An embedded Wi-Fi front-end-module in printed-circuit-board by employing printed lines

Abstract

This paper presents the implementation of a front-end-module (FEM) for wireless fidelity (Wi-Fi) by embedding a diplexer and two low-pass-filters (LPF). Each block is designed and simulated by employing printed lines in printed-circuit-board (PCB) substrate. This paper suggests the possibility of embedding all passive components in PCB by using printed lines. A proposed FEM is composed of a diplexer in order to divide a low-band path and a high-band path, a LPF for low-band, and a LPF for high-band in order to reject 2nd harmonic of a power amplifier. The size of an implemented module is 8 mm × 7.5 mm × 0.3. The dielectric constant of the FR4 and ABF in PCB substrate is 4.5 and 3.3, respectively. On basis of dielectric constant, a FEM is simulated. Parasitic capacitance in RF frequency is important factor when a LPF is designed. This paper attempts to employ parasitic capacitance as shunt capacitor instead of avoiding parasitic capacitance. Parasitic capacitance is extracted and modeled from 2.5-D simulation to employ the parasitic capacitor in high-frequency. A schematic of low-band path consists of a series inductor, a shunt capacitor, and a shunt inductor. A schematic of high-band path is composed of a series capacitor and a shunt inductor. Each path is terminated to the measured S-parameter of two LPFs because impedance of each filter isn't exactly 50 ohm. A slim and compact FEM, all components are integrated in PCB, was implemented and measured. As a result, insertion loss (IL) of a LPF for low-band is better than 0.8 dB and return loss (RL) is 12.6 dB. IL and RL of a LPF for high-band are better than 0.9 dB and 12.7 dB. IL and RL of a fabricated FEM are better than 1.9 dB and 7.4 dB, respectively.