本論文主要建立三種用於多埠網路散射矩陣量測之埠數降低方法，以及建立多埠網路分別於微波影像與天線特性量測之應用。
埠數降低法是藉於多埠網路端，連接負載元件，以降低所需量測之埠數，而由較低埠數網路之散射矩陣，求解原多埠網路之散射矩陣。如此則可減少多埠網路量測儀器及校準方法之需求。當所需之量測埠數可降低至二埠時，該多埠網路則可由商用之二埠向量網路分析儀量測。在本論文中，提出三種新的埠數降低法，分別稱為第一型、第二型及第三型。對第一型及第二型埠數降低法，且其所需之量測埠數可降低至二埠。而在第三型中，對互易網路或非互易網路，則可將需測埠數降低至二埠或三埠，所使用之負載元件，並不需全為已知。此三種埠數降低法之推導過程，分別於第二至四章中敘述。由實驗結果顯示，均可得到良好之精確度。此三種埠數降低法，提供了較直接使用多埠網路分析儀簡單之校準方法與儀器需求。
論文第五章係建立一項結合三天線法、天線散射矩陣及第一型埠數降低法，以進行天線增益及結構散射之量測方法。該方法係以反射形式量測，相較於傳統之傳輸形式量測方法，可不需返回之電纜線、極化校準及標準增益天線，實驗結果顯示此方法可得到相當之精確度。
第六章則建立一使用六埠反射儀之微波多向影像量測系統，六埠反射儀係經由功率量測值，計算散射物體之反射係數，以取代習用之向量網路分析儀，以簡化量測系統並可提高量測頻率。由所得之微波影像結果，包含金屬圓柱、四根金屬細圓柱及B-52飛機模型等三種物體，顯示重建之影像品質，與使用網路分析儀相近。
由實驗結果顯示，本論文所建立之三種埠數降低法，可由使用較低埠數之網路分析儀，量得準確之多埠網路散射參數矩陣。此外所建立之兩種多埠網路應用，對於微波多向影像與天線特性量測均有相當實用價值。

In this dissertation, three port reduction methods for multi-port network measurement and two applications of multi-port network for microwave diversity imaging and antenna measurement are presented.
Port reduction method (PRM) is a method to acquire the scattering matrix of an n-port network from the scattering matrix measured at a reduced port order by terminating certain ports. This then relaxes the instrumentation requirement and calibration procedure. As the port order is reduced to two, the scattering matrix of an n-port network can be obtained from the measurement using a conventional two-port vector network analyzer. In this dissertation, we present three novel port reduction methods denoted as type I, type II and type III PRM. For type I and type II PRM, the order of measured ports can be reduced to be two. For type III PRM, the order of measured ports can be reduced to three and two for non-reciprocal and reciprocal network. The terminators used for type III PRM can be partially known. Formulations of three three methods are presented in Chapters 2 to 4. The experiment results show good accuracy. These PRMs can provide simpler calibration procedure and instrumentation than those of directly using an n-port network analyzer.
A method that combine the concept of three-antenna method, antenna scattering matrix and type I PRM for the antenna gain and structural scattering measurement is described in Chapter 5. This method can eliminate the need of long return cable and polarimetric calibration as those using transmission measurement arrangement. Experiment results shows the good accuracy obtained with this novel method.
In Chapter 6, we present a cost-effective microwave diversity imaging system using a six-port reflectometer which measures four amplitude (or power) values to acquire the object scattered field indirectly. One can then relax the complex field measurement using vector network analyzer (VNA). The calibration procedure for this microwave diversity imaging measurement is also described. Experimental results of three types of scattering objects, a metallic cylinder, four distributed line scatterers and a scaled B-52 aircraft model, are presented using the described six-port microwave imaging system.
The three port reduction methods developed in this dissertation are shown can give an accurate result with the use of reduced port VNA for an n-port network scattering matrix measurement. In addition, the two applications of multi-port network are found very useful and practical in the antenna characteristic measurement and microwave diversity imaging.

Cover
Contents
Chapter 1 Introduction
1.1 Motivation and literature survey
1.2 Chapter outline
Chapter 2 Multi-port network measurement using type I PRM
2.1 Formulation
2.2 Experiment and verification
2.3 Summary
Chapter 3 Multi-port network measurement using type Ⅱ PRM
3.1 Formulation
3.2 Experimental and verification
3.3 Summary
Chapter 4 Multi-port network measurement using type Ⅲ PRM
4.1 Formulation
4.2 Experimental and verification
4.3 Summary
Chapter 5 Antenna gain measurement using three-antenna method with type I PRM
5.1 Introduction
5.2 Furmulation
5.3 Experimental
5.4 Summary
Chapter6 Mcrowave diversity imaging using six-port reflectometer
6.1 Introdiction
6.2 Microwave diversity imaging and six-port reflectometer
6.3 Microwave imaging experiment
6.4 Summary
Chapter 7 Conclusion
7.1 Multi-port network analyzer
Chapter 8 Appendix
References

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