Light source facility based on the 2.5 GeV ANKA storage ring successfully operates at the Karlsruhe Institute of Technology since 2000. At present the acceleration of particles is accomplished in three steps. Electrons are accelerated up to 50 MeV in the Race Track Microtron, gain energy up to 500 MeV in the 1 Hz cycling booster synchrotron. Then particles are accumulated and ramp energy in the main ANKA ring. Major upgrade of existing accelerators aims for the full energy injector LINAC similar to one designed for the MAX-IV facility in Lund (Sweeden) and low emittance storage ring inscribed into the present ANKA synchrotron geometry in order to preserve existing beam lines. The main objective of ring upgrade is to reduce the emittance of electron beam in 10 times to less than 8 nm?rad while ensure acceptable dynamic aperture and large momentum acceptance. Comprehensive studies and computer simulations have been done in order to find and optimize new lattice structure based on split bending magnets geometry and non-interleaved location of sextupoles separated by “–I” unit transfer matrix. We achieved compensation of second order aberrations and increased momentum acceptance in few times with respect to present design.