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Below spec power output issue with VCO & MMIC Amp - RF Cafe
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Below are the old forum threads, including responses to the original posts.
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Post subject: Below spec power output issue with VCO &
MMIC Amp Posted: Wed Apr 05, 2006 10:33 am
Joined: Wed Apr 05, 2006 10:32 am
I have built a 2-3GHz VCO and a MMIC based amplifier (both from
Minicircuits) for it separately on FR4 material with SMA connectors.
The VCO operates fine except that the specified output power should
be about 10dBm but I cannot get it to put out more than 0 or 1dBm. I
am using an HP8570 spectrum analyzer to make my measurements. The MMIC
based amplifier which is supposed to have a gain of atleast 10dB and
can put out a maximum power of greater than 13dBm also only increases
the VCO output by 1dBm, so the total output power I get from the VCO
and MMIC amplifier is not more than 3dBm. I have tried everything and
I am following the manufacturers design & datasheets and there doesn't
seem to be anything wrong I am doing. I spoke to Minicircuits and they
said they have not heard of this problem before and advised me to buy
a new VCO and MMIC amplifier unit and try again. Can anyone help shed
some light on this please? I am really stuck here!
Post subject: Posted: Wed
Apr 05, 2006 12:32 pm
Joined: Mon Jun
27, 2005 2:02 pm
To me it sounds like you have a matching problem between the VCO
and the MMIC.
I suggest that you will test each of them separately.
You already mentioned that the VCO doesn't output the required power.
Few questions that comes to my mind:
1. Have you placed
coupling capacitors between the VCO output and the MMIC input?
2. In the final circuit (With the VCO and MMIC cascaded) have you
used a pad between them?
Post subject: Posted: Thu
Apr 06, 2006 11:47 am
Joined: Wed Apr 05,
2006 10:32 am
Thanks for your reply IR. The problem
was with my SPectrum Analyzer or the way I was reading it. I tested
my VCO & Amp with another analyzer I had access to and the circuits
were performing as per spec! Thanks for your help anyway!