Research On UWB Signal Generation Technology Based On The Pulse Difference And Optical Polarization Synthesis By Using Microwave Photonics

The signal with-10 dB bandwidth over 500 MHz or fractional bandwidth(-10 d B bandwidth divided by central frequency)over 20% is defined as the UWB signal.The UWB signal has drawn extensive attention and achieved good progress due to its characteristics,such as the large bandwidth,low power consumption,anti multipath fading and sharing spectrum with other signals.The UWB signal generation based on microwave photonics can not only overcome the bandwidth limitation of electronic devices,but also enlarge the coverage of UWB system through the combination with the technology of radio on fiber(Ro F).This paper studies the problems about UWB signal generation based on the pulse difference and optical polarization synthesis by using microwave photonics.Firstly,this paper explains the reason for choosing high-order Gaussian pulse as UWB signal,and then proposes an optical reconfigurable UWB signal generation scheme based on the pulse difference with polarization multiplexing.The orthogonal polarization multiplexing avoids the interference between two optical carriers with the same frequency.And,reconfigurable generation of UWB signal in optical domain is realized through the delayed combination of different pulses.After the theoretical analysis,a simulation of the UWB signal generation is carried out to verify the proposed scheme.By adjusting the DC bias voltages,time delay and power coupling coefficient of adjustable optical coupler,1-4 order UWB signals with center frequency of 3.75,4.5,5.5,6 GHz and fractional bandwidth of 173%,156%,127%,100% are generated respectively.By encoding the input electric Gaussian pulses,the UWB PSM,BPSK,OOK and PPM signals are generated respectively.And the effect of fiber dispersion on UWB signal transmission performance is explored.Then,an experiment is carried out to verify the feasibility of the reconfigurable UWB signal generation.By adjusting the DC bias voltage,time delay and adjustable optical coupler,1-4order UWB signals with center frequency of 3.37,4.79,4.5,5.05 GHz and fractional bandwidth of 166%,129%,124%,89% are generated in the experiment.By encoding the input electric Gaussian pulses,the UWB signal of PSM,BPSK and OOK are generated respectively,and the transmission performance of UWB signal is explored.Base on the UWB signal generation,modulation,transmission and wavelength division multiplexing technology,an optical UWB system with multiple accesses is proposed.The simulation results show that,the UWB signals with different code still have a good performance after being transmitted to remote base station through this optical UWB system.And the effects of width of input Gaussian pulse and time delay between upper and lower branches on UWB signal generation are also explored at the end of this paper.