Output match and reserve isolation compensation of an inductively degenerated CMOS LNA using switchable resistor

As the complexity and operating frequency of integrated transceivers continue to increase accompanied with higher process variation, their calibration and characterization has become a considerable challenge to test engineers. In order to provide an efficient calibration method for 865-870 MHz low noise amplifier (LNA), which constitutes a mixed-signal circuit, a novel method is developed. This technique uses a switchable resistor which has been designed to investigate its ability to compensate for output match S22 and reserve isolation S12 without affecting other LNA performance. The use of the switchable resistor saves space on chip and prevents adding switch resistor noise. In addition, it allows the improvement of S12 by 5db after calibration.