Research On Microwave Photonic Technology Based Integrated RF System And Its Application

The integrated RF system realizes a variety of RF functions on shared software and hardware resources. It has the advantages of unified spectrum control, flexible resource allocation, equipment redundancy reduction and maintenance costs reduction. Hence, this system has been widely used in the applications of defense electronic equipment, satellite payloads, and communication networks. However, the integrated RF system faces serious problems, such as narrow bandwidth, high loss, and electromagnetic interference. Since the emerging microwave photonic technologies have the advantages of broadband, low loss, high isolation, parallel processing, etc., we innovatively implement such technologies into the building of integrated RF system. The achivements are as follows,To solve the problems of broadband&multiband local oscillators (LOs) generation and distribution in integrated RF system, we propose a multiple LOs generation method based on dual optical frequency combs (OFC). The method can generate dozens of separated LOs with only three fixed LOs used. Since the generation structure is compatible with optical fiber, it can support large area LOs distribution and sharing. In the experiment, five LOs within L to Ka band are successfully generated with uniform amplitude.To solve the problems of broadband&multiband frequency conversion in integrated RF system, we propose two frequency conversion methods based on the OFC.(1) In the first method, by coherently heterodyning the optic-carried multiband RF signals with an OFC, we can simultaneously down-convert multiband RF signals to different intermediate frequencies. Besides, this method can compress and invert the signal spectrum. Compared to the back to back (B2B) measurement, the converted signals have an EVM degradation of7.5%.(2) In the second method, we convert one signal to multiple bands. The underlying principle is to mix dual coherent OFCs with one of which carrying the input signal. Then, by optically channelizing, the converted signal in different bands are obtained in different channels. In the experiment, A C-band signal of6.1GHz is successfully converted to3.9GHz,4.1GHz,11.9GHz,19.9GHz, etc. the maximum cross talk is-13.6dB. Compared with the B2B case, the scheme shows a9.3%EVM degradation at OdBm power.To mitigate the polarization sensitivity of fiber-optic links, we studied a sinusoidal-wave-based polarization scrambling method that can be shared by multiple paths. Theoretically, for a specific polarization modulation depth, the direct current component of the output can be independent of polarization disturbance. We experimentally suppress polarization disturbance for more than40dB. When implemented into the applications of remote electro-optical modulation and remote photonic RF mixing, this method brings excellent stabilities (within0.6dB and0.9dB respectively) to the transmitted RF signal.Finally, we carry out the application research on two kinds of integrated systems, the reconfigurable distributed antenna system and the communication satellite repeater.(1) By the combination of photonic RF switching and photonic RF transmission, we design a reconfigurable distributed antenna system and build a prototype of the system, which realizes the resource allocation.(2) By the combination of photonic RF conversion and photonic RF switching, an advanced satellite repeater is designed under the cooperation with China Academy of Science and China Academy of Space Technology. Multiband frequencies repeat between C(6/4GHz)> Ku(14/12GHz) and Ka(30/20GHz) is demonstrated.