| Ultra-Wideband technology with high-date-rate, good safety performance andlow power becomes more and more attractive. Currently, the low-cost CMOS processis used to design ultra wideband circuit, in order to integrated ultra-widebandtransceiver and digital baseband part on a single chip, formed the system on chip.With the evolution of CMOS process, the dimension of the nano-scale CMOStransistors are continuing reduced, which significantly improved the bandwidth andnoise of the CMOS circuit, but damaged the linear performance at the same time. Thesmall dimension of CMOS transistors will induce the short-channel effects, whichmade the performance of CMOS transistors unstably, resulting in severe nonlineardistortion.The paper mainly studies on the mixer and power amplifier in the ultra-widebandtransceiver RF front-end circuits. Firstly, this paper introduces the concept ofultra-wideband technology, implementation of UWB systems and the structure ofmulti-band orthogonal-frequency-division-multiplexing ultra-wideband transceiver.Secondly, this paper described the research status of high linearity ultra-widebandmixers and power amplifiers. Thirdly, the nonlinear distortion mechanism of theGilbert mixer and the linear power amplifier, and several conventional linearizationtechniques are discussed. Finally, this paper proposes a high linearity ultra-widebandup-conversion mixer and power amplifier, and circuits are simulated and layouted byCadence software. The main achievements of this work consist of following aspects:(1) A new high linearity MB-OFDM ultra-wideband up-conversion mixer, whichoperating in the3.1~10.6GHz frequency band, is presented in this paper. The mainstructure of the mixer is a current bleeding pseudo-differential double balancedstructure. The cross-coupling post-distortion technology is used in thetransconductance stage of the mixer, which greatly improved the linearity of themixer and didn’t deteriorate other performance. The simulation results indicate thatthe presented mixer achieves16.56dBm max input third-order intercept point(linearity parameter) over3.1-10.6GHz frequency range.(2) A new high linearity MB-OFDM ultra-wideband power amplifier, which operatingin the3.1~10.6GHz frequency band, is presented in this paper. The circuit adoptstwo-stage differential amplification structure, the first stage is the driver stage and the second stage is the amplification stage. The RC shunt feedback network and thecascode cross-coupling post-distortion technology is implemented in the drive stageand the amplification stage, respectively, which improved the linearity of the poweramplifier. The simulation results indicate that the power amplifier achieves4.6dBmmax input1-dB compressed point (linearity parameter) over3.1-10.6GHz frequencyrange. |
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