Abstract:
For use in an amplifier configuration including a high-power amplifier and a low-power amplifier which are always interconnected in terms of high frequencies and between which switching is made using no switches, a highly stable high-frequency power amplifier module with high isolation between the amplifiers is provided. To reduce wrapping around from a low-power amplifier section in an activated state to a high-power amplifier section in a deactivated state or from the high-power amplifier section in an activated state to the low-power amplifier section in a deactivated state, an input matching circuit having high isolation characteristics is included in an input matching circuit portion which does not have much to do with amplifier efficiency. Switching of each of the amplifier sections between an activated state and a deactivated state is effected by control using bias input terminals.

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese application JP 2004-272945 filed on Sep. 21, 2004, the content of which is hereby incorporated by reference into application. 
     FIELD OF THE INVENTION 
     The present invention relates to a high-frequency power amplifier for use in a transmitter section of radio communication equipment such as mobile telephones. More particularly, it relates to a high-frequency power amplifier module in which switching between a high-power amplifier and a low-power amplifier can be made by bias control. 
     BACKGROUND OF THE INVENTION 
     In recent years, in the field of mobile communications, not only mobile terminals but also base stations are required to be made smaller and lighter. In this respect, since the power amplifier sections of relevant equipment greatly affect the sizes and weights of the equipment, it is important to improve efficiency of the power amplifier sections. Mobile terminals, in particular, are normally powered by batteries, so that the length of time during which they are continuously operable is limited. In the circuit of a mobile terminal, its power amplifier section consumes the most power. Reducing the power consumption of the power amplifier section (that is, making the power amplifier section more efficient) is therefore a major task to be solved to make the mobile terminal continuously operable for an extended period of time. For a base station, too, to allow its equipment to be installed close to an antenna so as to reduce cable loss, making its high-frequency power amplifier section smaller and lighter is required. Hence, improving efficiency of the high-frequency power amplifier section is essential. 
     Generally, the efficiency of a high-frequency power amplifier using a semiconductor device increases with its output level, achieving maximum efficiency around where the output is saturated. The maximum output (saturation power) level obtainable from a high-frequency power amplifier depends on the size of a semiconductor device used in it. If, to improve the efficiency in a low output power range of a high-frequency power amplifier, the semiconductor device included in the high-frequency power amplifier is made smaller, causing its output saturation level to be lowered, the high-frequency power amplifier will become unable to provide a high output power when required. If a high-frequency power amplifier is arranged to render high efficiency in a high output power range, its efficiency will remarkably deteriorate in a low output power range. Thus, it is extremely difficult to make a high-frequency power amplifier highly efficient both in a high output power range and in a low output power range. 
     A known arrangement for achieving highly efficient operation both in a high output power range and in a low output power range includes plural output stage amplifiers and switches. In the arrangement, the switches are used to selectively use the amplifiers according to the required output level (see the patent document 1, for example). 
     In another known arrangement intended to further improve efficiency, switching between plural output stage amplifiers is effected using no switches (see the patent document 2, for example). 
     [Patent Document 1] JP-A No. 07-336168 
     [Patent Document 2] JP-A No. 2003-046340 
     SUMMARY OF THE INVENTION 
     In the known arrangement in which switches are used to selectively use plural output stage amplifiers, the switches contribute to lowering the efficiency of operation, but isolation between the output stage amplifiers connected in parallel is enhanced. In the another known arrangement in which output stage amplifiers are selectively used using no switches, lowering of the operational efficiency due to switches does not take place, but, with high-power amplifiers and low-power amplifiers always interconnected in terms of high frequencies, isolation between the amplifiers is low and the amplifiers are less stable. 
     An object of the present invention is to provide a highly stable high-frequency power amplifier module with high isolation between output amplifiers. 
     Of the inventions disclosed in the present specification, the representative invention can be described as follows. A high-frequency power amplifier module according to the present invention includes a first amplifier section which power amplifies a high-frequency signal, a second amplifier section which power amplifies a high-frequency signal, an input matching circuit which makes input matching between the first amplifier section and the second amplifier section, and an output matching circuit which makes output matching between the first amplifier section and the second amplifier section, wherein operations of the first and the second amplifier sections are switched by control using a bias voltage or a bias current and wherein the input matching circuit has a high isolation characteristic between the first and the second amplifier sections. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to the present invention. 
         FIG. 2  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a second embodiment of the present invention. 
         FIG. 3  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a third embodiment of the present invention. 
         FIG. 4  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a fourth embodiment of the present invention. 
         FIG. 5  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a fifth embodiment of the present invention. 
         FIG. 6  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a sixth embodiment of the present invention. 
         FIG. 7  is a chart showing input-output characteristics and efficiency characteristics of amplifier sections according to the present invention. 
         FIG. 8  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a seventh embodiment of the present invention. 
         FIG. 9  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to an eighth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of a high-frequency power amplifier module according to the present invention will be described in detail with reference to the accompanying drawings. In the following description of the embodiments, the same components are denoted by the same reference numerals or symbols and their detailed explanations are not repeated. 
     Embodiment 1 
       FIG. 1  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to the present invention. A high-frequency power is input to a high-frequency input (RFin) terminal  101  and is transmitted, via a high-isolation, input matching circuit (HISO_MTin)  107 , to a high-power amplifier section (HP_AMP)  109  or a low-power amplifier section (LP_AMP)  110  to be amplified there. The amplified high-frequency power is then output, after passing an output matching circuit (MTout)  108 , from a high-frequency output (RFout) terminal  102 . The high-isolation input matching circuit may be, for example, a Wilkinson divider. 
     Activating the low-power amplifier section  110  and deactivating the high-power amplifier section  109  of the high-frequency power amplifier module is possible by turning off either or both of a bias input terminal (Cont 1 )  103  and a bias output terminal (Bias 1 )  105  of the high-power amplifier section  109  and turning on both of a bias input terminal (Cont 2 )  104  and a bias output terminal (Bias 2 )  106  of the low-power amplifier section  110 . 
     Activating the high-power amplifier section  109  and deactivating the low-power amplifier section  110  of the high-frequency power amplifier module is possible, in a manner similar to the above-described, by turning off either or both of the input side bias terminal  104  and the output side bias terminal  106  of the low-power amplifier section  110  and turning on both of the input side bias terminal  103  and the output side bias terminal  105  of the high-power amplifier section  109 . 
     Providing a high-isolation input matching circuit as in the present embodiment can prevent, using no switches, a signal from wrapping around from an activated amplifier section to a deactivated amplifier section, so that a highly stable and efficient high-frequency power amplifier module can be realized. 
       FIG. 7  shows input-output characteristics and efficiency characteristics of the low-power amplifier section and the high-power amplifier section. In  FIG. 7 , the horizontal axis represents an input power Pin, and the vertical axis represents an output power Pout and an efficiency η. Characteristic curves a and b represent an input-output characteristic and an efficiency characteristic, respectively, of the low-power amplifier section  110 . Characteristic curves c and d represent an input-output characteristic and an efficiency characteristic, respectively, of the high-power amplifier section  109 . 
     According to the level of an input power, switching between the high-power amplifier and the low-power amplifier is made through bias control for the two amplifiers, so that it is possible to use, when the input power level is low, the low-power amplifier section  110  whose efficiency characteristic b in a low power range is much better than the efficiency characteristic d of the high-power amplifier section  109  as shown in  FIG. 7 . 
     Embodiment 2 
       FIG. 2  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a second embodiment of the present invention. The configuration is the same as the configuration shown in  FIG. 1  with the high-isolation input matching circuit  107  replaced by a distributed constant Wilkinson circuit. 
     In this embodiment, distributed constant lines (MSLs)  212  and  213  and a resistance  214  make up the distributed constant Wilkinson circuit. In this case, it is not necessarily required that either or both of the line impedance and the electrical length are the same between the distributed constant lines  212  and  213 . In other words, impedances and/or distributions at Wilkinson divider terminals may be different for the low-power amplifier section  110  and the high-power amplifier section  109 . 
     This is because the amplification gain or the input impedance is not necessarily the same between the high-power amplifier section  109  and the low-power amplifier section  110 . Unlike in a case where impedances and/or distributions are the same for the high-power and the low-power amplifier sections, in a case where they are different for the high-power and the low-power amplifier sections, a configuration incorporating an arrangement for matching the input impedances of the high-power amplifier section  109  and the low-power amplifier section  110  can be used. The latter case also has an advantage that the difference in gain between the two amplifier sections can be made up for. Generally, a permissible range of difference between distributions for two amplifier sections is, though being dependent on the system in use, generally in the range of 0&lt;ΔG≦10 dB, or so. 
     When a distributed constant Wilkinson circuit is used, high isolation is maintained for not only fundamental-wave frequencies but also odd-numbered harmonics. A high-frequency power is input to the high-frequency input terminal  101  and is transmitted, via a distributed constant Wilkinson circuit, to the high-power amplifier section  109  or the low-power amplifier section  110 . The subsequent operation is the same as in the configuration shown in  FIG. 1 . According to the configuration of this embodiment as with the configuration shown in  FIG. 1 , when the input power level is low, an efficiency characteristic much better than obtainable using the high-power amplifier section  109  can be obtained using the low-power amplifier section  110 . 
     Embodiment 3 
       FIG. 3  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a third embodiment of the present invention. The configuration is the same as the configuration shown in  FIG. 1  with the high-isolation input matching circuit  107  replaced by a lumped constant Wilkinson circuit. In this embodiment, inductances  311   a  and  311   b , a capacitance  313 , and a resistance  314  make up the lumped constant Wilkinson circuit. In this case, the inductances  311   a  and  311   b  need not necessarily be of a same value. A high-frequency power is input to the high-frequency input terminal  101  and is transmitted, via the lumped constant Wilkinson circuit, to the high-power amplifier section  109  or the low-power amplifier section  110 . The subsequent operation is the same as in the configuration shown in  FIG. 1 . The effects of this embodiment are also similar to those obtained from the configuration shown in  FIG. 1 . 
     Embodiment 4 
       FIG. 4  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a fourth embodiment of the present invention. The configuration is the same as the configuration shown in  FIG. 1  with the high-isolation input matching circuit  107  replaced by a lumped constant Wilkinson circuit. In this embodiment, an inductance  411 , capacitances  412  and  413 , and a resistance  414  make up the lumped constant Wilkinson circuit. In this case, the capacitances  412  and  413  need not necessarily be of a same value. A high-frequency power is input to the high-frequency input terminal  101  and is transmitted, via the lumped constant Wilkinson circuit, to the high-power amplifier section  109  or the low-power amplifier section  110 . The subsequent operation is the same as in the configuration shown in  FIG. 1 . The effects of this embodiment are also similar to those obtained from the configuration shown in  FIG. 1 . 
     Embodiment 5 
       FIG. 5  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a fifth embodiment of the present invention. The configuration is the same as the configuration shown in  FIG. 4  with the lumped constant Wilkinson circuit made up of an inductance  411 , capacitances  412 ,  413 , and  515 , and a resistance  514 . The configuration of this embodiment has an advantage that, between the high-power amplifier section  109  and the low-power amplifier section  110 , high isolation can also be maintained for direct currents and low frequencies dependent on the capacitance  515 . 
     Embodiment 6 
       FIG. 6  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a sixth embodiment of the present invention. The configuration is the same as the configuration shown in  FIG. 1  with the high-power amplifier section  109  and the low-power amplifier section  110  each including a bipolar transistor. In the high-power amplifier section  109 , the input side bias terminal  103  is connected, via a resistance R 1 , to the base of an emitter-grounded large-output transistor Q 1  and the output side bias terminal  105  is connected, via an inductance  611 , to the collector of the transistor Q 1 . Similarly, in the low-power amplifier section  110 , the input side bias terminal  104  is connected, via a resistance R 2 , to the base of an emitter-grounded large-output transistor Q 2  and the output side bias terminal  106  is connected, via an inductance  612 , to the collector of the transistor Q 2 . 
     The bases of the transistors Q 1  and Q 2  are connected to an output of the high-isolation input matching circuit  107  via capacitors C 1  and C 2 , respectively. The transistor Q 1  included in the high-power amplifier section  109  has a device size equal to or larger than that of the transistor Q 2  included in the low-power amplifier section  110 . 
     Embodiment 7 
       FIG. 8  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to a seventh embodiment of the present invention. The configuration is made up of an example module board  801  carrying a circuit pattern corresponding to the equivalent circuit shown in  FIG. 3 . Shaded areas of  FIG. 8  represent wiring conductors on the module board. Also in  FIG. 8 , each “cap” represents a chip capacitor, each “ind” a chip inductor, a “res” a chip resistor, and each reference number  806  denotes a bonding wire. The components thus represented in  FIG. 8  make up a lumped constant Wilkinson circuit  805 . Note that  FIG. 8  shows principal parts only. Such parts as an output matching circuit, output terminals, and bonding wires for output are not shown in  FIG. 8 . Such parts are also omitted in  FIG. 9 . The lumped constant Wilkinson circuit  805  can be configured for the circuits shown in  FIG. 4  and  FIG. 5 , too. 
     A high-frequency power is input to a high-frequency input terminal  807  and is transmitted, via the lumped constant Wilkinson circuit  805 , to the high-power amplifier section  109  or the low-power amplifier section  110  provided on a semiconductor chip  802 . The subsequent operation is the same as in the configuration shown in  FIG. 1 . 
     Embodiment 8 
       FIG. 9  is a circuit block diagram showing a configuration of a high-frequency power amplifier module according to an eighth embodiment of the present invention. The configuration is the same as the configuration shown in  FIG. 8  with the lumped constant Wilkinson circuit  805  integrated on a semiconductor chip  902 . 
     Use of an integrated high-isolation input matching circuit incorporating a lumped constant Wilkinson circuit realizes a smaller configuration than that shown in  FIG. 8 . The semiconductor chip  902  is mounted on the module board  801 . The lumped constant Wilkinson circuit  905  can also be applied to the circuits shown in  FIG. 4  and  FIG. 5 . A high-frequency power is input to a high-frequency input terminal  907  and is transmitted, via the lumped constant Wilkinson circuit  905 , to the high-power amplifier section  109  or the low-power amplifier section  110  provided on the semiconductor chip  902 . The subsequent operation is the same as in the configuration shown in  FIG. 1 . 
     The present invention has been described in connection with the preferred embodiments. The present invention, however, is not limited only to the above embodiments. It goes without saying that various design changes can be made without departing from the scope and spirit of the invention. 
     According to the present invention, wrapping around from the low-power amplifier section in an activated state to the high-power amplifier section in a deactivated state or from the high-power amplifier section in an activated state to the low-power amplifier section in a deactivated state can be reduced, so that a highly stable high-frequency power amplifier module can be provided.