A tunable Si3N4 integrated true time delay circuit for optically-controlled K-band radio beamformer in satellite communication

In this paper we present the design, realization, and\u3cbr/\u3eexperimental characterization of a photonic integrated true time\u3cbr/\u3edelay circuit on a CMOS-compatible Si3N4 platform. The true\u3cbr/\u3etime delay circuit consists of an optical side band filter for single\u3cbr/\u3eside band modulation and an optical ring resonator for broadband\u3cbr/\u3etime delay. Two methods of optical delay tuning are investigated:\u3cbr/\u3e1) optical wavelength and 2) thermo-optic delay tuning. The wavelength\u3cbr/\u3econtrolled tuning enables a large delay tuning range and\u3cbr/\u3ecan be done remotely from a distant location. The close to a linear\u3cbr/\u3ephase measurements can be used for full beam-scanning of radio\u3cbr/\u3esignals with frequencies in the 20 GHz band. The thermal control\u3cbr/\u3eresults in a 5 GHz RF delay bandwidth. A proof-of-concept 2 × 1\u3cbr/\u3ebeamforming is demonstrated in the 20 GHz band. The design presented\u3cbr/\u3ehere can be employed to realize multi-beams for multi-users\u3cbr/\u3eserviced by multiple satellites