A study which develops a controller design methodology that has flexibility of eigenstructure assignment within the stability-robustness contraints of LQR is requried and has been performed. The previously developd control design methodology, namely, EALQR(Eigenstructure Assignment/LQR) has better performance than that of conventional LQR or eigenstructure assignment but has a constraint for the weitgting matrix in LQR, which could be indefinite for high-order system. In this paper, the effects of the indefinite Q in EALQR on the frequency domain properties are analyzed. The robustness criterion and quantitative frequency domain properties are also resented. Finally, the frequency domain properties of EALQR has been analyzed by applying to a flight control system design example.