Synthetic Aperture Radar Autofocus and Calibration

Posted3 months agoActive3 months ago

nbernard

201 points

16 comments

hforsten.comTechstory

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Synthetic Aperture RadarRadar TechnologyDiy ProjectsSignal Processing

Key topics

Synthetic Aperture Radar

Radar Technology

Diy Projects

Signal Processing

The post showcases a DIY Synthetic Aperture Radar (SAR) project with impressive results, sparking discussion on the technical achievements and the conditions that enable such deep tinkering and innovation.

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Oct 8, 2025 at 1:11 AM EDT
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Discussion (16 comments)

Showing 16 comments

dang

3 months ago

1 reply

Related. Others?

Homemade polarimetric synthetic aperture radar drone - https://news.ycombinator.com/item?id=43073808 - Feb 2025 (60 comments)

shash

3 months ago

Same guy.

His work is pretty amazing actually. Lots of little details he’s worked out and built upon. Someday I’d like to replicate his designs.

ccgreg

3 months ago

1 reply

I had fun reading this -- the radio astronomy technique called VLBI (very long baseline interferometry) has a ton of overlap, but the jargon words are fairly different. There are plenty of differences: our telescopes are mostly on the surface of the Earth and don't move, VLBI isn't a radar so there's no waveform, etc.

The EHT black hole telescope is an example of VLBI.

shash

3 months ago

Very similar. To the extent that when I’ve worked on synthetic aperture I have used ideas from radio astronomy.

And there’s a similar field of synthetic aperture ultrasound which is where I did a ton of work a decade ago.

smath

3 months ago

2 replies

Slightly tangential: this is a wonderful and deep project, that requires a lot of personal time. Lately I've been wondering what social/economic/govt conditions allow for this type of deep thinking + tinkering among working people (not academia). My very rough guess is the US of 1950-60s did, and some other countries today do, but not so much the US of today because the cost of living and time pressures are higher. I'd be curious if anyone has a more detailed answer (or a rebuttal of my thesis altogether).

YZF

3 months ago

1 reply

1650-1750 Britain?

https://en.wikipedia.org/wiki/John_Harrison

https://en.wikipedia.org/wiki/Isaac_Newton

And I'm sure lots more?

Or maybe more generally Europe circa 18th century?

Probably a lot more creativity/discovery/"personal projects" vs. the US 50s or 60's would be my guess? So we need prosperity and a monarchy?

smath

3 months ago

A benevolent monarchy maybe - like some places in the east (maybe).or maybe UBI? Some way to not have to worry about basic health and needs

What places have this today? I see an answer suggesting AUS below. ChatGPT says Switzerland

selimthegrim

3 months ago

Seems like from anecdotal reports on HN Western Australia might be a place where these conditions still obtain.

aidenn0

3 months ago

1 reply

I recall a post on HN about a decade ago where someone made an SAR by modifying one of those toy radar-guns into an FM CW Radar and mounting it on his bike. After trying a few different position-estimation algorithms, he got the best results just by maximizing the contrast.

ThomasPw

3 months ago

1 reply

RE "....a post on HN about a decade ago ...." I tried to find (search ) this post but could not...

defrost

3 months ago

1 reply

Homemade synthetic aperture radar (2015) - https://news.ycombinator.com/item?id=10387360

https://hforsten.com/homemade-synthetic-aperture-radar.html

https://hackaday.com/2019/08/15/bike-mounted-synthetic-apert...

aidenn0

3 months ago

That's the one. I remember it was of a football field. Apparently I was confusing it with a different article where the FMCW radar was made from a modified toy radar gun though, since this radar appears to be made from scratch.

NoiseBert69

3 months ago

I'm an embedded engineer for 15 years now and did some really spicy stuff during my career.

This hobbyist SAR project made by hforsten absolutely nuts. Wonderful.

He mastered mechanics, electronics, software and applied higher math of the highest difficulty grade. Guess we have to call this "The Holy Quadrivium".

Back to the tech:

Radar stuff is very interesting. Reverse Engineering cheap FMCW radars from China makes these very accessable to hobbyists too. Often you "only" have to care about the VCO for the frequency sweep and then read back the I/Q channels using two sync'ed ADCs. Then you can play around with algorithms to analyze the signals.

These 24GHz Car Speed CW (you see next to streets) radars can be used for classifying rain drops for example. They antenna pattern is quite sharp and they have high gain.

ThisIsTheWay

3 months ago

Awesome work. SAR imagery is notoriously fickle, and it is amazing to see these results from a DIYer.

fithisux

3 months ago

This is an excellent article and great work.

We need more articles uncovering the SAR mechanics, even for Satellite Data.

ACCount37

3 months ago

This is mad in all the good ways.

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ID: 45512300Type: storyLast synced: 11/20/2025, 5:27:03 PM