AD9959 UNLOCK Low Frequency Output 1Hz

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    Gra Afch

    AD9959 UNLOCK Low Frequency Output.
    To remove the lower frequency limit of 100kHz. For example, take RF OUT2 DDS9959. To do this, you need to take the following steps:
    1. Remove (unsolder) transformer T2.
    2. In place of the Footprint T2, you need to install the capacitor C1 = 10uF 10…16V 0805 and 2pcs Resistor 51 Ohm 0603. Here is a draft of the diagram below and the location of the components on the board.
    3. If you need to get a low frequency on another channel, for example, on RF OUT0, then you need to remove (unsolder) the transformer T0 and do steps 1 and 2.

    What will we get?
    1. The lower frequency limit is about 3-5Hz (If you want to get a lower frequency, for example, 1Hz, you need to increase the capacitor C1 to 47uF.)
    2. The level is 3 dB lower since we use one arm of the DDS current mirror.
    3. The level of harmonics will become higher since we do not use a current mirror and a balanced transformer.
    If you want all these characteristics not to deteriorate, then instead of T2 you need to put a transformer that will have a large inductance that will allow it to work at lower frequencies. This transformer must be calculated and manufactured independently.

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