Millimeter Wave Testing: the Struggle between Feasibility and Mass Production Support
Through the last 20 years, cellular phone RFICs below 6GHz band have achieved a tremendous progress on reducing mass production test cost, making it a small fraction of the total product cost. As frequency keeps increasing to the mmWave range for Wireless communication applications such 5G, backhaul, automotive and communication radars, the struggle to keep the mass production test cost acceptable is far from being realistic. Today’s cost is almost split between the price for Silicon, packaging and production testing.
Moving higher in frequency to the mmWave range imposes new dilemma to the test community including bench equipment vendors and ATE suppliers. The higher BW is the main advantage for moving to such frequency range to achieve higher data rate but this is requires a higher instantaneous analog bandwidth and complex modulation schemes to be measured during test.
The new multi-RF chains design 16, 32, 64 antenna elements (or more) poses new challenges. Those challenges are enormous, ranging from electrical specifications to mechanical requirements especially when using waveguide components. Instrumentation proximity to the DUT is almost a must to overcome the RF power losses in cables and interconnects. Higher integration of the RFIC by including ADCs/DACs and high speed SERDES to the RF front-end and the desire to achieve higher transmitter power increase the DC power consumption which comes with it's own challenges during production testing and require sophisticated cooling mechanisms. With highly integrated mmWave SOCs, design for test plays an important aspect to reduce production test cost.
Testing modules with integrated antenna in a production environment requires a complete new thinking, where only wireless communication between the tester and the DUT is possible. A stable calibration is a key to achieve an accurate and meaningful measurement especially for mmWave, the need for moving from a simple scalar de-embedding to a complex de-embedding (phase and amplitude) is highly desirable. New electrical spec such as accurate phase measurement between antenna ports is a new concept compared to traditional RF and mmWave transceivers.
In this Presentation, we will present the state of the art of mmWave test practices from design for test to automated test equipment (ATE) and test coverage. We will highlight the technical roadblocks preventing us form having a cost-effective mmWave high volume manufacturing.