# phased.FMCWWaveform generate wave without carried frequency

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peng dahui el 16 de Feb. de 2022
Editada: Sudarsanan A K el 22 de En. de 2024
hi! i found a question using phased.FMCWWaveform. the start frequency of the wave is 0Hz just like in the pic( https://ww2.mathworks.cn/help/examples/radar/win64/FMCWExample_01.png ). i know that it will need many computer hardware if we set a high start frequency like 77GHz and the example( https://ww2.mathworks.cn/help/radar/ug/automotive-adaptive-cruise-control-using-fmcw-technology.html ) just use the function tool and make a good simulation result. i am very puzzled that how the example can get a good result since the dechirp signal contains fc(carried frequency) information. fc not only influent propagation but also determine the dechirp signal. According to the theoretical derivation,we can get doppler frequency(fd=-2fc*R/c). as we all know,the fc in wave generated by phased.FMCWWaveform is 0,so the doppler frequency is 0? how does the example get a nice result? thanks for helping me solving the question.
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NoYeah el 24 de Mzo. de 2023
This is why we have to kick off the MATLAB

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### Respuestas (1)

Sudarsanan A K el 22 de En. de 2024
Editada: Sudarsanan A K el 22 de En. de 2024
Hello Peng,
In MATLAB simulations using "phased.FMCWWaveform", the carrier frequency () is typically not modeled because it does not influence the outcome of the simulation. The function generates a chirp signal used to determine the range and velocity of targets in FMCW radar systems.
The beat frequency, which is crucial for measuring target information, is derived from the transmitted and received signal frequencies. Since the carrier frequency cancels out during signal processing (dechirping), it's not required in the simulation to obtain accurate results for the target's range and velocity.
The Doppler frequency () is given by:
where 'v' is the target's velocity, and 'c' is the speed of light. The carrier frequency () is assumed to be part of the radar system but does not need to be explicitly included in the simulation.
Thus, the MATLAB example can generate accurate results without specifying a high carrier frequency like .
I hope this helps!
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