021/100 Distributed Inductance and Capacitance

100 ADS Design Examples Based on the Textbook: RF and Microwave Circuit Design
November 2019
Michael Benker

Example 2.11-2D: Convert the lumped element capacitors and inductors to distributed elements.

This is the schematic that needs to be changed into distributed element microstrip lines:


The following formulas are needed to calculate the inductive and capacitive line lengths to simulate this schematic using microstrip lines.

Inductive line length: (frequency)*(wavelength)*(Inductance)/(impedance of line)

Capacitive line length: (frequency)*(wavelength)*(Capacitance)*(impedance of line)

In order to know what at which frequency the inductance or capacitance are calculated, let’s run the simulation of the above circuit:


This circuit is centered at 10 GHz, since the circuit behaves as a terminated open-circuited transmission line with an open-parallel resonance at 180 degrees, or twice the length of a quarter wave line.

The above circuit is then modeled as follows: