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Investigation On Time Domain Planar Near Field Measurement Simulation

Posted on:2008-03-12Degree:MasterType:Thesis
Country:ChinaCandidate:X J ShenFull Text:PDF
GTID:2178360215496540Subject:Electromagnetic field and microwave technology
Abstract/Summary:PDF Full Text Request
UWB radar operates simultaneously over large bandwidth and the antenna parameters must refer to simultaneous performance over the whole of the bandwidth. Conventional frequency domain(FD) parameters just like pattern gain etc are not adequate for UWB antenna. This thesis describes an UWB RCS/antenna planar near field(PNF) measurement system under construction to get the wideband RCS or the impulse response and transient characteristic of UWB antenna. Unlike the conventional antenna or RCS time domain test system, UWB radar signal instead of the no-carrier short time pulse was used to excite the antenna that can avoid the decrease of the dynamic range. In order to validate the data analysis program, FDTD is used to calculate the transient E-field of M×N points in a fictitious plane just like the actual PNF sampling signals in the time domain(TD). The calculated results can be considered the actual oscilloscope's sampling output signals. Through nondirective frequency domain near to far field transform and directive time domain near to far field transform, we get the almost same radiation pattern comparing to the FD measurements and software simulation results. Metal plate's bi-static RCS and standard gain horn under TD-PNF measurement were simulated and also were compared with the FD-PNF measurement results. The results showed good agreement. Additionally, Time domain measurement has distinct advantages over frequency domain for gating out unwanted reflections, we also realize time domain far field measurement using a set of frequency domain system with fast sweep frequency function. Through time gating two different antenna's patterns can be obtained just via one measurement. The measure results show that gating can enhance the measurement precision. At last the paper analyzes the gating error and draws the conclusion that TD measurement is not suitable for the narrowband antenna. We also simulated three kinds of UWB antennas which can be used as time domain probes, They are dual polarization resistance loaded dielectric rod with small RCS(VSWR<2 BW: 3—12GHz), Non-dispersive TEM horn with fixed phase center, vivaldi antenna with low profile and wide pattern bandwidth(VSWR<2 BW: 2—8GHz). In additional we analysis and calculate the time domain parameters for vivaldi antenna such as TD radiation pattern, impulse response and signal fidelity etc.
Keywords/Search Tags:UWB Signal, Near Field to Far Field Transform (NFFFTF), Time Domain Far Field, Finite-Difference Time-Domain
PDF Full Text Request
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