Output Power and Gain Monitoring in RF CMOS Class A Power Amplifiers by Thermal Imaging

The viability of using off-chip single-shot imaging techniques for local thermal testing in integrated radio frequency (RF) power amplifiers (PAs) is analyzed. With this approach, the frequency response of the output power and power gain of a Class A RF PA is measured, also deriving information about the intrinsic operation of its transistors. To carry out this paper, the PA is heterodynally driven, and its electrical behavior is down converted into a lower frequency thermal field acquirable with an InfraRed lock-in thermography (IR-LIT) system. After discussing the theory, the feasibility of the proposed approach is demonstrated and assessed with thermal sensors monolithically integrated in the PA. As crucial advantages to RF-testing, this local approach is noninvasive and demands less complex instrumentation than the mainstream commercially available solutions.