Wave Wireless Systems Research Articles

Gravity waves of short period (5–90 min), in the lower thermosphere at 52°N (Saskatoon, Canada); 1978/1979

Winds data from a partial reflection radiowave system have been obtained from six 3 h soundings from August 1978 to June 1979. Radar returns from 52 to 118 km are sampled at 3 km intervals, and wind profiles are calculated every minute: waves with frequencies as high as the Väisälä-Brunt frequency (τ≈ 5 min) may be resolved. Time-series and spectral analyses are used to identify internal gravity (I.G.) waves (5≲τ≲90 min); short period waves are present in all seasons. Wave amplitudes are similar in four soundings, but are smallest in the April and largest in the January sounding. Polarization of the waves is evident during most soundings, consistent with the absorption or reflection of I.G. waves with phase velocities parallel to the mean flow. The autocorrelation functions of the reflected radiowaves (amplitude) are used to calculate a turbulent velocity parameter, and also the related energy dissipation rate from ~ 70–100 km: values of 0.1 W kg −1 are typical and peaks of ~ 0.2 W kg −1 occur. Again, largest values occur in the January sounding, smallest in the April sounding. The variation of I.G. wave energy density with height is also used to calculate an energy dissipation rate, and the good correspondence between profiles of these two estimates indicates the important role of I.G. waves in the creation of turbulence. Eddy diffusion (vertical) coefficient profiles are shown: values near 85 km are typically 2–6 × 10 2 m 2 s −1.

Radiowave Liquid Metal Media Level Sensors for Metallurgical Plants

The paper is concerned with development of reliable and easy-to-operate level sensors for liquid metal media, a major ingredient of metallurgical process control. Liquid metal level sensors can be developed which employ the radiowave method. Some properties and characteristics of radiowave systems are cited that are made of sections of transmission lines, waveguides, and aerials used in design of sensors. The sensors find their way into various vessels such as electric slag remelt and continuous ingot casting crystallizers and intermediate vessels. Industrial tests of pilot sensors proved that their design principles are sound.

Some physical constraints on the use of "Carrier-free" waveforms in radio-wave transmission systems

Are there practical applications in radio-wave transmission of inherently broad-band "carrier-free" waveforms such as Walsh functions? We demonstrate in this paper that the band-limiting constraints of radiating systems limit mission of the low-frequency spectral components of such waveforms and severely restrict the radiation directivity that may be achieved in systems that employ them. We also find that dispersion in the propagating medium poses difficulties for the use of such waveforms, and we present an example that illustrates their impracticality in a case in which medium-related limits on coherence bandwidth are of concern. Considerations of capital cost, reliability, and maintenance militate against the use of these waveforms and in favor of conventional spread-spectrum modulation schemes where such service is required. Troublesome aspects of engineering analysis methods for systems employing such modulation schemes are also exposed, as are some practical and economic difficulties to be expected if they are to be introduced as co-users of the electromagnetic spectrum with conventional radio systems.

Comparisons between time variations in D-region winds and electron densities at Saskatoon, Canada (52°N; 106°W)

A partial reflection radiowave system (2.2 MHz) has been used at Saskatoon, Canada (52°N, 106°W; L = 4.4) to obtain electron densities (~65–85 km) by the differential absorption experiment, and winds (52–118 km) by the spaced antenna drifts experiment. These data have been compared during the winter (December–March) of 1974/75, eleven selected days during January and February of 1976, and during 10 days in each of the four seasons of 1976. There is consistent evidence for a correspondence between increasing ionization and decreasing northward or increasing southward winds, during winter months. This is consistent with the hypothesis that nitric oxide (NO), created during magnetic storms by the associated auroral activity, contributes to electron density variability by way of circulation changes and atmospheric waves. It has not been possible to distinguish between a latitude gradient of NO or isolated accumulations of this minor constituent.

Winds and Wave Motions to 110 km at Mid–Latitudes I. Partial Reflection Radiowave Soundings, 1972–73

Abstract Measurements of winds (60–110 km) for Saskatoon, Canada (52N, 107W), have been obtained from a partial reflection radiowave system. Closely spaced atmospheric soundings (12 per hour) for heights between 51–117 km with 3–km height resolution, were made between August 1972 and September 1973. The median of the wind profiles for a given hour has been identified mainly as the prevailing wind, and the irregular components from each profile as internal atmospheric gravity waves (30<τ<60 min, 12<λ<30 km). The amplitudes and shears of the irregular winds have their largest values in winter. A diurnal variation has been found, showing a minimum in amplitude and shear values near noon for all seasons; this variation is especially noticeable above 90 km. Comparisons of seasonal variations in the prevailing zonal and meridional winds, with the amplitudes of the irregular winds, suggest interactions involving critical layers and momentum transfer. Tropospheric weather systems are considered in relation to the...

Electron Precipitation at an Auroral Latitude – Saskatoon, L = 4.4. I. Photometer, Magnetometer, and Radiowave Data

A study of the quiet and disturbed lower ionosphere (60–100 km) near solar maximum years (1970–1971) has been carried out at Saskatoon (52 °N, 106 °W, L = 4.4) using a variety of techniques: a 5577 Å photometer, a magnetometer, a 'partial reflection radiowave system' (2.2 MHz), and an all-sky camera. Good correspondences between local and planetary magnetic disturbances and the green line intensity I(5577 Å) have been found. Radiowave data, ordered in terms of I(5577 Å), have been used in seasonal epoch analyses for the four seasons. It is shown that after the photometric maxima near geomagnetic midnight, ionospheric disturbances below 80 km continue to increase in magnitude towards sunrise. They are evident until at least noon the following day. For a given level of I(5577 Å), the ionospheric disturbance (&lt; 90 km) is largest during the night hours in summer and winter; and after sunrise, largest in winter and fall months. There is good general correspondence between these results, and fluxes of precipitated electrons measured by satellite techniques.

Winds and wave motions (70–100 km) as measured by a partial reflection radiowave system

Sequential wind profiles (spaced by ⩾6 min) are obtained by the D 1 method, using partial reflections, for heights from 70–100 km. Simultaneous photographs of the ‘echo structure’ are used to interpret these data. It is shown that when allowance is made for echo distribution effects, profiles of small angular uncertainty ( Δφ < 45°) and high internal consistency are obtained. Irregular components of the wind are derived by differencing sequential profiles (spaced by 6–60 min), and parameters which are often consistent with those of internal atmospheric gravity waves are obtained (wave amplitudes ⩽50 m/sec; λ z , 10–20 km; τ, 40–120 min; shears, 10–50 m/sec/km). The direction of vertical phase progression is somewhat ambiguous, but some evidence for a standing mode and a downward propagating mode is presented. Some comments are made about comparisons between D 1, D 2 and rocket techniques.

Noise considerations on toll telephone micro wave Radio systems

Noise considerations on toll telephone micro wave Radio systems