Design and Simulation of a True-Time Delay Silicon Photonics Network for Beam Forming Applications

Abstract

Microwave photonics (MWP) combines the superior capacity of radio-frequency (RF) signals to travel through the atmosphere, and the high speeds and increased bandwidths of optical processing. Today, thanks to the rapid development of silicon photonics (SiPh), MWP can now fully leverage the scalability and power, size, and cost efficiencies of CMOS-enabled integrated technology; both in the electrical and optical domains. With the benefits of integrated electrical circuits (IC) and SiPh integrated photonic circuits (PIC), MWP can now address the stringent performance requirements of applications in modern telecommunications (telecom) for 5G and satellite networks. Beam forming is of particular interest, being one of the first major applications of MWP. True-time delay (TTD) optical beam forming networks (OBFN) are a specific MWP-enabled solution. In this thesis we discuss the fabrication, simulation, modelling, design, and characterization of SiPh components for a proposed 1×8, 8-bit discrete TTD OBFN architecture. We use the acquired SiPh device characteristics to create compact model representations for an end-to-end, Matlab-implemented simulation of the proposed OBFN. Details on the amplitude-modulated input signal modelling, digital output signal processing, linear antenna array field pattern modelling, and the OBFN control algorithm are discussed. A nominal operation study was conducted by testing beam steering angles of 0◦, 45◦ and 60◦ and 5 GHz 3 dB-bandwidth Gaussian pulse test signals with 18 GHz and 27 GHz centre frequencies. While TTD requirements for ±60◦-beam steering were achieved with minimal field pattern distortion, the estimated signal integrity figure of merit indicates that nominal device operation should not exceed more than ±45◦. Operation below the lower limit of the K band (18 GHz to 27 GHz) is recommended before optimization of the thermal-phase shifter (TPS) electrical input to improve the extinction ration (ER) characteristics of the device is conducted. Simulation runtime remains below 1 minute for all of the nominal operation test configurations.