What type of wave is composed of sine waves at the fundamental frequency and all odd harmonics?

The square wave is composed of sine waves at the fundamental frequency and all odd harmonics. When analyzing the frequency spectrum of a square wave, it is important to recognize that the waveform can be expressed as a series of sine waves where the fundamental frequency is present, alongside the odd harmonics (the 3rd, 5th, 7th, etc., frequencies).

This results from the mathematical representation known as Fourier series, which shows that a square wave can be reconstructed by summing these specific sine wave components. Each odd harmonic adds to the waveform's characteristics, giving it the distinctive sharp transitions seen in a square wave.

Understanding the harmonic content of waveforms is fundamental in signal processing and communications, as it helps to diagnose and interpret various signal properties and behaviors under different conditions.