| PhD Viva

Name of the Speaker: Mr. Ashitosh Velamuri (EE18D042)
Guide: Dr. Bijoy Krishna Das
Online meeting link: https://meet.google.com/cas-fdzw-oew
Date/Time: 9th May 2025 (Friday), 3:30 PM
Title: Programmable Silicon Photonic Microwave Filters using Microring Resonators

Abstract :

The futuristic 5G/6G communication and RADAR signal processing systems operating beyond X-band (>10 GHz) demand scalable microwave photonic integrated circuits for re-configurable operations. CMOS-compatible silicon photonics technology is being studied intensively for programmable optical signal processors (OSP) for high-frequency microwave to mm-wave applications. The bandpass filter is an essential microwave receiver architecture block to separate the signal of interest from the noise and eliminate cross-talks. The microring resonator (MRR) is a popular device for designing an efficient OSP for RF photonic filters. One significant challenge is implementing bandpass programmable microwave photonic filters with symmetrical out-of-band rejection around the central carrier frequency.

In this talk, I will discuss about the demonstration of microwave photonic filters (MWPF) with MRRs programmed to operate in different configurations. In the first part, I will present the proof-of-concept experimental results of the MWPF with the novel OSP design (based on cascaded MRR) fabricated in-house, with tunable frequency up to 8 GHz (theoretical limit: 60 GHz), tunable bandwidth 0.84 - 1.8 GHz, symmetric out-of-band rejection > 20 dB, along with its limitations and improvement scopes.

Next, I will discuss the programmable photonic integrated circuit comprising 14 Mach-Zehnder interferometers designed into a square mesh architecture to demonstrate a silicon photonic multi-band MWPF with tunable bandwidths and re-configurable number of passbands. The mesh architecture is programmed to realize MWPF with two, three and four bands. Among these, I will present a thorough investigation of the two-band filter response where the bandwidth of both the filter bands were tuned over the extensive range of 1.6 GHz to 12.7 GHz. Following, I will discuss the performance of such MWPF in a radio-over-fiber communication network using the X-band receiver link that was set up in our lab. With an optimized set of operating parameters of the programmable microwave filter, we could achieve a bit-error-rate as low as ~ 10-20 for a fiber-optic link length of 400 m (@ 100 Mbps).

Finally, I will discuss the experimental results to realize an integrated two-band MWPF with an on-chip modulator and detector. In the experiments, both passbands' central frequency could be tuned in the 5 - 18 GHz range and 38.5 - 25.5 GHz, respectively, with a symmetric out-of-band rejection > 20 dB. For the tuned frequency range, the bandwidth of the MWPF could be tuned from 1 - 6 GHz in our experimental setup.