Experimental monitoring of the gain in RF Power Amplifiers using Temperature Measurements
Document typeMaster thesis
Rights accessOpen Access
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The Aging effect is intrinsic to transistors in integrated circuits and occurs sooner with newer, smaller manufacturing node technologies. With prolonged usage within the nominal power and biasing operating point, some charges get trapped in the transistor channel and carrier mobility is reduced, the threshold voltage VT is increased and operating point changes, decreasing the drain current ID and gain. This results inworsened DC and RF characteristics of the transistor in a power amplifier PA, and so are their precision or communication power in analog or RF applications, respectively. The Aging can be calibrated and corrected by modifying the biasing, restoring the original gain at the cost of increased power consumption. To this date, this recalibration is performed with integrated power sensors that monitor the gain and control it by modifying the biasing. This method, however, uses valuable layout space and is a direct measurement which modifies the real circuit topology, having an impact on its characteristics and behavior. Prior research in the ETSETB Electronics Engineering department proposed the usage of temperature measurements, indirect by nature so they do not modify the circuit topology, to control the gain by also modifying the biasing as the Aging progresses. The studies proposed heterodyne (two RF tones) over homodyne (one RF tone) temperature measurements as being less prone to noise. An IC to test this principles called PAAGEANT was designed, simulated and manufactured, and 20 ICs are available at the ETSETB Electronics laboratory. This thesis experimentally characterizes in DC and RF one PA in the PAAGEANT IC to extract its gain and characterizes its temperature sensor TS and thermal coupling between the PA and TS. These characteristics are used to then propose experimental signatures relating the gain and temperature measurements. Several methods of temperature measurement of the PA are tested and studied with 11 ICs to ensure repeatability. In further studies, the signatures will be measured during and after the aging process, so a control system modifying the biasing can correct the resulting temperature signature of each IC after Aging to the signature measured before Aging, and so will the gain. Some temperature sensor TS characteristics vary among the measured ICs, and results show that the signatures must be calibrated for individual manufactured ICs. The homodyne and heterodyne signatures proposed in this Master's Thesis show promise in being used in control systems that will be correcting the gain-temperature signatures.