Analog real-time Fourier transformer using a group delay engineered C-section all-pass network

The characterization and measurement of ultra-fast signals have become increasingly important with the emergence of ultra-wide band systems. In this context, real-time systems are required to effectively analyze and manipulate signal spectra in many microwave and millimeter-wave applications. In optics, the real-time Fourier transform is a well-known concept, where the spectrum of the signal is measured in the time domain from propagation in a first-order dispersive medium [1]. This principle has been recently applied to microwave signals using a reflective-type dispersive structures [2]. This paper presents an analog real-time Fourier transforming system based on transmission-type group delay engineered all-pass structures. In this system, the limitation on the time duration of the measurable signal is significantly relaxed as a result of the chirp inversion technique being employed.