With recent advances in CMOS process technology, the concept of system-on-a-chip (SoC) has been realized by integrating more and more digital and analog building blocks in a single chip [2,9]. Additionally, these advances have brought several new types of processes faults (soft fault) and higher process variations to RF circuit resulting performances degradation. In order to compensate the RF circuit performance, a novel efficient self-calibration method for 865-870 MHz low noise amplifiers (LNAs), which constitute a RF mixed-signal circuit, is developed. This technique detects any deviation from the output match and from reverse isolation using built-in self test (BIST) methods, and then provides a corrective measure to recalibrate these LNA performances to the possible optimal value. This proposed self-calibration technique uses a switchable resistor which has been designed to investigate its ability to compensate for output match S22 and reverse isolation S12 without affecting other LNA performances. The use of this method saves space on chip and prevents adding switch resistor noise.In addition, the new calibration design shows the ability to calibrate S22 and S12 due to the catastrophic fault.