D. Tran

Planar Dual-Band Wide-Scan Phased Array in X-Band

The design of a planar dual-band wide-scan phased array is presented. The array uses novel dual-band comb-slot-loaded patch elements supporting two separate bands with a frequency ratio of 1.4:1. The antenna maintains consistent radiation patterns and incorporates a feeding configuration providing good bandwidths in both bands. The design has been experimentally validated with an X-band planar 9 × 9 array. The array supports wide-angle scanning up to a maximum of 60 ° and 50 ° at the low and high frequency bands respectively.

A Novel CPW-fed Optimized UWB Printed Antenna

An optimized coplanar waveguide (CPW)-fed, ultra-wideband (UWB) printed radiator is presented. Balanced shapes are incorporated to the radiating section so that the impedance is matched in a balanced manner over the intended bandwidth. Both the CPW-feed and the antenna sections are realized on one single layer of standard RT5870 high frequency laminate. The radiator possesses good UWB-characteristics in the designed spectrum (4.2 to 14.2 GHz). These include nearly perfectly symmetrical patterns, no side-lobes, no cross-polar components in the symmetrical axial plane and low cross-polar components in all other planes, balanced impedance bandwidth, and almost 4 octaves impedance bandwidth.

Over 150% bandwidth, quasi-magnetic, printed antenna

An optimized coplanar waveguide-fed, quasi-magnetic, printed antenna was described. The analysis of the features of a previously reported such device revealed the highly relevant effect on the bandwidth enhancement of the upper tapering length in the transition region, and of resonator length in the radiating region. By resorting to a parameter study that uses a full-wave, three-dimensional electromagnetic modeling tool, an operational impedance bandwidth of at least 150% was achieved. The antenna has stable co- and low cross- polarized patterns and it displays virtually no feed radiation. This behavior recommends the device for being employed in ultra wide-band applications.

A novel low-profile SWB unidirectional supershaped antenna for advanced ground penetrating radar applications

We report an advanced mathematical method featuring both antenna miniaturization and bandwidth enhancement for super wideband (SWB) antennas intended for advanced GPR applications. By implementing the supershape formula a wide range of practical antenna shapes can be described by just three design parameters, facilitating a lot the optimum antenna design. As a proof-of-concept, a PCB-based, balanced-fed antenna is presented and demonstrated. Our antenna design exhibits SWB characteristics since it operates in the frequency range 0.48 - 10.2GHz meeting the trade-off requirements for depth penetration and range resolution. Additionally, the employed floated ground plane yields a unidirectional broadside radiation pattern making the use of shielding and absorbing cavity unnecessary. Pattern stability is observed over the whole operating frequency range. In time-domain, a low pulse late-time ringing was achieved through the radiator shape optimization and the thin absorbing layer introduction as resistive loading method.

A novel uni-directional, off-axis CPW-fed, matched by unbalanced fork-stub, UWB ring slot antenna printed on single layer PCB with back plane

A rectangular ring slot antenna printed on a single layer substrate capable of providing: uni-omni directional radiation pattern (UODR), linear phase characteristic (LPC), matched impedance bandwidth (IBW) over 58% at -20 dB (VSWR<1.2) is presented. Optimized performances are obtained by using an unusual way of feeding, matching and tuning; the antenna is off-axis fed by CPW structure, matched and tuned by an asymmetric-and-unbalanced fork-stub element.

A novel single layer quad-band patch antenna

This paper presents a novel quad-band omni-directional patch antenna supporting a maximum of four operational sub-bands, with the inherent capability to enhance or eliminate the resonances of interest. The antenna has a single port and its cavity-backed waveguide-like configuration results in minimum mutual coupling levels. The antenna also features a compact and simple structure that is suitable for low-cost mass production.

The relativity of bandwidth - the pursuit of truly ultra wideband radiators for communication applications

An overview on the design of increasingly wider bandwidth radiators that are amenable to being integrated in array configurations is presented. The initial step is represented by moderate bandwidth radiator of the cavity backed patch antennas. The bandwidth characteristics are then substantially increased by combining coplanar waveguide (CPW) feedings and profiled dipoles, the result being radiators with unprecedented performances. This type of radiators are further refined for improving their time-domain adequacy or for ensuring intrinsic filtering properties.

The comparison of the near field beam patterns of 1D-CR MIMO and 2D-CR MIMO arrays

The focusing capabilities for one dimensional (1D-CR MIMO) and two dimensional circularly rotating multiple input multiple output (2D-CR-MIMO) arrays in different media are investigated. Impact of the position of the focusing point on the beamwidth and sidelobe structure is investigated. Impact of the medium (dielectric permittivity and ohmic losses) on the focusing capabilities is studied. For focusing point located at the edge position, within non or low conductive media, the -3 dB main beam width for both arrays become wider. In the same media, the form of the side lobes for 2D-CR MIMO array exhibit a spreading form while those for 1D-CR MIMO array show a spreading and periodic form. Within the high conductive medium, side lobes are concentrated around virtual elements which have a relatively narrow geometrical angle to the focusing point.

Full-wave characterization of EM transmission and propagation in TBM environment, a temporal and spectral GPR study

Details of the temporal and spectral study on the transmission and propagation of EM wave in a 3D-volume model for tunnel boring machine (TBM) environment using near-field power (NFP) approach are reported herewith. Typical TBMs common underground deposits (sand, silt, clay, limestone, granite) with different degrees of wetness (varying from 0% to 20%) are investigated using full-wave electromagnetic method. The NFPs data, taken at predefined calibrated reference plane, revealed clear physical insights and provided accurate information to key ground penetrating radar (GPR) design parameters and the logical arrangement of the antennas, especially when the sensor system is tailored for specific application to as in TBM environment. We also detected several numerical irregular-behaviors (high-spectra had less attenuation than low-spectra) displayed by different host-media, these phenomena are coincided with which Prof. Peter [1994] experimentally reported two decades ago, but he found no answer for this retrospect at that time. These irregularities are mysterious to all principal GPR designers and geo-researchers. In view of interaction of super wideband (SWB) antenna and media, these mysteries are now identified and clarified through full-wave analysis of the transmit-propagation chain. Detailed analysis and numerical results will be explained in details and demonstrated in the full paper and during the conference presentation.