459 research outputs found
Comparison of Analog R-F Photonic Links Using a Variety of Linearized Electro-Optic Modulators
The potential applications of high dynamic range analog r-f photonic links include antenna
remoting, photonic-coupled phased-array antennas, and cable-television transmission. This
paper compares the results obtained with a number of different modulator types and link
configurations and gives recent experimental results. Further details on the analysis and results
for some of the schemes can be found in a review paper that will appear later this year
Intermodulation distortion in high dynamic range microwave fiber-optic links with linearized modulators
Linearization of integrated optic intensity modulators significantly reduces the two-tone intermodulation distortion. The resulting intermodulation distortion produced by these modulators then varies as the input power to the fifth-order link system, the overall intermodulation product is a combination of third-order and higher-order terms. The authors determine the dynamic range of a cascaded microwave network consisting of a preamplifier, a high-dynamic-range fiber-optic link with a highly linear modulator, and a postamplifier. An expression is found that relates the intermodulation power at the output to the relative suppression from the signal level. As an example, a hypothetical 10-GHz low-distortion fiber-optic link that has a dynamic range of 125 dB in a bandwidth of 1 Hz is cascaded with various preamplifiers, and it is shown that the dynamic range of the system is reduced by as much as 20 dB, depending on the third-order intercept of the amplifier
Distortion in linearized electrooptic modulators
Intermodulation and harmonic distortion are calculated for a simple fiber-optic link with a representative set of link parameters and a variety of electrooptic modulators: simple Mach-Zehnder, linearized dual and triple Mach-Zehnder, simple directional coupler (two operating points), and linearized directional coupler with one and two dc electrodes. The resulting dynamic ranges, gains, and noise figures are compared for these modulators. A new definition of dynamic range is proposed to accommodate the more complicated variation of intermodulation with input power exhibited by linearized modulators. The effects of noise bandwidth, preamplifier distortion, and errors in modulator operating conditions are described
Wave-Coupled W-Band LiNbO_3 Mach-Zehnder Modulator
Summary form only given. Mach-Zehnder amplitude modulators have been designed for W-band operation (94 GHz), at a 1.3-μm optical wavelength. These modulators use bow-tie antennas, which are relatively insensitive to DC bias connections made to the ends of the antenna elements. The bow-ties should also give a greater bandwidth than the dipole antennas
Antenna-coupled millimeter-wave LiNbO_3 electro-optic modulator
The phase-velocity mismatch due to material dispersion in traveling-wave LiNbO_3 optical
waveguide modulators may be greatly reduced by breaking the modulation transmission line into short
segments and connecting each segment to its own surface antenna. The array of antennas is then
illuminated by the modulation signal at an angle which produces a delay from antenna to antenna to
match the optical waveguide's delay
60 GHz and 94 GHz antenna-coupled LiNbO_3 electrooptic modulators
Antenna-coupled LiBbO_3 electrooptic modulators can overcome the material dispersion which would otherwise prevent sensitive high-frequency operation. The authors previously demonstrated the concept with a phase modulator at X-band. They have extended this demonstration to a narrowband 60-GHz phase modulator and broadband amplitude modulator designs at 60 and 94 GHz, respectively
Novel Millimeter-Wave Electro-optic Modulator
A waveguide LiNbO_3 electro-optic modulator has been demonstrated with a novel wave-coupling technique which greatly reduces phase-velocity mismatch. An 8-12 GHz version produces 48° phase modulation with 126 mW of drive power. A 60 GHz version is being built
A Study of Broadband Microwave Fiber Optic Links with Linearized Integrated-Optic Modulators
A universally accepted figure of merit for analog microwave transmission links is the spur-free dynamic range (SFDR), which is the ratio (usually expressed in dB) of the largest to smallest signal a link can transmit and receive without introducing any measurable distortion. This paper presents the result of a study of broadband, microwave fiber optic links that contain high- linearity integrated-optic modulators. This study focused on two distinct modulator forms, the dual-parallel Mach-Zehnder modulator and the linearized directional-coupler modulator. Computer simulations were performed to determine how the SFDR was affected by variations of modulator parameters. In addition, the dynamic range and noise figure of links that included preamplifiers were calculated. The results of the link analysis was that the linearized directional-coupler modulator provided the highest SFDR for a broadband microwave fiber optic link
Creative Restitution: A Study of Differential Response Patterns
Creative restitution offers considerable potential to the field of criminal justice. The concept is of historical significance for it has been an important element in a variety of cultures. Yet, the notion of restitution or permitting an offender to make amends is not a significant element in our society. This paper explores the responses of a variety of populations to creative restitution. A number of findings were of significance including strong support for and acceptance of the concept by diverse groups
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Lithium and carbon isotopic fractionations between the alteration assemblages of Nakhla and Lafayette
Nakhla and Lafayette delta 7Li values for samples and extracts (4.1-14.2�) are consistent with brine evaporation. Relatively 13C-poor siderite in Lafayette suggests more than one carbon source was sampled
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