We present our work on reconfigurable, general-purpose linear photonic circuits. Photonic integrated circuits today resemble the very specialized application specific integrated circuits (ASICs) rather than general-purpose CPUs or highly flexible field-programmable gate arrays (FPGA). Reprogrammable optical circuits could dramatically reduce the time to application or prototype a new optical chip. We will discuss the possibilities of such circuits, and present a working implementation of a 4×4-port universal linear circuit implemented in silicon photonics. We demonstrate the circuit performing two distinct linear operations by changing the software algorithms that controls the circuit.
This article describes the complete design of high performances Ka-Band small size Spatial Power Combiner (SPC) Ampli¯er. Several multiple physics aspects are treated in the proposed study as electromagnetic behavior and thermo-mechanical features. The combiner consists of quadruple Fin lines to microstrip (FLuS) transitions inserted into a WR28 waveguide T-junction. In this structure, 16 Monolithic Microwave Integrated Circuit (MMIC) Solid State Power Ampli¯ers (SSPA's) are integrated. In order to drive the active devices at full power, thermal exposition has been controlled by an opportune heat-sinker subjected to a cooling airow. A main design has been followed by FEM simulation using Ansys-Ansoft HFSS and Comsol Multiphysics. Scattering parameters, stresses and strains have been computed together with the temperature and air°ow distributions. A mean insertion loss of 2 dB is achieved with a return loss better the 10 dB in the 31{37 GHz bandwidth while operating at maximum power. In such condition, the transistors present a maximum displacement of 28.7 ¹m caused by the thermal expansion of the material due to a channel temperature of 125±C, and special techniques have to been applied to avoid the MMIC's breakage.
This article describes the spatial power combining techniques dealing with the state of the art of Spatial Power Combiners (SPC) considering recent developments. A brand- new splitting scheme is proposed where difierent types of SPC are grouped according to the space where power combining and splitting occur. This paper should provide compendium knowledge for SPC design and selection of the opportune SPC basing on the target application. 1. INTRODUCTION In airborne and space applications, characteristics like reliability, size, e-ciency and weight of the Power Ampliflers (PA) assume a very important role in the selection of the proper PA to be employed. High RF power levels are demanded to vacuum tubes ampliflers like TWTA, Klystron or Gyrotrons but those have the main disadvantage to use heated wires and bulky magnets or electromagnets that give greater size and weight and reduce e-ciency (1). So, combined Solid State PA (SSPA) would be greatly appreciated if they could give at least the same order of magnitude in RF power levels, since in this case graceful degradation is increased. Spatial power combining technique is an alternative one to combine many SSPA reducing to a minimum extent the combining losses (2{4). This article deals with the state of the art of Spatial Power Combiners (SPC) and their charac- teristics (14). In addition, it is proposed a new splitting scheme for the SPC family, grouped respect to the ambient where combining and splitting take place, as shown in Figure 1. The fundamental SPC Amplifler's concept is to provide a large power value with minimum losses. In SPC the elec- tromagnetic energy coming from input is divided as much as possible in the space, without using transmission lines, and it is sent to many SSPA's. After amplifled energy is collected, it is sent to output port with the lowest possible number of transmission lines. SPC employees probes, antennas or transitions to take the spatial RF energy and send it to a two wires transmission line: the use of connectors at the ampliflers ports exclude the combiner to belong to the class of SPC. The system's quality is usually determined from its e-ciency. SPC e-ciency can be deflned as how much power is sent to ampliflers respect to how much power is provided to input port, such as it quantifles the capability of the combiner to intercept incoming energy PI and distribute it to N energy dividing/combining internal ports, that is
An investigation on the power energy injection in a resonator by electron stream is reported in this paper, by documenting the power transfer from an electron beam to a resonant cavity, coupled to an external circuitry. The proposed system has been employed to measure the radiation dose deposed by a medical electron linear accelerator. A prototype has been fabricated and tested through VNA cold measurements and dose deposition measurements. A microcon- troller system has been employed to obtain a digital output, the Monitor Units. The linearity of the Monitor Units for di®erent values of accumulated dose, have allowed to employ this system for the real time dose measurements.
It has been proved that Mixed-Line Rate (MLR) could in a cost-efficient manner scope with heterogeneity of constantly increasing traffic demands in core networks. In the same time, the energy efficiency of a Wavelength Division Multiplexing (WDM) transmission system of a MLR solution depends on the number factors (such as energy efficiency of transponders and regenerators, spectral efficiency, length of transmission distance etc.) and number of wavelengths operating with the particular bitrate and modulation format is one of them. Hence, this papers aims at exploring the power efficient 10 Gbps, 40 Gbps and 100 Gbps wavelength assignment strategy as well as the minimum optical bandwidth required to allocate all wavelengths.
The concept of cooperative Multiple-Input-Multiple-Output (MIMO), also referred to as network MIMO, or as Coordinated Multi-Point Transmission (CoMP), was standardized in 3GPP Release 11. The goal of CoMP is to improve the coverage of high data rates and cell-edge throughput, and also to increase system throughput. In this paper we analyze only the latter scenario, using system level simulations in accordance with 3GPP guidelines. It is shown that the use of joint coordinated multipoint transmission achieves additional throughput gains. However, the gains depend on the scheduling type. This paper also indicates that the criterion of fairness is an important parameter when the number of users is high.
We present a three-dimensional Ray-Tracing solver, called RAYWh (RAY-tracing Whistler), for the electromagnetic propagation and power deposition in plasma sources for space thrusters, where high density plasmas (ranging from 10(17) to 10(19) particles/m(3)) are confined by general magnetic configurations with magnitude below < 0.15 T. The 3D Maxwell-Vlasov equations are solved by means of a WKB asymptotic expansion, to investigate the propagation and absorption of whistler waves (excitation frequency is 13.56 MHz) under the influence of general confinement magnetic field, and axisymmetric realistic density profiles. The reduced set of the WKB equations for the wave phase and for the square amplitude of the electric field are solved numerically by means of Hamming's modified predictor-corrector method; the verification of WKB hypothesis are monitored during the simulation.The Ray Tracing approach is employed for the first time in the analysis of plasma sources for space plasma thrusters. A direct comparison between common helicon sources with axial, constant and uniform confinement magnetic field, and plasma sources with actual confinement magnetic field lines revealed a propagative picture with unconventional mode conversions, cut-offs and resonances inside the source that affect the power deposition.
The problem of wave diffraction on a multilayer grating is considered. Numerical technique based on a combination of the incomplete Galerkin method and scattering matrix method is applied. The problem of scattering matrix singularity in the case when a new diffraction order appears is treated in detail and the singularity-free expressions for the scattering matrix are introduced.
In this paper, we provide some examples of an approach resulting in uncorrelated antenna radiation patterns at both ends of a MIMO (Multiple-Input Multiple-Output) wireless link in a given propagation channel. The patterns of antennas exciting dipole or dipole and quadrupole TE and TM modes are analyzed for two generic MIMO channel models based on the Kronecker correlation model with Laplacian angle-of-arrival (AoA) and angle-of-departure (AoD) distributions. The presented results are of a fundamental nature and essential to achieve the promise of MIMO systems.
It has been widely known that experimental results show that multipath components seem to arrive at the receiver in concentrated groups. These groups of multipath components, or clusters, are usually a result of scattering from large physical structures. Their impact on the capacity of Multiple-Input Multiple-Output (MIMO) systems has been widely studied. However, their impact on the spherical vector waves (svw) expansion of the propagation channel has not yet been addressed in the literature. As we have recently shown, a svw expansion provides a compact and straightforward representation of both antennas and channels. This can potentially facilitate designing antennas tailored to take advantage of the spatial and polarimetric characteristics of the propagation environment, which is essential to the deployment of efficient wireless networks. In this paper, we therefore study the impact of clustering on the first and second order statistics of the multimode expansion coefficients. We adopt the simulation approach to exemplify our results and provide numerical examples.
Keywords: Nanophotonics, Plasmonics Reference EPFL-CONF-175227 Record created on 2012-02-28, modified on 2017-05-10
In this paper we investigate the feasibility of a diagnostic method for the Non Destructive Testing (NDT) for concrete structure based on the ultrasonic wave propagation. The propagation of ultrasonic waves in solids is governed by the linear elasticity equation. The determination of the types of waves that can propagate on a given structure is a complex matter as they depend on the geometry, the frequency and the physical properties of the materials. The transverse waves propagation on plane structures has been considered with the aim of locate defects on the structure. The presence of a defect, usually a void, produces a re∞ected wave as ultrasounds do not propagate in air. The analysis of the characteristics of the re∞ected wave is used to localize the defect.
Multidimensional Cauchy integrals are used to calculate numerically the electromagnetic field radiated internally and externally from surfaces on which the field is specified. The calculations are carried fully in the form of Clifford arithmetic and the results appear in the form of Clifford numbers, which are subsequently separated into electric and magnetic fields and compared directly with known analytical results.
