SU1423966A2 - Method of measuring reflectivity index of radio-absorbing material - Google Patents

Abstract

This invention relates to the field of radio measurements. The purpose of the invention is to increase accuracy. It is known that the intensity of the electromagnetic field decreases with increasing distance from the transmitting antenna (A) according to the 1 / g law, where r is the distance between A. To increase accuracy simultaneously with the displacement of the test material in the direction normal to its surface the distance between A according to the law defined by the formula LI ..; .. 2uh (F-F) (F ctgoi - F ctgV),: where d R is the value of the change in the distance between A; uh is the amount of movement of the test material ;.o (,, o is the angles of incidence of the electromagnetic wave on the test material; F, F are the corresponding values of the receiving direction A radiation pattern on the strength of the field in the direction of the transmitting A. Equipment that implements the method contains transmitting A 1, receiving A 2, which is directed to the mirror reflection point on the surface of the tested radio absorbing material 3 with the installation of the polarization plane in the horizontal plane 4, perpendicular to the 5 plane of the wave incidence material, directional coupler 6, gr 7, wattmeters 8, 9, rotary vcTp-in., 10, 1 or 13

Description

|

Yu

00

The invention relates to the field of radio measurements, can be used to determine the reflection coefficient of radio absorbing materials (PIIM) in the microwave range and is an improvement of the invention according to the authors. St. USSR № 1219984.

The purpose of the invention is to increase the point

NOSTIO.

The drawing shows a structural electrical circuit diagram of a device that implements a method for determining the reflection coefficient of a radio absorbing

p - positive integer

number,

The disadvantage of this method is the large measurement error k.o, at the lower frequencies of the microwave range. This is due to the fact that the NAM of the transmitting antenna in the direction of the specular reflection point on the surface of the tested RPM and the receiving antenna in a. the direction of the transmitting antenna as the RPM moves, it will also change at different angles oi, and uij will drop the wave as the test RPM will be different and

material.

The method for determining the Reflection coefficient of a radio-absorbing material is implemented in the following manner,

According to the main author. St. USSR ffj 1219984 describes a method for determining the reflection coefficient (k, o,) RPM

K (20 lg4-5Vp -iu T-f l)

, “H Prno, / + 31PY,

inclusive in irradiation. RPM and receiving antenna electromagnetic wave by means of a transmitting antenna,

: strapping RPM in the direction of normal H to its surface and measuring the maximum and minimum value of the signal at the receiving receiver's output.

In this case, measurements are performed with the direction of the maximum of the diagrams of the directivity (DN) of the receiving antenna E, the specular reflection point on the surface of the RPM and the orientation of the maximum of the transmitting antenna in the direction of the antenna antenna, and additionally eject the angles of incidence of the electromagnetic wave to the RPM corresponding to max. The minimum and minimum values of the signal at the output of the receiving antenna, k module-AND phase k.o, are determined by the formulas:

- Р mm 1

W 2ft I 2n - -r-- - -4 --- T I sinot, sintjL J

one

sinui.,

one)

(2)

de and ";"

S „And o.,.

the maximum and minimum values of the signal at the output of the receiving antenna; the corresponding angles of incidence of the electromagnetic wave on the RPM ;,

15 respectively, constitute F (.

and

0

five

0 d

lii. For the case when (X., -s. Signal Rupei output antenna

Fot

will be underestimated in (---) times, and

Fci,

ci, tx: 2 - overestimated as many times. There is an error in the definition of k.o. according to the formula (1). Even with a change in the DN by 4%, the measurement error k.o, increases to 60%.

Let the DN of the receiving antenna in terms of the field intensity be in the direction of the transmitting antenna, and the transmitting antenna in the direction of the point of the mirror reflection on the surface of the test RPM at angles ei, and f (. The wave fall on the test RPM is

F and Fj, and by power F and F respectively 5

vetstvenno. Let the power of the signal induced in the receiving antenna from the direct signal of the transmitting antenna also vary at the angles ei and oig of the wave incidence is P and P, respectively. Then the maximum and minimum signal power is determined from the following relationships:

Ka, f,

F, | K /. sinoi.j (3)

45

-jpT F, -4p7- F,

JKJ-sinisijj (4)

50

where ik / module k o. the subject

RPM, We put a condition that

-Nf57- F,

yy j

(five)

55

then, dividing the left and right parts (21) into (22) we get

(K - 1 iK jJis

 1 TO

(6)

Making the transformations, we obtain the formula (1) to calculate the modulo k.o. PI1M tested.

Thus, it was found that Formula (1) will be true only if condition (5) is fulfilled, i.e. Under the condition that the power of the signal induced in the receiving antenna from the forward signal of the transmitting antenna is

constant ratio:

R,

those. must

1 P

It is known that the electromagnetic field strength decreases with increasing distance from the transmitting antenna.

by

1 to the law

where r is the distance

between antennas. Changing the distance between the antennas is directly proportional to the change in the DN of the receiving antenna by the direction of the field in the direction of the transmitting antenna, thereby obtaining the change in the power of the signal induced in the receiving antenna from the direct signal of the transmitting antenna. the change in the DN of the receiving antenna in power in the direction of the transmitting antenna, i.e. In this way, the power of the signal induced in the receiving antenna from the forward signal of the transmitting antenna can be kept constant.

Determine the ratio between the change in the distance between the AR antennas and the displacement of the RPM uh.

Calculate first the tangents of the angles

Falls):

d. to the formulas (see plotgoi

R;

2h

tgci --G-

R

2h

de R, R is the distance between antennas, us at angles of the AC and with

respectively; h, h - heights

antennas above RPM at angles ct and oi, respectively. stately. By known values of F and F

define relation:

R F R F

where F, F - corresponding to the corners

a, oi values of the NAM of the receiving antenna in the direction of the transmitting antenna. Solving together equations (8), (9)

and (10), we get

ten

(eleven)

and H

(7)

15

(12)

(13)

0

25 30 35

From (12) and (13) we determine the magnitude of the change in the distance between the AR antennas and the displacement of the RPM uh by the formulas:

,

BK R - R

R (- | g - 1) (14)

40

(eight)

.

50

45 A device that implements a method for determining the reflection coefficient of a radio-absorbing material contains (see drawing) a transmitting antenna 1, which is directed to the receiving antenna 2, and the receiving antenna 2 to the specular reflection point on the surface of the tested RPM 3 ( is included) with the installation of the polarization plane in the horizontal plane 4, perpendicular to the plane of the 5-drop of the wave on the tested RPM. The input of the transmitting antenna 1 through the directional coupler 6 is connected to the generator 7 of the corresponding diapazon frequency, and the output of the receiving antenna 2 - wattmeter 8. In the side arm of the directional coupler 6

connect another wattmeter 9. Receiver controls it by wattmeter 9, and by

The antenna 2 is installed in the rotary device 10, which allows the antenna to tilt in the I direction to the mirror reflection point on the surface of the tested RPM 3, and also to move it in the horizontal plane in the direction of the transmitting antenna 1, for example side slots10

the wattmeter 8 measures the maximum and minimum values of the P signal and, using formula (1), calculate the co. tested RPM,

Claims (1)

Formula invented and The method for determining the reflection coefficient of a radio absorbing material without an echo chamber, if the measurements are 15 by the author. St. No. 1219984, characterized in that, for the purpose of ko RPM is produced in neyo Calculate the angles about and oi of the wave incidence on the tested RPM at given R, R and h, I r ot arctg 2h increase in accuracy, simultaneously with the movement of the test material in the direction normal to its surface, the distance between the antennas changes according to the law determined by the formula ei arctg ---, r R 2h  By dna antenna for log-periodic. | antennas determine the values of the DNs at angles 1 et and ftt F and F, respectively, but determine uR by the formula (18), I When generator 7 is on, the signal at the output of receiving antenna 2 is changed to a maximum of - P wax and minimum P Win by moving RPM 3 along normal to its surface with a change in the height of the location of the antennas above the RPM from h to h, 2. (- drawing) and changing the distance between the antennas c.R, to R {t. In this case, the distance between the antennas and the antennas is changed by the law (18). The power at the input of the transmitting antenna, 1 is kept constant, the wattmeter 8 measures the maximum and minimum values of the P signal and, using formula (1), calculate the co. tested RPM, Formula invented and The method for determining the reflection coefficient of a radio absorbing material, increasing accuracy, simultaneously with moving the test material in the direction normal to its surface, changes the distance between the antennas according to the law determined by the formula 25 F - F & R 2uh -p -tgr - Fcti; t where & R is the amount of change in the distance between the antennas; uh is the amount of movement of the tested material; OS and OB - at the point of incidence of an electromagnetic wave on the test material; F and F are the corresponding values of the receiving antenna pattern for the field strength in the direction of the transmitting antenna.