What defines a negative sweep waveform?

A negative sweep waveform is characterized by its specific relationship to timing and signal generation in radar technology. The correct answer describes a rectangular waveform whose negative pulse-width correlates directly with the sweep time of the reference sweep signal. This correlation is crucial because the sweep time determines how long the radar signal is emitted and then listened for echoes from target objects. When the waveform has a defined negative pulse-width linked to the reference sweep, it means that the radar is effectively capturing and processing the time taken for signals to return after hitting an object, allowing for accurate distance measurements.

In contrast, the other choices do not accurately capture the essence of a negative sweep waveform in the context of radar systems. A waveform with parameter changes based on the target might describe something variable but does not specifically define the characteristics of a negative sweep waveform. Similarly, a continuous signal used for measuring speed does not pertain to the discrete timing and pulse-width relationships that define a negative sweep. Lastly, a signal that lacks a representation of any time variable fails to align with the operational nature of radar waveforms, which fundamentally depend on timing to provide critical information about detected objects.