A Compact Antenna Array With Integrated Feeding Structure for Intelligent Vehicular Transportation Systems Application

A compact antenna array is developed for W-band vehicle mounted millimeter-wave radar, also suitable for Internet of Things (IoT) and intelligent vehicular transportation systems (IVTSs). The proposed array provides a flat shoulder shaped (FSS) radiation pattern, obtained using a beamforming algorithm, enabling medium- and long-range radar detection and information transmission between wireless devices. The beamforming algorithm determines the excitation amplitudes and phases of each subarray. Power dividers are designed using a scheme of equal/unequal power division to meet the requirements of amplitude. And phase shifters are used to create required phases. To obtain a compact design, a substrate integrated waveguide (SIW) feeding structure are employed to integrate power dividers, phase shifters, and waveguide transitions into a single part. Quadratic recursive exhaustive search in combination with full-wave simulation is used to optimize the design. Further improvements are made to achieve a more compact feeding structure. The realized array provides a stable FSS radiation pattern in the H-plane. In addition, its maximal gain appears in the boresight direction, which is usually a challenge for patch element array. The realized gain is 22 dBi, and the ripple in the shoulder range is less than 2.3 dB, which is better than other designs. The feeding structure is only 14 mm $\times 16$ mm large, showing a minimized design. The demonstrated antenna presents itself to be an excellent hardware candidate for IoT and IVTS.