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A new type of RF microwave differential-mode planar multiband bandpass filters (BPFs) are presented. Each symmetrical half of the proposed balanced filtering architecture is composed of the in-series cascade of K N-stub-loaded cells through K-1 inter-connection transmission-line segments to synthesize a differential-mode transfer function with N K th-order passbands. Additional features of this balanced multiband BPF topology are as follows: 1) generation of transmission zeros at both sides of all differential-mode passbands; 2) high common-mode power-rejection levels within the differential-mode passband ranges; 3) scalability to any number of arbitrary-order differential-mode transmission bands; and 4) lack of electromagnetic couplings in its physical structure. The theoretical foundations of the engineered balanced filter approach, along with guidelines to design the differential-mode transfer function and to …