Compact ultra-wideband monopole antenna with tunable notch bandwidth/frequency ratio

A compact tunable notch band ultra-wideband (UWB) antenna is implemented. The band notch characteristics have been obtained by placing a square-shaped metallic loop in the upper ground plane connected via PIN diode. The obtained notched frequency bandwidth can be altered by changing the states of the PIN diode. UWB response with narrow-band notch operation is observed when PIN diode is in ON state. When the PIN diode is in OFF state, the bandwidth of the obtained band notch widens by suppressing the first higher-order resonance and thus a narrow dual-band response is obtained. Moreover, the ratio of the frequency of first higher-order to the fundamental mode in the pass-band can be tuned with the different values as 1.584 and 2.20 in the ON and OFF state of the PIN diode, respectively. Furthermore, the antenna structure offers a compact geometry for the operation with the UWB response with band notch characteristics.

Islands in de Sitter space

We consider black holes in 2d de Sitter JT gravity coupled to a CFT, and entangled with matter in a disjoint non-gravitating universe. Tracing out the entangling matter leaves the CFT in a density matrix whose stress tensor backreacts on the de Sitter geometry, lengthening the wormhole behind the black hole horizon. Naively, the entropy of the entangling matter increases without bound as the strength of the entanglement increases, but the monogamy property predicts that this growth must level off. We compute the entropy via the replica trick, including wormholes between the replica copies of the de Sitter geometry, and find a competition between conventional field theory entanglement entropy and the surface area of extremal “islands” in the de Sitter geometry. The black hole and cosmological horizons both play a role in generating such islands in the backreacted geometry, and have the effect of stabilizing the entropy growth as required by monogamy. We first show this in a scenario in which the de Sitter spatial section has been decompactified to an interval. Then we consider the compact geometry, and argue for a novel interpretation of the island formula in the context of closed universes that recovers the Page curve. Finally, we comment on the application of our construction to the cosmological horizon in empty de Sitter space.

Design and Development of MIMO Antennas for WiGig Terminals

This article presents a design for high-gain MIMO antennas with compact geometry. The proposed design is composed of four antennas in MIMO configuration, wherein, each antenna is made up of small units of microstrip patches. The overall geometry is printed on the top layer of the substrate, i.e., Rogers RT-5880 with permittivity of 2.2, permeability of 1.0, dielectric loss of 0.0009, and depth of 0.508 mm. The proposed design covers an area of 29.5 × 61.4 mm2, wherein each antenna covers an area of 11.82 × 25.28 mm2. The dimensions of the microstrip lines in each MIMO element were optimized to achieve a good impedance matching. The design is resonating at 61 GHz, with a wide practical bandwidth of more than 7 GHz, thereby covering IEEE 802.11ad WiGig (58–65 GHz). The average value of gain ranges from 9.45 to 13.6 dBi over the entire frequency bandwidth whereas, the average value of efficiency ranges from 55.5% to 84.3%. The proposed design attains a compact volume, wide bandwidth, and good gain and efficiency performances, which makes it suitable for WiGig terminals.

Review of freeform TIR collimator design methods

Total internal reflection (TIR) collimators are essential illumination components providing high efficiency and uniformity in a compact geometry. Various illumination design methods have been developed for designing such collimators, including tailoring methods, design via optimization, the mapping and feedback method, and the simultaneous multiple surface (SMS) method. This paper provides an overview of the different methods and compares the performance of the methods along with their advantages and their limitations.

BLACK HOLE PROBES OF AUTOMORPHIC SPACE

Over the past few years the arithmetic Langlands program has proven useful in addressing physical problems. In this paper it is shown how Langlands' reciprocity conjecture for automorphic forms, in combination with a representation theoretic notion of motives, suggests a framework in which the entropy of automorphic black holes can be viewed as a probe of spacetime that is sensitive to the geometry of the extra dimensions predicted by string theory. If it were possible to produce black holes with automorphic entropy in the laboratory their evaporation would provide us with information about the precise shape of the compact geometry.