Fabrication of wireless LAN low-pass-filters for IEEE 802.11 b/g and IEEE 802.11 a in printed-circuit-board

Normally, embedded low pass filters (LPFs) by using low temperature co-fired Ceramic (LTCC) technology are widely employed and developed. In this paper, two embedded filters for both IEEE 802.11 b/g (Low-band) and IEEE 802.11 a (High-band) are designed and fabricated in printed-circuit-board (PCB) as organic substrate. In order to discuss the performance of LPFs in PCB, two LPFs for low-band and high-band are designed and fabricated in both LTCC substrates and PCB substrate. This paper deals with constrained condition in PCB when LPFs are designed and simulated. A proposed LPF for low-band is composed of series inductors, series capacitors, and shunt capacitor. A LPF for high-band consists of series inductors, series capacitors, and shunt capacitor. Parasitic capacitance which occurs in high RF frequency is important factor when a LPF for high-band is designed. This paper employs parasitic capacitance as shunt capacitor instead of avoiding parasitic capacitance. Parasitic capacitance is extracted and modeled from 2.5-Dimension simulation in order to employ the parasitic capacitors in high-frequency. Measured insertion loss and return loss for a low-band LPF and a high-band LPF by using LTCC are better than 0.5 dB and 18.7 dB, respectively. Measured insertion loss and return loss for a low-band LPF in PCB are better than 0.5 dB and 29.2 dB, respectively. Measured insertion loss and return loss for a high-band LPF in PCB are better than 0.9 dB and 12.7 dB, respectively. A fabricated LPF for high-band in PCB has a little difference from simulation and measurement. Insertion loss of high-band LPF in PCB is less than in LTCC. As a result, this paper shows that the performance of two LPFs in PCB is good.