Advanced Adaptive Photonic RF Filters with 80 Taps Based on an Integrated Optical Micro-Comb Source

TLDR

We demonstrate a photonic RF transversal filter using an integrated optical micro‑comb source that provides 80 evenly spaced lines across the C‑band with a record low free spectral range of 49 GHz. The filter employs both positive and negative taps generated by the micro‑comb, Gaussian apodization for out‑of‑band rejection up to 48.9 dB, and a tunable centre frequency with a widely adjustable 3‑dB bandwidth, enabling dynamically adjustable filter shapes. The 80‑tap configuration yields a QRF factor over four times higher than prior work, matches theoretical predictions, and offers broad bandwidth, high frequency selectivity, and reconfigurability, making it a cost‑effective solution for radar and communications systems.

Abstract

We demonstrate a photonic radio frequency (RF) transversal filter based on an integrated optical micro-comb source featuring a record low free spectral range of 49 GHz yielding 80 micro-comb lines across the C-band. This record-high number of taps, or wavelengths for the transversal filter results in significantly increased performance including a QRF factor more than four times higher than previous results. Further, by employing both positive and negative taps, an improved out-of-band rejection of up to 48.9 dB is demonstrated using Gaussian apodization, together with a tunable centre frequency covering the RF spectra range, with a widely tunable 3-dB bandwidth and versatile dynamically adjustable filter shapes. Our experimental results match well with theory, showing that our transversal filter is a competitive solution to implement advanced adaptive RF filters with broad operational bandwidths, high frequency selectivity, high reconfigurability, and potentially reduced cost and footprint. This approach is promising for applications in modern radar and communications systems.