VSWR is greater than 10. What to do to make it less than 2 for a dipole antenna

[RF_Jim]

JIM

yes generally speaking when the dipole resonates, you get a characteristic impedance of close to 72 ohms plus reactive impedance of around 34 ohms as well. so when we check the resonance we are also concerned about the characterisitic impedance of the dipole. and if you don't normalize your impedance in the excitation, you should be able to see a appropriate results irrespective of the impedances you have entered in the boxes.

Regards

chachitoelflaquito, good observations, but, one finds 'in the field' (or lab) when sweeping a dipole in or at 'resonance' the 'reactance' component (phase angle) sweeps through zero degrees indicating no reactance but what remains is the resistive (Re or real) component.

A little background, I may be new to HFSS, but am not a stranger the field of antennas (RF) or to VNA and HP Vector Votmeter/impedance and Phase meter etc measurement techniques ... In past years more time has been spent with the EESOF Touchstone product (lumped components plus transmission-line based simulator like Ansoft 2D Designer) in prior years but HFSS 3-D FEM is a whole new ball game as far as providing 'insights' into structure resonances. It sure beats spending hours and hours at the antenna 'range' or time spent in the anechoic chamber (where one still cannot get a 'clear picture' of what is going on EM-wave wise).

Thanks for your input and help too. It takes cooperation today to work and become familiar with these new tools! BTW, I will be 57 yrs old this year. Started with TI doing defense work in '75 and first project was MLS (Microwave Landing System, with a 64 feed-horn array) at 5 GHz for FAA to replace aging ILS system (but of course, GPS has changed all that and MLS was never deployed).

Jim

 

[elchiquito]

It's an honor to Know someone of your status Jim.Respect!

i have been in this field for not so long.just few years of work in this field and now doctoral Research and i am not even half your age . So much Respect for your age and achievements . i am sure you have plenty to offer for youngsters like me.

About the reactive component i have mentioned the reason where and how we can reduce it in the prior posts.

Regards

 

[shaikss]

characterisitic impedance can be plotted using the same modal values,but this time you will be choosing z-parameters and then you plot IM and Re values of the Z-parameters.

Another point why do we not have half wavelength dipole rather than something less than half a wavelength. at half wavelength we see some reactance as well,inorder to minimize the reactance to zero we use a value less than that of the actual half wavelegth.

small tip,actually two
use more number of points in the sweep, you will see a smoothly curved plots

radiation patterns.i see you have an habit of having a scale of 0 to 180 in phi. its a good practice to have a scale of 0 to 360 degrees in both theta and phi plane. you will all the lobes minor major and side. and the step value make it 1 as well in radiation pattern for smoother curves.

Regards

Hi Chachito,

I have a query regarding modelling of antennas.
Let me explain my scenario.

I have an antenna at the transmitter end resonating at 865 MHz. Whatever the signals that are transmitted by the transmitting antenna via the free space are received by another antenna resonating at the same frequency. The received power is then fed to the rectifier circuit,
Is it possible to model the scenario like Tx. antenna transmitting the signals, including the free space loss and check whats the amount of power received by the Rx.antenna.
Is there any other way to model the same?

Thanks!

 

[elchiquito]

Salaam Shaikss

I have never done something similar to what you have asked,but i am sure there is a way of doing it .and i probably know how to do it. May be JIM can chip in as well.

So this is how i see it being done. so you draw your tx antenna,set up radiation boundaries. then then twice the distance away from the radiation boundary you draw your Rx antenna with feed and everything,this time your radiation boundary will be of typing absorbing rather than radiating. then i am for sure you will be able to calculate the power recieved at the RX terminal.

This is what i would do.but i am not sure if this is THE way. someone can definetly critique .

Regards
ChachitoEL

 

[shaikss]

How should we make the radiation boundary as absorbed in hfss?

 

[elchiquito]

I believe that will be done using Incident field option when setting up the radiation boundary.Saw an interesting ansoft article on this.check it out

**broken link removed**

Regards
ChachitoEL