The effect of I,Q mismatch errors on adaptive cancellation

The effects of in-phase (I) and quadrature-phase (Q) amplitude errors and low-pass-filter (LPF) errors on adaptive cancellers are investigated. I,Q errors occur because of errors in the synthesis process of the mixers and LPFs designed to be identical for each input channel. These I,Q errors among the channels result in cancellation degradation. Tapped delay line transversal filters have been proposed as a way to compensate for these errors and thus improve cancellation performance. However, it is shown that if there is any LPF mismatch, then transversal filtering has a small effect on improving canceler performance. The use of individual I,Q adaptive transversal filter weighting is suggested as a means of completely eliminating the phase amplitude errors, and making the canceler performance responsive to transversal filter compensation     

Responses of the upper middle atmosphere (60–110 km), to the first two stratwarms of map (1982/3, 1983/4)

The global developments of the stratospheric events (～20–50 km) are briefly described using balloon and satellite data. Winds data from L.F. drift (52°N, 15°E, Europe) for heights of 90–100 km, and from M.F. radar (52°N, 107°W, Canada) for heights of 60–110 km are then compared with the stratospheric morphology.Data for 1982/3 and 1983/4 show that the planetary wave activity and warmings produced strong westward and southward perturbations in the radar winds. Satellite data from 0.1, 0.01 hPa are consistent with these winds; and also show smaller scale structures in the mesosphere than the stratosphere. The semi-diurnal tide responded strongly to the atmospheric disturbances in Europe and Canada: for the latter vertical wavelength changes occurred for heights of 70–100 km. However the correlation between these tidal fluctuations was not high indicating that the tidal adjustments were continental rather than hemispheric.     

Designing space vehicle shields for meteoroid protection: A new analysis

Dual-layer meteroid shields consisting of sacrificial bumper plates spaced some distance outboard from the vehicle hull are the most effective structures yet conceived for protecting space vehicles from supervelocity meteroid impacts. This paper presents a new analysis for designing dual-layer shields. The analysis is based upon energy and momentum conservation, fundamental electromagnetic radiation physics, and observation of results from extensive experimental impact investigations conducted at relatively low velocities (near 7 km/s). One important conclusion is that most of the kinetic energy of a meteoroid striking a dual-layer shield is expended as radiation at the stagnation zone on the face plate of the underlying structure. The analysis includes systematic procedures to evaluate the response of shield designs for a given impact threat. Similar applications of the analysis can be used to support a mathematically rigorous procedure for optimum shield design. The research described here supported the Halley Intercept Mission Project at the Jet Propulsion Laboratory, C.I.T., under Contract No. NAS 7–100, sponsored by the National Aeronautics and Space Administration.     

Synoptic observations of coronal transients and their interplanetary consequences

A small coronagraph has been placed in orbit to monitor the sun's outer corona from 2.5 to 10.0 solar radii, and five years of nearly continuous synoptic observations have now been completed. Rapid and sensitive image processing techniques have been developed to screen the data for transient phenomena, particularly coronal mass ejections (CMEs). About 50,000 coronal images have been examined, out of a five-year total of 68,000, and a standardized listing of more than 1,200 coronal transients for the period 1979–1982 has been prepared. These data have been analysed in the light of other available information, particularly on conditions in the interplanetary plasma. The dynamical characteristics of the active corona, as they are beginning to emerge from the data, are presented. We find that coronal mass ejections exercise significant influence on the interplanetary solar wind. They are the source of disturbances that are frequent and energetic, that tend to be somewhat focussed, that often reach shock intensity, and that propagate to large heliocentric distances, sometimes causing major geomagnetic storms.     

Charges on dust particles

We discuss the potential (charge) on dust particles in various environments. We first consider the classical case of a single isolated dust particle. In conditions which apply to planetary dust rings, the exact value of the dust potential depends critically on several effects (e.g. secondary electron emission, photoelectric efficiency) which are not well known for small dust particles of relevant material and surface conditions. In dust clouds of high dust densities the classical approach fails to give the correct value of the dust potential due to the neglect of collective effects. In terms of an ordering parameter P = a_μN_d0/n₀ (dust radius in microns × cloud dust density/exterior plasma density) the collective effects on the dust potential become apparent at P ～ 10^?6. For increasing values of P the collective effects increase, whence the dust potentials decrease and eventually approach zero.     

Conopulse Radar Angle Tracking Accuracy

An analysis is given of the tracking accuracy of a conopulse radar that angle-tracks on target echo pulses. The analysis includes effects of noises in both sum and difference channels, the effect of the tracking range gate's duration, and applies to any shape of radio frequency (RF) pulse envelope. For large single-pulse signalto-noise ratio and any shape of RF pulse envelope, accuracy approaches the theoretical accuracy of a conopulse system when a short-duration range gate is used. The inportant case of rectangular RF pulses is solved in detail.     

Geometric aspects of long-term noncoherent integration

Long-term integration is defined as integration, perhaps interrupted, over time periods long enough for targets to move through volumes in space resolvable by the radar. Because the motion of the target is unknown prior to detection, long-term integration must be performed along multiple paths representing plausible target paths. The geometry of such a set of integration paths affects detection performance in several ways. The simplest implementation of long-term integration, using constant radial velocity paths, is investigated. The effects of path geometry on detection is quantified and optimized for a target whose motion is nearly radial but otherwise unknown     

International trends in Stirling engine technology development:ISEC 1982-8

A brief survey is presented of trends in work reported at four International Stirling Engine Conferences held during the 1980s. The discussion covers international participation, publication sources and types, engine types, specialized engines, sponsoring institutions and observed trends