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mmWave Test Challenges

Many aspects of the test system require additional scrutiny when operating at mmWave frequencies such as the obvious RF instrumentation, cables and interconnects, the load board design and system level calibration.<Read More> Vector Network Analyzer (VNA) instrumentation is the heart of the RF measurement subsystem providing both phase and amplitude information; the ability to steer the RF energy is dependent on adjusting the phase and measuring the results. Scalar analyzers only return amplitude data and are, therefore, not a viable solution for these applications where the phase component of the result is critical.

Seemingly innocuous properties such as cable routing and bend radius are of little concern when fabricating low band (<6 GHz) test systems, but as we move into the high band arena (>30 GHz+) small variations or improperly rated components can result in significant signal variation and degradation. mmWave cable manufacturers, for example, specify minimum cable bend radius and connector torque requirements to achieve maximum transfer of RF energy. Therefore, manufacturing must ensure consistent fabrication techniques and processes, as well as incorporate the appropriate tooling for assembly.

mmWave load board design and blind mate interface performance are similarly critical to achieving desired system level test results. The device under test (DUT) load board must be designed to provide uniform trace impedances if the required signal performance is to be achieved. This involves selecting the appropriate laminate and stitching the signal and ground planes for consistent results across all channels. Blind mate interface connections are also a concern in production environments, especially at higher frequencies, where electrical performance must remain consistent across multiple engagement/disengagement cycles and across test systems.

We'll explore the RF measurement subsystem in our next post.
<Read More>mmWave Test Challenges White Paper