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

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


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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