Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Reexamination Certificate
2000-12-01
2001-08-28
Chang, Vivian (Department: 2682)
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
C455S574000, C455S573000, C455S126000
Reexamination Certificate
active
06282411
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery-powered mobile communication terminal device.
2. Description of the Related Art
In recent mobile communication terminal devices such as cellular phones, battery voltages employed have been lowered as the operational voltages of the internal circuits have been decreased. On the other hand, lithium ion batteries have become widely used because they have an advantage in battery capacity and weight.
FIG. 16
is a block diagram showing the configuration of a transmitting section of a conventional mobile communication terminal device;
FIG. 17
is an explanatory diagram illustrating a relationship between an input signal and its modulation frequencies;
FIG. 18
is an explanatory diagram illustrating the output phase of a baseband signal output from a baseband modulator;
FIG. 19
is an explanatory diagram illustrating phase errors included in a carrier wave;
FIG. 20
is an explanatory diagram illustrating the output phase of a transmission signal output from a quadrature modulator; and
FIG. 21
is a diagram showing a relationship between transmission power control levels and their transmission outputs in a digital portable phone using the GSM system.
Referring to
FIG. 16
, reference numeral
8
denotes a microphone;
9
denotes a control section;
10
denotes a baseband modulator;
11
denotes a modulation phase generating section;
12
denotes a phase adder;
13
denotes a phase converter; and
14
denotes a D/A converter. The baseband modulator
10
is composed of the modulation phase generating section
11
, the phase adder
12
, the phase converter
13
, and the D/A converter
14
. Reference numeral
15
denotes a quadrature modulator for modulating a carrier wave according to a baseband signal and outputting a transmission signal;
16
denotes a transmission local oscillator for receiving a battery voltage supply and generating a carrier wave;
17
denotes a battery for supplying a voltage to each circuit;
18
denotes a voltage regulator for regulating the battery voltage output from the battery
17
to a constant voltage, and outputting it to the transmission local oscillator
16
;
19
denotes a transmission power amplifier for amplifying the transmission signal to a predetermined transmission output level;
20
denotes a transmission ON/OFF control section for controlling the ON/OFF states of the transmission power amplifier
19
; and
21
denotes an antenna for transmitting the transmission signal amplified by the transmission power amplifier
19
.
Two power supply routes are used for driving the mobile communication terminal device shown in FIG.
16
. One route directly supplies power from the battery
17
to the transmission power amplifier
19
, while the other supplies a regulated, substantially constant voltage to the transmission local oscillator
16
through the voltage regulator
18
. To efficiently drive a circuit consuming a particularly large power, such as the transmission power amplifier
19
, it is necessary to directly connect the circuit to the battery
17
for power supply. On the other hand, power is supplied through the voltage regulator
18
to circuits such as the transmission local oscillator
16
which do not require large amounts of power but require a stable power supply.
The transmission local oscillator
16
generates a radio frequency wave having a predetermined frequency used as a carrier wave, and the phase and frequency of the carrier wave generated by the transmission local oscillator
16
are modulated by the quadrature modulator
15
according to a baseband signal. Therefore, it is especially important to supply a stable voltage to the transmission local oscillator
16
, which generates a carrier wave, in order to ensure communication quality.
Next, description will be made of the operation of the transmission section of the mobile communication terminal device. An analog voice signal entered from the microphone
8
is converted into a digital voice signal (1/0 signal) in the control section
9
. Then, the digital voice signal subjected to a voice coding process is arranged in the TDMA (Time Division Multiple Access) transmission format, and output to the modulation phase generating section
11
of the baseband modulator
10
.
FIG. 17
shows frequencies of the digital voice signal (1/0 signal) after it is passed through a Gaussian filter. Each frequency is equivalent to a variation in phase per unit time, or a microphase, indicated by a hatched portion in FIG.
17
.
The modulation phase generating section
11
generates a microphase according to input transmission data, and outputs it to the phase adder
12
. Microphases output from the modulation phase generating section
11
are integrated (added by the phase adder
12
) into the phase information shown in FIG.
18
. The phase converter
13
converts the phase information output from the phase adder
12
into inphase components I and quadrature components Q, namely an I digital modulation signal and a Q digital modulation signal, and outputs them to the D/A converter
14
. The D/A converter
14
, in turn, converts the I and Q digital modulation signals output from the phase converter
13
into I and Q analog modulation signals, and then outputs them to the quadrature modulator
15
as baseband signals.
The transmission local oscillator
16
receives a battery voltage supply output from the voltage regulator
18
to generate carrier waves, and outputs the generated carrier waves to the quadrature modulator
15
. The quadrature modulator
15
modulates the carrier waves according to the I and Q analog modulation signals. Specifically, the two carrier waves which are 90 degrees out of phase with each other (local oscillation signals generated in the transmission local oscillator
16
) are each multiplied by one of the I and Q analog modulation signals, and combined to produce and output a transmission signal to the transmission power amplifier
19
.
Since a mobile communication terminal device using the TDMA method makes transmission during only assigned time periods (time slots), the transmission power amplifier
19
is controlled so that it is turned ON only during such time-slot transmissions, and turned OFF otherwise. Such ON/OFF control is performed by the transmission ON/OFF control section
20
. The transmission signal amplified to a predetermined transmission output level by the transmission power amplifier
19
is output from the antenna
21
as a transmission wave. The transmission output of the transmission power amplifier
19
is controlled according to transmission power control levels, shown in
FIG. 21
, employed in digital portable phones using the GSM system.
Incidentally, since the battery
17
, which supplies power to the mobile communication terminal device, has a limited power supply capacity, the battery voltage supplied to the circuits momentarily (for about a few tens of A&mgr; seconds) drops when a large amount of power consumption occurs. Specifically, when the transmission ON/OFF control section
20
turns ON the transmission power amplifier
19
at the time of starting a transmission for a time slot, power consumption occurs to amplify the transmission signal, momentarily lowering the output voltage of the battery
17
.
When the battery voltage output from the battery
17
is lowered due to the initiation of operation of the transmission power amplifier
19
, the regulator output voltage from the voltage regulator
18
, which regulates the battery voltage to a substantially constant voltage, also momentarily drops. Since the transmission local oscillator
16
receives a voltage supply from the voltage regulator
18
, a drop in the regulator output voltage disturbs the oscillation frequency of the transmission local oscillator
16
, producing a phase error in a generated carrier wave as shown in FIG.
19
. When a carrier wave including such a phase error is output to the quadrature modulator
15
, and modulated according to a baseband signal, the transmission si
Chang Vivian
Lee John J.
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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