insertion loss and return loss

[mankan]

Hi all,

In PCB or in EM field, if insertion loss is 3db, what does that mean. is it 3% of the signal are lost because of the insertion of a device?

Similarly 4% of return loss means what?
More the return loss os good?

Can anybody tell me?

Mani

 

[IanP]

Depends on what you're measuring as a ratio (power, voltage, loudness), for the most part you're probably referring to power ..

A 3dB gain is 2 times the gain, a -3dB is the inverse loss -> that is 1/2 the power ..

Here're links that are helpful:
https://www.gcaudio.com/resources/howtos/voltageloudness.html

See Signal Integrity at:
**broken link removed**

IanP

 

[FvM]

dB isn't related to percent. It's a logarithmic measure for voltage (or current) and power ratios. To mention a more basic explanation:
https://en.wikipedia.org/wiki/Decibel

More return loss is good, generally. In most cases (exept for antenna matching or in the microwave field), good return loss values are 20 dB or above.

 

[Amithsleek]

Hi Mani,

3db is not in the terms if percent, it is in the terms of power where the signal power is lost.

4% return loss is good but more return loss leads to more miscommunication.