Development of a Low Profile Wide-Bandwidth Circularly Polarized Microstrip Antenna for C-Band Airborne CP-SAR Sensor

In this paper, a low-profile wide bandwidth circularly polarized microstrip antenna is

proposed as element for a C-band airborne circularly polarized synthetic aperture radar sensor. Several

bandwidth improvement techniques were proposed and implemented. In order to increase impedance

bandwidth, the antenna is constructed using double-stacked substrate with low dielectric constant,

modified radiating shape for multi-resonant frequency, and a circle-slotted parasitic patch. Generation

of the circularly polarized wave employs a simple square patch with curve corner-truncation as radiating

element. The asymmetric position of the feeding is attempted to improve the axial-ratio bandwidth.

To avoid a complicated feed network, the antenna is fed by single-feed proximity-coupled microstrip

line. The effect of copper-covering on the upper layer for decrease undesired radiation wave emitted by

the feeding is also studied and presented. Measurement results show that the impedance bandwidth

and axial ratio bandwidth are 20.9% (1,100 MHz) and 4.7% (250 MHz), respectively. Meanwhile the

measured gain is 7 dBic at the frequency of 5.3 GHz.