Mutong Xie

Measurement of the rotational Doppler frequency shift of a spinning object using a radio frequency orbital angular momentum beam

An indirect approach based on phase measurement is proposed to measure the rotational Doppler frequency shift, which takes full advantage of the phase structure of orbital angular momentum (OAM) beams in radio domain, using a vector network analyzer (VNA) as a phase discriminator. A proof-of-concept experiment is established by an optical-controlled system with the OAM state of 1. By analyzing the experiments results, the rotational Doppler frequency shift is measured as 24.83 Hz (max error rate 0.67%) at 50π rad/s rotational velocity, deducing the rotational velocity as 50.18π (average error rate 0.36%).

Anti-dispersion phase-tunable microwave mixer based on a dual-drive dual-parallel Mach-Zehnder modulator

An optically-controlled phase-tunable microwave mixer based on a dual-drive dual-parallel Mach-Zehnder modulator (DDDP-MZM) is proposed, which supports wideband phase shift and immunity to power fading caused by chromatic dispersion. By using carrier-suppressed single side-band (CS-SSB) modulation for the local oscillator (LO) signal and carrier-suppressed double side-band (CS-DSB) modulation for the input signal, no vector superposition for the same output microwave frequency occurs, making the system immune from power fading caused by chromatic dispersion. Phase tuning is achieved by shifting the phase of the LO signal, and direct electrical tuning of the wideband microwave input signal is avoided, thus supporting large working bandwidth. A phase-shifted down-conversion experiment is carried out, where a phase shift with 0 ~390° and down-conversion are achieved with a phase variation of less than 5° and power variation less than 3.5 dBm when the input signal sweeps between 12 ~16 GHz. The mixer is simple and power-efficient since it uses a single compact modulator, and does not require any optical filters. No power notches are observed in the output microwave spectrum, proving that the dispersion-related frequency-selective fading is mitigated.

Bidirectional radio over fiber system with wavelength reuse based on optical carrier polarization-suppressed DSB modulation

To overcome the limitation of wavelength-dependent optical filter, we have experimentally demonstrated a bidirectional RoF system based on carrier polarization-suppressed DSB modulation. After transmitted over 10.5-km SMF, 0.3-dB power penalty is achieved for bidirectional links.

Optical-controlled pencil-beam steering phased-array based on FD-OP

A pencil-beam steering phased-array based on optical-controlling scheme is proposed. FD-OP is used to gain flexibility and high tunablility. Experiments are conducted at 17 GHz to validate the 2D beams-steering ability of the system.

Mode measurement of a dual-mode radio frequency orbital angular momentum beam by circular phase gradient method

A measurement method of dual-mode radio frequency orbital angular momentum (RF-OAM) beams is proposed, dedicated to meeting the practical needs of the orbital angular momentum mode-division multiplexing (OAM-MDM) in free-space communication. Theoretical analysis and numerical simulations are conducted to demonstrate that a dual-mode OAM beam can be unambiguously measured by gathering the phase gradient function of a circle around the OAM beam axis and calculating its average value and PV (peak/valley) factor. A proof-of-concept experiment is presented, which employs a single receiving antenna on a rotatable plane to measure mode +1 and –2 of a dual-mode OAM beam.

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.

The First Experiment to Transmit RF Data in OAM Mode with Optical-assisted Circular Antenna Arra

We conducted the first experiment to transmit an RF IQ signal in OAM mode by OCAA, to prove that OAM modes coexists with IQ modulation and could be measured. Directionality and transmission quality is assessed.