RU2013781C1 - Device for measurement of parameters of electromagnetic pulse - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: device has primary measurement converter in the form of section of two-wire transmission line-asymmetric strip line. Second electrode has variable height along line which is calculated in agreement with given dependence. Height of second electrode is symmetric on both sides from its center. Space between electrodes is filled with dielectric material with dielectric permittivity higher than that of environment. First electrode covers the whole surface of dielectric material located between electrodes. Second electrode is placed on dielectric material over square curve and is covered from above with dielectric material too which dielectric permittivity is not less than that of material located between electrodes. Matching capacitance is mounted on each end of transmission line. Converter faces source of electromagnetic pulses with one end. Centers of sections of first and second electrodes of it are connected with the aid of matching communication line to recorder. EFFECT: improved reliability of measurements. 2 dwg

Description

 The invention relates to a pulse technique and is intended for use in reference metrological complexes measuring the parameters of pulsed electromagnetic fields with a subnanosecond front (amplitude, duration of the front of an electromagnetic pulse, etc.).

 A device is known for measuring the parameters of an electromagnetic pulse, comprising a capacitive primary measuring transducer in the form of two parallel and coaxial metal disks connected via a communication line to an active resistance and a recorder, while a dielectric material is located between the disks.

 A disadvantage of the known device is the low accuracy of measuring the parameters of EMP of various shapes, which is due to the introduction of errors in the measurement result due to distortion of the studied pulse due to the presence of its own decay time constant of the transient response of the primary measuring transducer.

 Also known is a device for measuring the parameters of an electromagnetic pulse, which is closest to the described one, containing a primary measuring transducer in the form of a segment of a two-wire transmission line, one end of which is open and facing the source of an electromagnetic pulse, while the converter is connected to the recorder by a coordinated communication line, a two-wire line the coupling has a constant impedance along the length of the line due to the fact that the electrodes of the transmission line have along the length of this line a constant width, the value of which is a function of the distance between the electrodes of the line, the dielectric constant of the dielectric between the electrodes, and the wave resistance of the two-wire line.

 This device improves the accuracy of measuring the amplitude-time parameters of electromagnetic pulses due to the fact that instead of a concentrated capacitance, the device uses a two-wire line distributed over the length of the capacitance, which makes it possible to more accurately repeat the shape of the pulse during registration.

 A disadvantage of the known device is that due to the lack of ideal broadband of the communication line, the shape of the measured pulse is not sufficiently identical to the shape of the pulse entering the recorder, which reduces the accuracy of measuring the edge duration and amplitude (the error component associated with distortions introduced by the communication line when measuring EMR with a front duration of less than 1 ns is 10-15%), and the device does not provide any technical methods to reduce the distortion of the pulse shape at p registration. At the same time, the device itself can be used only when measuring EMR parameters with a duration of no more than 15 ns, since when measuring pulses of longer duration, the transmission line should have a length of more than 2 m, and with such a length of the measuring transducer (which is almost impossible in itself) is practically impossible to achieve strict parallelism of the line electrodes, which causes an unacceptable increase in error, i.e. makes the known device inoperative with a pulse duration of more than 15 ns.

 The aim of the invention is to improve the accuracy of measurement and providing the ability to measure pulses of longer duration.

[м], (1) при 0<х≅L/2, где d - расстояние между электродами;
h_к - высота второго электрода на конце линии передачи;
n =

- параметр, зависящий от типа линии связи;
l - длина линии связи;
ε =

;
α- нормированный на частоту коэффициент затухания линии связи, [дБ/м/

];
c - скорость света.This is achieved by the fact that in the device for measuring the parameters of the electromagnetic pulse, containing the primary measuring transducer in the form of a segment of a two-wire transmission line, one of the ends of which is facing the source of the electromagnetic pulse, while the converter is connected to the recorder by a coordinated communication line, the specified two-wire transmission line is made in in the form of an asymmetric strip line, the space between the electrodes of which is filled with a dielectric material, the dielectric constant ₁ is greater than the permittivity of the surrounding medium, and one of the electrodes of this line covers the entire surface of the dielectric material and the other electrode is disposed on the dielectric material in a serpentine curve and topped as a dielectric material, dielectric constant ε ₂ is not less than the dielectric constant of the material disposed between electrodes, while connecting the communication line to the converter for the specified connection with the registrar is carried out in the middle of the length the first and second electrodes, at each end of the transmission line there is a distributed matching capacitance, while the second electrode of the line has a variable height along its length L relative to the surface of the dielectric material between the electrodes, the height of the second electrode is symmetrical on both sides of its middle and maximum in its middle, and the dependence of the height h (x) of the second electrode on the value of the current coordinate x along the length of the transmission line from the middle to the corresponding end of the second electrode is determined from the expression
h (x) =

[m], (1) at 0 <х≅L / 2, where d is the distance between the electrodes;
h _to - the height of the second electrode at the end of the transmission line;
n =

- a parameter depending on the type of communication line;
l is the length of the communication line;
ε =

;
α- frequency-normalized attenuation coefficient of the communication line, [dB / m /

];
c is the speed of light.

 In FIG. 1 is a diagram of the proposed device for measuring the parameters of the electromagnetic pulse; FIG. 2 is a view along arrow A in FIG. 1.

, а также составляющих его векторов электрического

и магнитного

полей). Линия передачи имеет электроды 2 и 3 (например из меди, латуни, серебра) и выполнена в виде несимметричной полосковой линии. Пространство между электродами 2 и 3 заполнено диэлектрическим материалом 4, диэлектрическая проницаемость ε₁ которого больше диэлектрической проницаемости окружающей среды (например, стеклотекстолит, флан, и т.п.). Электрод 2 этой линии покрывает всю поверхность диэлектрического материала 4. Электрод 3 расположен на диэлектрическом материале 4 по меандрической кривой (см. фиг.2) и покрыт сверху также диэлектрическим материалом 5 (см. фиг.1 и 2), диэлектрическая проницаемость ε₂ которого по крайней мере не меньше диэлектрической проницаемости материала 4 (например стеклотекстолит, гетинакс, ситал и т.п.). Электрод 3 линии передачи имеет вдоль своей длины L переменную высоту h(x) относительно поверхности диэлектрического материала 4. Высота электрода 3 симметрична по обе стороны от его середины и максимальна в его середине (точка а). Подключение линии связи 6 (например, в виде радиочастотного кабеля) к преобразователю 1 для соединения с регистратором 7 осуществлено в серединах длин электродов 2 и 3 (точки а, b на фиг.1). На каждом конце линии передачи установлена соответствующая согласующая емкость 8 и 9, распределенная по длине соответствующего конца, как на фиг.2. Зависимость высота h(x) электрода 3 от значения текущей координаты х вдоль длины линии передачи от ее середины (точка а) к соответствующему концу определена из выражения (1).A device for measuring the parameters of the electromagnetic pulse contains a primary measuring transducer 1 in the form of a segment of a two-wire transmission line, one of the ends of which is facing the EMP source (in the drawing), the EMP source is not shown, but the direction of the velocity vector is shown

, as well as its electric vectors

and magnetic

fields). The transmission line has electrodes 2 and 3 (for example, copper, brass, silver) and is made in the form of an asymmetric strip line. The space between the electrodes 2 and 3 is filled with a dielectric material 4, the dielectric constant ε _{1 of} which is greater than the dielectric constant of the environment (for example, fiberglass, flan, etc.). The electrode 2 of this line covers the entire surface of the dielectric material 4. The electrode 3 is located on the dielectric material 4 along the meander curve (see FIG. 2) and is also coated on top with dielectric material 5 (see FIGS. 1 and 2), whose dielectric constant ε ₂ at least not less than the dielectric constant of material 4 (for example, fiberglass, getinax, glass, etc.). The transmission line electrode 3 has along its length L a variable height h (x) relative to the surface of the dielectric material 4. The height of the electrode 3 is symmetrical on both sides of its middle and maximum in its middle (point a). The connection of the communication line 6 (for example, in the form of a radio frequency cable) to the converter 1 for connection with the recorder 7 is carried out in the middle of the lengths of the electrodes 2 and 3 (points a, b in figure 1). At each end of the transmission line, a corresponding matching capacitance 8 and 9 is installed, distributed along the length of the corresponding end, as in FIG. The dependence of the height h (x) of the electrode 3 on the value of the current coordinate x along the length of the transmission line from its middle (point a) to the corresponding end is determined from expression (1).

The above expression (1) is obtained empirically from the condition that the transmission line provides full compensation for the attenuation of the measured signal introduced by the communication line. To ensure this compensation, when calculating dependence (1) using experiment and machine processing of measurement results, various ratios d - the distance between the electrodes, h _к - the height of the electrode 3 at the end of the transmission line, ε ₁ , ε ₂ - the dielectric constant of the material of dielectrics 4 were studied and 5, l are the lengths of the communication line with a frequency-normalized attenuation coefficient α.

 The device operates as follows.

(где L_п - длина первичного измерительного преобразователя, равная длине электрода 2) импульс поля от середины линии достигает согласующей емкости 9, что вызывает возникновение обратной волны тока, распространяющейся вдоль линии передачи в направлении к точкам а и b. Поскольку координата х связана с текущим временем t как t =

, то в каждый момент времени t на входное сопротивление регистратора 7 через линию связи 6 разряжается участок линии передачи, заряженный до потенциала U =

d+

, где Е - напряженность электрического поля ЭМИ. Через время t₂, равное

(где L - длина меандрического электрода 3), за которое обратная волна тока от конца 9 достигнет точек а и b подсоединения преобразователя 1 с линией связи 6, разность потенциалов между электродами 2 и 3 станет равна нулю. За время t₁+t₂ на входе линии связи 6 формируется импульс длительностью

с длительностью фронта

. Сформированный импульс распространяется по линии связи 6 и регистрируется регистратором 7.The device is placed in a field-forming system with a TEM-type wave so that one end of the transmission line (end 8 in the drawing) is facing the EMP source. At the same time, the studied electromagnetic pulse begins to propagate along the primary measuring transducer 1, the parameters of which are the amplitude, the front duration, the pulse duration or the decay time constant recorded by the recorder 7. In this case, a potential difference is induced between the electrodes 2 and 3 of the primary measuring transducer 1 and the potential arises a current wave propagating along the communication line 6 to the registrar 7 from the end 8 of the transmission line to its middle at points a and b. Then after a time t ₁ equal to

(where L _p is the length of the primary measuring transducer equal to the length of the electrode 2), the field pulse from the middle of the line reaches the matching capacitance 9, which causes the appearance of a backward current wave propagating along the transmission line in the direction to points a and b. Since the x coordinate is related to the current time t as t =

, then at each moment of time t, a portion of the transmission line charged to the potential U = is discharged through the communication line 6 to the input resistance of the recorder 7

d +

where E is the electric field EMR. After time t ₂ equal to

(where L is the length of the meander electrode 3), for which the backward current wave from the end 9 reaches the points a and b of connecting the converter 1 with the communication line 6, the potential difference between the electrodes 2 and 3 will become zero. During the time t ₁ + t ₂ at the input of the communication line 6, a pulse of duration

with front duration

. The generated pulse propagates through the communication line 6 and is recorded by the registrar 7.

 Due to the fact that the electrode 3 of the transmission line has along its length a variable height h (x) relative to the surface of the dielectric material 4, which varies according to the indicated law (1), the shape of the pulse received at the input of the recorder 7, most accurately repeats the shape of the pulse of the electromagnetic field, since the device compensates for the losses that occur in the communication line due to the skin layer by preliminary distortion (amplification) in a predetermined manner from the time of the measured pulse in the primary Converter 1.

раз дает также дополнительные преимущества устройства за счет расширения временного диапазона измеряемых импульсов в сторону больших значений длительности (от 15 нс до мкс) и повышает технологичность изготовления первичного измерительного преобразователя 1 по сравнению с прототипом, где для взаимной установки электродов необходимы дополнительные крепежные элементы, которые неизбежно технологически усложняют изготовление устройства и вносят в линию передачи, непредусмотренные паразитные искажения в исследуемый сигнал.Due to the fact that the two-wire transmission line is made in the form of an asymmetric strip line, the space between the electrodes 2 and 3 of which is filled with dielectric material 4, and the electrode 2 of this line covers the entire surface of the dielectric material 4, and the electrode 3 is located on the dielectric material 4 along the meander curve and is also coated on top with a dielectric material 5, the dielectric constant of which is at least not less than the dielectric constant of the material located between the electrodes 2 and 3, is sufficient an increase in accuracy is possible since the distortion of the field penetrating into the space between the electrodes is excluded, the structure of the field inside the strip line repeats the structure of the incident TEM wave, and the asymmetry of the strip line formed by the indicated configuration of the electrodes and the dielectric between them is in good agreement with the asymmetry of the communication line (radio frequency cable), eliminating the distortion of the measured signal during its transmission from points a, b to the recorder, and also reducing the rise time of the transient response triads to its ultimate theoretical significance. A significant increase in the physical length of the electrode 3 (due to its meander shape, allowing many times to increase the length L of the electrode 3 with a minimum length L _{p of the} transducer) and a decrease in the wave propagation velocity in the transducer 1 in

times also gives additional advantages of the device by expanding the time range of the measured pulses in the direction of large values of duration (from 15 ns to μs) and increases the manufacturability of manufacturing the primary measuring transducer 1 in comparison with the prototype, where additional fasteners are necessary for the mutual installation of the electrodes, which are inevitable technologically complicate the manufacture of the device and introduce into the transmission line, unintended spurious distortions in the signal under study.

 The connection of the communication line with the converter for the indicated connection with the recorder, carried out in the middle of the lengths of the first and second electrodes, which are symmetrical with respect to their middle, eliminates spurious emissions associated with the excitation of the sections of the meander electrode 3, perpendicular to the magnetic field vector of the electromagnetic radiation, magnetic field, since these emissions are the same in amplitude and opposite in sign in the symmetrical sections of the electrode 3 relative to the middle.

 The specified introduction at each end of the transmission line of the corresponding distributed matching capacitance 8, 9 in combination with these features increases the accuracy of the measurement by providing the smoothest transition characteristic of the device.

длиной 10 м; первичный измерительный преобразователь на основе несимметричной полосковой линии с переменной вдоль длины линии высотой меандрического электрода, высота которого определена по зависимости (1).When implementing the device, the following equipment was used: EMR generator, developments based on the TEM cell; recorder - stroboscopic oscilloscope S7-13; communication line - radio frequency cable RK-50-4-21 with α = 1.46 * 10 ^-5 dB / M /

10 m long; primary measuring transducer based on an asymmetric strip line with a meander electrode height variable along the line length, the height of which is determined by dependence (1).

The following is the data for two transmitter designs. The same for all options are: the length of the primary measuring transducer L _p = 0.2 m, the width of the primary measuring transducer is 0.1 m, the distance between the electrodes is d = 1 mm, the electrode material is a copper wire with a diameter of 1 mm, the pitch of the meandering wire is laid along the length measuring transducer 2 mm.

Option 1: fiberglass (ε _1,2 = 3,5) was used as dielectric materials 4 and 5.

Option 2: materials PKT-5 (ε ₁ = 5) and PKT-10 (ε ₂ = 10), respectively, were used as dielectric materials 4 and 5, respectively.

 Comparative studies of the described device and prototype were conducted. When studying the characteristics of the prototype, the same EMR generator, recorder, the same communication line 10 m long, the distance between the electrodes d = 3 mm, the electrode material - copper, the width of the electrodes 12 mm were used.

 All device variants and prototype were pre-certified according to GOST 8.207-76.

 The amplitude and rise time of the front of field pulses with an amplitude of 500 V / m and a front duration of 250 ps at a pulse duration of 5 ns and 25 ns were measured, the values of the components of the measurement error associated with the attenuation of the signal in the communication line were determined (below, for brevity, these error components are indicated as "measurement error").

 1 version of the device. Measurement results for both pulse durations: amplitude 501 V / m, measurement error 4%, rise time 280 ps, measurement error 5%.

 2 version of the device. Measurement results for both pulse durations: amplitude 498 V / m, measurement error 3%, rise time 270 ps, measurement error 5%.

 Prototype. Measurement results for a pulse duration of 5 ns: amplitude 485 V / m, measurement error 10%, rise time 420 ps, measurement error 15%.

 A pulse of 25 ns duration exceeds the duration of the transient response of the primary converter, which does not allow it to be registered with the prototype device.

 Thus, as shown by experimental studies, the proposed device provides improved measurement accuracy (measurement error 3 ... 5%) compared with the prototype (measurement error 10 ... 15%), while using the described device precision measuring parameters of electromagnetic radiation with a subnanosecond front in a wide time range (> 15 ns) of pulse durations.

Claims (1)

DEVICE FOR MEASURING ELECTROMAGNETIC PULSE PARAMETERS, comprising a primary measuring transducer in the form of a segment of a two-wire transmission line, one end of which is facing the electromagnetic pulse source, while the output of the converter is connected to the recorder by a coordinated communication line, characterized in that, in order to improve the accuracy of measurement of parameters pulses and providing measurement of longer pulses, the two-wire transmission line is made in the form of an asymmetric strip line, the space between the electrodes of which is filled with a dielectric material, the dielectric constant ε _{1 of} which is greater than the dielectric constant of the environment, and one of the electrodes of this line covers the entire surface of the dielectric material, and the second electrode is made in the form of a meander and also coated on top with a dielectric material, whose dielectric constant ε ₂ at least not less than the dielectric constant of the material located between the electrodes, with the middle in the lengths of the first and second of the electrodes is the output of the converter, a distributed matching capacitance is installed at each end of the transmission line, while the second electrode of the line has a variable height along the length L relative to the surface of the dielectric material between the electrodes, the height of the second electrode is symmetrical on both sides of its middle, and the dependence of the height h / x / of the second electrode from the value of the current coordinate x along the transmission line from the middle to the corresponding end of the second electrode is determined from the expression:
h (x) =

, m
for 0 <x ≅ L / 2,
where d is the distance between the electrodes;
where h _to - the height of the second electrode at the end of the transmission line;
n =

- a parameter depending on the type of communication line;
ε =

,
l is the length of the transmission line;
α - frequency-normalized attenuation coefficient of the communication line, dB / m /

;
c is the speed of light.

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