J. J. Lee

Wide band bunny-ear radiating element

A low-cost wideband radiating element for EW (electronic warfare) and radar array antenna applications is reported. This printed end-fire bunny-ear element is fed by a balanced slot line, and it can operate over 0.5 to 18 GHz with very low loss in an isolated environment. The input transition, the feed line, and the launching section of this element are essentially TEM (transverse electromagnetic) structures. The element was scaled and used in an L-band array with 50% instantaneous bandwidth.<<ETX>>

A steerable leaky-wave antenna using a tunable impedance ground plane

A steerable leaky-wave antenna is built using a mechanically tunable impedance surface. A horizontally polarized antenna couples energy into leaky transverse electric waves on a tunable textured ground plane. By tuning the resonance frequency of the surface, the band structure is shifted in frequency, which changes the tangential wave vector of the leaky waves for a fixed frequency. This steers the elevation angle of the resulting radiated beam. This steerable leaky-wave antenna can scan over a range of 45/spl deg/ using a mechanical movement of about 1/500 wavelength.

Performance of an optically fed conformal array

The authors present an overview of the development work of a wideband photonic array antenna. They focus on the performance of a unique L-band (850-1400 MHz) 24/spl times/4 element conformal array, supported by a true-time-delay beamforming network. A 2-ns pulse was injected into the system and the round trip impulse response was measured to demonstrate the arrays 550 MHz (50%) instantaneous bandwidth.<<ETX>>

System design and performance of a wideband photonic array antenna

Presented in this paper is an overview of the development of a wideband photonic array antenna. The presentation will focus on the performance of a unique L-band 24 X 4 element conformal array, supported by a photonic true-time-delay beamforming network. A 2-ns pulse was injected into the system and the round trip impulse response was measured to demonstrate the arrays 550 MHz instantaneous bandwidth.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Photonics for phased-array antennas

In this paper, we discuss the applications and also several important system issues: insertion loss, noise figure, dynamic range and cost relating to photonics for wideband phased array antennas. This discussion is based on the work that we did on an L-band Optical Control of Phased Array Project funded by DARPA/Rome Lab. The antenna has been delivered to Rome Lab for further demonstration.

EHF Fiber Optic-Based Antenna Array

Lightwave circuits have a number of advantages over conventional metallic conductors for both analog and digital signal distributions in a phased array antenna. Potential architectures and system issues involved in implementing a fiber optic based EHF subarray will be discussed.

Microwave photonic applications of MEMS technology

We describe RF MEMS switches and their applications to tunable filters and switchable antenna elements. We describe different scenarios where RF photonic systems can benefit from RF MEMS device development.

Optoelectronic Switching for Radar Steering

We describe the use of fiber delay lines for radar steering and the implementation of laser switching to achieve true time delay steering of a dual band phased array transmitter.

Photonic RF Mixing Food For Multibeam Arrays

A number of optical beamforming techniques are currently being pursued which make use of low loss, low dispersion, single mode fiber to construct wide-band feed networks for phased array antennas [ l ] . The photonic RF mixing feed is one promising approach which uses the feed network itself to produce phased signals required for beam scanning. This method uses two fiber manifold networks to produce and to distribute two sets of RF modulated optical control signals to the antenna elements. The control signals are subsequently photodetected, and then mixed and filtered in the RF domain to provide each element with the proper output frequency and phase for beam scanning. As was shown in the initial L-band demonstration of this technique (21, the inter-element phase varies linearly with the sum of the two control frequencies and the output frequency is equal to their difference. Subsequent investigations of this technique 13-51 found similar single-beam phase behavior.

Silica-wavequide optical time-shift network for steering a 96-element L-Band conformal array

We report the demonstration of a 4-bit optoelectronic-switched silica-waveguide time-delay network. Targeted for insertion into a 96-element L-band conformal array, the optical time- shifter provides 16 programmable time-delays in steps of 0.248 nsec. By characterizing its RF insertion phase and synthesized pulse response, we verified that the relative time-delays generated by the waveguides were within 15 psec of their designed value. The antenna patterns obtained with the waveguide-module steering the central column of the phased array demonstrated greater than 50% instantaneous bandwidth for scan angles as wide as +/- 60 degrees.