Fiber-optic prism true time-delay antenna feed

Abstract

We describe and present experimental results for a novel and elegant optical-control technique for implementing a true time-delay function for array antennas. A microwave signal is transmitted on a wavelength-tunable optical carrier through a fiber-optic prism-a set of nominally equal-delay fibers with differing net dispersion-to photodetectors that feed each antenna element. The relative interelement time-delay (beam angle) adjustment is accomplished by tuning the optical carrier wavelength. Measured antenna patterns of a two-element array clearly demonstrate beam steering and true time-delay operation over a two-octave bandwidth of 2-8 GHz.

Optically beamformed beam-switched adaptive antennas for fixed and mobile broad-band wireless access networks

“…Therefore, the optical signal is routed through different aggregated lengths of fiber depending on the bias voltages of the switches, with up to eight different possible combinations (3 b wavelength-dependent dispersive behavior of the optical fiber, each modulated optical carrier suffers a different time delay, depending on the selected path, given by (1) where is the dispersion parameter of the fiber, is the length of the optical path, and is the wavelength spacing between optical carriers. This relative time delay between optical carriers corresponds to different beam-steering angles according to (2) After the wavelenth-division multiplexing (WDM) optical signal is delayed and amplified using an erbium-doped fiber amplifier (EDFA), each optical carrier is demultiplexed and launched to a high-speed photodetector (PD). After amplification using an millimeter-wave amplifier, the four modulated electrical carriers are radiated using a four-element patch antenna.…”

“…After amplification using an millimeter-wave amplifier, the four modulated electrical carriers are radiated using a four-element patch antenna. The phase front of the radiated signal can be varied among eight different positions depending on the chosen combination of switching voltages (i.e., total delays), according to (2).…”

Wide-band RF photonic second order vector sum phase-shifter

“…Many TTD phase shifters have been proposed over the years. These include switched delay line [2], dispersive fiber prism [3] and fiber grating devices [4]. Though promising, these phase shifters are complex and usually expensive to implement.…”

Performance evaluation of optical beamforming-based wideband antenna array (Invited Paper)

“…Thanks to the intrinsic advantage of large instantaneous bandwidth brought by optical technologies, broadband and large-range true time delay (TTD) can be easily implemented in the optical domain [8][9][10][11][12] . Thus, complex waveforms with larger instantaneous bandwidth can be applied, which enables distinctive features such as better resolution for ranging [13] , larger suppression of grating lobes [14,15] , and higher speed in wireless communications [16,17] .…”