Detecting Low-Frequency Critical Resonances in Power Amplifiers Using the Periodicity of Floquet Exponents
Different techniques have been presented for the measurement of critical resonances of power amplifiers in large-signal operation. However, low-frequency resonances are hardly observable at the output port of an amplifier that is tuned in a particular RF bandwidth with strict filtering out of band. In this work, we make use of the periodicity of Floquet exponents to detect and characterize the low-frequency resonances through measurements performed at the amplifier RF bandwidth. Techniques based on noise injection and output admittance measurements are applied and compared. Measurements on a DUT with strong decoupling of the low-frequency dynamics from the RF output port are carried out to demonstrate the feasibility of the procedure.