loaded antenna simulation in CST

capacity loaded dipoles

Hello,everyone, How to simulate a resistively loaded or capacitively loaded dipole in CST MW v5.0? Never see an example till now.

Added after 1 hours 16 minutes:

Anyone help?Thanks!

making a loaded antenna

I think it should be simple (but I never tried it)
for example, if you want to simulate a loaded dipole just draw the metallic cylinder (the dipole) and then cut it and insert a lumped element with some resistance.

impedance resistively loaded dipole

Does it work? Thank you for your advice, I'll try.

capacity loaded dipole

Lumped port with resistance will do. I have tried it.

Hi,
I have done quite a lot of simulations with lumped network elements such as inductivities or capacities. It worked good but I had sometimes problems if the space for the lumped element was to small. E.g. the antenna radiator is 1m long and the lumped element only 0.1mm. I think the mesh then had problems to calculate that cell then. I just made it slightly bigger (about 10mm) and it worked fine.

To make a long story short, it should work.

Ciao

@purushottam
I need to load the antenna with "Wu-king" profile, that is to load the antenna at an equal intervals such that the resistance per unit length varies as a particular funtion of the position along the antenna. I want to not only load it at the port.

@adel_48
I tried it, but a problem appeared that the antenna always have an input impedance with capacitive reactance. Whereas before loading, the input impedance have capacitive reactance before a frequency point and inductive reactance after that frequency. I think it maybe cause by cutting the antenna, for the cut will always brings capacity, so I enlarge the cutted part, that is to say, enlarge the distance between the cut so as to bring a smaller capacity, but it didn't change much.

@elomatic
Can you upload some examples using CST MWS, e.g. resistively loaded antennas and capacitively loaded antennas?

To all:
Thanks for helps from all of you.

you can use microwave office

Are you sure that your design of the antenna is correct?

Since if you are using a dipole antenna, the parasitic capacitance should be very small. Wu-king profile tries to absorb the energy such that no power is reflected back due to end reflections, but it cannot compensate for severly unmatched antenna.

Also, how much is this capacitance? as long as you are using a dipole (even thick one) your capacitance will be very small unless you make very thin cut. So, try to think in implementing the antenna, what will be the resistors you will use , what is their length (it should be at least 2mm) and use this in the simulation. Due to the descrete distribution of the resistance, you will have some sort of resonance frequency at higher frequencies, you can move this resonance away from your band by increasing the number of resistors and thus approaching the continuous distribution.

hope this will help,
Adel

Yes, it do help. It's too hard to implement a very thin gap to realize an appropriate capacity, so I used lumped capacity, but the obtained result is still not very close to those have been present. Really thanks for help from all of you. It's the best place I have found to discuss and learning.