A broadband modified differential phase shifter for microwave applications

In this paper, a novel broadband differential phase shifter is presented. In this design, multi-section coupled-lines are connected to a mirrored one to create a double-section to have a better coupling coefficient and frequency bandwidth of the phase shifter. In addition, the reference line of the conventional shiffman phase shifter is replaced with a similar structure of double coupled-lines to improve the phase and amplitude balance and the frequency response. The proposed design is simulated using the full-wave electromagnetic software IE3D and validated by the measurements. Compared with the cascading microstrip multi-section coupled-line configuration, the presented planar structure is symmetric and has a better performance. In order to prove the idea, the proposed structure is fabricated on a three plate stripline printed circuit and measured. The measured amplitude and phase imbalance between the two paths are within 0.4 dB and 1 degree over the frequency band of 2 to 6 GHz.