Introduction
This guide provides essential theoretical knowledge of UHF wave propagation and practical insights into UHF label antenna design. Understanding the physical properties of UHF waves is crucial for creating effective label antennas tailored to specific applications. The document covers fundamental antenna parameters, equivalent circuit representations, and a step-by-step approach to UHF label antenna design, including examples and tuning possibilities.
UHF Wave Propagation
This section delves into the principles of UHF wave propagation, including freespace transmission, absorption, reflection, diffraction, refraction, and polarization. It explains how various factors influence signal transmission and reception in UHF RFID systems.
- Freespace Transmission: Discusses the Friis Transmission Equation and key parameters like transmitted power, antenna gain, wavelength, and distance.
- Absorption: Explains how electromagnetic waves lose energy when passing through different media and the impact of material properties on signal attenuation.
- Reflection: Covers directional and diffuse reflection and their effects on wave propagation.
- Diffraction and Refraction: Details how waves bend around objects or change direction when moving between media with different propagation velocities.
- Polarization: Describes linear, circular, and elliptical polarization and their impact on power transfer efficiency between antennas.
Fundamental Antenna Parameters
This section outlines key antenna characteristics and their significance in UHF RFID applications.
- Radiation Pattern: Defines how antenna properties are represented in space, including principal E-plane and H-plane patterns.
- Field Regions: Differentiates between the reactive near-field, radiating near-field (Fresnel), and far-field (Fraunhofer) regions around an antenna, explaining their characteristics and boundaries.
