This paper presents a frequency-dependent orbital angular momentum (OAM) mode generation technique using a uniform circular array (UCA) antenna with series-feed proximity coupling. The proposed antenna operates within its specified frequency band, generating the OAM mode (Formula presented.) at the lower functional frequency and (Formula presented.) at the higher functional frequency. This functionality is achieved through proximity coupling and an optimized radius of the UCA circularly polarized (CP) array elements, which enable the required frequency-dependent behavior. The array elements, designed as sequentially rotated CP patches, provide the necessary phase shift for OAM mode generation. A prototype of the design is fabricated using an FR4 substrate with an overall size of 210 mm (Formula presented.) 210 mm. Simulated and measured results confirm the successful generation of OAM modes (Formula presented.) and (Formula presented.) within their respective frequency ranges. The design offers a low-profile structure, compatibility with transceiver circuits, and a simple architecture, making it suitable for advanced vehicular and wireless communication applications.