This element is used to provide filtering in the RF path. This system symbol is available on the System toolbar.

Name 
Model 
LPF_BUTTER 
Alternate Models 
LPF_BUTTER_C 
Schematic Symbol 
LPF 
Alternate Schematic Symbols 
None 
NOTE: The alternate model "..._C" is a circuit model created from a synthesis process with real components. The circuit is not visible to the user. Simulation time for the circuit models is generally longer since there are more components.
Parameter 
Description 
Units 
Default Value 
IL 
Insertion Loss 
dB 
0.01 
N 
Filter Order 
none 
3 
Fpass 
Passband Edge Frequency 
MHz 
200 
Apass 
Attenuation at passband 
dB 
3.01 
Amax 
Max Attenuation in stopband 
dB 
100 
Z1 
Reference Impedance Port 1 
Ohm 
50 
Z2 
Reference Impedance Port 2 
Ohm 
50 
TYPE 
Input Stopband Impedance (0 = Short, 1 = Open) 
none 
1 
The Butterworth filter characteristic is a maximally flat response in the passband generated by poles only. This results in no ripple in the passband, but a cutoff which is less sharp than some other filters. The insertion loss only affects the forward (S_{21}) and backward (S_{12}) transmission, but not the reflection coefficients (S_{11},S_{22}). The input impedance in the stopband only affects the phase of the reflection coefficients. For additional details on filter types see the FILTER Synthesis Manual.
Note: The insertion loss and passband attenuation must be greater or equal to zero. The filter order must be an integer greater or equal to 1. The frequency of the passband edge must be positive.
DC Block  DC will only be blocked by the amount of attenuation at 0 Hz.
Maximum Attenuation in stopband  The maximum attenuation in the stopband is modelled with a resistor between the input and output port of the filter. An equation is used to determine the value of the resistor from the given attenuation. This parallel resistor will only be effective when the filter stopband impedance TYPE is set to open. For even filter orders the impedance looking into one port is high and the other low so the maximum attenuation in the stopband has no effect.