Hi
I am doing a small project and one of the things I need is a radio receiver as I am trying to pick up the signal from a remote control. It would actually be ideal if I could just buy a receiver off the net somewhere, but unfortunately it isn't quite an ordinary receiver I need.
I have no interest in the information carried in the signal but only in how the carrier wave "looks". Ideally I would like to lead the signal directly into an AD converter and sample the "raw" signal. Unfortunately the signal is at 434.5 MHz which would mean an AD converter well outside my price range (not to mention the circuit design needed).
So I need some kind of radio receiver. After looking around on the net I figured that the superhetrodyne receiver would work, but instead of actually going all the way and extracting the data I would simply chose the IF to be in the low Mhz and sample that signal (I have a 25MHz ADC).
I have attached my receiver design as it is right now. It does work somewhat, but it isn't really that sensitive. If the remote control is more that 10m away the signal is very bad. Another thing is that if I do a FFT of the IF the overtones (IFx2,3,4,5,6.... etc) are quite strong in the signal and generally there's a lot of noise.
A few hard fact about the system:
Overview:
Antenna-->Bandpass(center frequency 434.75MHz)-->LNA-->LNA-->Mixer(431MHz LO)-->amp->Bandpass(center frequency 3.75MHz)-->amp-->ADC
I am using using ICs where possible to try and avoid having to design RF amps myself.
Mixer is a SA612A
LNA (amplifier) is a BSG2011 (I have used this one for all my amps).
Received signal is 434.75 MHz.
Finally, the question.
How could I improve it or what design would be better? By better I guess I mean more sensitive and with less noise/overtones in the IF.
I hope it was explained well enough and that you can help me.
EDIT: Ups... just noticed C36 on the diagram. I used it to bypass the amplifier to see how much of a difference the amplifier did, so it's not on the actual circuit board.
I am doing a small project and one of the things I need is a radio receiver as I am trying to pick up the signal from a remote control. It would actually be ideal if I could just buy a receiver off the net somewhere, but unfortunately it isn't quite an ordinary receiver I need.
I have no interest in the information carried in the signal but only in how the carrier wave "looks". Ideally I would like to lead the signal directly into an AD converter and sample the "raw" signal. Unfortunately the signal is at 434.5 MHz which would mean an AD converter well outside my price range (not to mention the circuit design needed).
So I need some kind of radio receiver. After looking around on the net I figured that the superhetrodyne receiver would work, but instead of actually going all the way and extracting the data I would simply chose the IF to be in the low Mhz and sample that signal (I have a 25MHz ADC).
I have attached my receiver design as it is right now. It does work somewhat, but it isn't really that sensitive. If the remote control is more that 10m away the signal is very bad. Another thing is that if I do a FFT of the IF the overtones (IFx2,3,4,5,6.... etc) are quite strong in the signal and generally there's a lot of noise.
A few hard fact about the system:
Overview:
Antenna-->Bandpass(center frequency 434.75MHz)-->LNA-->LNA-->Mixer(431MHz LO)-->amp->Bandpass(center frequency 3.75MHz)-->amp-->ADC
I am using using ICs where possible to try and avoid having to design RF amps myself.
Mixer is a SA612A
LNA (amplifier) is a BSG2011 (I have used this one for all my amps).
Received signal is 434.75 MHz.
Finally, the question.
How could I improve it or what design would be better? By better I guess I mean more sensitive and with less noise/overtones in the IF.
I hope it was explained well enough and that you can help me.
EDIT: Ups... just noticed C36 on the diagram. I used it to bypass the amplifier to see how much of a difference the amplifier did, so it's not on the actual circuit board.
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