  Spectra of circularly polarized harmonics is calculated by numerically
solving the Time-Dependent Schr\"{o}dinger Equation for a 2D model of Ne atom
using circularly polarized fundamental with counter-rotating second harmonic
laser fields. We demonstrate strong asymmetry between left- and right-
circularly polarized harmonics when a ground state with p-type symmetry is
used. It arises due to the circular polarization of individual attosecond
pulses in the generated pulse train. Reducing the length of the
counter-rotating drivers and introducing a small time-shift between them allows
to generate a single elliptically polarized attosecond pulse.
