We introduce the first antenna compression scheme for coherent radars. The idea is to transmit with a large array of phase-coded antennas at full power and later synthesize by linear superposition and proper phasing, the equivalent of a small transmitting antenna, similar to a single antenna module of the array. The full decoding is done by software by adding the power and cross-power estimates of the signals of each code, so no extra burden is added other than the summations. This approach allows the use of all the available power in phased array systems where either high-power transmitters cannot be used with small antennas or the transmitted power is distributed among the antenna elements. The wider beams are particularly important in meteor systems and, recently, in some radar studies of the neutral atmosphere, especially when multiple receiving antennas are used. Our scheme is based on complementary binary phase coding of antenna elements and works in a similar fashion to complementary phase coding used in pulse compression. We have implemented this idea at the Jicamarca Radio Observatory using a two-dimensional approach; thus four two-dimensional complementary codes were derived. The performance of this implementation has been tested using imaging techniques on an interferometer of four receiving antenna modules to study the angular characteristics of the well-known equatorial electrojet irregularities. In addition, in this mode we have made successful observations of the upper troposphere and lower stratosphere. ¿ 2001 American Geophysical Union