MATLAB: What is the difference between “phased.LinearFMWaveform” and “phased.FMCWWaveform”

fmcwMATLABPhased Array System Toolboxphased array tool boxradar

1. What is the difference between "phased.LinearFMWaveform" and "phased.FMCWWaveform" in Phased Array System Toolbox except for that Triangle waveform generation is possible in P"phased.LinearFMWaveform" function.

2. My other concern is I want to sweep bandwidth of 10Mhz from start frequency of 10 MHz and End Frequency 20MHz. How can i do that in "phased.LinearFMWaveform" function.

3. When i dechirp the received signal from transmitted signal of saw-tooth waveform, i should get 2 beat frequencies (according to "New ideas in FM Radar by H. D. Griffiths"). but i get only 1 beat frequency, why?

Best Answer

Hi Ali,

LinearFMWaveform is a pulse waveform, meaning that in general the system only transmit a very short period of time during one cycle and uses the rest of cycle to receive. On the other hand, FMCWWaveform is a continuous waveform, so the system transmits and receives at the same time and the duty cycle for the waveform is always 1.

Currently you cannot specify the starting and ending frequencies in LinearFMWaveform. However, depending on the system setup, you may still be able to simulate your case. For example, if your system's center frequency is 15 MHz, then your situation is just a symmetric sweeping over a 10MHz range.

I don't have that particular paper handy so I cannot comment much on your third question without seeing some code snippet.

HTH

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The default frqeuency range for the hydrophone is between 0 and 200 kHz. However, in your example, the carrier is set at 300 kHz, so the response is not correctly generated. If you replace the hydrophone definition as

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Your sampling rate is set at fs, which is about 20 MHz, this means your Nyquist is about 10 MHz, regardless what your carrier is, i.e., your signal is aliased. If you want to see 18 GHz at the center, you will have to sample at 36 GHz, this is obviously very expensive. On the other hand, the first step in receiver is normally mix it down so the carrier frequency is really used for transmission, and does not affect the signal processing much (except we need to compensate for RF distortions). This is why we often simply simulate at base band because it captures all the band that interests us.

HTH

Best Answer

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