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Super-regenerative Detector

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Papers » Principles of schematics etc. » Super-regenerative Detector
           
Dietmar Rudolph
Dietmar Rudolph
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02.Aug.11 14:13
 
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A super-regenerative detector circuit resembles very much to a regenerative detector circuit, and "only" the time constant of the grid leak CR combination may be different.

However, a super-regenerative detector is no longer linear in its behaviour. Therefore, an analysis in the frequency domain is no longer valid, and a time domain analysis is necessary. Furthermore, a frequency domain explanation leads to an incorrect conclusion.

The treatment starts with a conventional regenerative LC circuit.

In the article appended, super-regeneration is treated in time domain, and its feature so becomes clear.

Abstract

The superregenerative receiver as patented by Armstrong [10] is known for it’s ability to reach extremely high amplification factors with only one tuned circuit, greatly exceeding the amplification factors that are commonly reached by single tuned circuit regenerative receivers. This article is about exploring how superregeneration works. We will see that superregeneration is based on the development of free oscillations in the tuned circuit and has little in common with “regular” regeneration. A common simple explanation of superregeneration that is based on the idea of reaching an optimal regeneration level on average is analysed and proven to be incorrect. After analysing the implications of a continuous time dependent feedback function on the differential equations describing the tuned circuit, we will explore numerically what happens in a tuned circuit with superregeneration applied. As an important result we will see that the superregenerative tuned circuit is not bound by the well known amplification factor to bandwidth relation imposing a limit on the maximum amplification factor of a single tuned circuit based on the bandwidth requirements to receive modulated RF signals.

Exploring Superregeneration *)

Many thanks to Dipl.-Phys. Jochen Bauer who is the autor.

Regards,

Dietmar


Some practical experiments on superregenerative detector can be found here (in German).

*) revised edition 16.06.2012

einige, ein paar, etwas, ein bisschen, manche, irgendein, ziemlich, vielleicht ein, einige, manche, etwas, was, welche, irgendwelcher, irgendein, ungefähr, zirka, etwa, etwas, ein bisschen, viel [Some]

This article was edited 16.Jun.12 17:38 by Dietmar Rudolph .

Jochen Bauer
Jochen Bauer
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24.Jul.14 22:03

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In the previous paper, superregeneration was explored by numerically solving the differential equations governing a superregenerative circuit employing a linear feedback model. While this gives the reader some basic understanding of how superregeneration works, and in particular helps to understand the difference between "regular" regeneration and superregeneration, some more insight on an analytic level may be desirable.

This article here therefore takes a closer look at the superregenerative circuit using an analytic, non-numeric approach. By treating the superregenerative circuit employing a separate quench function generator as a parametric oscillator, well known methods for solving the resulting differential equations can be applied, resulting in  an approximate solution for the development of oscillation bursts in the circuit for a typical time-dependent feedback. From this closed-form solution, expressions for the frequency response curve and bandwidth as well as the amplification factor can be given.

 

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