A technique for determining channel coefficients for a first array of antennas coupled through respective first phase shifters to a first radio chain and a second array of antennas coupled through respective second phase shifters to a second radio chain is described. As to a method aspect of the technique, pairs of first and second phase vectors are applied to the first and second phase shifters, respectively. Each of the pairs defines complementary directional gains at the first and second arrays for receiving reference signals. A channel estimation is performed in each of the first and second radio chains for each of the pairs based on the received reference signals. Based on the channel estimations for each of the pairs, at least one channel coefficient for the antennas in each of the first and second arrays is determined.