  Light sources worldwide have experienced rapid growth in the last decades,
pushing towards higher brightness with lower emittance to meet growing demands
from the user community. The quest for higher brightness motivates the
development of low-emittance ring lattices. At this point, all
fourth-generation storage ring light sources employ variations of the
Multi-Bend Achromat (MBA) lattice. In this paper, we discuss an extension of
this approach, known as Complex Bend\cite{Timur_2018_techreport} Achromat (CBA)
lattice in relation to the future NSLS-II upgrade. A detailed approach for the
lattice design will be described, and the developed lattice will be presented.
The benefits of using a complex bend approach are demonstrated by achieving a
small natural emittance of 23 pm at a beam energy of 3 GeV, straight sections
of 8.4 m for long IDs acquiring a ratio of about 50\% of the drift space with
respect to the ring circumference, compact ring elements (complex bends) based
on Permanent Magnets and a large-scale reduction in the number of power
supplies. Our new approach provides an extension to the MBA concept for the
next-generation light source lattice design.
