Design of LNTA for Multi-Band WCDMA

Currently, a low cost, single-chip multi-band WCDMA/GSM transceiver is needed for the 3G segment of the cellular communication that provides backward compatibility with the 2G GSM network. In this thesis, a novel, multi-band, low noise transconductance amplifier (LNTA) is presented. The LNTA has three stages, which are the transconductance, feedback and single ended to differential conversion stages. In order to eliminate the bulky and lossy passive balun deployed for single ended to differential conversion before the LNTA, a single transistor was used preceding the LNTA in order to provide a differential output. The LNTA is designed with a large transconductance in order to suppress noise in the second stage mixer of a wideband transceiver. Hence, CMOS transconductor was employed as the input stage, and the transconductance of the LNTA was stabilized by the constant gm biasing circuitry. Moreover, an active feedback technique was developed to increase the linearity of the LNTA. Finally, a dual band matching network was used in order to realize multi-band operation. The LNTA presented in this thesis achieves 1.8dB – 2.8dB noise figure in the WCDMA bands. S11 is below -12 dB from 870MHz to 960MHz and it is below -15dB from 1.8GHz to 2.2GHz. The worst case out of band IIP3 is -14dBm for low band and -8dBm for the WCDMA high band. The total current consumption is 9mA from a supply voltage of 1V. The LNTA has been designed in IBM’s 65nm CMOS process technology.

Subject

CMOS amplifier
active feedback
dual-band matching

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Student theses

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master thesis

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Thesis_Hakan.pdf

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