Generation Of Binary-coded Microwave Signal Based On Microwave Photonics

With the development of wireless transmission system, the demand for high-speed coding microwave signals becomes more important. Compared with many restrictions in electric field, generation and processing of microwave signal in the optical domain has the advantages of high bandwidth, low loss, immunity to electromagnetic interference. In recent years, there have been many achievements in the field of photonics microwave about signal coding. This paper is aimed to study the method of generation of coding microwave signals in the optical field. To obtain coding microwave signal through the optical domain, a method of phase-coded microwave signal generation using a filter based on polarization maintaining fiber bragg grating(PM-FBG) reflection spectrum, a method based on a loop structure and An all-fiber scheme for generating binary digital modulation radio frequency (RF) signals based on spectral shaping and incoherent frequency-to-time mapping are proposed. The research contents are as follows:This paper has analyzed the theory of incoherent frequency to time mapping and discussed how to use the principle in microwave photonics. The analysis shows that the pulse width in time domain is only depended on the bandwidth of filter and the dispersion coefficient of dispersion medium.We summarize the scheme of producing phase-coded microwave signals in the field of photonics microwave. Then we propose two methods of phase-coded microwave signal generation. One method is based on a loop structure, the principle is that the incident light has different modulation in clockwise and counterclockwise direction in the loop, at the output of the optical coupler(OC), we can get1st-order phase-modulated sideband with different power, after the photoelectric detector (PD), phase-coded microwave signals are obtained whose phase are corresponding to the applied voltage on the dual-parallel MZM. Then we propose the other method of phase-coded microwave signal generation using a filter based on PM-FBG reflection spectrum. The principle is that the two polarization states in the principal axis of PM-FBG have different reflection spectrum. By tuning the applied voltage on the PolM with a set of binary digital data, the phase-modulated signal are filtered in different way by PM-FBG reflection spectrum. Through the PD, phase-coded microwave signals are obtained whose phase are corresponding to the binary digital data. The schemes are implemented using OPTISYSTEM and MATLAB simulation.A photonic scheme for generating binary digital modulation RF signals based on spectral shaping and frequency to time mapping is proposed. We can obtain the binary coded signals with high frequency. In the proposed system, a polarization modulator is connected to a polarizing beam splitter(PBS). In each branch of the PBS, there is a differential group delay(DGD) that is used to create a specific optical spectrum after filtering by a band pass filtering. Through frequency to time mapping using a dispersive element(DE) the coded signals as the same shape as the optical spectrum are obtained. When the output light from one branch of the PBS is blocked by setting optical switch as off-state, the intensity-coded signals can be generated by tuning the applied voltage on the PolM; and the frequency-coded signals can be obtained when optical switch is on-state. The scheme is implemented by MATLAB simulation and experiment.