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Mobile Phone Patent Abstract
A power amplifying apparatus for a mobile phone is provided. In
the power amplifying apparatus, a power amplifier uses a transistor
as a power amplifying device, and a non-volatile memory pre-records
the static characteristic measurement data of the transistor. A
DC bias current of the transistor is controlled according to transmission
power of the power amplifier referring to the static characteristic
measurement data, by changing a gate voltage of the transistor,
by changing a drain voltage of the transistor with the gate voltage
fixed, or by changing both the gate voltage and the drain voltage.
Mobile Phone Patent Claims
What is claimed is:
1. A power amplifying apparatus for a mobile phone, comprising:
a power amplifier; and a non-volatile memory for recording an actual
static characteristic measurement data of a specific transistor,
said specific transistor having the actual static characteristic
being arranged in a power amplifying device of the power amplifier,
wherein a DC bias current of the transistor is controlled according
to the transmission power of the power amplifier according to the
static characteristic measurement data.
2. The power amplifying apparatus of claim 1, wherein the DC bias
current is controlled by changing a gate voltage applied to the
power amplifying device according to the static characteristic data.
3. The power amplifying apparatus of claim 1, wherein the DC bias
current is controlled by fixing a gate voltage applied to the power
amplifying device by changing a drain voltage applied to the power
amplifying device according to the static characteristic data.
4. The power amplifying apparatus of claim 1, wherein the DC bias
current is controlled by changing both a gate voltage and a drain
voltage applied to the power amplifying device according to the
static characteristic data.
5. A power amplifying apparatus for a mobile phone, comprising:
a power amplifier; a non-volatile memory for recording an actual
static characteristic measurement data of a specific transistor
that is arranged in a power amplifying device of the power amplifier;
and a bias control circuit for controlling a DC bias current of
the transistor according to the transmission power of the power
amplifier according to the actual static characteristic measurement
data of the specific transistor, wherein the power amplifier, the
non-volatile memory, and the DC bias control circuit are incorporated
in one chip.
6. The power amplifying apparatus of claim 5, wherein the bias
control circuit controls the DC bias current by changing a gate
voltage applied to the power amplifying device according to the
static characteristic data.
7. The power amplifying apparatus of claim 6, wherein the bias
control circuit controls the DC bias current by fixing a gate voltage
applied to the power amplifying device and by changing a drain voltage
applied to the power amplifying device according to the static characteristic
data.
8. The power amplifying apparatus of claim 5, wherein the bias
control circuit controls the DC bias current by changing both a
gate voltage and a drain voltage applied to the power amplifying
device according to the static characteristic data.
Mobile Phone Patent Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an apparatus for extending
the battery life in a mobile communication system. More particularly,
the present invention relates to a power amplifying apparatus for
a Wideband-Code Division Multiple Access (W-CDMA) mobile phone.
2. Description of the Related Art
In order to save the battery life, a power control scheme is used
in that the distance between a mobile phone and a base station is
estimated so that the mobile phone can adjust its transmitting power
to achieve at least minimum required E/I at the receiver. To this
end, the mobile phone monitors its reception power to determine
how much transmission power is to be adjusted. FIG. 3 illustrates
a conventional structure of a power amplifying apparatus of a mobile
phone. In FIG. 3, a high power amplifier (HPA) 21 amplifies the
power of an input signal under the control of an automatic power
controller (APC) 23 and feeds the amplified signal to a transmission
antenna 24. A power monitor 22 serves to monitor the transmission
power received from the HPA 21. The APC 23 controls the transmission
power of the HPA 21 according to the output information received
from a digital signal processor (DSP: not shown) of a phone, or
from the output information from a controlling Central Processing
Unit (CPU) (not shown) and the output monitor 22. The output information
comprises a DC signal, which is produced from a digital signal output
from the DSP or the CPU via a digital-to-analog conversion (DAC)
process. Then, the DC signal is used to control the transmitting
power of the mobile phone.
The power added efficiency (PAE) of the HPA 21 is used to determine
power consumption efficiency, thus it is an important factor in
determining the life span of a battery. FIGS. 4 and 5 illustrate
graphs showing the relationship between the input/output power characteristics
and the PAE. For example, FIG. 4 shows the relative power consumption
information when a GaAs-FET is used as the HPA 21. In such a case,
the maximum PAE is obtained in the vicinity of the peak transmission
power, as shown in FIG. 4. On an average usage of a mobile phone,
a majority of the time is passed in a standby mode requiring less
power consumption, thereby extending the battery life time. However,
when voice transmission is required from the time to time, the peak
transmission power, depending on the transmission environment, is
required.
In view of foregoing in recent years, various suggestions have
been made to extend the life span of the battery by adjusting the
bias current and gate-source voltage. As shown in FIG. 5, a DC bias
current flowing through the HPA 21 is adjusted based on the output
of the HPA 21. Curves P1, P2, and P3 correspond to the output power
with respect to E1, E2, and E3 (PAE). P1 and E1 represent power
conversion efficiency for a relatively low DC bias current, whereas
P3 and E3 represent for a relatively high DC bias current.
In recent years, there has been an increasing tendency of employing
power amplifiers using a GaAs-FET, a transistor having high power
conversion efficiency. With reference to FIG. 6, static characteristics
differ in GaAs-FETs caused by changes in the manufacturing process.
That is, the static characteristics, such as pinch-off voltage and
drain saturated current, are greatly changed due to the manufacturing
differences. To control the drain current (Id) as shown in FIG.
6 to a drain current of a design value, the individual difference
in the static characteristics of different amplification transistors
should be minimized. However, this is impossible in the current
situation. Moreover, to obtain an ideal amplification transistors
having a desired characteristic for the operation of amplifier,
the manufacturing cost has to increased significantly because a
large volume of transistors has to be produced to achieve few transistors
exhibiting the ideal static characteristics.
SUMMARY OF THE INVENTION
It is, therefore, one object of the present invention is to provide
an amplifier that resolves the above shortcomings in such way that
the PAE of the power amplifier during a standby mode is increased.
It is, therefore, an object of the present invention to provide
a power amplifying apparatus for a mobile phone which can increase
the life span of a battery in a normal use state, by precisely controlling
the DC bias current that determines the PAE of the power amplifier.
The above object can be achieved by providing a power amplifying
apparatus, which uses a transistor as a power amplifying device,
wherein a non-volatile memory records the static characteristic
measurements of the transistor. The DC bias current of the transistor
is controlled according to transmission power of the power amplifier
by referring to the pre-recorded static characteristic measurement
data, by changing the gate voltage of the transistor or by changing
a drain voltage of the transistor having the gate voltage fixed,
or by changing both the gate voltage and the drain voltage.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features, and advantages of the present
invention will become more apparent from the following detailed
description when taken in conjunction with the accompanying drawings
in which:
FIG. 1 is a schematic view of a power amplifying apparatus for
a mobile phone according to the embodiment of the present invention;
FIG. 2A is a flowchart illustrating the preliminary process by
a manufacturing company of the power amplifying apparatus shown
in FIG. 1;
FIG. 2B is a flowchart illustrating the operation of a bias controller
shown in FIG. 1;
FIG. 3 illustrates the structure of a power amplifying apparatus
in a conventional mobile phone;
FIG. 4 is a graph showing the relationship between input/output
power characteristics and the PAE in an HPA;
FIG. 5 is a graph showing the relationship between input/output
power characteristics and the PAE in an HPA when a DC bias current
of the HPA is controlled according to the HPA output; and,
FIG. 6 is a graph showing static characteristic data of GaAs-FETs,
when used as power amplifying devices for the HPA.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will be described
hereinbelow with reference to the accompanying drawings. For the
purpose of clarity, well-known functions or constructions are not
described in detail as they would obscure the invention in unnecessary
detail.
FIG. 1 is a schematic view of a power amplifying apparatus (hereinafter,
referred to as an HPA module) for a mobile phone according to the
present invention. In FIG. 1, an HPA 11, a non-volatile memory 12,
and an output monitor 13 are incorporated in the HPA module 1 as
one chip. GaAs-FET is used as a power amplifying device for the
HPA 11 that includes a bias current setting circuit later described
herein. An EEPROM (Electrically Erasable Programmable Read Only
Memory) is used as the non-volatile memory 12, by way of example.
The static characteristic information of the GaAs-FET is pre-recorded
in the non-volatile memory 12. Specifically, the static characteristic
of the GaAs-FET, that is, its Vg-Id characteristic as shown in FIG.
6 is measured, plotted to 16 (=2.sup.4) kinds of data when a 4-bit
EEPROM is used, and recorded in the non-volatile memory 12 before
the HPA module 11 comes into the market.
In FIG. 1, Vd (drain voltage), Pin (input voltage), Vg (gate voltage),
P-monitor (power monitor), Data (data), clock (clock signal), CE
(chip enable), and Pout (output power) are the input/output terminals
of the HPA module 1. When the HPA module 1 is used as a power amplifying
apparatus for a mobile phone, Vd, Pin, Vg, P-monitor, Data, clock,
and CE are connected to a bias control circuit 2 outside the HPA
module 1. The bias control circuit 2 can be implemented using a
phone DSP or a controlling CPU.
FIG. 2A illustrates an operation of manufacturing the HPA module
1 shown in FIG. 1, and FIG. 2B illustrates a flowchart illustrating
the operation of the bias control circuit 2 when the HPA module
1 is used as a power amplifying apparatus for a mobile phone.
Referring to FIGS. 2A and 2B, the non-volatile memory 12 is incorporated
in the HPA module 1, as stated above. Before the HPA module 1 comes
onto the market, the static characteristics of the GaAs-FET (HPA
11) are measured in step al. The measured static characteristics
are recorded in the non-volatile memory 12 in step a2. In step a3,
the HPA module 1 is put on the market.
When the HPA module 1 is used as a power amplifying apparatus for
a mobile phone, the bias control circuit 2 reads data from the non-volatile
memory 12 in step b1, makes a control table in step b2, and optimizes
the output power of the HPA 11 according to the contents of the
control table in step b3.
Optimization of the output power refers to controlling the output
power based on the individual static characteristics of the GaAs-FET
retrieved from the non-volatile memory 12. In other words, the bias
control circuit 2 changes the drain voltage Vd or the gate voltage
Vg applied to the HPA 11 by controlling the DC bias current flowing
through the HPA 11 based on the output power (Pout) of the HPA 11
monitored by the output monitor 13.
Specifically, the bias control circuit 2 reads the static characteristics
of the GaAs-FET (i.e., the Vg-Id characteristic shown in FIG. 6)
from the non-volatile memory 12, then generates a control for setting
a DC bias current based on the read static characteristic information,
and controls the DC bias current so as to maximize the PAE according
to the generated control table. Consequently, the output power of
the HPA 11 is optimized. It should be noted that there are well
known methods in the art in generating such table.
The DC bias current can be controlled in three ways: (1) by changing
the gate voltage Vg; (2) by changing the drain voltage Vd with the
gate voltage Vg fixed; and, by changing both the gate voltage Vg
and the drain voltage Vd.
Using one of the above three methods, the output power of the HPA
11 is optimized since the static characteristics of the GaAs-FET
is already considered and the right current value is selected to
provide a maximum PAE. Hence, the control table made in the bias
control circuit 2 varies depending on which method is used.
When the DC bias current is controlled by changing the gate voltage
Vg, the control table is follows:
TABLE 1 gate voltage Vg DC bias current PAE V.sub.g 1 i.sub.k 1
k1 V.sub.g 2 i.sub.k 2 k2 V.sub.g 3 i.sub.k 3 k3 V.sub.g 4 i.sub.k
4 k4
When the DC bias current is controlled by changing the drain voltage
Vd with the gate voltage Vg fixed, the control table is as follows:
TABLE 2 drain voltage Vd DC bias current PAE V.sub.d 1 i.sub.k
1 k1 V.sub.d 2 i.sub.k 2 k2 V.sub.d 3 i.sub.k 3 k3 V.sub.d 4 i.sub.k
4 k4
When the DC bias current is controlled by changing the gate voltage
Vg and the drain voltage Vd, the control table is as follows:
TABLE 3 gate voltage Vg drain voltage Vd DC bias current PAE V.sub.g
1 V.sub.d 1 i.sub.k 1 k1 V.sub.g 1 V.sub.d 2 i.sub.k 2 k2 V.sub.g
1 V.sub.d 3 i.sub.k 3 k3 V.sub.g 2 V.sub.d 1 i.sub.k 4 k4 V.sub.g
2 V.sub.d 2 i.sub.k 5 k5 V.sub.g 2 V.sub.d 3 i.sub.k 6 k6 . . .
. . . . . . . . .
In case the DC bias current is controlled by varying the gate voltage
Vg, a gate voltage Vg that maximizes the PAE is selected referring
to the control table of Table 1 and applied to the HPA 11, thereby
optimizing the output power of the HPA 11.
The DC bias current applied by the bias control circuit 2 based
on the drain voltage Vd and/or gate voltage Vg flows through the
HPA II through the bias current setting circuit. The structure of
the bias current setting circuit is well known, thus its detailed
description is omitted here.
The consumption power of the HPA module 1 is defined as the product
of a DC bias current and a power supply voltage. If the DC bias
current is constant as in the prior art system, the HPA module 1
consumes power that is almost constant despite having low output
power. To increase the average PAE of the HPA module 1, it is important
to increase its PAE during a standby mode requiring less output
power. This implies that if the output power level is set to a low
level, the DC bias current is also set to be a low value, for example,
by setting the drain voltage Vd to increase the PAE.
As described above, according to the present invention, since the
transistor is used for a bias circuit and the transistor characteristic
caused by changes in the manufacturing process exist, the present
invention pre-records the static characteristic for each transistor
so that an optimal PAE can be achieved by adjusting the drain current
or gate voltage, or both, accordingly.
Also, the DC bias current can be precisely controlled by increasing
the capacity of the non-volatile memory 12. Moreover, although an
EEPROM is used as the non-volatile memory 12, the present invention
is not limited to the EEPROM. Any ROM can be a candidate for use
as the non-volatile memory 12 as long as it is rewritable, such
as a flash memory, a FAMOS (Floating Avalanche MOS), and a SAMOS
(Stacked-gate Avalanche MOS).
In addition, the bias control circuit 2 is implemented using a
phone DSP or a controlling CPU outside the HPA module 1 in the embodiment
of the present invention, but it can be further contemplated that
the bias control circuit 2 can be configured to be a circuit dedicated
to the exclusive purpose of bias current control and incorporated
in the HPA module 1.
As described above, an HPA module of the present invention incorporates
a non-volatile memory therein and has pre-recorded static characteristic
data of the HPA in the non-volatile memory before it is put on the
market. In operation, the data is read and the output power of the
HPA is controlled based on the individual static characteristics
of the HPA. By precisely controlling the DC bias current of the
HPA, the life span of a battery can be extended. Especially, the
present invention is highly effective in a W-CDMA mobile phone which
requires s a high efficiency (low power) power amplifying apparatus.
While the invention has been shown and described with reference
to a certain preferred embodiment thereof, it will be understood
by those skilled in the art that various changes in form and details
may be made therein without departing from the spirit and the scope
of the invention as defined by the appended claims. |