need help in calculating the gain and radiation pattern

Hello,
I am vishal from India
i need your help.
could anyone please teach me how to choose the appropriate value of theta and phi so that i can plot the gain, directivity and radiation pattern.
i will be very thankful to you.

Regards

Vishal

Hello,

To select the right values, you need at least to tell us something about your antenna, its orientation in 3D space and what you want to see (for example main beam, or side lobes). Also the scaling (dBs, dBs/div, Efield linear, power linear) and type of plot (polar 2D, 3D, rectangular, etc) can be of importance.

Hello Sir, Thanks for replying
Actually I am working on a paper i uploaded that paper so i have simulated that design using HFSS.
S(11) parameters has been matched almost but i dont know how to plot gain and radiation paper as it is given in the paper.
so please sir teach me how to plot these parameters.
i am going to upload that design with paper.

Regards
Vishal

Hello,

Do you have problems with how to interpret the radiation patterns in figure 4, or do you have some problems with how to use HFSS?

actually I am new to antenna field and working on it for last 6 months only so i need to learn many things.
I want to plot figure 4 and figure 5. but for plotting these figure i dont know for what values i should select the values of theta and phi.
i think i dont have any problem in using HFSS.

Does this plot help? It shows how theta and phi are measured.

yes surely it helped me.
so it means that i have to vary the values of theta and phi to check that at which point the gain is high.

For the peak gain, yes.

Your antenna is with its PCB in the YZ plane (figure 1 in the document). I use same theta en phi definition as in the figure posted by volker_muehlhaus. Note that when you search the web, you find definitions where theta is the angle in the XY plane.

# Figure 4, a, X-Z plane (shows the E_theta and E_phi fields).
The measuring antenna (assuming that the DUT is standing still), moves from the positive z-axis (theta = 0) towards the positive x-axis (theta = 90, phi = 0). It rotates further towards the negative z-axis (theta = 180, phi = 0). It keeps moving to the negative x-axis (theta = 270, phi = 0) until it reaches the positive Z-axis again.

This is an elevation radiation pattern as the measuring antenna moves in a vertical direction. One could also do an elevation pattern measurement in the Y-Z plane. This is with phi = 90 and theta varies from zero to 360

In elevation patterns, phi is a constant, and theta varies.

Polarization:

For E-phi, the measuring antenna has orientation so that it receives E-field with its polarization parallel with the phi direction. Phi goes from the x-axis to the y-axis (when theta = 90, or elevation = 0). If you use a dipole for E-phi measurement, the dipole is with its bar or wire parallel to the y-axis. You can see this as horizontal polarization over earth.

For E-theta, the measuring antenna is oriented parallel with the theta direction. When using a dipole and under small elevation (that is theta about 90 degrees), the dipole has vertical orientation, you can see this as vertical polarization. When theta = 0, the dipole is exactly parallel to the x-axis.

# Figure 4, a, X-Y plane (upper right graph)
Here theta = 90 degrees (elevation = 0). The antenna moves from the positive x-axis (phi = 0, theta = 90) toward the positive y-axis (phi = 90, theta = 90). It rotates further towards negative x-axis (phi = -180, theta = 90). It completes a full revolution via the negative y-axis (phi = -270, theta = 90) until the measuring antenna reaches the positive x-axis again.

E-theta is vertical polarization (antenna along theta direction), E-phi is horizontal polarization.

In azimuth patterns, theta is a constant, phi varies. One can also plot azimuth patterns under certain elevation.


You may play with phi/theta values for a known antenna (for example a HW dipole along the Z-axis, Y-axis and X-axis) to make sure you understand the definition in HFSS.

thank you i am working on your reply.

To WimRFP:
if i have an antenna structure in the xy plane, does the E-field in the z- direction?
and according to that the E-plane is taken to be either xz plane or yz-plane?
H-plane is the xy-plane?
is that correct?
thanks

I hope I understand your question correctly.

If you have an antenna structure in XY plane (without dielectric layers), it means you can't have current component in vertical direction (Z direction). That means you can't have vertical polarization under zero elevation angle. In other words, you can't have E-field in theta direction for theta = 90 degrees.

A half wave dipole with its orientation in Y direction, produces its strongest far field in the XZ plane. The E-field vector is perpendicular to the XZ-plane. There will be no vertical polarized component in the XY plane. In other words, E perpendicular to the XY plane is zero.

Though the antenna radiates in Z direction, there will be no E-field component in Z direction for theta = 0 (as in the far field both E and H are perpendicular to the direction of power flow).

Hi WimRFP,
whatever you say i understand that, but i have refered many paper in that For E field co & cross polarization (means vertical & horizantal ) are plotted in same graph.For H field the same way. as im following your procedure im getting 2 different graphs.
plz tell me where im wrong ?

thanking you in anticipation

In the far field, H and E follow the plain wave relation (E/H=377). So for a single propagating wave, there will be an E and H component, with 90 degr between them (in space) and they are in time phase. To determine the power density of that wave, you can use E or H, als long as the orientation of the sensor is correct. Results for both methods should be the same. If you don't want to figure out the polarization, you can use "total E-field" or "total H-field" in simulation.

In real world two waves may propagate (best example circular polarization). The actual field is the superposition (in both space and time) of two linearly polarized waves. So you are right that when determining cross polarization, you can use E or H for it (as each wave has fixed E/H relation). Results (graph) should be the same, as you mentioned.

However when you plot (for example) Etheta and Htheta, or Ephi and Hphi you will get different graphs. Yo can check this yourself with a dipole.

hi, I have just started my work on this field...now I am developing the theory on antennas and as well as also tried to use hfss.Though i am successful in designing some antennas but cannot getting my concept on how to calculate the radiation pattern, gain etc. From your point of view aru you going to tell that it is not possible to calculate gain, rad. pattern etc. when the designed antenna in XY-plane. And also plz tell me what are the proper values of theta and phi to be used to calculate an antenna gain?

thanks...waiting for ur reply...