Take, for example, the case of an AUT configured to receive a right hand circularly polarized (RHCP) signal and illuminated by a left hand circularly polarized (LHCP
) signal for the purpose of evaluating axial ratios.
Here [[alpha].sub.1,[theta]] and [[alpha].sub.2,[theta]] are power distribution of RHCP component and LHCP
can be achieved for the antenna with the same configuration as Figure 1(a).
The simulated and measured normalized LHCP
and RHCP radiation patterns in the XZ-plane and Y Z-plane for frequency of 5.83 GHz are shown in Figures 9(a) and (b), respectively.
This modulation is performed by switching an RF carrier between two antenna ports for transmitting LHCP
and RHCP waves.
At angles near zenith, RHCP is reflected as LHCP
. In the situation of double reflection, it is complex since there are two reflectors.
While port 1 exciting Left Hand Circular Polarization (LHCP
) radiation at the positive Z-axis, port 2 generates LHCP
at the negative Z-axis.
When observing an RL antenna radiation there is no way to discern the polarization angle from the response or the sense (RHCP or LHCP
Figures 16 and 17, respectively, show the results of the LHCP
gains and RHCP gains of the 1 x 2 linear array and the 2 x 2 array in the boresight direction.
3(b) shows the simulated RHCP radiation pattern and the cross-polarization (LHCP
) for two orthogonal planes, the azimuth plane and the elevation plane.
Also the measured results show that the cross-polarization level (LHCP
) is lower than the co-polarization level (RHCP) by more than 20 dB at the broadside direction, which is due to the fact that the probe-fed horizontal rectangular strip can provide the necessary capacitive reactance to compensate the inductive reactance caused by the vertical probes.
It is clear that the antenna is RHCP with a small LHCP
level of -27.2dB in both the principal planes.