This paper introduces the design and analysis of a compact bandpass with sharp attenuation. The filter topology employs three different cells of a bisected-Π/Π configuration of a negative refractive index metamaterial transmission line. The filter centre frequency is 3.65 GHz, and its 3 dB cutoff frequencies are 2.55 GHz and 4.6 GHz (57% fractional bandwidth). The filter attenuation increases to 20 dB in only 100 MHz (at 4.7 GHz). Moreover, the filter has only 0.2 dB insertion loss within the passband. The filter stopband is characterized with typical flat with 0.2 dB return loss within the stopband (4.7 GHz-5.75 GHz) and very close to 20 dB insertion loss. Moreover, the filter has two frequency independent designed transmission zeros within this stopband. Along with previous specifications, the filter size is only 0.22λg × 0.20λg (12 × 11 mm2) at centre frequency. The filter performance has been validated through circuit model, electromagnetic simulation, and experimental measurements.
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