Dual‐Band Filtering Phase Shifters With High Selectivity and Low Phase Deviation

ABSTRACT In this letter, a type of dual‐band filtering phase shifter is proposed that achieves low phase deviation and high selectivity. A structure for adjusting phase slope using phase‐slope‐compensation stubs is employed. The phase slope of the phase shifter can be flexibly adjusted by varying the impedance of the phase‐slope‐compensation stubs, effectively compensating for the phase slope variation caused by changes in the electrical length of the delay line and ultimately achieving a low phase shift error. The quad‐mode ring‐loaded resonator is employed to achieve two individually adjustable passbands. Two extra transmission zeros (TZs) are introduced by the stepped impedance resonator, noticeably enhancing the selectivity. To verify the design principle, three prototypes were fabricated and measured, demonstrating phase deviations of 90 ± 2.6° (with 45 ± 1.8° and 22.5 ± 1.3°) in the first band and 90 ± 1.5° (with 45 ± 1.7° and 22.5 ± 1.1°) in the second band, providing strong evidence of the theory's reliability.