[HN Gopher] MIMO Radar Antenna Arrays
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MIMO Radar Antenna Arrays
Author : parsecs
Score : 90 points
Date : 2021-05-15 05:57 UTC (1 days ago)
(HTM) web link (hforsten.com)
(TXT) w3m dump (hforsten.com)
| WJW wrote:
| Nice article! I used to work in this field and there is an insane
| amount of cool tricks you can do if you have enough signal
| processing available. The first (obvious) one is that, since you
| can switch beam direction as quickly as you can switch radio
| frequency (ie thousands of times per second) it is no longer
| necessary to give each target equal illumination time. It is for
| example possible to mostly focus on the missiles inbound to your
| vessel at mach 3 while still not losing track of all the other
| traffic in the area. You can't really do that with older
| mechanical antennas since the inertia would tear the assembly
| apart.
|
| The second is "colored space" radar, where you arrange the phases
| and wavelengths in such a way that the same transceiver array can
| generate multiple beams with different frequencies in different
| directions, giving true parallel beamforming (not merely
| concurrent as in the first example).
|
| Finally, though every textbook introducing these concepts uses
| transceivers arranged in a flat plane, that is not actually
| required. For example, the F-35 uses "conformal antennas" that
| are shaped like the rest of the airplane and uses a phenomenal
| amount of signal processing to convert the resulting signals back
| to "as if" the antenna had been a flat plane.
|
| I have always wanted to experiment with these things and
| rectennas to power small UAVs from afar so that they never have
| to land, but never got around to it.
| desertraven wrote:
| I have always been fascinated by powering devices with
| rectennas, but my research always turns up people "debunking"
| this, despite there being able research papers. Could you
| elaborate more on how you'd approach such a project?
|
| Also may I ask what your current field is?
| WJW wrote:
| A lot of people with proposals in this direction (most with
| only vague understanding about how electricity works, sadly)
| are wildly optimistic about the efficiency of wireless power
| transfer and wildly pessimistic about the efficiency of
| physical wires. I don't think wireless power transmission
| will ever replace large scale power transmission for
| terrestrial applications for example. It is also not very
| useful for powering small devices in (say) a room because the
| rectenna array need to be "facing" the transmitter and you
| can't guarantuee that for a phone in a pocket. You can make
| it up by increasing the power, but it's easy to show that it
| would need to transmit dangerous amount of EM radiation to
| get a reasonable amount of power to the device(s) in all
| scenarios. Hence the debunking.
|
| That said, if transmission efficiency is not your absolute
| main concern (such as would be the case when powering a
| drone) and you can control the attitude of the receiver array
| then it can absolutely be done. Apparently a Canadian
| research institute built a rectenna-powered plane all the way
| back in 1987 that could stay aloft for months. If I would go
| into a project like this it'd be interesting to see why they
| didn't continue with this and why "modern" long endurance
| drones typically go for solar cells on the wings instead.
| Tech-wise, getting some basic arrays up and running would be
| a good idea too. Finally, I can imagine that a certain amount
| of political goodwill would be needed as well, since high
| power phased arrays and long endurance drones have obvious
| military applications and most governments like to keep a
| tight lid on military tech (for good reasons).
|
| Current field is working as a combined Ruby/SRE freelancer,
| helping local startups fix speed up their test suites and
| fixing the sometimes terrible SQL queries ActiveRecord can
| spit out if you are not careful. Quite different from my
| previous field but a lot more freedom :)
| touisteur wrote:
| Oooh just give me a sensor array, infinite processing power and
| watch the digital beamforming, space-time adaptive processing,
| and millions convolutions dance...
| jcims wrote:
| Seems nearly impossible but it would be cool if SpaceX would
| open up access to the RF capabilities of their Starlink user
| terminal. Pretty impressive array for consumer electronics.
| aspectmin wrote:
| As to beaming power: Lasermotive worked on this problem for a
| while, but (to UAVs), but have recently renamed and are now
| working on delivering power over fiber.
|
| The UAV power problem is still huge (for example, the military
| needing to keep defensive, electric, UAVs aloft indefinitely vs
| very short linger times.
|
| https://en.wikipedia.org/wiki/Powerlight_Technologies
| JoeDaDude wrote:
| The folks at DARPA want to investigate the use of Machine
| Learning math and tools to control and process antenna arrays.
| See the Tensors for Reprogrammable Intelligent Array
| Demonstrations (TRIAD) program, referenced here:
|
| https://intelligencecommunitynews.com/darpa-releases-triad-a...
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