11 Décembre – Thesis defense - Hugo Vallée

10 h Amphi Jean-Paul - Laboratory IMS / Building A31 (Talence campus)

Design of millimeter-wave receivers for embedded automotive radars.

DSince few years, automotive industry implements more and more advanced driven assistance systems to improve safety and autonomy of vehicles. To achieve high autonomy level, each vehicle may include more and more sensors. The embedded 80GHz radar presents many advantages for car manufacturers: great immunity to outdoor conditions, real-time measurement of distance and velocity… To face such requirements, semiconductor industry has to simultaneously reduce cost and improve radar performances. It requires first to use advanced CMOS technologies (40nm, 28nm and smaller nodes). However, the main figures of merit should be improved such as the output power of the transmitter, the phase noise of the local oscillator and the noise figure of the receiver. The objective of this thesis is to propose new architectures and topologies able to improve the radar receiver performances.
In an automotive context, the radar receiver face two main issues. Mounted behind the bumper, the radar module is impacted by the reflection of the transmitted signal. It may cause non linearities in the demodulation chain thus creating false targets. For this reason the level of linearity is high, especially regarding the compression point and the limited front end (FE) gain. The improvement of the RADAR sensitivity requires both to maximize the FE gain and to minimize the noise figure (NF) of the receiver front-end. To face such contradictory specifications about the FE gain, this thesis works on more advanced design techniques and topologies.
In this thesis, a specific focus is proposed on two design techniques. First, the circuits are designed to improve their efficiency (gm/ID) by operating in the moderate inversion region which contributes to reduce the power consumption. Secondly, the common-gate based noise cancelling technique is explored at 80GHz. This topology achieves simultaneously a wideband behavior and a low noise figure. It leads to develop a topology called “complementary capacitor cross-coupled” which achieves high RF performance at a reduced power consumption with respect to the operating frequency.
Besides this thesis studies various mixing approach to determine the best suited for radar applications. First, considering its interesting performance trade-off in BICMOS technology implementations, active mixers are explored. Whereas the level of 1/f can allows for short range operations, it is too large for long range RADAR. To address this issue, passive mixers are then studied. They achieve better noise performances but severely impact the linearity performances. To overcome this drawback, an 80GHz current mode mixer featuring noise and linearity improvement is developed.

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