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FFT Bit Templating – A Technique for Making Amplitude and Frequency Measurements of a BPSK Modulated SignalShockey, Bruce 10 1900 (has links)
International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In many spacecraft receiver applications, the Fast Fourier Transform (FFT) provides a powerful tool
for measuring the amplitude and frequency of an unmodulated RF signal. By increasing the FFT
acquisition time, tiny signals can be coaxed from the noise and their frequency measured by
determining which frequency bin the signal energy appears. The greater the acquisition time, the
narrower the bin bandwidth and the more accurate the frequency measurement.
In modern satellite operations it is often desirable for the receiver to measure the frequency of a
carrier which is modulated with BPSK data. The presence of the BPSK data limits the FFT
acquisition time since the signal may switch polarities a number of times while the FFT samples are
being acquired. This polarity switching spreads the signal energy into multiple frequency bins
making frequency measurement difficult or impossible. The Bit Templating Technique, used for the
first time in the CMC Electronics Cincinnati TDRSS / BPSK Spacecraft Receiver, collects the
modulated waveform energy back into a signal bin so that accurate amplitude and frequency
information can be calculated.
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