Design method for minimizing RF voltage breakdown

Research study was conducted and results were published. Using principles of similarity and minimum of experimental data, a number of universal curves have been constructed covering wide range of experimental parameters. Gases other than air, such as argon and carbon dioxide, also are included in study

Exchange Rates and the Prices of Nonfood, Nonfuel Products

macroeconomics, exchange rates, prices, dollar, imports

Method for remotely sensing turbulence of planetary atmospheres

Based on variances of log-amplitude and phase fluctuations of radio occultation data received from orbital and fly-by missions, structure constant for Venusian planetary atmosphere has been estimated with high-confidence factor. Analysis indicates that effects of inhomogeneity, finite size, and superrefractivity of atmospheric turbulence cannot be ignored

Low loss dichroic plate

A low loss dichroic plate is disclosed for passing radiation within a particular frequency band and reflecting radiation outside of that frequency band. The dichroic plate is comprised of a configuration of dipole elements defined by slots formed in a conductive plate. The slots are dimensioned so as to pass radiation of a selected frequency and are shaped so as to minimize the relationship between that frequency and the tilt angle of the plate relative to the direction of radiation. The slots are arranged so as to minimize signal power loss due to cross polarization effects

Low-loss, circularly-polarized dichroic plate

Dichroic plate has orthogonally-disposed, loaded dipole apertures with their orientations arranged so as to cancel cross-coupling effects which would otherwise result in power loss to circularly polarized signal

Effects of turbulence in the atmosphere of Venus on Pioneer Venus radio, phase 2

Two problems related to the effects of turbulence in the atmosphere of Venus on the Pioneer entry probe radio link were studied. In the first problem, the cross correlation between the log amplitude and phase fluctuations of the Pioneer Venus communications link is examined. Data show that for fluctuation frequencies above approximately 1 Hz there is little or no correlation. For frequencies below this region the correlation is weak and the square root of the coherence has a peak value close to 0.65. The second problem consists of interferring turbulence characteristics of the Venus atmosphere from the Mariner 5 phase fluctuations. Data show that with the data processing techniques developed and currently available, the phase error due to oscillator drift, assumed trajectory delay, and spline curve fit exceed the turbulence induced fluctuations. Results show that it is not possible to interfere with the turbulence characteristics from Mariner 5 phase fluctuations

Design, modeling, and analysis of multi-channel demultiplexer/demodulator

Traditionally, satellites have performed the function of a simple repeater. Newer data distribution satellite architectures, however, require demodulation of many frequency division multiplexed uplink channels by a single demultiplexer/demodulator unit, baseband processing and routing of individual voice/data circuits, and remodulation into time division multiplexed (TDM) downlink carriers. The TRW MCDD (Multichannel Demultiplexer/Multirate Demodulator) operates on a 37.4 MHz composite input signal. Individual channel data rates are either 64 Kbps or 2.048 Mbps. The wideband demultiplexer divides the input signal into 1.44 MHz segments containing either a single 2.048 Mbps channel or thirty two 64 Kbps channels. In the latter case, the narrowband demultiplexer further divides the single 1.44 MHz wideband channel into thirty two 45 KHz narrowband channels. With this approach the time domain Fast Fourier Transformation (FFT) channelizer processing capacity is matched well to the bandwidth and number of channels to be demultiplexed. By using a multirate demodulator fewer demodulators are required while achieving greater flexibility. Each demodulator can process a wideband channel or thirty two narrowband channels. Either all wideband channels, a mixture of wideband and narrowband channels, or all narrowband channels can be demodulated. The multirate demodulator approach also has lower nonrecurring costs since only one design and development effort is needed. TRW has developed a proof of concept (POC) model which fully demonstrates the signal processing fuctions of MCDD. It is capable of processing either three 2.048 Mbps channels or two 2.048 Mbps channels and thirty two 64 Kbps channels. An overview of important MCDD system engineering issues is presented as well as discussion on some of the Block Oriented System Simulation analyses performed for design verification and selection of operational parameters of the POC model. Systems engineering analysis of the POC model confirmed that the MCDD concepts are not only achievable but also balance the joint goals of minimizing on-board complexity and cost of ground equipment, while retaining the flexibility needed to meet a wide range of system requirements

Near-field spectroscopy of bimodal size distribution of InAs/AlGaAs quantum dots

We report on high-resolution photoluminescence (PL) spectroscopy of spatial structure of InAs/AlGaAs quantum dots (QDs) by using a near-field scanning optical microscope (NSOM). The double-peaked distribution of PL spectra is clearly observed, which is associated with the bimodal size distribution of single QDs. In particular, the size difference of single QDs, represented by the doublet spectral distribution, can be directly observed by the NSOM images of PL.Comment: 3pages, 3figue

Interplay of disorder and geometrical frustration in doped Gadolinium Gallium Garnet

The geometrically-frustrated, triangular antiferromagnet GGG exhibits a rich mix of short-range order and isolated quantum states. We investigate the effects of up to 1% Neodymium substitution for Gallium on the ac magnetic response at temperatures below 1 K in both the linear and nonlinear regimes. Substitutional disorder actually drives the system towards a more perfectly frustrated state, apparently compensating for the effect of imperfect Gadolinium/Gallium stoichiometry, while at the same time more closely demarcating the boundaries of isolated, coherent clusters composed of hundreds of spins. Optical measurements of the local Nd environment substantiate the picture of an increased frustration index with doping.Comment: 5 pages, 5 figure