RF Electronics Chapter 7: RF Filters Page 213
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
Chebyshev Filters
The Chebyshev filter has ripples in the passband and the value of the ripples is a parameter
that is selected as part of the filter design. The filter of figure 7.5 has a 0.1 dB passband
ripple as shown on figure 7.6. The inductors and capacitors for the Chebyshev filter are
larger than those used in Bessel or Butterworth filters. The Chebyshev filter has a very
sharp attenuation response in the stop band, with a -60 dB attenuation at 967 MHz,
compared with 1.3 GHz for the same attenuation for the Butterworth filter. Increasing the
passband ripple will increase the passband attenuation. The group delay for the
Chebyshev filter is larger than that of the Bessel and Butterworth filters. As a result, the
Scale on figure 7.6 is different from figure 7.2 and 7.4.
Figure 7.5. Chebyshev Lowpass Filter.
Figure 7.6. Chebyshev Lowpass Filter Frequency Response.
Cauer-Chebyshev Filters
A Cauer-Chebyshev filter is a derivative of the Chebyshev filter and has capacitors in
parallel with the inductors to cause zeros in the stopband as shown in figure 7.7. The zeros
are placed, such that the minimum stopband attenuation values are the same as shown in
figure 7.8. This gives an even higher stopband attenuation, with a 60 dB attenuation at
628 MHz compared with 1.3 GHz for the Butterworth filter. The Cauer-Chebyshev filter
has an even bigger variation in the group delay than the Chebyshev filter and will thus
have very poor transient response. The group delay of the Chebyshev and Cauer-
CAP
ID=C1
C=8.031 pF
CAP
ID=C4
C=8.031 pF
CAP
ID=C3
C=14.26 pF
CAP
ID=C2
C=14.26 pF
PORT
P=2
Z=50 Ohm
PORT
P=1
Z=50 Ohm
IND
ID=L3
L=24.19 nH
IND
ID=L2
L=26.74 nH
IND
ID=L1
L=24.19 nH
RF Electronics: Design and Simulation
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