004/100 Example 1.3-1B Parasitic Elements of a Physical Resistor vs. Frequency

100 ADS Design Examples Based on the Textbook: RF and Microwave Circuit Design
Michael Benker
Example 1.3-1B: Plot the impedance of a 5 Ω leaded resistor in ADS over a frequency range of 0 to 2 GHz.


This indicates a resonance at 500 MHz. This is due to the parasitic iductance and capacitance that exists on a real resistor. The resistor behaves as a combination of series parasitic inductance and resistance, in parallel with a parasitic capacitance.

The impedance of an inductor is reduced as the frequency increases, while the impedance of a capacitor increases as the frequency increases. The intersection frequency of these two patters meet is the resonant frequency.

The resonance frequency can be found from equating XL and XC. The formula is:

Resonant frequency fR = 1/(2*pi*sqrt(LC))