| Summary: | 博士 === 國立臺灣大學 === 電信工程學研究所 === 97 === This dissertation presents the study results on two novel designs of retro-directive
antenna array and retro- and reflecto-nulling antenna array using 90 hybrids. Chapter
2 introduces the basic theory of operations of the directive and nulling arrays
and the basic principles of the folding methods by using 90 hybrids. Based on
the folding methods and the theory of operations developed in this chapter, a novel
design on retro-directive antenna array is described in Chapter 3 and a novel design
of nulling array called “retro- and reflecto-nulling array” is described in Chapter 4.
Both the theory and the experiments are studied.
Chapter 3 presents a novel approach to design linear passive retro-directive antenna
arrays by properly making use of 90 hybrids. For a 90 hybrid, when its
direct port and coupled port are terminated with the same reflection coefficient, the
phase difference of the reflected signals at the other two ports are reversed to that
of the incident signals. This then becomes a phase difference reversal circuit (or
a retro-directive circuit) and leads to the design of linear retro-directive antenna
arrays using 90 hybrids. In this approach, all signals from the input ports to the
output ports of the hybrid circuits inherently have the same path length especially
for the planar hybrid circuits. The formulas and a folding method on designing linear
retro-directive array circuits with arbitrary element numbers are presented with the
measurement results of three-element, four-element, and six-element retro-directive
antenna arrays, which are operated at 2.9 GHz.
In 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 and
specular reflection directions without using digital signal processing techniques. At
the beginning of this chapter, a four-element reflecto-nulling antenna array is developed
to verify the theory of operations of the nulling arrays described in Chapter
2. Then, by the folding method described in Chapter 2, a phase difference reversal
circuit developed in Chapter 2 and Chapter 3 can have the phase difference between
two adjacent ports of the phase difference reversal circuit be reversed as −Δϕi if the
phase difference of the input ports is Δϕi. Thus, the retro- and reflecto-nulling array
circuits can be implemented by the array circuits developed in Chapter 2 and Chapter
3 to achieve retro-nulling characteristics and by properly using the phase shifters
to achieve reflecto-nulling characteristics. This approach is implemented by a passive
circuit with the use of 90 hybrids and phase shifters which are properly connected
to the transmitting and receiving antennas. The array then has the retransmitted
radiation pattern giving two nulls at the incident direction θi and specular direction
−θi as the incident wave angle is at θi. The formulas and a folding method
on designing linear retro- and reflecto-nulling array circuits are presented with the
measurement results of three-element, four-element, five-element, and six-element
retro- and reflecto-nulling antenna arrays operated at 2.9 GHz.
|
|---|
