Technical Session 3

Technical Session 3: Antenna and Component Technologies

Cochair: Dr. Jeff Nemit, ITT Gilfillan
Cochair: Mr. Jim Fritsch, Northrop Grumman

Tuesday Afternoon April 23, 2002

3.1:: Nonuniform Sampling Reconstruction Applied to Sparse Array Beamforming
3.2:: Model-Based Adaptive Detection and DOA Estimation Using Separated Sub-Arrays
3.3:: Using a Wavelet Basis for a Spectrally Tunable Phased Array
3.4:: Improvements in Radar Transmitter Performance and Reliability Using High-Voltage Solid- State Modulators and Power Supplies
3.5:: A High Sensitive Receiver for Baseband Pulse Microwave Radar Sensor Using Hybrid Technology

3.1 Nonuniform Sampling Reconstruction Applied to Sparse Array Beamforming By: Scott D. Berger Air Force Research Laboratory	Abstract: In this paper, we investigate the application of non-uniform sampling reconstruction to sparse array beamforming to gain insight into its potential and identify additional challenges. The central concept of the nonuniform sampling beamformer is to use the nonuniform samples to reconstruct the samples of a uniform array with the same sampling density as the nonuniform array and then perform conventional beamforming. Our results show the potential of replacing elements in a sparse uniform linear array with uniform linear subarrays and using a nonuniform sampling reconstruction formula in improving the near-in (bandwidth supported by the array sampling density) grating lobes performance. However, this improved performance comes at the expense of significantly worsened performance in the out-of-band region (beyond the near-in grating lobe region). Additionally, the performance of the nonuniform sampling beamformer is extremely sensitive to phase noise. Although increasing the sampling density improved performance, the out-of-band performance and sensitivity are still areas of concern for most sparse arrays.
3.2 Model-Based Adaptive Detection and DOA Estimation Using Separated Sub-Arrays By: Christer Engdahl and Per Sunnergren Ericsson Microwave Systems AB	Abstract: The potential performance of adaptive detection and Direction-Of-Arrival (DOA) estimation using a certain class of sparse linear arrays, characterized by two widely separated sub-arrays, in combination with model- based techniques, is investigated. With this array structure, a large baseline is obtained with a limited amount of hardware. It is found that the very narrow main-lobe obtained by separating the sub-arrays can be utilized to obtain accurate DOA estimates, high angular resolution, and good detection performance even in close vicinity of a localized interference source. However, the presence of grating lobes deteriorates the performance at low SNR and also when the angular separation between two targets, or between a target and an interfering source, corresponds to an integer times the distance between the grating lobes.
3.3 Using a Wavelet Basis for a Spectrally Tunable Phased Array By: Robert J. Bonneau and Michael C. Wicks Air Force Research Laboratory	Abstract: Conventional phased array radars traditionally use digital filters that are adaptive in frequency on receive and use a fixed transmit pattern to illuminate their targets. Unfortunately such an approach does not take into consideration the spatial diversity of targets and interference sources that the phased array observes as it is electronically pointed throughout its search area. We propose a methodology that uses a wavelet filter bank to selectively transmit and receive radiation that is directionally dependent on the phased array's pointing direction. Such an approach allows us to illuminate with and receive radiation from targets in a way that is frequency selective depending on the pointing direction of the array and also more efficiently detect targets due to the compact spectral model produced by the wavelet filter bank.
3.4 Improvements in Radar Transmitter Performance and Reliability Using High-Voltage Solid- State Modulators and Power Supplies By: Paul D. Brown, Jeffrey A. Casey, J. Michael Mulvany, Timothy A. Hawkey, Michael A. Kempkes, and Marcel P.J. Gaudreau Diversified Technologies, Inc.	Abstract: The operational life of high power radar transmitters that employ microwave VEDs can be extended using high voltage, solid-state modulators and power supplies. Solid-state modulators and power supplies, whether integrated, or stand-alone, can benefit both retrofits and new designs. In this paper, modern solid-state modulator topologies are presented along with the conventional topologies that they replace. Several specific fielded radar transmitters that have been, or could be, retrofitted with "appropriate technology" are identified.
3.5 A High Sensitive Receiver for Baseband Pulse Microwave Radar Sensor Using Hybrid Technology By: S. Abuasaker and G. Kompa University of Kassel	Abstract: This paper describes an improved ultra-wideband (UWB) receiver for the receiving of ultra short electrical pulses transmitted by a short-range microwave radar. The receiver comprises an ultra-wideband balun operating in a frequency range of 600 MHz to 6 GHz and an integrated pulse sharpening circuit. The pulse sharpening circuit is driven by square-wave pulses with amplitude of 1.5 V, a pulse width of 70 ps (FWHM), and a rise time of 30 ps, and a fall time of 80 ps. The receiver is realized in hybrid technology on Copper clad substrate, which makes it low cost and easy to integrate. The principle of operation of the receiver is based on the symmetry of the received input pulses leading to a high sensitivity and a dynamic range of 60 dB.