Pierre A. Dufilie

Bio: Pierre A. Dufilie is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Antenna (radio) & Antenna array. The author has an hindex of 2, co-authored 8 publications receiving 51 citations.

Development of a high-throughput microwave imaging system for concealed weapons detection

Abstract: A video-rate microwave imaging aperture for concealed threat detection can serve as a useful tool in securing crowded, high foot traffic environments. Realization of such a system presents two major technical challenges: 1) implementation of an electrically large antenna array for capture of a moving subject, and 2) fast image reconstruction on cost-effective computing hardware. This paper presents a hardware-efficient multistatic array design to address the former challenge, and a compatible fast imaging technique to address the latter. Prototype hardware which forms a partition of an imaging aperture is discussed. Using this hardware, it is shown that the proposed array design can be used to form high-fidelity 3D images, and that the presented image reconstruction technique can form an image of a human-sized domain in ≤0.1s with low cost computing hardware.

A Ka-band Dual-Pol Monopulse Shaped Reflector Antenna

Abstract: MIT LL is developing a small dual-polarized Ka-band monopulse antenna, which has very challenging specifications imposed on the radiator that require a sophisticated and efficient reflector antenna design. Reflector shaping is a technique that can be used to create a specific non-standard reflector profile to generate a desired aperture illumination that classical parabolic reflector surfaces cannot provide. A comparison with the classical Cassegrain parabolic reflector antenna will be reviewed and results discussed for the antenna design approach utilized at MIT LL. Measured data will be presented for the prototype antenna that was constructed.

Space-Deployed Inflatable Dual-Reflector Antenna: Design and Prototype Measurements

Abstract: Large RF apertures have long proven to be a vexing challenge for small satellite/CubeSat platforms due to inherent mass and volume restrictions which has limited their use in SAR imaging, RF communications, and astronomy. Fixed apertures are fundamentally limited by the size of the platform itself so these restrictions drive the satellite designer to deployable apertures within which two primary classes exist: mechanical deployables and inflatable balloons. The primary trade between the two is packed volume and surface precision/accuracy per deployed aperture area. Inflatables offer significantly better packed volume than a mechanical deployable, but it is significantly harder to realize high precision surfaces. This paper details an axisymmetric array-fed confocal parabolic Gregorian reflector inflatable antenna system that has been designed, built, and characterized in the RF for potential space deployment from a small-sat payload. The system features three individual inflation chambers, a 2.4 meter primary reflector chamber, an independently adjustable 0.25 meter sub-reflector, and a 2.7 meter diameter torus that packs down to ∼1.25U, making use of this system feasible on many CubeSat platforms. The innovative implementation of the Gregorian design relaxes the fabrication tolerances required to achieve good RF performance. A novel approach for post-assembly correction of fabrication defects in the primary reflector has also been developed. Initial prototypes demonstrated approximately 38 dBi of gain with a ∼1◦ beamwidth at 10 GHz. This represents an improvement in realized gain of greater than 13 dBi, 6 dB improvement in primary reflector surface efficiency, while also increasing reflector aperture diameter by a factor of 2.4 over recent literature. A path forward to improve the manufacturing design to achieve higher performance at X-band and enable Ku-band capability is also discussed as well as considerations for deployment and use in a space environment.

Practical Design of an Octave-band Stacked Patch Antenna Phased Array

Abstract: MIT Lincoln Laboratory is developing a planar ultra-wideband phased array antenna. The radiator is required to operate over an octave of bandwidth and provide up to 55° of scanning in elevation and azimuth with dual polarization capability. Although these requirements are easily met using state of the art designs such as a PUMA or Vivaldi array, the design requires co-located phase centers for the unit cell. A detailed description of the probe-fed stacked patch radiator design will be reviewed and results discussed. Measurements will be presented for the prototype that was fabricated.

Compact Cavity-Backed Discone Array for Conformal Omnidirectional Antenna Applications

Abstract: A compact shallow cavity-backed discone array for conformal omnidirectional vertically polarized antenna applications is investigated. The antenna described consists of four discone antennas arranged in a ring array in a circular contoured conical cavity covered with a radome. The individual discone antennas are fed with coaxial transmission lines. This paper describes the antenna design and electromagnetic simulations of the antenna array. Good omnidirectional realized gain radiation patterns are demonstrated over the 960 MHz to 1215 MHz Tactical Air Navigation System (TACAN) band, an approximate 23% bandwidth.

Review of Metasurface Antennas for Computational Microwave Imaging

Abstract: This article covers recent advances in the fusion of metasurface antenna design and computational imaging (CI) concepts for the realization of imaging systems that are planar, fast, and low cost. We start by explaining the operation of metamaterial antennas which can generate diverse radiation patterns. Their advantages and distinctions from previous antennas are elucidated. We then provide an intuitive overview of the CI framework and argue that metamaterial antennas are a near ideal platform for implementing such schemes at microwave frequencies. We describe two metamaterial antenna implementations: frequency diverse and electronically reconfigurable. The tradeoffs governing the design and operation of each architecture are examined. We conclude by examining the outlook of metamaterial antennas for microwave imaging and propose various future directions.

Near-Field MIMO-SAR Millimeter-Wave Imaging With Sparsely Sampled Aperture Data

Abstract: The primary challenge of a cost-effective and low-complexity near-field millimeter-wave (mmWave) imaging system is to achieve high resolution with a few antenna elements as possible. Multiple-input multiple-output (MIMO) radar using simultaneous operation of spatially diverse transmit and receive antennas is a good candidate to increase the number of available degrees of freedom. On the other hand, higher integration complexity of extremely dense transceiver electronics limits the use of MIMO only solutions within a relatively large imaging aperture. Hybrid concepts combining synthetic aperture radar (SAR) techniques and sparse MIMO arrays present a good compromise to achieve short data acquisition time and low complexity. However, compared with conventional monostatic sampling schemes, image reconstruction methods for MIMO-SAR are more complicated. In this paper, we propose a high-resolution mmWave imaging system combining 2-D MIMO arrays with SAR, along with a novel Fourier-based image reconstruction algorithm using sparsely sampled aperture data. The proposed algorithm is verified by both simulation and processing real data collected with our mmWave imager prototype utilizing commercially available 77-GHz MIMO radar sensors. The experimental results confirm that our complete solution presents a strong potential in high-resolution imaging with a significantly reduced number of antenna elements.

Novel Efficient 3D Short-Range Imaging Algorithms for a Scanning 1D-MIMO Array

Abstract: Recently, millimeter-wave 3D holography techniques employing a scanning 1D multiple input multiple output (MIMO) array have shown several superiorities for short-range applications than traditional single input single output ones. However, current imaging algorithms for this emerging regime are not satisfied, either too slow as a back projection manner is used or of poor quality since several steps of approximations are introduced. In this paper, two fast fully focused imaging algorithms are developed towards fixing these drawbacks. Both algorithms are based on the assumption that the receivers are evenly distributed. The first algorithm further hypothesizes that the transmitters are also evenly located, while the second algorithm needs looser restrictions that the transmitters can be arbitrarily positioned. The frequency domain expressions of the modified Kirchhoff method are also derived and used to promote the precision of the proposed algorithms. In addition, several implementation issues, including resolution, sampling criteria, and computational complexity are discussed. Finally, both simulation and experimental results validate the effectiveness of the proposed methods on reconstruction quality and computational efficiency.

Near-Field 3-D Millimeter-Wave Imaging Using MIMO RMA With Range Compensation

Abstract: This paper presents a multi-input-multi-output (MIMO) range migration algorithm (RMA) with range compensation for near-field millimeter-wave imaging. The proposed algorithm is derived based on the effective phase center principle and scalar diffraction theory. Compared with the original MIMO RMA, the propagation loss is compensated better, and the reconstructed image quality is improved significantly. In the process of image reconstruction, a multistatic array topology is transformed to a monostatic array, and the round-trip propagation is converted into unidirectional optical field propagation. The efficiency of the proposed algorithm is analyzed theoretically, and demonstrated experimentally. Numerical simulations and experimental results show that the propagation loss in range is properly compensated by the proposed algorithm.

Development and Demonstration of MIMO-SAR mmWave Imaging Testbeds

Abstract: Multiple-input multiple-output (MIMO) radars and synthetic aperture radar (SAR) techniques are well researched and have been effectively combined for many imaging applications ranging from remote sensing to security. Despite numerous studies that apply MIMO concepts to SAR imaging, the design process of a MIMO-SAR system is non-trivial, especially for millimeter-wave (mmWave) imaging systems. Many issues have to be carefully addressed. Besides, compared with conventional monostatic sampling schemes or MIMO-only solutions, efficient image reconstruction methods for MIMO-SAR topologies are more complicated in short-range applications. To address these issues, we present highly-integrated and reconfigurable MIMO-SAR testbeds, along with examples of three-dimensional (3-D) image reconstruction algorithms optimized for MIMO-SAR configurations. The presented testbeds utilize commercially available wideband mmWave sensors and motorized rail platforms. Several aspects of the MIMO-SAR testbed design process, including MIMO array calibration, electrical/mechanical synchronization, system-level verification, and performance evaluation, are described. We present three versions of MIMO-SAR testbeds with different implementation costs and accuracies to provide alternatives for other researchers who want to implement their testbed framework. Several representative examples in various real-world imaging applications are presented to demonstrate the capabilities of the proposed testbeds and algorithms.