Implementation of a front-end-module by embedding a RF switch IC and a power amplifier in printed-circuit-board

This paper presents the implementation of a front-end-module (FEM) for wireless Local Area Network (W-LAN) by embedding a power amplifier module (PAM) and a double-pole-double-throw (DPDT) switch IC in printed-circuit-board (PCB) by sequential build up process using polymers. Polymers are adopted as substrates and these substrates are composed of FR4 and Ajinomoto-bonding-film (ABF). Vacuum lamination process is applied to get a planar surface and void free cavity filling. A proposed module consists of a matching stage for a PAM, a DPDT switch IC, a PAM and a Tx low-pass-filter (LPF) for rejecting 2^nd harmonic of a PAM. All inductors and capacitors for a Tx LPF and for a matching stage are designed and embedded in PCB. Therefore, each component has 3-dimension (3-D) geometry in PCB and it is designed by using Sonnet simulator as 2.5-D simulation tool. The overall size of a module and of a tested board is given as 5 mm times 4 mm times 0.8 mm and 20 mm times 6 mm times 0.8 mm, respectively. PCB employs 12 copper layers. The measured Tx LPF insertion loss is better than 0.5 dB and the return loss is better than 28 dB from 2.4 GHz to 2.5 GHz. Its rejection for 2^nd harmonic of PAM is more than 35 dB. The measured input impedance of a matching stage is 8.1 +11.6j. The measured adjacent-channel power ratios (ACPRs) of 1^st side-lobe and 2^nd side-lobe in the Tx output spectrum are 31.2 dBc and 59.9 dBc, respectively. An output 1-dB compression (P1dB) and gain are 15 dBm and 10.3 dB, respectively.