SU429369A1 - METHOD FOR DETERMINING THE MOMENT OF EQUALITY OF ROCKING FREQUENCY TO THE SPECIFIED VALUE - Google Patents

Description

one

The invention relates to radio measurements and can be used to obtain frequency labels in devices with a sweeping frequency.

The known methods for determining the moment of equality of the oscillating frequency to a given value are based on separating the zero beat region from the signal obtained by mixing the signals of the reference and oscillating frequencies.

The proposed method is characterized in that the signal at the mixer output is differentiated, pulses are generated when the differentiated signal is equal to zero, and a pulse is selected that does not coincide in time with the pulses generated at the time of equalization of the signal obtained by a 90 ° offset of the original signal at the mixer output, whose position in time corresponds to the moment when the oscillating frequency is equal to the specified value.

This allows increasing the accuracy of determining the moment of equality of the oscillating frequency to the specified value.

Let it be necessary to determine the moment when

F (f} F ,,

where F (t) is oscillating with the input sweep frequency;

FO reference frequency at the mixer input.

The phases of the input oscillations will be respectively equal

(4 J27rj / (0, fl (+ cp,

where f () is the phase of the signal with a swinging frequency;

F1 - the initial phase of the signal with a shaking frequency

That + Tr.

where fo is the phase of the reference frequency signal;

F2 is the initial phase of the reference frequency signal.

At the output of the mixer get the signal type

e (0,

20 where Uc (t) is the instantaneous value of the voltage at the mixer output; and c is the voltage amplitude at the mixer output

25 - T (O -

Substituting the values (f (t) and pho, get:

and, (I) g / c cos 2 IF (t) dt - 2r.F, t + cp ,, 30 where sr cpi - cpj. Differentiating the expression for L / dt in time, get - - and sin 2ir JF (f) dt - .t + 9., X dt (/). (1) Derivative does vanish when sin 2 тт j () dt - - P, t + cp O, f () Fo 0. The phase shift of the signal is t / c (0 -, half i /; (/); 7eCOs 2T: J / (y ± f / cSin 2uJ / (Ocf -2i: Fo + p ,. (2) where Uc (t) is the instantaneous value of the voltage of a signal whose phase is shifted by - relative to the phase of the signal Uc (t). The expression for Uc (t) vanishes when sin 2a IF (t) dt - 2-F, f + cp 0. Comparing the set of roots of equation (1) with the set of roots of equation (2), it can be noted that they are different by the root of equation (1), determined by the equality of the reference and the Thus, if pulses are formed at the moments when the signal is equal to zero, then a pulse can be distinguished from them that coincides in time with the moment that the oscillating frequency F (t) is equal to the specified value FO by the difference between the pulses formed Uc (t}. The drawing shows a block diagram of a device that implements the proposed method. It contains mixer 1, differentiating device 2, amplifier 3, null indicator 4, prohibition scheme 5, phase shifter 6, mixer 7, amplifier 8 and null indicator 9. Signals from the oscillating F (t) and reference FQ frequencies arrive at the input of the mixer 1, which converts them into a signal of the form. The converted signal is fed to the input of a differentiating device 2, where differentiation occurs. The differentiated signal is amplified by amplifier 3 and is fed to the input of a zero-indicator 4, which generates pulses at times when the differentiated signal is zero. The pulse sequence from the output of the null indicator 4 is fed to the signal input of the inhibitor circuit 5. At the same time, the signal with the oscillation frequency F (t) and the reference frequency signal FO, previously shifted by the phase shifter 6 by 90 °, are fed to the mixer 7 output, which converts these signals in the signal of the form Uc (t). The converted signal is amplified by amplifier 8 and is fed to the input of a null indicator 9, which generates pulses at the moments when the signal Uc (t) is zero. The pulses from the output of the null indicator 9 are fed to the prohibiting input of the prohibition circuit 5 and "prohibit pulses coinciding with them in time to the signal input of the prohibition circuit 5. At the output of circuit 5, the pulse coincides in time with the moment of equality of the swinging frequency F ( t} to a given value of f °. Item of the Invention A method for determining the moment of equality of the oscillating frequency to a given value, based on obtaining "zero beats by shifting the signals of the oscillating and reference frequencies, characterized in that To determine the moment of equality of the oscillating frequency to a given value, the signal at the mixer output is differentiated, pulses are generated; moments of equality of zero differentiated signal; and a pulse is selected that does not coincide with the pulses generated at the moments when the signal, equal to zero, is shifted by 90 °. the output of the mixer, the position of which in time corresponds to the moment of equality of the oscillating frequency to the specified value.