Seamlessly merging radar ranging and imaging, wireless communications, and spectrum sensing for 6G empowered by microwave photonics.

To facilitate intelligent interconnection among people, machines, and things, the next generation of communication technology must incorporate various sensing functions besides high-speed wireless communications. Integration of radar, wireless communications, and spectrum sensing is being investigated for 6G with increased spectral efficiency, enhanced system integration, and reduced cost. Microwave photonics, a technique that combines microwave engineering and photonic technology is considered an effective solution for implementing the integration and breaking the bottleneck problems of electronic solutions.

In-band full-duplex multiband mobile fronthaul network based on analog radio-over-fiber and tandem SSB modulation.

An in-band full-duplex multiband mobile fronthaul network is proposed based on analog radio-over-fiber and tandem single-sideband (TSSB) modulation. Two optical carriers with a wavelength spacing of 50 GHz in accordance with international telecommunication union dense wavelength division multiplexing (DWDM) standards are employed in each distributed unit (DU): one is used to carry two different radio frequency (RF) vector signals at 3 and 10 GHz, while the other is used to carry a vector signal at 15 GHz and a single-tone signal at 15 GHz. At the DU, a parallel TSSB modulation is applied, which eliminates the cross talk of TSSB modulation through two dual-polarization binary phase-shift keying (DP-BPSK) modulators.

Photonics-assisted compressed sensing radar receiver for frequency domain non-sparse signal sampling based on dictionary learning.

A photonics-assisted radar receiver based on compressed sensing (CS) technology is proposed to receive frequency domain non-sparse radar signals. The radar echo signal is mixed with a pseudo-random binary sequence (PRBS) in a photonic random demodulator (RD) consisting of a laser diode (LD), a dual-drive Mach-Zehnder modulator (DD-MZM), and a photodetector (PD). After the mixed signal from the photonic RD is undersampled by an analog-to-digital converter (ADC), the echo signal is reconstructed in the digital domain using an overcomplete dictionary generated by the dictionary learning algorithm and sparse reconstruction algorithm.

Photonic-based analog and digital RF self-interference cancellation with high spectral efficiency.

A photonic-assisted analog and digital radio frequency (RF) self-interference cancellation (SIC) approach with high spectral efficiency is reported for base stations in in-band full-duplex radio-over-fiber systems on the basis of our previous research. One dual-polarization quadrature phase-shift keying (DP-QPSK) modulator is used as the canceller for one base station. The two dual-parallel Mach-Zehnder modulators of the DP-QPSK modulator are both biased as carrier-suppressed single-sideband modulators and driven by the received signal and reference signal, respectively, to achieve high spectral efficiency while implementing the SIC in the optical domain.

Multiple radio frequency measurements with an improved frequency resolution based on stimulated Brillouin scattering with a reduced gain bandwidth.

A photonic-assisted multiple radio frequency (RF) measurement approach based on stimulated Brillouin scattering (SBS) and frequency-to-time mapping with high accuracy and high frequency resolution is reported. A two-tone signal is a single-sideband (SSB) modulated on an optical carrier via a dual-parallel Mach-Zehnder modulator to construct one SBS gain and two SBS losses for SBS gain bandwidth reduction. The unknown RF signal is also SSB modulated on a carrier that has been modulated by a sweep signal, thus the unknown RF signal is converted to a sweep optical signal along with the sweep optical carrier.

Photonic-based reconfigurable microwave frequency divider using two cascaded dual-parallel Mach-Zehnder modulators.

A photonic-based reconfigurable microwave frequency divider using two cascaded dual-parallel Mach-Zehnder modulators (DP-MZMs) is proposed. The first DP-MZM is driven by the input microwave signal, whereas the second DP-MZM is incorporated in an optoelectronic oscillator (OEO) loop and driven by the feedback signal. By properly setting the working conditions of the two DP-MZMs, the frequency of the input microwave signal is divided and the frequency-divided signal will oscillate in the OEO loop, with a tunable frequency-division factor determined by the bias conditions of the DP-MZMs.