Reconstruction Of The Characteristics Of Nonuniform Transmission Lines And Analysis Of The Noise Effects

The Zakharov-Shabat inverse scattering problem and its algorithm have been studied. The inverse scattering problem deals with the scattering parameters to reconstruct some characteristic parameters. This technology of getting the information of the object without touching it can be widely used. In order to testify the validity of this algorithm, a common used function with explicit analytical had been adopted as an example, and the numerical results showed that the algorithm is effective. Then we take a tapered transmission line as an example to reconstruct the characteristic impedance, which the ratios of two ports matched impedance are 2,3,4 respectively. A method of calculating the characteristic impedance from two ports then get the mean of them, to minimize the error, which will accumulate in the integral calculation, the experiment results showed that this method can reduce the error. In modern communication system, especially satellite communication and mobile communication, to keep the minimum equipment and high quality is one of the most important tasks in wireless communication. In order to minimize the scale of the microwave circuits, some standards have been approved for operating dual band with the dual frequency devices, for example the dual frequency antennas. Filter is one of the most important devices in microwave system, there fore the research about filters is one of the hotspot. Basically there are two methods for a dual frequency filter, one consists of a bandpass filter and a bandstop filter in a cascade connection, the other consists of two different central frequency bandpass filters in a cascode connection. This dissertation proposed a new idea to realize a dual passband filter with a nonuniform transmission line. The impedance profile of the NTL can be realized which satisfy the frequency requirement. Given the relative permittivity, the thickness of the dielectric and the conductor, we can get the geometry of the NTL.By the transient analysis of the NTL, when a voltage pulse sent at one port of the transmission line, the reflection signal will reach the steady region after a transient region, the steady state value is determined by the source and load terminations. For this reason we can use time domain reflectometry, the advantages of the TDR is that it can measure the transient response of the DUT compare with the network analyzer. It will severely affect the reconstruction results when there exists noise in the time domain reflection signal. In this dissertation, numerical experiments are carried out to reconstruct the characteristic impedance profile of an exponential type transmission line taper from its time domain reflection signal which is contaminated by white Gaussian noise. The effective algorithm for solving Zakharov-Shabat inverse scattering problem is employed. The numerical results show that the reconstruction algorithm is stable, and the characteristic impedance profile of the nonuniform transmission line can be reconstructed effectively in a wide S/N range.