A very-low-cost copper-wire antenna, easily fabricated by bending a single 70-mm-long copper wire two times, for WLAN operation in the 2.4 GHz band (2400-2484 MHz) is presented. The antenna has a very simple structure and is easily fed by using a 50- mini-coaxial cable. A prototype of the proposed antenna with the overall dimensions 40 mm x 5 mm is constructed and tested.
2. comprises a shorter radiating element, a longer radiating ele-
ment, and a shorting portion that connects both radiating ele-
ments. The antenna, overall, is rectangular in shape with the
dimensions 40 mm 5 mm. The shorter radiating element has
a length of 25 mm, and the shorting portion had a length of 5
mm, which the length in total approximately corresponds to a
free-space quarter-wavelength at about 2442 MHz, the center
frequency of the 2.4-GHz WLAN band. The occurrence of the
antenna operating frequency or the fundamental resonant mode
can be fine-tuned by simply adjusting the length of the shorter
radiating element while the length of the shorting portion re-
mains unchanged. However, the gap between the shorter and the
longer radiating elements is determined by the length of the
shorting portion; thus, the length value can not be too small.
The longer radiating element is treated as the ground portion in
this study, the length of which needs to be larger than that of the
Figure 2 Measured and simulated return loss. [Color figure can be shorter radiating element for better impedance matching and
viewed in the online issue, which is available at www.interscience. was selected to be 40 mm in this case.
wiley.com] To test the design prototype of the copper-wire antenna in
the experiment, a short 50- mini-coaxial cable with an I-PEX
connector is utilized. The inner conductor of the coaxial cable
antenna obtained from using a conducting wire, like a spiral wire is connected to the feeding point A at the shorter radiating
for the helical antenna [5]. In this Letter, we present a novel thin element, and the outer braided shielding is connected to the
copper-wire antenna, which shows similar antenna configuration to grounding point B at the longer radiating element. Both the
a PIFA in cross-section, for WLAN operation in the 2.4-GHz band feeding and the shorting points are set at a distance of 3-mm
(2400 –2484 MHz). The proposed antenna is made of a single away from the shorting portion. This distance also has a major
copper wire and constructed by bending the wire two times, which effect on the impedance matching, similar to matching a con-
can effectively reduce the manufacture cost and provide a very- ventional patch PIFA. Good impedance matching over the
low-cost antenna solution. The antenna is ideal for integration into 2.4-GHz band can be obtained by modifying the above-men-
WLAN applications. Details of the antenna and the experimental tioned antenna parameters: both the length of the longer radi-
results of a prototype are demonstrated. ating element and the distance in between the feeding/shorting
point and the shorting portion.
2. ANTENNA DESIGN
Figure 1(a) shows the geometry of the proposed antenna for
operation in the 2.4-GHz band in detail. The antenna is made of 3. RESULTS AND DISCUSSION
a single thin copper wire of 70 mm in length (about 0.8-mm Figure 2 shows the measured return loss of a constructed
diameter in this study) and can easily be fabricated by bending prototype. The obtained impedance, defined by 10-dB return
the copper wire two times into a U shape. The proposed antenna loss, reaches 125 MHz (2398 –2523 MHz) and covers the re-
Figure 3 Measured radiation patterns at 2442 MHz. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com]
2108 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 8, August 2008 DOI 10.1002/mop