Conformity Magazine - July 2008 - (Page 14)

thus allowing the calculable dipole antenna to become an acceptable method of traceability. While traceability for antenna calibration and site validation have been established, we will discuss later the remaining traceability problem for emission measurements. A project for revision of CISPR 16-1-5 was initiated to add antenna calibration methods to the standard. Due to a significant number of technical issues that require further study and resolutions, this project was deactivated to allow sufficient time for the necessary work to be completed. A complete revision of this standard is not to be expected in the near future. However, amendments to the current version may be available sooner, as we will see in the next section. We should not forget to mention at this point the existence of the American standard ANSI C63.5 [2], which is related to CISPR 16-1-5 and has largely dominated the area of antenna calibration for many years. Although some U.S. members of ANSI C63 subcommittee 1 (which is responsible for ANSI C63.5) are also participating in the CISPR work on antenna calibration, there remain key differences between the two documents. The key differences are the use of theoretical computations and geometric-specific correction factors in ANSI C63.5, as compared to the validation of an REFTS using analytically calculable dipoles in CISPR 16-1-5. There are also issues common to both standards described in [4] in more detail that include the lack of definition of a reference antenna. This ultimately introduces variability to the normalized site attenuation (NSA) measurements used to validate chambers. Therefore, validation of a chamber may lead to different results depending on the standard used. Harmonization between these two standards would be ideal but may still be some way off. CISPR 16-1-4 [5] Chamber Validation Once the antennas have been calibrated per ANSI C63.5, it is then possible to move on to the validation of the COMTS, or in our case the anechoic chamber. CISPR has divided the specification into two different frequency ranges, below and above 1GHz. Below 1GHz, there are two different chamber validation methods, depending on whether the chamber being validated is a semi-anechoic chamber (SAC) or a fully anechoic room (FAR). Semi-anechoic chambers will have absorbers on all walls and ceiling, but none on the floor which is designated as a ground plane as these chambers are fundamentally an indoor OATS. The origin of the use of the ground plane is well documented and the chamber validation method is the NSA method. The American standard ANSI C63.4 [6] also defines the NSA method and also calibrates antennas according to ANSI C63.5. Using the same pair of antennas (typically, to cover the full frequency range, a pair of biconical and a pair of log-periodic antennas are used) that has been calibrated on the REFTS, Table 2: Reorganization of CISPR 16 1 Conformity JULy 2008

Table of Contents Feed for the Digital Edition of Conformity Magazine - July 2008

Conformity Magazine - July 2008 Contents Editor's Note FCC Adopts 6 Million Dollars in DTV Enforcement Orders Commission Enforcement Bureau Adopts V-Chip Consent Decree FDA Seeks 2 Million Dollars from Medical Device Manufacturer FDA Answers Questions About CFLs and UV Radiation EPA Issues Energy Star Specs for TV, Video Boxes Canada Unveils Sweeping Product Safety Legislation How the Evolution of CISPR Standards Continues to Shape the Requirements for Anechoic Chambers ESD Open Forum Reach Compliance for Non-EU Article Manufacturers The iNARTE Informer Preamplifier Considerations for Emission Measurement Systems Effective Shielding in Medical Electronics Applications Product News Focus On...Power Components Buyer's Guide Updated Standards List for the EU's ATEX Directive EOS/ESD Symposium Set for September CPSC Actions in the News Researchers Work to Develop Non-Flammable Batteries Safety Link Launches Redesigned, Enhanced Web Site IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our "You Can't Make This Stuff Up" Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - July 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.