Amplifiers – With semiconductor amplifying device – Including particular power supply circuitry
Reexamination Certificate
2001-07-20
2003-09-09
Nguyen, Patricia T. (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including particular power supply circuitry
C330S127000, C323S314000
Reexamination Certificate
active
06617930
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power supply circuit for a transmitter. More specifically, the present invention relates to a power supply circuit for a transmitter used in a communicating instrument used for bi-directional microwave communication-from general households or small-scale offices to broadcast satellites or communication satellites.
2. Description of the Background Art
The market for radio communication utilizing microwaves has been recently developed dramatically, along with developments of various systems including broadcast satellites and communication satellites. At the same time, the Internet has been developed and digital BS broadcast has started, ever increasing the demand for bi-directional communication.
For bi-directional communication between a small-scale office or a general home and a broadcasting station, a broadcast satellite or a communication satellite is used. Currently, it is a dominant practice to use the satellite broadcast, as a signal transmission path for a down signal (downstream) from the broadcasting station to a general home, and to use a telephone line, as a signal transmission path for an up signal (upstream) from a general home to the broadcasting station.
The telephone line used for the upstream supports only a slow rate of communication, and therefore it is not suitable for exchanging motion picture, for example, hindering promotion of satellite multimedia applications. Thus, attempts have been made to enable bi-directional communication by introducing satellite communication to the upstream transmission as well.
FIG. 5
shows a concept of bi-directional communication between each home and the broadcasting station through satellite broadcast. Referring to
FIG. 5
, a parabola antenna
51
is provided on the roof, for example, of a broadcasting station
50
, and parabola antennas
62
and
63
are provided on the roofs of homes
60
and
61
, respectively. Through broadcasting satellite
70
, microwave bi-directional communication is performed between each of the parabola antennas
62
and
63
of respective homes and parabola antenna
51
of broadcasting station
50
. For bi-directional communication, microwave of 12 GHz band is used for one direction and microwave of 14 GHz band is used for the other direction. An LNB (Low Noise Block down Converter) similar to the one used in the conventional system for satellite broadcast reception is used as a receiver for bi-directional communication, and a transmitter is newly provided.
FIG. 6
is a block diagram showing a main portion of such a transmitter. The transmitter is positioned close to an outdoor parabola antenna of a home. An indoor unit, not shown, is provided in the house, and a signal for an image input through a terminal such as personal computer is converted to an intermediate frequency signal of 1 GHz, for example, superposed on a DC voltage of 12V, for example, by means of a coaxial cable, and transmitted to the transmitter.
In the transmitter shown in
FIG. 6
, an input intermediate frequency signal is applied to an IF circuit
1
through a capacitor C
3
. Capacitor C
3
prevents the DC voltage from being input to IF circuit
1
. IF circuit
1
amplifies the intermediate frequency signal to obtain a prescribed gain, and applies the result to an RF circuit
3
. RF circuit
3
mixes the intermediate frequency signal and a local oscillation signal from a local oscillation circuit
4
, so as to convert to a microwave having higher frequency than the intermediate frequency signal. The microwave signal obtained by conversion is further amplified to an appropriate level, input to a power amplifier
5
to be amplified to a high power signal, and thereafter, transmitted.
The input DC voltage is supplied through a coil L
1
to a power supply circuit
2
. Power supply circuit
2
includes a switching regulator circuit
6
, dropper regulator circuits
7
and
8
, and a voltage converter circuit
9
. Switching regulator circuit
6
converts the input DC voltage of 13V to 26V to a positive DC voltage of 12V, for example. The positive DC voltage output from switching regulator circuit
6
is applied to dropper regulator circuits
7
and
8
as well as to voltage converter circuit
9
.
Dropper regulator circuit
7
converts the positive DC voltage of 12V from switching regulator circuit
6
to a voltage value appropriate for voltage supplied to power amplifier
5
, for example, 10V, and supplies the resulting voltage to power amplifier
5
. Dropper regulator circuit
6
converts the voltage from switching regulator
6
to a positive voltage appropriate for voltage supplied to IF circuit
1
, RF circuit
3
and local oscillation circuit
4
, for example, 5V, and supplies the resulting voltage to respective circuits. Voltage converter circuit
9
converts the positive DC voltage input from switching regulator circuit
6
to a negative voltage of −5V, for example, and supplies the same to RF circuit
3
.
In power supply circuit
2
, dropper regulator circuits
7
and
8
are constant voltage circuits converting the positive, 12V DC voltage to +10V and +5V, respectively, for example, while voltage converter circuit
9
converts +12V to −5V.
FIGS. 7 and 8
illustrate an operation of the voltage converter
9
shown in FIG.
6
. Voltage converter circuit
9
includes an oscillation circuit
91
, a frequency dividing circuit
92
, a level converting circuit
93
and a negative voltage generating circuit
94
. Oscillation output of oscillation circuit
91
is divided into two by frequency dividing circuit
92
, for example, and the voltage level is converted by level converting circuit
93
from 12V to 5V. By the negative voltage generating circuit
94
, −5V is generated. In negative voltage generating circuit
94
, first, switches SW
2
and SW
4
are turned off as shown in FIG.
7
and thereafter, switches SW
1
and SW
3
are turned on. In this state, the input voltage V+ is charged to capacitor C
1
through the path of V+→SW
1
→C
1
→SW
3
→GND.
After the end of the charge cycle, a pump cycle starts, in which switches SW
1
and SW
3
are turned off as shown in
FIG. 8
, and thereafter, switches SW
2
and SW
4
are turned on. In this state, charges that have been stored in capacitor C
1
are shifted to capacitor C
2
for charging, by the closed loop of C
1
→SW
2
→C
2
→SW
4
.
After the pump cycle, the operation goes to the first charge cycle, and the above described operations are repeated. Assuming that the resistance RL is infinite in the initial state, Vout is at the potential of −V with respect to GND level, when Vout to GND are viewed. Namely, −5V is output at the Vout terminal.
As shown in
FIGS. 7 and 8
, voltage converter
9
converts a positive (+) potential to a negative (−) potential by the charging/discharging of charges to and from capacitors C
1
and C
2
. Therefore, when there is a large current flowing to the load, the output potential lowers. Therefore, it is necessary to provide a DC voltage higher in absolute value than the output voltage −5V, and therefore, it is necessary for switching regulator circuit
6
to provide the voltage of +12V to voltage converter circuit
9
.
However, a voltage of +12V is output from switching regulator circuit
6
, which is lowered to +10V by dropper regulator circuit
7
, and in addition, a large current flows through power amplifier
5
. Therefore, power loss experienced in dropper regulator circuit
7
is wasted. Further, as the current flowing through power amplifier
5
itself is large, there is also a considerable power loss at this portion, increasing power consumption of the overall transmitter. Increase in power consumption requires an expensive power source of the indoor unit that feeds to the DC voltage input and intermediate frequency signals, resulting in increased cost. This partially hinders introduction of the satellite bi-directional communication instrume
Nguyen Patricia T.
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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