| 1. |
- Höök, Anders, 1962, et al.
(författare)
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Soliton instabilities and pulse compression in minimum dispersion fibers
- 1994
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Ingår i: IEEE Journal of Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9197 .- 1558-1713. ; 30:8, s. 1831-1841
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Tidskriftsartikel (refereegranskat)abstract
- A new stability of ultrashort pulses in optical fibers is demonstrated which, together with a recently discovered modulation instability, is shown to deteriorate a pulse compression mechanism. The pulse compression is analyzed in detail by means of a perturbation technique.
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| 2. |
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| 3. |
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| 4. |
- Ilie, Dragos, et al.
(författare)
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Avoiding Detection by Hostile Nodes in Airborne Tactical Networks
- 2023
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Ingår i: Future Internet. - : MDPI. - 1999-5903. ; 15:6
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Tidskriftsartikel (refereegranskat)abstract
- Contemporary airborne radio networks are usually implemented using omnidirectional antennas. Unfortunately, such networks suffer from disadvantages such as easy detection by hostile aircraft and potential information leakage. In this paper, we present a novel mobile ad hoc network (MANET) routing protocol based on directional antennas and situation awareness data that utilizes adaptive multihop routing to avoid sending information in directions where hostile nodes are present. Our protocol is implemented in the OMNEST simulator and evaluated using two realistic flight scenarios involving 8 and 24 aircraft, respectively. The results show that our protocol has significantly fewer leaked packets than comparative protocols, but at a slightly higher cost in terms of longer packet lifetime.
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| 5. |
- Karlsson, Magnus, 1967, et al.
(författare)
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A variational approach to optical soliton collisions
- 1994
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Ingår i: Physica Scripta. - : IOP Publishing. - 1402-4896 .- 0031-8949. ; 50:3, s. 265-270
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Tidskriftsartikel (refereegranskat)abstract
- The mathematical analogy between the nonlinear Schrödinger equations describing propagation of temporal soliton pulses in optical fibres, and propagation of spatial soliton beams in planar optical wave guides is discussed. A straightforward variational method, based on trial functions and Rayleigh-Ritz optimization, is demonstrated and applied to incoherent interaction of solitons. We study incoherent soliton interaction in a wavelength-multiplexed optical-fibre communication system, as well as the analogous problem for crossed optical beams in a planar waveguide. The predictions of the variational approach are also shown to be in good agreement with numerical simulation results and with experiments.
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| 6. |
- Karlsson, Magnus, 1967, et al.
(författare)
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Soliton-like pulses governed by fourth order dispersion in optical fibers
- 1994
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018. ; 104:4-6, s. 303-307
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Tidskriftsartikel (refereegranskat)abstract
- The properties of pulse propagation in a nonlinear fiber including negative fourth order dispersion added to anomalous second order dispersion are analyzed numerically and analytically. An exact localized analytical solution is presented, and using an approximate variational method, an entire family of stationary approximate solutions is also obtained. These solutions are found to be in excellent agreement with numerical simulations.
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| 7. |
- Khanal, Prabhat, 1993, et al.
(författare)
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A Wide-Scanning Array Antenna of Connected Vertical Bowtie Elements Structurally Integrated Within an Aircraft Fuselage
- 2023
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 71:5, s. 4216-4227
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Tidskriftsartikel (refereegranskat)abstract
- A low-profile, wide-scanning phased-array antenna of vertical bowtie elements fully integrated with a structurally efficient radome and ribs of an aircraft fuselage is proposed in this article. The array is designed to simultaneously fulfil the electrical requirements of an airborne antenna sensor and the mechanical requirements of a load-carrying aircraft fuselage. The array antenna is capable of steering the beam up to ±80 degrees in the azimuth plane over a 20% bandwidth (2.4–3 GHz) with the active reflection coefficient ( Γact ) below −10 dB in an infinite array environment. Experimental results of a 16×16 element array demonstrator agree well with the simulation results. The 16×16 array antenna is capable of steering the beam up to ±60 degrees and ±75 degrees with the bandwidth of 20% and 10%, respectively, at Γact≤−10 dB. The array antenna also achieved good stiffness and performed well in the vibration loads of commercial transport aircraft.
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| 8. |
- Khanal, Prabhat, 1993, et al.
(författare)
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Edge Truncation Effects in a Wide-Scan Phased Array of Connected Bowtie Antenna Elements
- 2020
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Ingår i: 14th European Conference on Antennas and Propagation, EuCAP 2020. ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Edge truncation effects are critical when designing a phased array, as these can lead to the variation of the active antenna impedance and radiation pattern between individual array elements. This paper investigates edge truncation effects in an array of connected Bowtie antenna elements that has been initially designed through an infinite array approach. This design represents a novel implementation of the connected-array concept that offers a wide-scan performance with up to ± 80 degrees scan range in the E-plane (in the infinite array). The goal of this study is to estimate the minimum size of a realistic finite array of such connected Bowtie antennas.
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| 9. |
- Khanal, Prabhat, 1993, et al.
(författare)
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Integration of Airborne Early Warning Radar Platforms on Aircraft
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The need for a long-range and complete Air Picture has long since motivated the presence of airborne early warning (AEW) radar platforms. Later developments, such as stealth and advancing threats at low altitudes or hypersonic speeds have nothing but reinforce the need for increased-performance AEW. However, the high costs for the platform, integration, and operations restrict the number of platforms to a point where these high-value assets become sensitive to preemptive actions by an adversary. Therefore, SAAB has within the NFFP7 framework launched a series of studies aiming at smaller, adapted, and cost-efficient unmanned AEW platforms with extreme endurance. Thus, the aerodynamic performance of the carrier plus radar must be optimized, which implies that the projected area of the radar must be minimized. In this project, we study the possibility of integrating the antenna layer in the fuselage structure of the aircraft, thus gaining (i) body width and (ii) a more optimal wet geometry.
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| 10. |
- Liao, Wan-Chun, 1985, et al.
(författare)
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A Ka-Band Active Integrated Antenna for 5G Applications: Initial Design Flow
- 2018
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Ingår i: 2018 2nd URSI Atlantic Radio Science Meeting (AT-RASC).
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Konferensbidrag (refereegranskat)abstract
- Initial technology and design decisions are presented as part of a design flow to realize an active integrated antenna (array) element for 5G applications at Ka-band. The objective is to synthesize an antenna impedance that directly matches the amplifier optimal load impedance in order to maximize the overall efficiency of the integrated antenna-amplifier system while attaining an output power in the range of 15–25 dBm. A strategy to subsequently co-optimize this combined system is also discussed. Direct matching overcomes the insertion losses and bandwidth limitations of impedance-transforming networks, obviates the use of a standard 50-Ohm reference impedance, and potentially results in more cost-effective, more compact, and better performing active antenna designs in general.
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