SU991321A2 - Frequency deviation digital meter - Google Patents

Description

(54) DIGITAL MEASUREMENT DEVICE OF FREQUENCY

The invention relates to a measurement technique and is intended for use in radio engineering installations for various purposes.

According to the main auth. No. 898338 is known a digital frequency deviation meter comprising a serially connected driver, a delay unit, a memory unit, an analog-digital converter, an analysis unit, an arithmetic unit and an indicator, with the input of the pulse shaper connected to the second input of the memory unit ClJ,

However, in the study of FM signals, in particular when monitoring and adjusting the paths of the sensors, the known device does not provide information about the magnitude of the nonlinear distortion of the modulating oscillation.

The purpose of the invention is to enhance the functionality of the frequency deviation meter by enabling the amplitudes of the harmonics of the modulating oscillation of the studied FM signal to be measured using a digital frequency deviation meter.

This goal is achieved by the fact that the digital meter frequency deviation.

containing in series The formators, delay unit, memory unit, analog-to-digital converter, analysis unit, arithmetic unit and indicator, the input of the pulse generator, are connected to the second input of the memory unit, a memory unit is inserted, the input of which is connected to the analog-digital output the transducer and the output of the additional memory block are connected to the second input of the arithmetic unit .;

The drawing shows a block diagram of a digital meter deviasht.

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The device contains a shaper 1, a delay unit 2, a block, 3 memories, an analog-digital converter (ADC) 4, an analysis block 5, an arithmetic ok b, an indicator 7, a memory block 8.

2Q

The device works as follows.

Based on the Kotelnikov theorem, it can be concluded that for harmonic analysis of η harmonics of a periodic function, which has the fundamental frequency fp, it is sufficient to take 2n samples on the function period at equal intervals of 4-t-t.

Claims (1)

InSf at the moments of time corresponding to the expression where, 1,2, ..., 2n-1 is the sample number. Using these samples, it is easy to calculate the amplitude and phase of the harmonic components of the oscillations through Fourier coefficients: n 9 f. where a, and bn are the Fourier coefficients. In this digital frequency deviation meter, the law of variation of the instantaneous values of the levels (samples) of the investigated signal corresponds to the law of variation of its frequency. The values of the samples for the modulating oscillation period from the output of the analog-to-digital converter 4 are received in the second memory block 8. At the same time, either their hardware or a program of time fixes their temporary location. It is obvious that the intervals between samples are not equal. From the array of samples stored; in the second memory block 8, selected and fed to an arithmetic block; 6 those samples, which in their temporal position are necessary for harmonic analysis, i.e. (1) If the required sample does not exist, then its value is calculated by the method of linear | g interpolation, using the value of the adjacent samples. When measuring the frequency deviation, the second memory block 8 does not participate in the operation of the device. In practice, the analysis of the signal quality allows us to know the levels of no more than 5 harmonic components, so for the period of the fundamental frequency, it is enough to take samples at times where. Obviously, the calculation error is smaller, the stronger the inequality fnp fo. where ff, - is the intermediate frequency of the modulated oscillation; fj, is the fundamental frequency of the modulating oscillation. Calculations show that with fPR 10fo, the measurement error due to the inaccuracy of the mathematical apparatus does not exceed 0.1%. The advent of single-chip microcomputers makes it easy to implement the required arithmetic unit. Without any changes, this device can be used to measure the harmonic components of the AM envelope. The application of the proposed multi-functional measuring device will allow to reduce the size of the calibration complexes of transceiver equipment, simplify and speed up the verification process while maintaining the accuracy of measurement. The invention is a digital frequency deviation meter for auth.St. No. 898338, which is based on the fact that, with the aim of expanding the functionality by providing the ability to measure the amplitudes of the harmonics of the modulating oscillator, a memory block is additionally introduced in it, the input of which is connected to the output of the analog-digital converter, and the output of the additional memory block is connected to the second input of the arithmetic unit. Sources of information taken into account in the examination I. USSR author's certificate №898338, cl. G 01 R 23/00, 11.11.79.