Harmonic suppression of microstrip ring resonator using double spurlines

Niwat Angkawisittpan

Abstract

This paper presents a new design of microstrip ring resonator with harmonic suppression using double spurlines. Double spurlines are introduced for harmonic suppression in the proposed ring resonator with the purpose of circuit size miniaturization. The spurline structures force the proposed resonator to resonate only at the fundamental mode. It is shown that the harmonics can be suppressed by introducing double spurlines into the microstrip section without increasing the circuit size. The proposed resonator is designed with Finite-difference time-domain method (FDTD) and is implemented with microstrip technology. From the simulated and measured results, the proposed resonator operated in transmission mode resonates only at 2.35 GHz. Moreover, the transmission of harmonic region is reduced by 40 dB. It is appropriate to employ the proposed resonator in microwave circuit systems that require the compact size of the circuit.