AD9146 Analog Devices, AD9146 Datasheet - Page 42

• Manufacturer Part Number: AD9146
• Description: Dual, 16-Bit, 1230 MSPS, TxDAC+® Digital-to-Analog Converter
• Manufacturer: Analog Devices

Specifications of AD9146

• Resolution (bits): 16bit
• Dac Update Rate: 1.23GSPS
• Dac Settling Time: n/a
• Max Pos Supply (v): +3.47V
• Single-supply: No
• Dac Type: Current Out
• Dac Input Format: Byte,LVDS,Nibble

AD9146
REDUCING LO LEAKAGE AND UNWANTED
SIDEBANDS
Analog quadrature modulators can introduce unwanted
signals at the LO frequency due to dc offset voltages in the
I and Q baseband inputs, as well as feedthrough paths from
the LO input to the output. The LO feedthrough can be nulled
by applying the correct dc offset voltages at the DAC output.
This can be done using the auxiliary DACs (Register 0x42,
Register 0x43, Register 0x46, and Register 0x47) or by using
the digital dc offset adjustments (Register 0x3C through
Register 0x3F).
Rev. A | Page 42 of 56
The advantage of using the auxiliary DACs is that none of
the main DAC dynamic range is used to perform the dc offset
adjustment. The disadvantage is that the common-mode level
of the output signal changes as a function of the auxiliary DAC
current. The opposite is true when the digital offset adjustment
is used.
Good sideband suppression requires both gain and phase
matching of the I and Q signals. The I/Q phase adjust registers
(Register 0x38 through Register 0x3B) and the DAC FS adjust
registers (Register 0x40 and Register 0x44) can be used to calibrate
the I and Q transmit paths to optimize sideband suppression.
Data Sheet