This article presents a high-capacity millimetre-wave communication system using orbital angular momentum (OAM) multiplexing. The system transmits eight OAM beams (four on each of two orthogonal polarizations) over a 2.5 m link at 28 GHz, achieving a data rate of 32 Gbit/s and a spectral efficiency of ~16 bits/s/Hz. The OAM beams are generated using spiral phase plates (SPPs) and multiplexed through a 1×4 combiner. At the receiver, the OAM beams are demultiplexed using SPPs and a mm-wave OAM mode demultiplexer, achieving low crosstalk (<-12.5 dB). The system demonstrates a 8 Gbit/s link with two OAM beams on each polarization. OAM is a property of electromagnetic waves where the phase front is helical, allowing multiple orthogonal beams to be transmitted simultaneously. This property enables increased system capacity and spectral efficiency in millimetre-wave communications. The study shows that OAM-based multiplexing can be implemented in radio frequency and millimetre-wave systems, offering potential for high-speed, high-capacity wireless communication. The research demonstrates the feasibility of OAM-based communication systems, showing that OAM channels can be separated with low crosstalk and high data rates. The system uses a single aperture pair for transmission and reception, reducing the need for complex signal processing. The results show that OAM-based communication systems can achieve high data rates with low bit-error rates, making them a promising technology for future wireless communication systems.This article presents a high-capacity millimetre-wave communication system using orbital angular momentum (OAM) multiplexing. The system transmits eight OAM beams (four on each of two orthogonal polarizations) over a 2.5 m link at 28 GHz, achieving a data rate of 32 Gbit/s and a spectral efficiency of ~16 bits/s/Hz. The OAM beams are generated using spiral phase plates (SPPs) and multiplexed through a 1×4 combiner. At the receiver, the OAM beams are demultiplexed using SPPs and a mm-wave OAM mode demultiplexer, achieving low crosstalk (<-12.5 dB). The system demonstrates a 8 Gbit/s link with two OAM beams on each polarization. OAM is a property of electromagnetic waves where the phase front is helical, allowing multiple orthogonal beams to be transmitted simultaneously. This property enables increased system capacity and spectral efficiency in millimetre-wave communications. The study shows that OAM-based multiplexing can be implemented in radio frequency and millimetre-wave systems, offering potential for high-speed, high-capacity wireless communication. The research demonstrates the feasibility of OAM-based communication systems, showing that OAM channels can be separated with low crosstalk and high data rates. The system uses a single aperture pair for transmission and reception, reducing the need for complex signal processing. The results show that OAM-based communication systems can achieve high data rates with low bit-error rates, making them a promising technology for future wireless communication systems.