Square or Sine: Finding a Waveform with High Success Rate of Eliciting SSVEP

Figure 1

(a), (c), and (e) are the luminance figures of an LED measured by a Lutron LX-102 light meter. Their corresponding frequency representations are given in (b), (d), and (f), respectively. The spectrum of the square wave strictly adheres to theory, that is, a peak demonstrated at fundamental frequency 𝑓 as well as a peak at the 3𝑓 harmonic. The sine wave and the triangle wave do not. They have weak harmonics that should not exist at 2𝑓. However, these harmonics should not affect the result, since their strength are one tenth that of the fundamental frequency.

(a) 22 Hz sine

(b) Spectrum of sine wave

(c) 22 Hz triangle

(d) Spectrum of triangle wave

(e) 22 Hz 50% duty cycle square

(f) Spectrum of square wave