It is mostly true

CST does not include these changes in its simulation.

therefore, you should first get your material parameters and then make new material and in the conductivity part you should set an appropriate model for tangent delta el. according to your material properties at your defined frequency.

thanks amir Hossein.

for example for RT Duroid 5880 the tangent delta is 0.0009. but in wide band specially in ku band and ka band, i think i should prepare a xml or text file that define the variation of tangent delta according to frequency and load the file in material properties.

Dear Behrouz,

True.

We should indeed consider Re and Im components.

Best wishes

that is correct.

I have done this with HFSS for FR-4 substrate

But i am not fully familiar with CST.

although i think it is the same process

In the book by J. Grigas "Microwave Dielectric Spectroscopy of Ferroelectrics and Related Materials (Gordon & Breach Publishers, USA) you can find a lot of examples when the tangent of losses increase with the frequency at microwaves and millimeter waves and the reasons why?

Yes. The lossy characteristic of material vary with frequency and it should increase in consideration with the decrease in penetration depth and resistive path bound to increrase

Dear Sir,

I thin this is a problem of a material. If you have a magnetic loss material, so the tangent delta will be increase over the frequency.

YourS Sincerely

In general the losses increase with frequency especially at higher bands. Some materials show very high loss at certain bands of frequencies. Therefore, wideband designs should consider these facts.

The permittivity of many substances changes not only with frequency and temperature, but also with specimen age and history. In general,  the magnitude of the tan delta numbers increase as the frequency decreases, the lower the frequency (f), the higher the tan delta number. For the EM simulators, you should define by yourself the actual relation of  variation of losses tan angle and the frequency. In practrice the change is important only in a wide frequency range. the important you chould definr by yourself this relation and you shoul make several simualtion depending on the multiple band where the tan can change.

Basically loss tangent (tan(delta) is the ratio of reactive part of dielectric constant to real part of dielectric constant. It does change with the frequency. As the frequency increases losses also increase. For ideal case loss tangent should be zero. In other words dielectric constant should have real part alone (ideal case).

Hi all,

As usual, the dielectric properties of the substrates are typically given at lower frequencies by the manufacturer.

Yes, the losses and the effective permittivity increase with frequency.

To improve design accuracy (and involve this behaviour) of electromagnetic (EM) tools such as CST, ADS,….. the permittivity and the losses must be characterized in the considered frequency band of operation..

In another hand, the ceramic substrate, such as alumina, usually offers low dielectric loss and high dielectric constant, allowing the fabrication of compact millimeter wave circuits.

In LNTs loss tangent decreases with increase in frequency?

tan(delta)= 1/(2*pie*f*C*R)

ie., tan(delta) is inversely proportional to the frequency

so, as frequency increases the loss tangent decreases.

Hi,

Google "Universal dielectric response" and "Jonscher's law." Most amorphous materials have a loss tangent that increases with frequency.