SU1019358A1 - Pulse signal phase fluctuation measuring device - Google Patents

Description

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The invention relates to television technics and can, in particular, be used in the construction of instrumentation to measure the phase instability of the synchronization signal of television receivers.

A device for measuring phase fluctuations is known, comprising a main and auxiliary filters connected in series, a phase detector, one input of which is connected to the output of the main filter and the second to a wideband filter connected to the mixer. The device is equipped with a smooth local oscillator for transferring the phase ratios of the input signal to the intermediate frequency. 3 The disadvantage of this device is the low accuracy of the measurement, due to the fact that the intrinsic phase instability of the smooth local oscillator is transferred to the intermediate frequency. As a result of fluctuations in the phase of the intermediate frequency signal, they are the product of the phase instability of two sources, the studied and smooth local oscillator.

The closest in technical essence to the invention is a device for measuring the phase instability of a pulsed signal, containing a phase discriminator connected by one input to a pulse rammer (limiter), a sawtooth voltage shaping circuit, the input of which is connected to frequency controlled the generator of sinusoidal oscillations, and the output with the second input of the phase discriminator. The output of the phase discriminator is connected to the control input of the sinusoidal generator through a low-pass filter 2. nyh oscillations D.Nedostatkom known device is a low measurement accuracy.

The phase discriminator forms a voltage at its output, the variable component of which is proportional to the fluctuations of the phase of the test strip relative to the phase of the sawtooth voltage, and therefore, the phase of the controlled generator of sinusoidal oscillations. This imposes strict requirements on the phase stability of the signal generator, the latter depends on the transparency band of the low-pass filter. The narrower the transparency band of the filter, the more precise measurements of phase fluctuations are possible in the lower frequency range. In addition, the filter bandwidth must be wide enough to allow the tuning of the controlled oscillator to the frequency of the signal under study. With significant fluctuations in the frequency of the signal under investigation, it is difficult to satisfy the contradictory requirements placed on the low-pass filter. A compromise in choosing the filter transparency band reduces the measurement accuracy.

The purpose of the invention is to improve the measurement accuracy of the fluctuations of the phase of a pulsed signal.

To achieve this goal, a device containing a phase discriminator connected by inputs to a pulse shaper and a sawtooth shaper, a low-pass filter and an indicator, a delay element, an integrator and a frequency divider, and an element for-; supports are connected between the output of the pulse generator and the upstream input of the sawtooth voltage generator, the output of the phase discriminator is connected to the integrator input, the output of which is connected to the indicator and through the low-pass filter to the control input of the sawtooth voltage driver, the input of the frequency divider is connected to the output of the delay element, and the output - with the input of the installation of the zero integrator.

The piloaze voltage shaper can be made in the form of a source controlled by an external signal. An adjustable voltage source is connected via an electronic key controlled by an external electric signal with a capacitor, current generator and buffer cascade, the second capacitor plate grounded.

Such a construction of a sawtooth voltage former provides virtually instantaneous control of the initial level of the sawtooth voltage and the high linearity of the working section of this voltage, which increases the accuracy characteristics of the device as a whole.

The integrator can be implemented as an operational amplifier, the non-inverting input of which is grounded, and a pe3 lo is connected to the inverting input

A sistor, at the same time, between the output of the operational amplifier and the RGO, an inverting input includes a parallel-connected capacitor and an electronic switch controlled by an external electrical signal. In this construction of the integrator, a linear dependence of the capacitor charge current on the input voltage is provided, as well as the ease of setting zero integrator si (- a voltage acting on the control input of the electronic key.

Physically, the increase in the measurement accuracy is due to the fact that the delayed and undelayed signals of one (test) source, i.e., participate in the formation of the output voltage of the phase discriminator. signals that have not undergone additional changes period. The feedback action in the device leads to such a change in the initial level (but not the period) of the sawtooth voltage, in which both the constant and variable signal components lying in the transparency band of the low-pass filter are excluded from the input signal of the phase discriminator.

In this case, in known devices, the signal carrying information about phase fluctuations is the result of the interaction of two signals: the studied and local oscillator, which has its own phase instability.

FIG. Figure 1 shows a block diagram of a device for measuring fluctuations in the phase of a pulsed signal; LD, FIG. 2 - voltage diagrams at individual points of the device.

The proposed device for measuring the fluctuation of the phase of the pulsed signal (Fig. 1) includes a phase discriminator 1 connected by one of its inputs with the output of the driver 3 of the sawtooth voltage. In this case, the phase discriminator can be performed, for example, on a field-effect transistor, the drain of which is supplied with a sawtooth voltage from the shaper 3, the pulse signal under study from the shaper shaper is supplied from the shaper of the 2 pulses, and a grounded plate is connected to the source circuit.

The shaper 2 pulses can be made in the form of a single vibrator. The phase discriminator 1 is connected to the input of the integrator 4, the output of which is connected to the indicator 3, for example

84,

oscilloscope, and through the low-pass filter to the control input. the initial level of the sawtooth voltage forms 3. At the same time

low pass filter 6 can be made in the form of an active filter based on an operational amplifier. The output of the pulse driver is connected to the input of the delay element 7, which is an equivalent of a long line, and to the input of a frequency divider 8, for example, a blocking generator. The output of the delay element 7 is connected to the start input of the rapper 3 of the sawtooth voltage, and the output of the frequency divider 8 is connected to the input of the zero setting of the integrator.

The proposed device for measuring the fluctuations of the phase of the pulsed si | -

Nala works as follows.

The signal under study is fed to the shaper 2 pulses, from the output of which is fed to one of the inputs of the phase discriminator 1 and through

the delay element 7 at the start input of the shaper 3 sawtooth voltage. The delay time of the sig.pa by delay element 7 must satisfy the relation

(XKoU l - o HVo, Kcl.

where f-j is the time delay of the signal;

TQ - the nominal value of the period

signal;

 MciKc is the maximal value of oscillations of the period of the signal under study.

The sawtooth voltage from the shaper 3 sawtooth voltage is supplied to the second input of the phase discriminator 1. The initial (upper) level of the sawtooth voltage is regulated by a signal fed to the control input of the shaper 3 through a feedback circuit from the output of the 6 low frequency filter. The phase discriminator 1 forms a voltage proportional to the fluctuations of the period (but not the phase) of the signal under study. The integrator, during a fixed time interval determined by the signal period at the input of the zero setup, performs an integration operation over the time of the input signal and generates a voltage proportional to the fluctuations of the phase of the signal under study. This voltage is applied to indicator 5 and to the feedback circuit. The feedback action excludes from the output signal of the phase discriminator 1 the constant component, which would lead to the saturation of the integrator C, as well as the low frequency components lying in the transparency band of the low pass filter 6. Setting the integrator C to zero is produced by a signal arriving at the input of the setting zero from the splitter 8 frequency. The frequency division factor is determined from the ratio.

where 1 "is the frequency division factor; i Tint required time and haste

neither

The notation in FIG. 2: 9 and 10 voltage diagrams at the outputs of the driver 2 pulses and element 7

delays accordingly; 11 is a voltage diagram at the output of the sawtooth voltage generator 3 (when using a dashed line, the initial (upper) level of the sawtooth voltage is affected by the feedback signal J; 12 is the voltage diagram at the output of the phase discriminator 1; 13 voltage diagram at the input of the integrator zero setup; And is the integrator output voltage diagram.

The accuracy of measuring phase fluctuations by the proposed device in the specified frequency range is 5-10. The increase in accuracy is due to the fact that the measurement error of the proposed device is frequency independent. Therefore, in its resulting error, there is no component due to the frequency dependence of the phase fluctuations on the spectrum.

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Claims (1)

DEVICE FOR MEASURING PULSE SIGNAL PHASE FLUCTUATIONS, comprising a phase discriminator connected, by inputs to a pulse shaper and sawtooth voltage shaper, a low-pass filter and an indicator, characterized in that, in order to increase accuracy, a delay element, an integrator and a divider are introduced into it frequency, while the delay element is connected between the output of the pulse shaper and the start input of the ramp of the sawtooth voltage, the output of the phase discriminator is connected to the integrator input, the output is It is connected to the indicator and through a low-pass filter to the control input of the sawtooth voltage driver, the input of the frequency divider is connected to the output of the delay element, and the output to the zero input of the integrator. , .., 1019358 figure 1