SU750393A1 - Modulation depth measuring method - Google Patents

Description

This invention relates to electrical measuring technology. Methods are known for measuring the modulation depth based on measuring the minimum and maximum values of the amplitude-modulated signal l. These methods have low measurement accuracy and limited lower limits of measurement in terms of frequency and modulation depth. Methods are known for measuring the modulation depth, based on measuring instantaneous values of the amplitude modulated signal. The purpose of the invention is to improve the measurement accuracy and expand the dynamic range of the meter. This is achieved by the fact that in the method of measuring the modulation depth, based on determining the instantaneous values of the amplitude modulated signal, the voltage of the frequency limit is limited to certain calibrated levels given by the code fsj-, the number of amplitudes exceeding carrier frequency over each level from: from the first level (P one excess to the H level with the number of exceedances equal to the multiplicity n of the carrier and modulating frequencies, alternately There is a difference number of elevations o, between each two adjacent calibrated levels, the number of elevations n is found, and the codes Ut are the code of the average amplitude-modulated signal by the formula ... where is HO the known zero level code of the limit and the depth up and down according to the formulas N „„ - N "0,. He ,, CP" CP g NNS S ya - discreteness of determining the depth of modulation.

 FIG. 1 shows time diagrams, according to the method; in fig. 2 structural electrical circuit of the device for its implementation.

Let the modulation of the voltage U y – t of the carrier frequency be carried out by the non-sinusoidal voltage U (t) (see Fig. La

Coe (1 modulation depth factors, up U and down U, are determined by the formulas

and, and

and

Umh and-and

MB

, /

. -n (2)

iT

and

U is the maximum positive and negative value of the modulating stress; LST is the maximum and minimum amplitude modulated voltage; and - the average value of the amplitude of the modal bottom of the laser voltage or the voltage of the carrier frequency in the absence of modulating voltage. The minimum and maximum values of the amplitude-modulated voltage are determined in the following way, the Amplitude-modulated signal is limited to the calibrated voltage of certain levels, and the number of amplitudes of the carrier frequency above these levels is calculated. The instantaneous values of the amplitude-modulated signal are obtained from the difference in the number of amplitudes exceeding the voltage of the carrier frequency over the two adjacent levels of limitation. In this case, the instants of the appearance of the first pulse and the maximum number of pulses correspond to the levels of limitation equal to the maximum and minimum values of the amplitude-modulated signal with discretization error. These levels of limitation, as well as the number of excesses exceeded for each of them, are used to calculate the average value of the amplitude modulated signal. The essence of measuring the average value of an amplitude modulated signal is reduced to the trace of who he is. In the course of counting the number of elevations of the modulated modulated signal above each level of limitation alternately

determine the difference in the number of exceedances of the amplitude-modulated signal between the two nearest levels.

Assume n, - difference value

exceedances between calibrated levels

,)

no restrictions

AND

Ki

for the period of the modulating signal. Not- . It is difficult to guess that the code of the average value of the amplitude-modulated signal is

e

n-h

S.

t i i “a

)

Claims (2)

n where NO is the known code of the zero limitation level} I is the code of the limitation levels from the first excess to the maximum number of exceedances, i 1.2 ,,., From formula (3) it follows that the definition of the average value of the amplitude-modulated signal in this method limits an amplitude-modulated signal at certain calibrated levels; V calculate the number of excess amplitudes of the carrier voltage above each calibrated level; determine the difference number of elevations P. between two adjacent calibrated levels U, by the formula (3), the code of the mean value K | p is calculated. Dividing by n is not difficult, since n is a constant coefficient. The mean code value Tss.r and the codes of maximum and minimum values max MMVI, respectively, calculate the modulation depth upwards and the software using the formulas J, C СР.-СД, and ЦСР where cJ, is the resolution determination of the depth of modulation. The device consists of a comparing unit 1, a control unit 2, a calibrator voltage generator 3 and an arithmetic unit 4. The amplitude-modulated signal and (t) (see FIG. 1 a) is fed to one input of the comparison unit 1 and the control unit 2. The other input of the comparing unit 1 receives the signal J from the shaper 3 of a calibrated voltage which is advisable to build on the principle of code-to-analog conversion. By comparing with block 1, pulses are formed at the moments when the amplitude of the voltage of the carrier frequency is exceeded above the calibrated voltage level. These pulses go to control unit 2, which counts the pulses during the period of the modulated signal and synchronizes the operation of the device. The signal from the control unit 2 pho | World 3 sets the first (maximum) level and calibrated voltage. In this case, the comparing unit 1 does not generate an excess pulse, and the control unit 2 sets the next (lower) level of the calibrated voltage. This continues until the first pulse is output at the comparative block 1 (see Fig. 1b). At this moment, the calibrated voltage code corresponding to the level from the driver 3 is transferred to arithmetic 4. Subsequently, the following levels of the calibrated voltage are formed and the number of pulses Γ enters the control unit 2 from the comparison of the vacuum block 1; (see Fig. 1c) The change in the level of the calibrated voltage continues until the number of pulses MSks arrives at the control unit 2, this time the code of the calibrated voltage corresponding to the level J is transferred to the arithmetic unit 4, where the code proportional to the average value of the voltage is also recorded. In the arithmetic unit 4, the modulation depth coefficients are calculated using formulas (1) and (2). The invention The method of measuring the modulation depth, based on the determination of instantaneous values of the 1st amplitude-modulated signal, characterized in that, in order to improve the measurement accuracy and the wider dynamic range of the meter, the carrier voltage is limited at certain calibrated levels, set by N | , For the period of the modulating signal, the number of excess of the amplitude of the voltage of the carrier frequency above each level of limitation — from the first level max P one elevation to C gx H level, is calculated, and the number of exceedances equal to the multiplicity n of the carrier and modulating frequencies is alternately determined ; between each two nearby calibrated levels, by the number of exceedances n and the codes M, the code of the mean value of the amplitude-modulated signal over is found. formula in, H. , L rde N, is the known code of the zero limitation level and the modulation depth up and down according to the formulas, n max where (51, is the discreteness of determining the modulation depth. Sources of information taken into account in the examination 1. Valitov R.A. Radio engineering measurements, 1963, pp. 95, 2. Mirsky G. Ya. Radioelectronic Changes, Moscow, Energie, 1969, p. 157.