SU372640A1 - BALANCE MODULATOR - Google Patents

Description

one

The invention relates to modulators and can be used in clause, transmission, and transmission devices.

A balanced modulator is known, which contains two differential pairs of transistors with a cross-connection of collectors, and a current generator connected via two adjustable transistors to the junction of emitters of each differential pair of transistors.

The disadvantages of the known balanced modulator are weak carrier suppression and modulating frequencies, high sensitivity to variation in the parameters of circuit elements and poor stability of suppression; carrier frequency and modulating signals when the ambient temperature changes.

In the proposed balanced modulator, these disadvantages are eliminated due to the fact that an additional differential amplifier is connected between the collectors of the differential pairs and the current generator input.

The drawing shows a schematic diagram of the modulator.

The proposed balanced modulator contains two differential clauses, ares of transistors 1, 2 and 3, 4 with cross-connection of collectors, adjustable transistors 5, 6, current generators at transistor 7,

a transistor 8 in a diode switching on, which serves to thermally stabilize the current generator, an additional differential amplifier on transistors 9, 10, a capacitor 11 that serves; to suppress the carrier signal, and resistors 12-30. The balance modulator can be made integral, then terminals 31-45 serve as external terminals.

The current generator on the transistor 7 is connected via adjustable transistors 5 and 5 to the junction of the emitters of transistors 1, 2 to 3, 4, respectively. An additional differential amplifier on transistors 9, 10 is connected between the collectors of transistors 1, 3 V. 2, 4 differential pairs and the input of the current generator on transistor 7. Due to this, the properties of the balanced modulator are improved; which seeks to minimize any error signal. The reasons for the error can be the suppression of the carrier and modulating components, their second, third harmonics and various combinations of these harmonics, as well as a change in external conditions and the variation of the parameters of the elements.

If the amplitudes of the output signals taken from the collectors or emitters of the transducer are equal: resistors 9 and 10, which is determined in the first case — the need to amplify the modulated signals, in the second case — the need to agree with subsequent stages; the difference at the summation point — on the base of transistor 7 — is zero. When the amplitudes of the output signals are unbalanced in the resistor 27, a difference signal is produced, which, due to the effect of the negative feedback, passes through the transistors 7, 5, 6 w. 1, 2 c 3, 4, is allocated to the load resistors 18, 19 differential pairs of transistors, tend to minimize the error signal. A change in the gain of the device is made by changing the resistance value of the resistors 28, 29, 30. W ith, and 3 a bout: H and the Balance modulator, containing two differential pairs of transistors with a cross collector connection, and a current heater connected via two adjustable transistors to the junction, SMHiTTeppB of each differential pair of transistors, characterized in that, in order to increase the suppression of carrier frequency signals and decrease sensitivity. to the variation of the circuit parameters, between the collectors of the transistor differential pairs and the input of the current generator included an additional differential amplifier.