I have a plan to make a chirp signal which has 500MHz frequency sweep range with less than 10ms time interval (with positive slope).The range of the sweep frequency could be 0-500MHz or 1.0GHz-1.5GHz. I want to know that this kind of signal can be generated by AD9914.
Yes, the AD9914 can generate a 10ms sweep from 0-500MHz or 1-1.5GHz (assuming a 3.5GHz sample rate).
However, sweeping as high as 1.5GHz will be a challenge because the maximum sample rate of 3.5GHz puts the Nyquist frequency at 1.75GHz. Assuming you plan to use a reconstruction filter at the output of the AD9914, the filter must sufficiently roll off from 1.5GHz to 1.75GHz. Such a steep roll off requirement will be challenging to implement.
I follow up with another question on this subject.
I can generated a sweep, but want to use an input signal to start the sweep and to have an output signal indicating when the sweep is finished. Which pins do I use for this, and which bits in teh registers must be sat?
The AD9914's digital ramp generator (DRG) indicates the end of a sweep via the DROVER pin (see data sheet pg. 27).
Triggering a sweep via a single external trigger signal will take some creativity. The reason is the DRG triggers under a number of conditions related to the IO_UPDATE pin and the DRCTL pin. Furthermore, the function of the DRCTL pin varies depending on how you set the "no-dwell" bits (see data sheet pgs. 25-26).
Thank you Kenny,
I have read the datasheet once more and it seems to be ok to do this. I am using the eval-kit and plan to connect the input start trigger signal to J105 (DRCTL). The R134 must be removed. Then I use the AD9914 software to set the sweep and the the No-dwell bit in CFR2 high. By connecting a signal generator with a 1kHz signal to J105 this should start the sweep on the rising edge once every 1ms. The DROVER signal goes high after 400us when the sweep is finished. Do you agree?
Assuming you mean No-dwell high, then it should work as you state.
Under the No-dwell high condition, the device only pays attention to the rising edge of DRCTL (the rising edge of your "trigger" input). The DROVER pin should assert at the end of the sweep. Assuming you have programmed the sweep parameters for a 400us sweep period, then you should see DROVER assert 400us after the rising edge of DRCTL.