True non-intrusive sensors for RF built-in test

In this summary paper, we discuss two types of sensors that provide a built-in test solution for RF circuits. The key characteristic of the sensors is that they are non-intrusive, in the sense that they are not electrically connected to the RF circuit under test. This has the important advantage that the design of the RF circuit becomes totally independent from the design of the sensors. In other words, the RF circuit design methodology and performance trade-offs are totally transparent to the insertion of the built-in test strategy. In particular, we propose variation-aware sensors to implement an implicit functional test and a temperature sensor to implement a defect-oriented test. The proposed sensors provide DC or low-frequency measurements, thus they have the potential to reduce drastically the test cost. We discuss the principle of operation of the sensors, we provide design guidelines, and we demonstrate the concept on a set of fabricated chips. To the best of our knowledge, this is the first proof-of-concept of RF test based on non-intrusive sensors.