Investigation of Semi-Rigid Coaxial Test Probes as RF Injection Devices for Immunity Tests at PCB Level

This work investigates the performance of RF immunity procedures exploiting semi-rigid coaxial test probes as coupling devices to inject continuous wave (CW) RF power into the outlets of Integrated Circuits (ICs). Two solutions are presented, both offering the advantage with respect to the traditional direct power injection method, to run the test without removing the IC from its actual PCB. The first procedure resorts to near-field coupling to inject the noise into an interconnecting trace. The second procedure requires metallic contact between the probe tip and the injection point (e.g., a via or an IC pin). Specific figures of merit, such as coupling and power efficiency, test repeatability and intrusiveness, sensitivity to setup parameters and lateral spatial resolution, are introduced and used to ascertain the effectiveness of the proposed procedures. To this end, both numerical simulations and measurements were carried out on several PCBs. Feasibility of the proposed immunity procedures is eventually proven by an application example, involving a thermal sensor as device under test.