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The experiment consists of an ideal square wave generator. An ideal square wave is constructed of an infinite number of sinusoidal odd harmonics. To define the amplitude level of the fundamental frequency, the 3rd,5th,7th and 9th harmonic we use a few notch filters. They clip off (very sharply) one specific frequency while leaving all others. As you can see at each notch filter we see an ever decreasing series of ever increasing in frequency, harmonics. Now if we want to measure the amplitude of each harmonic, we take a look at every connection between L and C. For the fundamental frequency, the amplitude is 6.34V. This means that around 3/4 of the whole wave is comprised of the fundamental. The remaining 3.66V are split between an infinite number of harmonics. The most prominent are the 3rd (1.23V), the 5th (541mV), the 7th (300mV) and the 9th (236mV). They keep increasing, while their amplitude keeps decreasing, and in reality, no square wave is comprised of an infinite number harmonics, but actually quite finite. Also since in reality there is no such thing as ideal, every square wave will also contains even number harmonics.
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