Kari Halonen

RF gain control in direct conversion receivers

This paper presents a study of LO self-mixing and RF gain control issues in direct conversion receivers. In cellular systems, that use continuous time frequency duplexing, these can constitute serious problems. The presented topic is of special importance when digitally programmable gain is implemented at the RF frequencies before the downconversion mixers, practically in the LNA. Furthermore, this paper gives circuit solutions to overcome this problem.

A 2.5 V 50 MHz IF-sampling /spl Delta//spl Sigma/-modulator for digital cellular telephones

This paper discusses the design of a 50 MHz IF-sampling switched-capacitor /spl Delta//spl Sigma/-modulator with a 2.5 V supply voltage implemented in a 0.5 /spl mu/m BiCMOS process. The problems caused by the low analog supply voltage are addressed with special biasing and common-mode arrangements. Simulation results verifying a peak SNDR of 83 dB for a baseband signal are presented.