A novel simulation tool for PN junction varactors based on finite difference approximations

The estimation of the resistance of varactors used in integrated circuits for RF applications is a difficult task. This article presents a novel simulation tool for estimating the two main varactor parameters: resistance and capacitance. Once the capacitance and resistance are found, the Q factor can easily be obtained. The algorithm for estimating the varactor's parameters is based on the Finite Difference Approximation, and the programming language selected for its implementations is JAVA. The simulation accuracy has been checked by comparing the estimated resistance and capacitance valves obtained with this tool with those obtained by measurements of two PN junction varactors fabricated ad hoc. This comparison has shown excellent agreement. For example, the average error between the real and simulated capacitance is 14 percent, whereas the error for the resistance is only three percent.