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matching antenna to transistor amplifier - RF Cafe Forums
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| bamatom |
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Post subject: matching antenna to transistor
amplifier
Posted: Thu May 18, 2006 10:00 am
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Joined: Thu May 18, 2006
9:46 am
Posts: 3 |
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I have a general question how to match an antenna
to a self designed transistor amplifier. I want
to use a 2N4427 for 100MHz in common emitter configuration
(emitter directly on ground). The collector is connected
to 12V with via an inductor with a high inductance.
If I take the signal at the emitter, what output
impedance do I see? Is there a rule of thumb
how to deal with the transistors regarding to power
matching. If I look at the VSWR or S-Parameter
of my antenna, there is also a complex part. When
everyone talks about output impedance of the transistor,
there is always only a real number of Z mentioned.
Is there no complex part?
I guess this is
a very simple question and I am just confused. However,
an answer would very much help me to understand
the whole antenna matching to an amplifier topic
better.
-tom
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Dexter |
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Post subject:
Posted: Tue May 23, 2006 1:58 pm
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| Captain |
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Joined: Thu May 04, 2006
7:37 am
Posts: 7 |
Hello Mr. Bamatom, Your questions about transistor
are very basic, and are covered quite well by the
well-known Mr. Randy Rhea, in the last two editions
of High Frequency Electronics. Here is the path
for the 1st one. You can find the other on HFE website.
http://www.highfrequencyelectronics.com ... 6_Rhea.pdf
The simple answer to your question is that,
yes, for an amplifier (transistor) that has not
already been matched to 50 ohm, there will be both
a real and an imaginary part. Truth is, even with
a "50 ohm" device, it is almost certainly not purely
resistive. Read through Randy's two articles and
you'll have amuch better understanding, I guarantee
you. Dexter
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liw003 |
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Post subject: Re: matching antenna to transistor
amplifier
Posted: Sat May 27, 2006 8:03 pm
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Joined: Sat Apr 15, 2006
10:13 pm
Posts: 1 |
I am curious why you try to find the output impedance
looking from emitter since you use it as common
emitter. For me, I would care how to match the base
and collector port. Why VSWR is a complex number?
It should be the Amplitude of maximun voltage value
over minimun voltage value. I don't know where is
the complex part come from. And the reason why S-parameter
is complex value is that amplifier has equivalent
capacitance in side. S-parameter is define to descript
the intrinsic properties of a box. Now the box is
instead of an amplifer.
bamatom wrote:
I have a general question how to match an antenna
to a self designed transistor amplifier. I want
to use a 2N4427 for 100MHz in common emitter
configuration (emitter directly on ground).
The collector is connected to 12V with via an
inductor with a high inductance. If I take the
signal at the emitter, what output impedance
do I see? Is there a rule of thumb how
to deal with the transistors regarding to power
matching. If I look at the VSWR or S-Parameter
of my antenna, there is also a complex part.
When everyone talks about output impedance of
the transistor, there is always only a real
number of Z mentioned. Is there no complex part?
I guess this is a very simple question and
I am just confused. However, an answer would
very much help me to understand the whole antenna
matching to an amplifier topic better.
-tom
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Posted 11/12/2012
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