The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Future communication links will require higher data rates, multiple beams, and higher transmit/receive gains, in addition to smaller weight, cost, and power. With the growing interest for reduced size platforms and the requirement for ultra-wideband (UWB) performance to address multifunctionality, there is a strong need for UWB apertures to enable increased spectral efficiency, multifunctionality...
Synthetic aperture sonar has the characteristics of high resolution imaging which is not limited by the detection range. It can be used for imaging and mapping of the seafloor. However, the product value of detection range and speed of navigation is limited by the physical length of the array in the traditional synthetic aperture sonar. When the speed of navigation is improved on condition that the...
This paper presents our study on a sparse antenna array for 0.22 THz imaging. Based on the effective aperture concept for the design of sparse antenna array, two schemes for high performance THz imaging of a target at distance of 1 m have been achieved in simulation. Then, different schemes of larger array element spacing and mechanical scanning spacing have been investigated to build the relationship...
Fast cardiac imaging using diverging waves (DW) is receiving much attention. Coherent compounding is important to keep spatial resolution and CNR acceptable. Two approaches have been presented in literature to do so: i) the full aperture of the probe is used and the virtual focus is moved along an arc centered at the center of the probe (ARC); ii) a sub-aperture is used and the virtual focus is linearly...
Lateral resolution and therefore image quality in ultrasound is tied to aperture size. While this relationship is understood in ideal imaging conditions, the utility of a large aperture in the presence of clutter is unknown. This problem is particularly relevant to abdominal imaging where thick tissue layers and deep targets create a challenging imaging environment. Previous studies have focused on...
Bio-medical ultrasound imaging has recently gained considerable attention. A two-dimensional (2-D) array is essential for three-dimensional (3-D) volumetric imaging. Fully populated 2-D dense array requires thousands of active elements and their interconnections. We present a 2-D CMUT sparse array with 128 elements for 3-D volumetric imaging. This CMUT sparse array with a die size of 6.3 mm × 6.3...
We present a fully-populated 8×8 2D-phased array, capable of emitting directed air-coupled ultrasound at 40 kHz with λ/2-pitch size for zero grating lobes. In comparison to our previous work, in which we describe a 1D-phased array, we use 3D-printing to realize the wave guide structure. Besides the key idea to separate the vibrating from the acoustic aperture, the 3D-printing approach allows implementing...
Based on the linear relationship of channel data between synthetic transmit aperture (STA) and apodized plane wave (PW) firing, we previously proposed compressed sensing (CS) based STA (CS-STA) for linear array (Liu et al, IEEE TMI 2017), which achieves higher frame rate and higher contrast-to-noise ratio (CNR) than STA while maintaining its high resolution. Because diverging wave (DW) instead of...
Sparse multistatic array designs that are based on the effective aperture concept enable real-time and cost-effective 3D CW terahertz imaging solutions. However, reduced system costs or challenging imaging scenarios eventually require a violation of the Nyquist sampling criterion, which leads to the appearance of grating lobes in the terahertz image. We propose a method to suppress grating lobes by...
Radio frequency interference (RFI) has becoming a seriously limitation in the retrieval of geophysical parameters from the measurements of microwave radiometers. In this work, a novel RFI localization approach is presented here to improve the computationally complexity by using virtual arrays and direction of arrival (DOA) estimations techniques. The proposed RFI localization method utilizes the underlying...
A phased array lens has limited bandwidth due to the phase shifters that collimate and scan the beam. A wideband signal requires time delay units in place of phase shifters. This paper investigates the feasibility of implementing time-delay units in array lens antennas. Time-delay compensation mechanisms for array lens antennas are outlined and investigations are carried to determine the required...
The aim of this study is to compare the performance of different multiple-input multiple-output (MIMO) array topologies, intended to be used in ultra-wideband (UWB) near-field imaging applications, by using an analysis method that does not include the effects of image reconstruction algorithm. For this purpose, maximum projection method, previously proposed for the analysis of UWB arrays under far-field...
This paper presents a method with which to calculate the maximum scan error due to phase quantization in the visible region of dense phased arrays. The scan error is expressed as a function of the density ratio and the number of bits being used for digitization. A closed-form expression is derived with which the maximum scan error as well as the maximum scan range in the visible region of the array...
Knowing the electric fields that may be encountered in the proximity of large array antennas is critical for determining the compatibility of equipment near that antenna. Given a few parameters such as effective area, frequency and power, the electric field magnitudes at any given range can be approximated within easily determined boundaries using well-understood electromagnetic theory. This paper...
Airframe manufacturers, avionics companies, satellite operators and major airlines have launched programs to develop high speed data services for use on commercial aircraft and business jets. Inmarsat currently supplies aircraft with medium-rate data service and high quality voice throughout the world on both spot-beams and global beams. In 2001 EMS Technologies began installing Inmarsat BGAN transceivers...
Pinhole-array-based hand-held light field cameras can be used to capture 4-dimensional light field data for different applications such as digital refocusing and depth estimation. Our previous experiences suggest the design of the pinhole array mask is very critical to the performance of the camera, and the selection of mask parameters could be very different between applications. In this paper, we...
This study reports a novel tight-coupled dipole array antenna to operate with up to six octave bandwidth and 60 degrees scanning. The array was designed through full-wave EM simulations by employing the current sheet array radiator concept that was advanced by a novel integrated feed network. Several prototypes of planar and conformal arrays across 0.3–20 GHz have been fabricated and tested with good...
This paper discusses a fabrication approach and experimental validation of a very large, planar active electronically scanned array (AESA). The planar AESA architecture employs a monolithic printed circuit board (PCB) with 768 active antenna elements at X-Band. Manufacturing physically large arrays with high element counts is discussed in relation to construction, assembly and yield considerations...
In conventional light field near eye display (LF-NED) using pinhole aperture arrays, as the pupil size changes under different conditions, the overlapping area of adjacent elemental images is not certain. This is the primary cause of an uncertain net-shaped bright-dark pattern on the image plane. In this paper, a proof-of-concept light field near eye display prototype for virtual reality applications...
A switched array tile which is part of a large aperture for near-field microwave imaging is presented. The tile is based on the Boundary Array (BA), a sparse array topology for hardware efficient realization of imaging apertures. The larger array formed with the tile samples a scene with no redundancy, and is compatible with fast imaging techniques. Details on the design and realization of the tile...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.