Antennas
Design and Operation of Antennas
By Don MacArthur
I

n the world of electromagnetic compatibility (EMC) compliance, ensuring that electronic devices meet regulatory standards is paramount. A key component in achieving this compliance is the use of antennas, which are essential for testing and measuring electromagnetic emissions and susceptibility. This article explores the role of antennas in compliance testing, focusing on their construction and materials, setup and calibration, and maintenance and care. By understanding these critical aspects, engineers and technicians can ensure accurate and reliable measurements, ultimately leading to devices that perform optimally and comply with stringent regulatory requirements.

Construction and Materials
Antennas are critical components in various communication systems, and their construction and materials play a significant role in their performance. The choice of materials and design considerations for compliance testing antennas, such as biconical antennas, is essential to ensure accurate and reliable measurements.

Biconical antennas, for instance, are commonly used in compliance testing due to their broadband capabilities. These antennas are typically made from high-conductivity materials like copper or aluminum to minimize signal loss and improve efficiency. The design of biconical antennas includes conical-shaped elements that provide a wide frequency range, typically from 20 MHz to several hundred MHz. Additionally, these antennas often feature an integrated balun (balanced to unbalanced) structure to match the impedance of the elements to the transmission line.

Setup and Calibration
Setting up and calibrating compliance testing antennas is crucial to ensure accurate measurements. The setup process involves placing the antenna in the desired test environment, such as an open area test site (OATS) or a semi-anechoic chamber. The calibration process establishes the relationship between the values indicated by the measuring instrument and a reference standard.

For radiated emission measurements, the calibration must follow specific standards, such as ANSI C63.4-2014 or CISPR 16-1-4, which define the procedures for determining antenna factors (AF). Calibration measures field strength at specified distances using standard test procedures.

Maintenance and Care
Proper maintenance and care of compliance testing antennas is essential to ensure their longevity and performance. Regular maintenance includes cleaning the antenna elements to remove any dust or debris that may affect the signal quality. It is also important to inspect the antenna for any signs of wear or damage and to replace any faulty components promptly.
Calibration
In addition to regular maintenance, periodic calibration is necessary to maintain the accuracy of the antenna. Calibration intervals should be determined based on the manufacturer’s recommendations and the frequency of use. Keeping a detailed record of calibration dates and results can help track the antenna’s performance over time.
Pro Tip: When setting up compliance testing antennas, always ensure a clear line of sight between the antenna and the device under test
testing antenna
When setting up compliance testing antennas, always ensure a clear line of sight between the antenna and the device under test (DUT). Any obstructions or reflections can introduce inaccuracies in your measurements. Keep detailed logs of your calibration settings and environmental conditions during each test session. This helps maintain consistency across tests and makes troubleshooting any anomalies much easier. Keeping a clean testing environment and regularly inspecting your antenna for wear and tear can further enhance the reliability of your measurements.
Summary
In compliance testing, antennas are crucial for measuring and ensuring electronic devices meet regulatory standards. The construction and materials of these antennas, typically using high‑conductivity metals like copper or aluminum, ensure efficient performance. Proper setup and calibration, following standards such as ANSI C63.4-2014 or CISPR 16‑1‑4, are essential for accurate measurements. Maintenance practices, including regular cleaning, inspection, and periodic calibration, help sustain antenna performance and longevity. Understanding these aspects ensures reliable measurements and compliance, ultimately leading to optimal device performance.
References and Further Reading
  1. Emmanuel Ikimi, “Antenna Basics: Working Principle, Types, and Applications,” Maker Pro, February 28, 2020.
  2. A.H. Systems, “Biconical Antenna Selection for Compliance Testing.”
  3. Werner Schaefer, “Antenna Parameters and Antenna Calibration,” In Compliance Magazine, June 30, 2016.
  4. Doug Kramer, “Introduction to EMC Antenna Calibration Methods,” ETS-Lindgren, May 12, 2015.
  5. A.H. Systems, various application notes.
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