Birinchi harmonikni signalning diskret signalini vaqt domenidan chastota domeniga o'zgartirish uchun foydalaniladi. Birinchi harmonikni hisoblash uchun signalning vaqt domenidan N namunalar olinadi. Keyin DFT dan signalning chastota domenidagi ko'rsatmalarini hisoblash uchun foydalaniladi, bu esa kompleks koeffitsiyentlar qatoridan iborat. Birinchi harmonik DFTning birinchi koeffitsiyentiga mos keladi, uni quyidagi formula yordamida hisoblash mumkin: c_1 = (1/N) * Σ[n0 to N-1]_x{\displaystyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle \scriptstyle
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