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.
