This paper presents a novel integrated p-n varactor and its application in two wide range voltage controlled oscillators (VCOs). Eleven varactors were fabricated using a 0.35 μm BiCMOS process and measured to develop a parametric model. Using this model, two VCOs were designed - VCO1 oscillates from 2.55 GHz to 5.5 GHz with a tuning range of 73.29% and phase noise of -108.56 dBc/Hz at 1 MHz offset. VCO2 oscillates from 1.087 GHz to 2.032 GHz with a tuning range of 60.6% and phase noise of -123.53 dBc/Hz at 1 MHz offset, demonstrating

1. Integrated PN Varactors and their
Application in Wide Range VCOs
M. Marrero-Martín, B. González, J. García, Sunil L. Khemchandani, A. Hernández, and J. Pino.
Institute for Applied Microelectronics and Dpto. de Ingeniería Electrónica y Automática Universidad de Las Palmas de Gran Canaria Las Palmas de Gran Canaria, Spain.
Published in
XXV Design of Circuits and Integrated Systems Conference.
Lanzarote, Spain, 2010.
Abstract
This paper presents a novel cell-based varactor and its application in two wide range LC voltage controlled
oscillators. The varactors are based in p-n junction diodes and they are designed using AMS 0.35 µm
BiCMOS process. A set of eleven varactors has been fabricated and measured to derive a parametric model.
Using this model two oscillators, VCO1 and VCO2, have been designed. Measurements indicate that VCO1
oscillates from 2.550 GHz to 5.500 GHz, with a tuning range of 73.29% and a phase noise of –108.56 dBc/Hz
at 1 MHz offset. On the other hand, VCO2 frequency range is from 1.087 GHz to 2.032 GHz, with a 60.60%
tuning range and the phase noise is 123.53 dBc/Hz at 1 MHz offset.
Varactors Design
VCOs Design
0
Figure 5. VCO1 simplified schematic. Figure 6. VCO2 simplified schematic.
Figure 1. (a) Layout of basic cell. Figure 3. Inductors and capacitors
(b) Layer structure for basic cells. of the varactor equivalent circuit.
Varactors Measurements & Simulations
Figure 7. VCO1 layout. Figure 8. VCO2 layout.
0
VCOs Measurements & Simulations
Figure 2. Layout of a varactor. Figure 4. Capacitances vs. frequency.
Conclusions
In this paper we model new cell-based p-n varactors, Figure 9. VCO1 tuning range. Figure 11. VCO2 tuning range.
which are designed using AMS 0.35 µm BiCMOS
process. A set of eleven varactors has been
fabricated and measured to validate the parametric
model. And to test the varactors, two LC VCOs with
different frequency range were fabricated and
measured. VCO1 oscillates from 2.550 GHz to 5.500
GHz, obtaining a tuning range of 73.29 % and a phase
noise of –108.56 dBc/Hz at 1 MHz offset. In case of
VCO2 frequency range is from 1.087 GHz to 2.032
GHz, with a 60.60% tuning range, and the phase noise Figure 10. VCO1 measured Figure 12. VCO2 measured
phase noise for a 1087 MHz
is -123.53 dBc/Hz at 1 MHz offset. phase noise for a 5078 MHz
oscillation frequency. oscillation frequency.
INSTITUTO UNIVERSITARIO DE MICROELECTRÓNICA APLICADA (IUMA)
UNIVERSIDAD DE LAS PALMAS DE GRAN CANARIA (ULPGC)