Business analysts gather requirements commonly known as elicitation, analyze requirements, validate requirements, and manage requirements.
But they are also involved in the design of the solution.
While requirements focus on the needs of the organization, the design focuses on the actual solution which would fulfill that need.
Requirements that have been validated are used in the design of the solution.
But while those requirements might seem complete while designing the solution the business analyst might realize that they need additional requirements.
So they would need to go back to the stakeholders and gather more requirements from the stakeholders.
Examples of how requirements and design work together in creating a solution include
Example 1. Requirement: The organization needs to be able to view sales data by product and region.
Design: Mock up of a reporting dashboard.
Example 2. Requirement: Software should have the capability to limit the access rights of various users based on their department
Design: Access rights functionality prototype
As shown above the requirements are used in the design of the solution.