# Volume loss density in HFSS?

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#### dopplerjeff5000

##### Newbie level 5
Hello,

I see the volume loss density in HFSS is defined as...

ρ=Re[E•J+jωB•H]

Where does this come from? I suspect it comes out in the derivation of the Poynting vector, but I haven't seen this form in the derivations. If anyone has derived volume loss density in this form I'd be interested in seeing it.

#### dopplerjeff5000

##### Newbie level 5
Hi,

I'm bumping the thread because the matter remains unsolved. Derivation of volume loss density from Maxwell's equations yields ρ=σE, while HFSS shows it as in the original post. Any input on where the magnetic part comes from? Is it just the magnetic current component?

#### dopplerjeff5000

##### Newbie level 5
I thought I could bump my own post since it has not been answered and over 600 views. There is obviously interest in the topic. That said, I leave it up to you. Just let me know if you should delete it or if I should delete it.

#### FvM

##### Super Moderator
Staff member
I prefer to rate your post as additional question rather than not permitted bumping...

- - - Updated - - -

I meant it's O.K to add a question, and I think you did.

dopplerjeff5000

### dopplerjeff5000

Points: 2

#### PlanarMetamaterials

Where does this come from? I suspect it comes out in the derivation of the Poynting vector, but I haven't seen this form in the derivations. If anyone has derived volume loss density in this form I'd be interested in seeing it.

I think your guess is correct.

The real part of the time-dependant Poynting Vector is

p(t) = Re{E.J + H.M}, which since M = jwuH is equal to Re{E.J + jwuH.H} which is Re{E.J + jwB.H}

dopplerjeff5000

### dopplerjeff5000

Points: 2

#### dopplerjeff5000

##### Newbie level 5
I think your guess is correct.

The real part of the time-dependant Poynting Vector is

p(t) = Re{E.J + H.M}, which since M = jwuH is equal to Re{E.J + jwuH.H} which is Re{E.J + jwB.H}

It is encouraging to see your answer! Taking it a step further, I know that jwB•H can be interpreted as the curl of E•H. But is this quantity significant? The J•E term can be interpreted as power lost to heating, but what about the other term?

#### PlanarMetamaterials

Remember that HFSS deals with magnetic sources, or if you prefer, magnetic conductivity or magnetic charges. These quantities are realized in places such as Perfectly Matched Layers (PMLs) or the Magnetic Current Source Excitation. While these don't *technically* exist in real life, (and therefore we say M = 0), HFSS uses these values as "shortcuts", and therefore needs to take them into account.

#### Song Wong

##### Newbie level 3
Remember that HFSS deals with magnetic sources, or if you prefer, magnetic conductivity or magnetic charges. These quantities are realized in places such as Perfectly Matched Layers (PMLs) or the Magnetic Current Source Excitation. While these don't *technically* exist in real life, (and therefore we say M = 0), HFSS uses these values as "shortcuts", and therefore needs to take them into account.

I also want to know where the equation comes from? Do you have the references? which papers or books?

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