Sponsored by:

Table of Contents:

Definition and Overview

1. Copolar and Total Power Front-to-Back Measurement

2. Cross-Polar Discrimination

3. Polarization Purity

4. Microstrip Patch Antennas versus Dipole Antennas

5. Further Discussion of XPD

6. Orthogonality for Dipole and Microstrip Patch Antennas

7. Tracking of Antenna Beams

8. Summary

Self-Test

Glossary

PDF of this tutorial

Definition
Many wireless service providers have discussed the adoption of a polarization diversity scheme in place of a space diversity approach. Like space diversity, polarization diversity relies on the decorrelation of the two receive ports to achieve diversity gain. The diversity gain from polarization diversity is maximized if the dual-polarized antenna has receive and receive diversity ports that receive radiation in a cross-polarized fashion over the desired coverage area with equal field strengths. Stated in another way, in a typical sectorized system, the two receive ports must remain cross-polarized (i.e., orthogonal) and capable of tracking one another over the forward 120-degree sector and into the hand-over area. The orthogonality, combined with tracking ability, is necessary if systems using dual-polarized antennas in a polarization diversity scheme with an advanced combining technique are to perform as well as systems employing vertically polarized antennas in a horizontal space diversity format.

Overview
This tutorial provides an in-depth explanation of antenna pattern measurement techniques used to determine the performance of dual-polarized antennas and of some antenna characteristics that are unique to antennas used in a polarization diversity scheme.