This paper investigates the real-valued sine-wave amplitude and phase estimates returned by two Frequency-domain Linear Least-Squares (FLLS) algorithms. Both algorithms are based on Discrete Time Fourier Transform (DTFT) samples evaluated at the sine-wave frequency in order to maximize the immunity to wideband noise. One of the analyzed procedures, called FLLS algorithm, is affected by the contribution of the spectral image component on the estimated parameters. The other one, called enhanced-FLLS (e-FLLS) algorithm, compensates this detrimental contribution which is particularly significant when a small number of sine-wave cycles is observed. The image component interference compensation is obtained at the cost of a lightly higher computational effort and noise immunity. Closed form relationships for both the analyzed estimators and their variances are provided. Analytical expressions for the estimators which avoid matrix operations are also derived under conditions of practical interest. Finally, the accuracies of the analyzed algorithms are compared with a state-of-the-art estimator based on the classical three-parameter sine-fit algorithm, through both theoretical and simulation results. Index terms -Frequency-domain analysis, least-squares approach, parameter estimation, real-valued sine-wave, windowing.number of acquired sine-wave cycles ν is not too small so that the contribution of the spectral image component can be neglected, from (4) we have [15]:noticing that the matrix V J is equal to the identity matrix I (2J+1) when the rectangular window is adopted.From the definition of B, the following estimates for the sine-wave amplitude and phase are obtained:, (14) -(16) returns: 2 CR J A J J M J 2 ] var[ CR J J J SNR M J J + ≅ SNR M J J J (22) when δ is estimated a-priori. * , T J J J e 1 * , , J w J J e J e J J e J e 2 1 , 1 * , , M W V W NNPG B J e J J e J e σ − − CR J e J J e J e J J e J e 2 , 1 CR J e B J J M J CR J e J J SNR M J J A A J J J J J − − ] var[ 0 ENBW J J A A J J ] var[ 0 ENBW J J A A J J ) ( J J j J j J J k w J w J e J e J k J k k w J w