Abstract

Photonic true-time delay (TTD) beamforming^1–5 has been considered a promising technique for future wideband phased array antenna systems and has been intensively studied recently. An efficient way to achieve TTD beamforming is to use a fiber-grating prism. There are two types of fiber-grating prisms: the one uses discrete fiber Bragg gratings (FBGs)¹ and the one uses a chirped grating.⁴ Discrete FBG-based TTD system can usually work at microwave frequencies less than 3 GHz⁴ with discrete beam scanning. To achieve continuous beam steering at higher microwave frequencies, chirped grating based TTD beamforming system is usually used.⁵ The diffi-culty employing chirped grating based system is that one needs to provide a multi-wavelength source in which the wavelengths should be tuned with an equally increased or decreased wavelength spacing. To achieve this, multiple tunable laser sources with the wavelengths controlled by a programmable wavelength controller should be used. Obviously, this makes the whole TTD system bulky and expensive. To solve this problem, in this paper we propose to use a new multiwave-length tunable laser source that can generate mul-tiwavelength lasing with equally increased or decreased wavelength spacing.

© 2002 Optical Society of America