Simple, low-cost FMCW radar

A basic radar system makes radar accessible at low cost for experiments with rangefinding & navigation of autonomous aircraft or spacecraft.

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This relatively compact, cheap, simple FMCW radar operates in the spectrum around 5.8-6.0 GHz and is aimed at lowering the barrier to entry for experiments with radar and general education around RF/microwave electronics. It is capable of speed measurement, rangefinding and SAR imaging (with appropriate moving antennas or a moving vehicle.) It is potentially applicable to experiments with autonomous aircraft (or spacecraft) altitude-finding, SAR imaging/mapping or navigation as an alternative to (or in addition to) other sensing techniques such as GPS, ultrasonics, LIDAR or barometry, without some of the limitations applicable to those technologies.

Frequency-modulated RF is generated by the Hittite HMC431 VCO at top left, at about 5.8-6.0 GHz, amplified by the HMC476 MMIC gain block at top left, and split in half by the Wilkinson divider at top center. Half the RF output from the divider is amplified again and sent to the transmit antenna connector at top right.

The local oscillator, from the other side of the splitter, is amplified again and applied to the LO port of the Hittite HMC219 mixer at bottom center. The reflected RF from the receive antenna comes in at bottom right, where it is amplified by the Hittite HMC717 6 GHz LNA and the amplified output is applied to the mixer.

A couple of pi attenuators are used, after the VCO, before the mixer LO port and after the mixer's IF output, to "tune" optimal mixer LO level and overall performance, although I haven't fixed certain values for these attenuators yet, space for them is left on the board.

IF filtering, amplification and signal processing, along with generation of the 0-10V modulation signal for the VCO, are done on a separate board. More details to come, as design, fabrication, revision and testing progresses.

  • 1 × Hittite HMC431LP4E 5.5-6.1 GHz GaAs/InGaP HBT MMIC VCO (voltage-controlled oscillator) with internal output buffer
  • 1 × Hittite HMC717LP3E 4.8-6.0 GHz GaAs PHEMT MMIC LNA (Low-Noise Amplifier)
  • 1 × Hittite HMC219AMS8 4.5-9.0 GHz GaAs MMIC double-balanced mixer
  • 3 × Hittite HMC476MP86 0-6.0 GHz SiGe HBT MMIC gain block (amplifier)
  • 3 × Molex 0732511150 50 ohm SMA socket, board edge end-launch style to suit 1.6mm PCB, specified up to 18 GHz.

View all 9 components

  • Vision with microwaves

    Luke Weston12/22/2014 at 11:32 0 comments

    It needs a bit of filtering and frequency domain analysis, Fourier stuff, to extract the information you want, eg range, or speed, or imaging, and discard the stuff you don't. But that's mainly a software problem - there's now an analog output ready for the computer.

    Sure, I can do basic proximity detection and rangefinding at the bench scale with existing ultrasound or infrared sensors, but this is so much more interesting.

  • Some new videos

    Luke Weston12/22/2014 at 11:28 0 comments

    Trying a video on the iPad for the first time, so sorry if the camera is a bit clumsy. I think it's actually a little bulky and awkward compared to using a phone.

    Here the voltage on the varactor is held constant, without any modulation, so the output frequency isn't being modulated.

    The only thing that comes out from the mixer is the frequency offset of the Doppler-shifted RF reflected back from a target that is moving. In this mode, spatial mapping or rangefinding is impossible, but measuring a target's speed, like a police radar, is possible.

    A stationary target produces no signal, no matter how close it is or what its radar cross-section is like. Much like the Tyrannosaurus that eats Gennaro in Jurassic Park, it can only "see" movement.

    And I just realised there's a typo in the title.

  • New video is up!

    Luke Weston09/29/2014 at 07:00 0 comments

    NOTE: This is an 8-minute video, I know it is slightly longer than the 5 minutes requested by the THP judges. I think you'll still get some valuable substance and overview of the project work thus far if you stop watching at the 5 minute mark... so hopefully they are not too strict about an extra couple of minutes. Hope that's OK :)

    Please enjoy, and feel free to let me know if you have any comments or questions! :)

  • Productive day.

    Luke Weston09/29/2014 at 06:59 0 comments

    See, you can see just how productive my desk is today! (I swear it's not usually this bad!). I guess you could call this a behind-the-scenes "how it's made" sneak-peek.

  • Gain block schematic

    Luke Weston09/29/2014 at 06:54 0 comments

    This is the schematic of my HMC476 "building block" module for prototyping. I'm going to have everything on GitHub for public open-source consumption shortly, but right now, you can enjoy a pic :) Please do comment if you have any questions. :)

  • New video coming!

    Luke Weston09/29/2014 at 06:45 0 comments

    In fact I am uploading it right now! :)

  • Where's the software?

    Luke Weston08/21/2014 at 04:36 0 comments

    If you're interested in software, you might be wondering how much software I have for this project, or where you can check it out. I've just put some code up on GitHub, you can check it out by following the sidebar link.

    Truth be told, there isn't much software right now.
    Part of the reason for this is that I'm focussing on the relatively tricky microwave electronics first, and getting the RF hardware platform working. Another reason is that some people (Greg Charvat, for example) have already created some fantastic signal processing software tools and shared their contributions with the world.

    I've put up my quick SPI test code, using an Arduino to drive a Microchip SPI DAC to generate a triange-wave modulation signal (this is amplified, as previously discussed, into an 0-10V signal.) However, this was just a quick experiment and it is unlikely that the finished product will use an ATmega328 microcontroller or Arduino-compatible bootloader. I'll continue to share any quick little software tests, tools or scripts as they come along.

    Another thing I'm currently working on is to take the MATLAB signal processing and visualisation scripts provided by Greg Charvat and the MIT/Lincoln Lab folks, and to tweak these for the best match to my hardware characteristics - and to replace the use of MATLAB with free software tools, since MATLAB isn't really the cheapest, most accessible choice. As work progresses, I'll continue to share these changes and new code that is written.

  • Bits and pieces

    Luke Weston08/15/2014 at 13:02 1 comment

    Here are a few little components I've been working on lately - reusable, modular, general-purpose building blocks for various RF experiments and R&D.

    - HMC431 VCO module with shielded can (top of can not shown)

    - A simple breakout board for SOT86/Micro-X RF gain blocks. (Top centre) This could be used with various MMIC devices in that package, from RFMD, Hittite, Mini-Circuits or various other manufacturers, they're all pretty similar. This board provides coupling capacitors, bias tee, power indicator LED, current limiting resistor in the MMIC supply rail, and a few decoupling capacitors. The passive values can easily be changed to suit different devices, so it's a generally usable module. An input attenuator is provided on this board so that the output power can be kept within the amplifier's linear region if the input power is too large.

    - HMC717 LNA breakout board (bottom centre).

    - Two different Wilkinson dividers, one of which uses a coplanar waveguide architecture (with top groundplane) and one of which uses more a microstrip approach (no top copper pour, fatter tracks compared to CPWG for the same given impedance.) We'll see if they exhibit any performance difference.

    - 20-DIP chip provided for scale reference.

    I made these boards with no solder mask at all - for a few reasons.

    (a) Because the thin dielectric layer of solder mask between the metal and the air introduces a slight error (admittedly it is small) into the physics (for impedance and width calculations etc) because it is not accounted for in the model. 

    (b) To see if the board fab would have any issues with it. (No.)

    (c) Because it makes it easy to see where all the signal traces are, makes it easy to shunt extra components between the signal tracks and the groundplane (eg. to add extra bypass capacitors), to cut the tracks and hack the boards in other ways, eg. adding extra attenuation, if the need arises.

    (d) Because it looks good. OOH SHINY. The slight disadvantage is that the solder looks slightly "messy" (although there aren't any shorts) where it spills across the ENIG groundplane.

    I did put a small region of solder mask underneath the 16-pin LNA, because with the 16-pin 0.5mm pitch QFN device I wanted to ensure it soldered successfully without any shorts or problems. (I haven't tested it yet, but to visual inspection it's good.)

    Mixer boards are coming, but they haven't arrived yet.

  • System block diagram

    Luke Weston08/08/2014 at 05:50 0 comments

    So, you like block diagrams? Here, have a quick sketch of a diagram. :)

    (Note: the attenuator before the mixer LO port doesn't need to be there; that's a mistake.)

  • VCO devboard / module

    Luke Weston08/05/2014 at 03:44 0 comments

    This is a little dev board / module with the HMC431 VCO on board. 14-DIP chip for scale.

    You could use this with any of the other Hittite VCOs with the same package and pinout to suit a different frequency range as needed, such as the HMC385.

View all 24 project logs

Enjoy this project?



kwapiszon wrote 01/16/2021 at 15:51 point

Zastanawiam się czy nie dało by się zrobić transmisji cyfrowej. Powiedzmy budujemy z metalu jakieś urządzenie jak francuzi i pokazujemy różne kształty.

Radarem zaś odczytujemy te kształty i na tej podstawie odczytujemy dane. Proste i wygodne. Jeden robot za ścianą macha pałeczkami a ktoś to odczytuje. Dało by się wysłac wiadomość do mastodon-ta

  Are you sure? yes | no

philippe.matthieu wrote 07/27/2016 at 20:54 point

Forgot my GERBER question. I just found it on site. Thx

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philippe.matthieu wrote 07/27/2016 at 20:50 point

Nice Project Luke, are you finish ? like MIT SAR, but much smaler ;-)

Will you upload Gerber and circuit schema ? It woul be great for my project ;-)

Anyway, I was pleased to see your videos. very helpfull.

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waleedmansha wrote 11/27/2015 at 05:34 point

Where can I get a kit or all the components for this project?

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Agung wrote 03/22/2015 at 16:38 point

Hello Luke, Nice to know your project. Is this kind of Radar are able to do some SAR operation, just like the Greg Charvat one.? This is really interesting for me, because now I'm doing some kind of experiment and study about radar using  Greg Charvat's model.

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dag wrote 02/19/2015 at 21:42 point


That's a great project, but which substrate you used ( Dielectric Constant, Thickness) while designing PCB of RF board ?

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Jasmine Brackett wrote 08/15/2014 at 22:20 point
Hello Luke, I think you have most of what we are requiring for the next round of The Hackaday Prize. The only thing I can't see is links to code repositories or software libraries. And remember to mention any licenses or permissions needed for your project. Best to document that information in the project details. Thanks for entering and good luck!

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Luke Weston wrote 08/16/2014 at 03:21 point
Hi Jasmine, I will put an update up and some code online this weekend. :)

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rafael.menezes wrote 07/24/2014 at 23:14 point
If you need help with the algorithms, I have some background.

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J Groff wrote 07/23/2014 at 20:44 point
I wonder if the ultrasonic processing firmware would function with tweaks to constants?

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pfeffer.marius wrote 07/22/2014 at 08:45 point
Have you thought about the legislations over the world ? Would be realy nice if this could be used worldwide.

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Adam Fabio wrote 07/14/2014 at 03:04 point
Nice work Luke! I love those Hittite chips - though they can get pricey! Thanks for entering The Hackaday Prize - with 10 project logs, you're doing a great job keeping the updates coming in! Don't forget about the video, and good luck on your way to Space!

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Luke Weston wrote 07/02/2014 at 05:26 point
I will probably start with some PC-based experiments building on the prior similar work of Greg Charvat and Tony Long, but I would also like to eventually have the ability for a lightweight, cheap embedded microcontroller system to digitize the signal and extract basic information such as speed or altitude for use in autonomous navigation of a vehicle such as a quadcopter or other UAV, autonomous altitude control etc. But this kind of software is one of the least mature, least developed parts of the project at this time. Thanks for your support :)

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zakqwy wrote 07/02/2014 at 11:43 point
Sounds like a great plan. There are a number of industrial products out there that use FMCW radar systems for level monitoring in liquid/solid applications; while the firmware is always locked down and proprietary, the manufacturers often share some details of the echo processing system. Worth a bit of research to get you started I'm sure.

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pfeffer.marius wrote 07/21/2014 at 22:09 point
Sounds great ! Currently it's not easy (and cheap) to measure the distance to the ground from UAVs which is realy helpful for autonomous landing or collision prevention.

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zakqwy wrote 07/01/2014 at 17:35 point
Great project! I'd love to learn more about your plans for echo processing. Any algorithm details?

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