Bruce A. Black

Teaching DSP First with LabVIEW

The proponents of graphical programming (that is using graphics to program a computer, not programming a computer to do graphics) claim graphical programming is better than text-based programming; however text-based programmers far out number graphics-based programmers. This paper describes the preliminary developments of comparing the use of LabVIEW (a graphical programming language) to MATLAB (a text-based language) in teaching discrete-time signal processing (DSP). This paper presents the results of using both methods in a junior-level introduction to DSP class. The students who enter this class have had a course in continuous-time signals and systems but no DSP theory background. Several quarters of concept inventory data have been collected on the MATLAB version of the class. The same inventory was used with the LabVIEW version of the class and the results compared

Component-level simulation of optical beamforming systems

Binary fiber Bragg grating arrays are capable of providing a true-time-delay capability needed for beamforming. The grating arrays consists of a series of fibers connected by circulators and switches. Each fiber contains tow or more fiber Bragg gratings on a fiber may become smaller than the grating length. Alterative architectures that use ternary switching have been proposed that show promise in reducing the constraints on grating spacing, but require carful control of grating position. Component-level simulation was carried out to compare alterative architectures and to evaluate effects of tolerances in grating placement, component imperfections, connector losses, and similar impairments whose overall consequences are difficult to predict. Fiber Bragg gratings, channel balancers, switches, and other beamfomer components were modeled. Beamforming arrays were simulated that focus tow antennas, and allow beamscanning over a +/- 70 degrees angle in thirty-two discrete steps. The baseband bandwidth was assumed to exceed 1 GHz. Binary and ternary array structures were compared. The PHOTOSS photonics system simulator provided the simulation engine. Beam patterns were calculated for a beam sweeping past a broadside target, and for a beam sweeping past targets at other angles. Results of simulation have been used to inform decisions as physical systems are realized.

A ternary programmable dispersion matrix for receive/transmit optical beamforming

We present a new architecture for a programmable disperions matrix for optical beamforming. A 2-channel prototype is constructed to demonstrate beam steering for angles of ±70° in the receive/transmit mode in RF0.1-1 GHz frequency range.

Space-time delta-sigma modulation for reception of multiple simultaneous independent RF beams

In this paper we introduce and analyze a multiple-RF-beam beamformer in receive mode utilizing the principle of space-time delta-sigma modulation. This principle is based on sampling input signals in both time and space and converting the sampled signals into a digital format by delta-sigma conversion. Noise shaping is achieved in 2D frequency domain. We show that the modulator can receive signals of narrow and wide bandwidths with steering capability, can receive multiple beams, and establish tradeoffs between sampling in time and in space. The ability of the modulator to trade off between time and space provides an effective way to sample high frequency RF signals without down conversion. In addition, a space-time delta-sigma modulator has better performance than a solely temporal delta-sigma modulator (for the same filter order), as is typically used in communication systems to digitize the down-converted analog signals.

Two-beam two-channel optical T/R beamformer using ternary programmable dispersion matrix

A single two-channel photonic beamformer based on a ternary programmable dispersion matrix is proposed and demonstrated to simultaneously process two independent RF beams. Beam patterns for two RF beams and various target positions are presented.

Fiber-Bragg-grating-based four-bit optical beamformer

In this paper we implement and characterize a two-channel optical programmable beamformer. The system is designed to achieve four-bit resolution. The architecture of the programmable dispersion matrix is based on an array of four delay-lines each having two spliced fiber Bragg gratings. We have experimentally investigated the optical signal processing performance of the optical beamformer in receive and transmit modes. Beampatterns for RF range 40 - 200 MHz are presented along with the theoretical calculations. The main lobe of the beampattern is shown to be independent of frequency for several target positions thus demonstrating a “squint-free” characteristic of this optical processor.

Undergraduate summer research in RF photonics

Over the past four years, 2000-2003, undergraduates have participated in summer research at Rose-Hulman Institute of Technology (RHIT) carrying out a wide range of optics projects.

All optical receive beamformer at 1310 nm

We demonstrate an optical two-channel receive beamformer at 1310 nm using fiber Bragg grating arrays for producing true time delay. The antenna beam patterns are measured for broadside targets at several RF frequencies ranging from 40 MHz to 1 GHz. These results compare favorably with theoretical calculations.

Single-sideband suppressed-carrier rf processing

We present a simple scheme for implementation of optical single sideband suppressed carrier (OSSB-SC) modulation based on the use of standard MZM and passive fiber optic components. The function of the proposed modulator is also theoretically predicted. A Sagnac interferometer structure is used for sideband suppression. The light propagating in one direction is orthogonally linearly polarized to the oppositely propagating light. The orthogonal polarization is implemented by a non-reciprocal optical element. The optical carrier is attenuated by appropriately setting the Mach-Zender Modulator (MZM) at quadrature bias point. We will experimentally demonstrate sideband suppression and carrier attenuation up to 28 dB by using all commercially available components.

Paradigm shifts in enginering education: The influence of computers and communications

The authors report on the process of planning and executing a study on the influence of computer and telecommunications technology on engineering education. The study reported is a two-year study, designed to determine through the collection of knowledge, by survey and focus group discussions, what target areas for change in engineering education appear useful for future development. Preliminary results of the study are presented.<<ETX>>