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Below spec power output issue with VCO & MMIC Amp - RF Cafe Forums

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mirza_ss
Post subject: Below spec power output issue with VCO & MMIC Amp Posted: Wed Apr 05, 2006 10:33 am

Lieutenant

Joined: Wed Apr 05, 2006 10:32 am
Posts: 2
Hi everyone,

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!

Thanks!

Shafique


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IR
Post subject: Posted: Wed Apr 05, 2006 12:32 pm

Site Admin


Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello Shafique,

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?

_________________
Best regards,

- IR


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mirza_ss
Post subject: Posted: Thu Apr 06, 2006 11:47 am

Lieutenant

Joined: Wed Apr 05, 2006 10:32 am
Posts: 2
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!

Thanks
Shafique



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