A low sidelobe planar X-band antenna array with air coaxial feedline

A low sidelobe array antenna is investigated to provide a low-cost and effective solution to radar applications. This antenna array consists of 256 radiating elements divided into four subgroups of 64 elements each, and fed by a rectangular waveguide feed network. The feed structure of the proposed radiation element, which is basically a novel air coaxial-fed pyramidal horn array with shorting termination, can be realized by self-supporting feedline network and with low losses. Low sidelobe design is conducted according to the synthesized amplitude distributions with a number of unequal power dividers. The test results show that measured impedance bandwidth for voltage standing wave ratio(VSWR) less than 2 is within 0.5 GHz, with a relative bandwidth of 7.5%; the measured gain is 30 dB at the center frequency, while it is higher than 29.5 dB at a frequency band of 0.2 GHz; the measured sidelobe level is 28 dB in the E-plane and 29.5 dB in the H-plane.