[′kwä·drə·chər ¦pär·shəl ri′späns ‚kē·iŋ] (communications) A modulation technique in which two orthogonally phased carriers are combined; each carrier is modulated by one of the digital bit streams to one of three levels, used to convey chrominance information in color television, and considered for use in terrestrial radio. Abbreviated QPRK.