Q(1) If I enable the Premodulation and set HB1 and HB2 to mode 1, do I get the
x(t) = I(t)cos(2*PI*f*t) - Q(t)sin(2*PI*f*t), f = 125 MHz with 4 x
interpolation at the I-DAC output, and if not, how do I setup AD9146 in order
to obtain this signal.
2) Can you explain how the mixing / modulation is done in the Premodulator, HB1
and HB2, so it's easier to predict the the outcome of different settings of the
Premodulator, HB1 and HB2.
A(1) The answer is yes, using Premod modulate the single to Fdata/2 in this
case 250MHz/2 = 125Mhz. Selecting HB1 mode 1 and HB2 Mode 1 is the correct
filter modes. In this case they only do interpolation the modulation is done by
the premod block.
It is Ok to only use the I output but you do need to feed complex data to the
input which your email indicates you plan to do.
2) The HB1/2 filters includes modes that modulate to fs/4, fs/2 and 3Fs/4
when the premodulation is not turned on. Since you want to mdulate to Fs/8 and
are using 4x interpolation the premod block modulates to the fs/8. The mixing
is described in table 20. The modulation require I and Q data into the part.
The modes of these filters set the filter center frequency and/or modulation.
In some filter mode modulation is done but in modes 1 for both HB1 and HB2
there is no modulation just the center freq shift to 125MHz.
This diagram from our AD9122 part show how the HB1,2,3 work the AD9146 doesn’t
have an HB3.