Fractal microwave passive circuits are simple and novel structures that attract much attention recently, however, the fractal technique is dominantly applied in antennas. In this paper, some new characteristics of microstrip equilateral triangular patch resonator with fractal defection are analyzed, and novel fractal bandpass filters using equilateral triangular resonator are presented to implement high performances of multi-transmission zeros, wide passband and stopband, and low passband insertion loss as well as miniaturization. Using fractal defection in patch, multi higher order modes are inspired for coupling a much wider passband, and parasitical harmonics are effectively suppressed. A new bandpass filter with a wide passband of about 0.92 GHz (εr = 9.8) or 2.7 GHz (εr = 2.2), maximum passband insertion loss of less than 0.5 dB, and multi-transmission zeros at both sides of passband, and a second bandpass filter with wide passband and stopbands of more than 2 GHz are implemented. Compared with some literatures, sizes of the new filters reduced and performances are greatly enhanced. The proposed filters have compact and simple structures, small sizes, high selectivity and so on, and all these features are the requirement of wireless communication circuits.
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