I'm new to the world of RF communication and was interested in building a miniature radar unit powered running off an Arduino uno/nano. The radar is only a proof of concept on a small scale so won't run into issues with HAM licensing and the like.
I'm not 100% certain whether an Arduino can natively create a suitable antenna signal pulse, send it with an antenna like a monopole or dipole antenna and then await a response signal, and then based on delay or phase shift determine a target's range or velocity. As some antenna types are considered "dead shorts" in DC and the arduino is natively a DC device, just want some advice before i accidentally blow up my board.
Using Arduinos you can measure times in milliseconds (slow) or even microseconds (faster).
Because radio signals propagate at a speed of around 3x10^8 m/s, in one microsecond the radio signal has gone 300m, which equates to a round trip to a target 150m away.
This means that using microseconds to do the timing you can only measure distances in units of 150m.
Even if you were really clever and could measure the time of the reflection in machine cycles instead of microseconds you can't do much better.
For a typical Arduino with a 16MHz clock, then you can only measure time in units of 62.5ns, during which time the signal has travelled 18.75m.
All this pre-supposes that you can generate pulses of RF energy and receive the reflections, and convert them to a digital signal correctly.
There are experienced Arduino users who also have a lot of RF experience and knowledge. You might then expect that if an RF RADAR with an Arduino was possible, then by now someone would have achieved it. Did you find any examples with an Internet search ?
In most places in the World you will have to follow appropriate regulations, there is no general excemption for 'proof of concept' use.
Thanks for the replies, really appreciate the time. I've got a decent amount of experience with arduinos having done some DIY projects for around the house, and also have university experience with RF when I studied physics. But my knowledge based on the hardware limitations of arduino are pretty basic.
Considering the speed of the clock isn't really fast enough to do anything on a small scale, and the power restrictions of the arduino limit its range, it seems that an arduino is not the right method for attempting this. Would it be possible to use arduino to potentially control external hardware to make this possible or would it be more beneficial to just run the external hardware by itself.
I was just looking for a cost effective way of testing an at home radar.
Considering that RF signals at least in australia are band restricted and power restrictions apply, you can get around it by not emitting signals into an area where they affect others and are detected for a desk test it is not really an issue
This looks promising, I might look into using something similar. Although wouldn't this potentially also have the same problem where it can detect velocity through Doppler shift but wouldn't be able to determine range due to the sampling time.
I might look into the sonar or acoustic method due to the lower speed of sound as opposed to that of light, but might need to try something a little bit different to a standard ultrasonic method
Yes, you are right. I wanted to use it for a crude form of distance measuring to detect ground proximity in a model aircraft. But that's just detecting the difference between measuring nothing and measuring some dopplershift when the surface is approaching.
For practical distance measuring I only know the LIDAR sensors.
Perhaps more information can help your project.
For radar you need to apply all possible power to hit the target. Any antenna short of a dish type reflector will waste almost all your precious RF power. Also to create a reflected signal you need to send a huge amount of RF power so you can get some power in the reflection! You can research the power loss vs. distance.
You will also need to send the RF power in a VERY short burst so your receiver has time to prepare for the returning echo.
You write of measuring phase shift to compute velocity. Try frequency shift. You also need to be able to process the echo signal to get the frequency shift, which may be only a few Hz.
Relating to an antenna as a DC device. Remember, you are ONLY dealing with RF which is an AC signal. Many antennas are a DC short circuit, which will make no difference to the RF signal. Many of my ham radio antennas are DC shorted.
The antennas on most, of not all modules for the Arduino have capacitors in series with the antennas so DC cannot be shorted through the antenna. Check yours with your Ohmmeter.
The power loss of the transmitted signal falls off as an inverse square law.
A small proportion of the signal is reflected from a target - this signal then also falls off as an inverse square law.
The two combine to give a received power that is inversely proportional to the 4th power of the target distance.
That is why you need very high powers to 'see' targets that are a long way off.
