The paper focuses on computational electromagnetics. To reduce the computation burden, the domain is divided into smaller subdomains that are solved separately. A feature of such a scheme is the expression of the multipole expansion in one subdomain due to the sources placed in another subdomain. This work analyzes an alternative method to do this task. Now, the subdomains enclosing the antennas can have an arbitrary shape, hence reducing the distances between the antennas and the scatterers.