Matched filter (pulse compression) Design in LTSPICE

[kunene]

Hi guys

Im currently working in an ultrasonic level detector project. Where I need to send 40Khz sound waves and receive the echo through the piezoelectric sensors which in turn the signal received should be filtered for noise (increasing the S/N ratio).

So my biggest problem is in designing that filter (matched filter/pulse compression) in LTspice. I would like to ask for your help in designing this.

Looking forward to hearing anything you can share.

 

[crutschow]

You don't "design" a filter in LTspice, you design the circuit and then simulate it in LTspice to confirm that your design is correct.

Have you done any research to determine what filter characteristics you need? You must have that before you can do the design.

 

[kunene]

Oh yes, I have done quite a research I think, but all I come up with is a lot of theory. I never learnt about matched filter in colleague, which is why Iit happens to b quite challenging to me. All I know is about low, high and band-pass filter. About the matched/pulse compression filtering I don't even know how the circuit is supposed to look like.

So my question is to know about the circuit characteristic here (LTspice simulation, I think is is least of the problem). thanks in advance.

 

[ronv]

Why do you need the filter. How far are you trying to measure?

 

[kunene]

I need the filter to filter any noise that might be present in the echo which will be detected by the receiver sensor, you can see the attached file for the piezoelectric sensors that will be used. the distance from the transmitter to the target object(surface of the water) wont be longer than 5m.

So the output of the receiver sensor should go straight to the filter, and after the filter, go to the peak detector(another part that I already handled).

 

[ronv]

I don't think you will have any problem with s/n at 5 meters without the fancy filter.
Just give it a little ping and listen for the echo.

Take a look at a simple one.

https://www.buildcircuit.com/tag/ultrasonic-range-finder/

 

[kunene]

I have looked to that one, and it really is a good option, but it is a requirement for me to design the matched filter/pulse compression.

So it would help if anyone shares about the matched filter/pulse compression circuit.