Methodology development for thermal analysis of space power microwave rectifying antennas (rectennas).

摘要

Beaming power at microwave or millimeter wave frequencies is a means of transmitting power in air or vacuum. The reception and DC power conversion device is called a rectenna (element). To date rectennas have been designed either for powering aircraft or for solar power satellites. Use of rectennas in space missions will entail incident power densities greater than previously envisioned. This, coincident with absence of convective energy dissipation may result in temperatures above design limits. Thus it is necessary to predict the temperatures both globally (spatially) and locally (detailed) for rectenna element arrays. In this thesis such a methodology is developed with specific numerical results typical of space missions in earth orbit, including incident solar and albedo fluxes and radiative heat dissipation to 0 K.; A rectenna is comprised of subarrays, and in turn single unit cells--the smallest repeating element. The unit cell contains a diode which converts incident microwave to DC; inefficiencies result in a localized heat source. The heat conduction equation is solved numerically in this unit cell. Since the unit cell boundaries are not coincident with the lines of symmetry, the solution is also obtained by "shorting" the cell boundaries. This provides the local solution, but to provide the global solution (including Joule heating) the heat conduction equation is solved for a three unit cell array. These analyses are performed for both a detailed 3D and simple quasi 1D representation.; Comparing results of the detailed and simple representations for a unit cell, a shorted unit cell and a three unit cell array; a methodology is developed and demonstrated to be accurate for arbitrary size arrays. These calculations were performed for a 2.45 linear polarized (LP) rectenna.; The major conclusions are: the methodology developed is general and can readily be applied to the thermal design of higher frequency rectennas, where the temperature calculation is critical; and 2.45 LP rectenna diode temperatures are excessive and this rectenna needs to be redesigned.