PhaseCenterComputationofaCorrugatedHorn

Phase Center Computation of a Corrugated Horn
Phase center computations are a very sensitive subject and difficult to measure. The location of the phase center depends upon a couple of parameters such as polarization direction, scan angle direction and aperture width. The device modeled in this application is a cylindrical corrugated horn with a linear vertical polarization, depicted in Figure 1.
Figure 1:The CST MWS model showing the excitation direction and the definition of H- and E-Plane
Correct settings are crucial in order to obtain meaningful results. The polarization of the E-field is along the E-plane (vertically orientated). Figure 2 shows the E-phi component in a three-dimensional view. It can be seen that this field component is very
Figure 2:Field and H-plane scan direction settings
shows a rather flat phase regime for a certain aperture angle. In Figure 3 the farfield center is repositioned for three different locations, first, at the phase center and second, +/-5% of the total horn length repositioned on the propagation z-axis.
Figure 3:Three locations are defined for further recording of the phase variation
Figure 4 shows the 3D phase plot of the E-field for the various positions
Figure 4:From left to right: Phase center shifted by +5%, at center and -5% away from the optimal phase center
Figure 5:Phase variation along the H-Plane
The position of the phase center varies according to the aperture angle
rather small as shown in Figure 6. Note, that in general, the phase center
standard deviation is another critera to estimate the accuracy of the phase center computation, depicted in Figure 7. Figure 6:Movement of the phase center as a function of the considered aperture angle
Figure 7:Smaller aperture angle result in smaller standard deviations
Comparison to measurement: The measurements were carried out by Kathrein frequencies, +/-2% offset from center frequency, the phase center was
Figure 8:Actual phase center postion of the corrugated horn
Figure 9:The deviation is shown for two different frequencies. Note that the phase center varies with frequency。