Thursday, February 25, 2010

is EMI to blame for recent Toyota problems?

News outlets and internet blogs abound this week with stories speculating that the problems with some reported out of control vehicles may be related to EMI.

Anyone involved with Electromagnetic Compatibility will recognize that given the proliferation of technology in today’s automobiles, the conditions do exist for catastrophic failure of sensitive systems, and the potential is high for injury or death if such systems fail.

In traditional “analog” systems, these failures would tend to manifest in the form of glitches, or other minor system anomalies. Problems have been reported in the past with CB radio systems causing the electronic fuel injection to fail, causing the car to stall. More recently, and as systems are becoming more advanced, problems have been reported that cell phone calls have interfered with sensors causing the inadvertent operation of breaking systems.

In some of today’s vehicles however, with technology so advanced and systems so integrated into every aspect of the vehicles operation, it is virtually complete “fly-by-wire”. One can imagine the potential for disaster. Several groups exist that contain engineers devoted to such “imagination”, such as the SAE International, the IEEE and the ISO/IEC to name a few. Today, all major automakers have internal production controls and standards focused on Electromagnetic Compatibility, and most have been testing vehicles and systems for a couple of decades.

With many consumer electronic devices finding their way into the automobile, as well as cell phones and wireless headsets, the potential for interference is ever increasing. Automakers will need to address an ever changing EM environment.

With cost cutting measures driving the market, component suppliers are faced with tough decisions as to the extent of testing for product off the assembly. EMC testing is expensive, and testing everything that rolls off the line is impracticable. Some find, that one sample tested, is suitable to represent hundreds of thousands of units. Others may find that outsourcing testing can save thousands of dollars, but the tradeoff here is that these labs may not operate under the same tight controls as local accredited test labs, so the uncertainty in the results may be too high.

It is in fact not possible to know if EMI is the cause of a particular incident without extensive research and testing, it would seem that the phenomenon would be on the short list of suspects for now, however.

Thursday, February 4, 2010

Antenna Calibration Procedure

The wave reflected by earth can be considered ...
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The office of Engineering and Technology, Laboratory Division, released a public draft review regarding proper antenna calibration procedure.
The document answers the question;
“What procedure should be used to calibrate antennas used to make radiated emission measurements and normalized site attenuation (NSA) measurements”?
According to the public draft review, the revised ANSI standard, ANSI C63.5-2006 provides the proper procedure and is based on a horizontally polarized measurement performed on a standard antenna calibration site at a 10 meter distance.
Antenna factors collected in this manner can then be used for vertical or horizontal measurements at distances of 3 meters or more.

Monday, February 1, 2010

Company fined $10k for impacting weather radar near San Juan airport

Map of the Bermuda Triangle
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Terminal Doppler Weather Radar (TDWR) serving San Juan International Airport received interference adjacent to 5.61GHz, source tracked by FCC and FAA agents to radio transmitters providing wireless internet atop a nearby building.
The company responsible for the interference was issued a forfeiture order by the FCC enforcement bureau in the amount of $10,000. While the company used equipment that had been previously certified under the FCC rules for UNII operation, the equipment causing interference was operating on frequencies that it had not been approved for. Moreover, if the transmitters would be considered non-UNII devices and subject to section 15.407(2) of the FCC rules, then the power allowed would have been limited to ¼ Watt in that particular frequency band, however, the devices in question were designed to operating in excess of three times that level.
The full FCC forfeiture order can be found at