Well, I always assume it is negative for passive devices. That way it works with the math. Lets say I have a reflection coefficient of |ρ|=0.2. I would then say the return loss was 20*LOG(0.2)= - 14 dB. also if I look on a network analyzer, the return loss will be plotted as minus dBs...i.e. below the 0 dB line. A marker on an agilent network analyzer will read "- 14 dB".
I know the word "loss" gets some people, but the convention seems to be this way for that last 40 years or so.
Well, I always assume it is negative for passive devices. That way it works with the math. Lets say I have a reflection coefficient of |ρ|=0.2. I would then say the return loss was 20*LOG(0.2)= - 14 dB. also if I look on a network analyzer, the return loss will be plotted as minus dBs...i.e. below the 0 dB line. A marker on an agilent network analyzer will read "- 14 dB".
Return Loss is wrongly expressed as a negative quantity these days. The parameter S11 is negative while return loss is positive. Literally speaking, a negative loss will be a gain. One never says 'I suffered a loss of -$100'.
The "LOSS" in RL is how I justify this confusion.
If you send a signal in to a port, and you measure the reflection of that signal you should never
get a signal that is Greater then the original signal. so (Pin/Pr) will be > 1, or if you say (Pr/Pin)
you will get the VNA values of -RL.
Thanks for the answers. For active devices, what does the negative return loss mean? It means that the reflected wave is stronger than the incident wave?
For this IC chip: https://datasheets.maximintegrated.com/en/ds/MAX2830.pdf
on page 11, it gives a negative curve. The reflect wave is stronger?
Please clarify this for me.
Thanks for the answers. For active devices, what does the negative return loss mean? It means that the reflected wave is stronger than the incident wave?
For this IC chip: https://datasheets.maximintegrated.com/en/ds/MAX2830.pdf
on page 11, it gives a negative curve. The reflect wave is stronger?
Please clarify this for me.
For active devices, a negative return loss in dB is possible, but this indicates an unstable situation. ( **broken link removed** )
In this particular datasheet, I think that it might just be a typographical error that someone has missed. The specifications table on page 3 does indicate positive return loss values.