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The performance of a dc to 3 GHz externally modulated link utilizing balanced high-power photodetection is presented. Nonlinearity measurements of high power photodiodes show 1 dB compression currents in excess of 55 mA and an output third-order intercept point of +32 to +34 dBm. These high current photodetectors permit the use of high power lasers as external modulator sources for low noise fiber optic links with only small degradations in the predicted link dynamic range. An externally modulated link with a 240 mW Nd:YAG laser, a dual-output 4-V V, (dc) modulator, and balanced 100 mA total photocurrent yielded a link noise figure from 15.5 to 17.5 dB, a spur-free dynamic range of 119.5 dBHz2/3, and a 1-dB compression dynamic range of 168.4 dBHz 相似文献
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Nanocomposites (NCs) that are made magnetically responsive in controlled conditions attract continuing interest for their added magnetic properties. In this study, we report on the preparation and full characterization of a multifunctional NC composed of magnetic γ-Fe(2)O(3) nanoparticles (NPs) covalently attached to the surface of polyaminated (polyNH(2)) poly(2,6-di-pyrrol-1-yl-hexanoic acid) (pDPL) nanotubes (NTs). Such a hybrid conducting polymer iron oxide maghemite γ-Fe(2)O(3)@pDPL NC built specifically on covalent bonding has never been reported. The maghemite γ-Fe(2)O(3) NPs were prepared using an innovative ultrasound-assisted Ce(3+) doping process, resulting in polycarboxylation of the NP surface useful for control of aggregation and derivatization of functionality. The second component of the NC, i.e. polyNH(2)-modified pDPL NTs, was prepared from an acid functional pyrrole species followed by amine modification. The resulting innovative γ-Fe(2)O(3)@pDPL NC can be viewed as a multifunctional nanomaterial since it possesses both types of derivatization, i.e. polyCOOH (NPs) and polyNH(2) (NTs) combined with magnetic responsivity. 相似文献
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V. A. Pilipovich S. A. Sergienya A. K. Esman V. B. Zalesskii 《Measurement Techniques》2005,48(6):595-600
An automated system for plotting the current-voltage characteristics of solar cells when they are illuminated with standard solar radiation, based on a personal computer, is presented.__________Translated from Izmeritel’naya Tekhnika, No. 6, pp. 51–54, June, 2005. 相似文献
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A heterodyne technique is used to characterise the nonlinear response behaviour of microwave pin photodetectors in terms of 3 dB bandwidth reduction and signal distortion of the sinusoidal input/output. Bandwidth reductions from 20 to 2.5 GHz (at 1.6 mW) are observed.<> 相似文献
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Nonlinearities in p-i-n microwave photodetectors 总被引:1,自引:0,他引:1
The nonlinearities in p-i-n photodetectors have been measured and numerically modeled. Harmonic distortion measurements were made with two single-frequency offset-phased-locked Nd:YAG lasers which provide a source dynamic range greater than 130 dB and a 1 MHz-50 GHz frequency range. Carrier transport is analytically described by three coupled nonlinear differential equations, Poisson's equation and the hole and electron continuity equations. These equations are numerically solved to investigate and isolate the various nonlinear mechanisms. The numerical solution incorporates diffusion since our treatment includes carrier generation in the highly doped p-region of the device. This p-region absorption and carrier-dependent carrier velocities associated with a perturbed electric field (due to space-charge and loading effects) are shown to dominate photodetector nonlinear behavior. The numerical model was extended to predict that maximum photodetector currents of 100 mA should be possible in 20 GHz bandwidth devices before a sharp increase in nonlinear output occurs. In addition, second harmonic distortion improvements of 40-60 dB may be possible if photodetectors can be fabricated with strictly-depleted absorbing regions 相似文献
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We present simulation results, based on a one-dimensional p-i-n photodetector model, to explain the reductions in photodetector response observed at high optical powers. The nonlinear effects are attributed to the redistribution of the internal electric field due to space-charge effects created by the photocarriers. The corresponding modification of the position-dependent charge velocities results in high-frequency response reduction, roll-off reduction, and pulse narrowing. Electric field redistribution leads to two dimensional effects, which must be included for accurate modeling of milliampere photocurrents 相似文献
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We present and analyze a hardware-optimized technique that provides true-time-delay steering for broadband two-dimensional array-antenna applications. The technique improves on previous approaches by the reduction of the two-dimensional beam-former architecture complexity, by the provision of flexibility in time-delay unit selection, and by the potential reduction of optical loss. The technique relies on a one-dimensional bank of time-delay units to form the required time-delay gradient for proper off-broadside angle steering. A reconfigurable optical interconnection fabric is used to reassign dynamically the connections between the time-delay units and individual array elements of a two-dimensional array to effect the proper steering angle along the off-broadside cone. 相似文献
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We develop a method for forming squint-free wideband nulls in the antenna pattern of an ultrawideband array antenna. The technique uses an optical dispersive-prism beam former to provide time-delayed microwave signals to each antenna element for forming a squint-free main beam. The amplitude-modulated optical carrier is propagated through a set of optical links. Each link feeds an array element and includes an amount of dispersion proportional to element position. Tuning the wavelength of the optical carrier controls the microwave signal's arrival-time delay gradient across the array. A dispersive-prism tapped delay-line microwave filter is used to frequency shape a nulling signal. The wideband nulls do not significantly distort the main beam and are steered independently of the main beam. The technique is applied to sidelobe nulling for a transmitter and for jammer suppression for a receiver array. 相似文献
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I. A. Goncharenko A. K. Esman V. K. Kuleshov V. A. Pilipovich 《Measurement Techniques》2007,50(9):916-920
A fast optical signal digitization method is proposed based on micrometer ring waveguide cavities; a realization is presented.
Simulation has been applied to the digitization of an analog optical signal with linear intensity change. The sampling frequencies
can attain 1010 per second over a wide spectral range.
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Translated from Izmeritel’naya Tekhnika, No. 9, pp. 11–14, September, 2007. 相似文献