Frequency Beam-Steering Antenna With Large Scanning Angle and Low Sidelobe in Brick Configuration Aiming for 2-D Expansion

This communication presents the design, fabrication, and full experimental verification of a frequency-controlled beam-steering antenna array with large scanning angle and low sidelobe. A brick configuration, which allows full 2-D beam-steering expansion, is implemented for the overall design and specifically optimized for further integration of corresponding transmitter/receiver (T/R) modules. A novel stripline-fed quasi-Yagi antenna constructed in a three-layer geometry is proposed as the radiation element. Moreover, a novel low insertion loss coplanar waveguide (CPW)-to-stripline transition, sheltered by ground in both sides, is proposed for the feeding and resistance loading. In this proposed antenna design, by applying a broadside coupling and optimizing the radiation element, a strong coupling is achieved at the center working frequency and can also maintain almost unchanged within the whole operational frequency range, leading to constant low sidelobe levels (SLLs). Three substrate layers are utilized to ensure accurate alignment between the slow-wave stripline and radiation elements, which is essential for the prevention of sidelobe deterioration due to possible fabrication tolerance. A 20 element prototype is demonstrated and manufactured. In the measurement, this antenna is able to scan from -42° to 36° within its 2 GHz operational bandwidth. Meanwhile, a flat gain around 15 dBi and a SLL smaller than -18.5 dB are obtained. The above performance indicates that this antenna is a good candidate for scaling to 2-D beam-scanning large array applications.