NI 5441
Numerically Controlled Oscillator (NCO)

The Numerically Controlled Oscillator (NCO) is a digital circuit that creates two cosine waves of the same frequency (the carrier frequency) with two independent phases. You can use the Carrier Frequency property or the NIFGEN_ATTR_OSP_CARRIER_FREQUENCY attribute to set the carrier frequency. The I phase cosine waveform is multiplied by the I signal path, and the Q phase cosine waveform is multiplied by the Q data path. The I and Q phases are programmable from -180° to 180° by setting the Carrier Phase I and Carrier Phase Q properties or the or the NIFGEN_ATTR_OSP_CARRIER_PHASE_I or or the NIFGEN_ATTR_OSP_CARRIER_PHASE_Q attributes. The Carrier Phase Q property only applies when the Data Processing Mode property is set to Complex or the NIFGEN_ATTR_OSP_DATA_PROCESSING_MODE attribute is set to NIFGEN_VAL_COMPLEX. Both the frequency and the phases can be updated during generation. For quadrature upconversion, set the I phase to 0° and Q phase to -90°. The Carrier Phase I/Q properties can be used to simulate quadrature skew impairments. Change the I or Q Carrier Phase by the required quadrature skew to simulate this impairment.