Electrooptic Inspection of Vector Leakage in Radiofrequency Multichip Modules

This paper demonstrates a new approach for the measurement of vector electromagnetic leakage within tightly integrated electronic subsystems. Specifically, the effect of shielding and encapsulation techniques commonly used in radiofrequency (RF) multichip modules is investigated using an electrooptic (EO) near-field measurement system. The test vehicle used for this study is a single-chip 50-W microwave power amplifier integrated into a multilayer low-temperature cofired ceramic module. The measured near-field data show power intensity at 2.5 GHz with up to 0.2-mm resolution for each of the three x-, y-, and z-directed electric field vectors. The resulting images illustrate 1) the polarization-dependent shortcomings of the ubiquitous “via-fence” shielding technique and 2) the formation of surface waves in microstrip substrates due to impedance mismatch. These results are evidence of the applicability of the EO technique to the diagnosis of electromagnetic compatibility issues within compact RF multichip modules.