Mobile communication system having multi-band antenna

Details Mobile communication system having multi-band antenna Mobile communication system having multi-band antenna

2002-10-15

2003-12-09

Maung, Nay (Department: 2684)

Telecommunications

Transmitter and receiver at same station

Radiotelephone equipment detail

C455S552100, C455S566000, C343S895000

Reexamination Certificate

active

06662021

ABSTRACT:

PRIORITY
This application claims priority to an application entitled “Mobile Communication System Having Multi-band Antenna” filed in the Korean Industrial Property Office on Oct. 13, 2001 and assigned Serial No. 2001-63239, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile communication system, and more particularly to a mobile communication system having a multi-band antenna, which may be employed in a portable mobile communication system and allows the communication to be smoothly carried out in different frequency bands.
2. Description of the Related Art
Mobile communication systems have made surprising commercial progress not only in Korea but also in the world. All over the world, one important step in the progress of mobile communication systems is the change from analog transmission to digital transmission. On the basis of digital transmission, mobile communication systems having dual operation modes, that is, which can be operated in either CDMA or PCS mode, are now being developed as private portable mobile communication systems.
Further, according to the regulation E911 of the Federal Communication Commission (FCC) it is anticipated that future mobile communications in the United States should provide a global positioning function. E911 of FCC recommends that mobile communication terminals should be able to transmit their location, that is, should be traced by a wireless positioning system, for example, by a global positioning system (GPS) satellite. Therefore, mobile communication terminals will be required to have an antenna capable of receiving the signal of GPS band, which is 1.575 GHz.
In general, a mobile communication terminal capable of receiving the GPS signal employs a chip-type GPS antenna, which will be described in detail hereinafter.
FIG. 1
is a schematic view including a block diagram of a conventional mobile communication system capable of receiving signals of triple bands.
FIG. 1
shows the construction of a mobile communication terminal
10
for performing communication by receiving either a signal of the GPS band or other signals of other bands. The mobile communication terminal
10
has two antennas which selectively receive signals of bands different from each other.
That is, in the mobile communication terminal
10
, signals with frequencies of CDMA and PCS bands are synchronized and received by a dual band antenna
12
, while a signal with a frequency of the GPS band is synchronized and received by a GPS antenna
30
. “Dual Band Antenna for Wireless Transmitter/receiver” disclosed in Korean Patent Laid-Open No. 1999-0072602 and U.S. Pat. No. 6,198,440 B1 issued to Samsung Electronics, Co., Ltd., the contents of which are incorporated by reference, describes an antenna that may be utilized as the dual band antenna
12
, while a GPS band antenna realized as a chip may be utilized as the GPS antenna
30
.
A signal with a frequency of the CDMA/PCS bands received by the dual band antenna
12
is supplied to a separator
50
through a matching circuit
40
, which matches impedance between the dual band antenna
12
, and a circuit in the mobile communication system. The separator
50
separates the signal with frequencies of CDMA/PCS bands received through the dual band antenna
12
into a signal with a frequency of CDMA band and a signal with a frequency of PCS band, and supplies the separated signals to a CDMA duplexer
60
and a PCS duplexer
70
, which are connected with output terminals. In addition, the separator
50
supplies a signal received from the CDMA duplexer
60
or the PCS duplexer
70
to the dual band antenna
12
through the matching circuit
40
.
FIGS. 2 and 3
are Smith charts that illustrate impedance matching characteristics of the dual band antenna
12
at the CDMA/PCS bands when it is in retracted and extended states in free space, obtained from measurements by means of a mobile communication phone model SCH-8500, which is produced and sold by Samsung Electronics, Co., Ltd., in which the dual band antenna
12
having the same construction as that in the disclosed in U.S. Pat. No. 6,198,440 is employed. In this case, the impedance was measured at connection nodes between the separator
50
and the CDMA/PCS duplexers
60
and
70
. The impedance matching characteristics is measured by using a Network Analyzer 8753E manufactured by Agilent company. A vertical axis in graph of
FIGS. 2 and 3
indicates Voltage Standing Wave Ratio (VSWR) where a bottom value is 1 and its value is increased upward by one per each division in the graph. And, a horizontal axis in graph of
FIGS. 2 and 3
indicates Frequency. Also, in graph of the FIGS., frequency and VSWR as to the points
1
to
5
indicated as &Dgr; are mentioned on right side and top part, respectively. For example, in
FIG. 2
, the frequency of &Dgr;
1
is 824 MHz and the VSWR of &Dgr;
1
is 1.5399. The above are applicable identically to the other figures showing impedance matching characteristics in this application. Further,
FIGS. 5
to
8
illustrate antenna gain patterns at the CDMA/PCS bands in free space, obtained from measurements for the dual band antenna
12
employed in the above mobile phone model.
The two duplexers
60
and
70
each supply the CDMA and PCS band frequencies separately outputted from the separator
50
to CDMA RF section
110
comprising communication signal processing section and PCS RF section
120
, and also supplies the RF signal outputted from the CDMA RF section
10
and PCS RF section
120
to the separator
50
. The CDMA RF section
110
modulates the signal received from the CDMA duplexer
60
and supplies the modulated signal to the controller
90
, or modulates a signal to be transmitted that is inputted from the controller
90
and supplies the modulated signal to separator
50
. The PCS RF section
120
modulates the signal received from the PCS duplexer
70
and supplies it to the controller
90
, or modulates the signal to be transmitted that is inputted from the controller
90
to a signal of a PCS band and supplies it to the separator
50
.
The controller
90
has the functions of a control section in a general dual mode mobile communication system such as a mobile phone usable as either a CDMA or a PCS mobile phone. Therefore, the controller
90
either reproduces the voice from a signal received from the CDMA RF section
110
or the PCS, or supplies the voice signal to the CDMA RF section
110
or the PCS RF section
120
.
Meanwhile, a GPS filter
80
connected with the GPS antenna
30
filters signals received thereto and passes only the GPS band signal, thereby supplying it to a GPS signal processing unit
100
in controller
90
. The GPS signal processor
100
demodulates a signal of GPS band inputted thereto, thereby generating three-dimensional information for global positioning.
FIGS. 4 and 9
illustrate impedance matching data at the GPS band in free space state and an antenna gain pattern in a retracted state, obtained from measurements by means of the GPS antenna
30
employed in the above mobile communication phone model SCH-8500.
However, the conventional mobile communication system having the construction as shown in
FIG. 1
is disadvantageous in that it has a separate GPS antenna
30
for receiving the signal of GPS band, which makes the construction of the system complicated.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a mobile communication system which has an antenna construction capable of smoothly receiving frequencies of three bands which are different from each other.
It is another object of the present invention to provide a mobile communication system which employs an integrated antenna having a dual helical construction capable of receiving frequencies of either the CDMA/PCS bands or the GPS band with a minimum of loss.
It is still another object of the

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