To improve the performance of the antenna such as gain
and AR bandwidth, sequential feeding network technology[7]
is applied for the application with the four same CP patch
antennas arranged as shown in Fig.2(a), where all patched are
placed at same spacing at vertical or horizon direction, FJ, Fz,
F 3 and F 4 are feed point where each of the elements is excited
in the same amplitude and 900 phase delay in an anti-clockwise
sequence. There are several concrete implementations such as
parallel feeding network, series feeding network and hybrid
ring parallel feeding network[8]. Among these, the parallel
feeding network is applied in this paper for the simplicity and
ease of implementation shown as Fig 2(b), where Zp is the input
impedance of the element and Zin the impedance of the feeder.
Meanwhile AgO is the waveguide wavelength of the micros trip
transmission line and h,lz are the adjustable lengths to fit the position of the feed points.