A multi-beam antenna without a phase shifter has been designed for railway communications at the upper 5G band (28 GHz). Considering the curvature of railway tracks in practice, the required beam deflection range is within-30 to 30 degrees. The limited beam deflection range allows the Rotman lens to replace the phase shifters for beam steering, which saves the system cost considerably. Depending on the choice of the antenna element, it can create either a linear or a circular polarization. The measurement results demonstrate that the linearly and circularly polarized antenna achieves maximum directivity of 10.8 dBi and 11.2 dBi, respectively. The antenna's bandwidth for the linear (circular) polarization reaches 2 GHz (1.8 GHz), sufficient to support the high data rate of the 5G band. The antenna size is minimized to fit in a shark-fin cover mounted on the vehicle.

While the BLE is very popular for indoor communication, the antenna for the BLE in wearable sensor systems is lack investigation. This work proposes the BLE antenna for a wearable sensor, which is (i) small enough to fit in a compact device and (ii) tolerant against the nearby medium change.