Take A Deep Dive Into A Commodity Automotive Radar Chip

When the automobile industry really began to take off in the 1930s, radar was barely in its infancy, and there was no reason to think something that complicated would ever make its way into the typical car. Yet here we stand less than 100 years later, and radar has been perfected and streamlined so much that an entire radar set can be built on a single chip, and commodity radar modules can be sprinkled all around the average vehicle.

Looking inside these modules is always fascinating, especially when your tour guide is [Shahriar Shahramian] of The Signal Path, as it is for this deep dive into an Infineon 24-GHz automotive radar module. The interesting bit here is the BGT24LTR11 Doppler radar ASIC that Infineon uses in the module, because, well, there’s really not much else on the board. The degree of integration is astonishing here, and [Shahriar]’s walk-through of the datasheet is excellent, as always.

Things get interesting once he gets the module under the microscope and into the X-ray machine, but really interesting once the RF ASIC is uncapped, at the 15:18 mark. The die shots of the silicon germanium chip are impressively clear, and the analysis of all the main circuit blocks — voltage-controlled oscillator, power amps, mixer,  LNAs — is clear and understandable. For our money, though, the best part is the look at the VCO circuit, which appears to use a bank of fuses to tune the tank inductor and keep the radar within a tight 250-Mz bandwidth, for regulatory reasons. We’d love to know more about the process used in the factory to do that bit.

This isn’t [Shahriar]’s first foray into automotive radar, of course — he looked at a 77-GHz FMCW car radar a while back. That one was bizarrely complicated, though, so there’s something more approachable about a commodity product like this.

24 thoughts on “Take A Deep Dive Into A Commodity Automotive Radar Chip

  1. @11:30 “It’s mathematically computed, so it’s really pretty straight forward”. That sounds pretty typical for Shariariairiar, but for me it’s indistinguishable from magic.

    I also had a quick peek around for the BGT24LTR11 The chip alone is below EUR10, the development kit shown here costs around EUR150 while several “hobby level” outlets try to (it’s sold out) sell a different PCB with this IC for around EUR60 to EUR80.

    1. These videos are like an exploded-view drawing of my boat’s main engine. Laypersons look at it and say “yeah yeah, a little bit convoluted, but I get it.”

      But at the end of the day they can’t repeat the simplest details. “Pistons?” “It had!” “How many?” “Four, I assume. Wait. 6? Right?” “Naaaaaa, 9 of it.”

      1. Hearing 9 cylinders made me start trying to figure out how the designers could even balance that engine well enough to not vibrate itself to death, but then I remembered that you mentioned it’s for a “boat”. It must be a straight-9 two-stroke diesel engine for a ship then? I was assuming 4 stroke angles lol.Those things are crazy!

        1. Yes, crazy stuff. And it rattles like hell. Toothpicks are the tool to stop some noise from closet boards or other stuff.

          Boaty has a little more than 8000 TEU, so small thing.

  2. Has anyone managed to get data on the software command set for the BGT24LTR11
    Manufacturer wont give me anything other than the hardware datasheet.
    Anyone got a software library to drive this device?

    1. I don’t think this chip has a “command set”. Searching for the part number will lead you to application note AN472 which seems to describe how to integrate this chip into your own design.

      It’s definitely more complex than throwing a software library at it.

    2. Someone obviously didn’t look very hard… Going to the manufacturer website reveals application notes and even software integration documents. Most of which has all the documentation you need to integrate this into your project/product. That said, Adrian is correct in that this is not a trivial part that can be integrated with just a software library.

  3. “The degree of integration is astonishing here, and [Shahriar]’s walk-through of the datasheet is excellent, as always.”

    Rather necessary if anything is going to be a commodity.

  4. We use “fuses” in our chips, for trim at wafer test, before packaging. In our case they’re zener diodes of slightly different voltages, that we use as voltage references. In trim, during the wafer test, we have an algorithm that chooses which zener is the best match to the target, and once established, there’s a little mux in there that routes power to the switches that mux all the other unfavorable switches to the power bus and that pulse of power vaporizes all the other switches, leaving only the one (now permanently) enabled.
    We’ve also made chips that auto trim themselves by doing an initialization as they power up and choosing the best diode reference to use under the operational circumstances. Our customers HATED that because they want the chip to always behave exactly the same way, even if it’s not the best operating conditions. Hence we continue to use fuse burning as our primary trim method.

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