Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 8 Articles
AMultiport Amplifier (MPA) is an implementation of the satellite power amplification section that allows sharing the payload RF\r\npower among several beams/ports and guarantees a highly efficient exploitation of the available DC satellite power. This feature\r\nis of paramount importance in multiple beam satellite systems where the use of MPAs allows reconfiguring the RF output power\r\namong the different service beams in order to handle unexpected traffic unbalances and traffic variations over time. This paper\r\npresents Monte Carlo simulations carried out by means of an ESA in-house simulator developed in Matlab environment. The\r\nobjective of the simulations is to analyse how the MPA performance, in particular in terms of isolation at the MPA output ports, is\r\naffected by the amplitude and phase tracking errors of the high power amplifiers within the MPA....
We have developed a new, zone-based compact physics-based AlGaN/GaN heterojunction field-effect transistor (HFET) model\nsuitable for use in commercial harmonic-balance microwave circuit simulators. The new model is programmed in Verilog-A, an\nindustry-standard compact modeling language. The new model permits the dc, small-signal, and large-signal RF performance\nfor the transistor to be determined as a function of the device geometric structure and design features, material composition\nparameters, and dc and RF operating conditions. The new physics-based HFET model does not require extensive parameter\nextraction to determine model element values, as commonly employed for traditional equivalent-circuit-based transistor models.\nThe new model has been calibrated and verified. We report very good agreement between simulated and measured dc and RF\nperformance of an experimental C-band microwave power amplifier....
We present the bidirectional power line communication system developed in parallel to an electronic board for driving and control\nof HID (high-intensity discharge) and LED (light-emitting diode) lamps. The communication system, developed to be applied\nin the sector of public illumination, is been designed to combine high efficiency and reliability with low production costs; it\nconsists indeed of discrete cheap components. The communication system described in this paper implements the technique of\ntransporting digital information over existing power lines, avoiding the issue of installing new cables. Digitized signals can use\npower line cables through the amplitude voltage and current modulation. The solution proposed is more advantageous compared\nto communication techniques currently on the market which are essentially two types, power line carrier (modem for high-voltage\nlines) or radio (zig-Bee transceiver)....
Neurons cultured directly over open-gate field-effect transistors result in a hybrid device, the neuron-FET. Neuron-FET\r\namplifier circuits reported in the literature employ the neuron-FET transducer as a current-mode device in conjunction with\r\na transimpedance amplifier. In this configuration, the transducer does not provide any signal gain, and characterization of the\r\ntransducer out of the amplification circuit is required. Furthermore, the circuit requires a complex biasing scheme that must\r\nbe retuned to compensate for drift. Here we present an alternative strategy based on the gm/Id design approach to optimize a\r\nsingle-stage common-source amplifier design. The gm/Id design approach facilitates in circuit characterization of the neuron-\r\nFET and provides insight into approaches to improving the transistor process design for application as a neuron-FET transducer.\r\nSimulation data for a test case demonstrates optimization of the transistor design and significant increase in gain over a current\r\nmode implementation....
Copper phthalocyanine-based organic thin-film transistors (OTFTs) with zirconium oxide (ZrO2) as gate dielectric have been\nfabricated on glass substrates. The gate dielectric is annealed in N2 at different durations (5, 15, 40, and 60 min) to investigate the\neffects of annealing time on the electrical properties of the OTFTs. Experimental results show that the longer the annealing time for\nthe OTFT, the better the performance. Among the devices studied, OTFTs with gate dielectric annealed at 350?C in N2 for 60 min\nexhibit the best device performance. They have a small threshold voltage of -0.58 V, a low subthreshold slope of 0.8 V/decade,\nand a low off-state current of 0.73 nA. These characteristics demonstrate that the fabricated device is suitable for low-voltage and\nlow-power operations. When compared with the TFT samples annealed for 5 min, the ones annealed for 60 min have 20% higher\nmobility and nearly two times smaller the subthreshold slope and off-state current. The extended annealing can effectively reduce\nthe defects in the high-k film and produces a better insulator/organic interface. This results in lower amount of carrier scattering\nand larger CuPc grains for carrier transport....
We present a novel method to model the tracking behavior of semiconductor transistors undergoing across-chip variations in a\r\ncompactMonte Carlo model for SPICE simulations and showan enablement of simultaneousN(N-1)/2 tracking relations among\r\nN transistors on a chip at any poly density, any gate pitch, and any physical location for the first time. At smaller separations,\r\nour modeled tracking relation versus physical location reduces to Pelgrom�s characterization on device�s distance-dependent\r\nmismatch. Our method is very compact, since we do not use a matrix or a set of eigen solutions to represent correlations among\r\nN transistors....
The nanocomposite gate insulating film of a pentacene-based thin film transistor was deposited by inkjet printing. In this study,\r\nutilizing the pearl miller to crumble the agglomerations and the dispersant to well stabilize the dispersion of nano-TiO2 particles in\r\nthe polymer matrix of the ink increases the dose concentration for pico-jetting, which could be as the gate dielectric film made by\r\ninkjet printing without the photography process. Finally, we realized top contact pentacene-TFTs and successfully accomplished the\r\npurpose of directly patternability and increase the performance of the device based on the nanocomposite by inkjet printing. These\r\ndevices exhibited p-channel TFT characteristics with a high field-effect mobility (a saturation mobility of ~0.58 cm2 V-1 s-1), a\r\nlarge current ratio (>103) and a low operation voltage (<6V). Furthermore, we accorded the deposited mechanisms which caused\r\nthe interface difference between of inkjet printing and spin coating. And we used XRD, SEM, Raman spectroscopy to help us\r\nanalyze the transfer characteristics of pentacene films and the performance of OTFTs....
We have presented an RF MEMS tuneable lowpass filter. Both distributed transmission lines and RF MEMS capacitances were\r\nused to replace the lumped elements. The use of RF MEMS capacitances gives the flexibility of tuning the cutoff frequency of the\r\nlowpass filter.We have designed a low-pass filter at 9ââ?¬â??12 GHz cutoff frequency using the theory of stepped impedance transmission\r\nlines. A prototype of the filter has been fabricated using parallel plate capacitances. The variable shunt capacitances are formed by\r\na combination of a number of parallel plate RF MEMS capacitances. The cutoff frequency is tuned from C to X band by actuating\r\ndifferent combinations of parallel capacitive bridges. The measurement results agree well with the simulation result....
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