Radio Frequency Integrated Circuit Design - Webs

114 Radio Frequency Integrated Circuit Design
The other thing that must be considered is the substrate. This is an issue
for which we really do need a simulator. However, as mentioned above, the
capacitance and resistance will be a function of the area. This also means that
once several structures in a given technology have been measured, it may be
possible to predict these values for future structures. For this example, assume
that reasonable values for the fitting parameters have been determined. Thus,
R sub and C sub could be something like 870� and 115 fF. The complete model
with values is shown in Figure 5.15.
Example 5.6 Determining Inductance, Q, and Self-Resonant Frequency
Take the model just created for the inductor in the previous example and
compute the equivalent inductance and Q versus frequency. Also, find the selfresonance
frequency. Assume that the side of the inductor with the underpass
is grounded.
Solution
The equivalent circuit in this case is as shown in Figure 5.16.
This is just an elementary impedance network, so we will skip the details
of the analysis and give the results. The inductance is computed by taking the
Figure 5.15 Inductor � model with numbers.
Figure 5.16 Inductor model with one side grounded.