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How to make a homemade doppler radar

How to make a homemade doppler radar

The low-end stuff that we can get our hands on usually suffers from poor range, lack of sensitivity, and no way to characterize what the target is. But today we can use the good stuff that, until recently, was only available to military: radar. In this post we will discuss how radar works, commercially available small radar devices, and where to learn more to help make it easy to add radar to your next project.

Reach out and sense something! Radar is simple, it consists of a radio transmitter and receiver. Radar is a World War Two acronym meaning Radio Direction and Ranging, in other words a radar consists of a radio transmitter and receiver where the range to an object is measured by clocking the time between the transmitter transmitting a known modulated waveform and the receiver receiving this waveform scattered from a target.

One enabling technology for Radar was the cathode ray tube CRTwhich facilitated a method of measuring the time delay between transmitted and received waveforms.

This led to the development of numerous radar sensors used in the second world war, which generally followed the Plan Position Indicator PPI architecture. Toady, rather than using a CRT we can use high-speed digitizers. This offers the obvious advantage of applying signal processing to acquired data so that only moving targets are detected, tracking can be achieved, imaging, and a multitude of other modes.

But for hobbyist and consumer projects we do not need this much power, range, and can not afford the cost. We need the ability to sense like a long range radar detecting only moving targets, imaging, Doppler, signatures, etc but at short ranges and at low costs. Very few off-shelf small radar options exist as of today. If you are not interested in ranging or imaging but would like to measure velocities or radar signatures then consider CW Doppler radar.

CW Doppler radar works by feeding the output of a CW oscillator to an antenna and radiates that carrier towards a moving target. This carrier scatters off the moving target back to the receive antenna where it is amplified and fed to a frequency mixer. The mixer mixes the oscillator and the scattered carrier resulting in a Doppler shift product.

Low enough to be easily digitized by the audio input port of a laptop computer or other low-cost digitizer.

Try a CW Doppler radar.

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If you find an old motion sensor or door opener. These typically use CW Doppler radar modules known as Gunnplexers. Hack into one just as you would with the Police radar. This may not matter for your project. Short range radars sense at m or less. At these short ranges extremely short pulses meaning short in time duration, nS or pS in duration are required to provide sufficient resolution to be useful.

Short pulse, or impulse radar systems, generally follow a simple architecture where the impulse generator is often tied directly to a transmit antenna and a low noise amplifier LNA is tied to a receive antenna. A high speed digitizer is triggered off the impulse generator and acquires data on the output of the LNA.

You can incorporate impulse radar technology into your next project. Commercial versions of impulse radars are available to hobbyists and developers.Previously I made a simple frequency-modulated continuous-wave FMCW radar that was able to detect distance of a human sized object to m.

It worked, but as it was made with minimal budget and there was a lot of room for improvement. If you have read my previous articles you should know how FMCW radar works, but for completeness sake short explanation is given below:.

This chirp is then radiated with the antenna, reflected from the target and is received by the receiving antenna. On the reception side the received signal that was delayed and undelayed copy of the transmitted chirp are mixed multiplied together.

how to make a homemade doppler radar

The output of the mixer are two sine waves that have frequencies of sum and difference of the waveforms. The frequencies of the received signals are almost the same and the sum waveform has frequency of about two times of the original signal and is filtered out, but the difference waveform has frequency in kHz to few MHz range. The difference frequency is dependent on the delay of the received reflection signal making it possible to determine the delay of the reflected signal.

The electromagnetic waves travel at speed of light which allows converting the delay to distance accurately. When there are several targets the output signal is sum of different frequencies and the distances to the targets can be recovered efficiently with Fourier transform.

The biggest issue with the previous version was noisy power supplies causing spurs in the received signal, ADC sampling clock not being locked to PLL reference clock and microcontroller being too slow.

To save money I had chosen to use two buck converters to power all the digital and analog components. Even though I chose the switching frequency of the converters to be above the IF frequency, there ended up being some spurs also at lower frequencies.

Adding capacitance and swapping the inductors for better shielded ones helped the problem but didn't completely solve it. The proper fix is to add linear regulator after the buck converters to clean up the switching noise.

However when trying to measure heartbeat and respiratory rate the added phase noise from the varying sampling interval caused some noise in the measurements. Noisy power supplies also degraded the phase noise performance. The microcontroller I was using was pretty powerful compared to the cheapest 8-bit microcontrollers, but it was hopelessly underpowered to do any kind of digital signal processing.

Even the samples between the sweeps that didn't have any useful data were transferred to PC only to be discarded later. With more resources it would have been possible to do digital filtering, lower the sampling speed and only transfer the useful samples. Microcontrollers don't really have enough processing power to do any kind of non-trivial filtering. For example a tap FIR filter requires multiplications and additions for every sample.

Even if the multiplication could be done in one clock cycle the maximum sample rate is too low to be useful. The microcontroller should also have enough processing power to transfer ADC samples and do communication and other logic.

The last improvement is adding a second receiver antenna. When there are more than one receiver antenna it is possible to determine the direction of arrival of the received signal. If the return signal arrives in angle it is received at different antennas at different times. The different arrival time causes a phase shift in the IF signal which can be used to determine the direction. Since I'm not changing the transmitter, the maximum range performance should be pretty identical to the last version when using the same horn antennas.

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When smaller patch antennas are used as receiver antennas the range is going to decrease because the gain and efficiency of the patch antennas is smaller. Most of the values are easy to determine, but the minimum detectable power can be tricky. Clearly the minimum power that can be detected depends on the noise level of the receiver. Determining the correct noise bandwidth to be used is critical and easy to get wrong.

Noise bandwidth is clearly smaller than the sweep bandwidth since the IF filter filters most of the RF noise out. IF filter bandwidth determines the noise power that makes it to the ADC, but that is not the noise bandwidth to be used since some of the noise can be clearly filtered out after taking the FFT.The post explains a GHz microwave radar security alarm circuit which is designed to detect an intruder within the critical zone only while it's moving, static objects produce no effect for the sensor.

In the previous article we learned about a microwave Doppler radar sensor module KMY 24 which is a Hi-end sensor device capable of transmitting a sample signal in the GHz range across the set zone until it's reflected from a moving object back to the sensor for the necessary processing. In the following discussion we will see how this module can be suitably rigged with opamps for enabling the detected signals to be amplified and fed to an appropriate load such as an alarm or a relay driver stage.

Referring to the above GHz microwave radar security alarm circuit we can see the sensor module KMY 24 configured with the first opamp stage using N1 and the associated components.

Basically N1 is wired up as a differential error amplifier, wherein its two inputs are hooked up with the two differential outputs of the sensor unit. When a moving object or target is detected in front of the sensor module the reflected GHz signals go through a relative phase shift which is reflected back to the sensor and is processed inside the module producing an equivalent positive or negative response across the center two pinouts of the KMY 24 module.

This difference in voltage is fed to the two inputs of A1 which detects this and generates an equivalent amount amplified differential voltage across its output pin 1. A2 is configured as a filter stage which monitors the output from A1 and filters the unwanted spikes that might be induced at its input and feeds a clean amplified differential signal to the next opamp N3 stage.

N3 is connected as an impedance matching or transforming stage, which processes the fed differential input from N2 and converts it into a distinctive high or low pulses across its output pin 8, which becomes compatible to be used with either a DC alarm stage, relay driver stage or even a Microcontroller input.

Thus the GHz microwave radar sensor alarm circuit may be used as a security system for detecting even the slightest of movements from an intruder within a 6 meter range from the sensor's emitting point, and convert into an alarm or any desired triggered output. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

Your email:. Could you please help me finding it. Although I don't need it in bulk, but I would like to work with it if I get successful with this model on regular basis. Swagatam Majumdar ji, this is one of the best diy sites I have seen.

Hats off. I am not sure whether this would be available in common electronic part shops because it could be quite costly and not a high selling component. I am aware of its cost as I am already using HB So kind of you to reply on my comment. Kindly see if you or anyone on the Post could help in finding KMY OK, if possible I'll inquire with my local dealer and ask him whether it is available or not in the main market Lamington Road. I want to build one stereo amplifier 2w 2w,for my pc.

I want to add volume control and bass control. Suggest me a design with minimal noise and cheaper also. Now the motors are forward moving. But when obstacle is present the microcontroller cant change its port states. For ur reference m nt using a readymade kit. I have assembled the whole control ckt using atmels series chip and ld motor driver.

If u have any article regarding this. Everythings ready and when i assembled it to check, it was not making the motors on. Strangely when i was testing the voltages of the pins of controller and motor drivers by touching DMM probes, it suddenly running the motors forward… iam afraid bcoz its my final year project and exam is knocking at the door.

Your suggestions will be greatly appreciated. Hello Pritam, it would be quite difficult to judge the fault just by imagining, sorry no ideas, you may have to consult the local dealer from whom you purchased the kit.

Comment Policy: Dear Friends, 1 Kindly make sure your comments are related to the article topic, for example a motor related comment should be posted under a motor related post, a battery charger question under a battery charger post, voltage control under power supply article and so forth Thank you for your consideration!

Your email address will not be published. Notify me via e-mail if anyone answers my comment.It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher compared to the emitted frequency during the approach, it is identical at the instant of passing by, and it is lower during the recession. Hackaday featured plenty of projects using this effect: a small doppler motion sensorgesture control using doppler shifthacking an old radar gun.

how to make a homemade doppler radar

Any possibility of using this for weather radar? Amateur radio is experimentation, no daily exploitation. Sending microwaves and receiving echos is possible with this kind of experimental device, which is very cool. In France we have an official W tx limit, I assume some kind of limitation also applies in other countries.

Not to mention the extreme danger of high power RF radiation, and the difficulty to get meaningful results. And people trying to receive small signals would have reason to become mad if some device was sending such strong signals degrees away! I would have to look at the US regulations more.

How to Make a GHz Microwave Radar Security Alarm Circuit

I know the 1. Second sending it into the sky will not bother anyone. Perfectly acceptable to make ham radio weather radar.

Except for the power limit. There are also additional restrictions in part One way emissions, unless of a type specifically authorized i. Radar is not a specific exception.

Also, what could the pulse emission type be for if not for radar? Anyone know for sure? Instead of bouncing off a natural satellite, you are bouncing off the car in front of you or nearby clouds. One-way communications are banned, except for a specific list of exemptions.

He chose a poor frequency also. Not sure if this is in whole Europe or my country only. Like Dodo said the 9. A better version is coming up…. You cannot operate the same type of radar on land, though. You might notice intermittent illegal transmissions is punishable by five years, ten thousand dollars, or both per day.

The transmission regardless of time you transmit is considered a day.Did you use this instructable in your classroom? Add a Teacher Note to share how you incorporated it into your lesson.

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I cant get the processing code to display anything but a static image it doesn't show anything even when i put my hand in front of the sensor.

Reply 2 years ago. I f possible could you please send me a more elaborative version of comments for that piece,asap. Hello please specify the Position of programming you didn't understand. Reply 3 years ago. Excuse me ,if i want to use two of ultrasonic or more than 2 by to show on radar system which i will to use IDE Processing and IDE Arduino program in working. What should i do.

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Hello you can use 2 ultrasonic sensor but that will be much more complicated. My arduino uno r3 is connected to com6, so i changed the [0] to [6], but it doesn't run Reply 4 years ago on Introduction.

I'm not familiar with processing but I assume it's quiet the same as in every other programming language. The thing you get by calling Serial. Now in your case calling the function Serial.

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Hi, This is so far the closest I've seen to displaying ultrasonic visually. What I am trying to do is make my own Ultrasound Device, similar to the machines that are used in hospitals to see a baby in someone's belly.

Is this even possible with these components or am I looking for something that is not available? By ujash patel Follow. More by the author:. Add Teacher Note. Did you make this project? Share it with us!

I Made It! Reply Upvote. Baasil Biniyamin 2 years ago. MansiB5 2 years ago. TomLamaker 4 years ago. Thanks for sharing this amazing project!

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I do have one question though: Is it possible to display the radar you made on your phone using a bluetooth module? This what i faced,any resolution? PoneomenusT 3 years ago.Previously I made a very simple frequency-modulated continuous-wave FMCW radar that was able to detect distance of a human sized object to m.

It worked, but as it was made with minimal budget there was a lot of room for improvement. One of the bigger problems was that voltage controlled oscillator VCO generating the high frequency output signal was driven directly from the digital-to-analog converter DAC of the microcontroller. VCO tuning voltage and output frequency relation is not linear and using a linear ramp as a tuning voltage generates slightly non-linear frequency sweep.

If the frequency sweep is not linear it generates non-constant mixing tone at the baseband. FMCW radars use Fourier transform of the baseband signal to find the distance to the target and when the received tone is not constant it spreads the power in the frequency domain and target resolving resolution decreases.

VCO's output frequency as a function of the tuning voltage. Ideally this would be linear. A linear sweep can be generated by pre-distorting the VCO tuning voltage so that result is a linear sweep. Other way is to use a phase locked loop PLL that uses a frequency divider to measure generated RF frequency and compares it to accurate low frequency reference oscillator.

A feedback loop then adjusts VCO tuning voltage so that divided frequency equals the reference oscillator frequency, this forces the RF signal frequency to be division amount times the reference oscillator frequency. Sweeping the divider value in small fractional steps can be used to generate a very linear sweep. Alternatively reference oscillator frequency can be swept while keeping the divider constant.

how to make a homemade doppler radar

Mixer output of the old radar when antennas are replaced with loads. Waveform is caused by the LO leaking to RF input port of the mixer. Receiver also had few problems. First being that baseband low frequency amplifier just didn't have enough gain to amplify low power echoes from far away limiting the maximum range. Other receiver problem was DC mixing product changing during the sweep and creating AC signal.

Receiver LNA had a gain of 13 dB and mixer after it had a conversion loss of 8. This only leaves 4.

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Since the receiver is a direct conversion receiver, LO oscillator leaking to RF input port of the mixer is going to cause a mixing product at DC. Power amplifier output power and mixer conversion gain vary with frequency causing the DC offset term to also vary. It creates an AC signal with frequency equal to sweep repetition frequency. This frequency is around 1 kHz and is amplified by the baseband amplifier.

Since RF gain is low, this leakage signal can have bigger amplitude than the received signal saturating the baseband amplifier. A better mixer with more isolation, PA with less gain variation, more gain at RF and high-pass filter after mixer can be used to minimize this effect. Last problem was with the microcontroller. It probably would have been possible to improve firmware but strict timing constraint for generating the VCO ramp signal would had made it hard.

Because of the various problems with the old design I decided to make a new radar that fixed the problems. The new radar design is very similar to the old one on system level, but with few improvements.

It functions using same principle: Transmitted linear sweep reflects from target and is received at the receiver. There it is multiplied with copy of transmitted sweep. Since electromagnetic radiation travels at speed of light, there is a time difference between received reflection and transmitted sweep. Multiplication in mixer generates a low frequency signal that has a frequency proportional to travel time of signal.

Fourier transforming the mixer output signal gives frequencies in the signal and it can be used to resolve more than one target at the same time. Biggest difference is addition of PLL that linearizes the transmitted sweep. PLL used is ADFit is designed especially for radars and it can be programmed to generate accurate sawtooth and triangular ramps.The box said that this toy could clock the speeds of not only miniature Hot Wheels cars, but also full-sized vehicles.

I figured the toy must have severe limitations, but decided to buy one for my daughter anyway. It turns out that she we loved it, and we found that it could accurately measure the speeds of toy cars, cars on the road, even joggers. To my amazement, the detector even measured the speeds of spinning objects like bicycle wheels. Operating the toy is simple: you aim the gun, squeeze the trigger, and then read the detected speed on the LCD in back. A switch selects either mph or kph readings, and another switch toggles the display units between scale for Hot Wheels and scale actual speeds.

Power comes from 4 AAA batteries housed in the handle. Inside, the Mattel gun uses Doppler radar, just like the expensive speed detection systems used by law enforcement. It transmits a continuous wave at I suspect that this keeps the microwave emissions low enough to guarantee child safety.

Limitations aside, I realized that this so-called toy offers some interesting prospects. The wheels in my mind began to churn, and I decided to purchase another unit for my own use. I disassembled the gun and decided to repackage it to appear more professional — looks really are everything.

I separated the detector component itself the waveguide antenna from the display and control panel, then connected the two with a length of instrumentation cable. This configuration lets you position the antenna close to traffic on a tripod, and operate it remotely from a safe distance.

how to make a homemade doppler radar

Anyone still using — Azon Deal Buster just google it? Is it possible to connect the gun to something like the Raspberry Pi with a camera kit so that a picture is taken at certain speed readings, say anything over 35mph? My main motivation is to keep my children from becoming paraplegics. Sure thing! I recently moved and I have cars flying by 15 — 35 mph consistently over the speed limit which is I would love to get something like this set up. I would like to set up a database and log the speed, time of incident, license-plate, etc.

None of this would work. At any rate. They also must be checked before and after each shift. If someone were to challenge a speeding ticket and knew how to properly address these issues to the officer. Thus, designing your own is fine. It still could raise awareness, and provide enough proof for police to set up some speed traps in the area you have issue with on occasion to try and curtail these speeders. You know those signs that blink your speed? Well they have Radar guns in them obviously.

The law is very strict on the tracking and methods used to ascertain moving violations pertaining to speed. That is dangerous and should be handled by the police.

Thanks for your opinion. I did get a kick out of your one-man point-counterpoint, though…. Besides the fact that I thought it would make a fun experiment if nothing else. Setup a VCR set to extra long play record time like 6 hours or so. You can get them at local thrift store.

Setup a video camera on a tripod aimed at speeding cars. Put this gun on another tripod in the field of view.