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Can anyone with more experience give me some insights on the feasibility of using a Variable Bandpass Tuner as an Analog Radio source?

Here is my VBT Design based off a state variable filter:

Its center freq and BW are functions of the resistor labeled myQ and the capacitors labeled C_s.

For variable resistors I was considering using DACs, although im not too familiar with how to use them as digi pots, so analog pots may be the way to go. As far as variable caps go, please provide any recommendations on how I could do this. I was considering having "in-line" caps hooked up to a mux to allow me to select the capacitance I want from discrete values. Any suggestions?

Variable Bandpass Tuner Design

Noting the spice op codes that show my component calculations, where Rs is equal to my impedance scale value.

Variable Center Frequency DEMO:

r/rfelectronics - Feasibility of Using a VBT as an Analog Radio Source or Audio Equalizer r/rfelectronics - Feasibility of Using a VBT as an Analog Radio Source or Audio Equalizer
Photo from my report

Questions:

Would an antenna hooked up to LNA feeding my VBT design be a feasible way to receive AM radio? I know RF stuff is pretty sensitive so I'm wondering if a more advanced technique would be needed. I was reminded about the superheterodyne receiver arch, but I am looking for a easy implementable solution and don't really have time to design around I.F. solutions with Mixers and having to worry about aliasing. Is an S-parameter analysis needed here?

Background on Application:

I am making an audio equalizer for class and want to make it more interesting since i've already done this project at prior uni.

Here is a very rough block diagram of what i'm thinking about doing.

Mux chooses input

Amplify signal so that noise from BPF isnt as effective

Bandpass filters are Active 4th Order Multiple Feedback Topology BPF.

Each BPF has non-inverting amp with gain based off pots

All go into summing amplifier

Then to a VBT to amplify specific freqs, noting I also have a design for variable notch filter based off the vbt, thus allowing for elimination of any ugly freqs.

Then go into class d amp using a high side and lowside approach using mosfet drivers, then to impedance matched speakers.

r/rfelectronics - Feasibility of Using a VBT as an Analog Radio Source or Audio Equalizer
Full Audio System

Disclaimer I'm just a student; any help or suggestions is much appreciated.

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1 Answer 1

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Would an antenna hooked up to LNA feeding my VBT design be a feasible way to receive AM radio?

Not even in the slightest way is this a feasible method to receive and demodulate an AM radio signal.

Regular AM radio transmissions have a carrier of at least 100 kHz and that is miles above the frequency that your bandpass filter can usefully handle. You then need to demodulate the carrier using an envelope detector.

I suggest you study how an AM radio transmission is filtered and demodulated.

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