Multiplex communications – Generalized orthogonal or special mathematical techniques – Fourier transform
Reexamination Certificate
1998-06-17
2002-04-30
Luther, William (Department: 2664)
Multiplex communications
Generalized orthogonal or special mathematical techniques
Fourier transform
C330S126000, C375S297000, C708S403000, C455S103000, C370S342000
Reexamination Certificate
active
06381212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to amplifiers; and more particularly, to a power sharing amplifier system for land based mobile radio systems.
2. Description of the Prior Art
T. Ha,
Solid State Microwave Amplifier Design
, John Wiley and Sons, 1981, pages 268-269, shows and describes a 1 by 2 balanced amplifier in Figure 6.33 thereof for amplifying a single signal. Moreover, in the prior art, 1 by N balanced amplifiers are known for amplifying a single signal, where N is greater than 2. For example, known 1 by N balanced amplifiers have a transform matrix, N shared amplifiers, and an inverse transform matrix. The transform matrix has N input ports, wherein one input port receives the signal or signals to be amplified, and all remaining input ports are connected to ground through terminating resistors and the inverse transform matrix combines the signal or signals to a single output port with the remaining output ports connected to ground through terminating resistors. In the prior art, if two or more signals are to be amplified, then a corresponding two or more 1 by N balanced amplifiers are needed and used. In this prior art, multiple input/output signal paths are not used. One disadvantage of this approach is that a separate 1 by N balanced amplifier, and separate N shared amplifiers, are needed and used for each input/output signal path which significantly increases the cost of amplifying multiple signals.
In addition,
FIG. 1A
shows a known cellular configuration for three cellular sectors in a land mobile radio system generally indicated as
20
with three separate low power transmitters
22
,
24
,
26
; three separate amplifiers
28
,
30
,
32
; and three separate antennas
34
,
36
and
38
. One major disadvantage of the standard cellular configuration
20
is that if an amplifier fails then a whole sector loses communication with any mobile subscriber in the sector until the amplifier is repaired or replaced. In view of this, the standard cellular configuration
20
will typically include a respective extra amplifier (not shown) for each of the three separate antennas
34
,
36
and
38
. Thus six amplifiers must be used. Since amplifiers are expensive, this approach increases the cost of the standard cellular configuration
20
.
FIG. 1B
shows a 4 by 4 cellular configuration generally indicated as
40
similar to that shown and described in U.S. patent application Ser. No. 08/683,735, which is hereby incorporated in its entirety by reference. The U.S. patent application Ser. No. 08/683,735 is commonly owned by the assignee of the present application. The 4 by 4 cellular configuration
40
has four separate low power transmitters
42
,
44
,
46
,
48
; a 4th order transform matrix circuit
50
, four power sharing amplifiers
52
,
54
,
56
,
58
; a 4th order inverse transform matrix circuit
60
; and four antennas generally indicated as
62
,
64
,
66
,
68
. The 4th order transform matrix circuit
50
has four input ports
50
a
,
50
b
,
50
c
,
50
d
that respond to four different input signals from the four separate low power transmitters
42
,
44
,
46
,
48
, and provides four transform matrix input signals. The four separate amplifiers
52
,
54
,
56
,
58
respond to the four transform matrix input signals and provide four shared linear power amplified transform matrix signals. The 4th order inverse transform matrix circuit
60
responds to the four shared linear power amplified transformed signals and provides four inverse transform matrix amplified output signals to output ports
60
a
,
60
b
,
60
c
,
60
d
. In effect, the 4 by 4 cellular configuration
40
is characterized by having equal amplitude levels at all amplifiers from any input since a phase shift portion of each signal is presented to each amplifier
52
,
54
,
56
,
58
. In the amplification sharing technique used in the 4 by 4 cellular configurations
40
, each amplifier
52
,
54
,
56
,
58
shares in a substantially equal manner to the amplification of each input signal. Because of this, each shared amplifier
52
,
54
,
56
,
58
may be four times less powerful than the amplifiers used in the standard cellular configuration shown in FIG.
1
A.
FIG. 1C
shows an 8 by 8 cellular configuration generally indicated as
70
similar to that shown and described in U.S. patent application Ser. No. 08/683,735. The 8 by 8 cellular configuration
70
includes eight separate low power transmitters generally indicated
72
, an 8th order transform matrix circuit
74
, eight amplifiers generally indicated
76
, an 8 by 8 inverse transform matrix circuit
78
, and eight antennas generally indicated as
80
.
FIG. 1D
shows a mapping of each input port to a respective output port in the 8th order cellular configuration.
FIG. 1E
shows a chart of phase shifts for the 8th order transform matrix circuit
74
and the 8th order inverse transform matrix circuit
78
in the 8 by 8 cellular configuration.
The reader is generally referred to U.S. patent application Ser. No. 08/683,735 for a more detailed description of the 4 by 4 and 8 by 8 cellular configurations
40
,
70
.
The amplification sharing technique used in the 4 by 4 and 8 by 8 cellular configurations
40
and
70
offers some important advantages over the amplification technique of the standard cellular configuration
20
. For example, in the 4 by 4 cellular configuration
40
, the four separate amplifiers
52
,
54
,
56
,
58
effectively share the amplification of all the input signals, which provide inherent redundancy in the overall amplification of the input signals. Thus, if one amplifier fails, then all sectors still operate and maintain communication between the subscriber and the land mobile radio system. In such a case, the 4 by 4 cellular configurations
40
may be operating in a less desirable operating mode, but nevertheless it still operates and allows additional time for the failed amplifier to be repaired or replaced. Moreover, the 4 by 4 cellular configuration
40
also uses fewer amplifiers than the standard cellular configuration
20
if redundant amplifiers are maintained for each sector. These advantages combine to make the improved cellular configuration
40
less expensive and more reliable than the standard cellular configuration
20
.
However, one disadvantage of the 4 by 4 and the 8 by 8 cellular configuration
40
,
70
shown in
FIGS. 1B and 1C
is that the amplification sharing technique results in intermodulation products between the multiple input signals to the various amplifiers that distort the amplified RF output signal sent to and transmitted by the antennas
62
,
64
,
66
,
68
,
80
. The present invention provides a new and unique way to minimize the undesirable effects of the intermodulation products in the 4 by 4 and the 8 by 8 cellular configuration
40
,
70
, as well as other power sharing amplification systems.
SUMMARY OF THE INVENTION
In its broadest sense, the present invention provides a power sharing amplification system having an N by N transform matrix circuit, N power sharing amplifiers and an N by N inverse transform matrix circuit. The N by N transform matrix circuit has N input ports and responds to M input signals for providing N transform matrix input signals, where M is less than N. The N by N transform matrix circuit has at least one input port that does not receive an input signal. The N power sharing amplifiers respond to the N transform matrix input signals, for providing N amplified transformed signals. The N by N inverse transform matrix circuit responds to the N amplified transformed signals, for providing M inverse transform amplified output signals to N more output ports. The N by N inverse transform matrix circuit has at least one output port that does not provide an output signal to an antenna but instead provide an output for dissipation of intermodulation products. In the power sharing amplifier system of the present invention, M and N are integers greater than 1 and 2 respectively, M is less than N, M is
Luther William
Radio Frequency Systems Inc.
Ware Fressola Van Der Sluys & Adolphson LLP
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