Ultra Linear Low-Loss Varactor Diode Configurations for Adaptive RF Systems

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Two linear low-loss varactor configurations for tunable RF applications are compared. The wide tone-spacing varactor stack provides the best linearity for signals with relative large tone spacing like receiver jammer situations. The narrow tone-spacing varactor stack offers the highest linearity for in-band-modulated signals, and is better suited to adaptive transmitters. Both structures make use of a varactor with an exponential <formula formulatype="inline"><tex Notation="TeX">$C(V_{R})$</tex> </formula> relation, and so the different requirements of transmit and receive chains can be addressed in one technology. Both configurations have been realized in a silicon-on-glass technology. The measured <formula formulatype="inline"> <tex Notation="TeX">$Q$</tex></formula> at 1.95 GHz is from <formula formulatype="inline"> <tex Notation="TeX">${\sim}$</tex></formula>40 to 200 over a capacitance tuning range of 3.5 with the maximum control voltage of 12 V. The measured OIP3 of both structures are roughly 60 dBm. </para>