Page 1
Nokia Customer Care
2255 (RM-97)
Mobile Terminal
Antenna Description and
Troubleshooting
ISSUE 1 10/2005 Company Confidential ©2005 Nokia Corporation
Page 2
2255 (RM-97)
Antenna Description and Troubleshooting
Contents Page
Introduction ..................................................................................................................................................... 3
Stub Antenna ................................................................................................................................................ 3
Failures and Corrective Measures.............................................................................................................. 4
Installing the stub antenna ......................................................................................................................4
Uninstalling the stub antenna .................................................................................................................5
Damaged RF Feed Pin.............................................................................................................................. 6
Obstructed RF feed pad or missing matching circuit..................................................................... 6
Page 2 ©2005 Nokia Corporation Company Confidential ISSUE 1 10/2005
Page 3
2255 (RM-97)
Nokia Customer Care Antenna Description and Troubleshooting
Introduction
This troubleshooting guide addresses potential failures that affect antenna performance
of the 2255, and discusses methods for correction of these failures.
Stub Antenna
The 2255 uses a single band stub antenna for CDMA CELL band. The antenna radiator is a
flex meander that is wrapped around a plastic connector and overmolded.
Overmolded
plastic
Anchor
Feed contact
Figure 1: Main parts of stub antenna
ISSUE 1 10/2005 ©2005 Nokia Corporation Company Confidential Page 3
Page 4
2255 (RM-97)
Antenna Description and Troubleshooting
Failures and Corrective Measures
Installing the stub antenna
Figure 2 shows the assembly of the stub antenna into the D-cover.
Figure 2: Installing a stub antenna
If no stub antenna is installed, the antenna gain will be degraded by more than 25 dB.
The stub has a hook on the antenna anchor which locks the antenna into the D-cover
when installed. See Figure 3.
Hook
Figure 3: Locking mechanism on antenna anchor
During antenna installation, the antenna anchor passes through a plastic loop in the
C-cover (See Figure 4). The antenna is the last item to be installed during assembly of the
mobile terminal.
Page 4 ©2005 Nokia Corporation Company Confidential ISSUE 1 10/2005
Page 5
2255 (RM-97)
Nokia Customer Care Antenna Description and Troubleshooting
Whip/Stub antenna
Figure 4: Antenna locked into D-cover and plastic loop in C-cover
Uninstalling the stub antenna
During disassembly of the mobile terminal, the antenna needs to be uninstalled first. To
uninstall an antenna, a special extraction tool is needed. The antenna should never be
extracted by force as the antenna and/or the D/C-covers may brake or be damaged.
Use the static portion of the extraction tool to align the tool onto the D-cover. A moving
lever passes though the RF connector hole and releases the hook from D-cover.
Alignment part
Lever
D-cover
RF connector hole
Figure 5: Position of antenna extraction tool onto D-cover
ISSUE 1 10/2005 ©2005 Nokia Corporation Company Confidential Page 5
Page 6
2255 (RM-97)
Antenna Description and Troubleshooting
Damaged RF Feed Pin
The stub antenna has a spring clip feed contact that should properly touch the PWB.
Positioning of this pin is shown in Figure 2.
• If the RF feed pin is broken or bent the pin will not touch the PWB and the stub
antenna must be replaced. If the spring for the RF feed pin damaged, replace the
stub antenna.
• If the RF feed pin of the stub antenna does not touch the PWB, the antenna gain
will degrade by more than 25 dB.
Obstructed RF feed pad or missing matching circuit
If the RF feed pin is obstructed, removed or covered, the RF pin will not touch the PWB
and then the antenna performance will degrade.
• If corrosion is present or the pad is missing, replace the PWB and the mobile
terminal.
• If either pad is obstructed or covered, clean and/or clear the pad.
The antenna matching circuit is positioned next to the RF feed pad. If the matching
circuit is improperly installed or any of the components are missing, the antenna gain
will be degraded by about 25dB.
Matching circuit
Antenna pad
3.9pF
4.7nH
4.7nH
Figure 6: PWB layout of RF feed pad and matching circuit
Page 6 ©2005 Nokia Corporation Company Confidential ISSUE 1 10/2005
Loading...