The HP sceme in the patent refers to an array of series and parallel
diodes to reduce noise.
Just paralleling them does not reduce the noise!
Might this not depend what the type of noise was ?? JRC use this technique
in the RF stage of their receivers but I am wondering if this is only valid
for Gaussian noise?? the faulty diode looked anything but Gaussian. Is
there a situation here where we are not consider noise power which should
add(??) but in the case of the JRC receiver S/S+N ......maybe C/C+N (
:-)) ) i.e it is the effect of the noise on the total capacitance in terms
of the "FM noise" it produces??
The commonly called Zener diodes will work, all diffused diodes have an
approximately square-law voltage capacitance relationship. Avalanche diodes
("zeners" above 6v Vbr :-)) ) are made with big junction areas so can give
high capacitance. The lower the breadown voltage, the narrower the depletion
layer so the bigger the static capacitance. However the surfaces might not
be so well controlled as diodes intended for RF use. The noise demonstrated
was probably a surface state effect rather than a bulk defect.
Alan
G3NYK
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