AD9142ABCPZ datasheet(47/73 Pages) AD

47 / 73 page

AD9142A

Data Sheet

REDUCING LO LEAKAGE AND UNWANTED

SIDEBANDS

Analog quadrature modulators can introduce unwanted signals

at the local oscillator (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

using the digital dc offset adjustments (Register 0x3B through

Effective sideband suppression requires both gain and phase

matching of the I and Q signals. The I/Q phase adjust registers

(Register 0x37 and Register 0x38) and the DAC FS adjust

registers (Register 0x18 through Register 0x1B) can be used to

calibrate the I and Q transmit paths to optimize sideband

suppression.

For more information about suppressing LO leakage and

sideband image, refer to the AN-1039 Application Note,

Correcting Imperfections in IQ Modulators to Improve RF Signal

Fidelity and the AN-1100 Application Note, Wireless Transmitter

IQ Balance and Sideband Suppression from the Analog Devices

website.

Rev. A | Page 46 of 72

AD9142ABCPZ Datasheet(PDF) 47 Page - Analog Devices