Papers by Keyword: Propagation Loss

Abstract: In this paper, the effect of environment and altitude on ultrahigh frequency (UHF) band has been studied. Both theoretical study and experimental investigations are conducted in order to model and characterize such complex communication medium. The experimental study is primarily aimed at critically analyzing the detrimental impact of channel condition on received power in hilly environment under different altitudes. The propagated signal strength varies from one place to another due to time varying channel condition as a result of obstacles between the transmitter and receiver. There is dramatic need to experimentally investigate such scenario in order to provide an avenue through which service providers can strategies their policies for effective wireless communication. Developing such channel models is extremely useful in communication systems design and simulation. The proposed model has been compared with ITU-R model for verification of the develop model for propagation loss prediction in hilly environment. The results obtained are compared with different measurement at various altitudes in hilly terrain environment.

Abstract: The influence of the microwave propagation in the evaporation duct is studied by solving wide angle parabolic equation using Fast-Fourier transform method. Then, the result under smooth surface is compared with the simple and complex obstacle on the surface. It is shown that the propagation loss of electromagnetic wave will increase in evaporation duct with increase of the propagation path and the height obstacle, which effectively improves its remote propagation in waveguide after diffracting.

Abstract: Zinc sulfide (ZnS) thin films as the waveguide medium have been deposited onto oxidized silicon wafer substrates at cold temperature (Tcold = –50oC) and ambient temperature (Tambient = 25oC) by thermal evaporation technique. The surface morphology of ZnS films were pictured with an atomic force microscopy (AFM) and the surface roughness were calculated from the AFM images. The propagation losses of the samples were measured using a scanning detection technique attached to a prism coupler. The AFM results revealed that the surface of cold deposited ZnS film is rougher than the surface of ambient deposited ZnS film. The propagation losses of the cold deposited ZnS waveguide are consistently lower than the ambient deposited ZnS waveguide at all measured wavelengths.

Abstract: Zinc sulfide (ZnS) waveguides with the thickness of 0.5 μm have been deposited onto oxidized silicon wafer substrates at cold temperature (T_cold = –50°C) and ambient temperature (T_ambient = 25°C) by thermal evaporation technique. The propagation losses of ZnS waveguides were determined by a scattering detection method. The propagation losses of cold deposited ZnS waveguide were 20.41, 11.35, 3.51 and 2.30 dB/cm measured the wavelengths of 633, 986, 1305 and 1540 nm, respectively. Where as, the propagation losses of ambient deposited ZnS waveguide were 131.50, 47.99, 4.43 and 2.74 dB/cm measured the wavelengths of 633, 986, 1305 and 1540 nm, respectively. The propagation loss of the cold deposited ZnS waveguide was dominated by surface scattering whereas the propagation loss of the ambient deposited ZnS waveguide was dominated by bulk scattering.