Microcomb-based true-time-delay network for microwave beamforming with arbitrary beam pattern control

TL;DR

This paper presents a novel microcomb-based photonic true-time-delay network for microwave beamforming, enabling arbitrary beam pattern control with improved bandwidth and scalability for phased array antennas.

Contribution

The authors introduce a microcomb-based TTD beamforming network with a new spectral shaping method, supporting large-scale PAAs and arbitrary beam patterns.

Findings

Supports 21-element PAA in 8-20 GHz range

Achieves beam steering of ±60.2°

Demonstrates arbitrary beam pattern control

Abstract

Microwave phased array antennas (PAAs) are very attractive to defense applications and high-speed wireless communications for their abilities of fast beam scanning and complex beam pattern control. However, traditional PAAs based on phase shifters suffer from the beam-squint problem and have limited bandwidths. True-time-delay (TTD) beamforming based on low-loss photonic delay lines can solve this problem. But it is still quite challenging to build large-scale photonic TTD beamformers due to their high hardware complexity. In this paper, we demonstrate a photonic TTD beamforming network based on a miniature microresonator frequency comb (microcomb) source and dispersive time delay. A method incorporating optical phase modulation and programmable spectral shaping is proposed for positive and negative apodization weighting to achieve arbitrary microwave beam pattern control. The experimentally demonstrated TTD beamforming network can support a PAA with 21 elements. The microwave frequency range is $\mathbf{8\sim20\ {GHz}}$, and the beam scanning range is $\mathbf{\pm 60.2^\circ}$. Detailed measurements of the microwave amplitudes and phases are performed. The beamforming performances of Gaussian, rectangular beams and beam notch steering are evaluated through simulations by assuming a uniform radiating antenna array. The scheme can potentially support larger PAAs with hundreds of elements by increasing the number of comb lines with broadband microcomb generation.