Download presentation
1
Filter Design (2) Jack Ou ES590
2
Last Time Outline Butterworth LPF Design General Cases Other Filters
LPF to HPF Conversion LPF to BPF Conversion LPF to BRF Conversion General Cases Dual Networks RL≠RS Other Filters Chebyshev filter Bandpass Design Example Bessel filter Filter Synthesis via Genesis
3
Low Pass Filter Design Requirement
fc=1 MHz Attenuation of 9 dB at 2 MHz. RS=50 Ohms RL=25 Ohms
4
Determine the number of elements in the filter
(Same as before) 9 dB of attenuation at f/fc of 2.
5
Use a Low Pass Prototype Value for RS≠RL
6
Comparison: RS=RL
7
Frequency and Impedance Scaling
8
Matlab Calculation
9
Low Frequency Response
10
Comments about Butterworth Filter
A medium –Q filter that is used in designs that require the amplitude response of the filter to be as flat as possible. The Butterworth response is the flattest passband response available and contains no ripples.
11
Chebyshev Response Chebyshev filter is a high-Q filter that is used when : (1) a steeper initial descent into the passband is required (2) the passband response is no longer required to be flat
12
Comparison of a third order Passband Filter
3 dB of passband ripples and 10 dB improvement in attenuation
13
Design Methodology Even though attenuation can be calculated analytically, we will use the graphical method. Even order Chebyshev filters can not have equal termination (RS≠RL)
14
Low Pass Filter Design Requirement
fc=1 MHz Attenuation of 9 dB at 2 MHz. RS=50 Ohms RL=25 Ohms Less than 0.1 dB of Ripple Design it with a Chebychev Filter
15
0.1 dB Attenuation Chart
16
0.1 dB, n=2, Chebyshev
17
Matlab Calculation
18
Chbysehv, 0.1 dB Ripple, LPF ripple
19
Typical Bandpass Specifications
When a low-pass design is transformed into a bandpass design, the attenuation bandwidth ratios remain the same.
20
Butterworth Vs. Chebyshev
Butterworth: n=4, 40 dB Chebyshev: n=4, 48 dB, but RS≠RL We have to settle for n=5, 62 dB.
21
Chebyshev, 5th Order, 0.1 dB Ripple
23
Effect of Limited Inductor Quality Factor
Assume each inductor has a quality factor of 10.
24
Minimum Required Q
25
Phase of Chebyshev Bandpass Filter
Phase is not very linear during the passband! You can get a lot of distortion!
26
Bessel Filter Bessel Filter is designed to achieve linear phase at the expense of limited selectivity!
27
Low Pass Filter Design Requirement
fc=1 MHz Attenuation of 9 dB at 2 MHz. RS=50 Ohms RL=25 Ohms
28
Attenuation Possible to achieve 9dB
29
Bessel LPF Prototype Elementary Value
30
Matlab Calculation
31
Bessel LPF 6.8 dB of attenuation at f/fc=2
32
Phase of Bessel LPF (n=2)
33
Genesys BPF Design Example
34
Typical Bandpass Specifications
When a low-pass design is transformed into a bandpass design, the attenuation bandwidth ratios remain the same.
35
Butterworth Vs. Chebyshev
Butterworth: n=4, 40 dB Chebyshev: n=4, 48 dB, but RS≠RL We have to settle for n=5, 62 dB.
36
Start Geneysis Select Passive Filter Start Genesys
37
Filter Properties
38
Comparison Synthesized Via Genesis Synthesized using Charts
39
Change Settings
40
QL=50, QC=100
41
QL=10, QC=100
42
Export Schematic to ADS
(Not sure. ADS project is open)
43
Tune You can also fine-tune the value of a component and see how it changes the filter response
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.