SU1190452A1 - Tuneable two-frequency self-excited oscillator - Google Patents

Abstract

REJECTABLE TWO-FREQUENCY AUTOGENERATOR, containing - first and second varactors, one of which electrodes of the same name are connected to each other, and other electrodes of the first and second varactors are connected respectively to the first terminals of the first and second coils, and the first and second transistors, whose emitters are connected respectively with the first conclusions of the first and second chokes, oh. that is, in order to expand the range of operating frequencies while increasing the linearity of the tuning. A balancing transformer is inserted into it, the first tunable capacitor, which is connected between the emitter of the first transistor and the first output of the first winding of the balancing transformer, the second tunable capacitor, which is connected between the emitter of the second transistor and the first output of the second winding of the balancing transformer, the first limiting resistor, the first output of which connected to the base of the first transistor, the second limiting resistor, the first output of which is connected to the base of the second trans the first separator capacitor, which is connected between the base of the first transistor and the second output of the first inductor, the second separator capacitor, which is connected between the base of the second transistor and the second output of the second inductor, the first additional resistor, which is connected between the connection point of the first varactor and the first cathode inductance and common voltage, the second additional resistor, which is connected between the point of connection of the second varactor and the second inductor) but the third tunable capacitor and the third additional resistor, the first terminals of which are connected to the connection point of the first and second varactor between themselves, while the collectors of the first and second transistors are connected to the common bus, the second output of the second winding balancing transformer is connected to the common bus, the second terminals of the first and second chokes and the first and second limiting resistors are respectively the inputs of the supply currents and bias voltages, the second output of the third will complement The second output of the third tunable capacitor is the output of the second harmonic signal, and the second output of the first winding of the balancing transformer is the output of the first harmonic signal of the tunable two-frequency auto-oscillator.

Description

The invention relates to radio engineering and can be used as a generator of two measurements of the frequency of sinusoidal signals, for example, in various radio measuring devices.

The purpose of the invention is to expand the range of operating frequencies with increasing linearity adjustment.

Figure 1 shows a circuit diagram of the proposed tunable dual-frequency oscillator; Fig.2 - timing charts of his work.

Tunable dual-frequency oscillator contains the first and second varactor 1 and 2, the first and second transistors 3 and 4, the first and second inductors 5 and 6, the first and second coupling capacitors 7 and 8, balun transformer 9, the first and second tunable capacitors 10 and 11 , the first and second limiting resistors 12 and 13, the first and second chokes 14 and 15, the first, second and third additional resistors 1618, the third tunable capacitor 19. The tunable dual-frequency auto-oscillator works as follows .

The serial oscillating circuit of the tunable dual-frequency oscillator is formed by barrier capacitances of pn junctions 1 and 2, inductance coils 5 and 6, and input impedance elements without transistors 3 and 4 which are mainly determined by the capacity of the collector junction, since the capacitance of tunable capacitors 10 and II are much smaller than the capacitance of the collector junction, and the absolute value of the impedance of the chokes 14 and 15 is much larger than the impedance of the collector junction in the operating frequency band. Positive feedback is provided by the feedback of transistors 3 and 4 due to base modulation (the Airlie effect), as well as due to the parasitic capacitance of the design of transistors 3 and 4. Dp alignment of the input impedances of the bases of transistors 3 and 4 and electrical symmetry transistors 3 and 4 are supplied set at setting the bias voltage through

The limiting resistors 12 and 13. Oscillations arising in the oscillating circuit fall on the bases of transistors 3 and 4 in antiphase. When the electrical symmetry of the circuit and the identity of the varactor I and 2 between the bases of the transistors 3 and 4 will operate a sinusoidal voltage of the first harmonic. Under the action of this voltage, the sinusoidal current of the first harmonic flows through the varactors 1 and 2 and at the point of their connection only the voltage of the even harmonics of the self-oscillations is present. When performing varactors 1 and 2 on p-C-junctions with a stepwise distribution of impurities, this voltage will be sinusoidal with the frequency of the second harmonic.

The barrier capacitance — two oppositely connected pj-junctions of varactors 1 and 2 depends on the blocking bias voltage that is applied to the point of their connection. .

B. The case of a symmetric effect of a harmonic signal with a frequency of CO on two opposite-connected stepped p-n-junction with identical characteristics. The voltage at the point of their connection relative to the point of symmetry of the circuit contains a variable component of the doubled frequency, which through a tunable capacitor 19 is fed to the output of a tunable two-frequency oscillator.

The signals of the first harmonic on the emitters of the transistors 3 and 4 are antiphase, and the second harmonics are in phase. However, these relationships hold. . inaccurately because transistors 3 and 4 are not identical. To adjust the amplitude-phase ratios of the signals fed to the first and second windings of the balancing transformer 9, tunable capacitors 10 and 11 are used, which simultaneously determine the overall signal level at the output of the first harmonic signal. When adding signals from the emitters of transistors 3 and 4 on the balancing transformer 9, the signals of the first harmonic are added, and the signals of the second harmonic are subtracted, which reduces the nonlinear distortion. Dp increase linearity tuning value of the resistance registers 12, 13 and 18 in the chain x - offset spec3I

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During operation of a tunable dual-frequency oscillator, the signal is partially detected at pn-junctions of varactors 1 and 2, as a result of which direct current flows through varactors 1 and 2 and the chains of their displacement. On resistors 16-18, an auto-bias voltage occurs, proportional to. This current, which shifts the operating point on the characteristics of varactor 1 and 2 towards the most locking point. With decreasing locking bias on p – n junctions, the frequency slope increases, but the current increment through varactors 1 and 2 and, consequently, the magnitude of the auto bias increment also increases. Following this, at equal increments of the control voltage, the flow is made to the input of a tunable two-frequency auto-; generator, the increments of displacement at pn-junctions will be different. At voltages corresponding to the upper frequencies of the tuning range and small, due to the insignificant increase in the magnitude of the bias voltage, the displacement increment at the p -, transitions is equal to the increment of the control voltage. When eg 90A52: - 4

Notwithstanding the lower part of the range and the large slope of frequency tuning, the current increments of the varactor 1 and 2 increase, and the same 5 reduces the increment of the offset by. transitions.

Figures 2a and b show, respectively, the diagrams of the diagrams) of the Bae-collector of transistors 3 and 4} in r. 2c - the diagrams of the voltage between the transistors 3 and 4; Fig. 2d shows stress patterns at the junction point of varactors 1 and 2; na.2d, e, g, respectively, the diagrams of the emitter current and the current of the first and second harmonics of the transistor 3i in Fig. 2h, and k, respectively, the diagrams of the emitter current and the current of the first and second harmonics of transistor 4; on Fig.2l - Escher current at the output of a balancing transformer 9.

The base voltages of the transistors 3 and 4 are non-sinusoidal, but due to the synphase of their second harmonic components. . live between the base transistors 3 and 4, and consequently, on the conclusions of the varactor 1. and 2, connected respectively to the coils 5 and 6 of the induk-. close to sinusoidal, so at the junction point of varactors 1 and 2 only the second harmonic signal will be present.

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Claims (1)

TUNABLE TWO-FREQUENCY AUTOGENERATOR, comprising the first and second varactors, one of the same electrodes of which are interconnected, and the other electrodes of the first and second varactors are connected respectively to the first terminals of the first and second inductors, as well as the first and second transistors, the emitters of which are connected respectively to the first conclusions of the first and second chokes, characterized in that, in order to expand the operating frequency range while increasing the tuning linearity, symmetrizing transformer, the first tunable capacitor that is connected between the emitter of the first transistor and the first output of the first winding of the balancing transformer, the second tunable capacitor, which is connected between the emitter of the second transistor and the first output of the second winding of the balancing transformer, the first limiting resistor, the first output of which is connected to the base of the first transistor, the second limiting resistor, the first output of which is connected to the base of the transistor, the first isolation cond a nsator, which is connected between the base of the first transistor and the second terminal of the first inductor, a second isolation capacitor, which is connected between the base of the second transistor and the second terminal of the second inductor, the first additional resistor, which is connected between the connection point of the first varactor with the first inductor and the common yin , the second additional resistor, which is connected between the connection point of the second reactor with the second inductor and the common bus, the third tunable con a capacitor and a third additional resistor, the first terminals of which are connected to the junction point of the first and second varactors with each other, while the collectors of the first and second transistors are connected to a common bus, the second terminal of the second winding of the balancing transformer is connected to a common bus, the second terminals of the first and second chokes and the first and second limiting resistors are respectively the inputs of the supply currents and bias voltages, the second output of the third additional resistor is the input of the control voltage In this case, the second output of the third tunable capacitor is the second harmonic signal output, and the second output of the first winding of the balancing transformer is the first harmonic signal output of the tunable two-frequency oscillator. 1 1190452 '2