Henry Zmuda

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.

Multifrequency Microwave-Induced Thermal Acoustic Imaging for Breast Cancer Detection

Microwave-induced thermal acoustic imaging (TAI) is a promising early breast cancer detection technique, which combines the advantages of microwave stimulation and ultrasound imaging and offers a high imaging contrast, as well as high spatial resolution at the same time. A new multifrequency microwave-induced thermal acoustic imaging scheme for early breast cancer detection is proposed in this paper. Significantly more information about the human breast can be gathered using multiple frequency microwave stimulation. A multifrequency adaptive and robust technique (MART) is presented for image formation. Due to its data-adaptive nature, MART can achieve better resolution and better interference rejection capability than its data-independent counterparts, such as the delay-and-sum method. The effectiveness of this procedure is shown by several numerical examples based on 2-D breast models. The finite-difference time-domain method is used to simulate the electromagnetic field distribution, the absorbed microwave energy density, and the thermal acoustic field in the breast model.

A New FDTD Formulation for Wave Propagation in Biological Media With Cole–Cole Model

The finite-difference time-domain (FDTD) method has been widely used to simulate the electromagnetic wave propagation in biological tissues. The Cole-Cole model is a formulation which can describe many types of biological tissues accurately over a very wide frequency band. However, the implementation of the Cole-Cole model using the FDTD method is difficult because of the fractional order differentiators in the model. In this letter, a new FDTD formulation is presented for the modeling of electromagnetic wave propagation in dispersive biological tissues with the Cole-Cole model. The Z-transform is used to represent the frequency dependent dielectric properties. The fractional order differentiators in the Cole-Cole model is approximated by a polynomial. The coefficients of the polynomial are found using a least-squares fitting method

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.

Wavelength-based analog-to-digital conversion

This paper provides a comprehensive understanding of a tunable wavelength-based photonic high-speed analog-to- digital converter (ADC) approach and its anticipated performance. Analytic models, experimental data, and simulation results will provide the fundamental limits on the expected conversion speed and bit resolution. A thorough in situ study of the photonic signal conversion system under simulated space radiation conditions is required to precisely determine its performance in either a natural or man-made space environment. Although this study has not yet been performed on the entire system, preliminary performance predictions will be made based on previously published studies on the individual components within the system. The photonic components of particular interest that will be discussed in the context of radiation hardness includes the edge emitting laser diode with a MQW tuning element, the processor filters, the delay equalizers and the photodetectors.

Broadband nulling for conformal phased array antennas using photonic processing

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.

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.

Hardware implementation of wideband time domain Robust Capon Beamforming

Capon Beamforming algorithm is an optimal spatial filtering algorithm used in various signal processing applications where excellent interference rejection performance is required, such as Radar and Sonar systems, Smart Antenna systems for wireless communications. Its lack of robustness, however, means that it is vulnerable to array calibration errors and other model errors. To overcome this problem, numerous Robust Capon beamforming algorithms have been proposed, which are much more promising for practical applications. In this paper, an FPGA implementation of a Robust Capon Beamforming algorithm is investigated and presented, which deals with wideband real-valued signals in time domain. This realization takes an array input with 8 channels, computes the adaptive weight vectors for beamforming with an 18 bit fixed-point representation and runs at an 80 MHz clock on Xilinx V4 FPGA. The outcomes will be applied to a medical imaging project.