Revision of IEEE Standard 1309: IEEE Standard for Calibration of Electromagnetic Field Sensors and Probes, Excluding Antennas, From 9 kHz to 40 GHz

by John G. Kraemer PE, Member — Standards Development Committee

A. IEEE Standard 1309 — 1996 at a Glance
IEEE STD 1309 provides calibration methods for electromagnetic (EM) field sensors and field probes, excluding antennas per se, for the frequency range of 9 kHz to 40 GHz. It was published in 1996 as a new standard authored by a committee consisting of several probe and sensor manufacturers and users of EM field probes and sensors, as well as those with a general interest in the subject area. Per IEEE procedures, the standard is due for reaffirmation or start of revision in 2001. The IEEE EMC Standards Development Committee recently approved a project authorization request to revise the standard.

B. Overview of IEEE Standard 1309
EM field sensors are defined as electrically small, passive devices used for measuring electric and magnetic fields with minimum perturbation of the field being measured. Unlike antennas, they are designed to extract minimum energy from the field. EM field probes, by definition, consist of one or more field sensors and interfacing electronics (e.g. diodes, resistors, amplifiers) to provide an indication of field strength.

Field probes and sensors are used in two principle areas: 1) radiated EM effects immunity testing under popular standards such as MIL-STD-461E, DO-160D, and IEC 61000-4-3, and 2) radiation hazard measurements, such as those applicable to ANSI C95.3. They are also used to characterize transient fields such as those produced by ESD and lightning.

STD 1309 provides three calibration methods for EM field probes and sensors: calibration using a transfer standard, calibration using calculated field strengths, and calibration using a primary standard (reference) sensor. Most of the standard is devoted to calibration using calculated field strengths; it provides methods for creating standard electric and magnetic fields for sensor and probe calibration and provides direction on probe orientation in the field.

Per STD 1309, calibration shall address the characteristics of amplitude response, frequency response, accuracy (uncertainty), linearity, and isotropy. Additionally, the calibration may address response time, time constant, and response to modulation characteristics. Procedures for each of these measurements are included in the standard.

The number of calibration measurements made and which are quantized into various “grades” of calibration for each applicable characteristic, depends upon the probe or sensor design, the manufacturer’s specification, and the needs of the user. The standard provides descriptions of the various “grades” of calibration for each characteristic to aid in the specification of a calibration.
Although most of the standard’s text is dedicated to frequency domain calibration, methods are provided for time (transient) domain calibration. Included are methods to generate standard transient fields used for time calibration.

C. Why Revision?
As with almost any new standard, the first few years of use will bring about ideas for improvement. Areas of improvement, and hence expanded usefulness to the EMC community, may include the addition of characteristics to measure that may be applicable to one or more probe/sensor type, more direction on determining measurement uncertainty, or maybe an informative annex explaining how a particular calibration characteristic relates to a specific application of a field probe (e.g. burst peak measurement).

Several EM field probe and sensor developers and general interest EMC practitioners have expressed interest in adding descriptions of new probes types to the standard. This may prompt the need to include new acceptable methods of field generation and calibration. Currently, the standard includes the TEM cell, Helmholtz coil, open-ended waveguides and pyramidal horn antennas as preferred methods of field generation for frequency domain calibration.

Most importantly, the revision process will provide a wide opportunity for probe and sensor users, manufacturers, and general interest parties to provide constructive feedback and participate in the making of changes to this relatively new standard as part of an active working group.

D. Call for Volunteers
Do you have an interest in participating on the IEEE STD 1309 revision working group? If you are a user or manufacturer of EM field probes and/or sensors, or if you have a general interest in this area and would like to be part of this activity, please let us know. We currently plan to have our first working group meeting the week of August 19, 2002, in conjunction with the IEEE EMC Symposium in Minneapolis.

Our goal is to maintain a useful, up-to-date standard.

For more information, please contact John Kraemer at: jgkraeme@rockwellcollins.com.

John G. Kraemer is a principal EMI/EMC engineer at Rockwell Collins, Cedar Rapids, Iowa. His responsibilities include EMI/EMC design leadership and analysis on defense/aerospace communication, navigation, and cockpit display products. He also leads company-wide EMI/EMC training programs and has recently produced an in-house interactive computer based training course covering the design of aircraft equipment for EMI control. With over 19 years of EMI, EMC, TEMPEST and signal analysis experience, he is also teaching a new graduate level course on EMC for Iowa State University. He is the chairman of the committee that developed IEEE STD 1309, is a registered professional engineer in the State of Iowa, and is a NARTE certified EMC engineer. He may be contacted at jgkraeme@rockwellcollins.com.

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