Electrically Small, Broadside Radiating Huygens Source Antenna Augmented with Internal Non-Foster Elements to Increase Its Bandwidth

© 2002-2011 IEEE. A broadside radiating, linearly polarized, electrically small Huygens source antenna system that has a large impedance bandwidth is reported. The bandwidth performance is facilitated by embedding non-Foster components into the near-field resonant parasitic elements of this metamaterial-inspired antenna. High-quality and stable radiation performance characteristics are achieved over the entire operational bandwidth. When the ideal non-Foster components are introduced, the simulated impedance bandwidth witnesses approximately a 17-fold enhancement over the passive case. Within this-10-dB bandwidth, its maximum realized gain, radiation efficiency, and front-To-back ratio (FTBR) are, respectively, 4.00 dB, 88%, and 26.95 dB. When the anticipated actual negative impedance convertor circuits are incorporated, the impedance bandwidth still sustains more than a 10-fold enhancement. The peak realized gain, radiation efficiency, and FTBR values are, respectively, 3.74 dB, 80%, and 28.01 dB, which are very comparable to the ideal values

A 28-GHz, multi-layered, circularly polarized, electrically small, Huygens source antenna

© 2017 IEEE. A 28 GHz, multi-layered, circularly-polarized (CP), Huygens source electrically small antenna (ESA) is presented. The CP radiation is realized by integrating two orthogonal linearly polarized Huygens source EASs into one with an asymmetrical arc strip feed providing the necessary 90° phase difference. Finally, the CP Huygens source ESA exhibits the properties: ka = 0.942; 1.41% FBW-10dB with a 0.47% 3-dB axial ratio (AR) fractional bandwidth; and peak realized gain, FTBR, and radiation efficiency values are 2.03 dBi, 26.72 dB, and 73.4%, respectively. To confirm its efficacy for on-body applications, the specific absorption rate (SAR) values of the Huygens source ESA is evaluated and found to be very low

The Design of a Compact, Wide Bandwidth, Non-Foster-Based Substrate Integrated Waveguide Filter

© 2018 IEEE. A compact, wideband, half-mode substrate integrated waveguide (HM-SIW) filter with internal non-Foster element is demonstrated. First, its passive version is simulated and measured. Next, by integrating an ideal tunable capacitor at the end of the central stub of the HM-SIW resonator, the frequency-agile characteristic of the tunable HM-SIW filter is investigated. Finally, a negative impedance converter (NIC) is developed to replace this tunable capacitor to design a new nonFoster filter. The non-Foster-based HM-SIW filter was realized. Its measured results indicate that it has an operational fractional bandwidth of 10.8% and an electrical size 0.118 × 0.292 λ g 2, which is a 3.93 times bandwidth increase and a 12% electrical size reduction compared to its passive, fixed capacitance version

Prognostic awareness, will to live and health care expectation in patients with terminal cancer

2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Bandwidth-enhanced, compact, near-field resonant parasitic filtennas with sharp out-of-band suppression

© 2002-2011 IEEE. The designs, simulations, and measurements of a class of compact, bandwidth-enhanced filtennas are reported. Our design strategy is illustrated by separately designing a monopole and a bandpass filter to operate primarily in their respective fundamental modes. By combining these elements and manipulating the mutual coupling between them, an enhanced impedance bandwidth filtenna is realized. This strategy is applied to augment metamaterial-inspired near-field resonant parasitic antennas with filters. Simulations of these filtenna systems demonstrate that one can maintain stable radiation performance characteristics no matter how one arranges their component configurations, i.e., their relative positions and orientations. A selected filtenna design prototype was fabricated and tested. The good agreement between the simulated and measured results validates these design principles

Electrically Small, Low-Profile, Planar, Huygens Dipole Antenna with Quad-Polarization Diversity

© 1963-2012 IEEE. An electrically small, low profile, planar, Huygens dipole antenna with four reconfigurable polarization states is presented. The design incorporates both electric and magnetic near-field resonant parasitic elements and a reconfigurable driven element. The four polarization states include two orthogonal linear polarized (LP) and two circular polarization (LHCP and RHCP) states. A 1.5 GHz prototype was fabricated (partially with 3-D additive manufacturing), assembled, and tested. The measured results, in good agreement with their simulated values, demonstrate that even with its simple configuration, electrically small size (ka =0.944), and low-profile height (0.0449 λ0), this reconfigurable Huygens antenna possesses stable broadside radiation performance in all of its four polarization states. The measured results demonstrate that in its x(y)-LP state, the peak realized gain, front-to-back ratio, and radiation efficiency values are, respectively, 3303 dBi (2.97 dBi), 10.7 dB (9.9 dB), and 68.2% (67.5%). For the LHCP (RHCP) states, they are, respectively, 2.82 dBi (2.74 dBi), 11.4 dB (12.5 dB), and 67.1% (65.9%)

Designs of Compact, Flexible, Directive, Near-Field Resonant Parasitic (NFRP) Antennas

© 2018 IEEE. The designs of compact, low-profile, planar, flexible, directive, quasi-Yagi antennas are presented. By placing near-field resonant parasitic (NFRP) elements around the basic driven dipoles, these NFRP antennas achieve compactness, high efficiency and high directivity. The NFRP elements act either as director or reflector elements, empowering the antenna with desirable quasi-Yagi performance characteristics. These NFRP antennas are fabricated using thin substrates which can be bent without enduring any structure damage. The flexibility of these antennas is investigated under two bending conditions by mounting them on different radii cylinders. These antennas can be used in many advanced applications such as intelligent transportation system (ITS) and wearable devices

Dual-linearly polarized, electrically small, low-profile, broadside radiating, huygens dipole antenna

© 1963-2012 IEEE. A dual-linearly polarized, electrically small, low-profile, broadside radiating Huygens dipole antenna is presented, that is, an advanced combination of electric and magnetic near-field resonant parasitic elements. Its prototype was fabricated and tested. The measured results are in good agreement with their simulated values. At 1.515 GHz, the prototype is electrically small ( ka = 0.904 ) and low profile ( 0.0483\lambda -{0} ). It exhibits high port isolation and a large front-to-back ratio (FTBR). The isolation between its two ports is demonstrated to be over 25.8 dB within its -10 dB fractional impedance bandwidth, 0.46%. When port 1 (port 2) is excited, the peak realized gain is 2.03 dBi (2.15 dBi) strictly along the broadside direction with a 12.4 dB (12.1 dB) FTBR

Photocurrent measurements of supercollision cooling in graphene

The cooling of hot electrons in graphene is the critical process underlying the operation of exciting new graphene-based optoelectronic and plasmonic devices, but the nature of this cooling is controversial. We extract the hot electron cooling rate near the Fermi level by using graphene as novel photothermal thermometer that measures the electron temperature ($T(t)$) as it cools dynamically. We find the photocurrent generated from graphene $p-n$ junctions is well described by the energy dissipation rate $C dT/dt=-A(T^3-T_l^3)$, where the heat capacity is $C=\alpha T$ and $T_l$ is the base lattice temperature. These results are in disagreement with predictions of electron-phonon emission in a disorder-free graphene system, but in excellent quantitative agreement with recent predictions of a disorder-enhanced supercollision (SC) cooling mechanism. We find that the SC model provides a complete and unified picture of energy loss near the Fermi level over the wide range of electronic (15 to $\sim$3000 K) and lattice (10 to 295 K) temperatures investigated.Comment: 7pages, 5 figure