A Modeling Method Of Microwave Nonlinear Scattering Function Based On Wavelet Neural Network

The work frequency and power of microwave devices have increased gradually with the development of large signal communication, the non-linear characteristic has also become obvious more and more. At present, the modeling methods based on small S-parameter have been used widely, but these methods could only be used in weak non-linear circumstance. Now a new concept has been proposed and it provides a bran-new direction for the description of high non-linear characteristic of power devices.This paper presents microwave circuit non-linear theory as well as traditional description and modeling methods in detail. Based on these methods, we propose a new description way—non-linear scattering function, we primarily study it's definition, physics meaning, characteristic, and it's connection with networks. At last we build the non-linear scattering function model of large signal microwave devices by using the black-box model. This method considers the power device as a black-box, there is no need to know the interior structure and work mechanism of device, we just need the work characteristic of it's ports, based on this, we can emulate a equivalent model of the parameters of device, this is the so-called Artificial Neural Networks. Once the model been built successfully, we can use it to describe the non-linear characteristic of device and design non-linear circuit such as microwave power amplifier.Finally we have built the measurement system of non-linear scattering function, and have tested power transistor MRF281, MRF158 and MRF9030, we have built the model of their non-linear scattering function by using Wavelet Neural Networks that based on BP algorithm, this network algorithm is realized by C language programming, and we have gotten reasonable results. All these experiments proved that Wavelet Neural Networks can be used in non-linear scattering function modeling issue. Based on this we would carry out the next plan that focused on non-linear circuit design problem by using this non-linear scattering function model.