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
Joined: Mon Jun 27, 2005 2:02 pm
it sounds like you have a matching problem between the VCO and the
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
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