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

Diffraction theory and focusing of light by left-handed materials

A diffraction theory in a system consisting of left-handed and right-handed materials is proposed. The theory is based upon the Huygens's principle and the Kirchhoff's integral and it is valid if the wavelength is smaller than any relevant length of the system. The theory is applied to the calculation of the smearing of the foci of the Veselago lens due to the finite wavelength. We show that the Veselago lens is a unique optical instrument for the 3D imaging, but it is not a ``superlens'' as it has been claimed recently.Comment: 7 pages, 2 figure

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

Microwave Doppler tomography of high impedance ground planes for aerospace applications

© 2016 IEEE. Recent developments in the areas of metamaterials and high impedance ground planes (HIGPs) have created new opportunities for the development of novel multi-functional aerospace materials. One niche application of such materials is the suppression of electromagnetic surface waves across the outer mold line (OML) of aerospace structures. Doppler tomographic imaging and spectral filtering techniques are used to characterize the performance of a simple numerically simulated HIGP. A tapered HIGP concept is introduced to improve the performance over a range of illumination angles. This tapered HIGP is to be embroidered in a commercial aerospace pre-preg material. Experimental results will be presented at the conference

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%)

High birefringent ENZ photonic crystal fibers

© 2018 IEEE. A novel photonic crystal fiber (PCF) design that has a simple circular air hole configuration is reported that yields a very high birefringence. The enhanced birefringence is achieved by filling a select number of the air holes in its cladding with an epsilon-near-zero (ENZ) material to break the index symmetry of its X- A nd Y-polarization states. Comparisons of initial numerical simulations based on ideal ENZ materials and then those based on realistic ones demonstrate that the high birefringence property is still maintainable with currently available ENZ materials

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

Compact Planar Ultrawideband Antennas with Continuously Tunable, Independent Band-Notched Filters

© 2016 IEEE. A compact planar ultrawideband antenna with continuously tunable, independent band notches for cognitive radio applications is presented. The antenna is fabricated using a copper-cladded substrate. A radiating patch with an inverted rectangular T-slot is etched on the top side of the substrate. A straight rectangular strip with a complete gap is embedded into the T-slot. By placing a single varactor diode across this gap, a frequency-agile band-notch function below 5 GHz is realized. On the bottom side of the substrate, a U-shaped parasitic element having an interdigitated-structure is placed beneath the radiating patch. The second narrow band notch is created by inserting a second varactor diode into the gap on one leg of the parasitic element. It has a frequency-agile performance above 5 GHz. The presence of the interdigitated structure suppresses higher order resonant modes and enhances the tunability of the notched bandwidth. Because these antenna structures naturally block dc, a very small number of lumped elements are required. The experimental results, which are in good agreement with their simulated values, demonstrate that both band notches can be independently controlled and the entire frequency-agile fractional bandwidth is as high as 74.5%, demonstrating a very wide notched frequency-agile coverage