Terminology » RF Basics » Circular Polarization: Advantages and Disadvantages

Circular Polarization: Advantages and Disadvantages

circular polarization radio wave rfid antenna polarization

This page covers the advantages and disadvantages of circular polarization, including its basics. It mentions the benefits and drawbacks of using circular polarization.

Introduction

Polarization refers to the directional aspects of the electric field (E-field) of electromagnetic (EM) radio waves. It enables frequency reuse, enhancing satellite bandwidth capacity by allocating the same frequency at different polarizations (i.e., linear and circular).

What is Circular Polarization?

Circular polarization occurs when the E-field radiates energy in both the horizontal and vertical planes, as well as all planes in between. In this polarization, the electric field has two linear components that are perpendicular to each other, with equal amplitude and a 90-degree phase difference.

The resulting E-field rotates in a circle around the direction of propagation. Based on the direction of rotation, there are two types:

  • RHCP (Right-Hand Circular Polarization)
  • LHCP (Left-Hand Circular Polarization)

Circularly polarized light signals can be generated by passing a linearly polarized light signal through a quarter-wave plate (λ/4) at an angle of 45 degrees to the optical axis of the plate.

Circular Polarization

  • RHCP (Right-Hand Circular Polarization): In this type, the electric field rotates clockwise as seen by an observer towards whom the wave is moving. This type is shown in the figure above.
  • LHCP (Left-Hand Circular Polarization): In this type, the electric field rotates counterclockwise as seen by an observer towards whom the wave is moving.

Benefits or Advantages of Circular Polarization

The following are the benefits of using circular polarization:

  • No polarization adjustment is required, as it is fixed using an OMT (Orthomode Transducer).
  • There is less chance of cross-polarization interference.
  • RFID readers do not have to be on the same plane or similar heights as RFID tags, unlike linear polarization RFID readers.
  • RFID readers do not require knowledge of the tag orientation, unlike linearly polarized RFID readers. Therefore, it’s used for applications where the orientation of RFID tags is unknown when reading data.

Drawbacks or Disadvantages of Circular Polarization

The following are the drawbacks of using circular polarization:

  • It increases the cost of the antenna system.
  • It offers slightly lower cross-polarization isolation.
  • It offers a shorter read range for RFID readers compared to linear polarization.

Linear Polarization