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radar Level measurement

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hemnath

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I would like to measure the level or distance using radar.

Found some IC with 24GHz or 77GHz?. FMWC or CW? Confused in selecting the part.

Can anybody suggest me some ICs?

Thanks in advance.
 

www.infineon.com/24GHz-Radar
I did not see any only-CW (unmodulated) IC's at 24GHz, they are all usually VCOs (so FMCW can be implemented).

At the moment I would not rely on such ICs for mass production, they are usually not worldwide available in high quantities to small companies. And still too expensive. Although it is perfect solution for mass-production in US/Europe. If you produce at least around hundred thousands level measurement sensors, price will be acceptable. At small quantities it can be still useful for reducing "time to market", or solve design complexity issues, although still not money-efficient solution.

Good example of IC for Ku-band LNB:
http://www.rdamicro.com/products/Detail_132.aspx (who interested please google for rda3560m datasheet) it is single chip downconverter IC for LNB. Eliminates dielectric resonator oscillator requirement. No need to use expensive external PLL / hittite VCO / mixer / etc. Just single chip that includes all required components. But again, not much information provided, no datasheets. I think good support starts with buying good quantities of such ICs.

For level measurement signal processing algorithm is very important, also antenna radiation pattern and radiating power. There are many hidden problems in this area.
 
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I imagine that RDA3560 can be used somehow for level measurement. But it seems that chip can only switch between few frequencies in Ku-band (LO_SEL pin), and can't do fine tuning, as there no PLL registers, etc.
 

most low cost systems do this with an impulse source on the transmit antenna, and a sampler on the receiver side using an "equivalent time sampler" to measure the round trip travel time. it consists of around $15 worth of parts.
 

Thanks for the information. Can you guys please provide the circuit diagram by using those ICs.

Also I have found TDC-GPX multifunctional High-end Time-to-Digital Converter. will it be used to measure the level measurement?
If its, how to do it. Please guide me.
 

ADF5901 how abt this IC for my application?
 

With ADF5901 you can build pretty advanced radar
https://www.analog.com/media/en/technical-documentation/data-sheets/ADF5901.pdf
Look at Figure 31. I wonder why it hase two tx channels with power control. From my point of view there are too many expensive chips in this example.
IC has RF INT DIVIDER output. I've seen FMCW sensor where similar IC was used without using divider output! I guess that sensor rely on "almost" linear tuning VCO curve. Additional ICs = additional cost.

Give an example of some company's product that is already on the market, or at least requirements of your application. What distance you want to measure (where is it, object, etc.)?

Currently popular methods:
For stationary objects: (L)FMCW (linear frequency modulater continous wave)
For moving objects: FSK or MFCW (frequency shift keying or Multi-Frequency-Continuous-wave)
note that MFCW is not FMCW.

Currently popular advanced methods:
MFCW + beam scanning, etc.

For level measurement, there are also some "know-how" that it is not obvious.
You can aslo consider
**broken link removed**
 

Of course it is possible. If i would design such level meter: first buy some sensors and see how rf part is made. Especially old or cheap models. There was a link on this forum about level meters, there was very good pdf about how it is made. I can search for it tomorrow. One of your links mentions 6ghz frequency, and tdr. All you need to know now is what kind of modulation is used for time domain reflectrometry in level meters. I am not sure how they obtain 2mm precision.. i read paper on fmcw focusing (fmcw autofocus maybe), it can be usefull. I am sure there are many papers related to design of level meters. So google for paprers, also patents on freepatentsonline. It will give understanding.

Some frequencies good for measuring different materials, Some can be attenuated by vapours too much. You need to do a little research before choosing frequency
 
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I am new to radar. Can you pls guide me from where i can start from.
 

According to FMCW radar equations:
Range_Resolution (m) = c / [2*BW(Hz)] where "c" is speed of light (3*10^8)

So, for 2mm range resolution you need 75 GHz frequency bandwidth, which is pretty hard to get.
 

In theory you can interpolate/accumulate at lower frequencies and obtain some 2mm semi-precision. Assuming that level does not changes rapidly over time. Or use different waveform, not fmcw. 70 GHz would be difficult even with ic. Easier with on-chip antenna. I personally do not like 70 GHz idea. Good engineering approach is to do all calculations on required power, etc from requirements. Do few design iterations. If you want fast results i suggest buying some sensor and try reimplement its dsp signal processing, it might be.not so easy. Then reimplement rf part. Also you can buy some rf Evaluation board for ic you mentioned. Actually it is years of learning and knowledge. I started to learn rf few years ago in my free time, and there always new questions arise. I do not know where to.start helping you. Maybe some pll and vco with receiving mixer and transceiver antenna evaluation board to play with it, give some feeling. Best results can be obtained with vna and spectrum analyzers, but they are very expensive.

Also you start with trying cheap sensors. Google for rfbeam and innosent.

- - - Updated - - -

Update:
you can start with buying:
1. Innosent or rfbeam sensor with modulation
2. Some cortex arm development board (stm32, tms320,lpc, etc.) With adc and dac.

Connect dev board to sensor, control sensor modulation using dac, get IF signal with adc, do some dsp processing, i guess it would be fft. After some time you will you will understand what is feasible, what part must be improved.
 
vfone said:
According to FMCW radar equations:
Range_Resolution (m) = c / [2*BW(Hz)] where "c" is speed of light (3*10^8)

So, for 2mm range resolution you need 75 GHz frequency bandwidth, which is pretty hard to get.
Click to expand...

hemnath said:
I agree. with the formula we require 75GHz to achieve this accuracy.
Click to expand...

Resolution and accuracy should not be confused.
What you need is accuracy, not resolution.
The given formula is for resolution, i.e. the capability to distinguish two close targets.
 
zorro, thank for your remark, it is very important! I did not understand that before.

Btw, here is something interesting:
http://www.smgsys.com/pdf/FMCW radar.pdf
26GHz, resolution: 1mm (!), accuracy:+-3mm

http://portal.endress.com/wa001/dla/5000000/2463/000/00/far_Micropilot_S_en.pdf
6GHz (!), some parameters like 3mm, 0.5mm

hemnath
just google, many interesting articles and advertisements. Many papers mention modulation scheme (fmcw, double fmcw, pulse mode, etc.) bandwidth, etc.. You can learn many from those papers and advertisements too!
Save all downloaded materials to folders, systematise your new knowledge, make development notes and calculations.
 
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Thank you guys. I shall start learning the design notes and design some circuits to play with it.

I thought of using the ICs which are already available in the market which reduces the complexity of designing the circuit. I have also listed some of them earlier.

If you guys could help me or show the overview of what other components to add with the already available IC, that could really help me.
 

Usually you need:
1) RF IC
2) OpAmp (operational amplifier). Sometimes two stages OpAmp
3) DSP, some ARM microcontroller with ADC input and DAC output

4) RF IC IQ -> OpAmp -> DSP ADC -> your software algorithm
5) your software algorithm -> DSP DAC -> OpAmp -> RF IC VCO frequency control pin

Also other configurations are possible. If there are some PLL with modulation registers, then it would be:
1) DSP alters PLL control registers
2) PLL+VCO working with some modulation
3) PLL sends sync signal to DSP or DSP sends control word to PLL to start one modulation period
 

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