A broadband high dynamic range voltage controlled attenuator MMIC with IIP3 > +47dBm over entire 30dB analog control range

In this paper we introduce a novel design technique for broadband high dynamic range absorptive voltage controlled attenuators (VCA) on SOI CMOS. The VCA design is based on the classical passive FET `Pi' and `Tee' attenuator structures but uses stacked FET techniques to dramatically improve the signal handling capability. The VCA has >;30dB attenuation range over a frequency band from DC to >; 5GHz and achieves an IIP3 of >; +47dBm over the entire analog control range. The use of a stacked FET structure evenly distributes the RF signal across `N' FET devices thus reducing the 3rd order distortion generated by each individual FET. The reduction in distortion gained is directly proportional to the degree of stacking used.

I. Introduction

In this paper we present a fully monolithic solution for a broadband attenuator that uses stacked FET techniques to produce a linear-in-dB voltage controlled attenuator with IIP3 greater than +47dBm over the entire attenuation control range. The design integrates all the support, control and temperature compensation circuitry onto a single CMOS SOI die together with programming features such attenuation control slope gain adjustment, control slope polarity inversion and 3.3V or 5V power supply operation [1].