V-Band Millimeter-Wave Over Fiber Transmission Based On Microwave Photonic Frequency Conversion

Millimeter-wave（mm-wave）with a relatively high frequency band ranging from30GHz to 300GHz reveals abundant available spectrum resources and thus mm-wave technologies have become one of the key pillars to meet the vision of 5G/6G wireless networks.The V-band（50GHz-75GHz）stands out by large bandwidth and unlicensed band around 60GHz in next wireless communications.Microwave photonic（MWP）has inherent advantages in mm-wave applications for high bandwidth,immunity to electromagnetic interference and low loss.To generate and distribute high-frequency mm-wave signal by MWP,termed mm-wave radio over fiber（m-Ro F）holds great promise for facilitating high-capacity,low-cost and long-distance mm-wave networks.Thus,orientated by the advantages of high-capacity and low-cost requirements of dense mm-wave centralized radio access network（C-RAN）,high bandwidth and transparent transmission,this thesis concentrates on V band m-Ro F transmission based on MWP frequency conversion and signal processing.Details of the research are as follows:For the imperious demand of low cost and simple structure in dense mm-wave C-RAN,a V-band m-Ro F uplink fronthaul transmission using cascaded MWP downconversion is proposed.60GHz broadband radio frequency（RF）signal is directly modulated on ultra-wideband mach-zehnder modulator（MZM）in remote radio unit（RRU）without using complex and expensive mm-wave mixers,and RF signal is transmitted to central unit（CU）by a low-loss m-Ro F link.Symmetrically,sub-harmonic down-conversion is implemented using another MZM and a local oscillator（LO）signal in CU.Verified by the experiment,QPSK OFDM mm-wave signal with the center frequency in the range of 50GHz-70GHz is converted to the intermediate frequency（IF）with the center frequency of 1.4GHz using LO signal of 30GHz.IF signals with a bandwidth of 2.4GHz achieve a bit error rate（BER）performance below the 7%hard-decision forward error correction limit3.8?10^-3alone 5km fiber and 1.2m wireless transmissions.In addition,QPSK OFDM mm-wave signal with a bandwidth of 10GHz can achieve a bit rate of 10Gbit/s after 5km fiber and 1.2m wireless transmissions.Compared with the traditional electrical coherent frequency conversion and the envelope detection,the scheme has a simpler RRU structure and better transmission performance respectively.Basing on uplink transmission research,a full-duplex V-band m-Ro F transmission is realized by means of centralized MWP self-heterodyne frequency conversion.The optical heterodyne frequency-beating generation of downlink mm-wave communication,uplink mm-wave signal carrying and self-heterodyne downconversion are realized by using the same carrier-suppressed double-sideband optical signal,which can significantly reduce the structure and costs of RRUs and CUs.In the downlink,the optical heterodyne frequency-beating is used to convert the 16-QAM OFDM IF signal with a bandwidth of 2.5GHz to the mm-wave frequency band near 54GHz.After 25km fiber and 1.2m wireless transmission,BER of the received signal is1.9?10^-3and bit rate is 10Gbit/s.A gross bit rate of 6Gbit/s can be achieved over a total spectrum of 5.4GHz with the RF pilot phase noise cancellation in the uplink.In the uplink,QPSK OFDM measured mm-wave signal with a center frequency of 56.4GHz and bandwidth of 5.4GHz achieve a transmission bit rate of 6Gbit/s,obtained BER of the received siganal is6.4?10^-4.The research has directive significance for the mm-wave communications and network based on MWP signal processing,and provides a new solution for the realization of low-cost,long-distance transmission and ultra-dense mm-wave C-RAN with large capacity.