I have selected the AD9106 for inclusion into a piece of commercial test equipment I’ve designed. I have the Eval board (AD9102-ARDZ & the EVAL-SDP matching processor) and have been working with them. I have it doing most of what I desire. However, I have a few issues (see below) that I could use some explanations.
What I’m trying to do:
- I need to make a 0-10khz two carrier frequency (FSK) modulated waveform. That is, small one carrier for a time, followed by a second of a different frequency then repeat forever. An additional catch is that the two frequencies are of differing amplitudes. An example plot is referenced for a basic two-tone FSK, but no mention as to how. (See Figure 53, of the AD9102 datasheet). Again note: In my case, the two carriers need to be of different amplitudes.
- Related: The datasheet states: “When the frequency of the DDS needs to change within each pattern period, a sequence of values stored in SRAM is combined with a selection of DDSTW_MSB bits to form a tuning word.” Explain? I assume this is somehow tied to CMD Reg 0x47. But the datasheet offers little on what the meaning of bits [4:0] imply? Or, how to use them.
- Related: The datasheet states: “When the frequency of the DDS needs to change within each pattern period, a sequence of values stored in SRAM is combined with a selection of DDSTW_MSB bits to form a tuning word.” Explain? I assume this is somehow tied to CMD Reg 0x47. But the datasheet offers little on what the meaning of bits [4:0] imply? Or, how to use them.
- Is there a way to get DOUT to pulse after each pattern period? It seems to imply that it only outputs on a pre/post delay of Trigger#. Not all that useful for my application.
- What is the difference between Digital Gain (Cmd Addr 0x32-0x35) , and Analog Gain control (Cmd Address 0x4-0x7)? Digital seems to be working for me but only provides a 0-1V output range. (into 100ohm current shunt)
- A DDS source can be amplitude modulated (Figure 52-Chirp). Can Tuning Words in memory be mixed with modulation waveforms? For example, First Carrier for a time, modulated in SRAM, followed by Frequency two, also followed by AM modulation in SRAM all inside a single pattern period?
For reference, I’m using an external 8Mhz clock source and the Internal amplifiers turned on.
Inquiring minds want to know
D. Aldrich
UTE Inc.
Added plot.
[edited by: UTE at 7:46 PM (GMT -4) on 3 Aug 2021]
