[SI-LIST] Re: Query : RF Boards
- From: "Viklund, Per" <Per_Viklund@xxxxxxxxxx>
- To: Aditya Chandra <aditya@xxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 10 Feb 2012 09:21:22 +0000
If you want the list to assist, I think you need to give us a lot more details.
I've done PA's up to 144MHz on plain FR4 with good results so I know it can be
done.
Are you losing power on the drive side or the output side?
Are you sure the power is lost to losses or could you have gain problems with
the PA stage?
Is the circuit stable? -have you checked for harmonic oscillations?
Regards
Per Viklund - SM7IXF
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Aditya Chandra
Sent: den 9 februari 2012 17:16
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Query : RF Boards
Dear Sirs
?
We have been testing the 100W PA ?boards provided by you for last fortnight.
?
Unfortunately the performance is below the expected mark.
?
The PCB is a 4 layer PCB with Top Electric - GND - PWR - Bottom Electric as the
layer stack
?
It is 2 Oz on all layers and FR4 Tg170 material on all layers. Board Thickness
is 1.6 mm
?
The electrical connectivity appears to to be OK however the signal ?parameters?
and performance could not be achieved on this PCB.
?
After extensive testing and analysis we reached conclusion that the performance
deterioration is due to extremely high inter layer board capacitance. The
board?s die-electric capacitance is acting as a capacitor of very poor quality
on HF frequencies. Resulting in bypassing the RF signal in the region of 30Mhz
@ 12W per about 2.5-3 sq inches.
?
Is it because of PCB Material or any other possible issue.
?
Best Regards
Aditya
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