Patent ID: 8473534

Claim:
A method for use in a digital frequency synthesizer, the method comprising phase to amplitude conversion of an output value of a phase accumulator in said synthesizer, said coversion being carried out as an approximation of an amplitude which corresponds to an output phase value of the phase accumulator, wherein the approximation comprises a combination of a linear interpolation value and a second order sinusoidal term, the second order sinusoidal term being used as an error term to correct for errors in the linear interpolation value, wherein the approximation is expressed as y ⁡ ( x ) ≈ Y ⁡ ( k ) + Y ⁡ ( k + 1 ) - Y ⁡ ( k ) d · ( x - kd ) + Y ⁡ ( k ) · Y ⁡ ( ⌊ x - kd d · 2 N - 1 ⌋ ) · [ 1 - cos ⁡ ( d 2 ) ] , ⁢ ⁢ k = ⌊ x d ⌋ where: d=2π/2 N , with N being a natural number, and Y(k)=sin(k·d), and k = ⌊ x d ⌋ means that k is the integer part of x/d, x is from 0 to 2π radians.