A compact high selectivity seventh-order UWB bandpass filter with ultra-stopband attenuation

Based on a unique E-shape microstrip structure and its equivalent circuit, a compact and highly selective seventh-order UWB bandpass filter is developed for small wireless communication systems. This highly selective UWB bandpass filters offers ultra-wide stopband attenuation. The filter composes of six grounded middle stub E-shape microstrip structures connected in cascade using short sections of the microstrip line. The filter structure boosts reduced number of vias achieved by folding back the consecutive middle stubs in opposite direction. The proposed filter is smaller than 4.3 mm × 10 mm × 0.4 mm excluding the feeding ports. The theoretical and measured responses of the filter show excellent agreement.