Loaded-line phase shifter with enlarged phase shift range and bandwidth

A loaded-line phase shifter with substantially enlarged phase shift range and bandwidth is presented. The exact synthesis procedure is also presented. In the proposed topology, a pair of open circuited stubs is inserted between two λ/8 transmission lines and two grounded shunt stubs are used to align the insertion phase of the two phase states. For a phase shift of 45°, the simulated bandwidth is increased from 25% to 40% compared to the conventional loaded-line phase shifter while maintaining a return loss better than 16 dB and phase error better than ±2°. For a 90° phase shifter, the ±2° phase error bandwidth is increased from 2% to 21% with a return loss larger than 16 dB. To validate the topology, 45° and 90° phase shifters are designed and measured. The measured ±2° phase error bandwidth is 34% and 21% and the return loss is larger than 14 dB and 10 dB for the 45° and the 90° phase shifter, respectively.