In this letter, a passive high-selectivity dual-band filter with two controllable transmission zero (TZ) pairs is proposed, while synthesis method and control mechanism of the two TZ pairs are investigated. Specifically, by employing the magnetic/electric mixed coupling (MEMC), source–load coupling (S–L coupling) and stepped-impedance resonators, a dual-band bandpass filter with two pairs of controllable TZs is constructed. Two controllable TZ pairs can be independently adjusted by re-modifying the associated coupling structures. To validate the synthesizability and controllability of the TZ pairs, mathematical synthesis, and EM simulations are carried out. Two demonstrative filters with identical passband performance and different central TZ distributions for GSM (0.9/1.8 GHz) are designed and measured. The analysis and experimental results show that the synthesis-controllable TZ pair (fz2, fz3) introduced by MEMC can be synthesized and controlled using inline mixed coupling synthesis, and the optimization-controllable TZ pair (fz1, fz4) because of S–L coupling is controlled by S–L coupling strength optimization procedure.
