| 摘要 |
The present system for determining the phase and amplitude of a radio occultation signal modifies the traditional Open Loop tracking process to maximize the signal-to-noise ratio, minimize the sampling rate, and also preserve the structure of the radio occultation signals. A radio occultation system includes a transmitter system, a receiver system, and a post-processing system. The receiver system receives the radio signal that is transmitted by the transmitter system through the earth's atmosphere, where it is occulted, and down converts the received radio occultation signal to generate a down converted signal based on a phase model that uses a refractivity climatology. The receiver system then low pass filters the down converted signal and samples the in-phase and quadrature components of the down converted and low pass filtered signal. The post-processing system receives the in-phase and quadrature components of the down converted and low pass filtered signal, determines the mean residual frequency, and performs additional down conversion of the sampled signal to eliminate aliasing. The post-processing system then re-samples the down converted signal at a higher sampling rate and calculates the accumulated phase and amplitude from the re-sampled signal.
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