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This paper proposes some novel substrate-integrated waveguide (SIW) bandpass filters combined with planar resonators. According to specific topologies, microstrip lines with different electrical lengths are introduced into their designs. Their corresponding phase-shift characteristics are used to obtain the desired couplings between SIW cavities and the microstrip resonator. Two third-order filter samples are realized. One has a single transmission zero below the passband and the other possesses a quasi-elliptic response. Further, a fourth-order filter is developed by effectively superpositing two individual third-order topologies. It shows better frequency selectivity and flat in-band group delay, with good agreement between the measured and the simulated S-parameters. Their compactness and high rejection in the stopbands make them very suitable for system-on-package.