This document presents a very low-cost copper-wire antenna designed for WLAN operation in the 2.4-GHz band, easily fabricated by bending a single piece of wire. The proposed antenna, characterized by good impedance matching and omnidirectional radiation patterns, shows stable gain and high radiation efficiency, making it suitable for integration into wireless devices. Additionally, the document discusses the potential applications of millimeter wave technology for speech enhancement, highlighting improvements in noise reduction and sound quality for non-air-based speech transmission.

1. REFERENCES 1. INTRODUCTION
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Propagat Lett 3 (2004), 152-153. wireless electronic devices. These antennas are mainly designed to
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(a)
© 2008 Wiley Periodicals, Inc.
VERY-LOW-COST COPPER-WIRE
ANTENNA FOR 2.4-GHZ WLAN
OPERATION
Jui-Hung Chou and Saou-Wen Su
Technology Research Development Center, Lite-On Technology
Corporation, Taipei 11492, Taiwan; Corresponding author:
stephen.su@liteon.com
Received 16 December 2007
ABSTRACT: 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 5 mm is constructed and tested. © 2008 Wiley (b)
Periodicals, Inc. Microwave Opt Technol Lett 50: 2107–2109, 2008;
Published online in Wiley InterScience (www.interscience.wiley.com). Figure 1 (a) Geometry of the proposed very-low-cost copper-wire an-
DOI 10.1002/mop.23589 tenna. (b) Photo of a working sample fed by using a 50- mini-coaxial
cable of length 30 mm. [Color figure can be viewed in the online issue,
Key words: antennas; wire antennas; WLAN antennas which is available at www.interscience.wiley.com]
DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 8, August 2008 2107

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

3. MILLIMETER WAVE CONDUCT SPEECH
ENHANCEMENT BASED ON AUDITORY
MASKING PROPERTIES
S. Li,1,2 J. Q. Wang,1 M. Niu,1 T. Liu,1 and X. J. Jing1
1
Department of Biomedical Engineering, the Fourth Military Medical
University, Xi’an 710032, China
2
The Key Laboratory of Biomedical Information Engineering of
Ministry of Education, and Department of Biomedical Engineering,
School of Life Science and Technology, Xi’an Jiaotong University,
Xi’an 710049, People’s Republic of China; Corresponding author:
sheng@mail.xjtu.edu.cn
Received 17 December 2007
Figure 4 Measured peak antenna gain, average gain, and radiation ABSTRACT: Besides air, the millimeter wave (MMW) provides an-
efficiency. [Color figure can be viewed in the online issue, which is other valuable medium to conduct speech, which may extend the tradi-
available at www.interscience.wiley.com] tional speech detecting method, and provides some exciting possibility
for wide applications. However, the MMW conduct speech is in less in-
telligible and poor audibility since it is corrupted by additive combined
noise. This article, therefore, proposed a simple and efficient way to
quired bandwidth of the 2.4-GHz WLAN band. The experimen- take into account properties of the auditory system in the enhancement
tal data compare favorably with simulation results, which are processes. The parameters of the spectral subtraction algorithm can be
adaptive adjust in a perceptual sense based on a tradeoff between
based on the finite element method. Figure 3 gives the measured
amount of noise reduction, the speech distortion, and the level of musi-
radiation patterns at 2442 MHz. The far-field 2-D radiation cal residual noise. The results from both simulation and listening evalu-
patterns were measured at a 3 3 7-m3 anechoic chamber. ation suggest that the background noise can be reduced efficiently while
Measurements at other frequencies over the 2.4-GHz band of the distortion of MMW radar speech remains acceptable, the enhanced
WLAN operation were also taken, and the obtained results speech also sounds more pleasant to human listeners, resulting in im-
showed similar radiation patterns as those plotted here. Across proved results over classical subtractive-type algorithms. © 2008 Wiley
the operating bandwidth are observed omnidirectional radiation Periodicals, Inc. Microwave Opt Technol Lett 50: 2109 –2114, 2008;
Published online in Wiley InterScience (www.interscience.wiley.com).
patterns in the x–y plane. The measured peak antenna gain, the
DOI 10.1002/mop.23588
average gain for the x–y plane patterns, and the measured
radiation efficiency are presented in Figure 4. The antenna has Key words: non-air conduct; speech enhancement, millimeter wave;
a stable gain level of about 2.4 dBi, which is larger than the auditory masking
average gain by about 0.8 dBi. For the radiation efficiency, it is
found to exceed about 81%. 1. INTRODUCTION
The speech, which is produced by speech organ of human beings
4. CONCLUSION
[1, 2], is well know that it can be spread by means of air, and can
be heard by our ears or detected by acoustic sensors. However, air
A novel compact copper-wire antenna well-suited for WLAN is not the only medium which can spread and be used to detect
operation has been proposed, constructed, and studied. Good ra- speech. For example, voice content can be transmitted by way of
diation characteristics of the antenna have been observed. The bone vibrations. This vibration, therefore, can be picked up at the
antenna with a single copper-wire structure is easy to implement top of the skull using the bone-conduction sensors, strong voicing
and can be a promising solution for keeping cost down. The can be provided using this method [3]. Other medium, such as
antenna is very suitable to use in possible internal spaces within infrared ray, light wave, and laser also can be used to detect the
the housing of communications devices. non air spread speech or acoustical vibrations, however, their
application are limited since the materials in detail are usually
difficult to obtain [4].
Another medium, millimeter wave (MMW, as well as light and
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© 2008 Wiley Periodicals, Inc. research work concentrated on the MMW radar speech. Previous
DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 8, August 2008 2109