Tunable Dual-band Microwave Photonic Filters Covering 37.2 GHz to 186.1 GHz Utilizing Chirped Sampled Gratings

We present a microwave photonic filter featuring dual independently tunable passbands.Constructed with linearly chirped sampled Bragg gratings incorporating two equivalent phase shifts, supplemented by microheaters, this filter exhibits a tunable frequency range spanning from 37.2 GHz to 186.1 GHz. IntroductionWith the ongoing expansion of mobile communications, satellite communications, and Internet of Things (IoT) applications, the demand for multiband communication in wireless Radio Frequency (RF) systems is increasingly growing.Microwave photonic filters (MPFs), as critical components in microwave photonics, are receiving significant attention due to their outstanding frequency selection, filtration performance, and dynamic tunability.To meet the dynamic operational demands of multiband communications, the development of adjustable and reconfigurable multiband photonic filters is urgent.Recent studies have reported on the design of various tunable dual-band microwave filters, which can be implemented either through two cascaded micro-ring resonators (MR) [1] or distributed feedback Bragg-grating resonators (DFBR) [2], or by using a single resonator configuration such as the equivalent phase shift fiber Bragg grating (EPS-FBG) [3] and the dualarm Mach-Zehnder interferometer (MZI) [4].In this paper, we report for the first time an MPF with two independently tunable passbands within a single channel of a single grating, achieved using a chirped sampled grating (CSG) with two equivalent phase shifts (-EPS) and microheaters (MHs).The proposed structure is based on the reconfigurable equivalent chirp (REC) technique [5], symmetrically introducing two -EPSs within the CSG, thereby generating two independently tunable passbands.Compared to traditional MZI and MR, the CSG with two -EPSs filter offers narrow passband frequencies and a large tunable frequency range unrestricted by the Free Spectral Range (FSR), presenting unique advantages in wavelength selectivity and multiplexing capabilities, which are particularly critical for RF manipulation.