Tuesday, November 22, 2016

A Clever Second Use for A Radar

In May of 2015, Google introduced a miniature radar chip called Soli to it's developer's conference.  Soli is a specially designed system that's intended to allow gesture controlled interfaces to the computer.  There are a few of these ideas being pushed to enable this technology.  We talked about one in this space back in July, a wearable armband called Myo that embodied accelerometers to sense the user's movement.  Other approaches appear to be based on cameras.

Soli departs from those approaches and goes to radar.  Conventional radars don't have the time/space resolution to detect subtle movements, but Soli does. 
Imagining gesture interfaces on everyday objects is particularly intriguing: ATAP used the example of an analog radio where gestures control the volume and station. But it could be applied to any number of use cases. Soli's sensors can detect motion at a range of about two to three feet, Schwesig says, so any device you use within that range stands to benefit. Imagine dismissing smartphone notification with the wave of a hand or pressing your fingers together to play music from a bluetooth speaker.
Soli isn't real hardware yet, but Infineon, the semiconductor manufacturer that partnered with Google to build the chip, has said that it expects samples to be available in the first half of 2017 and production devices to go on sale in the second half.

This, as they say, is just about the end of the beginning.  Prototype hardware has been available for a while, and goup of experimenters at St. Andrews University in Scotland have almost stumbled into some interesting and unanticipated uses for Soli. They've found ways to use it to instantly recognize objects like metals or peoples' body parts and distinguish between them, according to a paper presented last month at the Symposium on User Interface Software and Technology.
The system, also known as Radar Categorization for Input & Interaction or RadarCat, trains itself with machine learning algorithms to read those signatures and assign them to an object. It has been shown to instantly identify things like sponges and smartphones, differentiate between copper and steel, and tell if a glass of water is empty.
What's going on here?  I have no details, but just based on what I know about radars, here's a couple of guesses.  There are two ways to get finer position resolution with a radar: use of higher frequencies for their shorter wavelengths and use of shorter pulses.   Higher frequencies have only gotten easier every year since just about forever.  There's a WiFi protocol called WiGig or 802.11ad that uses frequencies around 60 GHz for ultrabroadband WiFi.  Conventional WiFi is at either 2.4 or 5 GHz.  You might get bit rates around 100 Megabits/second with your WiFi network.  WiGig offers a couple of channels available at 6-8 Gigabits/second. 

Back in 2014, my mind was blown by finding that over a million WiGig modems had shipped (mostly in Dell laptops) in their first year of production.  Today, projections are for a billion WiGig chipsets to ship in 2021, not by 2021, just five years from now.  I had worked on a 60 GHz modem at Major Southeastern Defense Contractor before I left in '96; probably in the '94 time frame, and it was exotic, excruciatingly expensive technology (although kind of fun to work with!).

WiGig chipsets, if flexible in how they work, could fit into the range where the wavelength is small enough to see individual fingertips with adequate resolution.  A quarter wavelength at 60.0 GHz is .047", so it's very easy to get many wavelengths over a finger's width.  The other way of increasing resolution is by using shorter pulses, or pulse compression in the radar.  Shorter pulses are probably accommodated by WiGig frequency range hardware, too.  They offer just short of 10 GBPS data, so let's say a pulse is just one-ten billionth of a second long. That's 100 picoseconds and 6 full cycles of the 60GHz RF.  In 100 picseconds, the radar pulse travels 3 mm, 0.118". 

This is not to say they're using the WiGig band, I don't even know if they'd be allowed, but the point is that the hardware isn't that excruciatingly expensive and exotic technology any more.

As they say in the video, the reflection from various objects is different, and they let the system self-program to learn things (machine learning).  The more objects it's exposed to, the more it will be able to identify.   A really interesting side application of something never intended for that use.


  1. The application for signing for mute people has potential- the machine could interpret sign and vocalize through a speaker.

  2. 60GHz doesn't travel very far. It's right in the range where water molecules (I think) absorb the RF energy. It was extensively used for satellite cross-links, as it wouldn't penetrate the atmosphere, and so it wasn't susceptible to eavesdropping from the ground....

  3. This may revolutionize human machine interfaces. And I have no doubt there will be applications to come unimagined as yet.

  4. I was working radar design at 140GHz in 1985 (at a "major defense supplier"), and we were trying to push the envelope up to the next atmospheric window above that. SAW devices can handle whatever frequencies you want to build them for. Often overlooked, though, is scattering by atmospheric particulates and reflection characteristics of the surfaces around the desired target. Snow, for instance, is much more highly reflective at 94Ghz than at 35Ghz and causes real problems.

    You can get a lot out of antenna design, especially if you can take advantage of various polarization modes.

    BTW, drjim, some handheld tactical comm radios take advantage of the absorption at 60Ghz so the enemy cannot eavesdrop on you – or even know that you're around :-)

    1. And that's why they use 60GHz.

      When I worked at Hughes we were pushing up to over 300GHz.

      It's right around those frequencies where you start to use "Quasi Optical" methods, as standard RF practices start to fail....

    2. It's from oxygen, not water, but it's still a lot of absorption at 60GHz.

      As later comments show, that can be a feature or a bug depending on application. For satellites, it's used for space communications that can't be monitored from the ground. Tactical radios or tactical datalinks that can't be heard from more than a few hundred yards are out there now.

      In this case, assuming it is 60 they're using, they're working at contact distance, so who cares? In the case of WiGig, again, being a very local area is still fine. Better for security. I'm sure we've all looked at how many WiFi routers we can hear from around our neighborhoods. Do you really need to be heard from a quarter mile away?

  5. I suppose it is a neat option but I think we suffer from overuse of technology. My washing machine has 20 different combinations for types of wash. I always use one and never used the other 19. My dishwasher has 3 or 4 different cycles I mean WTH just wash the stupid dishes. I can't figure out how to prevent it from heat drying so I have to listen for it and open the door. My gas stove has an electric brain/controls. If power is out I can't even use the stupid gas stove; who the hell came up with that idea??? My wife's car keeps showing that the tire pressure is low; it isn't. So I put a piece of black electrician tape over it so we didn't see the warning anymore. My laptop has a hyper sensitive touch pad it causes me more problems than it's worth. I assume this radar gesture interface would be similarly problematic.

    I like the simple hard wired on/off switch, no computer controls and not 20 ways to do one simple thing. Even my stupid refrigerator has a computer chip in it, why? Simplify and reduce the costs.

    1. Just as I was about to hit "Reply", I got an email from Google Calendar informing me tomorrow is Thanksgiving. Imagine that!! Who would have ever not known tomorrow is a big holiday - except people who don't live in the US and don't care? That's another example. I don't use Google Calendar at all.

      I'm with you only in spades. If I my machine has 20 washing machine cycles, I want control over every aspect of them. Instead, my washer won't turn on "warm" water if it thinks the temperature of what's coming out of the tap is already warm. But wait, it's worse: that number is set by the federal freakin' EPA! They tell me my the water out of my cold tap qualifies as "warm" except for the handful of coldest days of the year. Last night my wife told me the water had turned on warm for the first time since last February. I think if I want to set my warm water to 107.3 degrees, it's none of the EPA's effin' business what I set it to! Instead, they say, "no, your water is 78 degrees and we think that's warm enough". We actually called out the service tech under warranty to tell him, "look: when I set it hot, the hot water tap comes on, but when I set it to warm, only the cold water comes on... it must be broken". That's when we found out it's an EPA regulation (which is essentially federal law).

      My gas stove allows me to turn on the stove by using a match or any open flame I want. On the other hand, it's a feature we asked for.

      The combination of federal over reach and appliances you can't control the way you want is the worst of all words.

      All of these features (20 wash types, the inflation monitors in the tires, etc.), what's called feature creep. It's because they try to add cheap little trinkets they can get to attract customers. "That washing machine has the basic cycles, but this one has a separate cycle for wool from llamas!"..."but we don't have anything made from llama wool"..."we might, and anyway, it has 20 cycles instead of 18, so it's better for the price".

  6. Ever seen the Two and a Half Men where Alan is showing Charlie how to do the laundry? Told him the washing machine would call him on the cell phone when it was done. Downhill from there.
    And I have a hand gesture for Google. Same one I have for the Feds.

  7. Great. Now we will be bathed in 60GHz radiation all our lives, in addition to everything else.

    Yet another thing evolution did not prepare us for and which will have unintended consequences unforeseen and unnoticed until 15 years in the future.