Telecommunications – Transmitter – Measuring – testing – or monitoring of transmitter
Reexamination Certificate
1999-08-26
2003-09-23
Nguyen, Lee (Department: 2682)
Telecommunications
Transmitter
Measuring, testing, or monitoring of transmitter
C455S103000, C455S104000
Reexamination Certificate
active
06625427
ABSTRACT:
This Application claims the benefit of the earlier filing date of Japanese Patent No. 10-240731, filed Aug. 26, 1998, the entire contents of which are hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a multicarrier type radio transmission apparatus for combining signals of a plurality of channels with a plurality of carrier frequencies into one signal to effect radio transmission.
This application is based on Japanese Patent Application No. 10-240731, filed Aug. 26, 1998, the content of which is incorporated herein by reference.
The individual amplification system was first put into practice as the amplification system in the multicarrier radio transmission apparatus. In the radio transmission apparatus of individual amplification system, amplifiers
10
-
1
,
10
-
2
, . . . ,
10
-n of a number equal to the number of carrier frequencies (the number of channels) used are provided as shown in FIG.
1
and transmission signals of the respective channels (signals from signal generators
12
-
1
,
12
-
2
, . . . ,
12
-n) are amplified by the respective amplifiers
10
-
1
,
10
-
2
, . . . ,
10
-n. Since the signals input to the respective amplifiers
10
-
1
,
10
-
2
, . . . ,
10
-n are signals each corresponding to one of the channels, there occurs no possibility that the signal of each channel will interfere with the signal of another channel. Thus, the amplifiers
10
-
1
,
10
-
2
, . . . ,
10
-n can be operated in a high-efficiency operating region. Further, it is advantageous in the heat radiation because the amplifiers
10
-
1
,
10
-
2
, . . . ,
10
-n are separately provided for n channels.
Output signals of the amplifiers
10
-
1
,
10
-
2
, . . . ,
10
-n are combined in power by a power combiner
18
and supplied to an antenna (not shown). In order to prevent signals reflected from the power combiner
18
from being fed back to the amplifiers
10
-
1
,
10
-
2
, . . . ,
10
-n and causing distortion in the amplified signals, it is necessary to insert isolators
16
-
1
,
16
-
2
, . . . ,
16
-n between the amplifiers
10
-
1
,
10
-
2
, . . . ,
10
-n and the power combiner
18
so as to maintain isolation between the channels. However, if the isolators
16
-
1
,
16
-
2
, . . . ,
16
-n are inserted, there occurs a problem that great loss occurs to produce a large amount of heat.
Further, in order to simplify the construction of the power combiner
18
, it is necessary to supply the amplified signals to the power combiner
18
via band-pass filters
14
-
1
,
14
-
2
, . . . ,
14
-n having high channel selectivity. However, since the pass bands are fixed in the conventional filters, it is impossible to change the frequency of the carrier signal of each channel if the pass bands of the filters
14
-
1
,
14
-
2
, . . . ,
14
-n are set to correspond to the bands of signals of the respective channels output from the signal generators
12
-
1
,
12
-
2
, . . . ,
12
-n. In the actual transmission system, there is a request for changing the carrier frequency of each channel to a carrier frequency of another channel assigned to the system or there will be a request for changing the bandwidth of the carrier frequency in the future, but the individual amplification system cannot cope with the request. In order to cope with the request at least to some extent, the pass bands of the filters
14
-
1
,
14
-
2
, . . . ,
14
-n are set equal to each other and the carrier frequency band of all of the channels is set as the pass band. However, in this case, it is also necessary to insert the isolators in order to improve the channel selectivity. Therefore, the power combiner
18
becomes complicated in construction.
In order to solve the problem of the individual amplification system, a collective amplification system was developed. As shown in
FIG. 2
, in the collective amplification system, signals of carrier frequencies of the respective channels output from the transmission signal generators
12
-
1
,
12
-
2
, . . . ,
12
-n are first combined by a power combiner
22
and then collectively amplified by an amplifier
24
. Thus, since the amplifier
24
is not provided in the succeeding stage of the amplifier
24
, it becomes unnecessary to connect an isolator in the preceding stage of the power combiner
22
and a problem of loss and heat generation which occurs in the individual amplification system by the presence of the isolators will not occur. However, since a plurality of channel signals are simultaneously input to the amplifier
24
, the linearity of the amplifier
24
becomes important in order to prevent inter-modulation distortion between the channel signals (generally, the high linearity operation and the high-efficiency operation conflict with each other), but in recent years, the high-efficiency operation of a linear amplifier can be attained by various technical improvements. In this respect, the advantage in efficiency of the collective amplification system is recognized.
However, in the collective amplification system, the operation efficiency of approx. 40% at maximum can be attained when the maximum permissible number of channels are received, but if there is an unused channel, the efficiency is lowered. This is because the amplifier
24
must be operated in a low-efficiency operating region (low input power portion) when the number of channels used is small since the input power to the amplifier
24
is changed according to the number of channels used. Further, in the collective amplification system, since heat generation is concentrated in one portion of the amplifier
24
, it becomes necessary to take a large-scale heat radiation measure. Since the number of accommodated channels is determined by the maximum permissible number of channels of the amplifier
24
and the value of the maximum permissible power of the filter
26
, there occurs a problem that it is difficult to increase the number of accommodated channels after designing of the system. Further, there occurs a problem that large permissible power becomes necessary as the specification of the filter
26
in order to deal with a large number of channels.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to solve a problem of a conventional multicarrier radio transmission apparatus of individual amplification system.
Another object of the present invention is to provide a radio transmission apparatus which can prevent inter-modulation distortion between channels in the amplifier and reduce the adjacent channel leakage power to attain the high-efficiency operation of the amplifier higher than the efficiency of the conventional individual amplification system.
Still another object of the present invention is to provide a radio transmission apparatus which is excellent in heat radiation and can attain the high-efficiency operation irrespective of the utilization factor of the channels.
Another object of the present invention is to provide a radio transmission apparatus which is highly flexible with respect to an increase or decrease in the number of accommodated channels.
Another object of the present invention is to provide a radio transmission apparatus which can cope with a difference in the transmission rate with high flexibility.
A radio transmission apparatus according to the present invention performs radio transmission by use of a plurality of carrier frequencies and comprises signal processing systems each including a transmission signal generator for generating a signal of one carrier frequency, an amplifier for amplifying the signal generated from the transmission signal generator, and a variable band-pass filter for permitting only the signal of the one carrier frequency among the output signal of the amplifier to pass therethrough; and a combiner for combining signals output from the variable band-pass filters of the plurality of signal processing systems into one signal and using the signal as a transmission signal.
In the above radio transmission apparatus, since a signal generated from the transm
Kayano Hiroyuki
Suzuki Yasuo
Kabushiki Kaisha Toshiba
Nguyen Lee
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tran Tuan
LandOfFree
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