Kirt's Cogitations™ #224
RF Technology in Autos
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Cog·i·ta·tion [koj-i-tey'-shun] – noun: Concerted thought or
reflection; meditation; contemplation.
Kirt [kert] – proper noun: RF Cafe webmaster.
RF Technology in Autos
There are few things more compelling for considering the purchase of a new car than being far from home in
your old beater, and having the engine shake and rattle so violently that people on the roadside stare at you as
you drive by. The wisest of them would have been contemplating taking cover lest a part fly off. I knew the time
for such a catastrophe was nigh, but the hope was that the beast (my 1995 Mercury Tracer) could be pacified for
just a while longer. Alas, with no compression in cylinder #2, its days are over, and now I have to decide what
will replace it. The model choices are nearly overwhelming, as are the mechanical and electronic options (RF and
otherwise) available for them.
This will be my first new vehicle in more than 25 years.
I am no tree-hugger, but do consider myself to be an environmentally responsible person, so good gas mileage
will be a prime consideration (≥ 30 mpg/48 kmpg). The Tracer – or Trasher as I affectionately refer(ed) to it –
managed about 26 mpg traveling to and from work, with a 1.9 L engine and an automatic transmission. Based on some
preliminary research, it appears that gas mileage is generally really lousy on most vehicles, so that reduces the
It is dismaying to see that in the year 2007 most vehicles are not getting at least 30 mpg. Emission control
and additional safety structures/device devices are responsible for about a 10-15% reduction in mileage according
to my research, but come on, with all the computer feedback and engine/transmission technology available, 25 mpg
for a mid-size sedan is ridiculous. Even the hybrids barely eek out 40 mpg. The 1996 Mazda Protégé I had (before
somebody ran a stop sign and totaled it) was getting 40 mpg. Has power train technology and vehicle aerodynamics
stood still for a decade?
Speaking of hybrids, I would really like to buy one, but when considering the
real cost of ownership over the long run and realizing that for most situations there is very little advantage
from a gas mileage perspective of operating one, the additional expense cannot be justified. Many articles that
approach the evaluation in an intellectually honest way point out the necessity for replacing the battery banks
after about five years and the ecological impact of disposing of the old batteries in a landfill. The financial
cost is on the order of a few thousand dollars, and the eco cost is a lot of hazardous, heavy metals in a
reclamation depot. Most, if not all, of the lead-acid batteries get shipped to “developing” countries to be
processed by workers who are lucky to be provided with rubber gloves and an exhaust fan.
Some hybrids use NiMH (nickel metal hydride) cells, but they are also full of heavy metals and are even more
expensive to replace. Research is under way for the use of lithium technology batteries which are more
environmentally friendly, but need to be made less prone to explosion (I have linked to many fire-in-the-pants
cellphone news stories over the years). As with plasma displays and HDTV, I will let the wealthier amongst us
finance the technology development and cost-reduction before buying one myself. However, I will be the biggest fan
(which is actually a short form of “fanatic”) and enthusiastic promoter of those who perform and underwrite the
financial cost of development.
On to the real topic of this article: RF technology in automotive products.
The science has progressed far beyond having your iPod broadcast over the FM band so your $2k, eardrum-popping,
500 W stereo system can blast it through a dazzling array of crossover-networked speakers. Hands-free (Bluetooth)
cellphone interfaces are mere 20th century technology, as are keyless entry systems and radar detectors.
Throughway SpeedPasses for toll booths have been around since the early days of RFID. OnStar™ emergency reporting
systems debuted in the 1990s and satellite radio in the late 1980s. That was then; this is now.
One of the
most impressive developments (IMHO) is the object detection system that uses radar, sonar, or a combination
thereof to gauge the distance to nearby structures or items to help prevent bumping into the side of a building or
running over a tricycle or most importantly, running over a living being. These systems have been adapted to
assist in tasks like parking where curb distance measurements are displayed to the driver, and in parallel
parking. Taking the science to an extreme, BMW and Lexus are now running commercials for a car that will parallel
park itself or back into a parking space with no help from the driver.
Collision avoidance systems (CAS) employ radar to survey the area surrounding a moving vehicle and search for
potential hazards like a car moving into your lane with too little clearance, and vehicle making a sudden stop
ahead of you, or a truck calculated to be on a collision course with you. An appropriately urgent warning is
generated for the driver, and in some cases the CAS will take evasive action independent of the driver (such as
applying the brakes). Both the CAS and the aforementioned automated parking systems will take a lot of faith on
the part of the driver to allow an inanimate object to basically commandeer the vehicle while in motion.
Somewhat less extreme, but impressive nevertheless, are gadgets like the tire pressure monitoring system (TPMS)
which consists of a MEMS based silicon sensor and RF transmitter inside each tire (sometimes in the valve stem)
that sends real-time data to a receiver for inclusion in the vehicle health status report. There are also efforts
underway to replace all of the control wiring for electrical systems in the rear portions of the car with
Bluetooth-like communications that will allow only a single high current bus wire to be distributed to items such
as the tail running, brake, and backup lights, and allowing the local wireless controls to do the switching. Doing
so saves weight and simplifies the wiring harness.
All of the advancements have come about due to the
brilliance of the people who have pioneered MEMS devices and the miniaturization and integration of entire complex
RF systems onto a single piece of silicon or GaAs. Of course, a lot of credit goes to the manufacturing engineers
who have figured out how to produce the products in high volumes and at an affordable price. Such feats are
inspiring to the next generation of engineers and scientists who will take it upon themselves to push the
boundaries even farther. Finally, some of the whiz-bang technology that was promised us for the 1990s, by
magazines like Popular Science and Mechanix Illustrated, are coming to fruition.
…well, except for the 100 mpg cars.