An ATE system for testing 2.4-GHz RF digital communication devices with QAM signal interfaces

Recently, there is an increasing need for methods of functionally testing RF devices to provide lower cost alternatives to testing RF communication systems. This paper proposes an ATE system for testing RF devices with QAM signal interfaces. The system utilizes a concept of direct modulation/demodulation with multi-level drivers and multi-level comparators. The multi-level drivers can directly generate the 4-QAM and 16-QAM signals. The multi-level comparators can directly compare the baseband data with its expected data. The multi-level comparators are based on the dynamic threshold concept which changes the threshold voltage levels dynamically in response to the expected values of a signal under test. This architecture is suitable for a test system which is required to test many kinds of signals flexibly. Experimental results are discussed with a prototype circuit that demonstrates the proposed concept applied to testing of a 2.4 GHz 16-QAM signal.