Two Novel Designs of Directive and Nulling Arrayssing 90◦ Hybrids
Date Issued
2009
Date
2009
Author(s)
Hsieh, Sung-Nien
Abstract
This dissertation presents the study results on two novel designs of retro-directiventenna array and retro- and reflecto-nulling antenna array using 90 hybrids. Chapter introduces the basic theory of operations of the directive and nulling arraysnd the basic principles of the folding methods by using 90 hybrids. Based onhe folding methods and the theory of operations developed in this chapter, a novelesign on retro-directive antenna array is described in Chapter 3 and a novel designf nulling array called “retro- and reflecto-nulling array” is described in Chapter 4.oth the theory and the experiments are studied.hapter 3 presents a novel approach to design linear passive retro-directive antennarrays by properly making use of 90 hybrids. For a 90 hybrid, when itsirect port and coupled port are terminated with the same reflection coefficient, thehase difference of the reflected signals at the other two ports are reversed to thatf the incident signals. This then becomes a phase difference reversal circuit (or retro-directive circuit) and leads to the design of linear retro-directive antennarrays using 90 hybrids. In this approach, all signals from the input ports to theutput ports of the hybrid circuits inherently have the same path length especiallyor the planar hybrid circuits. The formulas and a folding method on designing linearetro-directive array circuits with arbitrary element numbers are presented with theeasurement results of three-element, four-element, and six-element retro-directiventenna arrays, which are operated at 2.9 GHz.n Chapter 4, a novel approach is developed to design linear passive retro- and reflecto-nulling antenna array which has two nulls occurring at the incident andpecular reflection directions without using digital signal processing techniques. Athe beginning of this chapter, a four-element reflecto-nulling antenna array is developedo verify the theory of operations of the nulling arrays described in Chapter. Then, by the folding method described in Chapter 2, a phase difference reversalircuit developed in Chapter 2 and Chapter 3 can have the phase difference betweenwo adjacent ports of the phase difference reversal circuit be reversed as −Δϕi if thehase difference of the input ports is Δϕi. Thus, the retro- and reflecto-nulling arrayircuits can be implemented by the array circuits developed in Chapter 2 and Chapter to achieve retro-nulling characteristics and by properly using the phase shifterso achieve reflecto-nulling characteristics. This approach is implemented by a passiveircuit with the use of 90 hybrids and phase shifters which are properly connectedo the transmitting and receiving antennas. The array then has the retransmittedadiation pattern giving two nulls at the incident direction θi and specular directionamp;#8722;θi as the incident wave angle is at θi. The formulas and a folding methodn designing linear retro- and reflecto-nulling array circuits are presented with theeasurement results of three-element, four-element, five-element, and six-elementetro- and reflecto-nulling antenna arrays operated at 2.9 GHz.
Subjects
90 degree hybrids
retro-directive array
nulling array
Type
thesis
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