How can i generate pulsed FM signal (chirp) sweeping from 21MHz to 25MHz using AD 9854.Please suggest the steps to program AD 9854 evaluation module.
There's a lot of flexibility as to what you can program for the automatic IO update rate, the ramp rate, and when you want to stop the sweep that there's no set answer. The simplest I can think of is to start the sweep on one IO update pulse and to end it on the next IO update pulse that comes along by writing and setting CLR ACC 2 sometime in between the two pulses. You would set the IO update rate to equal how long you want the sweep to take. The delta frequncy would be the frequency range divided by the number of steps you want it to go through. And last the ramp rate would equal the IO update rate divided by the number of steps.
Some equations from the datasheet you'll need...
IO Update Rate = (N + 1) * SYSCLK_Period * 2
Ramp Rate = (N + 1) * SYSCLK_Period
Frequency = (N / 2^48) * SYSCLK_Frequency
Where N is the decimal value of the associated register.
For example, say you want the time to sweep to be 5ms long and for it to go through 1000 frequency steps. You would program the IO_Update rate register to 0x000752FF (5ms). The delta frequency register would be 0x000150867C3F (4kHz). The ramp rate register would be 0x0000EF (5us). Finally, the start frequency register would be 0x1C0000000000 (21MHz).
Since this question relates to the AD9854 DDS, I have moved it to the Direct Digital Synthesis Community. Someone here should be able to assist you.
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Information on Chirp Mode starts on page 24 of the datasheet with 'Basic FM Chirp Programming Steps' on the following page. Do you need more information than this?
As part of my project work,I need to make a transmitter, transmitting chirp signal(21MHz-25MHz), using the ad9854 evaluation module available in our lab.Ref.clk given is 32MHz*6=192MHZ,Internal I/o update clock is used,but i was not able to interrupt the chirp at 25 MHz.Sir how can i control the sweep range between 21MHz to 25 MHz?Kindly answer me with a proper solution.
i am very much thankful to you.With the above suggestions i was able to generate the pulsed FM signal using ad9854.Now i am trying to design a proper receiver.Can you please suggest a way to decompress the pulse and to extract the information.Hope you will do the needful.Thanks in advance
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