Linear time-invariant (LTI) systems find ubiquitous applications in digital signal processing [1], image processing [2], communication [3], and array processing [4], to name a few. An LTI system can be characterized by its impulse response, which is defined as the output response to an impulse input. For an arbitrary input signal, the output signal of an LTI system is obtained by the convolution of the input signal with the impulse response. This property is closely related to transform-based methods in signal processing, such as discrete-time Fourier transforms, z-transforms, and discrete Fourier transforms. Interested readers are referred to [1] and the references therein.