Simultaneous RF Self-Interference Cancellation, Local Oscillator Generation, Frequency up- and down-Conversion in an Integrated In-Band Full-Duplex 5G RF Transceiver Front-End

Abstract

Wideband radio-frequency (RF) self-interference cancellation (SIC), local oscillator (LO) generation, frequency up-, and down-conversion are all crucial for an in-band full-duplex (IBFD) 5G RF transceiver front-end. In this paper, a microwave photonic approach enabled by only one optical dual-polarization IQ modulator (DP-IQMZM) is proposed to simultaneously realize wideband RF SIC, LO generation, frequency up- and down-conversion. Note that, the LO signal with high spectral purity and low phase noise is produced by a dual-loop optoelectronic oscillator (OEO) using a self-polarization stabilization structure, and the generated LO signal is applied for frequency up- and down-conversion. Besides, the optical single-sideband signal is produced at the output of this 5G RF transceiver for uplink transmission from the remote antenna unit (RAU) to the baseband unit (BBU), so the power fading induced by fiber dispersion could be completely suppressed. A proof-of-concept experiment is performed, and the LO signal with the central frequency of 10 GHz, the phase noise performance of −108.97 dBc/Hz at a frequency offset of 10 kHz is achieved. A 5 × 20 MHz Long Term Evolution (LTE) 16/64-ary quadrature amplitude modulation-orthogonal frequency division multiplexing (16/64QAM-OFDM) signal with the central frequency of 12.6 GHz is down-converted to 2.6 GHz. Meanwhile, the cancellation ratio of 30.22 dB and 26.26 dB could be achieved when the bandwidth of the self-interference signal is 150 MHz and 300 MHz, respectively. Moreover, a 3 × 20 MHz LTE 64QAM-OFDM signal with a central frequency of 2.6 GHz is up-converted to 12.6 GHz, and the electrical signal-to-noise ratio of the generated RF signal can achieve 31.34 dB. The measured error vector magnitude performance shows that the generated down- and up-converted signal both meet the 3^rd Generation Partnership Project (3GPP) requirements for 5G systems.