A novel design of feeding and short-circuiting an internal patch antenna for mobile phones is presented. The patch antenna is with a simple rectangular patch and is fed through and short-circuited to a small ground plane (denoted as antenna ground here) protruded from the main or bottom ground of a folder-type mobile phone. With the presence of the small antenna ground, which can function as a shielding wall, the proposed antenna can be placed in close proximity to the RF shielding metal box in the mobile phone, with very small effects on the antenna performances.

1. 2005 IEEE AP-S
International Symposium
Internal Shorted Patch Antenna
NSYSU for UMTS Mobile Phone
*Saou-Wen Su1, Kin-Lu Wong1, C.L. Tang2, S.H. Yeh2
1
Dept. of Electrical Engineering
National Sun Yat-Sen University
Kaohsiung 80424, Taiwan
2
Computer & Communications Research Lab
Industrial Technology Research Institute
Hsinchu 31040, Taiwan
*E-mail: susw@ema.ee.nsysu.edu.tw
Jul 2005

2. Dept of EE, NSYSU, Taiwan
NSYSU Outlines
(I) Introduction
Configuration of the conventional mobile-phone PIFAs
Mobile-phone PIFAs with a shielding metal box
(II) Design Considerations of the Antenna
Constructed prototype of the internal patch
Parametric studies on the impedance matching
(III) Comparison of the Antenna Performance
Between the proposed patch and the corresponding
conventional PIFA
Advantages over the conventional PIFA designs
(IV) Conclusion
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3. Dept of EE, NSYSU, Taiwan
Conventional PIFAs (1)-
NSYSU On the feeding/short-circuiting PIFAs
Conventional PIFAs mainly comprise: a top patch,
a feeding pin, and a shorting pin
The top patch is usually mounted above a system ground plane;
The shorting and feeding pins, connected to the top patch at proper positions,
have the same length as the distance between the patch and the ground plane
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4. Dept of EE, NSYSU, Taiwan
Conventional PIFAs (2)-
NSYSU Metal box placed away from the PIFAs
Conventionally a large isolation distance (usually > 7 mm)
is required between the internal PIFA and the RF/battery
shielding box for avoiding destructive coupling
MOTL, vol. 32, pp. 87-88, Jan 2002 MOTL, vol. 41, pp. 483-486, Jun 2004 4

5. Dept of EE, NSYSU, Taiwan
Design Consideration (1)-
NSYSU Configuration of the internal patch
Detailed dimensions of the
shorted patch;
Design example for UMTS
folder-type mobile phones
TW/US Patent Pending 5

6. Dept of EE, NSYSU, Taiwan
Design Consideration (2)-
NSYSU Antenna return-loss performance
9.6-dB RL BW (2:1 VSWR)
satisfies the UMTS band,
1920~2170 MHz
Relatively small variations in the
measured RL for three possible
talk positions are seen
The center frequency can be obtained
from the following equation:
c
f≈
4 × (0.5L + W )
where c is the speed of light
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7. Dept of EE, NSYSU, Taiwan
Design Consideration (3)-
NSYSU Measured radiation patterns, peak gain
Measurement is for the
Measurement is for the
talk position with α = 15oo
talk position with α = 15
Peak antenna gain level reaches about 3.4 dBi
across the UMTS band
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8. Dept of EE, NSYSU, Taiwan
Design Consideration (4)-
NSYSU Parametric studies on impedance BW
Other parameters are the
Other parameters are the
same as given previously
same as given previously
Increasing h in general increases the
impedance BW;
Feed gap d is inversely proportion to
the center operating frequency
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9. Dept of EE, NSYSU, Taiwan
Design Consideration (5)-
NSYSU Parametric studies on impedance BW
(continued)
Decreasing t leads to a slight decrease
in the center operating frequency,
different from a quick decrease in that
of the conventional PIFA;
Short-circuiting the patch to the
antenna ground is to introduce
additional inductance to compensate
for the capacitive coupling between
the patch and the bottom ground
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10. Dept of EE, NSYSU, Taiwan
Antennas by Comparison (1)-
NSYSU On the surface current distributions
Smaller surface current
distributions are seen
in the portion below
the proposed antenna
ground
Proposed antenna should be
less prone to hand effects on
the performance degradation
Conventional PIFA of size 28 x 15 mm2
(short-circuited by a pin) with h = 6 mm
and t = 2.5 mm
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11. Dept of EE, NSYSU, Taiwan
Antennas by Comparison (2)-
NSYSU Shorted patch with a shielding metal box
Shielding metal box in vicinity to the
antenna and the conventional PIFA
with an isolation distance D
Detailed
Detailed
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12. Dept of EE, NSYSU, Taiwan
Antennas by Comparison (3)-
NSYSU Effects of the metal box on impedance BW
Impedance matching quickly degraded
with a decrease in D
Negligible variations on the impedance
matching over the bandwidth
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13. Dept of EE, NSYSU, Taiwan
Antennas by Comparison (4)-
NSYSU Radiation power contributed from antenna
Proposed antenna and corresponding PIFA are divided into various portions
for investigating each portion that contributes to radiation power
Shorted patch Antenna ground
Proposed antenna
Proposed antenna
Bottom ground
Upper ground
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14. Dept of EE, NSYSU, Taiwan
Antennas by Comparison (5)-
NSYSU Radiation power contributed from antenna
(continued)
Shorted patch
Corresponding
Corresponding
conventional PIFA
conventional PIFA
Bottom ground
Upper ground
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15. Dept of EE, NSYSU, Taiwan
Antennas by Comparison (6)-
NSYSU Radiation power contributed from antenna
Simulated (IE3D) antenna efficiency are normalized with respect to
total antenna efficiency of 81% and 78% for the proposed antenna
and the corresponding PIFA
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16. Dept of EE, NSYSU, Taiwan
Internal Shorted Patch for
NSYSU UMTS Mobile Phone Application
Other possible embodiments:
For bar-type mobile
phone application
Proposed PIFA mounted at the
bottom end of the bottom ground 16

17. Dept of EE, NSYSU, Taiwan
Internal Patch Integrated with
NSYSU Shielding Metal box
UMTS antenna can also be integrated with
a step-shaped shielding metal box served
as an antenna ground plane
More board space on the system circuit
board are released for deploying the RF
modules or other associated components
UMTS antenna integrated with
a step-shaped shielding metal box
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18. Dept of EE, NSYSU, Taiwan
NSYSU Conclusion
Proposed shorted patch antenna can be
arranged to be in close vicinity to the RF
shielding metal box with small coupling
effects between the antenna and the
shielding metal box
More designs of the internal mobile
antenna integrated with the shielding
metal box are foreseen and in progress
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19. Dept of EE, NSYSU, Taiwan
THANK YOU FOR YOUR ATTENTION!
NSYSU
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