A Compact Five-Port Hybrid Network with Electronic Control of Both Magnitude and Phase

This work presents a microstrip line-based 5-port hybrid network with tunable magnitude and phase outputs. The network is constructed by incorporating an additional output port into the traditional 3 dB branch – line hybrid coupler and integrating two varactor diodes. The proposed beamforming network offers a 30° progressive phase variation with amplitude variations of at least $\pm 3 \mathrm{~dB}$ over the $2.25-2.55\ \mathrm{GHz}$ range using only one varactor diode, while the other is set to a fixed bias. Thus, it is ideal for adaptive beamforming in wireless LAN applications. Since it is based on a transmission line model, higher-order beamforming networks can be easily obtained. Measurements show that the 5 – port coupler maintains at least 15 dB isolation and a 10 dB return loss over the $2.2-2.8\ \mathrm{GHz}$ range. The overall size of the structure is $0.125 \lambda_{g}^{2}$.