Capacity and coverage management issues in the forward link of CDMA systems

Abstract

A multisensory approach is being developed at the University of Texas at Arlington (UTA) to improve upon current capabilities in environmental monitoring. These sensors consist of an FT-IR for operation in the near to thermal infrared regions of the spectrum, a long-path UV (LPUV) system and an active/passive millimeter-wave instrument that will operate over the 75-110 GHz window. This report will discuss how we expect the synergistic capability to work and will describe in some detail the design of the millimeter-wave instrument. Field-portable FT-IR instruments have been used effectively to monitor a limited number of gaseous pollutants but are limited by interference from CO₂ and H₂O and, for longer hydrocarbon chains, by spectral overlap. UV instruments, on the other hand, are much more sensitive but many gases do not exhibit spectral absorption (emission) in the UV. It is known that various hydrocarbons, NO[subscript]x, 0₃ and other gases have rotational lines in the 75-110 GHz, and narrow- bandwidth millimeter wave instruments are now being effectively utilized to monitor trace gases in the stratosphere. Use of a wide-bandwidth millimeter-wave system is now being proposed for environmental monitoring at lower altitudes. Aspects of the millimeter-wave system that are considered in this report include antenna and front-end mixer selection, active/passive mode selections and parallel/serial channel tradeoffs. For this instrument 1200°K (cooled) effective noise is expected.