SU756600A1 - Quartz generator - Google Patents

Description

The invention relates to radio engineering and is intended for the use in radio engineering devices for various purposes, in particular in radio transmitters and radio receivers 5 devices.

Known crystal oscillators used in transceiver devices include a generator, a transistor, a quartz resonator and a capacitor connected in series with it in the emitter-base circuit of the transistor, a capacitor connected between the emitter and the base of the transistor, a voltage divider connected between 15 minus terminal of the source voltage and ground, a resistor in the emitter circuit and a choke in the collector circuit of the transistor [1].

• A known crystal oscillator containing a transistor, a voltage source, an oscillating circuit consisting of an inductance and a capacitor, a crystal oscillator connected between the base of the transistor and. ground, a resistive voltage divider to supply an offset to the base of the transistor and stabilize the operating point of the transistor, connected between the negative terminal of the voltage source and ground;

2

a resistor and a capacitor connected in parallel between the emitter and ground; a capacitor connected between the emitter and the collector of the transistor £ 2 ^.

The described quartz oscillators have the following disadvantages: the generator output power depends on the parameters of the quartz resonator, primarily on the dynamic resistance. Quartz resonators produced by the industry at frequencies of 90-250 MHz have a large variation in dynamic resistance (from 20 to 1200 m), as a result of which the generators have different output power, which creates great difficulties in developing the devices in which they are used and reduces the quality indicators of these devices; There is no frequency adjustment in the generator, which leads to additional difficulties in setting the nominal frequency of the generator.

The purpose of the invention is to increase the stability of the parameters when changing 25 parameters of quartz resonators, as well as expanding the limits of the frequency tuning of the generator.

To achieve this goal, a quartz oscillator containing a transistor, into the collector circuit of which

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756600

an inductor is included, a quartz resonator, a trimming resistor is connected to the collector circuit of the transistor in series with the inductor, and an additional inductor is connected in series with the quartz resonator in series with a temperature-dependent trimmer in the temperature range.

FIG. 1 is a schematic diagram of the device; in fig. 2nd its temperature-frequency characteristic; in fig. 26 - dependence of the generator output power on temperature; in fig. 2c - the value of the output power of the generator, when using quartz resonators in it with different dynamic resistance.

The quartz generator contains a transistor 1, between the base of which and the earth are connected in series a quartz resonator 2 and an inductor 3, stabilizing the operation mode of the transistor, a voltage divider on resistors 4 and 5 connected between the negative terminal of the voltage source and ground, a blocking capacitor 6, a resistor 7 in the emitter circuit of the transistor, a trimmer capacitor 8 connected between the emitter and the earth, the coil 9 of the inductance in the collector circuit, in series with which the trimmer resistor 10 is connected, divide capacitor 11. The oscillatory circuit in the collector circuit of the transistor, which is formed by the inductor 9 and the capacitance of transistor 1, must be tuned to a frequency higher than the resonant frequency of the quartz resonator. The collector circuit is inductive in nature at the generation frequency, and this ensures easier excitation of the whole circuit.

The balance of the phases in the oscillator is achieved by selecting a certain value of the capacitor capacitance 8, which is also designed to fine tune the generator to the operating frequency.

In order for a spurious excitation at a non-quartz frequency to occur in the circuit, it is necessary that the capacitance between the emitter and collector of the transistor be as small as possible. Therefore, in the generator, feedback is carried out only at the expense of the own capacity of the collector-emitter of the transistor; there is no external capacitance between the indicated points of the circuit. Since the trimming resistor 10 is included in the collector circuit of the oscillator, the change in its magnitude causes a change in the quality factor of the circuit and the mode of the transistor, and hence the output

power generator, which is |

Kim way you can do almost

constant regardless of parameters

.applied quartz resonator.

The collector circuit is tuned to a frequency that is different from the resonant frequency of the quartz resonator, i.e. is a complex impedance at the operating frequency of the generator, which makes it possible to use a resistor 10 for discrete adjustment of the frequency of the crystal oscillator.

The resistor can be made thermo-dependent with the desired dependence of resistance on temperature, and then in the generator the temperature compensation of the resonator frequency drifts occurs, which allows increasing the frequency stability of the oscillator in a wide temperature range.

Trimmer capacitor 8 can be replaced by a varicap, while adding a varicap power supply circuit, and then the generator will have electronic frequency tuning, which is necessary when using the generator in sealed structures or installing it in hard-to-reach places.

The use of a resistor as a trimmer allows you to get in the manufacture of a generator with almost the same output power, regardless of the parameters of the used quartz resonators, i.e. completely eliminate the selection of expensive resonators and other elements of the circuit and thereby significantly reduce the cost of the generator and make it serially capable.

Claims (2)

Claim 1. A quartz oscillator containing a transistor, the collector circuit of which includes an inductor, a quartz resonator, characterized in that, in order to increase stability when changing parameters of quartz resonators, as well as expand the limits of the frequency tuning of the generator, and the collector circuit of the transistor is in series with the inductor a trimming resistor is included, and an additional inductance coil is included in series with the quartz resonator in series with it. 2. The generator according to claim 1, characterized in that, in order to increase the frequency stability of the generator in the temperature range, the trimmer resistor is heat-sensitive.