lossy materials

in CST MWS we have two types of material available. lossy and loss free.

i am wondering whats the use of loss free material ?

because in reality all material will be lossy so whats the purpose of giving loss free material version as well

in CST MWS material library

we have copper(lossy) and copper( loss free)

similaly we have FR4( lossy) and FR4 (loss free)


i will appreciate if any one can comment on the purpose of giving these 2 models of the same material or how we can use them affectively in our simulation study



regards

well not using cst for a bit i would speculate (particularly for metal) loss free is simpler to solve, therefore requiring less memory, but might not be the accuracy you require for all applications.

a perfect e (essentially loss less copper) versus copper with loss for instance would not require solving inside the copper for loss less but would for lossy.

One should always try to use lossless materials in computer simulations if possible since this greatly reduces the simulation times. For antennas and microwave circuits we are often interested in finding resonances. And the resonance frequencies are independent of the finite conductivity, that is, you won't see a shift in frequency if you introduce losses. However, if your interested in the efficiency (for example the antenna efficiency) then you have to take into account the losses.

hi

thanks to the people who commented on my question.
i agree with Jone that if you are only interested in the resonant frequency position than its better to sue loss free material for quick simulations

but what if i am interested in the impdedance bandwidth ( S11 <-10dB)

will it be affected if i use lossy and loss free materials?

looking for comments from anyone


regards

Yes, the impedance bandwidth will be affected. Losses tend to flatten out the resonance curves so that you obtain more bandwidth. However, most materials are low-loss and therefore you can still neglect the losses. Futhermore when you actually build your device you introduce losses that you little control over. So you always end up with more bandwidth (which often is a positive effect) compared to the simulated device.

To see how much influence the loss has, you can simply simulate a lossless structure and a lossy one and then compare. I almost always neglect losses in my simulations to win time. Only in some final verification I include the losses.

Hi,

It is useful to evaluate the losses.
For instance, you can ask whether or not is it worth to try to reduce the losses, and in that case whether in the conductor or in the dielectric. Lossless simulations can give you the answer as they give upper limits to the improvement.
Regards

Z

Hi

i agree with Jone .

losses changes the Q(qualilty factor) of the structure and hence the impedance bandwidth.

so if we are only interested in finding the resonant frequency position we can use lossless structure to reduce simulation time.

however if we want to find the accurate impedance bandwidth we need to use the actual lossy structure.

this is important for simulating antennas as the radiation efficiency and hence gain are reduced for lossy structures as compared to lossless case.

i hope people may find this information useful.

regards
shahid

May i know what are the actual application for loss free and lossy material in industry?
what i had learns that,electromagnetic wave had different reaction in both of them (loss free and lossy material)

agreeing with the above posts, lossless structures are useful for simulation only if u have to find the resonant frequency...like in the case of an antenna,,,the frequency where S11 is minimum,,,,losses are introduced into simulation strucutre to check with respect to the actual measurement paameters required....