Power Calibration Loop With High Accuracy of 10 dBm ±0.5 dB for a 77-GHz Radar Application

A TX power calibration loop with high accuracy for millimeter-Wave (mm-Wave) automotive radar application is presented. The loop consists of a calibration logic, a variable gain amplifier (VGA), a power amplifier, a power detector, an analog-to-digital convertor (ADC) and a temperature sensor fabricated in a 40-nm CMOS process. The digital power calibration loop is implemented to adjust the monitored detector output voltage to a predetermined target voltage according to a temperature by controlling the gain of the VGA. To achieve high power accuracy and stability against temperature variation, the proposed power detector is designed to realize flat or monotonic characteristics against temperatures by optimizing a second distortion. Measured calibrated output power shows 10 dBm ±0.5 dB over wide temperatures ranging from -20 °C to 125 °C.