A 3.1 to 5 GHz cmos rf transmitter for direct-sequence code division multiple access applications

Abstract

An ultra-wideband RF transmitter with local oscillator (LO) leakage reduction method for direct-sequence code division multiple access (DS-CDMA) is presented. To achieve ultra-wideband gain flatness, the method of combining two shunt-peaking loads with different resonant frequencies is used. A double balanced mixer with a linear transconductance stage is used to increase the linearity of the mixer. To reduce the LO leakage at the output port, an additional DC feedback loop is applied to the linear transconductor. Measurement results show 9.5 dB gain with +/- 0.8 dB variation over 3.1-5 GHz range. The output P]dB is approximately -3 dBm and the output IP3 is more than 9.8 dBm for a frequency greater than 3-5 GHz. By the LO leakage reduction method, the LO leakage output power is 5 dB lower than without it. The transmitter consumes 54 mW with a 1.8 V supply and is realized with a 0.18 mu m RF CMOS technology. (c) 2007 Wiley Periodicals, Inc.