The circuit designer now has two ways to specify a single layer capacitor. 
The first way is by 1MHz cap and equivalent series inductance.  This  is
the circuit theory point of view.  The second way is by characteristic
impendence and electrical length.  This is the transmission line theory 
point of view.  It is the circuit designer's responsibility  to decide the 
more effective way for a particular application. Guidelines for capacitor 
choice are presented below, using some examples from CAPCAD.

For the purpose of these exercises, low frequency shall be defined as 
fmax < fp/2 where fmax is the maximum operating frequency, and fp is 
the first parallel resonance of the capacitor.

Example one: Low frequency turning capacitor

D25CG2ROC5PX(1=.025,W=.025,t=.0045,K=65,df=.007,R=.03) has its first 
parallel resonance at '32.6 GHz.  At any frequency below 16 GHz the 
physical capacitor may be represented by an ideal 2.0 pF capacitor with a 
series 0.012 nH inductor. Losses may be approximated by choosing a function
for Q, such as:

Q(f)=120x(f(GHz))-.176                  1 Ghz < f < 10 Ghz

or by defining series and parallel resistors, such as:

Rser=.003 x (f/1 GHz).5
                                          1 GHz < f,10 Ghz
Rpar= 120/(2 fC)

The equivalent series inductance of the manufactured device will vary by +- .002 nH.

Once the secondary parameters of series inductance and loss have been specified, 
a capacitance value can be chosen for the application.  To ensure the circuit will 
work as designed, it is a good idea to write CAPCAD'S parameters to a file and use 
them in the final circuit simulation.

When the modeled equivalent series inductance of a capacitor is low enough that it 
doesn't appreciably affect the device's reactance, the circuit theory point of view 
is adequate.  Specify the capacitor by its case size and capacitance value (see page 9).