MTFC (Microstrip Thin Film Capacitor) SmartComponent

Symbol

Parameters

Name	Description	Unit	Default
Subst	Microstrip substrate name	None	MSub1
F	Center frequency	GHz	1
C	Capacitance	pF	1
W	Conductor width; set to 0 if Zo specified	mil	0
Zo	Characteristic impedance of line for computing W; set to 0 if W specified	Ohm	50
CPUA	Capacitance per unit area	pf/mm^2	300
T	Thickness of capacitor dielectric	mil	0.2
RsT	Sheet resistance of top metal plate	Ohm	0
RsB	Sheet resistance of bottom metal plate	Ohm	0
TT	Thickness of top metal plate	mil	0
TB	Thickness of bottom metal plate	mil	0
COB	Bottom conductor overlap	mil	0
COT	Top conductor overlap	mil	0
DO	Dielectric overlap	mil	0
Delta	Length added to conductor for tuning capacitance	mil	0

Notes

1. MTFC designs a microstrip thin film capacitor. The underlying design uses the MTFC component contained in the Tlines-Microstrip palette.
2. The design is accomplished by determining the length required to achieve the desired capacitance using the capacitance per unit area (CPUA) in conjunction with the specified width (W).
3. Since this capacitor is often fed with a microstrip line, either the physical width or the characteristic impedance of a microstrip line on the substrate can be specified. However, only one of the parameters should be non-zero.
4. The parameters from RsT through DO inclusive are not used in the design process but are passed on to the underlying MTFC component and therefore included in any simulations or optimizations.
5. The tuning parameter Delta represents incremental length required to achieve the desired capacitance. It is typically relatively small, as the initial design tends to be accurate.
6. The Optimization Assistant tunes the conductor length to achieve the desired capacitance.
7. A SmartComponent subnetwork is empty until the Design Assistant is used to generate the design. Refer to Design Assistant.

Example

A MTFC component was used to design a 100 pF capacitor at a center frequency of 2 GHz. The conductor width corresponds to that of a 50 Ohm microstrip line fabricated on MSub1. Optimization yielded a value of Delta = -2.411.