Novel Varactor-Loaded Phasing Line for Reflectarray Unit Cell with Large Reconfigurability Frequency Range - New Contributions in Information Systems and Technologies - page 3

and 25° in the H-plane. The above reconfigurable reflectarray is very advantageous
with respect to the active reflectarrays available in literature. As a matter of fact, the
proposed antenna allows to obtain a very high reconfiguration degree through the
integration of a single varactor diode, thus reducing the complexity of the electronics
controlling board. Furthermore, the higher versatility of the proposed radiating
structure allows to simultaneously optimize different radiation features such as:
antenna bandwidth, reconfigurability angular range, polarization agility. In a previous
conference contribution [9], the authors already show the capabilities to optimize the
varactor loaded unit cell for wide angle beam-steering applications. At this purpose, a
reduced size cell 0 at 11.5 GHz is properly designed to

reconfigure the radiation pattern within an angular region greater than about 40°. As
further development, in this work, the unit cell proposed in [9] is properly redesigned
to achieve beam-scanning and/or reshaping pattern capabilities within a broader
frequency range. In particular, the unit cell operational band is improved by adopting
a wideband varactor loaded phasing line, composed by a couple of radial stubs. The
designed cell is extensively simulated at different frequencies, showing a very good
behavior within a large frequency range. As a matter of fact, all phase curves
computed between 11.25 GHz and 12.6 GHz show a maximum phase variation
ranging from 290° up to 330°, thus ensuring good reconfiguration capabilities. This
result is very interesting, as the achieved reconfigurability frequency range (~ 1.35
GHz) is about 3.4 times greater than that obtained for the unit cell tuned by a simple
linear phasing line [9]. A preliminary experimental test is also reported on a 10 GHz
prototype to confirm the validity of the proposed approach.

ʔ x× ʔ y=0.46 ʻ 0 ×0.46 ʻ

2 Reflectarray Unit Cell with Large Reconfigurable

Frequency Range

The unit cell layout proposed in this work is illustrated in Fig. 1. It consists of a
rectangular patch aperture-coupled to a microstrip line, which is composed by a
couple of radial stubs. One end of the line is loaded by a varactor diode, that allows a
dynamical tuning of the phase reflected by the cell. As demonstrated in the following
sections, this novel phasing line geometry allows to improve the reconfigurability
frequency range. The validity of this configuration is numerically tested through the
design of a reconfigurable reflectarray unit cell operating at 11.5 GHz.

Fig. 1. Unit cell layout: (a) top view; (b) side view