SU1323976A2 - Device for measuring frequency deviation - Google Patents

Abstract

The invention relates to the technique of electrical measurements and is intended to measure the frequency deviation of signals with an arbitrary modulation law, is an additional invention to the authors. St. No. 1288609. The purpose of the invention is to improve the accuracy of measurement while expanding the operating frequency range of the device. To achieve this goal, two adjustable attenuators 8 and 9, two amplitude detectors 10 and 11 are introduced into the device. Subtraction unit 12 and second filter 13. The device also contains a phase discrimination unit 1, a voltage amplitude maximum amplification unit 2, filter 3, circuit 4 division, frequency deviation indicator 5, delay line 6 and phase divider 7. In the whole operating range of input frequencies, the device maintains the equality of the input voltages of the block I phase discrimination. This eliminates the displacement of the centers of the discriminative characteristic of the device relative to the zero level and greatly expands its working range. 3 il. with to with with about figure 1 Go

Description

The invention relates to electrical measuring and is intended to measure the frequency deviation of signals with an arbitrary modulation law.

The purpose of the invention is to improve the measurement accuracy while simultaneously expanding the operating frequency range of the device by stabilizing the centers of the linear working sections of the detector characteristic of the device relative to the zero line, which is carried out over a wide range of input frequencies.

FIG. 1 shows a functional block diagram of the proposed device; in fig. 2 and 3 are the stress plots showing his work.

The device contains a phase discrimination unit, a voltage sweep separation unit 2, a filter 3, a dividing circuit 4, a deviation indicator 5 whose input is connected to the output of dividing circuit 4, the first input of which is connected to the output of the voltage sweeping 2 unit, and its second input - with the output of the filter 3, the first and second outputs of the phase discrimination unit 1 being connected respectively to the input of the voltage separation unit 2 and the input of the filter 3.

In addition, the device contains a delay line 6, a phase shifter 7, adjustable a.ttenuators 8 and 9, amplitude detectors 10 and 11, a subtraction unit 12, and a second filter 13, the output of which is connected to the control inputs of the first 8 and second 9 adjustable attenuators, outputs which are connected respectively to the input of the delay line 6 and the input of the phase shifter 7. The output of the delay line 6 is connected to the input of the first amplitude detector 10, and the output of the phase shifter 7 to the input of the second amplitude detector 11. The outputs of the first K) and second 11 amplitude detectors Connected respectively to the first and second inputs of subtraction unit 12, the output of which is connected to the input E of the third filter 13. Informational BXOZIBI adjustable attenuators 8 and 9 are connected to the input of the device, and the outputs of delay line 6 and phase shifter 7 are connected respectively to the first and second inputs of unit 1 phase discrimination.

The device works as follows.

Let a signal be sent to the input of the device, the voltage of which

 A-sin wl.

Then at the output of line 6, the delay voltage and.

Ur And sin w (t - t), where t - signal delay time line 6

delays.

Suppose that the phase shift, vsssimy adjustable adjustable phase shifter 7, is zero. Then on the first and second outputs of block 1 phase discrimination 1: signals, the signals have the form:

(I cosf

. Ojt

sm -2

PC

C, A (I cos I -1sin (FROM

From FIG. 2i that the voltage Ui (w) at the first output of phase discrimination unit 1 is dependent on the frequency of the input signal, which consists of periodically repetitive linear sections, the frequency difference between two adjacent humps Ao) being determined only by the time delay of the signal line 6 delays, namely

And with

Jl t

five

0

five

P

five

0

five

0

five

FIG. 26 shows the voltage at the second output of phase discrimination unit 1. Near the transition points Ui ((o) through the zero level, the voltage Us is almost constant, gf

and.

From the above relations it follows that the steepness of the detector characteristic of the device (more precisely, the phase discrimination unit) is equal to

S 2Ak / AU /,

where k 1,1 is the correction factor that takes into account nonlinearities that occur for the dependence Ui (w).

The last relation accurately determines the steepness of the detector characteristic 01 (w) at the points of its passage through the zero level.

If a FM signal is sent to the device input, the carrier frequency of which is m-, and the deviation is equal to Dso-, then the device processes it as follows.

By means of an adjustable phase shifter 7, the dependence of h (co) and Uz (w) is shifted to coincide with one of the closest points of the transition of characteristics through the pu, g (Z level), which is shown by the dotted line in Fig. 2a, b. The fine tuning moment is determined equalizing the constant component of the voltage at the first output of the phase discrimination unit 1. The voltage sweep unit 2 eliminates the constant component of the voltage (in the presence of residual detuning) and highlights the range of this voltage

and, where C 2A-k-T / n is a constant coefficient.

Thus, the voltage at the output of dividing circuit 4 is directly proportional to the frequency deviation of the input signal, and the proportionality coefficient is determined by the value of m delay of the signal in delay line 6.

The signal from the output of dividing circuit 4 is fed directly to the input of a frequency deviation indicator, which is calibrated in the corresponding units of measurement.

Attenuators 8 and 9, the detectors 10 and 11, the subtraction unit 12 and the second filter 13 are designed to eliminate the error of the output of the delay line 6 and the output of the phase shifter 7 by the constant component of the voltage of these signals. This is done as follows.

The signals from the outputs of the delay line 6 and the phase shifter 7 after amplitude detection, respectively, in the detectors 10

which eliminates the need for using special calibration tools when using sufficiently stable delay lines. The use of delay line 6, phase shifter 7, attenuators 8 and 9, allows to obtain a flawed range of operating frequencies. In addition, the device has increased accuracy, as the signal levels at the inputs of block 1 phase discrimination stabilized.

Claims (1)

and 11 are fed to the inputs of subtraction unit 12. The presence of the indicated stabilization of levels In the presence of a mismatch of these signals, the signals also makes it cheaper to reduce the filter 13 which allocates a constant component of the device and reduces its damping of the mismatch signal the use of the line is then interchanged with the control inputs of the regulator and the phase shifter with higher attenuators 8 and 9. In the corresponding losses and a more stable relationship with the mismatch value of the transfer ratio on the frequency of transmission, the transmission coefficients of the signal regulating through them, attenuators, and so that the magnitude of the error should tend to zero. Formula of the Invention The dependence of the coefficients ne-Device for measuring the deviation of the frequency from the control direction is required (for example, –20 you, according to Aut. St. No. 1288609, different from the mismatch) is presented here, so that, in order to improve the accuracy of iz FIG. 3. Thus, throughout the working diameters and expansion of the working range of the input frequencies, pa-frequencies are supported, two controlled veins of the input voltages of the block I phase-attenuator, two amplitude detectors, discrimination are introduced, which eliminates the offset of the subtraction block. and the second filter, the output of the discriminatory (detector) centers 25 of which is connected to the control inputs of the device characteristic with respect to the n-adjustable attenuators, the outputs of which level due to the predominant increase in sweat p r in the delay line compared to losses in the regulated connected to the input of the delay line and the input of the phase shifter, with the output of the delay line connected the phase shifter, which takes place with increasing, to the input of the first .amplitude detector,  NUPLNPY IAGAGOTM R PIU / pktatr oia o ouTvrvn / 4% o-egopa in pa i / Dvrvn D-rnnnrr INPUT frequency. As a result, the working range of the device is significantly widened. The proposed device provides a measurement of the frequency deviation of FM signals with an arbitrary modulation law. The measurement result depends only on the delay time of the signal by the line 6 for the output of the phase shifter to the input of the second amplitude detector, the outputs of the first and second amplitude detectors are connected respectively to the first and second inputs of the subtractor whose output is connected to the second filter; Attenuators are connected to the input of the device. which eliminates the need for using special calibration tools when using sufficiently stable delay lines. The use of delay line 6, phase shifter 7, attenuators 8 and 9, allows to obtain a flawed range of operating frequencies. In addition, the device has increased accuracy, as the signal levels at the inputs of block 1 phase discrimination stabilized.  The presence of this stabilization of signal levels also makes it possible to reduce the cost of construction of the device and reduce its dimensions by using a delay line and a phase shifter with higher losses and a more stable dependence of the transmission coefficient on the frequency of the signal passing through them, - Invention formula Device for measuring the frequency deviation by aut. St. No. 1288609, characterized in that, in order to improve measurement accuracy and expand the range of operating frequencies, two adjustable attenuators, two amplitude detectors, a subtraction unit and a second filter, whose output is connected to the control inputs of adjustable attenuators, are introduced into it exits that  The presence of this stabilization of signal levels also makes it possible to reduce the cost of construction of the device and reduce its dimensions by using a delay line and a phase shifter with higher losses and a more stable dependence of the transmission coefficient on the frequency of the signal passing through them, - Invention formula Device for measuring the frequency deviation by aut. St. No. 1288609, characterized in that, in order to improve measurement accuracy and expand the range of operating frequencies, two adjustable attenuators, two amplitude detectors, a subtraction unit and a second filter, whose output is connected to the control inputs of adjustable attenuators, are introduced into it exits that connected to the input of the delay line and the input of the phase shifter, with the output of the delay line connected to the input of the first .amplitude detector,  About ouTvrvn / 4% o-egopa in pa i / Dvrvn D-rnnnrr and the output of the phase shifter to the input of the second amplitude detector, the outputs of the first and second amplitude detectors are connected respectively to the first and second inputs of the subtractor, the output of which is connected to the input of the second filter, and the information inputs of the adjustable attenuators are connected to the input of the device. 3 and about fie.Z.