Mobile telephone system

Details Mobile telephone system Mobile telephone system

2000-10-26

2002-04-02

Waung, Nay (Department: 2681)

Telecommunications

Transmitter and receiver at same station

Radiotelephone equipment detail

C455S188100, C455S552100, C330S051000, C333S104000, C333S105000

Reexamination Certificate

active

06366788

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a multi-band system mobile telephone apparatus that can transmit and receive a plurality of band-frequencies and particularly to the technique that can effectively be applied to a mobile telephone apparatus including a transmitting unit for transmitting the radio signal of the dual-band system by amplifying the same signal.
BACKGROUND ART
In the European digital cellular system that is now put into the service as the mobile communication system, it is assumed in the GSM (Global System for Mobile Communication) using the frequency of 0.9 GHz band that subscribers will exceed the system capacity in near future. Therefore, the mobile telephone apparatus (hand-held telephone) corresponding to the dual-band system using, in combination with the GSM system, the DCS (Digital Cellular System) 1800 system using the frequency band near 1.8 GHz is requested because this system is similar to the GSM communication system in such a point that the same modulation system GMSK (Gaussian-filtered Minimum Shift Keying) is introduced.
Here, since above two systems (GSM system and DCS1800 system) are almost used in common except for the frequency, it is possible to constitute the hand-held telephone set that is used in common in the GSM/DSC1800 systems by providing only the high frequency unit such as the power amplifier module that can be used for dual band system.
Therefore, in order to achieve the power amplifier module corresponding to the dual-band system, two power amplifier module systems corresponding to each communication system are integrated within the module and are structured to selectively switch each system as required.
FIG. 8
illustrates a schematic structure of the hand-held telephone discussed prior to the present invention. In the same figure, the reference numeral
6
designates a system control unit (CNTU);
10
, a blanching filter;
9
, a transmitting/receiving antenna corresponding to the dual-band;
1
, a first high frequency power amplifier module (RF power module);
2
, a second RF power module;
32
, a wide-band amplifier (WAMP);
4
, a radio frequency signal processing unit (RFSPU);
7
, an operation panel (OP);
8
, a transceiver consisting of a speaker (SP) and a microphone (MIC). Moreover, the communication systems that can be used through the switching operation include the GSM system and DSC1800 system.
A radio signal processing circuit
4
is comprised of a modem processing unit, transmitting/receiving IF (intermediate frequency) unit and frequency converting unit (up-/down-converter) or the like and a radio signal (f
1
or f
2
) of any one of the GSM system of 0.9 GHz band or the DSC1800 system of 1.8 GHz band selected is generated and output at the transmitting time. These two kinds of radio transmitting signals f
1
, f
2
are input respectively to the first RF power module
1
and the second RF power module
2
.
The RF power module
1
is a power amplifier module corresponding to the GSM communication system and is comprised of an RF power MOSFET (T
1
) for final stage amplifier, matching circuits MC
1
and MC
2
consisting of passive elements and inductance element Lc
1
for DC choke of drain bias. In this case, the transistor T
1
is formed to provide an output, through the switching of a gate voltage to cutoff bias level and predetermined bias level for realizing high efficiency, with the first bias control signal
13
output from the system control unit
6
interlocked with the GSM/DSC1800 selection switch of the hand-held telephone body.
In the same manner, the RF power module
2
is the power amplifier module corresponding to the DSC1800 communication system and is comprised of the RF power MOSFET (T
2
) for final stage amplifier, matching circuits MC
3
and MC
4
consisting of passive elements and inductance element Lc
2
for DC choke of drain bias. In this case, the transistor T
2
is formed to provide an output, through the switching of gate voltage to the cutoff bias level and the predetermined bias level to realize high efficiency, with the second bias control signal
14
output from the system control unit
6
interlocked with the GSM/DSC1800 selection switch of the hand-held telephone body.
The RF power module
1
and RF power module
2
are respectively designed to set the matching with the matching circuits MC
1
to MC
4
so that the radio signals of the respective communication systems can be amplified effectively.
Thereby, the apparatus is operated as a hand-held telephone set of the GSM system, the bias control signal
13
of the RF power module
1
is set to the predetermined bias level and meanwhile the bias control signal
14
of the RF power module
2
is set to the cutoff bias level. Thereby, it is possible to selectively operate only the RF power module
1
to amplify the GSM radio signal f
1
(0.9 GHz band).
When the apparatus is operated as a hand-held telephone set of the DSC1800 system, the bias control signal
14
of the RF power module
2
is set to the predetermined bias level and meanwhile the bias control signal
13
of the RF power module
1
is set to the cutoff bias level and thereby only the RF power module
2
is selectively operated to amplify the DSC1800 radio signal f
2
(1.8 GHz band).
The structure explained above is selectively used depending on the setting of communication system by respectively providing the exclusive RF power modules within the apparatus for two communication systems. The RF power modules provided within the apparatus are designed in the optimum manner for respective communication system, assuring economical and effective operation.
Moreover, the RF power module used in the hand-held telephone set satisfies the specifications of the high frequency characteristic determined by each system such as the output power or the like and is also required to satisfy further high efficiency and reduction in size and therefore this RF power module should attain both small size and high efficiency.
Here, the technique to control the harmonics is well known as the technique to realize further high efficiency operation of the power amplifier for transmitter. For example, the Japanese Published Unexamined Patent Application No. SHO 60 (1985)-109310 discloses the structure that one end part of the ¼ wavelength transmission line is terminated at a higher frequency, while the other end thereof is connected to an amplifier element and a series resonant circuit to obtain the desired basic waveform signal output from the serial resonant circuit. With this structure, the connecting point of the output side of the amplifying element and ¼ wavelength transmission line is terminated for the basic waveform and odd number order harmonics and thereby the ideal class F operation mode in which a current and a voltage at the output terminal of the amplifying element become zero can be obtained, and high efficiency can also be attained.
The high frequency power amplifier circuit of the related art forms a power amplifier circuit, as illustrated in FIG.
9
(
a
), by connecting the other end of a ¼ wavelength transmission line
34
with one end thereof is terminated for high frequency signal to the output side of an amplifying element
33
and one end of the series resonance circuit
35
and the other end of the series resonance circuit
35
to an output terminal
36
. Here, when the amplifying element
33
operates upon input of a basic signal, the voltages are distributed on the ¼ wavelength transmission line
34
. FIG.
9
(
b
) illustrates the condition of voltage distribution on the ¼ wavelength transmission line
34
. This voltage distribution can be obtained for signal inputs of basic signal and double-frequency signal. In this figure, I indicates the connection part of the ¼ wavelength transmission line
34
terminated to the output terminal of the amplifying element
33
, while II indicates the high frequency termination part of the ¼ wavelength transmission line
34
. Sine one end II of the ¼ wavelength transmission lin

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