Filter Practice Problem for P.E. - Electrical

[AlexMarshall]

Hey everyone, I'm trying to get prepped from my EE Professional Engineering exam and there is a question that I cannot solve in the prep-guide. I'm hoping that someone might be able to help because it can be solved in MatLab (as noted in the book). Here is the problem description:

You are an engineer working at a major automotive manufacturer that offers a back-up/obstacle-detection system using sensors installed in the rear bumper. The sensors emit an ultrasonic signal ranging from 40-50 KHz. When an object is present, some of the ultrasonic signal is reflected back and the system will alert to driver to the obstacle. In minimal signal required for this detection is -70dBuV. The amplitude of the returned signal is indicative of the object's size.

Alongside the system, there is an electronic module radiating noise at 75 KHz. The level of this noise can be as high as -60dBuV. In order for this back-up system to function properly, the noise must be 15 dB below the desired signal. Note that the impedance and load impedance is 50 Ohms.

Problem:

Part A. Design an analog filter that will eliminate the impact of the noise on the system in a cost effective manner. Note any impacts that the filter may have on the back-up system.

Part B. Implement an Infinite Impulse Response (IIR) digital filter based on the analog filter in Part A. [utilize MatLab]

Part C. Implement a Finite Impulse Response (FIR) digital filter that will eliminate the impact of the noise on the system. [utilize MatLab]

I really appreciate any help that you all would have to offer! This is the one problem that I haven't been able to solve in the manual!

Thank you!

 

[Peele1]

PE prep questions are multiple-choice, and don't use MatLab. This looks like a homework assignment.

 

[benbo]

I'm very rusty, but can't you just cascade a few LPFs (Sallen Key) filters with a 50 KHZ cutoff until you get the proper amplitude response? I think these are just caps and resistors on op-amps, and they have a standard design. You could also do it with a bandpass filter, but I don't see the neccesity since the noise is all at a higher frequency.

I believe a Sallen Key filter is an IIR filter so I think you can just use the analog transfer function to create a similar transfer function in z. THen take a z transform of it to find the various delays you need. It might be complicated, hence the matlab.

I know the FIR filter is more complicated, I can't even remember how to design this, and it might take matlab to do it. Maybe you use the FFT.

I'm very rusty. It's been 20 years since I even thought about this, except for some extremely simple questions on the PE. If you are really talking about takling the PE and not a homework problem, you likely won't get anything like this.