A compact differential wideband bandpass filter with good out-of-band performance

In this article, a compact resonator-loaded coupled line-based shaped differential wideband pass filter with good harmonic suppression for common mode is presented. It consists of four ports arranged in a watch-shaped configuration for differential mode of operation. To analyze the differential mode, circuit is divided into two-port networks along a symmetrical plane. This results in a stopband response under common mode excitation or a bandpass response under differential mode excitation. The length and width of the stubs can be optimized to observe the passband and stopband responses for the differential bandpass filter. A filter is then fabricated using substrate Roger5880, epsilon r = 2.2, and thickness (t) = 0.787 mm for experimental verification of the proposed technique.