SU1539956A1 - Frequency-modulated crystal oscillator - Google Patents

Abstract

The invention relates to radio engineering and can be used in systems of automatic frequency control. The purpose of the invention is to increase the frequency tuning range and to ensure that the frequency control is balanced with the frequency without impairing its slope. The device contains transistors 1, 2, emitter follower 4, quartz resonator 5, current source 6, control voltage source 7, load 8, inductance coil 14. The goal is achieved by introducing into the device a transistor 3, three capacitors 9-11, a current distributor 12 and a voltage divider 13. When the control voltage changes from the maximum value of one polarity to the maximum value of the other polarity, the frequency is adjusted from the lower to the upper limits of the range. 1 il.

Description

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The invention relates to radio engineering and can be used in systems of automatic frequency control.

The purpose of the invention is to increase the frequency tuning range and ensure balancing of the frequency control characteristic without deteriorating its slope.

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

The frequency of the on-modulated quartz oscillator includes the first, second, and third transistors 1,2 and 3, the emitter follower 4, the quartz resonator 5, the current source 6, the control source 7 , load 8, first, second and third capacitors 9, 10 and 11, current distributor 12, voltage divider 13, inductance coil 14.

Frequency-modulated crystal oscillator operates as follows.

When the control voltage source 7 is present at the outputs, the magnitude and polarity of which ensures the full opening of the first transistor 1 and the closing of the second and third transistors 2 and 3 by setting the corresponding mode of the distributor 12, the positive feedback signal from the output of the amplifier repeater 4 passes through series-connected crystal oscillator 5, the second capacitor 10 and the coil 14 to the emitter of the first transistor 1. In this case, the open first transistor 1 together with the emitter follower 4 and the positive feedback circuit form a quartz oscillator circuit whose oscillation frequency will be lower than the serial resonance frequency of the quartz resonator 5 due to the presence of coil 14 in the circuit.

By changing the polarity of the control voltage of the source 7 and setting the appropriate mode of the distributor 12, the third transistor 3 opens and the first and second trapistors 1 and 2 close. In this case, the third transistor 3 together with the positive feedback circuit consisting of a quartz resonator 5 and the first capacitor 9, form a quartz oscillator circuit, the frequency of which will be higher than the initial (at zero control voltage) frequency,

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Since the first capacitor 9 connected in series with the quartz resonator 5 in series increases the frequency of the oscillations generated compared to the serial resonance frequency of the quartz resonator 5.

When the control voltage changes from the maximum value of one polarity to the maximum value of the other polarity, the frequency is adjusted from the lower to the upper limit of the range. When this occurs, the sequential opening of the first, second and third transistors -. 1, 2 and 3. For control voltage values close to zero, the quartz oscillator circuit is formed by a second transistor 2 emitter follower 4 and a quartz resonator 5. In this case, the frequency of the generated oscillations is close to the frequency of the series resonance of the quartz resonator 5.

The third capacitor 11 at the frequency of the generated oscillations closes the bases of the first, second and third transistors 1, 2 and 3 to a common bus. At the load 8, the vector summation of the signals passing through the first, second and third transistors 1, 2 and 3 is carried out. The divider 13 and the source 6 provide the frequency-modulated dc oscillator with direct current.

Claims (1)

Invention Formula A frequency-modulated crystal oscillator containing the first and second transistors, the load that is connected between the power bus and the combined collectors of the first and second transistors, the emitter follower, whose input is connected to the combined collectors of the first and second transistors, and the output through the quartz resonator is connected to the second emitter transistor, the current source, the first output of which is connected to the common bus, the inductor, the first output of which is connected to the emitter of the first transistor and the source ravl guide voltage, characterized in that, in order to increase the tuning range of the frequency and providing a frequency control The balance characteristics without sacrificing its steepness, introduced the third transistor whose collector is connected to the combined collectors of the first and second transistors, a voltage divider that is connected between the power bus and a common bus, whose output is connected to the bases of the first, second and third transistors, the first capacitor that is connected between the emitters of the second and third transistors , the second capacitor, which is connected between the emitter of the second transistor and the second output of the inductance-, the third a capacitor that is connected between the voltage divider and a common bus, a current distributor, the first, second and third outputs of which are connected to the emitters of the first, second and third transistors, respectively, and whose input is connected to the second output of the current source, the first and second outputs The control voltage source is connected respectively to the first and second control inputs of the current distributor.