| 摘要 |
Methods and systems for demodulation of open-loop GPS radio occultation signals are provided. An occulted GPS radio signal where the atmosphere-induced modulation on the phase is up to 180 degrees may be recorded by a radio occultation receiver. The radio signal may be concurrently received by a second receiver where the atmosphere-induced phase modulation is below 90 degrees and where the Navigation Data Message (NDM) bit sequence can be readily extracted. The extracted NDM bit sequence may be used to demodulate the occulted GPS radio signal and a 4-quadrant phase extractor may then be used to determine the phase and amplitude of the radio occultation signal. The phase and amplitude modulations after removal of NDM may be used for inversion, e.g., retrieval of the atmospheric parameters such as the bending angle, refractivity and deriving of the meteorological parameters.
|
