1kHz square wave hardware decomposer based on bandpass filter

1. Engineering Principles
According to Fourier analysis, a square wave can be decomposed into a series of sinusoidal signals. The square wave in the interval [0, T] can be expressed as: A band-pass filter refers to a filter that can pass frequency components in a certain frequency range, but attenuate frequency components in other ranges to a very low level. The Butterworth filter is characterized by the smoothest frequency response curve in the passband. This type of bandpass filter is used in this project to decompose the square wave into the fundamental wave, the third harmonic, and the fifth harmonic...
 
2. Circuit structure
circuit The topology is determined using ADI's filter wizard, and the op amp uses a universal single op amp OP07C.
Filter Wizard: https://tools.analog.com/cn/filterwizard/
 
The circuit is divided into three parts:
the first part is a tenth-order Butterworth bandpass filter with a center frequency of 1kHz, composed of 5 pieces of OP07C, which is responsible for decomposition The fundamental wave of the square wave is output;
the second part is a tenth-order Butterworth bandpass filter with a center frequency of 3kHz, which is responsible for decomposing the third harmonic;
the third part is a sixth-order Butterworth bandpass filter with a center frequency of 5kHz. The converter is composed of 3 OP07C pieces and is responsible for decomposing the fifth harmonic;
an adder circuit is designed at the bottom, which can superimpose the fundamental wave, the third harmonic and the fifth harmonic in equal proportions, and observe the mixed waveform. LM358DT implemented.
 
3. The experimental test
uses a signal generator to generate a square wave signal with a frequency of 1kHz and an amplitude of 5V. Connect the oscilloscope probe to the output point on the board. It can be observed that the square wave of 1kHz is decomposed into a fundamental wave of 1kHz and a third wave of 3kHz. harmonics and the fifth harmonic of 5kHz.