Miniaturised microstrip bandpass filter using octagonal hairpin resonators with side-coupled technique

A miniaturised elliptic-function-response bandpass filter using octagonal double-hairpin-shape resonators with side-coupled stubs has been designed and fabricated. Measured results are in good agreement with the electromagnetic simulation results and verify that the central frequency and the passband range of the proposed filter are 968 and 950-990-MHz, respectively. Also, its electric coupling characteristics and field distributions are investigated. The circuit size of the proposed filter occupies only 22.6-14.3-mm (-0.13-_gtimes0.085times_g).