# convolving an LTI with filters

I just started learning signal processing and one of the very first topics I begun with is convolution. I want to learn signal processing practically, therefore I opted to work with circuits(also a newbie in this) in parallel.

In the first exercise I did, there is a piecewise linear function which I convolved with RC circuit(once by grounding capacitor(0.1 μF) and the other time by grounding resistor(10 kOhms)). The experiment is divided into two parts.

1. Simulating

I did circuit simulation in multisim and applied transient analysis to understand the convolution.

1. Using hardware measurement with NI myDAQ

I used NI ELVIS waveform generator to generate the signal to the circuit and NI ELVIS oscilloscope to graph the output and input to the RC circuit. I have attached both the transient analysis and oscilloscope graphs of low pass and high pass filtered output. After completing the experiment, I got few questions.

1. How well the input signal(amplitude of 5V) affects when I increase/decrease capacitance and/or resistance in the circuit?
2. In the simulation, the amplitude of filtered low pass signal is around 4.8 V whereas on real circuit, the amplitude is around 1 V. Could that be any mistake of mine or do the real circuit cause such high voltage drop? Or any other factors?
3. Also the waveforms in both cases look different. Especially in the high pass filter circuit, the waveform is in negative side. How should I understand this? If there is any underlying explanation that I need to know, it would really be helpful to understand the concept better. Thank you in advance.
• welcome to the DSP SE. i am not an English language expert but the words you might be looking for are "convolving" and "convolved". Jun 30 at 21:49