SU454664A1 - Frequency comparator - Google Patents

Description

one

This invention relates to a radio measuring technique.

A frequency comparator is known that contains several series-multiplied frequency multipliers, consisting respectively of a multiplier and a frequency mixer, a frequency multiplier of the first reference signal.

However, the known frequency comparator is characterized by a relatively high frequency comparison error.

The aim of the invention is to reduce the frequency comparison error.

For this, a second reference signal converter is connected to the comparator, connected to the inputs of the mixers of the frequency multiplying blocks and consisting of a series-connected multiplier, divider and frequency multiplier.

The drawing shows the block diagram of the comparator.

The frequency comparator contains blocks 1, 2 multiplying the frequency, consisting of multipliers 3, 4 and mixers 5, 6, frequency multiplier 7 of the first reference signal, frequency converter 8 of the second reference signal, consisting of multiplier 9, divider 10 and frequency multiplier 11. The comparator contains: also inputs 12-14 and output 15.

The comparator works as follows.

It is advisable to consider the operation of the comparator at specific values of the compared frequencies and multipliers.

Suppose, for example, that the frequency of the signal under study fcc / o ± Af is compared with the frequency of the reference signal MHz, close to 1 MHz. In multiplier 4, the frequency of the signal under study is multiplied 10 times, and in multiplier 7, the reference signal arriving at input 13 is multiplied in frequency by 9 times. After mixing the signals in the mixer 5, a difference frequency is formed, equal to

f, 10 (f. ± A /) - 9 / .rf, ± 10if.

After passing through one multiplication unit, the frequency difference between the reference and test signals increased 10 times. Since the output signal of block 1 is input to the subsequent block 2, after passing the signal under study successively through n blocks, the difference in the frequency of frequencies increases by a factor of 10. As a result, the output 15 of the comparator appears signal with a frequency

/ o / 0 ± 10 A /.

Due to the large frequency difference, this signal is easily investigated using an electron-counting frequency meter, an analyzer

spectrum or other measuring device (not shown).

When working with a higher reference frequency, for example / o 5 MHz, it is fed to the input of frequency converter 8. In the multiplier 9 of this converter, the frequency of 5 MHz is multiplied by 3 times, then divided by 5 times by divider 10, and finally multiplied by another 3 times by the multiplier 11. As a result, the output of the frequency converter 8 receives a signal with a frequency of 9 MHz, which is fed to the inputs of the mixers instead of the signal of the multiplier 7. Otherwise, the operation of the comparator is completely similar to working with the reference signal of 1 MHz.

If a higher frequency of the reference signal is used, it is multiplied beforehand and only then goes to the frequency divider. In this case, the phase noise of the frequency divider becomes comparable or even lower in level than the noise of the multiplied signal, therefore the effect of the divider

by comparison error and the level of phase fluctuations brought in by the comparator is markedly reduced.

Subject invention

A frequency comparator with two reference signals of multiple frequencies, containing several frequency multiplying blocks consisting of a series-connected multiplier and a frequency mixer, a frequency multiplier of the first reference signal, the output of which is connected to the inputs of the mixers, the inputs of which are also fed to a second reference signal that differs in that, in order to reduce the frequency comparison error, a frequency converter of the second reference signal is inserted in it, connected to the inputs

mixers of frequency multipliers and consisting of a series-connected multiplier, divider and frequency multiplier.

II