Design of analogue and digital phase-complementary filters

The measurement of instantaneous spectral energy by the traditional bandpass, rectify and smooth method leaves much to be desired when the signal has a high transient content. The paper presents analytic methods for the designing of `phase complementary¿ filters based on the tke¿at general time window, in both the continuous and discrete time domains. These filters can provide a well-defined measure of instantaneous spectral energy. Digital variants are shown to be capable of computationally efficient practical implementations.