Receiver for Jupiter
|RF Amp||Narrow Band Pass Filter||Mixer||Low Pass Filter||Audio Preamp||Audio Power Amp|
Low Pass Filter
Low pass filter band limits the mixer o/p to audio frequencies
up to 3.3 KHz. Also to have less loss and sharp cutoff the active filter is
used. The filter is having 5th order low pass Sallen-Key configuration. The
filter is 60dB down at 10KHz and having 3dB cut off of 3.3KHz.The response
of the filter is selected as Chebyshev to have sharp cutoff.
To have fifth order response the two-pole section and three-pole section are cascaded. The operational amplifier is configured in the voltage follower configuration, which has a close loop gain of unity, very high i/p impedance and nearly zero o/p impedance. The opamp OP27 is selected which is the precision operational amplifier.
(One can use the passive filter and audio section after the mixer as given in Jove receiver manual.)
Response of the Active Lowpass filter: - (Simulated in Eagleware)
Only drawback in the use of this filter is the requirement of Dual power supply!