The infinity and orthogonality of the orbital angular momentum (OAM) of vortex electromagnetic waves (VEMWs) provide a new degree of freedom for the modulation of information. The VEMW generated by the uniform circular array (UCA) exhibits the characteristics of the Bessel function in terms of amplitude, and there is a null amplitude region in the beam center. This characteristic is particularly obvious when the array radius is small. In practical applications, it is usually necessary to switch OAM mode to ensure the richness of the received information. This leads to a sudden drop in radiation energy when switching OAM modes, and the OAM mode cannot be fully utilized. To address this issue, this paper proposes an OAM mode switching method based on the characteristics of the intersection of the adjacent-order Bessel functions for radar forward-looking imaging. Meanwhile, this paper introduces OAM mode repetition frequency (OMRF) to indicate the “speed” of switching OAM mode. Finally, through the application in the field of forward-looking radar imaging, it is proved that the method proposed in this paper can effectively improve the OAM mode utilization rate and anti-noise ability.

Zippers are common in a wide variety of objects that we use daily. This work investigates how we can take advantage of such common daily activities to support seamless interaction with technology. We look beyond simple zipper-sliding interactions explored previously to determine how to weave foreground and background interactions into a vocabulary of natural usage patterns. We begin by conducting two user studies to understand how people typically interact with zippers. The findings identify several opportunities for zipper input and sensing, which inform the design of Zippro, a self-contained prototype zipper slider, which we evaluate with a standard jacket zipper. We conclude by demonstrating several applications that make use of the identified foreground and background input methods.