DRCC: Interference from Other Vehicles?

That's not correct.

DRCC and other radar systems on cars do function by sending out a signal and timing the return. They don't do it as a narrow pulse but as long chirp where the frequency is modulated during the pulse. The difference between the frequency of the echo and the signal being sent out is an indication of the range and velocity of the object returning the echo. This technique is called FMCW (Frequency Modulated Carrier Wave).

The radars can suffer with interference from other radars but unless the timing is exact it does not normally cause a problem.

kevin

 

That article is describing the current state of the art. "The first part of solving that problem is having a more detailed point cloud. Software 8.0 unlocks access to six times as many radar objects with the same hardware with a lot more information per object."

Current radars output a list of objects where each object is a range, azimuth, velocity and intensity where there is a significant radar return - it is often described as a "Point Cloud" (although that term more usually refers to the output of a Lidar). An single vehicle will produce many returns - each facet in the body work or mechanical piece tend to give separate returns. Because they are all at similar range and moving at the same velocity they can be grouped together. As the technology develops the number of returns that can be handled and the resolution to which they are observed is improving.

There are some videos on this web site showing the data that is obtained from the radar Smartmicro: Automotive Radar Overview.

kevin

 

Is "FMCW" using Doppler technology? I used to work for Toshiba on Color Flow Doppler Ultrasound.

 

Yes - the Doppler of the return is used to obtain the relative velocity of other vehicles.

FMCW is not required just to get doppler but it can be used with ultrasonic systems to obtain range information.

kevin

 

Just for historic interest, my understanding is that millimetre radar WAS used in ww2 and was in fact a crucial strategic development in the battle against German Submarines, to protect the merchant navy and vital naval supply lines.

See List of World War II British naval radar - Wikipedia

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WW2 radar did not use millimeter radar. They used much lower frequencies. It wasn't until the magnetron was invented that even centimeter wavelengths were used that made airborne radar practical (H2S).

Although that link does use millimeters for the wavelength measurement in general the term is not used below about 20GHz (1.5cm).

Most modern day radar for aircraft or military uses use lower frequencies - in particular those around 3cm (~10GHz).

The DRCC uses 77GHz that is equivalent to 3.9mm wavelength.

kevin

 

Ok thanks. Looks like an improved cavity magnetron was developed by the British in 1940 and was in military radar by 1943 in the ASV III/XI radar which had a wavelength of only 32 mm. Not all that far off 15mm. But I don't dispute your knowledge of the terminology.

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My understanding is there are atmospheric attenuation effects that limit the range at these frequencies. I'm not having a lot of luck Googling references. Would you have anything handy?

The reason I ask is Alabama has a lot pine trees whose needles that match WiFi frequencies. The old 'Pringles' ad hoc network links didn't work so well in our area . . . especially when damp.

Thanks,
Bob Wilson

 

Some Wi-Fi (802.11b, g, and some n) uses the same 2.4 GHz range as microwaves. Newer Wi-Fi uses the 5G Hz bands (802.11a, some n, 802.11ac)
Bluetooth at 2.5 GHz may be prone to microwave oven interference too.

I work with Wi-Fi as part of my job.

 

Interesting thanks. I don't think the magnetron in radar was so relevant for the Battle of Britain which was an air force battle, but it was very relevant in the battle against German subs in the Atlantic which were crippling vital supply lines to the UK.

I agree that it, alongside the code breaking work at Bletchley Park (that was so very very inaccurately portrayed in the recent "movie" "Breaking the Code") were crucial to winning the war against Germany.

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Years ago I watched a PBS show about a secret that won world war II.

It had to do with radar that was developed for the projectiles fired at airplanes.
It was the biggest top secret at the time, at it lead to a huge advantage in shooting down enemy aircraft.

In those times, there were spotters that would estimate the elevation of incoming aircraft.
That info would be radioed to the defensive batteries. They would look up in a table for that specific gun
and adjust a mechanical timer on the individual shell so that it would detonate at the correct elevation.
It would the be fired at the aircraft and hit or miss.

With the radar, it generally hit. To help preserve the secret radar, they maintained the same procedure for firing.

So they had developed a vacuum tube circuit, along with a miniature transmitter and receiver, that would fit into
the casing with the explosive charge, and could survive the explosive launching via massive gun.

Impressive!

 

Sorry I named the wrong movie! The one that is recent and IMHO more fiction than history is "The Imitation Game".

Don't know whether or not it's right but the Wikipedia link I quoted says that the first microwave radar was deployed by the Allies in 1943.

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