Yes / This paper presents a novel 2D meta-surface wall to increase the isolation between microstrip patch radiators in an antenna array that is operating in the teraherz (THz) band of 139–141 GHz for applications including communications, medical and security screening systems. The metasurface unit-cell comprises conjoined twin ‘Y-shape’ microstrip structures, which are inter-digitally interleaved together to create the meta-surface wall. The proposed meta-surface wall is free of via holes and defected ground-plane hence easing its fabrication. The meta-surface wall is inserted tightly between the radiating elements to reduce surface wave mutual coupling. For best isolation performance the wall is oriented orthogonal to the patch antennas. The antenna array exhibits a gain of 9.0 dBi with high isolation level of less than −63 dB between transmit and receive antennas in the specified THz-band. The proposed technique achieves mutual coupling suppression of more than 10 dB over a much wider frequency bandwidth (2 GHz) than achieved to date. With the proposed technique the edge-to-edge gap between the transmit and receive patch antennas can be reduced to 2.5 mm. Dimensions of the transmit and receive patch antennas are 5 × 5 mm2 with ground-plane size of 9 × 4.25 mm2 when being constructed on a conventional lossy substrate with thickness of 1.6 mm. / H2020-MSCA-ITN-2016 SECRET-722424 and UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1