Coupling modeling and bandpass filter design using electric and magnetic couplings on CMOS 65 nm technology

Abstract

This letter presents the electric and magnetic couplings modeling on CMOS 65 nm technology. It is based on the simplified equivalent substrate model. The field distribution is studied to analyze qualitatively the electric and magnetic couplings. Based on CMOS 65 nm technology, the coupling coefficients with and without passivation are calculated quantitatively for comparisons and then the coupling characteristics are summarized. In order to demonstrate the coupling model, a bandpass filter using electric and magnetic couplings is designed. The measured bandwidth is 23 GHz centered at 63.5 GHz and the insertion loss is 3.8 dB. Good agreement between the simulated and measured results validates the coupling modeling. K E Y W O R D Sbandpass filter (BPF), CMOS 65 nm technology, coupling coefficient, electric and magnetic couplings 1 | INTRODUCTION CMOS technology has been widely applied in the past few years in the radio frequency applications because of its high system integration. When the passive components, such as filters and transformers are designed by using CMOS technology, coupling is a dominant factor to influence the performance, and the electric and magnetic couplings 1,2 should be carefully studied.In the past decades, the substrate modeling of integrated circuit technology has been studied extensively. It helps the designers for simulating microwave circuits. Also, the simplified modeling saves computing time in the full wave simulation. A coplanar waveguide and its discontinuities have been modeled on SOI CMOS technology. 3 The matching network of the power amplifier (PA) is simulated based on the equivalent CMOS substrate, 4 and the measured results of the PA agree with the post simulation.Based on the substrate modeling, the bandpass filter (BPF) design becomes a popular research topic because of its indispensable characteristic of frequency selectivity. Consideration of resonators and their couplings are crucial in filter design. 5 Various resonators are utilized to construct the CMOS BPFs for size reduction and performance improvement. Open loop resonators, 6 parallel line resonators, 7 step impedance resonators, 8 and ring resonator 9 are employed to realize the millimeter wave BPFs. Furthermore, dual-mode BPF 10 is fabricated on 0.18 μm CMOS technology to obtain wide bandwidth. As for the coupling scheme, it has been widely studied on PCB process to obtain the proper coupling strength in filter design. 11,12 However, coupling is seldom discussed in the CMOS technology.In this paper, the modeling of the electric and magnetic couplings on CMOS 65 nm technology has been built. The coupling scheme of transmission lines is analyzed based on the multi-layer technology. Meanwhile, the comparisons of electric and magnetic coupling strengths between quarter-wavelength resonators with and without passivation are studied. This coupling model and the independence between the electric and magnetic couplings found in this paper can be applied to the design of various components, such as BPF, diplexer, and cou...