The Technology Of Instantaneous Microwave Frequency Measurement Based On Asymmetric M-Z Interferometer

With the development of the wireless technology and the radar technology, in modern electronic warfare and radar systems it is significant to intercept and analyze microwave signals from enemy communication systems. Those signals may have a broad range of frequency, but typical microwave receiver can only process narrowband signals. For this reason, it is a demand to determine the frequency of the coming microwave signal in an accurate and quick manner, before further processing by the dedicated receiver. This function is carried out by an instantaneous frequency measurement(IFM) system. Microwave-photonic technology is introduced to light weight, small size, low loss, wide bandwidth, electromagnetic interference immunity. Bring the Microwave-photonic technology into the IFM system can take advantages on the frequency measurement. Due to the widespread attention from researchers civil and abroad, related research has become the current hot spots. However, microwave photonics frequency measurement technology still has some issues that made the practical using failed, such as low integrated level, complicated and poor measurement rate.In order to solve the problems above, a system of instantaneous microwave frequency measurement based on asymmetric Mach-Zehnder interferometer(MZI) is proposed. This system is based on simple structure, can be easily integrated. The theoretical measurement accuracy can arrive at 0.1 GHz, and the measurement range is between 1 GHz and 20 GHz. Those performances are closer to the practical using.First, the theories used in this system are introduced. Then, the basic structure and working principle of the instantaneous microwave frequency measurement system based on asymmetric MZI is proposed. In order to proof the feasibility of the system, transmission characteristics were given by a mathematic way. Descriptions of the parameters are introduced briefly in the end of first section.Second, in order to meet the requirement of the IFM system, some basic structures of the system are designed. Then characteristics of the IFM system determined by those basic structures can be given below: a) optical waveguide working on single mode; b) bending loss of the MZI is less than 1 d B; c) modulation range is between 1 GHz and 30 GHz; d) free spectrum range is 35 GHz.Then, some other parameters are investigated. Those parameters can partition into three parts: a) laser; b) PD; c) receiver. In the end, some available values of those parameters are given. The hold characteristics of the IFM system are provided after all designs finished. Finally, an experiment was given to demonstrate the available of those designs. The relationship between the output optical power and the input microwave frequency was showed after the experiment.