Temperature and Process Calibration of HBT-Based Square-Law Power Detectors for Millimeter-Wave Built-In Self-Test

HBT-based millimeter-wave square-law power detectors exhibit high power readout uncertainties, typically in the range of ±5dB, related to process and temperature variations. High uncertainty is unacceptable when the detector is used for built-in self-test purposes. To overcome this drawback, we propose a new calibration procedure based on an analysis of the process and temperature-dependent terms in the detector output voltage equation. Unlike previous approaches, the proposed procedure has minimal area overhead while dealing with both temperature and process variation. The calibration procedure is verified experimentally along with process corner and Monte Carlo simulations. We show that the proposed approach is able to entirely remove the limitation of the dynamic range (DR) for low inputs caused by mismatch. After calibration, the power prediction error in the DR is within ±1dB, an accuracy improvement of at least 4dB.