William S. McCormick

Design and performance evaluation of a 2.5-GSPS digital receiver

Todays very deep submicron IC technology enables high-performance analog and digital applications to be integrated on a single piece of silicon. For this effort, a design of 2.5 giga-sample per second (GSPS) receiver-on-a-chip (ROC) is presented. For our design, we take advantage of a compensation technique to reduce spurs and improve instantaneous dynamic range. A major goal is to produce a low-cost, small, and lightweight, and low-power ROC. Our design will cover a 1-GHz bandwidth (125 - 1125 MHz), and it will correctly process two simultaneous signals by detecting their frequency, pulsewidth (PW), and time of arrival (TOA). The single or dual signal, spur-free dynamic ranges and two signal instantaneous dynamic ranges of our design are high. The minimum frequency separation of two signals is 10 MHz (one channel width), and the maximum amplitude separation (dynamic range) of two signals is 18 dB with the second signal false alarm less than 1%.

A noise insensitive solution to an ambiguity problem in spectral estimation

The instantaneous frequency measurement (IFM) receiver is capable of measuring the center frequency of single frequency pulses over a wide range (bandwidth) of center frequencies. Because of various constraints, the frequency resolution requirement results in long correlator delay times that reduce the single correlator bandwidth. A large bandwidth can be achieved only if two or more correlators are used. The problem of estimating frequency is then reduced to the simultaneous congruence problem of number theory. A design procedure is presented for solving the congruence problem for a given amount of noise protection, a stated frequency resolution, a minimum bandwidth, and a fixed level of precision (bits) in the IFM receiver. >

Resolution of a 2/spl pi/ ambiguity problem in multiple frequency spectral estimation

An algorithm is proposed to resolve a fundamental 2/spl pi/ ambiguity problem occurring in multiple frequency spectral estimation. Given M frequencies f/sub m/, and I separate frequency estimators with unambiguous bandwidths F/sub i/, the ambiguity problem can be stated as solving for the fm, given the estimator outputs, /spl alphasub mi/, (1/spl les/m/spl les/M;1/spl les/i/spl les/I) where f/sub m/=/spl alphasub mi/+K/sub mi/F/sub i/ and K/sub mi/ is some integer. The proposed algorithm exhaustively resolves all possible /spl alphasub mi/ groupings into single frequency values using a noise insensitive technique that exchanges system bandwidth for noise protection. The correct multiple frequencies are then defined as the single frequencies that repeat a specified number of times. A complete analysis is included. >

Efficient parallel rooting of complex polynomials on the unit circle

An efficient method is presented for rooting complex polynomial equations of any order where the root space is restricted to the unit circle. The method restates the evaluation of polynomials as a recursive algorithm involving only additions. By means of the bilinear transformation, the straight line, uniformly spaced, recursive polynomials evaluation method of A.H. Nuttall (1987) is extended to the unit circle where the root positions are determined by thresholding. General coefficient transformations are provided along with a comparison to the Horner method. >

Two frequency estimation without multiplication

A computationally simple algorithm that measures one or two frequencies using lookup tables and simple adders is presented. The algorithm is based on a real-time processing of instantaneous frequency and envelope. The algorithm provides a maximum-likelihood estimate in the single-frequency case. Oversampling is required and the algorithm cannot estimate three or more frequencies. A complete error analysis is presented along with simulation results

2.5 GSPS/1 GHz wide band digital receiver

Todays very deep submicron IC technology enables high performance analog and digital applications to be integrated on a single IC chip. For this effort, a design of 2.5 giga-sample per second (GSPS) electronic warfare (EW) receiver-on-a-chip (ROC) is presented. For our design, we take advantage of a super-resolution technique to reduce sidelobes and spurs for improving instantaneous dynamic range. A major goal is to produce a low cost, small and lightweight, and low power EW ROC. Our design covers a 1 GHz bandwidth (125 MHz - 1125 MHz), and it correctly processes two simultaneous signals by detecting their frequency, pulse width (PW), and time of arrival (TOA). The single or dual signal, spur free dynamic ranges and two signal instantaneous dynamic ranges of our design are high. The minimum frequency separation of two signals is 10 MHz (one channel width), the maximum amplitude separation of two signals is 18 dB, and the second signal false alarm is less than 1%.

HIGH-BANDWIDTH LASER-PULSE GENERATOR USING CONTINUOUS-WAVE LASERS

A laser-pulse generator for the transfer of continous-wave (cw) absolute radiometric calibrations to high-speed pulse photodetectors is described. The cw input lasers are modulated by a spinning polygon mirror in a ring cavity to produce high-speed, constant-amplitude, constant-shape laser pulses. Constantamplitude outputs range temporally from cw to 15-ns full-width at half-maximum (FWHM) Gaussian pulses. An all-reflective optical design permits operation of the device from the visible to the far-infrared spectral regions. Design and performance estimates for the pulse generator as well as experimental verification are presented.

Hyperspectral exploitation with plant sentinels

The primary goal of this paper is to develop Hyperspectral algorithms for early detection of a readout system used in conjunction with plants designed to de-green or discolor after detection of explosives, harmful chemicals, and environmental pollutants. Work in progress is aimed to develop a new class of biosensors or Plant Sentinels that can serve as inexpensive plant-based biological early-warning systems capable of detecting substances that are harmful to human or the environment [LoHe03]. The de-greening circuits in the laboratory plant, Arabidopsis, have been shown to induce rapid chlorophyll loss, thereby change color under the influence of synthetic estrogens. However, as of now, the bio de-greening phenomenon is detectable by human eyes or with a system (chlorophyll fluorescence) that works best in laboratory conditions. In order to make the plant sentinel system practically viable, we have developed automated monitoring scheme for early detection of the de-greening phenomenon. The automated detection capability would lead to practical applicability and wider usage. This paper presents novel and effective HSI-based algorithms for early detection of de-greening of plants and vegetation due to explosives or chemical agents. The image processing based automated degreening detector, presented in this paper will be capable of 24/7 monitoring of the plant sentinels and to detect minutest possible discoloration of the plant-sensors to serve as an early-warning system. We also present preliminary results on estimating the length of time that the explosive or chemical agent has been present.

The Estimation of Induced-Voltage Peak Magnitude and Energy Level Under LTA/EMP Excitation of Low-Loss Aircraft Cabling

The important vulnerability parameters of peak voltage transient magnitude and voltage transient energy are estimated for the LTA/EMP induction problem. Using basic linear system theory, straightforward expressions are derived to estimate these two survivability parameters. The derived model is quite general including cable characteristics, varying terminating impedances , and varying points of cable excitation. Using the developed model, a comparison of the LTA and EMP cases is made. An iliustrative example involving the yaw-damper circuit of the USAF f-l11 is also included.

Error sensitivity analysis of a bandwidth expansion technique in spectral analysis

The paper presents an error sensitivity analysis of a bandwidth expansion technique in spectral analysis based on a noise-protected version of the Chinese Remainder Theorem. Necessary and sufficient conditions on remainder percent error and sampling period/time delay error are derived using various properties from number theory. The developed design criteria have special relevance to real-time, wide bandwidth spectral estimation in the EW passive receiver.