Continue to Site

# Active Z and Z parameters inHFSS

#### Plzzahut

##### Newbie
Could someone explain the difference between Active Z and Z parameters(also 2 S parameters)

In my design, two lumped ports activate together in order to generate an E field and those 2 ports have a phase delay.

so what if I want those 2 ports' input impedance to be 50 ohms in oder to use coaxial cable to feed in.

I want to let the device work at 100Mhz, if I look active Z(1:1) and S(1:1) parameters, all stuff looks ok.

But if I use Z and S parameters, The Z(1:1) goes to 70 ohms and the impedance peak is at 120Mhz.

I'm so confused.

Shall I look at Active Z?

#### PlanarMetamaterials

"Active" parameters take into account multiple excitations, whereas typical parameters are only concerned with one.

What kind of device is it?

#### Plzzahut

##### Newbie
"Active" parameters take into account multiple excitations, whereas typical parameters are only concerned with one.

What kind of device is it?
briefly speaking it is a device with 2 metal plates that works as a capacitor. Between them is the very high e field which I need.
One lumped port connects to the positive plate and the other to the negative plate.
And they share the same ground plane which is the outside housing.
In practice, the metal plate is connected to the N connector's needle, in simulation I connected the plates and housing together.
Since those lumped ports excite together and one has a 180-degree phase delay, so do active parameters represent each ports' own characteristic when both ports excite?

#### PlanarMetamaterials

The active parameters will take into account the excitations of the other port, yes.

As to which set of parameters you want -- it really depends what information you are looking for. What are you trying to determine with this simulation?

#### fereshteh

##### Member level 1
Could someone explain the difference between Active Z and Z parameters(also 2 S parameters)

In my design, two lumped ports activate together in order to generate an E field and those 2 ports have a phase delay.

so what if I want those 2 ports' input impedance to be 50 ohms in oder to use coaxial cable to feed in.

I want to let the device work at 100Mhz, if I look active Z(1:1) and S(1:1) parameters, all stuff looks ok.

But if I use Z and S parameters, The Z(1:1) goes to 70 ohms and the impedance peak is at 120Mhz.

I'm so confused.

Shall I look at Active Z?
In HFSS, you can see the passive and active S/Z-parameters. In a multi-port devices, when you ask for Z-parameters, e.g. Z11, HFSS will only enable port 1 and assume all other ports are matched. Thus you'll only see the passive Z-parameters. While for active Z-parameters, HFSS will give you the results by taking into account the effect of mutual coupling with other ports. Hereon, HFSS will see what is the magnitude at other ports (1W or 0W). (0W is matched load,1W must be considered.