Abstract
:
An analysis
of tnmel-diode low-level detection is presented for the purpose of explaining
some of the unusual detection characteristics that occur under certain hias
conditions. For example, in the vicinity of its inflection hias point, a tmmel diode
exhibits a discriminator-like rectification behavior with two sensitivity
peaks. When biased at one of these peaks, the diode is capable of unusuaUy high
sensitivities, at least an order of magnitnde better than the sensitivity of
any other known diode. It is shown that these high sensitivities are
proportional to (1 J?z),where P is the RF power gain of the detector viewed as
a reflection-type amplifier. The resultant gain bandwidth (or sensitivity
bandwidth) limitations of the detector are discussed. UnusuaUy high sensitivities
are also possible at the lower microwave frequencies when the tunnel diode is
biased at its peak current point. A knowledge of the diode static characteristics,
the reflection coefficient, and the video circnit permits an accnrate
analytical evaluation of the sensitivity performance of any tunnel diode, and
calculations are carried out for an example diode and compared against measured
data. The paper also contains a speeific comparison of the relative sensitivity
performance of the example tnnnel diode versus a hot carrier diode.
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