Sensors are increasingly being used today for many new areas of technology (aeronautics, space, telecommunication.). They are mandatory for systems that want to regulate themselves (control systems), and very useful for just obtaining information on the surrounding environment (temperature, pressure, surface integrity). In the world of sensors, we are specifically interested here in wireless sensors, passive and chipless, operating in the millimeter band (Ka). These have constraints of being remotely interrogable (wireless) and having no power source (no battery) or active electronic component (no transistors). This passivity and the absence of silicium components make those sensors very robust (long life) for reduced manufacturing costs. Thus, they can be placed in environments where access is difficult, or where physical conditions are harsh (integrated in buildings, in the middle of a nuclear power plant, inside a satellite, etc.). We investigate here how mm-wave sensors can be interrogated using a Frequency Modulated Continuous Wave (FMCW) RADAR working in the Ka Band. This thesis presents how we can perform interrogation of mm-wave passive sensors using its backscattered EM. RADAR interrogation quantifies the backscattered signal of the sensor according to the distance. We aim to get the sensor's information by this echo. Nevertheless, this brings other constraints : the environment around our sensor can disturb our interrogations in closed environments (presence of electromagnetic clutter). This is why, here, we suggest a depolarization technique to get rid of this clutter and therefore improve the quality of the interrogation. This depolarization technique simply proposes to produce the signal backscattered by the sensor in an orthogonal polarization : as the beat spectrum observed in this orthogonal polarization (cross-polarization) is less subject to environmental perturbations, we make the sensor signal independent of it and can obtain more accurate information. To go further, we examine the feasibility to interrogate sensors behind a metallic wall by using passive repeaters. To make the design of future sensing devices, we produced simulation and mathematic development of the interrogation full chain system. With this interrogation technique, we demonstrate that we are able to design, fabricate and interrogate passive sensors working in the Ka-Band. For this, we used the 3D printing metal technologies for fabricating pressure sensor mixing a Wave-Guide with microfluidic channels that can be used for pressure sensing. Knowing how to make those sensors will make a huge difference on how we aim to design our passive sensors. Through this manuscript, we will have defined the general design rules for our passive depolarizing sensors interrogable by RADAR. We present different estimators (echo at the sensor position, sensor position, integral, etc.) in order to exploit the diversity of scattering parameter variations that can be proposed technologically for sensing. We thus open the doors to new design possibilities to realize sensor functions, through the modification of the filter templates used and the use of the right estimators. The use of additive technology, especially metal 3D printing, opens up opportunities for the integrated realization of passive sensors, because until now sensors used were connected to standard antennas for interrogation. We aim to finally have an all-in-one structure that can be used as a sensor object with antennas and transducers integrated in it. This kind of object could be a huge advance for RADAR sensing as they are meant to be small because they work on the mm-band. Therefore, they will be suitable for our harsh environments/indoor/thru wall applications, where it will be complicated to place a bulky sensor.