Large Antenna Structures Research Articles

Dynamic reliability analysis of antenna reflector accuracy under wind excitation

In this paper the dynamic reliability of antenna reflector accuracy under wind excitation is studied. Based on the assumptions that the wind vibration responses of structures are mutually independent Gaussian stationary processes and the cross points of responses with the boundary are approximately submitted to Poisson process, the formulae of dynamic response of structure under wind excitation are set up and the dynamic reliability of antenna reflector accuracy is analysed. Finally, the computation results of a large antenna structure in engineering are presented.

Limitations of Plasma Charging Damage Measurements Using MOS Capacitor Structures

AbstractThis paper investigates the sensitivity and limitation of capacitor testing for measuring potential charging damage to gate oxides in a given plasma step. While C-V measurements are the most directly related to transistor threshold voltage (Vth) and transconductance (gm), C-V measurements are slow, difficult to automate and not usable for large antenna structures without a fuse link. In contrast, ramp breakdown measurements are quick and easy to automate but lack sensitivity. Charge-to-breakdown offers better sensitivity but with long measurement times. A more promising method is the V-t measurement where the slope dV/dt after initial charging is a measure of the trapping generation rate and is found to be very sensitive to charge damage. The damage sensitivity of this method is high and involves tradeoffs between antenna ratio, testing current and testing time. All of which are critical to damage testing. Leakage measurements are another method which offers short measurement times and high sensitivity. Their limitations are the noise level of the measurement system and the making of good probe contact to the gate material.

Analysis of engineering structures response to random wind excitation

In this paper, based on the present author's earlier study about the random process of wind, the elastic engineering structure response to wind load is analysed by means of the random vibration and finite element method. From the most general model the formulae for calculating the response power spectrum and mean square value of displacement and stress of structure are derived, with which both the static and dynamic response of structures can be obtained simultaneously. Finally, a large antenna structure in engineering is calculated as an illustration. Its response to Davenport's wind load spectrum is given.

Inflatable space structures

The importance of inflatable structures for activities in space is discussed, and their history is described. The changes in structural principles when such structures are used in a zero-gravity environment are highlighted. Technical issues arising for large precision structures, regarding environment, surface accuracy, analysis and electrical properties are considered. A typical large inflatable antenna structure is examined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

New deployable truss concepts for large antenna structures or solar concentrators

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Natural vibration and buckling of general periodic lattice structures

A method is presented for vibration and buckling analysis of arbitrary lattice structures having repetitive geometry in any combination of coordinate directions. The approach is based on exact member theory representing the stiffness of an individual member subject to axial load and, in the case of vibration, undergoing harmonic oscillation. The method is an extension of previous work that was limited to specific geometries. The resulting eigenvalue problem is of the size associated with the repeating element of the structure. A computer program has been developed incorporating the theory, and results are given for vibration of rectangular platforms and a large antenna structure having rotational symmetry. Buckling and vibration results for cablestiffened rings are also given.

Antenna tolerance theory&amp;#8212;A review

The theoretical basis of antenna tolerance theory is reviewed. Formulas are presented for the axial loss of gain and the pattern degradation as a function of the reflector surface rms error and the surface spatial correlation. Methods of determining these quantities by astronomical or ground-based electrical measurements are described. Correlation between the theoretical predictions and the performance of actual large antenna structures is presented.