Miniaturized VHF/UHF Dual-Band Circularly Polarized Four-Element Sequential-Rotation Array Antenna Based on Alternately Overlapped Bent Radiation-Coupled Dual-L Antenna Elements

This communication presents a novel miniaturized circularly polarized (CP) very high frequency/ultrahigh frequency dual-band four-element sequential-rotation array antenna for SATCOM applications. The dual-band operation is realized by using radiation-coupled dual-L antenna as the array element. Four elements are bent and alternately overlapped in a sequential-rotation manner, which effectively reduces the array antenna's size while ensures that elements do not touch each other to maintain dual resonance. This results in a compact design which makes better use of the limited space to achieve good performances. Furthermore, since it does not rely on dielectric materials, particularly high permittivity materials, to reduce the resonance length, the proposed array antenna is both lightweight and low cost when compared with conventional miniaturized CP antennas operating at similar frequencies and having close performances. A prototype working at 295/355 MHz is designed, fabricated, and measured, whose weight is 786 g and effective size is 0.197λ × 0.197λ × 0.068λ at 295 MHz. The measured bandwidth of the main body for active reflection coefficient ≤-9.5 dB is 5.6 MHz (1.9%) and 7.2 MHz (2%) for the lower and higher bands, respectively. The measured gain, axial ratio, and efficiency of the proposed array antenna are better than 4.5 dBi, 1.15 dB, and 71% within ±2 MHz bandwidth for both bands.