Multichannel signal generator performance characterization employs orthogonal modulation to characterize a relative performance of channels of a multichannel signal generator. The performance characterization includes generating a first signal in a first channel of the multichannel signal generator and generating a second signal in a second channel of the multichannel signal generator. The first and second signals include an orthogonal frequency-division multiplexing (OFDM) digital modulation having a first set of subcarriers assigned to the first signal and a second set of subcarriers assigned to the second signal. Performance characterization further includes combining the first signal and the second signal to produce a combined signal along with receiving and demodulating the combined signal according to the OFDM digital modulation using a digital receiver and determining a performance parameter of the second channel relative to the first channel from the received and demodulated combined signal.