In RF transmitter (TX) IC having an offset‐QPSK modulation scheme, a sine wave of the transmission signal represented by a 12‐bit digital code generated through the genetic algorithm reduces the I/Q imbalance and the intermodulation distortion in the analog circuit of the TX. It was experimentally confirmed by using test ICs fabricated in a 130‐nm CMOS process. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2905–2912, 2016