[SOLVED] How would multiplexer for bio-medical signals would work ?

How would multiplexer for bio-medical signal work ?

My thesis is about this, a mutilplexer for bio-medical signals. The point of it is to take the cardiac signal and respiratory signal from the vital support machines, make them go through a multiplexor and then eventualy send it via internet to another device so the doctor can remotely keep track of the patient. I'm aware that there are far more variables to control in an ICU but to simplify the project for now we will only work with those two.

My project as I said before is only the multiplexing part. I'm supposed to finish the last phase of it today (which is basically finally explaining how the whole thing works) and I'm shooting arrows in the dark, I have no clue how to work this out so I was hoping you could help me.

I talked to one of my teachers and I asked for some help and he gave me the following diagram which I was hoping you could help me figure out:


so we have our main signal (plus noise and interference)---> goes through a x32 amplifier--->goes through a band pass filter (0.1 Hz-120 Hz)---> Then goes through a low pass filter (60 Hz)---> then it goes through the sampling part--->quantification---->Codification....

Here's what I have figured out from that: Our main signal, say a cardiac signal goes through the amplifier because it's max possible amplitude is of about 500 mV which could be too small for the resolution of the AD converter (the digitization part). Then the signal goes through a series of filter to reduce the noise and eliminate the interference brought by the power source of the vital support machines and such. So basically what this whole part of the process has done is clean up and prepare the signal for the the digitizing part (am I right ?). So here's when I don't know what else do to, I'm not quite sure what comes next on the sampling part, quantification and codification.

On the previous phases of the thesis we have established that we will use ASCII code of 8 bits for the codification part. Also we chose "natural sampling" (apparently). So can anyone please explain this to me ? I had to catch up on this thesis after they started to I'm having a hard time figuring things out. Any help, advice or observation that you can provide would be highly appreciated. Thank you very much.

Your thoughts and views are appreciable and understood.

Firstly you need a 2 to 1 Multiplexer for transferring each of those signals.

Also it is must to have sampling/quantizing/coding techniques prior to multiplexing. The reason for this is mentioned by you as transferring through internet to other device.

Also i wish you would prefer Time Division Multiplexing(TDM).

Regarding encoding style its upto you to choose any of the available techniques.

Let me know your views on this.

All the very best to your project.

Yes exactly, that's what our teachers advised, to use TDM but I'm not exactly sure how to do this. I'm so glad you answered, thank you very much.

Can you perhaps explain to me how to ensemble all this concepts together ? Because so far all I've got is the blocks diagram i described above. I've been analizing I think I've gone a little bit farther since I think I know what the sampling frequency would be. According to Nyquist it should be twice or above the highest frequency on the original signal, am I right ? I would really appreciate all the help you could give me, I'm literally shooting arrows in the dark. Am I missing something, is the diagram complete for what it was intended to be, a multiplxer of bio-medical signals ?

Again, thank you so much for your help !

Firstly as it is a real-time project i want you to make a study on the bio-medical signals and its frequencies which you are going to use in your project.

Later its a sequential implementation.

Are you doing this in real-time or in simulator?

multiplexer means you have many input signals channels directed to some output channels. Your have two options here:
1) analog multiplexer - your have say two analog signals from a patient a) heart beat b) blood pressure and one analog channel as output. Your job is to develop a switch that will select one of two input to be send to one channel output.
2) digital multiplexer - input and output are digital. If you study digital electronics you will find how to build one.

THere are hundreds of ways to make a TDM ADC with real-time filtering, compression, companding or linear with any bit rate.. like DVD audio 7.1 channels or like biomedical signals. Here is on complex chip for audio **broken link removed** that shows how it is done well. But then this PhD thesis in 1977 is more interesting.. BTW I have designed many TDM ADC networks with TDM DAC outputs but that was decades before the internet was invented.