RF TRANSMITTER LAYOUT - RF Cafe Forums
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Post subject: RF TRANSMITTER LAYOUT Posted: Fri Jul 25, 2008 2:45 pm
Joined: Sun Jun 22, 2008 3:57 am
i am a beginner to CAD. i have designed a layout for a rf video tx circuit. i am enclosing the schematic and layout. please tell me if there are any errors. i used a longer trace to connect L2 to T1. will it have any effect on L2 inductance? please give me suggestions on how to make it better. [img][img]http://img93.imageshack.us/img93/7151/rflayoutsd4.th.jpg[/img][/img]
Post subject: Posted: Mon Jul 28, 2008 5:46 am
Joined: Fri Feb 17, 2006 12:07 pm
Location: London UK
A track length of about 35 mm and 0.5mm wide (estimates from your pdf file) will add about 0.4 microhenry to L2.
I gave you an extensive reply to this design on June 30th. Was this understood and followed?
Essentially, all of the RF side of the circuit should be ground on both sides of the PCB, with pads for components. Conventional LF electronic layout, as done by software, leads to many problems at RF. Much of this is due to narrow track widths give rise to higher radiated fields and so increase the RF coupling into parts that should not be coupled to. Thus the true schematic model with narrow tracks would have many many mutual inductances that give rise to spurious genrated frequencies. Best avoided.