How to set frequency with EVAL-AD9914

I tested sweeping with EVAL-AD9914.

I want to know how to set frequency using GUI to EVAL-AD9914.

When I set one frequency(1500MHz), the sine out frequency is 1010MHz. (When I set 1000MHz, the result is 672MHz)

My external clock : 122.88MHz (from signal generator)

Below image is my snapshot of GUI.

In other words, how do I get the frequency I set?

  • 0
    •  Analog Employees 
    on Sep 14, 2021 1:30 PM

    When using the internal PLL, the system clock frequency is constrained to 2.4-2.5 GHz (per the data sheet). Notice that the "PLL lock detected" indicator in the GUI is not illuminated. The reason is that the PLL is trying to output 3932.16 MHz, but cannot because the internal VCO can only output frequencies in the range: 2.4-2.5 GHz.

    For your application, the following inequality applies:

    2400 MHz <= 122.88*N <= 2500 MHz, where N is the multiplier.

    The reason you are experiencing a reduced output frequency is because the internal PLL VCO is clamped at its maximum output frequency (~2.65 GHz) and is not able to generate the 3932.16 MHz shown in the GUI.

    Incidentally, when using the internal PLL, the AD9914 cannot provide a 1500 MHz output signal. The reason is the maximum specified PLL output frequency is 2500 MHz, which limits the maximum output frequency to 1250 MHz.

  • Hi KennyG, I got it as follow your guidance. I have a question. I want to skip special frequency so I set Enable Frequency Jump and setting frequency. But the frequency sweep is from 200MHz to 400MHz, no skip special frequency.

    Could you guide me how to resolve this issue?

    Please refer to below image.

  • 0
    •  Analog Employees 
    on Sep 15, 2021 1:07 PM in reply to lupetech

    Unrelated to your question:

    Be aware that there is a software bug when using the DRG. Specifically, in the DIGITAL RAMP GENERATOR window, entries made in the Rising Sweep Ramp Rate (RSRR) and Falling Sweep Ramp Rate (FSRR) boxes are transposed. That is, what you enter in the RSRR box applies to the falling rate and vice versa.

    Regarding the "frequency jump" feature:

    The jump feature only works for uni-directional sweeps (up-sweeps or down-sweeps). That is, bi-directional sweeps (both No Dwell bits set) cannot use the jump feature.

  • Hi KennyG, When I unchecked both or either of them(No-Dwell High and No-Dwell Low), there is no sweep.

    Just AD9914 generate one tone(CW). When I checked both of them, there is a sweep, but no frequency jump.

    Is there a bug of the GUI?

  •  Hi KennyG,

    I did another test without checking No-Dwell High and No-Dwell Low. 

    When I pushed Up and Down button repeatedly, AD9914 has a frequency jump.

    I have a question, could you guide how to generate auto sweep with frequency jump?