Novel methodology for choosing detectors for the Automatic Level Control of high power amplifiers

The automatic level control (ALC) is a loop used to control the output power of high-power amplifiers. The main goal of this loop is to maintain the output as constant as possible in any condition of the input signal. To achieve this regulation, the majority of systems use feedback loops which have detectors to measure the output signal and compensate when the signal is outside an acceptable range. The performance of such ALCs depends on the measurements of the output power. The ALC will not compensate to the right value if the measurements are not correct. This article is to discuss several detectors solution for such application, and enable to define the most appropriate one to achieve the best measurement. The more common detectors to be used are peak, average, root mean square (RMS) or log ones. Each of these detectors have advantages and drawbacks. The conclusion of this study shows that whatever the crest factor of the signal only one detector (peak detector) will provide the same measurement. And, it is mandatory for this application to make sure that the output level will never exceed the maximum rating of the amplifier system.