System-level filter design methodology for WLAN-OFDM transceivers

Orthogonal frequency division multiplex (OFDM)-based WLAN standards target wireless communications in the 5 GHz band for consumer multimedia applications. Digital OFDM transceiver ICs, based on frequency domain equalization, have been presented. However, it is still a challenge to design a complete system, including the front-end, with minimum degradation of the performance offered by the digital modem. This article focuses on mixed-signal filtering aspects, introducing filters in the system signal path that reduce or even completely corrupt the system performance, even if the filters fulfill the spectral specifications. Therefore, an efficient model was developed, which provides direct insight to the cause of degradation due to filtering, and additional specifications (apart from the filter mask) are defined. Given these specifications, a system-level filter design methodology to efficiently constrain the implementation loss and implementation complexity is presented and illustrated in a design case.