Wideband bandpass filter with sharp cutoff and wide stopband for microwave imaging system designed for heart failure detection

A broadband bandpass filter for microwave imaging system aimed at heart failure detection is proposed. The filter is designed using the following three different types of resonators; low impedance feeding network, parallel-coupled microstrip lines and a rectangular middle resonator. To suppress the harmonics, widen and increase the attenuation at the stopband, multiple open-ended stubs are embedded within the resonators arms. ABCD matrices are used to derive the required values of the design parameters for the proposed filter. To meet the frequency requirements of microwave-based heart failure detection system, a filter is designed with fractional bandwidth 67% (500 MHz) centered at 0.75 GHz and more than 20 dB of attenuation at the stopband that extends up to four times the center frequency.