SU1020967A1 - Frequency modulator - Google Patents

Description

The invention relates to radio engineering and can be used to generate frequency-modulated oscillations, for example, in drivers of radio transmitting devices of multichannel telemetry systems.

A frequency modulator is known that contains a converter transistor cascade, in which the drain circuit of the transistor includes a band-pass filter, a power source, first and second LC-oscillating circuits connected via respective separation capacitors to the first and second gates of the transistor of the conversion transistor cascade, and the first and second varicaps connected between the corresponding chokes, the other terminals of which are combined and are the input of the modulating signal of the frequency module pa and the corresponding LC-oscillatory circuit CO

However, the known frequency modulator, the advantages of which are relatively high linearity of the modulation characteristic and increased frequency deviation, is relatively difficult to implement, since it also includes at least two transistors, which are made by two auto-oscillators and two different sources of nutrition.

The purpose of the invention is to simplify the frequency modulator.

This goal is achieved by the fact that in a frequency modulator containing a converter transistor stage, the drain of the transistor of which includes a band-pass filter, a power source, the first and second LC-oscillating circuits, connected via the respective separation capacitors, respectively, to the first and second gates of the transistor transistor cascade, the first and second varicaps, included -Means corresponding to those of the chokes, the other outputs of which are combined and are input modulating signal of the frequency modulator and the corresponding LC-oscillating circuit, the source of the transistor of the converter transistor cascade is connected via an auto-transformer connection to the first and second LC-oscillating circuits, the varicaps are connected antiphase to the LC-oscillating circuits, the first varicap

connected to a power source through an inputted adjustable voltage divider.

The drawing shows a circuit diagram of a frequency modulator.

The frequency modulator contains a converter transistor cascade on a field-effect transistor 1 with two gates, a band-pass filter 2, a power source 3, a first1Y and a second LC-oscillating circuit and 5, separation capacitors 6 and 7, the first, second varicaps 8 and 9, chokes 10 and 11, an adjustable divider 12 voltage.

The frequency modulator operates as follows.

The modulating signal arriving at the input of the frequency modulator through the choke 10 acts on the anode of the varicap 8 and simultaneously through the choke 11 on the cathode of the varicap 9.

A field-effect transistor 1 with two gates simultaneously performs the functions of an active element of a converter transistor cascade and active elements of autogenerators assembled in a three-point scheme with an autotransformer connection. The first of the oscillators includes the first LC-oscillating circuit 4 with the first varicap 8, connected via a coupling capacitor 6 to the first gate of the field-effect transistor 1, the source of which is connected to the first LC oscillating circuit 4 by means of. an autotransformer connection (with a tap of the inductance of the LC-ventilation circuit k). The second oscillator includes a second LC oscillating circuit 5 with a second varicap 9 connected via a coupling capacitor 7 to the second gate of the field-effect transistor 1, the source of which is connected to the second LC oscillating circuit 5 via an autotransformer coupling with the inductance of the LG oscillating circuit 5. Thus, the current. Drain of the field-effect transistor 1 contains oscillations of the frequencies of the wallpaper of the generators, which are always different, and. their combinations.

Since the coefficients of the inductors of the first and second LC-oscillating circuits 4 and 5 to the source circuit of the field-effect transistor 1 are less than 0.1, the influence of different frequencies of the oscillators on each other is absent.

3 1020967-4

Band-pass filter 2 allocates the B-frequency frequency modulus offered by the fineness of the frequency of two oscillators. The use of P-regulation regulates the output. At the output of the frequency frequency models 12, the voltage also oscillates, often reducing the number of power sources. which changes in accordance5 without preserving the advantages of two-continuous and arbitrary measuring-known frequency modulation of the input modulating signal-torus — high linearity and higher frequency deviation.

Claims (1)

A FREQUENCY MODULATOR containing a converter transistor cascade, in which a bandpass filter is included in the drain circuit of the transistor, the power supply * the first and second <LC oscillatory circuits connected through the corresponding isolation capacitors to the first and second gate of the transformer, respectively -FI t transformer transcascade, the first and second included between the respective chokes, the other outputs of the ricapa resistor, which are combined and are the input of the modulating signal of the frequency modulator, and the corresponding LC-oscillatory circuit, which differs in that, in order to simplify frequency modulator, the source of the transistor of the transistor transistor cascade is connected via an autotransformer connection to the first and second LC oscillatory circuits, varicaps are connected out of phase to the LC oscillations Tel'nykh contours § frames, wherein the first variable-capacitance diode connected with | with a power source through an adjustable voltage divider introduced.