The influence of chromatic fiber-dispersion on the transmission distance of fiber-optic microwave and millimeter-wave links is analyzed and discussed in this paper. It is shown that dispersion significantly limits the transmission distance in intensity modulated direct detection links operating in the above 20 GHz frequency region by inducing a carrier to noise penalty on the transmitted signal. At 60 GHz, a 1 dB penalty is induced after less than 500 m transmission over standard single-mode fiber with a dispersion of 17 ps/km/spl middot/nm and the signal is completely extinct after 1 km. In remote heterodyne detection links, the dispersion induces both a carrier to noise penalty and a phase noise increase on the transmitted signal. It is shown, however, that the induced carrier to noise penalty is insignificant. At 60 GHz, the induced penalty is less than 0.3 dB after 100 km transmission. The phase noise increase proves more dominant. At 60 GHz, a 150 Mbit/s QPSK signal is limited to around 10 km of transmission.

Chromatic dispersion in fiber-optic microwave and millimeter-wave links

The concept of true-time-delay steering for phased array antennas and its advantage over phase shifters in broadband applications are described with particular emphasis on the potential advantages offered by fiber-optic delay lines. The system architecture of the phased array antenna and the design and performance of the fiber-optic time-shifter networks in the antenna are described. The radiation patterns of the phased array antenna at L and X bands are presented. Using semiconductor laser switching to implement the delay times, the absence of beam squint in the antenna pattern and its frequency was switched from L to X band is demonstrated. >

The first demonstration of an optically steered microwave phased array antenna using true-time-delay

Experimental results for an optical-control technique for implementing a true time-delay function for array antennas are reported. 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. >

Fiber-optic prism true time-delay antenna feed

Demonstrated is the optical generation and transmission of a microwave signal by the mixing of two high-quality optical signals from diode-laser-pumped Nd:YAG ring lasers, resulting in a narrow microwave line width (less than 5 kHz line width at 3 dB and less than -115 dBc/Hz at 300 kHz from line center) and broad microwave tunability (DC to 52 GHz). A III-V semiconductor waveguide with a doping superlattice active region is used to optoelectronically provide 20 dB of amplitude control and up to 5 pi of phase shift. This approach can be straightforwardly implemented using integrated optics and fiberoptic links for control of phased-array antenna elements. >

Optical generation, distribution, and control of microwaves using laser heterodyne

A photonic in-phase/quadrature (I-Q) RF phase shifter utilizing two integrated optic Mach-Zehnder modulators has been tested. This phase shifter demonstrates the capability of 360 degrees phase control, >

A photonic integrated-optic RF phase shifter for phased array antenna beam-forming applications

Microwave signals for all array elements in a phared array microwave antenna are simultaneously generated by spatial sampling of a moving sinusoidal interference pattern formed between two frequency-offset injection-locked laser diodes. The offset and radar frequency of 3.2 GHz were generated by a Bragg cell. A nearly distortionless antenna beam pattern and 180° steering are demonstrated in a linear seven-element array.

Optical feed for a phased array microwave antenna

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Optical feed for a phased array microwave antenna