A Current-Mirror-Based GaAs-HBT RF Power Detector for Wireless Applications

This paper describes circuit design and measurement results of a newly developed GaAs-HBT RF power detector for use in wireless applications. The detector features logarithm-like, frequency-independent characteristics. The detector can be also driven with small input power levels, enabling base-terminal monitor which can utilize directivity of a power stage. Since a unique current-mirror-based topology is successfully employed for realizing these features, the detector is easy to implement on a GaAs HBT power amplifier. Measurement results of a prototype detector fabricated with a single-stage amplifier on the same die are as follows. The detector can deliver a detection voltage of 0.4-2.5 V and its slope of less than 0.17 V/dB over a 2-22-dBm output power range at 3.5 GHz while drawing a current of less than 1.8 mA from a 2.85-V supply. The detector is also capable of suppressing voltage dispersion within 50 mV over a 3.1-3.9-GHz wide frequency range operation, and this dispersion is less than one-seventh of that of a conventional collector-terminal-monitor type diode detector.