Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1999-11-05
2002-04-16
Hunter, Daniel (Department: 2749)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S011100, C455S020000
Reexamination Certificate
active
06374119
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a system and method for mobile communications. More specifically, the present invention relates to a system and method for mobile communications which remove blanket areas of communications using a mobile repeater.
(b) Description of the Related Art
Conventional mobile communications systems comprise base stations (BS), base station controllers (BSC), a mobile switching center (MSC), and mobile stations (MS).
The BSs communicate with the MSs using predetermined frequencies, and each BS has a predetermined communications area. Therefore, a plurality of BSs is arranged in a suitable manner so that communications areas of adjacent BSs partially overlap to create a large area where mobile communications can take place.
However, even though with the above-mentioned arrangement an entire city can be covered, blanket areas where no communications are possible come to be formed in underground spaces of large buildings, interior spaces of skyscrapers, etc. As a result, communications service can not be provided to users in such blanket areas.
To solve the formation of the blanket areas, radio frequency (RF) repeaters are provided in those areas.
FIG. 1
is a schematic diagram of a conventional in-building repeater used in code division multiple access (CDMA) communications.
As shown, the in-building repeater comprises duplexers
11
and
16
; low noise amplifiers
12
and
17
; pre-amplifiers
13
and
18
; intermediate frequency (IF) modules
14
and
19
; surface acoustical wave (SAW) filters
1
and
4
; mixers
2
and
3
; and power amplifiers
15
and
20
.
An operation of the in-building repeater of the above configuration will now be described.
When RF signals are received from a BS through a directional antenna
10
, the received signals are transmitted to the low noise amplifier
12
in the transmission direction through the duplexer
11
. The low noise amplifier
12
and the pre-amplifier
13
then amplify the signals, and the IF module
14
converts the amplified signals into intermediate frequency signals. After the signals are output from the IF module
14
, noise is removed from the signals in the SAW filter
1
, and then converted into RF signals in the mixer
2
. The converted signals are amplified in the power amplifier
15
, pass through the duplexer
16
, then are radiated through in-building antennas or leakage coaxial cables.
On the other hand, the RF signals transmitted from a MS of a subscriber are received through the in-building antennas or leakage coaxial cables, passed through the duplexer
16
, and amplified by the low noise amplifier
17
and pre-amplifier
18
. The RF signals amplified by the pre-amplifier
18
are converted into IF signals in the IF module
19
, and signal noise is removed through the SAW filter
4
, after which the signals are converted into RF signals through the mixer
3
. The converted RF signals are amplified by the power amplifier
20
, passed through the duplexer
11
, then radiated from the antenna
10
to be transmitted to the BS.
The in-building repeater using the conventional antenna can be used only on a single floor or one particular space of a building. Therefore, in order to radiate the waves to many floors, the leakage coaxial cables are utilized.
However, since waves are radiated only along the paths where the leakage coaxial cable lies in the conventional in-building repeater, a cable of substantial length must be used in large buildings. As a result, transmission loss occurs as signals travel the distance of the cable. In addition, installation of the cable becomes complex with the increased length of the same, and the costs involved in installing the lengthy cable are high.
Optionally, a light dispersion antenna is used which converts the RF signals into light waves and radiates the light signals to the blanket areas in a building.
FIG. 2
is a schematic diagram of an in-building repeater using a conventional light dispersion antenna.
As shown, the repeater comprises duplexers
36
and
40
; low noise amplifiers
22
and
39
; mixers
23
,
25
,
31
, and
34
; filters
24
,
26
,
29
, and
32
; light transmitters
27
and
38
; light receivers
28
and
36
; a light dispersion antenna
41
; and power amplifiers
35
and
37
.
The operation of the repeater using the light dispersion antenna is similar to that of the previously described repeater. But in contrast, the RF signals are converted into light signals to be transmitted through optic cables, and the light signals are radiated to the blanket areas using the light dispersion antenna
41
.
However, the installation of the repeater using the optic cables and light dispersion antenna involves great costs.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a system and method of mobile communications for reducing blanket areas in a building at a low cost.
In one aspect of the present invention, a mobile communications system comprises a base station (BS) transmitting and receiving signals by a predetermined serving frequency signal; a donor module coupled to the BS, the donor module converting output signals of the BS into intermediate frequency (IF) signals and outputting the converted signals to a path, and the donor module converting the IF signals provided from the path into serving frequency signals and transmitting the converted serving frequency signals to the BS; and a plurality of remote modules receiving output signals of the donor module through the path, and converting the signals into the serving frequency signals and outputting the serving frequency signals to a mobile station (MS) within a blanket area, and the remote modules converting the signals into IF signals and outputting the signals to the donor module through the path.
The donor module comprises a first duplexer performing bi-directional communications with the BS; a transmitter converting radio frequency (RF) signals provided through the first duplexer into IF signals, and amplifying and outputting the signals; a second duplexer transmitting the signals of the transmitter to a rigid (RG) cable, the second duplexer receiving IF signals through the RG cable; a receiver converting IF signals transmitted to the second duplexer into RF signals and transmitting the signals to the first duplexer; and a power controller detecting a signal level of the receiver and controlling the power of the transmitter and receiver.
The transmitter comprises a first low noise amplifier amplifying the RF signals provided through the first duplexer; a first mixer converting the RF signals into IF signals; a first surface acoustic wave (SAW) filter filtering output signals of the first mixer to obtain desired IF signals; a first variable attenuator performing power control on output signals of the first SAW filter according to external control signals; a first power amplifier performing power amplification on output signals of the first variable attenuator; a frequency shift keying (FSK) modulator outputting FSK modulated signals; a second variable attenuator controlling power according to control signals of the power controller; a first amplifier amplifying signals of the second variable attenuator; a first low pass filter performing a low pass operation on signals of the first amplifier; and an adder adding signals of the first low pass filter and the first power amplifier, and outputting resulting signals.
The receiver comprises a second SAW filter passing desired IF signals among the IF signals transmitted to the second duplexer; a second low noise amplifier amplifying output signals of the second SAW filter; a second mixer providing status control signals to the second low noise amplifier according to control of the power controller; a third variable attenuator performing power control on output signals of the second mixer according to control of the power controller; a third mixer converting signals of the third variable attenuator into RF signals; a third SAW filter passing desired RF signals amon
Jun Ju-Sung
Lee Sang-Keun
Baker & Botts LLP
Hansol PCS Co. Ltd.
Hunter Daniel
Le Lana
LandOfFree
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