SU1195270A1 - Method of digital measuring of time relationship of reference oscillator frequency - Google Patents

Abstract

The invention relates to a radio metering technique and can be used to dynamically measure the frequency of reference radio frequency generators. The purpose of the invention is to reduce the dynamic measurement error. POS. The goal is achieved by measuring additionally in a second sequence of time intervals. The method is implemented in a device containing the reference generator 1 under test, controlled switches of the first 2 and second 3 measuring channels, control unit 4 of digital frequency meters 5.1, 5.2.-. .5.p First and 6.1, 6.2 ... 6p of the second measuring channels, digital multipliers 7 and 8, cytf mater 9, digital multiplication unit 10, the output of which is the output S of the device, digital delay unit 11 and adders 12 and 13. The operation of the device (LA is given in temporary diagrams.: CZ grams in the description of the invention. 2 il ..; about the joint venture ND sj

Description

The invention relates to a radio metering technique and can be used for dynamic frequency measurements of reference radio frequency generators. The purpose of the invention is to reduce the dynamic error of the measurements by taking measurements additionally in the second sequence of time intervals. FIG. 1 shows a simplified diagram, explaining the measurements carried out using the proposed method; in fig. 2 - timing diagrams explaining the method. The scheme contains the reference generator 1 under study, controllable switches of the first 2 and second 3 measuring channels, control unit 4 of digital frequency meters 5.1, 5.2 ... 5.P first and 6.1, 6.2, 6p of the second measuring channels, digital multipliers 7 and 8, the adder 9 and the block) of the diffraction multiplication 10, the output of which is the output of the device, the digital delay unit 11 and the adders 12 and 13. The output of the generator 1 is connected to the inputs of the switches 2 and 3, the control inputs of which are connected to the outputs of the block 4, and outputs through frequency meters 5 and 6 and adders 12 and 13 are connected the first channel of the connections in series with the unit 11 and the multiplier 7 by the second - to a multiplier 8 and an adder 9, a second input of which .soedinen yield multiplier 7, and output via a multiplier 10 - with vyhodnoyshinoy meter. The method is carried out as follows. The signal of the reference oscillator under study with the current frequency f (t) is simultaneously applied to the switch. 2 and 3 of the first and second measuring channels, controlled by the control unit 4. Using these switches, periodically, at a constant time interval of dG, the measured frequency f (t) is applied to the inputs of digital frequency meters 5 .. - 5. P of the first measuring channel and 6.1 - 6.P of the second measuring channel. This forms the first and second periodic sequences of measuring time intervals. All the frequency meters of the first measuring channel are averaged by the measured 0 2 frequency and a digital count is made of the number of periods of the measured signal over a fixed time. The whole frequency interval of the second measuring channel measures the average of the measured frequency and the digital count of the number of periods of the measuring signal on over a fixed time interval of 2 i - LT. In this case, in the summator of the first measuring channel, a discrete sequence f (t) dt of N (ti) digital values with a period T is formed, and in the adder 13 of the second measuring channel, a discrete sequence of digital values N, (tp - f (t) dt with a period of which the time averaging interval of the measured frequency of the first measuring channel is set (based on the permissible value of the basic conversion error, the frequency is a digital value} taking into account the exact correction of the measured frequency generated in all frequency meters of the channels by analog method with subsequent analog-digital conversion and summation of the result of the digital count of the number of periods of the measured frequency, during the time interval with the digital value of the exact correction. From the output of the adder 12 of the first measuring channel a discrete sequence of digital values with a period T. 11 is delayed by 4f and the output digital sequence in multiplier 7 is multiplied by a constant coefficient equal to 1. From the output of the adder 13 of the second measuring channel di A discrete sequence of digital values with a period and in multiplier 8 is multiplied by a constant coefficient K, the value of which is set according to condition K and the output digital sequences of the first Measuring channel and the second measuring channel are summed in adder 9, and the resulting total sequence of output digital values in multiplier 10 multiply by a constant coefficient K, the value of which is established by the condition Kj T | . At the output of the circuit, a periodic sequence of digital output values is obtained.

M (t,) - f (t ,.). ..

With a jump-like change (Fig. 2) of the measured frequency from d to f + 4 f after a constant time interval, the duration of the output of the first measuring channel is a periodic digital sequence MXt) —the transient response of the first measuring channel and the periodic digital sequence Mg ( t) - temporary transient response of the second measuring channel. In FIG. Figure 2 also shows the corresponding output digital sequences Mj-Ct), liUt at the outputs of adders 12 and 13, and the output digital sequence MK; (t) is the transition characteristic of block 10, which is the output of the circuit, with m / -e.

From the transient characteristic M.jj (t (Fig. 2), it follows that the rotational average fj interval obtained by the proposed method, with an abrupt change in the measured frequency, is much smaller than the temporal averaging interval f of the transient response Mr (t) of the first measurement channel. , the dynamic error of frequency measurement in the proposed method is reduced in

 A times, but no less than an order of magnitude.

Example. The time dependence of the frequency of the reference oscillator 41-53 is measured. Two measurement channels are created with four digital frequency meters 43-54, with attachments for introducing an accurate correction, the measured frequency generated by the analog integrator and the A / D converter, each. The time intervals of the digital frequency counter of the first measuring channel are set to 1 s, according to the technical characteristics of the measuring instruments. The time averaging intervals of the digital frequency meters of the second measuring channel are set to

2 1, 1s, i.e. & t 0.1s more than in digital frequency meters of the first measuring channel. A digital time delay of 0.1 s is used, and the measurement of the co. According to the formula of the invention, I get that the dynamic error of frequency measurement in the proposed method

decreases in --111 - Q

time. it

Ls n.-f.-fft3

0.1-10

for the first time, it was possible to measure the time dependence of the frequency with a fluctuation period of 0.2 s or less.

Thus, in comparison with the prototype, the proposed method provides a reduction in the dynamic error by no less than an order of magnitude.

Claims (1)

Invention Formula The method of digital measurement of the time dependence of the frequency of the reference generator, based on the formation of the first periodic sequence of measuring time intervals shifted relative to each other by a constant value, and counting the number of periods of the measured signal during each measuring interval of the first sequence. Characterized in that, in order to reduce the dynamic measurement error, a second periodic sequence of measuring time intervals is additionally formed, the number of periods of the measured signal is counted during each measuring interval of the second sequence, the first periodic sequence is shifted relative to the second, and the time dependence of the measured frequency is determined according to the formula M (t.) (T.) - K, N (t.), e M (t.) is a sequence of numbers proportional to the instantaneous values of the measured frequency at discrete instants of time t., where i О, 1, 2, ...;  Gg / Kjt; / lG constant coefficients; t - the duration of the measuring time intervals 51195270 the first sequence, (G "S - the time shift between intervals of the first sequence; 5 duration of measuring time intervals of the second sequence; DT is the time shift between tO first and second sequences;  N (t) is the number of periods of the measured signal in the i-M measuring inter- i time interval of the first periodic sequence; Ct;) the number of periods of the measured signal in the i-th measuring time interval of the second periodic sequence; . start time t. i-ro measuring time interval of the first and second periodic sequences.