Printed Frequency Scanning Antenna Arrays With Enhanced Frequency Sensitivity and Sidelobe Suppression

This paper presents a novel design of the 1-D frequency scanning antenna array with enhanced scan sector, frequency sensitivity, and sidelobe suppression. The antenna is intended for the direct imaging radar sensors. Modified pentagonal dipoles with impedances ranging from 120 to 1070 Omega are used as radiating elements to provide the required sidelobe suppression. For the antenna design, new types of phase shifters are considered, with respect to their insertion loss, frequency bandwidth, phase shift, and manufacturing simplicity: the double-cell left-handed shifter and its right-handed counterpart. Four linear arrays with eight pentagonal dipoles are combined to obtain the antenna array with higher gain and narrower main beam with respect to constituent linear arrays, but with almost identical H-plane scanning properties. The proposed antenna array was manufactured, and the measured results show an increased scan sector of 55 degrees, high frequency sensitivity of 14.25 degrees/100 MHz, gain of 15.5-17 dBi, and low sidelobe levels of around -20 dB in the whole scanning frequency range. Measured results are in very good agreement with simulations.