SU459837A1 - Amplitude Detector - Google Patents

Description

one

The invention relates to radio engineering, can be used in radio devices that require signal detection in a wide dynamic range.

Amplitude detector is known that contains a transistor cascade connected in series with a common emitter, a push-pull circuit, an amplifier cascade, an emitter follower and a low-pass filter, and a nonlinear negative feedback element.

The purpose of the invention is to reduce the inertia of the detector - in the proposed amplitude detector a non-linear negative feedback element is connected between the output of the amplifier cascade and the junction of the emitters of the detecting cascade.

The drawing shows the functional scheme of the device.

The proposed amplitude detector contains a detecting cascade 1 on transistors 2 and 3 according to a common emitter circuit included on the push-pull circuit, an amplifier cascade on transistor 4, an emitter follower on transistor 5, a low-pass filter 6 and an element of nonlinear negative feedback-ez 7,

The detector works as follows.

In this detector, the effect of expanding the dynamic range of the detected radio signals can be obtained when two conditions are met:

Transistors 2-4 should operate in mode

-potentials at the outputs of the non-linear negative feedback element 7

must be the same.

With a small input signal and, therefore, a sufficiently low level of the rectified signal at the collector of transistor 4, this signal lies in the cutoff region of the current-voltage characteristic of a nonlinear negative feedback element 7. The current in the feedback circuit practically does not leak and, therefore, it can be considered open. In this case, the detecting

cascade 1 and the amplifier cascade on the transistor 4 together constitute a conventional “B.” class amplifier. With a sufficiently large transmission coefficient, such an amplifier amplifies very small signals.

level

As the input signal level increases, the non-linear negative feedback element more and more opens and the negative feedback more and more increases. it

results in a decrease in the gain of the amplifier and a linearization of its amplitude response, which occurs through non-linear negative feedback, compensating for the non-linearity of this response.

The emitter follower on transistor 5 serves to isolate the low pass filter 6 from the feedback circuit. As a result of this decoupling, the feedback is carried out along the harmonic components of the spectrum of the rectified signal, which leads to an improvement of the fronts and the height of the detected signal.

4 Subject of the invention

Amplitude detector containing series-connected detecting transistor cascade according to a common emitter circuit included in a push-pull circuit, an amplifying stage, an emitter follower and a low-pass filter, as well as an element of nonlinear negative feedback

connection, characterized in that, in order to reduce the inertia, a nonlinear negative feedback element is connected between the output of the amplifier cascade and the junction of the emitters of the detecting cascade.

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