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Frequency hopping (FH) has been widely used as a powerful technique for antijamming in wireless communications. However, as the wireless spectrum is becoming more and more crowded, it is very difficult to achieve efficient antijamming results with FH-based schemes. Orbital angular momentum (OAM), which provides the new angular/mode dimension for wireless communications, offers an intriguing way for antijamming. In this paper, we propose to use the orthogonality of OAM-modes for antijamming in wireless communications. In particular, we propose the mode hopping (MH) scheme for antijamming within the narrow frequency band. We derive the closed-form expression of bit error rate (BER) for multiple users scenario with our developed MH scheme. Our developed MH scheme can achieve the same antijamming results within the narrow frequency band as compared with the conventional wideband FH scheme. Furthermore, we propose mode-frequency hopping (MFH) scheme, which jointly uses our developed MH scheme and the conventional FH scheme to further decrease the BER for wireless communication. Numerical results are presented to show that the BER of our developed MH scheme within the narrow frequency band is the same with that of the conventional wideband FH scheme. Moreover, the BER of our developed MFH schemes is much smaller than that of the conventional FH schemes for wireless communications. Index Terms-Orbital angular momentum (OAM), mode hopping, frequency hopping, mode-frequency hopping, mode decomposition. I. INTRODUCTION F REQUENCY hopping (FH), which is a solid anti-jamming technique, has been extensively used in wireless communications. There exist some typical FH schemes such as adaptive FH [2], differential FH [3], uncoordinated FH [4], adaptive uncoordinated FH [5], and message-driven FH [6], etc. These FH Manuscript

A new level shifter used in multiple voltage digital circuits is presented. It combines the merit of conventional level shifter and single supply level shifter, which can shifter any voltage level signal to a desired higher level with low leakage current. The circuits wad designed in 180nm CMOS technology and simulated in SPICE. The simulation results showed that the proposed level shifter circuit has 36% leakage power dissipation reduction compared to the conventional level shifter.

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