Development of low-cost frequency-modulated continuous-wave radars at S and W band

Continuous-wave radars are capable of measuring distance and radial velocity. For measuring distance, frequency modulation is required. The most common type of modulation is a linear variation of frequency over time. Continuous-wave linear frequency modulated (CW-LFM) radars are used in multiple applications such as proximity sensors, non-intrusive inspection or imaging systems. This project has two different objectives: - Development of a low-cost CW-LFM radar for radar imaging. Radio frequency elements in a radar imaging system tend to be one of the most expensive parts of the whole system. The project looks for a low-cost alternative of conventional systems. - Development of a low-cost CW-LFM radar for educational use. An adaptable CW-LFM radar is desired while allowing flexible configuration and full characterization of each parameter of the radar. Also, there is the need to obtain the raw samples of the radar, for further processing in a personal computer. This document shows the development of two CW-LFM radars, one at W band and the other at S band. Both bands allocate at least one ISM reserved band, allowing the operation of said radars without license. The advantage of the W band is the availability of huge bandwidths. It is easier to obtain larger bandwidths when operating at higher frequencies. Given the fact that the resolution of a CW-LFM radar is defined by the absolute bandwidth, the use of mm-bands is a good option when looking for large bandwidths. Also, using high frequencies helps to improve the cross-range resolution on a imaging system. The main benefits of the S band are the reduced costs due to wide selection components and low manufacturing costs. The W band radar is based on a commercial MMIC (Monolithic Microwave Integrated Circuit), which provides all the high-frequency elements: oscillator, mixer and amplifiers among others. This project creates the needed baseband platform for said MMIC, providing the ability for frequency modulation and adapting the signal for the correct acquisition. It is focused on radar imaging. The S band radar originates as an educational project: a very low-cost radar capable of measuring distance and speed. The whole system is designed with commercial integrated circuits. The wide selection of components in the band due to WIFI band overlap, reduces the cost of the system. Also the selected frequency band allows to manufacture the boards without much complexity. In the basic design of this system, every functional block of the radar is isolated and connectorized. With this structure, full characterization of the radar can be achieved, allowing the users to compensate any malfunction of the system. The whole system is configured by a microcontroller, which also samples the signal that will be transmitted to a personal computer via USB. Also, the applications of each radar are studied. Specifically, the W band radar has been integrated in an already-existing passive imaging system