Normalized Phase and Gain Derivatives as an Aid in Evaluation of FM Distortion

Second and third order harmonic distortions are evaluated which are generated in a network of known transfer functions when subjected to an undistorted FM input signal. From the general Carson and Fry formula for the response of the network, both quasi-stationary and nonquasi-stationary terms can be evaluated with the aid of normalized derivatives of the gain and phase function of the network. These normalized functions can be calculated by adding contributions of every significant pole and zero of the transfer function. The distortions are evaluated in discrete terms and presented in a form which lends itself well to quantitative discussion. One numerical example is included.