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Help - Need design info for Transistor Frequency Multiplier? - RF
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RF Head
Post subject: Help - Need design info for Transistor Frequency
Multiplier? Posted: Mon Jun 08, 2009 7:42 am
Captain
Joined: Mon Feb 09, 2009 12:26 pm
Posts: 11
Can anyone suggest
any good source(s) for design information re: Transistor Frequency Multipliers?
In particular I need some information to help me build a frequency
tripler with an output at around 900 MHz.
Steve
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nubbage
Post subject: Re: Help - Need design info for Transistor
Frequency Multiplier?Posted: Tue Jun 09, 2009 2:57 am
General
Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location:
London UK
Hi Steve
Sorry I cannot contribute any sources, but
for what it is worth, my approach would be a conventional common emitter
balanced amplifier using two transistors and a 3dB hybrid at 300MHz,
then a resonant output balanced circuit at 900MHz. Over-driving the
two bases will ensure plenty of third harmonic, and most of the second
harmonic will cancel in the push-pull balanced amp.
Quantifying the
level of 3rd harmonic, and how to design the input, output and biasing
will require a text book or an article, but that is the fundamental
approach I would look for.
_________________
At bottom, life
is all about
Sucking in and blowing out.
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RF Head
Post subject: Re: Help - Need design info for Transistor
Frequency Multiplier?Posted: Wed Jun 10, 2009 3:08 am
Captain
Joined: Mon Feb 09, 2009 12:26 pm
Posts: 11
That's definately
worth considering. However, I only have a 2V5 supply rail and need to
keep current as low as possible. On top of all this I have next to to
design space!
I have tried a simple class C, CE stage with a
simple resonator as the collector load. This is then light cap coupled
out. Early results look promising.
I have also thought about
approaching this as a harmonic termination problem. The idea being to
pesent short circuits to the sub harmonics and an open circuit to the
wanted 3F. End result should be square wave flavour and hence rich in
3F. First attempt was not great. Wait and see.
Steve
Top
nubbage
Post subject: Re: Help - Need design info
for Transistor Frequency Multiplier?Posted: Wed Jun 10, 2009 6:45 am
General
Joined: Fri Feb 17, 2006 12:07 pm
Posts:
218
Location: London UK
Hi Steve
A series resonant circuit
at 2*f is the approach used in varactor triplers too. In fact you might
profit from using a 2GHz transistor in an unconventional way with no
power supply, just using the collector base capacitance as a varactor,
driving the base, and using a matching circuit between the collector
and the output BPF at 3*f, then place a 2*f series resonant trap from
collector to ground, with no supply at all. You save on space taken
by supply choke, bias resistors, and decoupling cap.
See what happens.
The loss might be 3dB but that is no big deal if you have enough drive
power.
Let me know how it goes.
_________________
At bottom,
life is all about
Sucking in and blowing out.
Posted 11/12/2012
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