12. 540 Principles of the Global Positioning System Lecture 16 Prof. Thomas Herring 04/08/02 12.540Lec16
04/08/02 12.540 Lec 16 1 12.540 Principles of the Global Positioning System Lecture 16 Prof. Thomas Herring
Propagation: ionospheric delay Summary Quick review/introduction to propagating waves Effects of low density plasma Additional effects Treatment of ionospheric delay in GPS processing Examples of some results 04/08/02 12.540Lec16
04/08/02 12.540 Lec 16 2 Propagation: Ionospheric delay • Summary – Quick review/introduction to propagating waves – Effects of low density plasma – Additional effects – Treatment of ionospheric delay in GPS processing – Examples of some results
Microwave signal propagation Maxwell's equations describe the propagation of electromagnetic waves( e.g. Jackson Classical Electrodynamics, Wiley, pp. 848 1975) 4丌r1aD V·D=4npV×H=-J+ at I aB V●B=0 V×E+ 0 c a 04/08/02 12.540Lec16
04/08/02 12.540 Lec 16 3 Microwave signal propagation • Maxwell’s Equations describe the propagation of electromagnetic waves (e.g. Jackson, Classical Electrodynamics, Wiley, pp. 848, 1975) ∇ • D = 4πρ ∇ × H = 4 π c J + 1 c ∂D ∂t ∇ • B = 0 ∇ × E + 1 c ∂B ∂t = 0
Maxwells equations In Maxwells equations E= Electric field; p=charge density; J=current density D= Electric displacement D=E+4TP where P is electric polarization from dipole moments of molecules Assuming induced polarization is parallel to E then we obtain D=EE. where s is the dielectric constant of the medium B=magnetic flux density(magnetic induction H=magnetic field; B=uH; u is the magnetic permeability 04/08/02 12.540Lec16
04/08/02 12.540 Lec 16 4 Maxwell’s equations • In Maxwell’s equations: – E = Electric field; ρ=charge density; J=current density – D = Electric displacement D = E+4 π P where P is electric polarization from dipole moments of molecules. – Assuming induced polarization is parallel to E then we obtain D = ε E, where ε is the dielectric constant of the medium – B=magnetic flux density (magnetic induction) – H=magnetic field; B = µ H; µ is the magnetic permeability
Maxwells equations General solution to equations is difficult because a propagating field induces currents in conducting materials which effect the propagating field Simplest solutions are for non-conducting media with constant permeability and susceptibility and absence of sources 04/08/02 12.540Lec16
04/08/02 12.540 Lec 16 5 Maxwell’s equations • General solution to equations is difficult because a propagating field induces currents in conducting materials which effect the propagating field. • Simplest solutions are for non-conducting media with constant permeability and susceptibility and absence of sources