I'm looking at implementing an LC bandpass filter, where I want upper and lower cut off frequencies to be 1254 Hz and 48 Hz respectively.

Based on the pictures I've added - from http://www.radio-electronics.com/info/rf-technology-design/rf-filters/simple-lc-bandpass-filter-design.php - I'm looking at implementing the T Section filter and have attempted to work out values of components, the only issue being that a characteristic impedance is required. Previously, I only really understood this to be associated with transmission lines, however, I last night seen someone say they chose a value and placed an equivalent resistor after the source. Is this a method I should also use?

I will also need to amplify the voltage by around 60dB and as I understand it this should be between the high pass filter and the low pass filter, which way is best to amplify?

Any help is greatly appreciated.

Additional information: The source is a radar motion sensor output, whose voltage is approximately 4mV and a frequency of 21MHz.

T Section and Pi Section LC Filters

Corresponding filter component equations

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    \$\begingroup\$ You need to specify the requirements of the filter before you can design it. This includes the source impedance, the load impedance, the stop band rejection level, the flatness within the band, etc. Since your low and high frequencies are so far apart, your best approach is probably separate low and high pass filters rather than a bandpass design. Also since your frequencies are so low, RC filters are probably a better approach because the inductor values for an LC filter are going to be fairly large. \$\endgroup\$ – Barry Mar 28 '18 at 12:24
  • \$\begingroup\$ @Barry Do you suggest the RC filter under the 'Active Band Pass Filter' heading here: electronics-tutorials.ws/filter/… \$\endgroup\$ – Jandy12 Mar 28 '18 at 12:27
  • \$\begingroup\$ That seems like a reasonable approach. \$\endgroup\$ – Barry Mar 28 '18 at 16:08
  • \$\begingroup\$ Define Passband -3dB and group delay error at both edges then bandreject attenuation with slope. A more complex 10th order active Bessel filter may be suitable using TI Filter tool but depends on pass ripple , group delay and skirt slope ( in addition to what Barry said.) \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 28 '18 at 19:32

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