Conformity Magazine - September 2007 - (Page 32)

July 2007 compliance deadline now upon us (for products that were already on the market when the requirements went into effect in July 2006), we thought this would be a particularly timely opportunity to share some of our initial findings on the DFS testing and certification process. Don’t Assume that your Product Will Meet the DFS Requirements the First Time it is Tested In today’s highly competitive electronic manufacturing marketplace, most companies operate as close as possible to the speed of light in order to beat their competitors to market. This generally means squeezing every single unnecessary delay out of the product development process, and often results in commitment, to product release deadlines that can be challenging (if not impossible) to meet. We have found that many of the products we have tested failed to meet their DFS requirements on the first pass. Although many of our clients have come to us with the expectation that they would be able to complete their DFS testing in just a few days, more often than not, once the DFS test set-up are in place and the initial measurements begin, we quickly find problems with devices in meeting the radar detection requirements, the channel move time requirements, the channel availability check requirements, or all of the above. Many of our clients have had a particularly difficult time meeting the detection requirements when subjected to the bin 5 waveform, specifically with regard to the timing of the bursts. When these failures occur, the formal testing process comes to a halt while the manufacturer addresses the source of the DFSrelated problems. This can take anywhere from a few days to a few weeks of concentrated troubleshooting and debugging effort, and the testing process is essentially stalled during this time. So our first words of advice to manufacturers of products affected by the DFS requirements are plan accordingly and allow sufficient time to address your DFS testing needs. DFS is Primarily a Software Issue – Get the Software Developers Involved as Early as Possible! Another common misunderstanding that takes place in the DFS certification process is the belief that the testing requirements can be handled solely by the manufacturer’s hardware engineering team or compliance management team. It is important to understand that DFS is primarily a software (or firmware) issue so, when problems arise, the software developers often need to get involved to assist with resolution. Signal Radar Signal #1 Radar Signal #2 Radar Signal #3 PRF 700 Hz 1800 Hz 3000 Hz Pulse Width 1μs 1μs 1μs Burst Length 26ms (18 pulses) 5ms (10 pulses) 100ms (300 pulses) It is ideal to have a member of the software team present during the testing process to address problems as they arise, and to help keep the testing program on track. Furthermore, simply preparing a product to begin a formal DFS testing program can sometimes be a challenging task in itself. Many manufacturers going through the process for the first time fail to understand all of the specific modes of operation that a product must be able to demonstrate during the testing process. For example, any product being tested for DFS compliance must be able to operate in “passive scan mode” while using any of the DFS frequencies (the 5250-5350 and 5470-5725 MHz bands). But, manufacturers sometimes show up for testing with their devices unable to meet this requirement, and often require support from their software team to modify the device for testing purposes. As the software team may rarely (if ever) get involved in matters related to product compliance, this process can sometimes be a time-consuming challenge. In addition, various other software-related issues may arise during the testing process and that is why our second piece of practical advice is get the software developers involved in the DFS testing process as early as possible. Don’t Underestimate the FCC Turn-Around Times for DFS Grant Approvals This is a critically important factor for manufacturers of products affected by the DFS requirements to understand, as it will have a direct impact on their ability to meet their product release deadlines. Currently, the FCC will not allow Telecommunication Certification Bodies (TCBs) to certify grants for any DFS “Master” devices or for DFS “Client” devices that have ad hoc radar detection capabilities. TCBs essentially exist to expedite the FCC grant approval process for electronic product manufacturers, and many of those manufacturers have grown accustomed to the relatively quick turn-around times that TCBs can provide in the grant approval process. However, since the DFS requirements are still fairly new, and since they deal with matters of critical importance (i.e. military radar system interference), the FCC is currently conducting testing in its own lab on all devices submitted for DFS approval. Furthermore, a representative of the National Telecommunications and Information Administration (NTIA) must be present to witness the testing as it takes place. The only exception to this rule is for devices with no radar detection capability, which are the only type of DFS grant applications that TCBs can currently process. Hopping Rate n/a n/a 1kHz Table 1: FCC-03-287 Radar Parameters 32 Conformity September 2007 It has been our experience that the approval process typically takes about 23 months from the point when the DFS grant application and product samples are submitted to the FCC. However, in cases where the device is particularly difficult to set up for DFS testing, or where the

Table of Contents Feed for the Digital Edition of Conformity Magazine - September 2007

Contents Editor’s Note FCC Extends Disability Access Requirements to VOIP Commission Fines Importer $3 Million Over Non-Compliant TVs FCC Gets Tough on Retailers Over Analog TV Tuner Labeling Analog Cellular Service Sunset Date Reaffirmed Commission Adopts Recommendations of Katrina Panel Free-Space Antenna Factors Through the Use of Time-Domain Signal Processing Editorial Correction ESD Open Forum An Update on Revisions to IEC 61000-4-2, the Basic Standard on ESD Practical Advice for Meeting the DFS Testing Requirements of the FCC The EMC Impact of Embedded Software ESD Design Buyer's Guide Tate Renominated to the FCC EPA Releases Report on U.S. Electronic Waste Additional Standards For The EU’s Toy Directive Medical Device Manufacturer Enters Consent Order Updated Guidance Document on Laser Products Issued FDA Offers Advice on Defective Heating Pads CPSC Issues China Product Safety Program Report Other CPSC Actions In The News IEC Standards Update Product Reviews Product News UL Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - September 2007

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