Harmonic suppressed differential phase shifter

For the first time, a broadband differential phase shifter with harmonic suppression is proposed. The proposed structure is not only used to provide a constant differential phase shift over the desired wide bandwidth, but also have a significant harmonic band rejection at the same time. Design formulas for the structure are derived using a systematic analytic technique. The optimal design parameters for different typical differential phase shift values are provided to allow for a quick design procedure. To illustrate the principles, a broadband 45° phase shifter is designed, fabricated and measured. It achieved excellent performance with small insertion loss, small phase deviation and good out of band rejection.