Development of an intelligent receiver for a planetary probe

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The objective of this research is to develop an intelligent receiver which efficiently transmits wave data observed by an earth satellite and planetary probe.Development of data compression method and its evaluation was performed by an prototype of an intelligent receiver which composed of an IBM/PC compatible board computer, A/D converter, Digital Signal Processor (DSP), etc in 1997. An data compression method by variable block-length subband coding is developed, its compression rate and processing speed for various waveforms observed by the Geotail satellite using CPU and/or DSP were evaluated, and its usefulness was confirmed.A sweep receiver for the intelligent receiver using Digital Down Converter (DDC) was developed in 1998. The DDC digitally convert a frequency of A/D converted data to a lower frequency. First, observed frequencies are converted to a analytic signal of a *50kHz bandwidth whose center frequency is equal to a local frequency. This converted waveform can be efficiently sent by the data compression method shown above. Their frequency spectra can be analyzed using the Fast Fourier Transform (FFT). A frequency analyzer for frequencies up to 2MHz with about 200Hz resolution has been developed and can process data several tens times faster than the analog-type Geotail sweep receiver (SFA).A high resolution and high speed frequency analyzer and data compression methods have been developed successfully. These results could be used for planetary probes in the future.