  We consider theoretically phase locking in a simple two-dimensional Josephson
junction array consisting of two loops coupled via a joint line transverse to
the bias current. Ring inductances are supposed to be small, and special
emphasis is taken on the influence of external flux. Is is shown, that in the
stable oscillation regime both cells oscillate with a phase shift equal to
$\pi$ (i.e. anti-phase). This result may explain the low radiation output
obtained so far in two-dimensional Josephson junction arrays experimentally.
