SU1388981A1 - Device for stabilizing mean frequency of a frequency-modulated signal - Google Patents

Abstract

This invention relates to an FM technique and increases the stability of an average frequency of an FM signal. The frequency of self-oscillations in an annular connection, formed by four mixers 7, 6, 10 and II and resonant wave 1 2,1 whose output is connected to the second input of mixer 7, during operation of the device remains constant and equal to the frequency of the stabilized auto-oscillator (SAH ) 2. The stability of forced self-oscillations will be determined mainly by the stability of the frequency of the SAG 2, which can be made of quartz. The accuracy of the FM conversion caused by the instability of the average frequency of the FM signal in the FM depends on the stability of the output oscillations, therefore it is advisable to use a controlled quartz crystal as the controlled oscillator 14. The proposed device, by no less than an order of magnitude, increases the stability of the middle part of the output FM signal. I il. e (L

Description

13

The invention relates to a frequency modulation technique and can be used to obtain a frequency-modulated (FM) signal with a highly stable average frequency from a frequency t4 modulated signal with a non-stable average; Frequency.

The goal is to increase the stability of the average frequency of the FM signal,

The drawing shows the structural diagram of the proposed device.

The device for stabilizing the mid-frequency FM signal contains the first mixer 1, the stabilized oscillator 2, the first delay line 3, the second mixer 4, the narrow band filter 5, the third, fourth and fifth mixers 6, 7 and 8, the second 9, the sixth and seventh mixers 10 and P, the resonant amplifier 12, the phase detector 13 and the controlled oscillator 14.

Device (given that all

mixers - single-sided) works as follows.

The first mixer. 1, the stabilized auto-oscillator 2, the first delay line 3 and the second mixer 4 form a device with direct deviation subtraction (LDPE), which at the input of the narrow-band filter 5 generates a signal with phase modulation and reduced deviation from the original FM signal 1a. Narrowband filter 5, tuned to the oscillation frequency. Stabilize the poipaHHoro auto oscillator 2, passes these oscillations to the output, the phase of these oscillations changes according to the law of variation (due to the instability of the carrier frequency of the FM signal. Components of the frequency spectrum of the useful message through the narrowband filter 5 pass.

The third 6, fourth 7, sixth 10 and seventh 11 mixers, the second delay line 9, the resonant amplifier 12, the phase detector 13 and the control oscillator 14 comprise an inverse converter from phase to modulation, which also restores the deviation of the spectral components that passed narrow-band filter 5. At the output of the second, p 8

0

five

0

The signal is modulated in frequency. For simplicity, let us assume that the modulation of the device is implemented by a sinusoidal current.

Ug (t) and cos (“o + bojt + + m sinnt, (1)

where Qg is the carrier frequency of the input FM

signal;

L WITH C - the instability of the carrier frequency of the input signal;

 frequency modulation index;

lso

Q

frequency deviation;

modulated frequency with ignition.

At the output of the first mixer 1, oscillations of the cumulative frequency are emitted and therefore a signal is received at the second input of the second mixer 4

UCM, U (. Cos (ОЭо + ЛСОН + COCA) t +. + M sinfzCt -t- ,,) - (Op + AcoJT ,,, +

Ch si

(2)

Where

0 „Hq.

Si

the frequency and the initial phase of oscillations of the stabilized auto-oscillator 2, respectively;

 - lag time in the first delay line 3.

At the output of the second mixer 4, oscillations of the difference frequency are distinguished.

five

0

and

cm g

.

, t + 2

ii "- it m sin ---

xcosS2 (t - 2-) - () .t: 4 "} (3)

From the output of the second mixer 4, oscillations (3) are transmitted to a narrow-band filter 5 tuned to the frequency at the output of which the signal has the form

and

P

 UCMZ af cos

+ yin) j, +,

CHA - (with

(four)

where K „a, is the transmission coefficient of a narrow-band filter.

The phase shift of the oscillations at the output of narrow-band filter 5 when fine tuned to the QCA frequency will be the same as at its input.

From the output of the stabilized oscillator 2, the oscillation also enters the first input of the fourth mix.

There is a compensation of instability of the non-55 cells 7, the output of which is connected to

the actual frequency of the FM input signal.

Indeed at the input of the device and at the first input of the second mixer 4

the input of the third mixer 6, the second input of which receives the oscillation from the output of the narrowband filter 5.

ten

From the output of the third mixer 6, the oscillation is fed to the input of the sixth mixer 10, the output of which is connected to the input of the seventh mixer 11, to the second input of which oscillates from the output of the controlled oscillator 14. At the same time, the oscillation from the controlled output generator 14 through the second delay line 9 is delivered to the second input of the sixth mixer 10. From the output of the seventh mixer 1, the oscillations arrive at the input of the resonant amplifier 12, the output of which is connected to the second input of the fourth mixer 7. Included .c the ring nenie mixers 7, 6, 10, 11 and a tuned amplifier 12 form a self-oscillating system in which a steady state at vtol - nenii phase balance balance conditions and amplitudes exist stable kle bath with a frequency equal to the stabilized oscillator. Oscillations of the same frequency are applied to the inputs of the phase detector 13 -25; therefore, the control voltage at its output is zero and the frequency of the controlled generator 14 is equal to the initial (initial) value Ots. jn In series-connected mixtures of bodies 7 and 6, the oscillations return to a hydrodynamic state, while at the exit of the mixer - 7

20

with a frequency of 2Сор, equal to the sum of the frequencies of oscillations arriving at its inputs. At the output of the mixer 6, an oscillation with a frequency O. equal to the difference of the frequencies of the oscillations arriving at its inputs is selected. As a result of gate heterodyning at the output of the third mixer 6, the beat is shifted out of phase with respect to the oscillations at the output of the resonant amplifier 12 by the value of LSR

35

40

45

In stationary mode, at the output of the controlled generator 14, there is a oscillation with a nominal frequency O „r o, corresponding to the high-stable carrier frequency of the MOR of the input fecal.

In the dynamic mode, if there is a real FM input signal with an unstable carrier, the input phase shift changes & (p, the oscillation frequency in the self-oscillating system formed by

- (QJ + iCoc) o j, (where the phase ring connection is in blocks 7, 6,

the oscillation shift in the filtration chains 10, 11 and 12, is deviated relative to

mixers 6 and 7). In sequential terms, because

The coupled mixers 10 and 11, also without the balance of the phases, are performed on the other, and a returnable heterodyning frequency occurs. At the output of the phase oscillation, and at the output 50 of the vector tector 13, a control of the mixer 10 appears, oscillating

with a frequency equal to the sum (+ o „) of the oscillation frequencies received

The main signal is fed to the control oscillator 14, and its frequency is changed by the value of ftW, as well as to its inputs. At the output of the seventh, that the condition of phase balance in the autocolle of the filter 11 is distinguished by oscillation with the beam system formed

Cams 7, 6, 10, 11 and 12 are again performed at frequency Oj-. Balance condition

totoy (co, d) equal to

the difference in the frequency of oscillations received at its inputs. As a result

-phases in this case takes the form

heterodination at the output of the seventh mixer 1 I, the oscillation is shifted out of phase relative to the oscillation at the second input of the holder 10 by iC ((-Rem "

-Coppo Tj, (or рsr с with „„ + Qttro lS, if the output of the sixth mixture of bodies 10 is different, the difference frequency is often the same, and the output of the seventh mixer 11 is the total frequency), where o, j is the signal delay time in the second delay line 9, GpJ, „- the first shift of the oscillation in the filtration circuits of mixers 10 and 11; Considering the above phase relations, the phase balance condition for the auto-vibration system formed by the mixers 7, 6, 10 included in the ring joint , 11 and the resonant amplifier 12 can be represented as

ifcM7. -UOHT ,, + Cf ,,, -W.oS

+ KT (5)

or

 V Che,

: MI

+ Kir,

where K 0, 1, 2, 3, ...;

 phase shift of oscillations

fPt

resonant amplifier.

In stationary mode, at the output of the controlled generator 14, there is a oscillation with a nominal frequency O „r o, corresponding to the high-stable carrier frequency of the MOR of the input fecal.

In the dynamic mode, if there is a real FM input signal with an unstable carrier, the input phase shift changes & (p, the oscillation frequency in the self-oscillating system formed by

ring connection blocks 7, 6,

-phases in this case takes the form

Rsm. , + q c «,, (Unro +

-nlo „,) + 4 pa K1G (6)

or

Q cM,, tfcM. (nro +

: + ssgp) yy + Ch ps}

In this case, the magnitude of the phase shifts

,,., i jffcMi. RF remains virtually unchanged. And expressions (5) | and (6) imply that the increment is often .-- 1t of the controlled oscillator 14, caused by instability of the average often | you FM input signal, is equal to

U0 "r

having chosen

- yso „with g,

6.2

(7)

 get ASO Lso „

The oscillation of the oscillator 14 controlled by the frequency of 14 to the second input L of that mixer B, at the output of this (the mixer, we get the FM: oscillations with a highly stable average frequency

) + fbfO .. -iU) (С0 „-« „r).

-pgo) + (ЫYN -Sh „) (too -Y

pgo

Thus, the frequency of autocollections in an annular connection is formed by four (single-band) 7, 6, 10, II and resonant: amplifier 12, the output of which is connected to the second input of the fourth mixer 7, during operation of the device It remains unchanged and equal to the frequency of the stabilized oscillator 2. Therefore, the stability of the forced self-oscillations in the considered auto-oscillatory system will be determined mainly by the stability of the frequency of the stabilized auto-oscillator, which can be made Artsev. In addition, the accuracy of pre. formation of phase modulation, the instability of the center frequency of the FM signal into a frequency depends substantially on stable oscillations, therefore, as a controlled oscillator, it is 14

0

five

0

25

thirty

35

40

45

Differently use a controlled crystal oscillator.

Thus, the proposed device allows for at least an order of magnitude increase in the stability of the average frequency of the output FM signal.

Claims (1)

Invention Formula A device for stabilizing the average frequency of a frequency-modulated signal, containing a first delay line connected in series, whose input is the device's input, the first mixer, another input connected to the output of a stabilized oscillator, the second mixer, another input connected to the device's input , a narrow band filter and a third mixer, as well as a second delay line, a fourth mixer, one input of which is connected to the output of a stabilized auto generator, and a fifth mixer, one in The device is connected to the input of the device, and the output is the output of the device, characterized in that, in order to increase the stability of the average frequency of the frequency-modulated signal, the sixth mixer, the seventh mixer, the other mixer the inputs of which are connected respectively to the output and input of the second delay line, a resonant amplifier, the output of which is also connected to the second input of the fourth mixer, phase detector, second input cat This is connected to the output of a stabilized auto generator, and a controlled generator, the output of which is also connected to the input of the second delay line, and the output of the fourth mixer is connected to the second input of the third mixer.