FIR-filter based RF-beamforming network for wideband and ultra wideband antenna arrays

In this paper, a wideband electronic beamforming concept applicable for UWB short pulse systems is derived and experimentally demonstrated. In particular, a Finite Impulse Response (FIR)-filter based beamforming network is configured such that an antenna array yields a desired radiation pattern within a predefined frequency range. An experimental verification of a wideband transmission system is presented for the frequency range from 1.5 GHz to 2.0 GHz. The transmit system consists of a wideband power divider feeding a matrix of analog FIR-filters. These FIR-filters control a circular antenna array of four elements. The receiver consists of a single antenna element. Measurements are performed in frequency domain using a vector network analyzer. The results show an almost frequency independent radiation pattern with a half power beamwidth of 72◦ and a maximum sidelobe level of -10 dB.