Testing of RF mixers with adaptive filters

This work describes a technique for testing RF mixers with digital adaptive filters. RF circuits are widely used on data transmission applications, such as wireless communication, radio and portable phone systems. However, traditional analog testing covers mainly linear circuits, being not suitable to non-linear pieces of hardware like analog mixers. Herein, an adaptive non-linear filter is trained so that it can mimic the behavior of a RF mixer. Then, a test stimulus is simultaneously applied to the filter and the mixer and the outputs of both circuits are compared to check whether the circuit under test is faulty or fault free. A prototype of a mixer was built in order to allow fault injection in the circuit under test. Thus, the detection capability of the proposed technique could be checked in a real life circuit. The preliminary results point to a very promising test technique. The test is very precise, low cost and allows a complete fault coverage with a very small testing time.