Fig. 1. Schematic diagram of microwave photonic filter (MPF). (a) MPF based on single microring; (b) MPF based on cascaded three microrings

Fig. 2. Frequency tuning of MPF filtering center and bandwidth tuning of MPF. (a) Schematic diagram of frequency tuning; (b) schematic diagram of bandwidth tuning

Fig. 3. Structures of waveguide and microring resonator (MRR). (a) Cross section of double stripe silicon nitride waveguide; (b) schematic diagram of all-pass MRR; (c) schematic diagram of cascaded three microring filter

Fig. 4. Simulation results of MPF based on cascaded three microrings. (a) Radio frequency (RF) response image: ① Low frequency band (3.0~8.3 GHz); ② intermediate frequency band (8.3~9.5 GHz); ③ high frequency band (9.5~20.0 GHz); (b) phase differences of photocurrents from beating between optical carrier and ±1 order sidebands; (c) amplitude differences of photocurrents from beating between optical carrier and ±1 order sidebands; (d) comparison between RF responses of MPF based on single microring and cascaded three microrings

Fig. 5. Photo of packaged chip

Fig. 6. Transmission spectra measurement setup for MRR

Fig. 7. Measured transmission spectra. (a) Transmission spectra of single microring; (b) transmission spectra of cascaded three microrings; (c) transmission spectra of combined three microrings

Fig. 8. Experimental setup for characterizing MPF based on cascaded three microrings

Fig. 9. Comparison of RF responses of MPFs based on single microring and cascaded three microrings

Fig. 10. Measurement results of MPF based on cascaded three microrings. (a) Bandwidth tuning; (b) frequency tuning