SU547704A1 - Method and device for measuring frequency deviations from nominal value - Google Patents

Description

(54) METHOD AND APPARATUS FOR MEASURING FREQUENCY DEVIATION FROM NOMINAL VALUE apparatus for performing the method is provided with a reversible counter .kotorogo summing input coupled to the pulse shaper, and subtracting i - with the reference frequency generator, potentially pulse decoder state zero down counter, switching the input of which is connected to the generator of the reference frequency, and the output from the installation of the reversible counter in the (N-1) state, the potential-pulse decoder (Ml) of the reverse state a pulse counter, the pulse input of which is connected to the driver, and the output is connected to the bus of the reverse counter installation to the zero state, to which the output of the control unit is connected, and the output potential-pulse decoder, the pulse input of which is connected to another output of the control unit, and potential inputs All decoders are connected to the output of 1Ш1М tires of the reversible counter. Figures 1 and 2 show diagrams of a device that implements a method; in fig. 3-6 are timing diagrams explaining the measurement method. The essence of the method is as follows. The reverse summation (comparison) of the input measured and exemplary fo frequencies is performed modulo N (modN), and N is determined from the ratio of the nominal values of measured frequencies fni and the length of the message: .HOA ((fHrfoTcJ), where GCD is the most common common divisor ; foTC4.- value of the reference frequency. At a constant spacing Afp of the nominal values of measured frequencies, the reference frequency should be chosen from the following range f - fi (RMS HI th tp 5 where K 0,1,2 ...; fH, - the minimum value of the measured frequency in the set fn I. In this case, the reference frequency is equal to one Of the nominal frequencies fni or differs from the extreme frequencies, by an amount that is a short of the separation Afp. The latter circumstance expands the choice of the model frequency fo, since the proposed measurement method must be equal to O COUNT To reduce the number of full counting cycles modulo N in reverse counting requires a reference frequency to choose in the middle of a set of m measured frequencies, i.e., for odd m ° Hp ,, for even m о sampling m / ,, /, When the last conditions are met, the IOD value; equal to the frequency pa3HocaAfp: - GCD (fiii-foTcj), and the comparison module N Afp to. In FIG. Figures 3-6 are a graphical representation of the change in the state of the counter at various ratios of measurements efy.x of frequencies fx- and reference frequency fg. FIG. Figure 3 shows the change in the state of the counter when choosing fo equal to one of the nominal measured frequencies fH, and arriving at the input of the counter frequency fx-fn- + Afx. The operation of the counter in this case does not differ from the operation of a conventional reversible counter, and the counting of impulses is carried out both as a decrease (with Afx 0) and with an increasing result (with Afx 0). FIG. Figure 4 shows the change in state of the counter modulo N with fx- ,, f ,, ± Afp ± Afx fg, FIG. 5 - at f X. f o fp fx fo of FIG. 6 - at, - fo + 2Afp ± Afx fo. If at the end of the unit with a duration to the resultant number in the counter is equal to O or N, then the values of the measured frequencies are equal to the nominal values (graphs D). If the result of the reversible sum modulo N lies in the interval from O to N / 2, then the measured frequency fx is greater than its nominal value (graphs E), and if the result is in the range from N / 2 to N-1, then f (graphs D). Indeed, the number n in the adder (counter) modulo N, accumulated during the time to, is equal to n mod (fo) to. Opening the modulo operation of modulo N, we obtain {n ± Afxto, the remainder of the division (fv; fp) tf, by N; Afx the deviation of the measured frequency from the nominal value. In a reverse counter counting pulses ranging from O to N, negative residues -p} take the values {-n} -Nn In this case, the value of the frequency deviation from the nominal (-Afx) can be read using a decoder from the counter in the reverse code : N- {-n} NN-1-n p Thus, the value of the resulting number n, read from the counter at the end of the time interval to, will be H. . proportional directly to the absolute deviation of the frequency from the minimum value of Afx, and not to the relative deviation of Afx / fx. In the proposed method, the range of measured frequencies is one order from fo. The upper value of fo, and hence fx, is limited only by the speed of the counter. Since the resulting value in the counter npHfx fH, Afx 0 -n 0; N at fx fH, Afx 0 n 0- | pu fx fo, Afx 0 -n - | -Nl, O for a one-to-one reference, the deviation of the frequency should not exceed M / 2, in terms of the dololisimu frequency d .. f /, | - a

where Afp is the frequency spacing of the nominal measured frequencies.

In multi-frequency communication systems, the change in frequencies Afxj, called destabilizing factors and the Doppler effect, is almost constant at all m frequencies. In this case, the remainder n calculated by the modulo-N counter will be the same for the entire set of measured frequencies.

The proposed method can be implemented using a device (see Figs. 1 and 2), which includes a pulse shaper 1, an oscillator of exemplary frequency 2, a reversible counter 3, a control unit 4, a potential-pulse decipher 5 zero-state reversible counter , potential impulse descrambler 6.) state of the reversible counter and output potential impulse descrambler 7.

Consider the work of the reversible counter 3 modulo N.

Pulse are added to the output of the reversing counter 3 for addition and subtraction. The number of bits of the reversible counter 3 n is chosen such that the volume of this counter is not less than N. i.e. 2 N

The decoder 5 is constructed so that a pulse at its output appears when the reversible counter 3 is in the (N-1) state and the input pulse has set it to the state.

Thus, if the input of the reversible counter 3 receives impulses for subtraction, the counter is transferred to the (N-1) state by a pulse from the decoder 5, and then the state passes from (N-1).

The summing input of the reverse counter receives a sequence of pulses of the input frequency fx, obtained in the driver of pulses 1. The subtractive input receives a sequence of pulses of the model frequency fo from the generator 2.

During the time t0 in the reversible counter 3, the input and reference frequency pulses are counted, and the calculation is performed modulo. The state of the reversible counter at the end of the time interval fo is determined using a potential-pulse decoder 7, at the input of which the pulses are received from the control unit 4, which follow with a period to. According to the number of the WRINKER of the decoder 7, on which the

pulse, the magnitude and sign of the frequency deviation from the nominal value is determined.

The control unit 4 synchronizes j the operation of the reversible counter with pulses following with a period of to the formula of the invention

1. A method of measuring the frequency deviation from the nominal value, based on counting and comparing the number of periods of exemplary and measurable frequencies, characterized in that, in order to improve the accuracy, the duration of the multi-frequency signal is measured, the difference between the nominal frequencies in the parcel is determined , reversive counting of the number of pulses of a multifrequency package modulo, proportional to the product of the difference between the nominal values of frequencies in the package and the duration of the package with increasing and decreasing frequency signal from the nominal value recorded in the meter.

2. A device for carrying out the method according to Claim 1, characterized in that it is equipped with a reversible counter, the summing input of which is connected to a pulse shaper, and the subtracting one - with an exemplary frequency generator, a potential pulsed zero-state reversing counter, the pulse input of which is connected with the generator of the reference frequency, and the output with the bus of the installation of the reversible counter in the (N-1) state, the potential impulse descrambler (N-1) of the state of the reversible counter, the pulse input of which is connected with the driver, and the output with the bus of the reversible counter installation in the control state, to which the output of the control unit is connected, and the output potential-pulse decoder, the pulse input of which is connected to another output of the control unit, and the potential inputs of all the decoders are connected to the output one us reversible counter.

Sources of information taken into account in the examination:

1. Ermolov R.S. Digital frequency meters, M., Energii M973., P. 23-26.

2. Author's certificate No. 336612, M.C.C. G01 R 23/10, 1973 (prototype).

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