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

Abstract

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. INDEX TERMS Direct power injection, Microstrip line, Near-field probe, Radiated Immunity, Radio Frequency.

Test Design Methodology for Time-Domain Immunity Investigations Using Electric Near-Field Probes

“…Theoretically, the effect of perturbation exerted by the presence of the probe on the transmission characteristics of the trace under test should be taken into account. However, previous investigations [9] carried out by measurement and simulation on injection setups involving electric-field probes proved that, as long as the trace under test is covered by the solder mask (non-contact test in [9]), the probe exerts a negligible effect on signal propagation on the trace under test (i.e., the test is not intrusive). Hence, this effect can be neglected.…”

“…To exemplify the procedure of identification of the parameters of the behavioral model, an electric near-field probe, realized by a semi-rigid cable RG405 11.75 mm long and terminated in a 1 mm tip (hereinafter referred to as "probe RG405") is considered. The definition of probe performance parameters for immunity tests and their experimental investigation for probe RG405 can be found in [9].…”

“…In 2014, the standard IEC TS 62132-9 was published [6], which includes an immunity procedure at IC level carried out through near-field scanning. The feasibility of using both electric and magnetic near-field probes for immunity verification at PCB level was investigated in [7] and [8], [9], respectively. A comparison of performance of different electric near-field (E-field) probes for immunity investigations is provided in [10].…”

Analysis of Near-Field Probing Techniques for Immunity Tests

“…Compared with traditional radiated susceptibility tests or direct radiofrequency power injection method [8], nearfield tests not only are available for module-and PCBlevel testing but can also provide detailed information on weak components and/or noise propagation paths [9]- [12]. Indeed, near-field probes can be used to detect EMsensitive areas at IC [6], [13] and PCB [14], [15] levels. Furthermore, by properly placing probes on IC pins/nets, one can evaluate the EM-immunity performance of specific electronic components [15], [16].…”

“…Indeed, near-field probes can be used to detect EMsensitive areas at IC [6], [13] and PCB [14], [15] levels. Furthermore, by properly placing probes on IC pins/nets, one can evaluate the EM-immunity performance of specific electronic components [15], [16]. Therefore, it is of great importance to investigate the performance of different near-field probes and the corresponding test setups to ascertain their suitability for immunity analysis.…”