RU2024884C1 - Phase calibrator - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: calibrator has frequency standard 1, standard frequency unit 2, two phase-setting channels 3, each of them having unit 4 of phase-setting, frequency synthesizer 5, frequency converter 6 and selective filter 7. Bypass units 8, each of them consisting of series connected amplifier and attenuator, are introduced into the calibrator. EFFECT: enhanced reproduction accuracy of phase shift angle at the expense of lessening the mutual influence between the phase-setting channels. 1 cl, 2 dwg

Description

 The invention relates to electrical measurements, namely to phase measurements between two electrical signals, and can be used to certify and verify accurate measuring equipment (phase meters, phase indicators, phase comparators).

A device for reproducing a phase angle angle (UFS), comprising a reference generator, a block of reference frequencies connected to two identical channels made of series-connected frequency synthesis unit, electronic switch, frequency beat unit, selective output filter [1]. The disadvantage of this setup is an error of the order of 0.05 ^about in a small frequency range from 0.001 Hz to 30 kHz.

There is also known a technical solution, which is the closest in technical essence to the invention — an installation for reproducing UFS, which implements a method for discrete setting of phase shift in a wide frequency range [2]. The installation comprises a reference generator, a block of reference frequencies connected to two identical channels made of a frequency synthesis unit and an attenuator, a switch of two reference frequencies, two delay elements, two coincidence elements, two transition shapers, two triggers and a counter. The disadvantage, as studies have shown, is in the order of 0.03 ^{of the} error caused by the fact that there is parasitic coupling between the two elements of the frequency control channel set through wires connected to the reference frequency block.

 The purpose of the invention is to improve the accuracy of the reproduction of UVS in a wide range of frequencies.

This goal is achieved by the fact that in the phase calibrator containing the reference generator, the block of reference frequencies, two phase-setting channels, each of which contains series-connected phase setting block, a frequency synthesizer, a frequency converter and a selective filter, the input of the block of reference frequencies is connected to the output of the reference generator, the outputs of the reference frequency unit are connected to the inputs of one of the phase-setting channels, between the inputs of the same phase-setting blocks, frequency synthesizers and frequency converters of both phase-setting catch blocks included junctions, each of which comprises a series-connected high-frequency amplifier and an attenuator, amplifier, the gains of high frequency attenuator and at each interchange unit satisfy the relation
To _at ^. K _A = 1, where K _y , K _A are the transmission coefficients of the amplifier and attenuator, respectively.

Decoupling nodes, made in the form of a series-connected linear high-frequency amplifier and attenuator, make it possible, in comparison with known technical solutions, to significantly reduce the effect between phase-setting channels by reducing spurious coupling along the output-input circuit of the isolation node. Since the amplifier gain K _FF, and the damping factor of the attenuator K _s are chosen equal, the overall direct transmission factor is close to unity, so the signals in the two channels do not undergo changes, and parasitic coupling between the channels decreases in K _of times compared with interchanges consisting only of an amplifier with a coefficient of K _us . Since the nodes of the isolation are linear decoupling elements with the same input and output resistances, they do not affect the spectral composition of the signal and do not introduce additional error when setting the phase shift.

 The presence of spurious communication between the channels is one of the main sources of the UFS error. Reducing communication using decoupling nodes can improve the accuracy of reproduction of UVS.

 In FIG. 1 shows a functional diagram of a phase calibrator; in FIG. 2 - implementation of the junction node.

The phase calibrator contains a reference oscillator 1 connected to a reference frequency block 2 and two identical channels 3. Each channel 3 contains a phase setting block 4, a frequency synthesizer 5, a frequency converter 6 and a selective filter 7. The outputs of the reference frequency block 2 are directly connected to two the inputs of the phase setting block 4, the free inputs of the frequency synthesizer 5, the second input of the frequency converter 6 of one channel, and through the nodes 8 of the isolation - to the same inputs of the other channel 3. The nodes 8 of the isolation are made in the form of The high-frequency amplifier 9 and attenuator 10 are included. The reference oscillator 1, the reference frequency block 2, and the frequency synthesizer 5 can be used from the frequency synthesizer Ch6-31. As a reference generator 1 can also be used with higher technical requirements for frequency stability frequency standard Ch1-69. The phase setting block 4 is designed to generate a phase shift control signal and is made of two delay elements, two identical transition conditioners, a coincidence circuit, a D-flip-flop, an RS-flip-flop, an “I” circuit and a programmable pulse counter and is similar to that described in [2]. A frequency synthesizer 5 is designed to switch frequencies, as well as to specify a phase shift. Frequency synthesizer 5 is similar to the serial frequency synthesizer Ch6-31. The frequency converter 6 is made according to the ring circuit of the frequency converter with matching high-frequency transformers on diodes, for example, KD 514, which provides suppression of spurious components. The load of the frequency converter 6 is the selective filter 7. The selective filter 7 performs the selection of useful signals and is made in the form of a six-link semi-active filter. Junction nodes 8 are designed to suppress spurious connections between the channels of phase setting. For UR _, it is advisable to use two series-connected links, each of which consists of a high-frequency amplifier, the output of which is connected to the attenuator with a attenuation equal to the gain of the amplifier in a wide frequency range (Fig. 2). The attenuator can be made according to the scheme of the U-shaped link. Thus, the total attenuation of spurious communication between the channels when using two links will be at least 120 dB, and SD ₁ ... SD _{k-1 will} be single-link.

 Let us consider the operation of the phase calibrator and the influence of the UFS reproduction errors.

From the signal of the reference generator 1 in the block 2 of the reference frequencies, a series of pure harmonic signals with frequencies is obtained
f ₁ = nf _kg , f ₂ = (n + 1) ^. f _kg, f ₃ = (n + 2) ^. f _kg , ...

· n. Практически n = 30, f_кг = 10^-6 Гц, тогда при k = 9, l = 24. В синтезаторе 5 частоты формируется сигнал с частотой, изменяющейся во всех его преобразовательных устройствах от минимального значения
f_min = f

l+

+

+

+ ... +

+ ... +

(2) до
f_max = f

l+

+

+

+ ... +

+ ... +

, (3) где m - число смесителей-делителей (разрядов) в синтезаторе частоты,
р - значение коэффициента деления частоты на выходе разряда.(1) f _i = (n + i) f _kg , ... f _k = (n + k) ^. f _kg , where n is the frequency multiplier,
k is the final value of the series from 1 to 9, as well as one reference frequency f _op = l ^. f _kg , where l =

N. Almost n = 30, f _kg = 10 ^-6 Hz, then at k = 9, l = 24. A signal is generated in the frequency synthesizer 5 with a frequency that varies in all its converter devices from the minimum value
f _min = f

l +

+

+

+ ... +

+ ... +

(2) to
f _max = f

l +

+

+

+ ... +

+ ... +

, (3) where m is the number of mixer-dividers (discharges) in the frequency synthesizer,
p is the value of the frequency division coefficient at the discharge output.

+

+ ...n ₁₁ ÷ n _1m is the frequency multiplier in the first discharge of the frequency synthesizer, depending on the final value of the series,
n _k1 ÷ n _km is the frequency multiplication coefficient in the Kth discharge of the frequency synthesizer, depending on the final value of the series. Usually p is equal to 10. In practice, out of the possibility of decad frequency organization of the set of frequencies, m is 9, and n ₁₁ ÷ n _km are in the range 3.0 + 3.9. At the channel outputs after the frequency converter 6 and the selective filter 7, a frequency range is obtained
f _out = [f _min ÷ f _max ] - f _n =

+

+ ...

+ ...+

- n

· f_кг , (4) где f_n = nf_кг частота, подводимая ко вторым входам преобразователей 6 частоты от блока 2 опорных частот. Синтезатор 5 частоты работает на принципе переключения частот n₁mf_кг, n₂mf_кг на время Δt в смесителе-делителе (разряде). Таким образом, значение заданного УФС будет равно
Δφ₃ = Δω·Δt = (ω₂-ω₁)·Δt =

f_кг·Δt·2π . (5)
Погрешность УФС будет зависеть от:
неточности задания временного интервала Δt,
неточности установления значения частот,
временной нестабильности частот,
связи между каналами
δ φ=δ

+δ φ_н+δ φ_вн+δ φ_св , (6)
δφ_св = arctg

+

, (7) где γ₁₂ и γ₂₁ - коэффициенты проникновения сигнала из первого канала во второй и наоборот. При условии U_c1 = U_c2 и γ₁₂ = γ₂₁ = γ, то δ φ_св = arctg γ' = arctg 2 γ , (8) где γ' - коэффициент связи между каналами или между узлами каналов, т.е.. . . +

+ ... +

- n

· F _kg , (4) where f _n = nf _{kg is the} frequency supplied to the second inputs of the frequency converters 6 from the block 2 of the reference frequencies. Frequency synthesizer 5 operates on the principle of switching frequencies n ₁ mf _kg , n ₂ mf _kg for a time Δt in a mixer-divider (discharge). Thus, the value of the specified UVS will be equal to
Δφ ₃ = Δω Δt = (ω ₂ -ω ₁ ) Δt =

f _kg · Δt · 2π. (5)
The error of the UVS will depend on:
inaccuracies in setting the time interval Δt,
inaccuracies in setting frequency values,
temporary frequency instability,
communication between channels
δ φ = δ

+ δ φ _n + δ φ _int + δ φ _sv , (6)
_{communication} δφ = arctg

+

, (7) where γ ₁₂ and γ ₂₁ are the coefficients of signal penetration from the first channel into the second and vice versa. Under the condition U _c1 = U _c2 and γ ₁₂ = γ ₂₁ = γ, then δ φ _cb = arctan γ '= arctan 2 γ, (8) where γ' is the coupling coefficient between channels or between channel nodes, i.e.

γ_i , (9) где S - число узлов в каналах.γ ′ =

γ _i , (9) where S is the number of nodes in the channels.

Consider the level of these errors:
δ φ Δt = 10 ^-3 / p ^m rad
δ φ _n = 10 ^-7 rad for serial synthesizers,
δ φ _int = 10 ^-9 ÷ 10 ^-8 rad for serial synthesizers,
δ φ = 0.114 ^for _{communication} with γ '= 0,001 (1 mV at 1 V).

It follows that the connection between the channels is the dominant source of error. To reduce its influence, the inputs of two channels 3 are interconnected via nodes 8 of the isolation UR ₁ ... UR _to . These nodes 8 of the isolation consist of series-connected high-frequency amplifiers 9 with a gain of K _must and an attenuator 10 with a coefficient of attenuation of K _don . Decoupling nodes 8 are linear decoupling elements that do not introduce additional harmonic components into the signal. The same input and output resistances of the isolation nodes 8 ensure coordination of the complex resistances of previous and subsequent high-frequency circuits without signal distortion.

= 1 , (10) где К_у - коэффициент передачи усилителя 9, равный К_ус,
К_А - коэффициент передачи аттенюатора 10, равный К_осл = 1/К_ус.The gain of the amplifier 9 and the attenuation coefficient of the attenuator 10 are chosen equal. The optimal is K _us = 10 + 30, since with this gain coefficient the amplifier 9 achieves the greatest linearity of the amplitude-frequency characteristic and the lowest noise level, which is crucial for phase setting. The direct transfer coefficient of the node 8 isolation is equal
K _p = K _y · K _A = K _yc ·

= 1, (10) where K _y is the transfer coefficient of amplifier 9, equal to K _us ,
K _And - the transfer coefficient of the attenuator 10, equal to K _don = 1 / K _mustache .

Следовательно, при К_ус = К_осл, K_осл =

. Таким образом, при К_п = 1 проникновение паразитных составляющих по цепи выход-вход ослабевает в К_осл раз больше, чем при применении просто усилителя. Амплитуды сигналов, поступающих в оба канала через узлы 8 развязки, не искажаются, так как К_п = 1, поэтому не требуется их дополнительной коррекции. Включение узлов 8 развязки при одинаковых сигналах на входах каналов 3 будет уменьшать связь между каналами 3 в К_рраз, где коэффициент развязки К_р равен
К_р = К_ус . К_осл = К_ус ². (11) Например, при К_ус = К_осл = 10 следует, что К_р = К_ус ² = 100 и погрешность от связи между каналами 3 фазозадания снижается с 0,114 до 0,0011^о.It is assumed that the amplifier 9 at the decoupling nodes is covered by deep feedback. Therefore, the output-input feedback coefficient is defined as
K _p (reverse) =

Therefore, when K _us = K _donkey , K _donkey =

. Thus, when K _p = 1, the penetration of parasitic components along the output-input circuit weakens in K _donkey times more than when using just an amplifier. The amplitudes of the signals entering both channels through the nodes 8 of the isolation are not distorted, since K _p = 1, therefore, their additional correction is not required. The inclusion of nodes 8 isolation with the same signals at the inputs of channels 3 will reduce the connection between channels 3 in K _p times, where the isolation coefficient K _p equal
To _p = To _us . K _donkey = K _mustache ² . (11) For example, when K _us = K _donkey = 10 it follows that K _p = K _us ² = 100 and the error from the connection between the channels 3 phase setting decreases from 0.114 to 0.0011 ^about .

 To increase the isolation in circuits, where the stray coupling coefficient between the phase detection channels is greatest, for example, at the high-frequency channel inputs, two isolation nodes can be connected in series. More than two decoupling nodes connected in series, it is impractical to use.

This solution was used in the UFS calibration equipment. Studies have shown that the error in the UFS task has decreased to 0.005 ^o in the frequency range from 10 Hz to 10 MHz.

Claims (2)

 1. PHASE CALIBRATOR containing a reference generator, a block of reference frequencies, two phase-setting channels, each of which contains a series-connected phase setting block, a frequency synthesizer, a frequency converter and a selective filter, the input of the block of reference frequencies is connected to the output of the reference generator, the outputs of the block of reference frequencies are connected with inputs of one of the phase-setting channels, characterized in that, in order to increase the accuracy of reproducing the angle of the phase shift, between the same inputs of phase-setting blocks, synthesizers Toty and frequency converters fazozadayuschih both channels included junction blocks, each of which comprises a series-connected high-frequency amplifier and an attenuator. 2. The calibrator according to claim 1, characterized in that the transmission coefficients of the high-frequency amplifier and attenuator in each isolation block satisfy the ratio
K _y · K _a = 1,
where K _y , K _a are the transmission coefficients of the amplifier and attenuator, respectively.

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