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How to create an fmcw radar?

Self-made Radar

First of all: this section is not an instructions manual suitable for reproduction. It is a concept for the construction of a radar set, which should encourage to think about it and for own solutions. Nevertheless, some parts are also interesting for a replica, since they can also be used for other projects.

I often receive inquiries from young people who have decided to build their radar. Probably in the context of a planned Bachelor thesis, but I'm not sure, because here the supervisors would have to act as a brake because this task is rarely financially affordable for a student. Even the simplest to make configuration will require a financial investment of around 500 Euros. With a phased-array antenna, one would quickly be in the range of several thousand Euros.

I would now like to present a project on how to set up your radar, preferably with components that are freely available on the market. I will only describe the hardware here. Those who want to rebuild this project should be able to do the programming themselves (or know someone who can). When evaluating prices for radar sets it should be kept in mind that the number of units produced is usually small. That is to say that all engineering costs incurred are distributed among this small number of radar sets. This applies in particular to the software to be created. The software accounts for more than half of the final price of radar sets. The material value, on the other hand, is rather low.

The frequency range used is the WLAN band from 2.4 to 2.5 GHz, which can be used without special approvals. There are various modules available that require little or no modification. Components available on the market should be used so that soldering work is kept to a minimum. The proposed components are also available for the frequency range 5.725 - 5.875 GHz. This affects the construction of the antenna: At 2.4 GHz is required a yagi antenna, at 5.8 GHz a horn radiator with a coaxial cable feed.

Of course, compromises will have to be made everywhere, because, for example, building an antenna yourself is much cheaper than buying finished products. Separate transmitting and receiving antennas are still cheaper than a ferrite circulator, even if the final product will not look so elegant. However: A do-it-yourself antenna is usually cheaper but takes much more time.