A New Fractal-Based Design of Stacked Integrated Transformers

Goran Stojanović,Milan Radovanović,Vasa Radonić

doi:10.1155/2008/134805

Goran Stojanović, Milan Radovanović + Show 1 more

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https://doi.org/10.1155/2008/134805

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Abstract

Silicon-based radio-frequency integrated circuits are becoming more and more competitive in wide-band frequency range. An essential component of these ICs is on-chip (integrated) transformer. It is widely used in mobile communications, microwave integrated circuits, low-noise amplifiers, active mixers, and baluns. This paper deals with the design, simulation, and analysis of novel fractal configurations of the primary and secondary coils of the integrated transformers. Integrated stacked transformers, which use fractal curves (Hilbert, Peano, and von Koch) to form the primary and secondary windings, are presented. In this way, the occupied area on the chip is lower and a number of lithographic processes are decreased. The performances of the proposed integrated transformers are investigated with electromagnetic simulations up to 20 GHz. The influence of the order of fractal curves and the width of conductive lines on the inductance and quality factor is also described.

Highlights

Constant growth of wireless applications brought to an intensive need for mobile communications and mobile communication devices
The integrated transformer is an essential component in many RF and microwave integrated circuits [1,2,3,4,5,6,7,8]
We present novel layouts of the primary and secondary windings in the shape of fractal curves and demonstrate a comprehensive analysis of the shape and order fractal curves influence on the inductance and quality factor

Summary

Introduction

Constant growth of wireless applications brought to an intensive need for mobile communications and mobile communication devices. Used transformers are fabricated on lossy silicon substrate; they are from the start limited to a lower quality factor, coupling coefficient and high parasitic effects between the component and the substrate. Various transformers layouts including parallel winding, interwound winding, overlay winding, and concentric spiral winding were presented in [13]. Planar transformers generally have lower self-inductance, parasitic capacitances, and coupling factor, but higher resonant frequency comparing with the stacked transformers, which engage less chip area and have higher inductance values and lower quality factor [14]. The width of conductive lines (usually have the square spiral shape), spacing between coils, and material used for their fabrication have influence on overlay characteristics of the transformer. Papers that present other layout geometries (apart from square spiral) of the primary and secondary coils are very rare

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