Using Multilayer Baluns To Improve ADC Performance

By Anaren, Inc.

Introduction

This application note explains the use of Anaren's multilayer balun (BD0205F5050AHF) in conjunction with Analog Devices AD9640 integrated dual 14-bit, 80/105/125/150 MSPS analog to digital converter. The AD9640 ADC (Analog to Digital Converter) operates up to a 125 MSPS conversion rate and is optimized for use in diversity radio systems, smart antennas, multimode digital receivers, and software radio systems.

This application note will show that use of Anaren's BD0205F5050A00 balun will result in an improvement in SFDR (Spurious Free Dynamic Range) and gain flatness as compared to a traditional wirewound balun implementation. The BD0205F5050A00 is a new Anaren product that has been specifically designed for use in an ADC front end circuit.

In addition to improving ADC performance, it will be seen that Anaren's baluns offer superior part to part consistency through proven fabrication technology based on multilayer organic substrates. The same technology provides a balun with a sub 1mm height profile for height constrained applications. Anaren baluns, because of the achievable gain flatness, support wide bandwidths at higher frequency of operation for undersampling applications. This differentiation allows operation and performance repeatability not available in a wire-wound equivalent. A reduced overall component count also comes through a single Anaren balun replacing multiple wire-wounds parts while maintaining performance.