Noise in VCO and PLL - Noise figure control in LNA

Noise in VCO and PLL: Noise properties of VCO and PLL, key components of modern telecommunication systems, have been studied. Noise due to internal white noise sources in steady-state oscillators is well described by random walk phase noise, that causes zero-crossing jitter, plus amplitude noise, that is usually negligible in applications. In VCO, the control voltage does a®ect not only the frequency, but noise sources too; starting from this observation, accounting for the intermodulation between control signal and noise sources, a model for phase noise in VCO when a time varying control signal is applied has been developed and tested with simulations. Preliminary results regarding square wave modulation are available for now. Noise figure control in LNA: Continued in 2005 the cooperation with the RF Group on the study of noise ¯gure control techniques in LNA, mainly for cellular phones and portable terminals. In the context of re-con¯gurable multistandard, multi-frequency applications, the portable terminal should adapt itself, in addition to changes in the frequency band of operation, to other time-varying RF environmental conditions, such as signal strength and blockers strength. Aiming at power consumption reduction, the frontend, and the LNA in particular, should not be designed to operate always at minimum noise ¯gure, since noise ¯gure is almost always reduced at the cost of higher power consumption. Signi¯cant power saving can be achieved by allowing noise ¯gure to rise, without a®ecting the quality of the received information, when certain signal strength and blockers strength combinations are met, e.g. strong signal and weak blockers. Publication of the results is expected in 2006.