An UHF frequency-modulated continuous wave wind profiler - receiver and audio module development
Tutor / director / evaluatorFrasier, Stephen J.
Document typeMaster thesis (pre-Bologna period)
Rights accessOpen Access
The measurement of winds and processes taking place in the atmosphere is a fun- damental requirement in both research and operational meteorology. This project is focused on the processes taking place in the lower troposphere called the atmospheric boundary layer (ABL). The ABL is important meteorologically in terms of assessing of convective instability. The entrainment zone at the top of the ABL acts as a lid on rising (and cooling) air parcels due to the temperature inversion. An external mechanism such as geographically forced uplift, vigorous surface heating or drylines, can break the entrainment layer, allowing the capped air parcels to rise freely. As a result, vigorous convection will begin producing severe thunderstorms. ABL research and studies help (i) develop and improve existing numerical weather prediction models, (ii) understand the transfer of hear, water vapor and momentum between the Earth and the atmosphere, (iii) re ne the analytical description of tur- bulent processes and (iv) quantify the absorption and emission in the troposphere, which is a major factor in shaping climate on Earth. The e ect of the troposphere on wave propagation has also been studied extensively for the purposes of improving radio communications.The main reason for the radar development is the need of continous monitoring of the winds and elds in the atmosphere, improving the in-situ measurements. Conven- tional radar pro ler technologies usually are able to make atmospheric measurements of the boundary layer, but precluding the lower part of the ABL, (around 150 meters). The Frequency Modulated Continuous Wave, Spaced Antenna (FMCW-SA) Radar, that is being developed in University of Massachusetts - Amherst, at the Microwave Sensing Laboratory (MIRSL), will allow measurements of the lower part of the ABL. The use of FMCW radars is introduced in order to improved the limitations of pulsed radars. Pulsed radars are limited by the pulse-width and switching speed of the transmit-receive switches because of the use of a common antennas for both functions. The pulsed nature of the radar dictates a high transmitter power, and consequently the need for switches that are both faster and high powered. FMCW radar alleviate this problem by using separate antennas for transmit and receive, also being able to be used at short ranges. The problem in dual-antenna systems is parallax at low altitudes due to the spatially separated antenna apertures, and some uncertainty in the actual sampling volume. The primary objective of this thesis, is to explain the previous results and the problems encountered on the FMCW Wind Pro ler Radar, and to provide a detailed account of the work one in order to x remaining issues. Several problems were encountered on the radar's receiver. Noise and leakage were still not allowing the radar to achieve sensitivity enough to work properly. To solve it, the receiver was modi ed. This thesis, provides a detailed account of modi cations including a new audio-module, modi ed FPGA and tests to report conclusions.
Projecte final de carrera fet en col.laboració amb University of Massachusetts - Amherst, the Microwave Sensing Laboratory (MIRSL)