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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 project was created on 06/30/2014 and last updated 6 months ago.

Description
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.
Details

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.

Components
  • 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.
  • 3 × Susumu PAT1220-C-3DB-T5 Susumu 0805 PAT series 50-ohm pi attenuators, specified up to 10 GHz. I will tweak actual values later.
  • 30 × Assorted capacitors, resistors, a couple of LEDs, 3.0V LDO and a couple small FETs.
  • 4 × Several assorted opamps - LM358, MCP6001, OPA2228s, MAX477 Various functions - IF video amplification, triangle-wave oscillator, DAC output gain, active filters
  • 1 × Microchip MCP4921 SPI 12-bit DAC for VCO modulation waveform synthesis - arbitrary function.

Project logs
  • Vision with microwaves

    6 months ago • 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

    6 months ago • 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!

    9 months ago • 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! :)

View all 24 project logs

Discussions

Agung wrote 3 months ago -1 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 5 months ago point

Hi,

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

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Jasmine wrote 11 months ago 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 11 months ago point
Hi Jasmine, I will put an update up and some code online this weekend. :)

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rafael.menezes wrote a year ago point
If you need help with the algorithms, I have some background.

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J Groff wrote a year ago point
I wonder if the ultrasonic processing firmware would function with tweaks to constants?

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pfeffer.marius wrote a year ago 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 a year ago 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 a year ago 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 a year ago 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 a year ago 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 a year ago point
Great project! I'd love to learn more about your plans for echo processing. Any algorithm details?

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