2Last Time Outline Butterworth LPF Design General Cases Other Filters LPF to HPF ConversionLPF to BPF ConversionLPF to BRF ConversionGeneral CasesDual NetworksRL≠RSOther FiltersChebyshev filterBandpass Design ExampleBessel filterFilter Synthesis via Genesis
3Low Pass Filter Design Requirement fc=1 MHzAttenuation of 9 dB at 2 MHz.RS=50 OhmsRL=25 Ohms
4Determine the number of elements in the filter (Same as before)9 dB of attenuation at f/fc of 2.
10Comments 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.
11Chebyshev ResponseChebyshev 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
12Comparison of a third order Passband Filter 3 dB of passband ripples and 10 dB improvementin attenuation
13Design MethodologyEven though attenuation can be calculated analytically, we will use the graphical method.Even order Chebyshev filters can not have equal termination (RS≠RL)
14Low Pass Filter Design Requirement fc=1 MHzAttenuation of 9 dB at 2 MHz.RS=50 OhmsRL=25 OhmsLess than 0.1 dB of RippleDesign it with a Chebychev Filter