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Radar/Wireless Transmitter on a Chip
dganapa writes "Researchers at the California Institute of Technology, headed by Dr. Ali Hajimiri, have developed a low-cost radar system on a silicon chip. The entire system has been designed from the ground up on silicon, thus leading to reduced cost as well as robustness in response to design variations and changes in environment. The chip runs at a staggering speed of24 GHz (enabling it to transfer data as fast as the main network of the Internet) and can soon lift wireless, high-frequency communication to a whole new level. The radar as such is not as powerful as a conventional radar but because of its cost-effectiveness, a number of them can be coupled together to perform really well. A related NY Times article is here. A recent article from Slashdot shows that radar technology is increasingly being implemented in the automobile industry. This current chip is sure to be much more successful than its predecessors as far as the automobile industry is concerned, but whether or not its processing speed will become important in the computer industry remains to be seen."
* The chip could serve as the brains inside a robot capable of vacuuming your house. While such appliances now exist, a vacuum using Hajimiri's chip as its brain would clean without constantly bumping into everything, have the sense to stay out of your way, and never suck up the family cat.
Not really. The radar might reflect off the cat or your leg, but would pass right through wooden furniture and walls. A radar-equipped vacuum cleaner would still bump into stuff.
* A chip the size of a thumbnail could be placed on the roof of your house, replacing the bulky satellite dish or the cable connections for your DSL. Your picture could be sharper, and your downloads lightning fast.
Wrong on size. Satellite dishes are big to both help collect enough RF energy to get a clean signal and to pinpoint on a single satellite. Without the needed collecting area and beam-forming span of the antenna, the signal would be weak and overlaid with signals from other satellites in orbit.
Two wrongs don't make a right, but three lefts do.
Is the frequency band at 24 GHz actually licensed for automotive radar systems?
According to this press release it's not licensed in parts of Europe.
And in the US, there is only a temporary license.
I haven't found an unbiased summary yet - the referenced press release is from a working group of companies in the automotive industry.
This summary says that the frequence is reserved for radio astronomy and similar users.
Lets see the most common American radar bands..
a nds.htm
X Band operates on ~10.5Ghz
K Band operates on ~22.4Ghz
Ka Band operates on ~34-35Ghz
(source: http://www.snooper-uk.com/radar_laser_speedtrap_b
The article states the frequency being used of is 24Ghz, so the only possibly problem might be with K band detectors.
I dont think they would put both in the same band anyway.. wouldn't that interfere with the radar guns themselves?
I'm not completely sure, but this site says that BellSouth's backbone could download the library of congress in 126 seconds- so it's gotta be pretty fast.
I found the NYTimes article dumbed things down a little too much. Basically, this is a press release by a fairly young professor about a ISSCC paper to be presented next week.
CMOS is getting fast enough (could be SiGe BiCMOS chip but probably CMOS) to allow for amplifiers and ADC (analog-to-digital) that work in the radar (~25GHz on up) range & also allows for million gate DSPs and digital logic on the same chip. The analog front-end is running around 24GHz which gives a 1/4 wavelength around 3mm (antennas are implemented as PCB traces off-chip). This is an analog GHz signal where the transistors are amplifying a tiny GHz signal using analog amplifiers. Digital clock speeds are completely different. Digital is like switching completely from off to on (ie. 0 to 5V -- in reality try 2V or 3.3V). This is like a uV signal being amplified to be later converted to a digital signal with a more reasonable bandwidth that a digital CPU could handle (like your overclocked Pentium).
The parallel analog antennas & blocks which allows for parallel ADC of 8 channels.. 8 parallel radar antennas. By using parallel processing you can use the information gained by the other channels to improve your ADC or have each channel only need to work at 1/8 of the total speed. Also, having 8 antennas allows phased arrays where you can control the beam and allows you to scan the beam or block out other signals (much like cell towers can focus in on one cell signal, and why your 802.11 router has two antennas). So, depending on how much bandwidth the ADCs need & how fast the DSP is running is really the 'digital' GHz part of the chip. So the digital processing is probably a more reasonable 100's of MHz (though hard to compare DSP speed to CPU speed). The processed digital waveform can be sent high-speed off chip, or to on-chip CPU to be used to disable your cruise-control and hit the brakes for you.
Why do you care? Well by using straight CMOS the radar system can be made on one chip and not need 'exotic' GaAs/SiGe/InP (BJTs of traditional radar systems) and when the automotive chips get down to sub-$5 they will show up in every car. Also doing it this way, much smaller power is involved and you don't need circuits that look like your microwave oven waveguides.
Well, looks like your math is right. But the resoultion of a radar is mainly determined by its bandwidth, not the carrier frequency. i.e. Shorter pulse = larger bandwidth = higher bandwidth.
Both Cadillac and Jaguar sell vehicles with Radar-based Adaptive Cruise Control, which will brake for you if needed.
Check out the Cadillac XLR.
Don't know; Don't care; Don't ask
It is indeed possible for a device to generate radio frequency with a wavelength greater than the devices physical size. A typical AM station generates a signal at a wavelength 600 meters to about 200 meters. Most AM stations do not have antennas this long and their transmitter boxes certainly aren't this size.
Frequencies can theorectically be generated with any size circuitry. Im pretty sure this circuit does so using the so called Phase Locked Loop (PLL) circuit, possibly mixing 2 or more together to get the very very very very high frequency by addition. This circuit does not require wire coils (often of relatively large size) to resonate at these "really" high frequencies. There would need to be a filtering step (or two or three) and I can see how this circuit would be hard to miniturize, but I guess they have done it!
Typically for a radio signal to be radiated you need at least a half wavelength antenna but even this can be cheated at. In the microwave region where this device is working at, signals are best radiated using a "dish" type antenna. This chip no doubt does not come with this dish. It simply generates the rf at 24 GHz.
ZBeat
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