Apparatus for mobile communication system which performs signal transmission by amplitude modulation and phase modulation

A mobile communication system has a mobile phone in which a voltage is set corresponding to the characteristic variation of a PA even when a PA having characteristic variation is used. The mobile phone employs a polar loop method, which comprises an antenna (1) for transmission and reception of signal waves; an antenna switch (2) for switching the transmission mode and the reception mode; a BBLSI (3) having a function to control the transmission and reception; an RFIC (4) having a function for modulating and demodulating the transmitted and received signals; and a PA (5) for amplifying up to the target output power by means of the amplitude modulation at the time of the transmission.

CROSS-REFERENCES TO RELATED APPLICATIONS

The following applications, including this one, are being filed concurrently, and the disclosure of the other applications are incorporated by reference into this application in their entirely for all purposes:

U.K. Patent Application No. 0212737.1 (filed on May 31, 2002) entitled “APPARATUS FOR RADIO TELECOMMUNICATION SYSTEM AND METHOD OF BUILDING UP OUTPUT POWER”

U.K. Patent Application No. 0212725.6 (filed on May 31, 2002) entitled “A COMMUNICATION SEMICONDUCTOR INTEGRATED CIRCUIT, A WIRELESS COMMUNICATION APPARATUS, AND A LOOP GAIN CALIBRATION METHOD”

U.K. Patent Application No. 0212729.8 (filed on May 31, 2002) entitled “TRANSMITTER AND SEMICONDUCTOR INTEGRATED CIRCUIT FOR COMMUNICATION”

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a technique effectively applied to an apparatus for mobile communication system such as a mobile phone in which a power amplifier (hereinafter, referred to as PA) is built. More particularly, the present invention relates to a technique effectively used in an apparatus for mobile communication system capable of supplying a voltage corresponding to a characteristic variation of a PA.

BACKGROUND OF THE INVENTION

According to the examinations made by the inventors of the present invention, with respect to the apparatus for mobile communication system such as a mobile phone, the following techniques are known.

For example, in a mobile phone, a PA in which a semiconductor amplifier device such as a MOSFET or a GaAs-MESFET is used in an output section of the transmission side is built in addition to a base band LSI (hereinafter, referred to as BBLSI) as a control circuit device having a function to control the transmitting and receiving of signal and a radio frequency IC (hereinafter, referred to as RFIC) as a radio frequency circuit. The PA amplifies up to the required output voltage for communications and then outputs the output voltage.

SUMMARY OF THE INVENTION

With respect to the mobile phone as described above, in the RFIC compatible with EDGE (Enhanced Data transmitted for GMS Evolution) based on GSM (Global System for Mobile Communication) system, a technique employing a polar loop method has been proposed in which feedback is applied while isolating amplitude modulation (AM) components and phase modulation (PM) components from each other. Therefore, an AM loop including the modulation amplitude components using the PA is constructed and the linearity is required for the PA characteristic.

However, in the case where a mobile phone is constructed by the use of the conventional technique, the RFIC compatible with the EDGE employing the polar loop method causes the increase of the load on the PA characteristic. More specifically, it becomes necessary to select a PA corresponding to each RFIC when constructing various specifications of mobile phones. And in this case, there occurs a problem that no PAs can be available except the specific PAs having no characteristic variation.

In such a circumstance, while placing a particular focus on the characteristic variation of the PA, the inventors of this invention have conceived to use the compensation of the characteristic variation of the PA with an aim to be suited to the RFIC compatible with EDGE. For its achievement, while focusing on the bias voltage at the time of the amplitude modulation as a factor to determine the characteristic of the PA, the inventors have found out the method of setting the bias voltage depending on the characteristic of the PA so that the target output power can be achieved.

Considering the foregoing, an object of the present invention is to provide an apparatus for mobile communication system capable of constructing a system such as a mobile phone by setting a voltage corresponding to the characteristic variation of the PA even in a case where the PA having characteristic variation is used.

The above and other objects and novel characteristics of the present invention will be apparent from the descriptions and the accompanying drawings of this specification.

The advantages achieved by the typical ones of the inventions disclosed in this application will be briefly described as follows.

More specifically, the present invention is applied to an apparatus for mobile communication system such as a mobile phone performing data transmission of EDGE system including the amplitude modulation, wherein the apparatus for mobile communication system is provided with a BBLSI for controlling the transmitting and receiving of signal, an RFIC for modulating and demodulating the transmitting and receiving signals, and a PA for amplifying up to the target output power by means of the amplitude modulation at the time of the transmitting. Also, the present invention has characteristics as follows.

(1) Provided is a controllable voltage source (e.g., a register and a DAC (Digital to Analog Converter)), which can optionally set the bias voltage or the power supply voltage corresponding to the characteristic variation of the PA so that the target output power can be achieved at the time of amplitude modulation in the PA. Thus, an apparatus for mobile communication system can be constructed by setting the bias voltage or the power supply voltage corresponding to the characteristic variation of the PA even when the PA having characteristic variation is used.

(2) A system configuration is accomplished, in which the connection between the PA and the BBLSI or the RFIC for setting the bias voltage or the power supply voltage is made by means of one pin. Thus, the connection between the PA and the BBLSI or the RFIC by means of the one pin makes it possible to supply the bias voltage or the power supply voltage.

(3) A system configuration is accomplished, in which the DAC is built in the PA, the BBLSI, or the RFIC. In this configuration, the DAC and the RFIC or the BBLSI are connected to each other by the use of the one analog pin when the DAC is built in the RFIC or the BBLSI. Alternatively, the DAC and PA are connected to each other by the use of the one pin (BBLSI) for serial interface using digital signal when the DAC is built in the PA. Thus, when installing the DAC in the RFIC, the BBLSI, or the PA, the connection therebetween can be made by the use of one pin terminal and one line to supply the bias voltage or the power supply voltage.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. Note that components having the same function are denoted by the same reference symbol throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

Although not particularly limited, the apparatus for mobile communication system to which the present invention is applied is applied to a mobile phone having a PA built therein, and an example of the mobile phone will be described below.

An example of a configuration of a mobile phone in an embodiment of the present invention will be described based onFIG. 1.FIG. 1shows a schematic configuration of a mobile phone in this embodiment.

The mobile phone mentioned in this embodiment is one employing the polar loop, which comprises an antenna1for the transmitting and receiving of signal waves, an antenna switch2for switching the transmission mode and the reception mode, a BBLSI3having a function to control the transmission and reception, an RFIC4having a function for modulating and demodulating the transmitted and received signals, and a PA5for amplifying up to the target output power by means of the amplitude modulation at the time of the transmission.

The BBLSI3is a control circuit device that is bidirectionally connected to the RFIC4and is constituted of a DSP (Digital Signal Processor), a microprocessor, a semiconductor memory, and the like. The BBLSI3has functions to convert an audio signal to a base band signal at the time of transmitting, to convert a received signal to an audio signal at the time of receiving, and also to generate signals for switching modulation methods and those for switching a band at the time of the transmitting and receiving.

The RFIC4is a radio frequency circuit constituted of, for example, a PLL synthesizer having a VCO, a modulator, a demodulator, a divider, a mixer, a switch, and the like, and the RFIC4is connected to the antenna switch2connecting to the antenna1, the BBLSI3, and to the PA5. The RFIC4has functions to generate oscillation signals having multiple frequency bands, to modulate the transmitted signals at the time of transmitting, to demodulate the received signal at the time of receiving, and to switch the modes of GSM, DCS (Digital Cellular System), and PCS (Personal Communication System).

The PA5is a power amplifier connected to the antenna switch2connecting to the antenna1and to the RFIC4. The PA5has functions to amplify up to the output power required for communications and to output the voltage thus obtained.

In the mobile phone having the above-mentioned configuration, since the polar loop is employed, a loop is formed in which feedback is applied while isolating amplitude modulation components and phase modulation components from each other. Particularly, the amplitude loop includes the amplitude modulation components using the PA5and has a path starting from the RFIC4and returning back to the RFIC4through the PA5, wherein the bias voltage of the PA5is supplied from the RFIC4, and whereby the PA5can be used efficiently.

Note thatFIG. 1shows an example where a BIASDAC6for supplying a bias voltage of the PA5is built in the RFIC4. However, it is also possible to install the BIASDAC6in the PA5or in the BBLSI3. Details thereof will be described later.

Descriptions will be made for an example of the connection between the PA and the BIASDAC and the configuration of the same referring toFIGS. 2 to 4.FIG. 2schematically shows a configuration of the PA and the BIASDAC,FIG. 3schematically shows a circuit of the PA, andFIG. 4schematically shows a configuration of the BIASDAC, respectively.

As shown inFIG. 2, the PA5is constituted of an AM controller11, an amplifier12, a capacitor C1, and the like. Although not particularly limited, the PA5is constituted as a module in which the AM controller11and the amplifier12are formed on a semiconductor chip as an integrated circuit and the integrated circuit and the element such as the capacitor C1are mounted on a common ceramic substrate. In this PA5, a signal PAin of the phase modulation component is inputted, and a signal Vramp of the amplitude modulation component is inputted to the AM controller11, these signals are amplified by the amplifier12in a state where a bias voltage Vbias is applied, and then outputted as a signal Vrfout obtained by adding the amplitude component to the phase component.

More specifically, the PA5is constituted of, for example, the capacitor C1, transistors T1and T2, resistors R1and R2, and the like as shown in an example inFIG. 3. The gate terminal, the drain terminal, and the source terminal of the transistor T1are connected to the PAin terminal via the capacitor C1, the Vrfout terminal, and the ground potential, respectively. Further, the gate terminal of the transistor T1is connected to the Vbias terminal via the resistor R1. The gate terminal, the drain terminal, and the source terminal of the transistor T2are connected to the Vramp terminal, the Vcc potential, and the Vrfout terminal via the transistor R2, respectively.

The BIASDAC6is constituted of a register21, DAC22, and the like. The DAC22is provided with a current source23, a parallel circuit of resistors24and switches25, an amplifier26, and the like. In the BIASDAC6, data corresponding to a bias voltage Vbias that can be applied to the characteristic variation of the PA5is stored in the register21and the switches25are turned on and off based on the data in the register21so that resistance of the resistors24in the parallel circuit matches with the characteristic of the PA5. Then, the bias voltage Vbias that matches with the characteristic of the PA5is outputted from the DAC22via the amplifier26.

More specifically, in the BIASDAC6having a configuration including the register21and the DAC22as shown in an example inFIG. 4, data DATA from the outer BBLSI3is taken in the register21synchronously with a clock signal CLK by means of the activation (start) of a load enable signal LE, and then the data DATA is held therein. Thereafter, the data held in the register21is transmitted to the DAC22by the parallel transmission, and is converted in the DAC22from the digital signal into the analog signal, and then outputted as the bias voltage Vbias. The bias voltage Vbias is supplied from the BIASDAC6to the PA5by one pin terminal based on an analog system.

In the connection between the PA5and the BIASDAC6having the structure as described above, the signal PAin of the phase modulation component is inputted and the signal Vramp of the amplitude modulation component is also inputted to the PA5. Then, the inputted signals are amplified by the amplifier12and the signal Vrfout obtained by adding the amplitude component to the amplified phase component is outputted from the PA5.

At this time, in the BIASDAC6, the switches25are turned on and off based on the data in the register21so that resistance of the resistors24in the parallel circuit matches with the characteristic of the PA5, and the bias voltage Vbias that matches with the characteristic of the PA5is set. Then, the bias voltage Vbias that matches with the characteristic of the PA5is supplied from the BIASDAC6, and whereby it becomes possible to maximize the performance of the PA5.

Descriptions will be made for an example of the characteristic of the PA referring toFIGS. 5 and 6.FIG. 5shows a case where linearity can not be obtained in a range where linearity is required andFIG. 6shows a case where accuracy can not be obtained in a range where linearity is required, respectively. Each of the horizontal axes represents the signal Vramp [V] of the amplitude modulation component and each of the vertical axes represents the signal Vrfout [dBm] obtained by adding the amplitude component to the amplified phase component.

On constituting the polar loop in the PA5, it is desirable to have linearity and infinite bandwidth so as not to be distorted relative to the amplitude signals. In actual cases, however, a certain gain and linearity are shown at the time of high power level (Vramp=large) but the linearity can not be obtained and gain of the PA5is changed at the time of low power level (Vramp=small).

In an example of the characteristic shown inFIG. 5, the linear part of the PA5changes depending on the value of the bias voltage Vbias applied from the BIASDAC6. When the bias voltage Vbias is set to Vbias1, it is impossible to maintain the linearity in a range where the linearity is required. Therefore, the bias voltage Vbias is set to Vbias2in order to give the linearity in a range where the linearity is required.

In an example of the characteristic shown inFIG. 6, the linearity is maintained in both cases where the bias voltage Vbias is set to Vbias3and Vbias4. However, when the bias voltage Vbias is set to the Vbias4, the use range of the signal Vramp of the amplitude modulation component relative to the required maximum output becomes small. Therefore, it is impossible to perform the accurate control by the signal Vramp. Thus, the bias voltage Vbias is set to the Vbias3so that the variable range by the signal Vramp can be maximized in the range where the linearity is required.

As described above, the linearity is maintained in the range where the linearity is required and the bias voltage Vbias is set so that the variable range by the signal Vramp can be maximized in a range where the linearity is required. By so doing, it becomes possible to use the PA5efficiently. Note that, when the PA5is built in a mobile phone, the optimum value of the bias voltage Vbias corresponding to the respective characteristics is obtained and stored in the BBLSI3. Then, the value of the bias voltage Vbias is written in the register21of the BIASDAC6in the RFIC4from the BBLSI3at the time of the switch-on of the mobile phone. Thus, the bias voltage corresponding to the PA5can be supplied.

Another configuration of a mobile phone will be described based onFIGS. 7 and 8.FIG. 7shows a case where the BIASDAC is built in the BBLSI, andFIG. 8shows a case where the BIASDAC is built in the PA, respectively, each of which has a system configuration in which the bias voltage can be set by the one pin.

In a configuration example of a mobile phone shown inFIG. 7, the BIASDAC6is built in a BBLSI3aand the bias voltage is supplied to the PA5by the one analog pin. More specifically, the mobile phone is constituted of the BBLSI3ahaving the BIASDAC6built therein, a RFIC4a, the PA5, and the like and the bias voltage can be supplied from the BIASDAC6built in the BBLSI3ato the PA5by one pin based on an analog system.

In a configuration example of a mobile phone shown inFIG. 8, the BIASDAC6is built in a PA5band the bias voltage is supplied to the PA5bby the one pin for digital serial transmission. More specifically, the mobile phone is constituted of the BBLSI3, an RFIC4b, the PA5bhaving the BIASDAC6built therein, and the like and the signal for setting the bias voltage can be supplied from the BBLSI3to the PA5by one pin by the digital serial transmission.

Therefore, according to the mobile phone in this embodiment, advantages as described below can be obtained.

(1) In a mobile phone performing the data transmission of EDGE system including the amplitude modulation, even when the PA5having characteristic variation is used, since the register21and the DAC22capable of optionally setting the bias voltage are used, it is possible to set the bias voltage so as to correspond to the characteristic variation of the PA5and to construct a system.

(2) Since the PA5and the BBLSI3or the RFIC4are connected to each other by using one pin, it is possible to supply the bias voltage to the PA5by using only one pin.

(3) In a system configuration in which the BIASDAC6is built in the PA5or the BBLSI3, the BIASDAC6and the RFIC4or the BBLSI3are connected to each other by the use of one analog pin when the BIASDAC6is built in the RFIC4or in the BBLSI3, or the BIASDAC6and the PA5are connected to each other by the use of one pin for digital serial transmission when the BIASDAC6is built in the Pa5. Therefore, the connection therebetween can be made by the use of one pin terminal and one line to supply the bias voltage.

(4) Since even the PA5having the characteristic variation can be used to construct a system, it becomes possible to satisfy various specifications. As a result, mobile phones of various specifications can be constructed.

In the foregoing, the inventions made by the inventors thereof have been described in detail based on the embodiments. However, it goes without saying that the present is not limited to the embodiments and various modifications can be made therein without departing from the scope of the present invention.

For example, in the foregoing embodiments, the case where the bias voltage corresponding to the characteristic variation of the PA is set has been described. However, the present invention is not limited to this. More specifically, it is also possible to set a power supply voltage of the PA so as to correspond to the characteristic variation of the PA. Also in this case, similar to the case of the bias voltage, the configuration in which power supply voltage is set by the controllable voltage source composed of a register and the DAC can be employed.

Also, in the forgoing embodiments, descriptions have been made with using a mobile phone as an example. However, the present invention can also be effectively applied to, for example, an IC used for mobile phone compatible with the EDGE, and further applied to various types of apparatus for mobile communication systems.