continuous, as in mode H.

The measurement program has the following main routines:
1) Preparation for work.

 2) Working stroke.

 3) Calculation of the phase response.

4) Analysis of the phase response, calculation of the level of H _x .

The purpose of the "Preparing for work" subroutine is to check the operability of the units and systems of the device by the controller, measure the characteristics of the multi-frequency discriminator and approximately determine the level of the product, and select the type of emitted signal (mode H or SOI). Having received confirmation of the operability of the nodes and systems of the device and disabling the AFC, the subroutine measures the characteristics of the multi-frequency discriminator, performing:
- setting the frequency of the generator 1 to the lower limit of the operating frequency range, simultaneous measurement of the frequency and output voltage of the phase detector, storing these values,
- increasing the frequency of the generator by changing the decreasing voltage by Δf ≪ f _k -f _k-1 , repeated simultaneous measurement of the frequency and output voltage of the phase detector, storing them,
- repeated playback of this operation until the upper limit of the working frequency range is reached.

Сравнивая L^≈ с заданным значением L₀, подпрограмма осуществляет выбор вида излучаемого сигнала: квазинепрерывный импульсный (КНИ), если L^≈ > L₀ и непрерывный (H), если L^≈ < L₀. Затем подпрограмма, установив минимальную в рабочем диапазоне частоту перехода f₀₀₀ или f₀₁₀ и знак коэффициента передачи схемы управления, обеспечивающий устойчивость АПЧ в этой точке, подключает выход схемы управления 23 к входу генератора 1 (включение АПЧ). В результате выполнения этой операции выходной сигнал фазового детектора 5, усиленный схемой управления частотой 23, начинает поступать на вход управления частотой генератора 1, обеспечивая тем самым функционирование схемы частотной автоподстройки частоты с многочастотным дискриминатором. АПЧ устанавливает частоту генератора f₀₀₀ либо f₀₁₀, выводя устройство на исходную позицию подпрограммы "Рабочий ход".The subprogram selects from the obtained data two series of approximate values of the transition frequencies f _kl satisfying the condition U ≈ 0 for the negative (f _k0 ) and positive (f _k1 ) steepness dU _fd / df, and determines the approximate value of the distance to the product surface using the formula:

Comparing L ^≈ with a given value of L ₀ , the subprogram selects the type of emitted signal: quasi-continuous pulsed (SOI), if L ^≈ > L ₀ and continuous (H), if L ^≈ <L ₀ . Then, the subroutine, setting the transition frequency f ₀₀₀ or f ₀₁₀ minimum in the operating range and the sign of the transfer coefficient of the control circuit ensuring stability of the AFC at this point, connects the output of the control circuit 23 to the input of generator 1 (switching on the AFC). As a result of this operation, the output signal of the phase detector 5, amplified by the frequency control circuit 23, begins to be fed to the frequency control input of the generator 1, thereby ensuring the functioning of the frequency-locked loop with a multi-frequency discriminator. AFC sets the frequency of the generator f ₀₀₀ or f ₀₁₀ , bringing the device to the starting position of the subprogram "Travel".

The “Travel” subroutine provides a measurement of a number of frequencies f _klm corresponding to a number of phase differences of the received and transmitted signals φ = 2πk + lπ + m π / 2 + π / 2 for a given frequency range f _min -f _max . The subroutine algorithm is independent of the type of radiation (H or SOI). In FIG. 4 shows changes in the characteristics of the multi-frequency discriminator during the measurement process. Before starting the measurement at m = 0, the frequency of the generator 1 is set by the controller in the region of the minimum transition frequency in the operating range, while the command l = 0 (or l = 1) is provided, which ensures the stability of the AFC at this point, and the AFC is turned on (Fig. 4a) . After the transition process, the frequency meter 7 determines the exact value of the frequency f ₀₀₀ (or f ₀₁₀ ) and stores it in the controller memory. Next, the controller with the command m = 1 shifts the phase detector characteristic by π / 2, which leads to the disruption of the AFC equilibrium, the appearance of an error signal, and the restoration of equilibrium at a frequency f ₀₀₁ , which is measured and stored (Fig. 4b). Next, the frequency f ₀₁₀ is measured at l = 1, m = 0 (Fig. 4c) and the frequency f ₀₁₁ at l = 1, m = 1 (Fig. 4d). It is significant that any of the phase increments performed does not remove the AFC outside the zone of local stability. In the next cycle, which begins by measuring the frequency f ₁₀₀ at l = 0, m = 0, all operations are repeated. Measurements are taken while the condition: f _klm <f _max . The algorithm of the subroutine "stroke" is given in "Appendix 2".

(6)
где: n - целое число, получаемое округлением n^*, определяемой как

(7)
Значения величин α_klm,Δφ $\genfrac{}{}{0ex}{}{\text{1}}{\text{фв}}$ извлекаются из памяти контроллера, куда они заносятся при процессе калибровки. Измерение их проводится в режиме линейной ФЧХ (например, в режиме КНИ при работе с репером) по следующим формулам:

(8)

(9)

(10)
В режиме КНИ подпрограммы "Рабочий ход" и "Вычисление ФЧХ" выполняются: дважды для измерения расстояния до репера и до поверхности продукта. Подпрограмма "Анализ ФЧХ-КНИ" имеет один программный модуль, применимый и в режиме H, "Линеаризация ФЧХ", т.е. аппроксимация ее выражением вида:
φ^(лин) = 2πfτ.
Определение τ проводится, например, решением уравнения:

(11)
где Δf $\genfrac{}{}{0ex}{}{\text{(-)}}{\text{klm}}$ и Δf $\genfrac{}{}{0ex}{}{\text{(+)}}{\text{klm}}$ - значения дискрета изменения частоты на один шаг рабочего хода ниже и выше частоты f_klm.The subroutine "Calculation of the phase response" sets the exact values of the phase difference corresponding to the measured frequencies, determining the value of n, introducing a correction for the asymmetry of the phase detector and using the exact value of the phase shift phase shifter 11. The calculation is carried out according to the formula:

(6)
where: n is the integer obtained by rounding n ^* , defined as

(7)
Values of α _klm , Δφ $\genfrac{}{}{0ex}{}{\text{1}}{\text{fv}}$ retrieved from the controller memory, where they are entered during the calibration process. Their measurement is carried out in the linear phase response mode (for example, in the SOI mode when working with a benchmark) according to the following formulas:

(eight)

(9)

(10)
In the SOI mode, the subroutines "Stroke" and "Calculation of the phase response" are performed: twice to measure the distance to the benchmark and to the surface of the product. The subroutine "Analysis of the phase-phase response-SOI" has one program module, which is also applicable in mode H, "Linearization of the phase-response characteristic", i.e. approximation by its expression of the form:
φ ^(lin) = 2πfτ.
The determination of τ is carried out, for example, by solving the equation:

(eleven)
where Δf $\genfrac{}{}{0ex}{}{\text{(-)}}{\text{klm}}$ and Δf $\genfrac{}{}{0ex}{}{\text{(+)}}{\text{klm}}$ - the discrete values of the frequency change by one step of the stroke below and above the frequency f _klm .

In the SOI mode, the determination of the τ _{p of the} reference and τ _{n of the} surface uniquely determines the measured value — the distance from the reference to the surface of the product:
L _x = LL _p = c (τ _n -τ _p ).
The “PFC-N Analysis” subroutine performs the “PFC linearization” module, determines τ _n and extracts the periodic component of the PFC as the difference
φ = φ _klm -2πf _klm τ _n (12)
Next, using interpolation, the exact values of the frequencies f _{r are} determined at which the condition for the equality of expression (12) to zero is satisfied and the value r is determined for each of them, as the ratio rounded to the integer:
r ^* = f _r / (f _r - f _(r-1) ).

The distance between the benchmark and the surface of the product is determined by the formula:
L _x = Vr / 4f _r . (thirteen)
The proposed device for measuring distance in addition to the main purpose can be used as
- a meter of the phase-frequency characteristics of the transmission and reflection coefficients of multipoles, and when measuring the phase of the transmission coefficient, the measured object is switched on between the input and output of the device, and when measuring the phase of the reflection coefficient, to the decoupling element (ferrite circulator, directional coupler) connected to the input and output of the device,
- a meter for the non-uniformity of group delay time (GD) of a signal in information transmission systems, and the measured object is switched on between the output and the input of the device.

 If you connect a transmitting antenna to the output of the device, and two or more spatially separated receiving antennas to the input through the switch, the device is able to determine the angular coordinate of the object. For this, the phase response measurement procedure is carried out in turn with each of the receiving channels, connecting the input of the device to the antenna of the working channel. The determination of the angular coordinate is carried out either by the magnitude of the ratio of the measured distance difference to the base (the distance between the antennas), or by direct analysis of the measured phase response. If the switching capabilities in the receiving channel are limited, for example, when operating in the millimeter range of radio waves, then at least one more phase detector connected to the second receiving antenna and VCO is added to the device. In this case, the channels are switched by connecting the VCO control input to the output of the working channel PD.

 The materials of this application indicate that the present invention in terms of a set of features and technical effect can open a new direction in long-range measurement (we will call it conventionally as the phase-frequency method), which can compete with the main direction of this technical field: continuous FM radar (frequency method). It is therefore of interest to compare the capabilities of the frequency and phase-frequency methods, their fundamental differences and similarities.

 Common to these methods is the use for determining the measurement distance in the frequency range of the complex reflection coefficient (or transmission) of an object (or space) located between the output and input of the meter. In this case, the real part of this function is measured in the frequency method, and its argument in the phase-frequency method. It follows from this that, in terms of informativeness, for example, the ability to distinguish between extraneous objects, the methods are at least comparable.

 The measurement accuracy of both methods is determined in essence by the accuracy of determining the frequency of the emitted signal at any time in the measurement process. In the frequency method, this certainty is achieved by high requirements for the parameters of linear frequency modulation and their stability. The phase-frequency method provides the ability to directly measure the frequency with almost unlimited accuracy, which determines its undoubted advantage in this quality.

 The resolution of each of these methods is determined by the width of the frequency range used: the deviation of the LFM for the frequency and the frequency range of the generator for the phase-frequency method. The magnitude of the deviation and linearity of the LFM are contradictory parameters, which means that high values of accuracy and resolution are not simultaneously realized. The possibilities of expanding the frequency tuning range for the phase-frequency method are practically unlimited, and expanding the operating frequency range does not lead to a decrease in accuracy, but to its increase.

 The advantage of the phase-frequency method in accuracy and resolution is realized by accurately measuring the set of generator frequencies set by the AFC system, which requires a certain time, and the more, the higher the required accuracy and resolution. This means that the phase-frequency method is inferior in frequency to the frequency one that realizes the receipt of measurement results in real time.

Claims (5)

1. The method of measuring the distance by measuring the phase difference of the emitted and received periodic signals, consisting in the fact that by changing the frequency of the emitted signal set the specified phase difference φ $\genfrac{}{}{0ex}{}{\text{(y)}}{\text{0}}$ of the emitted and received signals, the set value of the generator frequency f _o is measured and the distance is calculated from the measured frequency value and the set phase difference, characterized in that the dependence of the phase difference of the emitted and received signals on the frequency is measured, for which the predetermined difference is changed repeatedly by certain values Δφ _i phases, measure the set values of the frequency of the generator f _i , calculate the phase-frequency characteristic according to the formula

where φ _i [f _i ] is the phase difference value for the measured frequency value f _i ,
determine the linear component from the phase-frequency characteristic

where V is the propagation velocity;
f is the signal frequency,
from the steepness of which the distance l is determined, which is traveled energetically by most of the signal along the main path, as well as the periodic component and its spectrum for calculating the difference of the distances traveled by the signal along the main and other paths.  2. The method of measuring distance according to claim 1, characterized in that a reference point is set in the path of the emitted signal, a signal returned by it is received, and the coordinates of the object or objects are determined using the known coordinates of the reference point and the distance between the objects and the reference point calculated from the phase-frequency characteristic.  3. A device for measuring distance, containing a generator with a frequency controlled by voltage, connected to the output of the device, phase comparison means, the first input of which is connected to the output of the generator, the second to the input of the device, a frequency meter connected to the output of the generator and computing means connected to a frequency meter and determining a distance, characterized in that it further comprises a programmer connected by a bus for receiving and transmitting digital information with a frequency meter and computing means a removable control tool made in the form of a controller, the input of which is connected to the output of the phase comparison tool, and the output is connected to the generator frequency control input, and the controller is endowed with a program that provides the generator frequency setting corresponding to the stability condition of the automatic generator frequency adjustment using connection and disconnection operations the input of the generator to the output of the means for comparing the phases, changing the frequency of the generator by changing the voltage at its input, changing the sign of the coefficient before chi signal output from the oscillator input phase comparing means.  4. The device for measuring distance according to claim 3, characterized in that between the output of the generator and the means for comparing the phases, or between the input of the device and the means for comparing the phases, a controlled phase shifter is switched on by two or more fixed phase shift values, the control input of which is connected to the controller.  5. A device for measuring the distance according to claim 3 or 4, characterized in that between the controlled generator and the output of the device, as well as between the input of the device and the phase comparison means, key devices connected to the command outputs of the controller are connected, connecting or disconnecting the generator to the command the output of the device, and the input of the device to the phase comparison tool.

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