
General Antenna Rules
The following general rules should help in maximizing antenna
performance.
1. Proximity to objects such as a user’s hand, body, or metal objects will
cause an antenna to de-tune. For this reason, the antenna shaft and tip
should be positioned as far away from such objects as possible.
2. Optimum performance will be obtained from a quarter or half-wave
straight whip mounted at a right angle to the ground plane. In many
cases, this isn’t desirable for practical or ergonomic reasons, thus,
an alternative antenna style such as a helical, loop, or patch may be
utilized and the corresponding sacrifice in performance accepted.
OPTIMUM
USABLE
NOT RECOMMENDED
3. If an internal antenna is to be used, keep it away from other metal
tracks, and ground planes. In many cases, BE the space around the
(MAY NEEDED)
Figure 25: Ground Plane Orientation
CASE
like GROUND PLANE
components, particularly large items transformers, batteries, PCB
NUT
antenna is as important as the antenna itself. Objects in close proximity
to the antenna can cause direct de-tuning, while those farther away will
alter the antenna’s symmetry.
4. In many antenna designs, particularly
quarter-wave whips, the ground plane acts
VERTICAL λ /4 GROUNDED
ANTENNA (MARCONI)
as a counterpoise, forming, in essence,
a half-wave dipole. For this reason,
adequate ground plane area is essential.
The ground plane can be a metal case or
ground-fill areas on a circuit board. Ideally,
it should have a surface area greater than
the overall length of the quarter-wave
radiating element. However, this is often
not practical due to size and configuration
E
I
GROUND
PLANE
VIRTUAL λ /4
DIPOLE
DIPOLE
ELEMENT
λ /4
λ /4
constraints. In these instances, a designer
must make the best use of the area available
– 24 –
Figure 26: Dipole Antenna