Analysis of electrically large patch phased arrays via CFDTD

Abstract

To validate the CFDTD code, analysis was first carried out on a smaller array with 64 elements. The structure was built up with elements identical to those used in the 10,000-element array. Models of the validation array were constructed using both CFDTD and XFDTD. The array radiation patterns were shown for 0/spl deg/, 30/spl deg/, 45/spl deg/, and 60/spl deg/ scan angles at the center frequency of 1.75 GHz. The beam was scanned in the /spl Phi/ = 90/spl deg/ plane. The solid lines represent CFDTD data while the dotted lines indicate the corresponding XFDTD set. As the beam is steered away from boresight, the 3-dB beamwidth increases from 12.9/spl deg/ at boresight to 26.2/spl deg/ at the 60/spl deg/ scan angle. The first sidelobe level is about 13 dB below the peak when the main beam is pointed at boresight. The total change in peak sidelobe level is 4.0 dB as the beam is scanned from boresight to 60/spl deg/. The array directivity calculated with CFDTD is 23.0 dB, which is within 0.2 dB of the value given by XFDTD. Furthermore, the scan loss from 0/spl deg/ to 60/spl deg/ is observed to be 3.0 dB with CFDTD and 2.8 dB with XFDTD. These values are consistent with expectations for a well behaved array with 0.5/spl lambda/ element spacing.