frequency chirp 该怎么理解？

chan

在ADS HELP中对脉冲功率源PtRF_Pulse 做的解释：
1，This RF pulse power source creates a pulse modulated RF carrier with optional frequency chirping. The carrier frequency at the start of the pulse is defined by the Freq parameter. For envelope simulation, Freq identifies the closest analysis frequency. If the frequency is not close enough to an analysis frequency, a warning is issued and the source output is set to zero for that analysis

2，The additional frequency chirp is referenced to the frequency value at the Delay time point where the pulse first starts turning on. The chirp rate is calculated by dividing the Chirp parameter by the sum of Width, Rise and Fall time. The Chirp value then represents the amount of frequency shift over the full, extended pulse width. If OffRatio is not 0, this same chirp rate will continue until the next pulse starts, when it is reset to the Freq value.
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