This paper presents the design and experimental validation of a planar archimedean spiral antenna for broadband orbital angular momentum (OAM) beam generation. In contrast to OAM-based patch antennas with limited bandwidth, the proposed antenna is capable of producing OAM beams with a 20% fractional bandwidth (4.5–5.5 GHz). The design consists of four geometrically rotated archimedean spiral arms positioned at (Formula presented.) relative to each other. Due to the geometric rotation of the radiating arms, there is an inherent azimuthal phase progression that results in the desired phase progression for OAM mode (Formula presented.), thereby eliminating the need for a separate phase-shifting network for each feed point. The single-feed planar configuration exhibits good impedance matching, as indicated by (Formula presented.) being less than (Formula presented.) dB over the entire operating band. Simulated and measured results confirm stable vortex beam generation with OAM purity values in the range of 70%–80% throughout the bandwidth. The three-dimensional phase distribution demonstrates a consistent (Formula presented.) azimuthal phase rotation across frequency, thereby confirming broadband OAM beam generation. The demonstrated broadband operation and modal stability enable the proposed antenna structure to support microwave OAM-based imaging and spatial sensing systems.