Frequency-Dependent Phase Difference Feeding Network for Beam Direction Stabilization

A novel frequency-dependent feeding network is proposed to feed an antenna array that works in an octave frequency range. To achieve a fixed beam direction in such a broad bandwidth, the ratio of the phase difference to the operating frequency of the feeding network is designed to be constant across the frequency range. Compared with fixed feeding networks, the topology is highly flexible, allowing for different output phase differences by simply altering the values of the phase shifters. Variable output phase differences . can be realized by tuning the frequency-dependent power dividers and the phase shifters. A design method for a frequency-dependent power divider is proposed using the signal synthesis theory for directional couplers. Moreover, a broadband 90. phase shifter is proposed to compensate for the phase offset in the feeding network. An experimental feeding network is designed and fabricated for a broadband antenna array, achieving fixed direction beams in the frequency range of 2-4 GHz. The measurement results are consistent with the simulation results. In addition, the proposed frequency-dependent feeding network can be extended for higher-order networks.