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A comparative study on transformer and inductor based LC tanks for VCOs

Duarte R., Fernandes J. R.

International Journal of Microelectronics and Computer Science

2010

Vol. 1, nr 1

37-41

This paper presents a detailed comparative study of two different approaches to implement the resonator found in radio frequency (RF) voltage controlled oscillators (VCOs). An inductor LC tank VCO and a transformer LC tank VCO are compared in terms of phase noise, power consumption, tuning range and circuit area. Conclusions about the use of each approach depending on the design goals are presented.

A Behavioral Model for Sigma Delta Fractional PLL and Applications to Circuit Dimensioning

Duarte R., Fernandes J. R.

Electronics and Telecommunications Quarterly

2009

Vol. 55, No 4

563-575

This paper presents an accurate high level model for the design of sigma-delta fractional Phase locked loop (PLL) architectures. High level models provide simulation speedups of about two orders of magnitude when compared to transistor level simulation. When compared to other models presented in the literature the proposed model has the advantage of having the frequency instead of phase as the output of the VCO. This approach greatly simplifies the implementation of the PLL blocks and results in an increase of the overall model performance. Several nonlinear phenomenons's such as cycle slipping, spurious signals and phase noise are also accurately modelled. Finally, this paper combines genetic algorithms with the proposed behavioral model to optimize the PLL parameters and reduce the impact of the sigma-delta phase noise.