NI 5442
IQ Combiner

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, the I and Q data streams are combined after they are multiplied with the carriers. The IQ combiner is implemented as I_p − Q_p. The combiner block dictates that the following conditions must be true at any given time during the generation, or an overflow can occur:

-1 ≤ I_pCos(ωt + Φ_I) − Q_pCos(ωt + Φ_Q) ≤ 1 if the carrier is enabled or

-1 ≤ (I_p − Q_p) ≤ 1 if the carrier is disabled

where I_p and Q_p are the processed I and Q streams

Tip  If the OSP block is configured for quadrature upconversion, and the Carrier Phase I property or the NIFGEN_ATTR_OSP_CARRIER_PHASE_I attribute is set to 0° and the Carrier Phase Q property or the NIFGEN_ATTR_OSP_CARRIER_PHASE_Q attribute is set to -90°, then the IQ combiner must follow the following formula (Ip2 + Qp2 ≤ 1) or an overflow can occur.

When an overflow occurs, the data is clipped at the rail where the overflow occurred and the OSP block continues to process data. NI-FGEN returns an error when the status of the signal generator is checked.

Tip  To disable error reporting caused by OSP overflows, use the OSP Overflow Error Reporting property or the NIFGEN_ATTR_OSP_OVERFLOW_ERROR_REPORTING attribute.