Edward N. Toughlian

Photonic beamformer for phased array antennas using a fiber grating prism

This letter presents, for the first time, measured data on a Bragg reflection grating based fiber-optic prism true time delay processor for transmit/receive phased array beamforming. Measurements taken over a 3.5-GHz bandwidth demonstrates high resolution beamsteering and highly linear low-noise phase data. The system takes maximum advantage of component reuse and fully integrates the transmit and receive modes in one efficient hardware compressive topology.

Variable time-delay system for broadband phased array and other transversal filtering applications

A variable time delay system for broadband phased array receive and other transversal filtering applications is disclosed and employs a segmented mirror device (SMD) and a linear fiber array to realize a quantized variable delay line. The use of the SMD allows for extremely high packing density without the large losses usually associated with switched fiber schemes.

A photonic implementation of a wide-band nulling system for phased arrays

This letter presents a novel architecture for independently steering broad-band nulls for phased array antennas. Measurements taken over a ten percent fractional bandwidth on a three-element proof-of-concept system shows a null depth of better than 40-dB uniform across the entire band in this laboratory setup. The architecture presented is best suited for small antenna array applications, for example self-guided airborne munitions. In a fully integrated, optimized system, null depths of 50-70 dB or greater across a multigigahertz bandwidth are anticipated and the critical factors, which influence this performance, are examined.

Photonic Architectures for Broadband Adaptive Nulling with Linear and Conformal Phased Array Antennas

This paper presents several photonic architectures for independently steering multiple broadband nulls for linear and conformal phased array antennas. Analytic expres sions that quantify bandwidth requirements are developed and both experimental and simulation results which demonstrate the antenna system performance are presented. In a fully integrated, optimized system, null depths in excess of 50 dB across a multigigahertz bandwidth are anticipated and the critical factors that influence this performance are examined.This paper presents several photonic architectures for independently steering multiple broadband nulls for linear and conformal phased array antennas. Analytic expres sions that quantify bandwidth requirements are developed and both experimental and simulation results which demonstrate the antenna system performance are presented. In a fully integrated, optimized system, null depths in excess of 50 dB across a multigigahertz bandwidth are anticipated and the critical factors that influence this performance are examined.

A photonic wideband analog-to-digital converter

This paper provides a comprehensive understanding of a novel photonic high-speed analog-to-digital converter (ADC) approach and its anticipated performance. Compelling analytic models, experimental data, and simulation results show that the system will achieve the goal of developing an ADC with a resolution on the order of 12 bits and with conversion speeds in excess of 10 GS/s.

A photonic wide-band analog to digital converter

We describe how a tunable laser and common photonic components can perform the process of analog-to-digital conversion. The all-optical processing yields conversion rates orders of magnitude faster than the fastest electronic processor.

True-time-delay photonic beamformer for an L-band phased array radar

The problem of obtaining a true-time-delay photonic beamformer has recently been a topic of great interest. Many interesting and novel approaches to this problem have been studied. This paper examines the design, construction, and testing of a dynamic optical processor for the control of a 20-element phased array antenna operating at L-band (1.2-1.4 GHz). The approach taken here has several distinct advantages. The actual optical control is accomplished with a class of spatial light modulator known as a segmented mirror device (SMD). This allows for the possibility of controlling an extremely large number (tens of thousands) of antenna elements using integrated circuit technology. The SMD technology is driven by the HDTV and laser printer markets so ultimate cost reduction as well as technological improvements are expected. Optical splitting is efficiently accomplished using a diffractive optical element. This again has the potential for use in antenna array systems with a large number of radiating elements. The actual time delay is achieved using a single acousto-optic device for all the array elements. Acousto-optic device technologies offer sufficient delay as needed for a time steered array. The topological configuration is an optical heterodyne system, hence high, potentially millimeter wave center frequencies are possible by mixing two lasers of slightly differing frequencies. Finally, the entire system is spatially integrated into a 3D glass substrate. The integrated system provides the ruggedness needed in most applications and essentially eliminates the drift problems associated with free space optical systems. Though the system is presently being configured as a beamformer, it has the ability to operate as a general photonic signal processing element in an adaptive (reconfigurable) transversal frequency filter configuration. Such systems are widely applicable in jammer/noise canceling systems, broadband ISDN, and for spread spectrum secure communications. This paper also serves as an update of work-in-progress at the Rome Laboratory Photonics Center Optical Beamforming Lab. The multi-faceted aspects of the design and construction of this state-of-the-art beamforming project will be discussed. Experimental results which demonstrate the performance of the system to-date with regard to both maximum delay and resolution over a broad bandwidth are presented.

Variable time delay for RF/microwave signal processing

This paper addresses the problem of dynamic optical processing for the control of phased array antennas. The significant result presented is the demonstration of a continuously variable photonic RF/microwave delay line. It is shown that by applying spatial frequency dependent optical phase compensation in an optical heterodyne process, variable RF delay can be achieved over a prescribed frequency band. Experimental results which demonstrate the performance of the delay line with regard to both maximum delay and resolution over a broad bandwidth are presented. Additionally, a spatially integrated optical system is proposed for control of phased array antennas. This approach uses a class of spatial light modulator known as a deformable mirror device and leads to a steerable arbitrary antenna radiation pattern of the true time delay type. Also considered is the ability to utilize the delay line as a general photonic signal processing element in an adaptive (reconfigurable) transversal frequency filter configuration.

A photonic true time delay processor for Global Positioning System (GPS) null steering

This paper presents a novel architecture for independently steering broadband nulls for phased array antennas. Measurements taken over a ten percent fractional bandwidth on a three-element proof-of-concept system shows a null depth of better than 40 dB uniform across the entire band in this laboratory setup. The architecture presented is best suited for small antenna array applications, for example GPS guided airborne munitions. In a fully integrated, optimized system, null depths of 50-70 dB or greater across a multi-gigahertz bandwidth are anticipated and the critical factors, which influence this performance, are examined.

Fiber-optic-based null steering for conformal array antennas

This paper presents a photonic architecture for independently steering the broadband nulls of linear and conformal phased array antennas. Analytic expressions quantifying bandwidth requirements are developed and simulation results demonstrating array performance are presented.