RU2018853C1 - Method and apparatus for measuring inverse losses in ferrite microwave device - Google Patents

Abstract

FIELD: microwave technique. SUBSTANCE: apparatus for measuring losses has serially-connected microwave generator, directional coupler with impedance transformers and meter for measuring the ratio of powers in adjacent arms of secondary channel, a device to be measured, reflected power meter, reflecting member, absorbing load. The reflecting member is located on a length of a regular transmission line and capable of longitudinal movement. During measurements the reflecting member is moved along the transmission line up to a position in which a monitored reflected power level coincides with a predetermined one, then all the signals in an indicator arm of the coupler are compensated for with the aid of the impedance transformer in the adjacent arm, the reflecting member is moved into another position in which the reflected power level coincides with the predetermined one again, the indications of the power ratio meter and displacements of the reflecting member are read out, the measurements are repeated at the presence and absence of the measured ferrite device in the path. Inverse loss value of interest is calculated from the indications of the power ratio meter and displacement value of the reflecting member. EFFECT: enhanced accuracy. 2 cl, 3 dwg

Description

 The invention relates to microwave technology and can be used to measure the return loss of microwave ferrite devices operating in the mode of a given level of reflected power (load with a given VSWR) at a high power level.

 The parameters of microwave ferrite devices operating at a high power level depend on the level of incident and reflected powers passing through the ferrite device. The return losses (decoupling) of decoupling devices: valves, circulators, are most strongly dependent on the level of reflected power. Therefore, the measurement of these parameters is carried out in a predetermined measurement mode, which is determined by the level of incident power and the VSWR of the final unmatched load (which determines the level of reflected power), for example, by means of autostart. N 311218. The disadvantage of this method is the low sensitivity and inconsistency of the measurement mode (the reflected power level changes during the measurement), which leads to the appearance of an additional measurement error.

 The method of measuring return losses at a high power level has higher sensitivity and constancy of the mode (I. Shagin. Measurement methods and setup schemes for measuring parameters of microwave ferrite devices. Reviews on electronic engineering. Series 1 "Microwave electronics", issue 10 (479) . M.: Central Research Institute "Electronics", 1977, p.15).

 However, the positive properties of this method are manifested only when using an inconsistent load having a constant VSWR in the entire frequency range of the measured device and a well-coordinated phase shifter turned on before this load. Actual mismatched load designs are typically a matched absorbing load and a reflective element included in front of it. There are various designs of reflective elements (mismatchers), including broadband, to ensure accurate calculation of their VSWR. However, the creation of well-coordinated absorbing loads and phase shifters is a rather complicated (and not always feasible) technical task (especially at high power levels and at high frequencies). In practice, VSWR 1, 3 is considered acceptable for such structures; in this case, the known constructions of phase shifters (dielectric waveguide, trombone and telescopic coaxial) change their VSWR and the phase of the reflected signal when the phase of the transmitted signal changes. Therefore, in the practical implementation of the method, the influence of reflections from the phase shifter and the absorbing load on the measurement mode and sensitivity cannot be avoided. For example, with a VSWR of an inconsistent load of 2.0 and a change in the VSWR of the phase shifter within 1.2, a four-fold change in the reflected power level is possible, which leads to the appearance of an additional error and a decrease in the measurement sensitivity.

 A known loss meter in ferrite devices (ed. St. N 310200). In it, the creation of the measured signal is performed by switching on the reflecting element before the absorbing end load, therefore it has the same disadvantages - the inconstancy of the measurement mode and the additional errors associated with this, as well as the possibility of a significant decrease in sensitivity (several times).

 The aim of the invention is to improve the accuracy and sensitivity of the measurement of the return loss of microwave ferrite devices operating in the mode of a given level of reflected power at any SWR absorbing load.

 This is achieved by the fact that at a given level of reflected power when using a circuit with a directional coupler at the input of the measured device, a reflected power meter behind it, a reflecting element and an absorbing load, the following operations are performed: power is supplied to the path from the microwave generator, the specified level of reflected is controlled power at the output of the measured device when moving the reflecting element of the mismatch along a regular transmission line to a position at which the controlled level of of the desired power coincides with the set one, compensate all the signals in the indicator arm of the coupler using the impedance transformer installed in the adjacent arm and again move the reflecting element of the mismatch along the regular transmission line to another position at which the controlled level of reflected power re-coincides with the specified one, count the value of this the displacements and readings of the power ratio meter in the indicator arm, and then the device is excluded and with the previous meter readings power ratio, the power ratio meter in the indicator arm is re-counted, and the loss value is calculated as the product of the ratio of the power ratio meter in the indicator arm of the directional coupler in decibels in the absence and presence of the measured device in the path by the quadruple square of the sine of half the phase angle of the reflected signal, determined by the magnitude of the movement of the reflective element.

 The measuring device consists of a cascade-switched microwave generator, a directional coupler with a power ratio meter in the indicator arm and a resistance transformer in the adjacent arm, a measuring device, a reflected power meter of the reflecting element with a given VSWR and absorbing load. The reflecting element is placed on a segment of a regular transmission line with the possibility of adjustable longitudinal movement over a distance, which makes it possible to obtain a given level of reflected power in its two positions.

 Figure 1 shows the structural diagram of a device for measuring the return loss of ferrite microwave devices; figure 2 is a vector diagram of the formation of the total reflected signal at the output of the measured device; figure 3 is a vector diagram of the formation of the measured signal in the indicator arm of the directional coupler.

 The device comprises a generator 1 with an indicator of the generated power level, a directional coupler 2, an impedance transformer 3, an absorbing load 4, a power ratio meter 5, a reflected power meter 6, an absorbing end load 7, a measured ferrite device 8, a mismatch 9, containing a reflecting element ( OE) with a given VSWR.

The measurements are made in the following order: a microwave signal of a given power level is supplied to the path and the reflecting element of the OE of the mismatch 9 is set to the position (l ₁ ), at which the reflected power level (P ₆ ) controlled by it will correspond to the specified one. Then using a transformer of impedances 3 compensate for all the signals received at the input of the power ratio meter 5 until its zero readings (P ₅ = 0). After that, the reflecting element is moved (by which the phase of the reflected signal is shifted) of the MA to another position (l ₂ ), at which the previous readings (P ₆ ) will be observed on the power meter ₆ , and the readings of the power ratio meter 5 are then counted (P ₅ ') . When the OE reflecting element is moved between the positions l ₁ and l ₂ , either a maximum (P _6max ) or a minimum (P _6min ) of the readings of the power meter 6 is observed. Then, the measured device is excluded from the path and the readings of the power ratio meter 5 are read out at the previous (P ₆ ) readings of the reflected power meter 6.

sin

(дБ),, (1) где
Ψ=arcsin

(град) при

Г

Г

(2)
Ψ=180^°-arcsin

(град) при

Г

sinφ <

Г

(3)
φ =

- при Р_6мин между l₁ и l₂ (4)
φ = 180

1-

- при Р_6мaкс между l₁ и l₂ (5)
λ - длина волны генератора 1;

Г

=

;

Г

=

(6)
К_оэ, К_зад. - соответственно КСВн отражающего элемента ОЭ и заданное значение КСВн несогласованной нагрузки.The desired value of the return loss (decoupling) α _arr. determined by the formula:
α _arr = 10lg

sin

(dB) ,, (1) where
Ψ = arcsin

(deg) at

G

G

(2)
Ψ = 180 ^° -arcsin

(deg) at

G

sinφ <

G

(3)
φ =

- at Р _6min between l ₁ and l ₂ (4)
φ = 180

1-

- at Р _6max between l ₁ and l ₂ (5)
λ is the wavelength of the generator 1;

G

=

;

G

=

(6)
To _oe , To the _ass. - respectively, the VSWR of the OE reflecting element and the set value of the VSWR of the inconsistent load.

=P_пад·

Г

(7)
Если конструкция отражающего элемента ОЭ позволяет точно рассчитать КСВн, то целесообразно иметь К_оэ = К_зад при этом φ=Ψ если возможен только приближенный (оценочный) расчет, то целесообразно иметь К_оэ ≥ К_зад, в этом случае значение К_оэ можно найти непосредственно в процессе измерений по значениям отраженной мощности Р_6макс; Р_6мин и уровню падающей мощности.P ₅ '' - readings of the power ratio meter 5 with the measured device excluded from the path, determined depending on the specific measurement conditions (with the readings of the power meter 6 equal to P ₆ ), or when repeating the entire measurement process, as the readings in (˙) l ₂ ; either as readings (P _pad ) in (˙) l ₁ or (˙) l ₂ when the power ratio indicator 5 is connected to arm B of coupler 2, and load 4 to arm A of this coupler, then
P

= P _pad

G

(7)
If the design of the OE reflecting element allows you to accurately calculate the VSWR, then it is advisable to have K _oe = K _ass, with φ = Ψ if only an approximate (estimated) calculation is possible, then it is advisable to have K _oe ≥ K _ass , in this case, the value of K _oe can be found directly in the process of measurements according to the values of the reflected power R _6max ; P _6min and the level of incident power.

- сигнал, отраженный непосредственно от отражающего элемента ОЭ;

- сигнал, соответствующий заданному уровню отраженной мощности;

- суммарный сигнал, образованный отражениями от нагрузки 7, от разъемов (фланцев) рассогласователя 9 и выходного разъема измерителя мощности 6.The measurement principle and the form of the calculation formulas can be understood from the vector diagrams in FIGS. 2 and 3. FIG. 2 shows a vector diagram of the formation of the total reflected signal recorded by the power meter 6, where

- a signal reflected directly from the reflecting element of the MA;

- a signal corresponding to a given level of reflected power;

- the total signal formed by reflections from the load 7, from the connectors (flanges) of the mismatch 9 and the output connector of the power meter 6.

, поэтому возможны два положения ОЭ (l₁ и l₂), при которых сумма сигналов

и

равна

. Угол поворота сигнала

определяется расстоянием между (˙) l₁ и (˙) l₂, обозначим его 2 φ, тогда

повернется на угол 2 Ψ, поэтому из соотношений для треугольника получим:
Ψ = arcsin

[град] (8)
Измеритель мощности 6 дает в точках l₁ и l₂ показания Р₆ ≈ |

|², т. е. уровень отраженной мощности (и режим работы измеряемого устройства) в этих точках будет соответствовать заданному независимо от качества согласования нагрузки 7 и других элементов.When moving the reflective element of the OE, only the phase of the signal changes

, therefore, two OE positions (l ₁ and l ₂ ) are possible at which the sum of the signals

and

is equal to

. Signal rotation angle

is determined by the distance between (˙) l ₁ and (˙) l ₂ , we denote it by 2 φ, then

rotates by an angle of 2 Ψ, so from the relations for the triangle we get:
Ψ = arcsin

[city] (8)
Power meter 6 gives at points l ₁ and l ₂ readings P ₆ ≈ |

| ² , i.e., the level of reflected power (and the mode of operation of the measured device) at these points will correspond to a given value regardless of the quality of matching of the load 7 and other elements.

Figure 3 shows a vector diagram of the formation of the measured signal (U ' _s ), which carries information about the measured magnitude of the return loss.

), образованная отражениями от входа исследуемого прибора 8, отражениями от нагрузки 7, измерителя мощности 6, разъемов рассогласователя 9, направленностью ответвителя 2; сигнал, отраженный от трансформатора полных сопротивлений 3 (сигнал компенсации)

и измеряемый сигнал

=

Q_обр, (9) где Q_обр. - коэффициент передачи по напряжению измеряемого прибора в обратном направлении.The input of the power ratio meter 5 receives the sum of the signals of "interference" (

) formed by reflections from the input of the studied device 8, reflections from the load 7, power meter 6, mismatch connectors 9, directivity of the coupler 2; signal reflected from the impedance transformer 3 (compensation signal)

and measured signal

=

Q _arr. , (9) where Q _arr. - voltage transfer coefficient of the measured device in the opposite direction.

=

+

+

=0
Очевидно, что при этом сигнал

может быть представлен в виде

=-

-

При повороте сигнала

на угол 2 Ψ произойдет поворот на этот же угол только сигнала

, остальные сигналы своей амплитуды и фазы не изменят. Тогда результирующий сигнал

'₅ образуется двумя сигналами с амплитудой |

| сдвинутыми по фазе на угол (180^о - 2 Ψ).At the time of compensation (P ₅ = 0), you can write

=

+

+

= 0
Obviously, the signal

can be represented as

= -

-

When turning the signal

at an angle of 2 Ψ, only the signal will be rotated to the same angle

, the remaining signals of their amplitude and phase will not change. Then the resulting signal

' _{5 is} formed by two signals with amplitude |

| phase shifted by an angle (180 ^o - 2 Ψ).

=

=2

sinΨ
(10) Так как
P

~

U

; P

~

;

~

Г

;

~

Г

,, то из выражений (9) и (10) с учетом того, что α_обр=20 lg

получим выражение (1).According to the rules of summing vectors we get:

=

= 2

sinΨ
(10) Since
P

~

U

; P

~

;

~

G

;

~

G

,, then from expressions (9) and (10), taking into account the fact that α _arr = 20 log

we get the expression (1).

From the analysis of measurements and expression (1) it follows that the measured signal depends only on the set value of the SWR (K _ass ) of the inconsistent path load, the displacement of the reflecting element (Δ l = l ₁ - l ₂ ), the magnitude of the return loss of the measured device and is not dependent neither from the VSWR of the absorbing load (K _mon ), nor from the VSWR of other path elements, and at points l ₁ and l _{2 a} constant predetermined level of reflected power is provided (i.e., the measurement mode), which increases the measurement accuracy.

The measurement sensitivity increases at least 3 times (for K _mon = K _ass = K _oe we have Ψ = φ = 60 ^o ), and for K _mon <K _ass — up to 4 times (Ψ> 90 ^o ) sensitivity increase is always ensured independently of the SWR of the absorbing load and other path elements.

The proposed method and device is quite simple to implement in different sections of waveguides and coaxial lines and can be used at high power levels in a wide frequency range, since they do not impose any stringent requirements for VSWR neither to the load, nor to the circuit elements, nor to the reflective element itself. It is enough that it has a VSWR close to the specified one and the possibility of longitudinal movement along the transmission line. For example, the load of the absorbed power meter MKZ-69 has a VSWR ≅ 1.3 at frequencies up to 3 GHz, at a frequency of 4 GHz the VSWR increases to 1.7-1.8 (not standardized). When measuring the return loss of a ferrite device and using the VSWR mismatch = 2.0, a change in the mode of reflected power is possible within the limits: for SWRf of a load of 1.3 - from 0.04 R _pad to 0.187 R _pad , i.e. more than 4.5 times; with VSWR load of 1.7 - from 0.03 R _pad to 0.48 R _pad , i.e. 16 times.

When using a quarter-wave cylinder made of fluoroplastic (KSVN 2.0) as a reflecting element, placed on a regular line segment with the possibility of moving along it for a distance within half the wavelength for any SWR load, it is possible to set the reflected power level twice corresponding to the specified SWR 2 , 0 (≈ 11% of P _pad ). At the same time, with an VSWR of load 1.3, we have Ψ = 78 ^о , with an VSWR of load 1.7 we have Ψ = 67 ^о , i.e. sensitivity increase will be respectively 3.9 times (5.9 dB) and 3.4 times (5.3 dB), i.e. the sensitivity of the method remains quite high when changing the SWR of the load over a wide range.

 The method does not require the use of phase shifters at the input of the mismatch. High accuracy and sensitivity are maintained at all realistically achievable SWR values of the absorbing load and other elements of the microwave path, and the creation of mismatches with a movable (e.g., dielectric) reflecting element is technically much simpler than creating well-coordinated absorbing loads, phase shifters, or special designs of inconsistent loads with a given VSWR Maintaining a constant predetermined level of reflected power and the necessary uncompensation (unbalance) of the signals in the indicator arm of the coupler, which allows to increase the accuracy and sensitivity of measurements, is achieved by the same movement of the reflecting element.

Claims (2)

 1. A method of measuring the return loss in microwave ferrite devices, based on the supply of power to the path from the microwave generator, monitoring a given level of reflected power at the output of the measured device, compensating for all signals in the indicator arm of the coupler connected to the output of the microwave generator using the microwave installed in the adjacent arm impedance transformer, and reading the readings of the power ratio meter in the indicator arm of the coupler in the presence and absence of the measured device in the path, characterized in that, for the purpose To increase the accuracy and sensitivity of measurements, a given level of reflected power is obtained by moving along a regular transmission line of a reflecting element with a given VSWR to a position at which the controlled level of reflected power coincides with a predetermined one, and after performing the compensation operation, this reflecting element is again moved to another position, at which the controlled level of reflected power repeatedly coincides with the set one, the magnitude of this movement is counted, and the value of the return losses is calculated They are expressed as the product of the ratio of the readings of the power ratio meter in decibels in the indicator arm of the directional coupler in the absence and presence of the measured device in the path by the quadruple square of the sine of half the phase angle of the reflected signal, determined by the magnitude of the movement of the reflecting element.  2. A device for measuring return losses in microwave ferrite devices, containing a series-connected microwave generator, a directional coupler with a power ratio meter in the indicator arm and an impedance transformer in the adjacent arm, a reflected power meter, a reflecting element with a specified VSWR and an absorbing load, while the output of the directional coupler and the input of the reflected power meter are designed to connect the input and output of the measured device, characterized in that, in order to increase of measurement accuracy and sensitivity, a reflecting element with a given VSWR is placed on a segment of a regular transmission line with the possibility of adjustable longitudinal movement over a distance, which makes it possible to obtain a given level of reflected power in its two positions.

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