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By William Clausen, Prowave LLC

Introduction

The evolving 3G and 4G communications standards are offering higher data rates both for uplink and downlinks. They employ multiple data and modulation formats. The new standards also improve the usable data rates for mobiles operating at highway speeds in excess of 100 Km/hr. These higher throughputs stress the system's infrastructure and firmware. To enable higher throughput many physical phenomena need to be compensated for, such as multipath and fading. Legacy systems usually employ a single antenna or, at best, a limited array. To implement the MIMO (multiple-in, multiple-out) concept for spatial diversity where multiple transmitters may send data to a single receiver, fast switching or beam steering antennae are desirable.

This article presents a method of developing a steerable array of antennas using the post processing capabilities of EDA software. Our technique employed Agilent Technologies' Genesys simulation software with Agilent's Momentum GX 3-D-planar EM simulator. Superposition of fields through post processing allows the prediction of the far-field pattern from an array of similar antenna elements. Individual element phase, amplitude, and spacing may be tuned to achieve the desired beam direction. When a large number of elements are employed, the optimization engine in the software is used to provide the optimum drive level and phase for a selected beam angle.

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•Application Note: Antenna Array Modeling And Optimization