Publication

Abstract : This paper presents a circular substrate-integrated waveguide (SIW) cavity array divided equally into eight wedges for generating orbital angular momentum (OAM) modes ℓ=±1 and ℓ=±2 at an operating frequency of 5.8 GHz. These eight azimuthally arranged SIW cavities are equipped with two arc-shaped radiating slots positioned along equiphase contours to achieve a uniform phase distribution. An external eight-way feeding network provides the required discrete phase progression, enabling multi-mode OAM generation using a single array. The fabricated prototype demonstrates a measured impedance bandwidth of 80 MHz, a return loss of approximately 30 dB, and inter-port isolation exceeding 25 dB. Experimental validation using cylindrical near-field measurements and Fourier-based modal decomposition confirms the generation of the desired modes with a radially averaged modal purity of approximately 97% for ℓ=±1 and 93% for ℓ=±2 .