| 21. | The tone is modulated using frequency shift keying.
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| 22. | In this approximation, the frequency shift is not affected by the direction of the optical radiation.
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| 23. | As a result, the frequency shift arises.
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| 24. | To pick up moving targets, the radar looks at the Doppler frequency shift of the returned signal.
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| 25. | The frequency shift can be calculated, by:
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| 26. | The only effect in known physics that can cause a uniform frequency shift is the Doppler effect.
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| 27. | A frequency shift keying ( FSK ) signal is alternating between two waveforms, and allows passband transmission.
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| 28. | This gravitational frequency shift is noticeable.
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| 29. | However, non-linear sweeps have to be used with caution when target returns are affected by Doppler frequency shifts.
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| 30. | Frequency is folded for high speed targets where radial velocity produces a frequency shift above the Nyquist frequency.
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