SU1543535A1 - Modulator - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to increase the deviation of the amplitude of the output signal. The modulator contains transformers 1 and 8 with windings 2,3,4,9 and 10, capacitors 5 and 7, an element with a controlled resistance, made in the form of a field-effect transistor 6, a bias circuit 11, a source 12 of a carrier frequency signal. The goal is achieved by the introduction of switches 13 and 14, which have two positions. In the "1 P" position, the parasitic amplitude modulation in the device is zero, and the phase modulation is equal to the total value of the deviations of the carrier frequency phase under the action of the modulating signal in two oscillatory circuits. In position "2 P" parasitic phase modulation is negligible. 1 il.

Description

The invention relates to radio engineering and can be used to form both phase-modulated and amplitude-modulated signals in various radio communication devices, radar systems and radio measurements.

The purpose of the invention is to increase the amplitude deviation of the output signal.

The drawing shows the principle electrical circuit of the modulator. The modulator contains the first transformer 1 with the primary winding 2 and the first 3 and the second 4 secondary windings, the first capacitor 5, the element with controlled resistance, made in the form of a field-effect transistor 6, the second capacitor 7, the second transformer 8, which includes the first primary 9 and secondary 10 windings, bias circuit 11, carrier frequency signal source 12, as well as the first 13 and second 14 switches.

The modulator works as follows.

When the first 13 and second 14 switches are in position 1 of the first 3 and second 4 secondary windings of the first transformer 1 are connected according to and represent one secondary winding, which with the second capacitor 7 and the field effect transistor 6 - body circuit, and the primary winding 9 of the second transformer 8 with the first capacitor 5 - the second LC-oscillating circuit.

The signal from the output of a 12-kal carrier source signal enters the first LC oscillating circuit tuned to the carrier frequency. The modulating signal arrives at the gate of field-effect transistor 6 and changes its channel resistance. This changes the quality factor of the first LC oscillating circuit and As a consequence, the phase modulation of the carrier signal is carried out, and parasitic amplitude modulation occurs along with it. Phase and amplitude modulated signal from the first LC oscillating circuit enters the second LC oscillating circuit, in which also under the effect of a change in the active resistance of the channel of the field-effect transistor 6, phase and amplitude modulation is performed. At the same time by including

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Pi of the second LC oscillating circuit between the midpoint of the composite secondary winding of the first transformer 1 and the drain of the field-effect transistor 6, the amplitude modulation of the signal in it is counter-phase with respect to the amplitude modulation in the first LC circuit, i.e. it is equal to zero, and the phase modulation is added to the phase modulation that has arisen in the first LC circuit, i.e. is equal to the total value of the phase deviation of the carrier frequency under the action of the modulating signal in the first and second LC-oscillatory circuits. In this case, the processes in the modulator proceed as follows. When a field-effect transistor 6 arrives at the gate of the modulating signal, the resistance of its channel varies within wide limits. If its resistance differs little from zero (R 0) and B the considered time point, point a has a positive potential, and point b is negative, the current I, from point a flows through the second capacitor 7 and the channel of the FET 6 to point B. The current from point b then flows through the primary winding 9 of the second transformer 8 and the first capacitor 5 through the channel of the field-effect transistor 6 to point b. Current 12 flows through the primary winding 9 of the second transformer 8, creates a voltage drop across it, which is transmitted to the secondary winding 10 of the second transformer and then to the load. In this case, the phase shift between the voltages iBi Uaq is absent.

In the case when the resistance RK under the action of the voltage of the modulating signal satisfies the condition RK 0, the point and also at the considered moment of time has a positive potential, and the point b is negative, the current 13 from point a through the second capacitor 7 and the primary winding 9 the second transformer 8 flows to point c. When this current iL from point to through the primary winding 9 of the second transformer 8 and the channel of the field-effect transistor 6 flows to point b,

Currents 1-j and 1g create on the primary winding 9 of the second capacitor 8 a voltage drop U which

equal to the vector sum of the voltages generated on it due to the flow of currents l and 13.

When the condition is met, where XC7 is the reactance of the second capacitor 7, Xug is the reactance of the primary winding 9 of the second transformer 8, and when Rw changes from zero to R k 0 between the input voltage (UeS) and output voltage (U) Phase modulator phase shift 2 occurs. The amplitude modulation of the output voltage (between the points guide) is absent. The bias circuit 11 serves to select the operating point of the field-effect transistor 6. The first capacitor 5 allows the second LC oscillator circuit to be tuned to resonance, which reduces the energy consumed by it.

When the first 13 and second 14 switches are located in the 2P position, first 3 and second 4, the secondary windings of the first transformer 1 are switched in opposite. At the same time, the processes in the modulator proceed as follows. Under the influence of the modulating voltage that is applied to the gate of the field-effect transistor 6, the resistance of its channel varies within wide limits. If this resistance does not differ much from zero () and at the considered time points a and b have a positive potential, and points z and c are negative, then a current 11 flows from the point v to point a through the primary winding 9 of the second transformer 8, and from point b to point v through the channel of the field-effect transistor 6 and the primary winding 9 of the transformer 8 - (current 12. If the condition ХС1Ч- XLg is fulfilled, then for the current I ,, the resistance of the circuit has a capacitive character, and for the current 1g - inductive Consequently, the currents I 1 and 1g in the primary winding 9 transformer pa 8 are directed oppositely to each drugu.Pri execution conditions C7 X - X U9 Xug mutual compensation of the currents 11 and 14 full of primary winding 9 resulting current transformer 8 is zero is also zero voltage at the output of the modulator...

At the moment of time when the resistance RK under the mode-5 interaction

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The first signal will satisfy the condition RK O, and the points a and b will also have a positive potential, the current 12 due to R k O tends to zero. In this case, only the current I, flows through the primary winding 9 of the second transformer 8. The voltage drop created by this current is transferred to the modulator output.

The parasitic phase modulation in this case is negligible because the currents I., and 1 in the primary 15 winding 9 of the second transformer 8 flow counter and the phase shift is compensated.

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Claims (1)

Invention Formula A modulator containing the first transformer, the primary winding of which is connected to the output of the source of the modulated signal, and the secondary winding is connected in a ring with the first capacitor and the element with a controlled resistor, which is made in the form of a field-effect transistor The bias circuit is connected, and the source of the field-effect transistor is connected to the common bus, the second transformer, the primary winding of which is connected in parallel to the first capacitor, the second capacitor, the first output of which is connected to the station A field-effect transistor, the secondary winding of the second transformer is the output of the modulator, and the gate of the field-effect transistor is the input of the modulator, characterized in that, in order to increase the amplitude deviation of the output signal, the first and second switches are introduced into it and the first transformer is provided with a second secondary winding, the first output of which is connected to the output of the first switch, the first input of which is connected to the first input of the second switch and to the second output of the second capacitor, the second input of the first th switch is connected to the second input of the second switch, to the point connecting the first output of the first secondary winding of the first transformer and the first capacitor, and the output of the second switch is connected to the second output of the second secondary winding of the first transformer.