SU1427546A1 - Frequency-modulated quartz osciliator - Google Patents

Abstract

The invention retreats to radio engineering. The purpose of the invention is to reduce the parasitic amplitude modulation (PAM) of the output signal. The generator contains a high-pass filter 1, 2.8 to 9 low-pass filters, controlled quartz 3 and 6, an integration block 4, a phase modulator 5, a synchronizer 7, amplitude detectors Yu and 1, a paraphase comparator 12, analog switches 13 and 14 and analog adder 15. The goal is achieved by alternately connecting to the phase modulator 5 grs 3 or 6, SS having a PAM element for a given control frequency, I Il. |

Description

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The invention relates to radio engineering and can be used in radio communication devices.

The purpose of the invention is to reduce the parasitic amplitude modulation (PAM) of the output signal.

The drawing shows a structural electrical circuit of a frequency-modulated crystal oscillator.

. A frequency-modulated crystal oscillator contains 1 high frequencies, the first low pass filter 2, the first controlled variable crystal oscillator 3, the block ,, 4 integra tions, the phase modulator 5, the second controlled quad oscillator 6, the synchronizer 7, the second 8 and third 9 low-pass filters; the first 10 and second 11 amplitude detectors; the phase comparator 12; the first 13 and second 1A analog keys and the analog adder 15;

Frequency-modulated crystal oscillator operates as follows

The input signal through the filter 1 and the integration unit 4 is fed to the first input of the phase modulator 5 o. The spectrum of the modulating influence is divided by filter 1 and 2 into

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(flat, flat-convex, flat-bent).

Suppose that a larger value of the PAM level is observed at the output of the first controlled quartz generator 3, the voltage at the PAM frequency is detected by filter 8 and fed to the amplitude detector 10. Similarly, the voltage from the output of the controlled quartz generator 6 is fed to the input of filter 9 and from its input to the input of the amplitude detector 11, Since the PAM level is greater at the input of the amplitude detector 10 than at the input of the amplitude detector 11, the voltage at the output of the amplitude detector 10 is greater than. at the output of the amplitude detector P. These voltages are fed to the inputs of the paraphase comparator 12. The voltage coming from the output of the amplitude detector 10 to the first input of the paraphase comparator 12 is greater than the voltage from the output of the amplitude detector 1 to the second input therefore, voltage 1 appears at its forward output, which is fed to the second input of the analog switch 14 and from 25

low-frequency and high-frequency covers it,

are supplied. Low frequency spectrum

including a constant component — it directly affects the frequency

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Nerators 3 and 6, the synchronizer input analog adder 15 and on

Through the open second analog switch 14, the voltage from the output of the second controlled quartz oscillator 6 with a low PAM level is supplied to

..protected equality, instantaneous hour .TOTj generated signal.

Given high-frequency resonators of complex slices, the frequency of parasitic oscillations can be higher than the frequency of the main resonance by tens, hundreds of hertz. Therefore, starting with the frequencies of the controlling oscillation, hundreds of herds will experience significant distortion of the output signal.

Moreover, the HAM level at these frequencies can be tens of percent. Quartz resonators for controlled quartz oscillators 3 and 6 are selected so that the frequencies of their main resonances coincide when the anharmonic frequencies do not match. Similar spectral characteristics are inherent in resonators made of quartz crystals at different cut-off angles, as well as in a resonator Md having various forms of quartz plates

Through the open second analog switch 14, the voltage from the output of the second controlled quartz oscillator 6 with a low PAM level is supplied to

analog adder input 15 and on

from its output to the phase modulator 2. At the same time, the analog switch 13 is closed — the voltage of O is applied to its second input from the inverse output of the paraphase comparator 12. Since the voltage supplied to the input of the phase modulator 5 is low The PAM level, the output frequency-modulated voltage also has a low PAM level.

Similarly, the highest PAM level is observed at the output of the second controlled quartz oscillator 6. A second quartz oscillator 3 with a lower PAM level is connected to the second input of the phase modulator 5. Thus, alternately connecting the controlled quartz oscillators 3 and 6, which have the smallest SAM level at this control frequency, to the phase modulator 5 allows significantly reducing the AMF level of the output frequency-modulated

signal frequency-modulated crystal oscillator.

Formula of the invention

A frequency modulated crystal oscillator comprising a series-connected high-pass filter integration unit and a phase modulator, a first-pass low pass filter and a first controllable crystal oscillator are connected in series, the inputs of the high-pass filter and the first low-pass filter being combined and modulated quartz oscillator, characterized in that, in order to reduce the parasitic amp

 output modulation, a synchronizer, an analog adder, the output of which is connected to the second input of the phase modulator, a second controlled quartz oscillator, the control input of which is connected to the output of the first low-pass filter, the first analog switch which is connected between the output of the first controlled crystal oscillator and the first input of the analog totalizer; ra, the second analog key which

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connected between the output of the second controlled crystal oscillator and the second input of the analog adder, a para-phase comparator, the first and second outputs of which are connected to the control inputs of the first and second analog switches, respectively, the second low-pass filter connected in series and the first amplitude detector, whose output connected to the first input paraphase comparator, connected in series tre-. tiy low pass filter and second

15 amplitude detector, the output of which is connected to the second input of the paraphase comparator, while the outputs of the first. and the second controlled quartz oscillators are connected respectively to

20 to the input of the second low-pass filter and the input of the third low-pass filter, the synchronizer input is connected to the output of the first controlled crystal oscillator, and the synchronizer output

25 is connected to the control input of the second controlled quartz oscillator, and the frequencies of the first and second controlled quartz oscillators are chosen equal, and the anharmonics - not 30 coinciding.

Claims (1)

Claim A frequency-modulated crystal oscillator containing a series-connected high-pass filter, an integration unit and a phase modulator, a series-connected first low-pass filter and a first controlled crystal oscillator, while the inputs of the high-pass filter and the first low-pass filter are combined and are the input of a frequency-modulated crystal oscillator . ra, characterized in that, in order to reduce parasitic amplitude modulation of the output signal, a synchronizer, an analog adder, the output of which is connected to the second input of the phase modulator, a second controlled crystal oscillator, the control input of which is connected to the output of the first low-pass filter 25, is introduced into it, the first analog key, which is connected between the output of the first controlled crystal oscillator and the first input of the analog ra, the second analog key, in total · which is connected between the output of the second controlled crystal of a quartz oscillator and second, by the input of an analog adder, a pair is a phase comparator, the first and second e outputs of which are connected to the control inputs of the first and second analog keys, respectively, a second low-pass filter and a first amplitude detector connected to the first input in series a paraphase comparator, a third low-pass filter and a second 15 amplitude detector connected in series to the second input of the paraphase comparator, the outputs of the first st. and the second controlled crystal oscillators are connected respectively to the 20th input of the second low-pass filter and the input of the third low-pass filter, the input of the synchronizer is connected to the output of the first controlled crystal oscillator, and the output of the synchronizer is connected to the control input of the second controlled crystal oscillator, and the frequencies of the first and the second controlled quartz oscillators are chosen equal, and the anharmonics are not - 30 matching.