RU2133476C1 - Method for measuring the law of change of tuning of carrier frequency of frequency-modulated rf pulses - Google Patents

Abstract

FIELD: radio engineering, applicable for measurement and monitoring of radio-frequency radiation parameters, determination of mode of received signals. SUBSTANCE: this object accomplished at realization of the invention provides for measurement of the law of frequency variation in RF pulse at FM carrier frequency in real time (or close to it) at prior uncertainty of parameters of FM pulses in the form of a single number. The object is accomplished by that in the method for measuring the law of change of tuning of FM pulse carrier frequency at pulse beginning and end, calculating mean value of carrier frequency as arithmetic mean of the values of carrier frequency at pulse beginning and end, the value of carrier frequency in the middle of RF pulse length is measured and compared with the mean value of carrier frequency calculated before; it the compared values are equal, we have a linear law of frequency variation, if they are unequal - a non-linear one; if the measured value is larger than the calculated one, we have a convex function of frequency variation, if it is smaller - a concave one. EFFECT: enhanced speed of response by two and more times, depending on the type of the law of frequency variation. 3 dwg

Description

 The invention relates to radio engineering and can be used to measure and control the parameters of radio emissions, determine the type of received signals.

 To solve some problems, for example, in radio monitoring, it is necessary to ensure that the information on the law of intrapulse frequency modulation (FM) in the real (or close to it) time scale (i.e., for each received radio pulse) is used for subsequent use of this parameter in the identification and classification of signals.

 The variety of possible laws of change of frequency in a pulse is linear, non-linear with a power-law function of frequency modulation, compound [Ch. Cook, M. Bernfeld. Radar signals. Theory and application. Per. from English Ed. M. Kelson. M .: Sov. Radio, 1971. - p. 347], it is possible to consider the law as the most important information parameter, providing an increase in the probability of identification of radiation sources and classification of signals together with such parameters as the carrier frequency (initial or average), pulse duration, pulse repetition period, frequency deviation and direction of carrier frequency tuning (from the initial smaller to final larger, or vice versa).

The law of frequency change in the radio pulse can be estimated by measuring the instantaneous values of the carrier frequency f _i at discrete time instants t _i , i = 1, 2, 3, ..., n. Such measurements are provided, for example, by acousto-optical meters of signal parameters [see, for example, V.N. Kochemasov, E.V. Dolbnya, N.V. Sable. Acoustoelectronic Fourier - processors. - M.: Radio and Communications, 1987. - p. 133; A.S. USSR N 1124431 H 03 J 7/32 Multichannel panoramic receiver. - Official Bulletin. "Discoveries. Inventions", N 42, 1984; V.N. Kochemasov. The use of dispersive Fourier processors in reconnaissance receivers. - Foreign Radio Electronics, N 2, 1987. - pp. 66-73]. Instead of measuring directly instantaneous samples of frequency f _i , for example, the values of amplitude A _i , the signal from the output of the frequency detector, functionally dependent on the frequency can be measured.

 Measurements of instantaneous samples of frequency or amplitude can be carried out either manually or automatically. In radio monitoring, measurements and the input of measured values into a computer must be carried out automatically in real time.

After obtaining an array of f _i values, it is necessary to construct a functional dependence f (t) of the law of the frequency change in the pulse according to the discrete values of f _i using any interpolation method, for example, parabolic [see, for example, Bronstein I.N., Semendyaev K.A. . Math reference. - M .: Nauka, 1967 .-- p. 574]. Thus, to obtain an estimate of the law of frequency change in a pulse, additional operations (addition, division, etc.) with the results of measuring instantaneous frequency samples are required.

Carrying out such operations in real time with samples of the carrier frequency f _i coming from the output of the meter with a high repetition rate and in a large volume, and then storing the functions f (t) in memory in order to use it for signal classification and identification of radiation sources, is difficult even for high-performance computers, as It requires high-speed information input devices, large amounts of RAM and permanent memory, high speed information processing.

 To ensure the required speed of law assessment and reduce the amount of information about the law of frequency change in an impulse, it is necessary to have an law estimate in the form of one or more numbers.

 Obtaining a law estimate in the form of a single number provides methods for measuring the nonlinear distortions of the law of changing the frequency of an FM signal [Pavlenko Yu.F., Spanion P. A. Measurement of parameters of frequency-modulated oscillations. - M .: Radio and communications, 1986.-p.118], for example, methods for measuring differential slope [ibid, p. 145], in which the measure of non-linearity is the maximum deviation of the differential characteristic from the horizontal. To measure the nonlinearity of the FM signal, the voltage is additionally modulated by the voltage of the “nozzle”. Then, the signal under investigation is fed to the FM signal receiver, the frequency of the “tip” signal is extracted using a frequency detector of frequencies, and through an amplitude detector and a low-pass filter, they are fed to an oscillographic indicator, on the screen of which the differential slope is measured, the magnitude of which is used to determine the law of frequency tuning, as the value of the deviation from the linear law.

 A sign of an analogue that coincides with the sign of the claimed technical solution is the measurement of the law of tuning the frequency of the radio pulse in the form of one number - the deviation of the studied law of the change in the carrier frequency from linear.

 The disadvantage of this method is the inability to measure the law in real time for signals with a priori unknown parameters.

 The reasons hindering the achievement of the desired result are the need for additional modulation of the FM signal, tuning of frequency-selective devices to harmonics of the modulating frequency, i.e. a priori knowledge of the parameters of the signal under study and visual acquisition of measurement information, which makes it impossible to use this measurement method in real time (for each radio pulse).

где Δf_max(+), Δf_max(-) - значения максимального отклонения кривой f = φ(t) от прямой, соединяющей крайние точки этой кривой, положительного и отрицательного, соответственно (т.е. над прямой и под прямой).Closest to the technical nature of the proposed method is a method for assessing the nonlinearity of the frequency tuning of the oscillators of the oscillating frequency (GKCh) [GOST 15166-73. Oscillating frequency generators in the frequency range from 1 MHz to 40 MHz. Types. Main parameters. Technical requirements. Test methods. ]. The method consists in the following: at discrete time instants t _i , i = 1, 2, ..., k, measure the values of the carrier frequency of the signal f _i and plot the frequency f _i versus time t _i . Then build a linear graph of the carrier frequency from its initial f _n (for i = 1) to the final f _to (for i = k) values; find the maximum deviation (difference) Δf _{max of the} measured values of the carrier frequency f _i from the frequency values when it is linearly tuned at points t _i , and determine the nonlinearity of the law of frequency tuning by the formula:

where Δf _{max (+)} , Δf _{max (-)} are the values of the maximum deviation of the curve f = φ (t) from the straight line connecting the extreme points of this curve, positive and negative, respectively (i.e., above the line and under the line).

f _n, f _k - initial and final values of the carrier frequency in MHz.

The disadvantage of this method is the inability to measure in real time, because it is necessary to build a linear graph of the dependence of the frequency tuning from f _n to f _k , find the deviations of the frequency Δf from the linear at each measured point, and then select the maximum frequency deviation Δf _max , which is taken as a measure of non-linearity.

The reasons that impede the achievement of the required technical result are that to measure the maximum value of the frequency deviation from the linear one, after measuring all the values of the frequency f _i , it is necessary to carry out a number of operations: construct a linear graph of the frequency change from f _n to f _k ; compare the values of f _i with the corresponding frequency values on a line graph - calculate the frequency deviation Δ f; select the maximum deviation value. All these operations require time, which makes it impossible to obtain the measurement result in real time.

 The signs of the prototype, coinciding with the features of the proposed technical solution, are as follows: measurement of the carrier frequency at the beginning and at the end of the pulse, calculation of the average value of the carrier frequency as the arithmetic average of the values of the carrier frequency at the beginning and end of the pulse.

 The problem to which the invention is directed is to provide for the measurement of the law of frequency tuning in a pulse in real time (or close to it) with an a priori unknown parameters of FM pulses.

 The technical result achieved by the implementation of the invention allows real-time measurement of the law of change of frequency in a radio pulse at an FM carrier frequency in the form of a single number with a priori unknown parameters of a radio pulse, which makes it possible to increase the speed by two or more times depending on the type of law of change frequency.

 The technical result is achieved by the fact that in the method of measuring the law of carrier frequency tuning in radio pulses with frequency modulation, which consists in measuring the carrier frequency at the beginning and at the end of the pulse, calculating the average value of the carrier frequency as the arithmetic average of the values of the carrier frequency at the beginning and end of the pulse , the value of the carrier frequency in the middle of the pulse is measured and compared with the previously calculated average value of the carrier frequency, and if the compared values are equal, then the law of frequency change eyny if not equal - the non-linear, thus, if the measured value is greater than calculated, the change of frequency function is convex, if less - is concave.

The analysis of the essential features of the prototype and the claimed object revealed the following new significant features for the claimed object:
- measuring the value of the carrier frequency in the middle of the duration of the measured pulse;
- comparison of the measured value with the previously calculated average value of the carrier frequency.

 The theoretical evidence for the presence of a causal relationship of the totality of the claimed essential features with the specified technical result is as follows.

The proposed method for measuring the law of intrapulse FM is based on measuring the mean frequency of the FM signal. In FIG. Figure 1 shows two laws of carrier frequency tuning in an FM radio pulse, curve a) is a linear law, curve b) is non-linear. The frequency varies from the initial value of f _n to the final f _to during the pulse duration τ _and = t _to -t ₀ .
For the linear law of change of frequency in a pulse (LFM), the average (arithmetic mean) value of the carrier frequency in a pulse is
f _cf = 1/2 (f _n + f _k )
Let the frequency measurement be provided at uniform discrete time instants t _i , i = 1, 2, ..., k. Consider the values of the carrier frequency at time t ₀ , t _cf and t _n , i.e. at the beginning, in the middle and at the end of the pulse (see Fig. 1). The measured frequencies are f _n , f _cf1 and f _k (for curve 1) and f _n , f _cf2 and f _k (for curve 2), respectively. We determine the value of f _cf by formula (1) and compare it with the measured values of f _cf1 and f _cf2 . A comparison can be made either by finding the difference between these values, or by finding their ratio.

Для нелинейного закона изменения частоты (кривая 2) f_ср≠f_ср2, причем f_ср2 > f_ср, что характерно для выпуклого закона измерения частоты (для вогнутого закона изменения частоты в импульсе было бы обратное соотношение), т.е.Obviously, for the linear law of frequency change (curve 1)

For the nonlinear law of frequency change (curve 2) f _cp ≠ f _cp2 , and f _cp2 > f _cp , which is characteristic of the convex law of frequency measurement (for the concave law of change of frequency in the pulse, the inverse relation would be), i.e.

Таким образом, сравнение среднего арифметического значения несущей частоты в импульсе со значением несущей частоты, измеренным в момент времени, равным половине длительности радиоимпульса, характеризует отклонение закона изменения частоты от линейного, т.е. обеспечивает измерение закона перестройки частоты в радиоимпульсе.

Thus, a comparison of the arithmetic mean value of the carrier frequency in a pulse with the value of the carrier frequency measured at a time instant equal to half the duration of the radio pulse characterizes the deviation of the law of frequency change from linear, i.e. provides measurement of the law of frequency tuning in a radio pulse.

где A - амплитуда импульса,
ω₀ - начальное значение несущей частоты,
Δω - девиация частоты в импульсе,
k - показатель степени,
τ_и - длительность импульса.Let us show the possibility of measuring the law of carrier frequency tuning in a pulse by the deviation of the carrier frequency in the middle of the pulse from the mean square. The signal with a power-law function of frequency modulation can be written as [Varakin L.E. Theory of complex signals. - M .: Owls. radio, 1970.- p.117]

where A is the amplitude of the pulse,
ω ₀ - the initial value of the carrier frequency,
Δω is the frequency deviation in the pulse,
k is an exponent
τ _and - pulse duration.

Тогда для времени t = τ_и/2, подставляя это значение в выражение (4), получим значение частоты
- для линейного закона частотной модуляции

- для нелинейного закона частотной модуляции

Подставляя значения выражения (4) при t = 0 и t = τ_и (т.е. для начального и конечного значений несущей частоты) в выражение (1), получим среднеквадратическое значение несущей частоты в импульсе

Тогда величина отклонения для линейного закона изменения частоты в соответствии с (2) с учетом (5) и (7) равна

а для нелинейного закона частотной модуляции в соответствии с (3) с учетом (6) и (7) равна

Таким образом, для линейного закона изменения частоты в импульсе величина частотного отклонения равна нулю, а для нелинейного не равна нулю и может служить оценкой закона частотной модуляции.In this case, the law of change of frequency in the pulse is determined by

Then, for time t = τ _and / 2, substituting this value in expression (4), we obtain the frequency value
- for the linear law of frequency modulation

- for the nonlinear law of frequency modulation

Substituting the values of expression (4) at t = 0 and t = τ _and (i.e., for the initial and final values of the carrier frequency) into expression (1), we obtain the rms value of the carrier frequency in the pulse

Then the deviation for the linear law of frequency change in accordance with (2), taking into account (5) and (7), is equal to

and for the nonlinear law of frequency modulation in accordance with (3), taking into account (6) and (7), it is

Thus, for the linear law of change of frequency in a pulse, the magnitude of the frequency deviation is zero, and for a nonlinear one it is not zero and can serve as an estimate of the law of frequency modulation.

According to expression (8), a graph of the dependence of the frequency deviation Δ ₂ on the value of the exponent k presented in FIG. 2. For calculations, the frequency deviation Δω was taken equal to 10 MHz, and k varied from 0 to 4 with a step of 0.1. As can be seen from figure 2, the values of the frequency deviation provide an unambiguous measurement of the law of frequency tuning in the pulse.

 Given that the main characteristic of non-linear distortion meters of the FM law is the resolution [see, for example, Pavlenko Yu.F., Shpanion P. A. Measurement of parameters of frequency-modulated oscillations. - M .: Radio and communication, 1986. - 208 p.], Evaluate the resolution of the proposed method.

The error Δ _{1 of the} determination of f _cf by the formula (1) is equal to the sum of the errors of measurement of the instantaneous carrier frequency f _i
Δ ₁ = 2Δ _f ,
where Δ _f is the measurement error of the instantaneous frequency f _i , Δ _f = 0.5Δf _i , where Δf _i is the resolution of the measurement of the instantaneous carrier frequency f _i .

Необходимо также учесть погрешность из-за неопределенности выбора значения отсчета частоты, соответствующего половине длительности импульса τ_и/2, при четном и нечетном количестве отсчетов частоты f_i. Эта погрешность равна 2Δ_f, т.е.The error in determining f _cf1 or f _cf2 is

It is also necessary to take into account the error due to the uncertainty of the choice of the frequency reference value corresponding to half the pulse duration τ _and / 2, with an even and odd number of samples of the frequency f _i . This error is 2Δ _f , i.e.

Δ ₂ = 3Δ _f .
The error in estimating the law by formula (3) is equal to the sum of the errors Δ ₁ and Δ ₂ :
Δ = Δ ₁ + Δ ₂ = 5Δ _f = 2.5Δf _i ,
which will determine the resolution of the method for evaluating the law of change in the frequency of the pulse.

 The invention is illustrated by drawings, in which Fig. 1 shows various laws of tuning the carrier frequency, Fig. 2 shows a graph of the frequency deviation from the value of the exponent, Fig. 3 shows an example of a device that implements this method of measuring the law of frequency tuning in a pulse with a frequency modulation.

 A method of measuring the law of tuning the carrier frequency of radio pulses with frequency modulation is to measure the carrier frequency at the beginning and at the end of the radio pulse, as well as at the time corresponding to the middle of the duration of the radio pulse, in calculating the average value of the carrier frequency as the difference between the final and initial values of the measured frequencies and comparing calculated average value with measured at time corresponding to the middle of the duration of the radio pulse, and if the compared values are equal, then the law changes The frequency variations are linear, if not equal, then not linear, and if the measured value is greater than the calculated one, then the frequency change function is convex, and if less, then concave.

The possibility of implementing a method of measuring the law of tuning of the carrier frequency of radio pulses with frequency modulation is illustrated by an example of a description of the method as a sequence of the following actions:
1. Measure the value of the carrier frequency of the radio pulse f _i , at discrete time instants t _i = n • Δt, where n = 1, 2, 3 ..., during the duration of the input radio pulse;
2. Remember the first (initial) value f _n reference carrier frequency;
3. Remember the last (final);
4. Remember everything in order of priority values of the samples of the carrier frequency f _i ;
5. The last value f _{k of the} reference carrier frequency is added to the initial value of f _{n of the} reference carrier frequency;
6. The resulting amount (f _k + f _n ) is divided into two;
7. The result of dividing (f _k + f _n ) into two is remembered;
8. Count the number of clock pulses during the duration of the measured radio pulse;
9. Divide this number (see clause 8) into two;
10. Remember it as the address for sampling the value of the carrier frequency of the radio pulse corresponding to the middle of the duration of the radio pulse;
11. In accordance with the received address determine the value of the carrier frequency of the radio pulse;
12. Compare the obtained value of the carrier frequency of the radio pulse (see clause 11) with the previously calculated average value of the carrier frequency of the radio pulse (see clause 7);
13. The result of the comparison has the following meanings: if the compared values are equal, then the law of frequency change is linear, if not equal, then it is non-linear, and if the measured value is greater than the calculated one, then the frequency change function is convex, and if less, then concave.

 In more detail, the implementation of the invention is illustrated by the example of a device that implements the method using the drawings, where in FIG. 1 shows the different laws of tuning the carrier frequency, figure 2 shows a graph of the frequency deviation from the value of the exponent, figure 3 shows an example of a device that implements this method of measuring the law of frequency tuning in a pulse with frequency modulation.

 The device comprises a carrier frequency meter (INC) 1, an amplitude detector (HELL) 2, a clock pulse generator (GTI) 3, a first register 4, a second register 5, an adder 6, a first divider into two 7, a third register 8, a counter 9, a second divider by two 10, the device of random access memory 11, the fourth register 12, the comparison device 13.

 The input of the device is the connected inputs of LF 1 and HELL 2. The output of HELL 2 is connected to the input of the GTI 3, the first output of which is connected to the clock input of the first register 4, and the second to the clock input of the second register 5 and the clock input of the frequency meter 1. Output LF 1 is connected with series-connected first register 4, adder 6, first divider by two 7, third register 8. Output LFM 1 is also connected to the second input of adder 6 through second register 5. The second output of GTI 3 is also connected to series-connected counter 9, the second divider m two 10, memory device 11, a fourth register 12, and the comparison device 13, whose outputs are the outputs of the device. The second output of the GTI 3 is also connected to the clock input of the third register 8 and to the clock input of the fourth register 12. The output of the IFI 1 is also connected to the information input of the RAM device 11. The output of the third register 8 is connected to the second input of the code comparison device 13.

The device operates as follows. Measured pulsed radio signals with an FM carrier frequency are fed to the input of the device. INCH 1 provides a measurement of the values of the carrier frequency of the radio pulse f _i at discrete time instants t _i , i = 1, 2, ... n, specified by the GTI 3 during the duration of the input radio pulse of the pulse, comes from HELL 2. From the output of INCH 1, codes of discrete samples frequencies f _i are supplied to the input of the first register 4, in which the first (initial) value of the reference frequency of the carrier frequency f _{n is} stored, as well as the inputs of the second register 5, in which the last (final) value of the reference frequency of the carrier frequency f _k and RAM device 11 is stored where everyone is remembered in yadke priority sample values of the carrier frequency f _i. The final value of the carrier frequency f _k corresponding to the last clock pulse from the second output of the GTI 3 is added to the initial value f _{n of the} carrier frequency in the adder 6, the resulting sum is divided into two in the first divider by two 7 and recorded in register 8 as the average value of the carrier frequency for linear law of frequency tuning in a pulse. Counter 9 counts the number of clock pulses received from the GTI 3 during the duration of the measured radio pulse, this number is divided into two in the second divider by two 10 and acts as an address for sampling the carrier frequency value corresponding to half the pulse duration. This frequency value enters the register 12. The comparison device 13 compares the frequency values and outputs the comparison result to the corresponding output, and if the compared values are equal, then the law of frequency change is linear, if not equal, then non-linear, while if the measured value is greater than the calculated one, then the function of changing the frequency is convex, and if less, then concave.

 The practical feasibility of the claimed object is not in doubt. The functional elements of the claimed object satisfy the criterion of industrial use, as they can be performed, for example, using commercially available integrated circuits, for example, the K553, K555, K1533 series [G. Avanesyan, V. P. Levshin Integrated circuits TTL, TTLSh. -M.: Engineering, 1993].

 INCH 1 can be implemented according to various known schemes, for example, according to the scheme of a panoramic receiver based on the effect of pulse compression [Tsursky D.A. , Peretyagin I.V., Kalyuzhny N.M. Multi-channel panoramic receiver, as USSR N 995285, H 03 J 7/32, publ. 02/07/83 in the official bulletin "Discoveries. Inventions", N 5], or according to the acousto-optoelectronic Fourier processor [Kochemasov V.N., Dolbnya E.V., Sobol N.V. Acousto-optoelectronic Fourier processors. - M.: Radio and Communications, 1987, Fig. 5.12 b, p. 137].

 AD 3 can be performed on semiconductor diodes according to the scheme of a push-pull diode detector [Reference for educational design of receiving-amplifying devices. Ed. Belkina M.K. - Kiev, Vyscha school, 1982, p. 212, fig. 8.7].

 GTI 3 can be implemented on a chip type 533LAZ, two resistors R1, R2, capacitor C1 and a quartz resonator ZQ.

 The counter 9 can be implemented on a chip type 533IE5.

 Registers 4, 5, 8, 12 can be performed on microcircuits of the type 533IR23 (8-bit register with parallel output).

 The device for comparing codes can be implemented on chips of the type 530SP1. The RAM device can be implemented on chips of the type 533IR23 or 533IRZO.

 Divisors into two 7 and 10 are implemented on a universal shift register type 533IR29.

Claims (1)

 A method of measuring the law of tuning the carrier frequency of radio pulses with frequency modulation, which consists in measuring the carrier frequency at the beginning and at the end of the pulse, calculating the average value of the carrier frequency as the arithmetic average of the values of the carrier frequency at the beginning and end of the pulse, characterized in that the value of the carrier frequency is measured at the time corresponding to the middle of the duration of the radio pulse, and compare with the previously calculated average value of the carrier frequency, and if the compared values are equal, then the law Changes linear frequency if not equal - that is nonlinear, while if the measured value is greater than calculated, the frequency change function convex if less then concave.

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