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How do I short circuit? - PCB with LNA

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brmadhukar

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How do I short circuit?

Hi,
I have a PCB with LNA connetcted to RF downconvertor at 1575MHz. Now I do not need this LNA. How do I short circuit this LNA. The input and output points are directly opposite. The board is a six layer board with FR4. Can I just use some capacitor to reduce the cabling or just use cabling?

B R
 

eep2nw

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I'd use some copper tape to do the trick. It's a cheap and effective method, but not one to use for final designs.
 

egemini

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Hello
Its better you should use a low loss coaxial cable to interconnect.
Other methods may cause impedance mismatch.
thanks
 

flatulent

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remove parts

You will also have to remove the first and last part of the circuit so that the amplifier is not in parallel with the transmission line. Also, connecting the input to the output will cause it to oscillate.
 

Bagster

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DO NOT short this device out with copper strips. The bias connnections are more likely to still be in place and you will damage the PSU. The capacitor shorting is by far the best method. Use a 47Pf cap to start with. The device cannot oscillae because it will be missing. you may have mis-matching and this could potentially cause ripple. Your conversion gain & NF may be affected depending on the signal level into the down convertor.


Bagster
 

toonafishy

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I would use semi-rigid coax to connect input to output. It is easy to work with and would have very little loss for this short length.
 

g579

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1. You should use some series capacitors or should remove biasing the LNA.
2. At about 1500 MHz a few millimeters of length of a 50 ohm strip will not cause any problem (as I guess your LNA is a matched one).
 

jwei363

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re

remove LNA first,
connect LNA in/out with a cap.
1500M is not so high.
 

dd21

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cut those traces for the output biasing and input biasing. The stubs may cause problems at 1.5 GHz.
 

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