HUFF et al.: DIRECTIONAL RECONFIGURABLE ANTENNAS ON LAPTOP COMPUTERS

3221

Fig. 1.

Antenna geometry, including ground plane and substrate, with tuning elements [7].

II. RECONFIGURABLE ANTENNA DESIGN

The reconfigurable antenna used in this study is a single

turn microstrip square spiral, previously reported on in [7].

The antenna geometry and position of switching elements

(hard-wired for proof-of-concept) is shown in Fig. 1. The total

length of the spiral is 80 mm, and is determined by approx-

imately one wavelength around the desired base operational

frequency. The spacing between the first and last linear spiral

sections is 1.0 mm, and the antenna is centered on a grounded

Fig. 2. Laptop computer model (including dimensions) used in EVS

substrate with dimensions of 34 mm

Duroid 58801

simulations and fabricated for experimental portion of position and

electromagnetic environment.

36 mm. The first configuration of the antenna is that of the

base geometry where no tuning elements are added. Hence,

yielding 50 MHz of shared 2:1 VSWR bandwidth between the

moving counterclockwise from the top left corner, the first

and

configurations.

(not grounded), and the second tuning

tuning element is

element is  (an in-line short), creating the

configuration

B. Frequency Reconfigurability

(the unperturbed single turn square spiral). In all configurations,

plane and the H plane as the

the E plane is designated as the

To change the operating frequency of the antenna, only the

plane. The two configurations, reconfigured radiation and

in-line open-circuit is activated, giving the

configuration. In

reconfigured frequency, are described in the following sections.

this configuration, the antenna acts as an open-circuited single-

wavelength resonator, resulting in a shift in the operating fre-

A. Pattern Reconfigurability

quency band from  (3.7 GHz) to  band (6.0 GHz). At this

higher frequency, the coupling to the parasitic arm formed by the

In the original antenna configuration

with no tuning ele-

in-line open is reduced. For the reconfigured frequency mode,

ments activated, the length of the square spiral is approximately

the antenna is linearly polarized with broadside radiation pat-

one wavelength and gives broadside linear polarization along

plane.

terns polarized along the

the diagonal in the  band (3.7 GHz). To reconfigure the pattern,

two tuning elements are required. The first tuning element is a

III. LAPTOP MODEL

short to ground  that has a shorting pin diameter

, equal

to 1.23 mm and located approximately one-quarter wavelength

To perform the study of integration and packaging, a generic

from the feed position. The second element is an open-circuit

model of a laptop computer is developed for FDTD simulation

in the spiral  , that has a spacing width

of 1.0 mm. With

and fabricated for experimental verification. The overall dimen-

config-

the shorting pin and the in-line open present (the

cm )

sions of the generic laptop are: base unit (

uration), the antenna behaves more as a shorted quarter-wave-

cm ). The open angle of the com-

and screen (

length resonator with a parasitic element (the remaining section

puter to simulate actual operation is 105 , and the side profile

of spiral) that helps to maintain the impedance match and create

dimensions of the generic laptop model can be seen in Fig. 2.

a 45 tilted radiation pattern. In this configuration, the antenna is

body, clad

The fabricated model consists of a Lucite2

linearly polarized along the  plane, with operation at 3.7 GHz,

in copper tape across the structure (tacked with solder to ensure

1Duroid 5880

2Lucite

is a registered product of the Advanced Circuit Materials Divi-

is a registered trademark of Lucite International Ltd., Queens Gate

sion, Rogers Corporation, 100 S. Roosevelt Ave, Chandler, AZ 85226 USA.

Queens Terrace, Southampton SO14 3BP, U.K.