Preliminary Comment
Those involved in compliance engineering are often required to read many standards and comprehend them so they can guide others. Although informative, many of these same standards are not very exciting to read, are often confusing, and seem like they contain conflicting requirements. Most are not meant to be read like a novel but are better suited to reading small sub-sections at a time. There are exceptions to the rule, and the following briefly describes an exceptionally well-written standard that breaks the typical mold.
Introduction
On September 23rd, 2021, the IEEE Standards Antennas and Propagation Society approved and released a new 207-page version of IEEE Recommended Practice for Antenna Measurements. This 2021 version of the standard is identified as IEEE Std 149TM and was developed by the Antennas and Propagation Standards Committee, Working Group APS/SC/149_WG. The previous version of the standard was dated as far back as 1977 but was reaffirmed in 2008. It has been over 40 years since the original version of the standard was published and much of the technology available at that time is now obsolete. Therefore, this new updated major revision and expansion of the original standard is a welcomed addition to the compliance test and engineering community.
Due to advances in technology over the past 40 or so years, it was not possible to maintain the intent of the original standard as a standardized test procedure for antennas. Therefore, the committee reclassified IEEE Std 149-1977 as a recommended practice, intending to have it function instead as a guideline for obtaining the highest quality measurements without prescribing an exact method. The new recommended practice, however, does preserve many familiar areas covering antenna measurements and range evaluations but depicts them using the latest state-of-the-art industry best-practice methods and contemporary tools.
Participants
When the 2021 version of the IEEE Recommended Practice for Antenna Measurements was completed, the working group responsible for its construction had a Chair, Vice Chair, Secretary, and over 60 members. The number of balloters (those who may have voted for approval, disapproval, or abstention) was 36.
When the IEEE SA Standards Board approved this recommended practice, its membership was comprised of a Chair, Vice Chair, Past Chair, Secretary, and 22 individual members, one of which was listed as Member Emeritus.
What’s Included in the New Recommended Practice?
The standard’s abstract indicates the new recommended practice includes fundamentals related to measurements of antenna transmitting and receiving properties. The standard assumes that any antenna to be measured can be treated as a passive, linear, and reciprocal device where radiation properties can be measured in either the transmitting or the receiving mode. It includes the important note that a fundamental property of any antenna is its radiation pattern. Therefore, the measurement of radiation patterns in an antenna test facility is examined. Furthermore, the design of antenna test facilities is explained along with instrumentation requirements for the proper operation of the antenna facility, directions for evaluating an (existing) range, and the operation of ranges is included. An additional benefit of the standard is that references that clarify measurement techniques and where additional details may be found are provided.
Scope
The scope of the standard is chock full of useful information on all things related to measurements of antennas.
For example, the standard includes measurement of radiation patterns in an antenna test facility, design of antenna test facilities, instrumentation requirements, and directions for evaluating and operating antenna ranges.
A parameter that frequently limits the useful bandwidth of the antenna is the input impedance to the antenna (this important parameter controls power transfer from generator to antenna); therefore, measurement procedures and network descriptions for antenna impedance are included.
Measurement of the radiation pattern includes errors. A method of measurement uncertainty analysis is provided for its applicability to the various test facilities portrayed. This is a valuable resource for anyone running an accredited test facility who must provide a measurement uncertainty budget as part of the accreditation process.
Purpose
This recommended practice provides a guideline for the conventional approaches and techniques used to describe the functioning of conventional antennas.
Specific Contents
Specific notable contents in the order they are presented in the standard include the following:
- Normative References
- Definitions, Acronyms, Abbreviations
- Antenna Range Design
- Antenna Range Instrumentation
- Antenna Range Evaluation
- Measurement of Radiation Patterns
- Measurement of Gain and Directivity
- Measurement of Polarization
- Measurement of Radiation Efficiency
- Measurement of Impedance
- Special Measurement Techniques
- Uncertainty Evaluation
- Antenna Range Operation
- Electromagnetic Radiation Hazards
- Antenna Testing Under Environmental Conditions
- Informative Annexes
- Annex A – Bibliography
- Annex B – Field Regions
- Annex C – Reciprocity
- Annex D – Over-the-air (OTA) Measurement of Integrated Devices
- Annex E – Electrical to Reference Boresighting
- Annex F – Impedance Mismatch Correction Deviations
Conclusion
The working group responsible for updating this standard should be proud of their accomplishment. In approximately 200 pages, they have managed to succinctly communicate all that needs to be known about performing antenna measurements correctly and with engineering rigor. Even if you are not involved in the practice of the measurement of antennas but have a passing interest and would like to learn more, this is the standard to read. Doing so will quickly get you up to speed, saving you many hours of unnecessary research and much confusion.
