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Ansoft Designer / Ansys Designer 在线帮助文档：

Nexxim Simulator >
Nexxim Component Models >
Nexxim Filters >
   Bessel-Thompson Band Pass Filter       

Bessel-Thompson Band Pass Filter

Netlist Form

An instance of a Bessel-Thompson band pass filter has the following Nexxim netlist syntax:

Axxx n1 n2 [N=val] [FL=val] [FU=val] [R1=val] [R2=val] [IL=val] COMPONENT=bessel_bandpass_filter

n1 and n2 are the nodes connected to the filter. The entry COMPONENT=bessel_bandpass_filter is required.

Netlist Example

A22 1 2 N=5 FL=80e6 FU=100e6 IL=0.5
+ COMPONENT=bessel_bandpass_filter

Notes

1. Bessel-Thompson filters are derived from a maximally-flat delay criterion (the first n derivatives of the delay are zero at the origin). As a result, they exhibit very good group delay characteristics, at the cost of poor attenuation performance in the stopband.

2. The transfer function of the Bessel filter (low-pass prototype) is given by [see Reference 1]:

where B_n(jw) is the Nth-order Bessel polynomial, and b₀ = B_n(0).

3. The normalized low-pass prototype filter is designed for a cutoff frequency w_c=1. To change the response of the filter to a band-reject, a frequency transformation is required, where w is substituted by {Reference 3]:

where w₀ is the geometric mean of the edge frequencies, w_L and w_H, of the stopband:

4. The range for N (order of filter) is from 1 to 15. Orders higher than 15 cannot be simulated.

References

[1] Approximation Methods for Electronic Filter Design, Richard W. Daniels, McGraw-Hill, Inc.

[2] Handbook of Filter Synthesis, Anatol I. Zvered, John Wiley & Sons, Inc. 1967.

[3] Microwave Engineering, 2nd Ed. David M. Pozar, John Wiley & Sons, Inc. 1998.

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