Yongfeng Wei

Generating, multiplexing/demultiplexing and receiving the orbital angular momentum of radio frequency signals using an optical true time delay unit

A scheme for generating and/or eliminating the orbital angular momentum (OAM) of radio frequency (RF) signals based on the true time delay (OTTD) system is proposed for the first time. The central structure of the scheme is the OTTD unit connected with a circular antenna array which can provide or compensate the helical phase variation precisely, and therefore can form or eliminate the OAM radio beam with different states (the topological charges) conveniently. Other prominent advantages of the proposed system are support for multiplexing/demultiplexing the OAM states carried on the RF signals with the same frequency and support for exchange of the OAM states carried on two RF signals. This can be regarded as the analog of various other multiplexing technologies for increasing the capacity and efficiency in radio communication systems. Theoretical analysis and numerical simulations demonstrate the feasibility of the proposed scheme.

Generating the orbital angular momentum of radio frequency signals using optical-true-time-delay unit based on optical spectrum processor

A system for generating radio frequency signals with orbital angular momentum (OAM) is proposed and certificated for the first time, which employs an array of multiple optical-true-time-delay elements and circular antennas array (CAAs). A constructive Fourier series theory about CAAs collectively forming an OAM radio beam is demonstrated. An optical spectrum processor offers the four lines high-resolution time delay by adding a series of linear optical phase shifts. The OAM radio beam with topological charge L=1 is produced and measured successfully.

An orbital angular momentum radio communication system optimized by intensity controlled masks effectively: Theoretical design and experimental verification

A system of generating and receiving orbital angular momentum (OAM) radio beams, which are collectively formed by two circular array antennas (CAAs) and effectively optimized by two intensity controlled masks, is proposed and experimentally investigated. The scheme is effective in blocking of the unwanted OAM modes and enhancing the power of received radio signals, which results in the capacity gain of system and extended transmission distance of the OAM radio beams. The operation principle of the intensity controlled masks, which can be regarded as both collimator and filter, is feasible and simple to realize. Numerical simulations of intensity and phase distributions at each key cross-sectional plane of the radio beams demonstrate the collimated results. The experimental results match well with the theoretical analysis and the receive distance of the OAM radio beam at radio frequency (RF) 20 GHz is extended up to 200 times of the wavelength of the RF signals, the measured distance is 5 times of the original measured distance. The presented proof-of-concept experiment demonstrates the feasibility of the system.

Compensation of chromatic-dispersion for full-duplex radio-over-fiber links with vector signal transmission using frequency tripling

This paper demonstrates the theory of chromatic dispersion (CD)-induced constellation rotation (CR) in a radio-over-fiber (ROF) link, and a symmetry theory for compensation. A 60 GHz full-duplex ROF system with vector signal transmission using frequency-tripling modulation (FTM) is also proposed. The simulations for both 5 Gbps and 200 Mbps 16 QAM signal transmission show that the CD-induced CR can be entirely overcome due to the proposed method, and the proposed ROF schedule still maintains good performance even after 500 km of 200 Mbps vector signal transmission. Meanwhile, the central station is significantly simplified and cost-effective since only one 15 GHz local oscillator is needed for both the generation of an optical millimeter-wave signal and the carrier of the downlink intermediate-frequency (IF) signal.

High spectral purity millimeter wave generation and wavelength reuse radio over fiber system based on modified double sideband

A modified double sideband modulation(DSB) scheme to realize frequency doubling and wavelength reuse in the uplink is proposed. In the modified DSB scheme, by adjusting the phase difference between two arms of the intensity modulator, the optical carrier and the two first-order sidebands are generated, after beaten by the photodiode, a high spectrum purity and low phase noise millimeter-wave (mm-wave) signal with double times of the RF frequency without any optical filter or dc bias is generated. Theoretical analysis and numerical simulation are performed, showing that the power penalties for bidirectional signals are less than 2 dB after transmitted over 40 km single mode fiber. Additionally, the proposed scheme has simple configuration and good quality.

Full-Duplex ROF Link with Seamless Convergence and High-Speed Broadband Wireless Access

Full-duplex ROF link with seamless convergence and high-speed broadband wireless access is proposed. The simulation of V-band (62.4GHz) and conventional 802.11n (2.4GHz) with 16QAM signal transmission shows that our novel schedule maintains quite good performance.