An amplitude-modulated analog waveform has a maximum amplitude Amax and a minimum amplitude Amin (a positive value), then the modulation index is given by
1
\(\frac{{{A_{min}}}}{{{A_{max}}}}\)
2
\(\frac{{2{A_{min}}}}{{{A_{max}} + {A_{min}}}}\)
3
\(\frac{{{A_{max}} - {A_{min}}}}{{{A_{max}} + {A_{min}}}}\)
4
\(\frac{{{A_{max}} - {A_{min}}}}{{2\left( {{A_{max}} + {A_{min}}} \right)}}\)