I need to design a radar system for my assignment, one task is to generate LFM pulses of width 1.33us increase from 0Hz to 15MHz. Is that possible to use a DDS to do that? How to do that if it is capable? Thanks a lot for your input in advance.
Hi, A DDS is perfect for a LFM application. The following DDSs (AD9910, AD9911, AD9954) have this feature built-in. All you do is program the lower and upper frequency limits using the DRG (digital ramp generator). That's 0Hz and 15MHz in your case. Next program the frequency step size and step rate. If you want the maximun number of intermediate steps between 0Hz and 15MHz in a 1.33us pulse width then program the step rate with a value of 1. A value of 1 for the min step rate equals the SYNC_CLK rate. The SYNC_CLK rate equals 1/4th the internal system clock. The system clock equals the REF CLK input, if the internal PLL is disabled, else the system clock rate equals the output of the internal PLL. If you divide 1.33us / SYNC_CLK rate, it will give you the frequency step size to be entered.
The AD9910 is the most versatile for a LFM operation. You can go the AD9910 product page on the ADI website and download the AD9910 software GUI. The GUI is informative about what the DDS can do. You don't need the evaluation board to run the software once downloaded.
Sorry for the question I am having. Can you please demonstrate using an example the linear sweep from 100-125 MHz at 200 KHz step size and time spent for linear sweeping from 100-125 MHz to be 1 micro second. Can AD9958 or AD9959 be used for this purpose? How much would be the time spent for the linear sweeping from 100-125 MHz for AD9954, AD9854 & AD9910. Can you please demonstrate making this easy to understand to newbie like me who is about to start doing a project on this in my organisation. Quick reply would be highly appreciated.
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