Design of 6 GHz Variable-Gain Low-Noise Amplifier Using Adaptive Bias Circuit for Radar Receiver Front End

This paper presents a variable-gain low-noise amplifier (VGLNA) based on an adaptive bias (ADB) circuit for the radar receiver front end. The ADB processes signal separated by coupler at LNA output port. First, rectifies coupled into positive DC voltage through rectifier, which is then inverted to control junction-gate field-effect transistor (JFET). voltage-controlled current of JFET flows voltage-divider network and finally produces biasing BJT base termination, decreases with increase in input RF power. proposed VGLNA operates automatically high gain low power power, providing wider dynamic range as compared constant-bias counterpart. For validation, prototype fabricated measured 6 GHz. As observed, generated changed from 858 mV 798 increases −50 dBm 0 dBm. result, represented P1dB point (IP1dB) has 6.5 dB, while still maintains 15.15 dB