Low-IF 5 GHz WLAN linearized transmitter using baseband digital predistorter

Abstract

This paper proposes a low-IF architecture, which is appropriate for the design of a WLAN 802.11a transmitter. A prototype circuit was designed, for experiments in this work, in the frequency band 5.1 GHz to 5.9GHz. The evaluation of this transmitter was carried out in terms of Error Vector Magnitude (EVM) and assessed for different power backoffs. Moreover, a digital baseband predistorter was added in order to improve the tradeoff between linearity and power efficiency since WLAN signals admit a high peak to average power ratio. The low-IF predistorted transmitter has shown better linearity performance for lower power backoff than that obtained with the same one but without linearization. Thus, the proposed linearized WLAN transmitter takes advantage of the digital implementation of the IQ modulator in addition to the digital baseband predistortion for improving the EVM performances for a low power backoff.