Re: OT - Radar Question


Rob, M0DTS
 

I have had a play with one such unit as used it modern cars, indeed they are now on 77GHz and i have tried to get one running on 76GHz cw...
I have not tried it with the original FMCW Radar operation, figuring out the CAN commands to enable it are beyond me but a custom VCO sweep would easily be possible and some clever dsp using the on board ADC would make a nice radar unit.
I have also got another unit which uses SiGe cmos RF chips but i have had zero success firing that up yet.

Some photos and progress so far is here:
http://m0dts.co.uk/index.php?tag=76GHz&item=179

Comments and further ideas welcome!

Rob
M0DTS

On 12/6/2017 6:37 PM, Andy Talbot andy.g4jnt@... [ukmicrowaves] wrote:
 
Aren't automotive radars more likely to be much higher in frequency, in the 30 - 50GHz region?.   There was talk over a decade ago about threats to, and band planning for, the 47 and 76GHz bands with automotive radar being cited.   Things have moved on and integrated SSPAs with phased array antennas perhaps with MEMs elements thrown into the mix are a cost effective solution now.    X-Band radar  is old hat - used for long range stuff!

I saw a proposal for a research study for MEMs devices as part of millimetric phased arrays back at the start of the millennium

Andy  G4JNT

On 6 December 2017 at 18:19, Christopher Bartram cbartram@... [ukmicrowaves] <ukmicrowaves@...> wrote:
 

Hello Richard

When, many years ago, I was sailing - before the days of cheap DSP - I made a little 10GHz FMCW handheld radar based on a varactor tuned Gunn oscillator and a horn, which I played with when sailing around the SW Coast. Like Kent's aid for the sight impaired, I simply used an audio amplifier. It worked, but was more qualitative than quantitative, particularly as my prototype had a sweep rate control . I did demonstrate it to a marine electronics manufacturer, but it was considered 'too much of a toy' to interest them! With the Gunn turned off, it was also quite useful when sailing in reduced visibility, as a passive radar detector which would provide some directional information.

The price of X-band PA devices is falling, but slowly. I'm quite often asked why I don't make a 10W amplifier, and the answer is still price. As the parts used in radars are likely to be prematched, it's probable that they will not work that well at 10.4GHz - but it would be an interesting project to try to make them do so.

73

Chris

GW4DGU


On 06/12/17 17:08, Richard Baker perwick@... [ukmicrowaves] wrote:
FMCW Radars are now popular on small seagoing vessels as they can be be all solid state and hence use less energy and hopefully be more reliable in a marine environment. The disadvantage is they need two antennas usually stacked one above the other in a single deep ray dome.

If the frequency sweeps are alternated between LF to HF and HF to LF (Chirp-up and Chirp–down) it is possible to get Doppler information as well as distance, bearing and intensity.

They work in the 9.3 to 9.4GHz frequency range with a typical maximum sweep bandwidth of 75MHz completed in ~1.3ms. They can have a range down to as little as 2 metres.

There is a fear than there will be mutual interference if you get a marine full of them all operating at the same time but I have not seen this yet.

They are effective collision warning devices on boats but distances are much larger and speeds less than half those seen with cars. I assume the technology is scalable to shorter distances and higher speeds using a phased array antenna to give very fast azimuth sweeps. Fortunately cars are not interested in targets miles away as boats are.
 
I wonder if the PA devices could be got to operate on 10GHz as they should become quite cheap with the economies of scale and are in the useful 2-10 watt range and designed for a 100% duty cycle.

Richard
GD8EXI


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