ABSTRACT
A multiband and multi-mode antenna with circular polarized conical patterns is suitable for achieving desired spectral efficiency, increased capacity, and spatial diversity for IoT applications. However, simultaneous excitation of such circular polarized multiple Orbital Angular Momentum (OAM) modes through a single patch antenna is challenging due to the complexity of simultaneously fulfilling distinct requirements of each mode. In this paper, a ring patch antenna is designed to excite different OAM states at different frequencies simultaneously. First, characteristic mode analysis is used to analyze the possibility of simultaneous excitation of multiple OAM modes at corresponding frequencies through a simple ring patch antenna. Then, a dual port ring patch antenna is designed and fabricated to verify the capability of generating multiple OAM states at corresponding frequencies. Furthermore, it also presents the guidance to suppress unwanted OAM modes.
ABSTRACT
In this paper, an improved multi-carrier generation scheme based on single-side-band recirculating frequency shifter with optical finite impulse response (FIR) filter for amplified spontaneous emission (ASE) noise suppression is proposed and experimentally demonstrated. The carrier-to-noise-ratio (CNR) instead of tone-to-noise-ratio (TNR) is introduced to more reasonably and exactly evaluate the signal-to-noise-ratio of a multi-carrier source with non-flat noise floor. We have experimentally attain the worst case CNR of 22.5dB and 19.1dB for generated 50 and 69 flat low noise carriers, which has shown significant improvement than the previous cited works based on recirculating frequency shifter.
