The application of linearly swept frequency measurements

The theory of linearly swept frequency measurements has been studied [M. A. Poletti, J. Audio. Eng. Soc. 36(6) (1988)]. This theory shows that the Fourier transform of a linear system impulse response may be produced as a function of scaled time by convolving, multiplying, and reconvolving the impulse response with infinite duration, complex linear frequency‐modulated (FM) signals. The first convolution is implemented by injecting a linear FM signal into the system. The multiplication may be viewed as a synchronous detector that removes the carrier from the output of the system. The third operation may be viewed as a quadratic phase filter that removes the skewing distortion to produce the true transfer function as a function of time. The application of the theory using finite real signals is discussed. It is shown that for a finite duration impulse response a suitably time‐limited signal may be injected into the system which produces the response that would be produced with an infinite signal, and that t...