HUFF et al.: DIRECTIONAL RECONFIGURABLE ANTENNAS ON LAPTOP COMPUTERS

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in all positions. As predicted by the EVS, positions 1 and 3

provide the antenna with the necessary conditions to effectively

reconfigure the radiation pattern. In position 1, the reconfigured

radiation pattern is different from that of the antenna measured

in free space; the pattern symmetry can be attributed to the

symmetric placement of the antenna with respect to the screen

and the behavior of the antenna on a large, symmetric ground

plane. Measurements with the antenna in position 3 yield al-

most identical results to the free-space reconfigured radiation.

At position 3, the near free-space operation is attributed to the

asymmetric position of the antenna as well as the asymmetric

antenna radiation characteristic. However, radiation in this po-

sition is scalloped slightly due to edge diffraction occurring

at the corner of the screen area (see Fig. 6). This supports the

findings of the EVS that indicate a higher standard deviation

of currents on this portion of the chassis.

Fig. 8. Measured azimuthal radiation patterns showing the effects of scattering

objects at position 4 with horizontal polarization. (a) and (b) Represent the

In position 2, the desired reconfigurability is not observed,

, respectively.

and

reconfigured radiation configurations

and the pattern is only reconfigured to a broader beam. Although

the desired reconfigurability is not observed at this location, the

effects of symmetry from the integration position (with respect

to the screen) are evident in the symmetry of the resulting main

beam, similar to effects observed at position 1. At position 4, the

beam is not successfully reconfigured, and to a lesser degree

resembles operation at position 2. These results demonstrate

the importance of surface currents to the reconfigured radiation

characteristics of this particular antenna.

3) Electromagnetic Environments and Scattering Ob-

jects: In general, the effects of scattering objects and elec-

tromagnetic environments on the overall operation of the

reconfigured radiation configurations are minor at positions

Fig. 9. Measured VSWR of antenna in free space and integrated on laptop for

1, 2, and 3 (not shown here for brevity). This is due to the

the reconfigured frequency configuration

.

antenna positions on the laptop, which are slightly elevated

above the table. However, at position 4 the effects from the

These plots show that scattering objects in the vicinity of the

scattering objects and electromagnetic environments severely

laptop can influence greatly the antenna's performance.

deteriorate the performance of the antenna. At this position,

the electromagnetic environment and scattering objects can

B. Performance of Reconfigured Frequency Configurations

directly influence or alter the radiation characteristics (in both

the

and

configuration), such that the pattern character-

1) Bandwidth and Radiation Characteristics: For the recon-

istics are rendered undesirable. Intuitively, position 4 is not a

figured frequency configurations on the dielectric work surface,

and

(vertically polarized), local placement of the an-

desirable location for an antenna. In this position the antenna

tenna does not significantly shift or deteriorate the resulting

resides in the plane most likely to encounter scattering from

2:1 VSWR bandwidth (Fig. 9). Fig. 10 contains the radia-

random objects placed in the vicinity of the laptop, and also

tion patterns for the antenna with reconfigured frequency in

presents the possibility of the radiating element interacting

all positions. At positions 1 and 2, the antenna experiences a

with the work surface. This is demonstrated when the structure

slight increase in gain at broadside but retains desirable pattern

resides on the conductive surface and the antenna is integrated

characteristics. This characteristic is also seen in position 3,

at position 4. At this position the antenna experiences a massive

dB) in the

configuration (which

but without a significant change in gain. Operation with the

reduction in gain (

employs a grounding via) from grounding through the chassis

antenna in position 4 appears to be acceptable.

and coupling to the conductive surface. This effect is not shown

2) Electromagnetic Environments and Scattering Ob-

specifically in Fig. 7 (the decrease in pattern magnitude is too

jects: For the first three positions, the location of the antenna

large to meaningfully plot within the range of the other antenna

prevents significant interaction with the scattering objects, as

patterns) and is largely an antenna specific issue. However, this

was the case for the reconfigured radiation mode. Position 4

measurement emphasizes that position 4 is least desirable for

again shows problematic behavior. In this configuration, the

this mode of operation. For a different view of this, Fig. 8(a)

pinching of the beam between two scattering objects (a large

and (b) illustrate the effects of the scattering objects on the re-

metal tin and a stack of CDs) is present for both the base and

configurable radiation configurations at position 4 and compare

reconfigured frequency configuration. Although the position

the measured patterns for the antenna and the antenna in the

and type of scattering objects were chosen at random, place-

presence of scattering objects on the dielectric work surface.

ment of an antenna in the most likely plane of scattering objects