Photonic implementation of a highly reconfigurable wideband RF spectral shaper

Abstract

In emerging Radio Frequency (RF) systems, the capability to dynamically process a wide range of frequency bands is highly desired due to the multi-frequency operation in multi-function RF systems and the large signal bandwidth usage associated with data-intensive applications. As the operation bandwidth increases, the frequency response uniformity of both RF components and microwave transmission medium degrades, that leads to the need of broadband RF spectrum equalization to support wideband high-quality services. Therefore, a wideband and reconfigurable RF spectral shaper is highly desired for dynamically manipulating the RF spectrum from low- to high-frequency band. Unfortunately, it is very challenging for conventional RF electronics to achieve dynamic spectral control over a wide operation bandwidth. In this paper, we take advantages of photonics and demonstrate a highly-reconfigurable RF spectral shaper that can manipulate an RF spectrum of tens of GHz wide. The proposed scheme is based on a microwave photonic filter architecture with multiple tunable, reconfigurable and switchable passbands. By manipulating the shape, bandwidth, and frequency of the passbands, highly reconfigurable wideband frequency responses for spectral equalization are experimentally achieved, covering the entire 0 to 10 GHz frequency range with adjustable attenuation up to 40 dB. Various RF equalization functions including tunable positive/negative slope, non/inverted parabolic, and multi-point spectral control with tunable floor are experimentally demonstrated using the proposed system. Several of the demonstrated RF functions have also been applied to arbitrary pulse shaping. The RF spectral shaper can be tuned to adapt to different scenarios dynamically, which could benefit a variety of applications including RF signal processing systems and communication networks.