A fully integrated CMOS direct-conversion transmitter front-end for WiMAX

Abstract

A complementary metal oxide semiconductor (CMOS) direct-conversion transmitter front-end circuit for WiMAX is presented in this article. The front-end circuit includes an I/Q modulator, a power amplifier and an integrated on-chip balun. The on-chip LC balun provides differential-to-single-ended conversion which can eliminate the mismatch caused by off-chip balun. The proposed transmitter front-end circuit is fabricated by a 0.18-µm CMOS technology with thick metal option. The measured saturated output power is 20.6 dBm with local oscillator of 2.5 GHz. This study is tested using a WiMAX baseband signal with 10-MHz and 20-MHz bandwidths, 64-quadrature amplitude modulation and 5/6 coding rate. When the output power is 12.6 dBm, the measured error-vector magnitude is less than −30.52 dB.

Keywords:

• I/Q modulator
• power amplifier
• LC balun
• transmitter
• WiMAX

Acknowledgements

The authors thank Andrew Ko from Agilent HK and Dr. Siu-Kei Tang for their support in conducting measurements. This study was supported by the Research Grant Council of Hong Kong SAR Government under project number CUHK414408.