Microwave Signal Parameter Estimation Based On Microwave Phtonics

Microwave photonics is widely used in signal processing civilian communications, defense and military, aerospace and medical fields and play a crucial role, as the unique advantages of its systems and devices(such as:low loss, light weight, high-bandwidth, small size, strong anti-electromagnetic interference and relatively stable frequency response). With the increasing frequency employed in recent years, microwave photonic signal processing technology, especially for the high-speed signal processing is widely used. This paper focuses on the parameters estimation of microwave signals, including an approach for the carrier frequency extraction based on optoelectronic oscillator(OEO), and a method of the symbol rate estimation. The details are as follows:(1) Based on the high Q factor, high spectral purity, and good stability properties of OEO system, a method for the carrier frequency extraction is proposed. Firstly, the received microwave signal is applied to modulate optical carrier under carrier-suppressed double sideband (CS-DSB) modulation, then the output optical signal as a carrier into the OEO ring; Then in this OEO loop does not use an electrical filter but the use of stimulated Brillouin scattering(SBS) gain spectrum and the loss spectrum with a very narrow bandwidth characteristics equivalent to a high Q microwave photonic filter, by setting the optical carrier wavelength at the lowest point of SBS loss spectrum, the advantage of microwave signal in the mode competition can achieve carrier extraction and the data is suppressed. In the experiments,10GHz and9.1GHz microwave signals without digital signal is extracted respectively. When the carrier frequency is10GHz and20GHz respectively, digital speed of PRBS is5Mbit/s, by comparing the simulation results of OEO open loop and closed loop, proved that the proposed system can extracte the carrier frequency of the recieved signals with data.(2) Based on photonic technique, an approach to the symbol rate estimation of the remote distributed microwave signal reception is proposed. Firstly, the received microwave signal is applied to modulate the light wave under the carrier-suppressed double sideband (CS-DSB) modulation in the remote terminal, generates two optical sideband signals carrying the microwave signal. Then the two sidebands are transmitted to the central station through optical fiber links, and one of them is filtered out in the optical domain. After the photoelectric detection (PD), The microwave signal symbol rate can be obtained by analyzing the spectrum of the electrical signals. The proposed approach is verified via both simulations and experiments. In the simulations, the symbol rate of0.8GBaud or6GBaud is successfully extracted for pseudo-random binary signal (PRBS) with the carrier frequency at60GHz; At the mean time, the symbol rate of3GBaud is extracted for PRBS signals with25GHz carrier frequency. In the experiments, the symbol rate at3GBaud or5GBaud was also achieved when the carrier frequency is25GHz. The proposed approach has the advantages such as wide instantaneous bandwidth, low loss for remote transmission, availability for distributed monitoring, and strong immunity to electromagnetic interference, which would play an important role for the microwave signal analysis and estimation.