This 3 pole bandpass filter using
https://wetnet.net/rf_design/3pole.main.cgi design calculator online.
this bandpass filter is butterworth filter and intended to filter digital tv bandwith 470MHz to 800 MHz , and only this signal will detected after antenna.
Parameter of filter :
Band Frequency 470 - 800 MHz
Center Frequency = 635 MHz
Bandwith = 400 MHz
Impedance = 50 ohm
Input this parameter to online filter calculator above :
Click Submit , and the result :
L1,L3 : 0.008763 uH ( 8,763 nH)
L2 : 0.039789 uH (39.789nH)
C1,C3 : 0,000008 uF ( 8 pF)
C2 : 0,000001753 uF (1,753 pF)
We must determine for Inductor L1,L2,L3 the coil diameter, coil length and number of turn of coil.
Using online calculator from
http://www.qsl.net/in3otd/indcalc.html we can determine diameter, length and number of turn coil.
For L1,L3 :
L = 0,00876 uH , coil diameter will be d : 0,01 m , Coil length will be l : 0.01 m and number of turns , n : 1,1355
And for L2 :
L = 0,0396 uH , coil diameter will be d : 0,0259 m , coil length will be l : 0,01 m and number of turns n : 1,1355
The most important thing of build filter is the connection between component should be as close as possible, for avoiding wild capacitance that will generate noise, and the ground area of PCB should be good and wide.
On the next article, I will posting the implementation of this filter.