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Ansoft Designer / Ansys Designer 在线帮助文档：

System Simulator >
System Component Models >
Filters >
   Elliptic Low Pass Filter (ELLPF_KP, ELLPF_FS, ELLPF_N)       

Elliptic Low Pass Filter (ELLPF_KP, ELLPF_FS, ELLPF_N)

Properties	Description	Units	Default	Range
AMAX	Maximum ripple in the passband	dB	Required	>0
AMIN	Minimum ripple in the stopband	dB	Required	>0
FC	Cutoff frequency	Hz	Required	>0
FS	Stopband edge, ELLPF_FS only	Hz	Required for ELLPF_FS	>FC
KP	Steepness of descent (Sharpness), ELLPF_KP only		Required for ELLPF_KP	[0,1)
N	Order of filter, ELLPF_N only		Required for ELLPF_N	[2,15]
R1	Reference resistance at node 1	Ohm	50.	³0
R2	Reference resistance at node 2	Ohm	50	³0
IL	Insertion loss in dB		0	³0

Notes

1. The model ELLPF has been separated into three components: ELLPF_KP, ELLPF_N, and ELLPF_FS. The parameters KP, N and FS may not be used concurrently, and are required for the corresponding components.

2. The elliptic filter is equiripple in the pass band and the stop band (it has equal loss maxima in the pass band and equal loss minima in the stop band). The elliptic filter is used when a sharp transition region is desired for the lowest possible order (which defines the number of reactive elements needed for the filter implementation).

3. The model is described by the following¹:
where
A(f) is the loss in dB,
R_n is the n^th order Tschebycheff rational function, and _.

4. The magnitude of the transfer function, |H(jw)| is equal to the inverse of the loss:

5. There are three input options:

i. Set AMAX, AMIN, FC, FS. The sharpness of the filter is calculated as FS/FC, and the order of the filter is calculated numerically from the four given parameters.

ii. Set AMAX, AMIN, FC, KP. The sharpness of the filter is given, and the order of the filter, N, is calculated numerically as a function of the four given parameters.

iii. Set AMAX, AMIN, FC, and N. The order of the filter now determines the sharpness of the filter, which is calculated numerically as a function of the given parameters.

6. The normalized low pass prototype filter is designed for w_c=1 (where w_c=2pf_c). A frequency transformation is performed for the low pass filter, where the transformed w is given by:

7. Range for N: 2 < N < 15

Netlist Form

ELLPF:NAME n1 n2 AMAX=val AMIN=val {FC=val,FS=val | FC=val,KP=val | FC=val,N=val}[R1=val] [R2=val] [IL=val]

Netlist Example

ELLPF:1 1 2 FC=2ghz FS=2.1ghz AMAX=0.01 AMIN=40

ELLPF:2 1 2 FC=2GHZ N=10 AMAX=0.01 AMIN=40

ELLPF:3 1 2 FC=2GHZ kp=0.96 AMAX=0.01 AMIN=40

References

1. Approximate Methods for Electronic Filter Design, Richard W. Daniels, Bell Telephone Labo­ratories, Inc., McGraw-Hill Book Company, 1974.

2. Handbook of Filter Synthesis, Anatol I. Zverev, John Wiley & Sons, 1967.

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