A 2.4 GHz direct conversion transmitter for Wimax applications

The evolving 802.16 WiMax and WiBro standards offer the possibility of high data rate wireless access for home and business users. The first generation systems are currently being designed and deployed in the licensed frequency bands centered around 2.5GHz and 3.5GHz. The use of high data rate OFDM modulations translates into challenging requirements for the transmitter in terms of spectral quality and EVM. In particular, this calls for low distortion, good signal balance and low phase error. This article focuses on the challenges and advantages associated with implementing a direct conversion transmitter in the Wibro band centered at 2.35GHz. A complete mixed signal implementation that includes a dual DAC, IQ modulator, LO synthesizer, variable gain amplifier and RF power detector is presented along with system-level measured results