Pulse or digital communications – Spread spectrum
Reexamination Certificate
2000-08-07
2004-11-16
Tse, Young T. (Department: 2634)
Pulse or digital communications
Spread spectrum
C375S316000, C375S345000, C375S349000
Reexamination Certificate
active
06819706
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio frequency (hereinafter, referred to simply as RF) receiving device of a mobile radio communication base station system in a CDMA (code division multiple access) system.
More particularly, the present invention relates to a control device for controlling power level between frequency assignment, in an RF receiving device of a mobile radio communication base station system in a CDMA system which down-converts an RF received signal into intermediate frequency signals for three frequency assignment, converts the down-converted three frequency assignment IF signals into digital signals, and executes a QPSK (quadrature phase shifting keying) demodulation and a channel filtering for each frequency assignment in a digital manner, whereby it prevents the performance deterioration of all channels due to the power level difference between the frequency assignment.
2. Discussion of Related Art
A general mobile radio communication base station system in a CDMA system includes a switching system and a cell equipment. Of course, the above system contains a large number of functional devices which are all embodied with various kinds of equipments.
The key part of the mobile radio communication base station system is composed of a channel card, a sector interface card, an analog common card and a digital shelf on which a terminal card is packaged. Additionally, it contains a tranceiver shelf which up-converts an IF signal outputted from the digital shelf in an ultra high frequency (UHF) signal and reversely, down-converts the UHF signal into the IF signal. In the tranceiver shelf the sector interface card is installed to couple baseband forward signals received from the channel cards and up-convert the coupled signal into the IF signal. The sector interface card receives the coupled baseband transmitting signals coupled from the analog common cards and couples and amplifies the received signals. The coupled signal is coupled, through a low-pass filter (LPF), to the IF signal, i.e., the delayed signal by the phase of 0° and 90° of 4.95 MHz and transmitted as the IF signal of 4.95 MHz, through a band-pass filter (BPF), to an RF rack. Therefore, the RF rack converts the received IF signal of 4.95 MHz into the UHF signal, for transmitting the converted signal through an antenna.
Now, an explanation of the construction and operation of the general mobile radio communication base station system will be discussed.
FIG. 1
is a block diagram illustrating the construction of a general mobile radio communication base station system. In construction, the system comprises: a base station control processor (BCP)
2
which operates and controls one base station; a base station interconnection network (BIN)
3
which serves as a packet router between the base station and a control station
1
via a line E
1
or T
1
and interfaces high-level data link control (HDLC) packet data between the processors within the base station; a time and frequency unit (TFU)
4
which generates a reference frequency and a timing synchronizing signal to thereby execute the synchronization for each processor within the base station and the timing synchronization with an adjacent base station; a digital unit (DU)
5
composed of a first digital unit
5
a
and a second digital unit
5
b
, which modulates/demodulates the data signal and voice signal transmitted/received through a CDMA channel; and an RF unit (RFU)
6
composed of a first RF unit
6
a
and a second RF unit
6
b
, which converts an UHF signal received from a mobile station into an IF signal to thereby transmit the converted IF signal to the digital unit
5
, receives the IF signal inputted from the digital unit
5
to thereby convert the received IF signal into the UHF signal, and amplifies the converted UHF signal to a predetermined level to thereby execute space-radiation for the amplified UHF signal. The RF unit
6
is divided into an RF receiving device and an RF transmitting device.
Under the general mobile radio communication base station system in the CDMA system, the construction of a prior art RF receiving device is shown in FIG.
2
.
As shown, the conventional RF receiving device includes an RF receiving antenna
10
, a receiving unit
20
, first to third RF down-converters
30
,
31
and
32
by frequency assignment, first to third analog IF processors
40
,
41
and
42
by frequency assignment, and first to third channel cards
50
,
51
and
52
by frequency assignment.
The antenna
10
and the receiving unit
20
are used commonly for all frequency assignment and the first to third RF down-converters
30
,
31
and
32
and the first to third analog IF processors
40
,
41
and
42
are used by each frequency assignment. And, each of the first to third channel cards
50
,
51
and
52
is used by one or more by frequency assignment. For instance, the RF receiving device in the CDMA system supporting four frequency assignment includes one antenna, one receiving unit, four RF down-converters, four analog IF processors, and four or more channel cards.
Now, an explanation of the operation of the prior art RF receiving device supporting the three frequency assignment will be discussed.
First, the receiving unit
20
receives the RF signal received from the antenna
10
, limits the band of the received signal by using a band-pass filter (which is not shown in the drawing), amplifies the filtered signal to a predetermined level by means of a linear noise amplifier (which is not shown in the drawing), and outputs the amplified RF signal to the first to third down-converters
30
,
31
and
32
, respectively. The first to third down-converters
30
,
31
and
32
receive the RF signal from the receiving unit
20
, down-convert the received RF signals into IF signals by using two-stage mixer and local oscillator (which are not shown in the drawing), and output the down-converted frequency assignment IF signals to the first to third analog IF processors
40
,
41
and
42
. In other words, each of the first to third down-converters
30
,
31
and
32
primarily down-converts the received RF signal into the IF signal of about 70 MHz through the local oscillator and mixer at the first stage and secondarily down-converts the received IF signal of 70 MHz into the IF signal of 4.95 MHz through the local oscillator and mixer at the second stage. At the same time, each of the first to third down-converters
30
,
31
and
32
limits the band of the down-converted IF signal by using an SAW filter having the pass band of 1.25 MHz corresponding to the bandwidth of frequency assignment 1FA. The first to third analog IF processors
40
,
41
and
42
receive the down-converted IF signals outputted from the first to third RF down-converters
30
,
31
and
32
, divide the received signals into the signals on I/Q channels to down-convert the signals on the I/Q channels into baseband signals, execute a quadrature phase shifting keying (QPSK) demodulation for each of the baseband signals, and convert the analog baseband signals on the I/Q channels into digital signals. And, the first to third analog IF processors
40
,
41
and
42
execute multiplexing for the digital baseband signals on the I/Q channels and transmit the multiplexed signals to the first to third channel cards
50
,
51
and
52
. The first to third channel cards
50
,
51
and
52
receive the multiplexed digital baseband signals on the I/Q channels by each frequency assignment and execute a CDMA demodulation for each of the received signals by the frequency assignment.
However, the above conventional RF receiving device of the mobile radio communication base station system in the CDMA system suffers from problems that the extension of system is carried out by one frequency assignment, because the RF down-converter and the analog IF processor are used by each frequency assignment, that the size of the base station system as well as the RF receiving device system is bulky, because three RF down-converters and three an
Bryan Cave LLP
Hyundai Electronics Ind. Co. Ltd.
Weigell Charles T. J.
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