On-Wafer Production Testing Enables Fast Non-50ohm Impedance and Power Sweeps
When it comes to the production testing of RF transistor wafers, time is money. Only seconds are spent on each die, and that short time is used for basic parametric analysis such as IV curves and S-Parameters. Spending a few more seconds on each die can yield additional RF parameters such as output power from which efficiency can be calculated, but this is always performed at 50ohm or some fixed impedance. Even though RF transistors might have load impedances of a few ohms or less, non-50ohm production testing with varying impedances has never been implemented due to the slow testing times associated with traditional mechanical impedance tuners. Open-loop active load pull improves test times by eliminating mechanical tuners, but can still only achieve a few impedance points per second.