ABSTRACT The concept of reflectarrays can be dated back to the

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ABSTRACT
The concept of reflectarrays can be dated back to the early 1960s. A reflectarray can
produce pre-designed radiation characteristics by combining the principles of phased arrays and
geometrical optics without requiring a complicated feeding network. It is broadly used to steer
reflection beams to the desired directions as in a phased array. Reflectarray operates using an
array of passive elements, whose individual reflection phase is dependent on the dimension of a
resonant structure, and forms a planar reflection phase front. As a result, the main beam can be
switched to different directions by controlling the phase shifts to the reflected signal of all the
elements on the reflectarray. Prior to the design of reflectarray, infinite periodic array approach
was used to simulate the single resonator element in order to examine the reflection phase
characteristics of such element under the mutual influences of an infinitely large array
environment.
The maximum range of the phase change of a unit element will affect the reflectarray
performance. In the effort of optimizing a single element, varying the resonator size and adding
loading element are among the most common techniques used. The desired phase change for the
single element is that it can cover one 360◦ cycle which then it is sufficient for narrowband
operation, as the phase can be wrapped to attain larger phase variations. In my research project,
several reflectarrays with different types of radiating elements have been studied. Higher order
modes of the resonators are excited. With the use of an array of long rectangular patches, they
can form a reflectarray that can achieve broad bandwidth.