Other Parts Discussed in Thread: LMX2581
i use AFE7071 in my design. i use a 64Mhz crystal oscillator as DAC clock(convert to differential clock by a balun) and
FPGA clock, the FPGA generate DAC data and use same oscillator with DAC. i set AFE7071 to single differential DDR
clock mode, and make sure the DACCLKP rising edge latch the I data, and falling edge latch the Q data.
the LO is LMX2581, differential output to AFE7071 LO input, and the LO frequency is 640Mhz.
i generate a single tone I/Q base band data. disable the offset and QMC function, but the RF output image spectrum is
very high, only about -10dbc to the main output spectrum.
1 i enable the QMC function and adjust the phase and gain ,but can not get good result.
2 i change the LO input to single ended(disconnect the LO_N to LMX2581 and connect to a capacitor and resistor to gnd)
the image spectrum decrease to -25dbc.
the sideband suppression is far away from the value in datasheet
can anyone can help me to resolve this problem? can i should check the LO , config register or other point?