Miniaturized on-chip lowpass filters with wide stopband and sharp roll-off

Abstract

In this paper, a compact on chip lowpass filter with wide stopband and sharp roll-off using multi-stage pi-section low-pass cell circuit is presented. In order to obtain the characteristics of wide stopband and sharp roll-off for lowpass filters (LPFs), the pi-section low-pass cell circuit is analyzed and adopted, which is useful and convenient to produce transmission zeros for LPFs. Finally, a third-order LPF and a fourth-order LPF are manufactured and the measurement results show that the filter it has the −3 dB cut-off frequency at 5 GHz, while its insertion loss is less than 1 dB. In addition, the LPFs achieves more than 35 dB sideband suppression format form 6.3 GHz to 40 GHz. The LPFs size are very compact less than $0.41 \text{mm}\times 1.1 \text{mm} (0.02\lambda g\times 0.05\lambda g)$ including the pads. ( $\lambda g$ is the guided wavelength at 5 GHz).