Abstract:
There is provided a radio frequency (RF) signal amplifying device consuming less power and operable at a high voltage in a PA driving amplifying apparatus applicable to a PA amplifying circuit which amplifies power of an RF signal. The RF signal amplifying device includes: a balun converting an unbalanced radio frequency signal into a balanced radio frequency signal; a primary amplifier differentially amplifying the balanced radio frequency signal from the balun; and at least one secondary amplifier secondarily and differentially amplifying the balanced radio frequency signal amplified from the primary amplifier.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 2007-57942 filed on Jun. 13, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an amplifying device, and more particularly, to a radio frequency (RF) signal amplifying device consuming less power and operable at a high voltage in a power amplifier (PA) driving amplifying apparatus applicable to a PA amplifying circuit which amplifies power of an RF signal. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, development of wireless communication has also led to development of various wireless communication transceiver devices. Also, a radio frequency (RF) signal amplifier employed in these wireless communication transceiver devices has been under development. 
         [0006]    A conventional RF signal amplifier will be described with reference to  FIG. 1 . 
         [0007]      FIG. 1  is a circuit diagram illustrating the conventional RF signal amplifying device. 
         [0008]    Referring to  FIG. 1 , the conventional amplifying device  10  includes an amplifying part  11  having a plurality of switches differentially switched on/off from one another and an inductor part  12  supplying a direct current (DC) to the amplifying part  11 . 
         [0009]    The aforesaid conventional amplifying device  10  includes inductors  12   a  and  12   b  supplying the DC, which add to the size of the amplifying device. Besides, the amplifying device  10  consumes a considerable amount of power due to resistance of the inductors thereby to be degraded in efficiency. 
       SUMMARY OF THE INVENTION 
       [0010]    An aspect of the present invention provides a radio frequency (RF) signal amplifying device consuming less power and operable at a high voltage in a power amplifier (PA) driving amplifying apparatus applicable to a PA amplifying circuit which amplifies power of a signal. 
         [0011]    According to an aspect of the present invention, there is provided an RF signal amplifying device including: a balun converting an unbalanced RF signal into a balanced RF signal; a primary amplifier differentially amplifying the balanced RF signal from the balun; and a secondary amplifying group including at least one secondary amplifier secondarily and differentially amplifying the balanced RF signal amplified from the primary amplifier, wherein the primary amplifier includes: a first amplifying unit disposed between a driving power terminal supplying a predetermined driving power and a ground, the first amplifying unit differentially amplifying the balanced RF signal and outputting a first balanced RF signal having a predetermined voltage level; a second amplifying unit connected in series between the driving power terminal and the first amplifying unit, and complementarily switched on/off with the first amplifying unit, the second amplifying unit differentially amplifying the balanced RF signal and outputting a second balanced RF signal having a voltage level higher than the voltage level of the first balanced RF signal, and the secondary amplifying group includes a first secondary amplifier, wherein the first secondary amplifier includes: a third amplifying unit disposed between the driving power terminal and the ground, the third amplifying unit secondarily and differentially amplifying the first balanced RF signal from the primary amplifier; and a fourth amplifying unit connected in series between the driving power terminal and the third amplifying unit, and complementarily switched on/off with the third amplifying unit, the fourth amplifying unit secondarily and differentially amplifying the second balanced RF signal from the primary amplifier. 
         [0012]    The primary amplifier may include: first to fourth input capacitors connected in series between signal input terminals of the first and second amplifying units and output terminals of the balanced RF signal from the balun, respectively; and first to fourth resistors connected in series between the first to fourth input capacitors and output terminals of the first and second balanced RF signals, respectively, wherein the first to fourth capacitors eliminate a direct current component from the balanced RF signal from the balun, respectively, and the first to fourth resistors separate the balanced RF signal terminals and the output terminals of the first and second balanced RF signals from each other, and supply a bias power to the first and second amplifying units, respectively. 
         [0013]    The first secondary amplifier may include: a plurality of bias voltages connected in series between the driving power terminal and an input terminal of the first balanced RF signal, and between the ground and an input terminal of the second balanced RF signal, respectively, the bias voltages supplying a bias power to the third and fourth amplifying units, respectively; a plurality of first separation resistance groups connected in series between the input terminals of the first and second balanced RF signals and the output terminals of the secondarily amplified RF signal, respectively, the first separation resistance groups separating input and output signals from each other; and a plurality of second separation resistance groups connected in series between corresponding ones of the output terminals of the secondarily amplified RF signal having different polarities from each other to separate each output signal. 
         [0014]    The first amplifying unit may include a plurality of amplifying elements, the plurality of amplifying elements including at least two groups of amplifying elements where at least two of the amplifying elements are connected in series to each other, the two groups of amplifying elements connected in parallel to each other to differentially amplify the balanced RF signal, the second amplifying unit includes a plurality of amplifying elements, the plurality of amplifying elements of the second amplifying unit including at least two groups of amplifying elements where at least two of the amplifying elements of the second amplifying unit are connected in series to each other, the two groups of amplifying elements of the second amplifying unit are connected in parallel to each other to be complementarily switched on/off with the two groups of amplifying elements of the first amplifying unit, each of the respective two groups of amplifying elements of the first and second amplifying units includes a P-channel field effect transistor and an N-channel field effect transistor, wherein the P-channel field effect transistor has a gate receiving the balanced RF signal, a source receiving a power source and a drain outputting an amplified signal, and the N-channel field effect transistor has a gate receiving the balanced RF signal, a source receiving a power source and a drain outputting an amplified signal and connected to the drain of the P-channel field effect transistor. 
         [0015]    The N-channel field effect transistors of the first amplifying unit may have respective source terminals connected together and the P-channel field effect transistors of the second amplifying unit may have respective source terminals connected to the respective source terminals of the N-channel field effect transistors of the first amplifying unit to thereby form a virtual ground. 
         [0016]    The third amplifying unit of the secondary amplifier may include a plurality of cascode amplifying elements connected in parallel to one another to differentially amplify the first balanced RF signal, and the fourth amplifying unit connected in series between the driving power terminal and the third amplifying unit, the fourth amplifying unit including a plurality of cascode amplifying elements complementarily switched on/off with the plurality of cascode amplifying elements of the third amplifying unit, the plurality of cascode amplifying elements of the fourth amplifying unit connected in parallel to one another to differentially amplify the second balanced RF signal. 
         [0017]    The third amplifying unit of the first secondary amplifier may include first and second cascode amplifying elements connected in parallel to each other, wherein the first cascode amplifying element includes a first field effect transistor having a gate receiving the first balanced RF signal, a source connected to the ground and a drain outputting an amplified signal, and a second field effect transistor having a source connected to the drain of the first field effect transistor, a drain outputting an amplified signal and a gate, and the second cascode amplifying element includes a third field effect transistor having a gate receiving the first balanced RF signal, a source connected to the ground and a drain outputting an amplified signal, and a fourth field effect transistor having a source connected to the drain of the third field effect transistor, a drain outputting an amplified signal and a gate, the fourth amplifying unit of the first secondary amplifier includes third and fourth cascode amplifying elements, wherein the third cascode amplifying element includes a fifth field effect transistor having a source receiving the driving power, a gate receiving the second balanced RF signal and a drain, and a sixth field effect transistor having a source connected to the drain of the fifth field effect transistor, a drain outputting an amplified signal and a source, and the fourth cascode amplifying element includes a seventh field effect transistor having a source receiving the driving power, a gate receiving the second balanced RF signal, and a drain, and an eighth field effect transistor having a source connected to the drain of the seventh field effect transistor, a drain outputting an amplified signal, and a source. 
         [0018]    The second and fourth field effect transistors may have the respective gates connected together and the sixth and eighth field effect transistors may have the respective gates connected to the respective gates of the second and fourth field effect transistors together to thereby form a virtual ground. 
         [0019]    The secondary amplifying group may further include: second and third secondary amplifiers each connected in parallel to the first secondary amplifier and secondarily amplifying the first and second balanced RF signals, respectively; and wherein the second secondary amplifier includes a fifth amplifying unit disposed between the driving power terminal and the ground and having a plurality of cascode amplifying elements connected in parallel to one another to differentially amplify the first balanced RF signal; and a sixth amplifying unit connected in series between the driving power terminal and the fifth amplifying unit and having a plurality of cascode amplifying elements complementarily switched on/off with the plurality of cascode amplifying elements of the fifth amplifying unit to differentially amplify the second balanced RF signal; and the third secondary amplifier includes a seventh amplifying unit disposed between the driving power terminal and the ground and having a plurality of cascode amplifying elements connected in parallel to one another to differentially amplify the first balanced RF signal, and an eighth amplifying unit connected in series between the driving power terminal and the seventh amplifying unit and having a plurality of cascode amplifying elements complementarily switched on/off with the plurality of cascode amplifying elements of the seventh amplifying unit to differentially amplify the second amplified balanced RF signal. 
         [0020]    In respective output terminals of the first to third secondary amplifiers, corresponding ones of the output terminals outputting the balanced RF signal having phases identical to each other may be commonly connected. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0022]      FIG. 1  is a circuit diagram illustrating a conventional amplifying device; 
           [0023]      FIG. 2  is a schematic structural view illustrating an amplifying device according to an exemplary embodiment of the invention; 
           [0024]      FIGS. 3A and 3B  are circuit diagrams illustrating a primary amplifier and a secondary amplifier applied to an amplifying device, respectively according to an exemplary embodiment of the invention; and 
           [0025]      FIGS. 4A and 4B  are graphs illustrating output signals of primary and secondary amplifiers applied to an amplifying device, respectively according to an exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
         [0027]      FIG. 2  is a schematic structural view illustrating an amplifying device according to an exemplary embodiment of the invention. 
         [0028]    Referring to  FIG. 2 , the amplifying device  100  of the present embodiment includes a balun  110  and an amplifying part  120 . 
         [0029]    The balun  110  receives an unbalanced radio frequency (RF) signal and outputs a balanced RF signal having phases opposite to each other. 
         [0030]    The amplifying part  120  amplifies a voltage level of the balanced RF signal from the balun  110 . 
         [0031]    The amplifying part  120  may include a plurality of amplifiers to amplify a current of the balanced RF signal to a necessary level. Accordingly, the amplifying part  120  may include a primary amplifier  121  and a secondary amplifier group  122 . 
         [0032]    The primary amplifier  121  may include first and second amplifying units  121   a  and  121   b.  The first and second units  121   a  and  121   b  output first and second balanced radio frequency (RF) signals having voltage levels different from each other, respectively. The secondary amplifier group may include a plurality of secondary amplifiers secondarily amplifying the balanced RF signals primarily amplified by the primary amplifier  121 . 
         [0033]    The secondary amplifier group  122  may include first to third secondary amplifiers  122   a,    122   b,  and  122   c  according to an exemplary embodiment of the invention. The first to third secondary amplifiers  122   a,    122   b,  and  122   c  each may include two amplifying units connected to each other between a driving power terminal and a ground. 
         [0034]    The secondarily amplified balanced RF signal from the secondary amplifier group  122  may be utilized as a driving signal for driving a power amplifier (PA) employed in a global system for mobile communications (GSM) or a general packet radio service (GPRS). 
         [0035]    The primary amplifier  121  and the secondary amplifier group  122  will be described in detail with reference to  FIGS. 3A and 3B . 
         [0036]      FIGS. 3A and 3B  are circuit diagrams illustrating the primary and secondary amplifiers applied to the amplifying device of the present embodiment. 
         [0037]    Referring to  FIG. 3A , the primary amplifier  121  employed in the amplifying device of the present embodiment may include a first amplifying unit  121   a  disposed between a driving power terminal Vdd and a ground, and a second amplifying unit  121   b  connected in series to the first amplifying unit  121   a  between the driving power terminal Vdd and the first amplifying unit  121   a.    
         [0038]    The first amplifying unit  121   a  may be formed of first to fourth field effect transistors (FET)s. Here, the first FET M 1  has a drain connected in series to a drain of the second FET M 2 , and the third FET M 3  has a drain connected in series to a drain of the fourth FET M 4 . Moreover, each of the first to fourth FETs M 1 , M 2 , M 3 , and M 4  has a balanced radio frequency (RF) signal from the balun  110 . Here, out of the balanced RF signal, a positive (+) balanced RF signal component may be inputted to the gates of the first and second FETs M 1  and M 2 , respectively. On the contrary, a negative (−) balanced RF signal component having a phase difference of 180° from the positive (+) balanced RF signal component may be inputted to the gates of the third and fourth FETs M 3  and M 4 , respectively. The first and second FETs M 1  and M 2  are connected in parallel with the third and fourth FETs M 3  and M 4  to thereby form the first amplifying unit  121   a.    
         [0039]    Likewise, the second amplifying unit  121   b  may be formed of fifth to eighth FETS M 5 , M 6 , M 7  and M 8 . Here, the fifth FET M 5  has a drain connected in series to a drain of the sixth FET M 6 , and the seventh FET M 7  has a drain connected in series to a drain of the eighth FET M 8 . Moreover, each of the fifth to eighth FETs M 5 , M 6 , M 7 , and M 8  has a gate receiving a balanced RF signal from the balun  110 . A positive (+) balanced RF signal component may be inputted to the gates of the fifth and sixth FETs M 5  and M 6 , respectively. Meanwhile, a negative (−) balanced RF signal may be inputted to the gates of the seventh and eighth FETs M 7  and M 8 , respectively. The fifth and sixth FETs M 5  and M 6  are connected in parallel to the seventh and eighth FETs MI 3  and MI 4  to thereby form the second amplifying unit  121   b.    
         [0040]    Out of the first to eighth FETS, the first, third, fifth and seventh FETs M 1 , M 3 , M 5 , and M 7  may be configured as a P-channel FET. On the contrary, the second, fourth, sixth and eighth FETs M 2 , M 4 , M 6  and M 8  may be configured as an N-channel FET. 
         [0041]    Also, signals are separated through resistors R connected to input terminals of the balanced RF signal and output terminals of the first and second balanced RF signals RF out high+, RF out high−, RF out low+, and RF out low−, respectively and a bias power of each of the FETs is supplied. Also, corresponding ones of the first to fourth input capacitors Ci 1  ,Ci 2 , Ci 3 , and Ci 4  are connected to the input terminals of the balanced RF signal, respectively to inhibit transfer of a DC component of the balanced RF signal. 
         [0042]    The primary amplifier  121  has the first amplifying unit  121   a  and the second amplifying unit  121   b  connected in series to each other between the driving power terminal Vdd and the ground to have the driving power Vdd distributed thereto. Therefore, even though a high driving power Vdd of e.g., 3.4V is applied, each of the FETs can have an allowable voltage of 0.75V applied thereto so as to be stably operable. 
         [0043]    Accordingly, the first and second balanced RF signals RF out high+, RF out high−, RF out low+, and RF out low− outputted from the first and second amplifying units  121   a  and  121   b  of the primary amplifier  121 , respectively have a voltage level different from each other. As described, when a driving voltage of 3.4V is applied, the each of the FETs may have a voltage drop of about 0.75V. Given this, the second balanced RF signal RF out high+ and RF out high− has a voltage level of about 2.48V and the first balanced RF signal RF out low+ and RF out low− has a voltage level of about 0.78V. 
         [0044]    Referring to  FIG. 3B , the secondary amplifier group  122  employed in the amplifying device of the present embodiment may include first to third secondary amplifiers  122   a,    122   b,  and  122   c.  When it comes to a structure of the first secondary amplifier, the first secondary amplifier  122   a  includes a third amplifying unit  122   a   1  disposed between the driving power terminal Vdd and the ground and a fourth amplifying unit  122   a   2  disposed between the driving power terminal Vdd and the third amplifying unit  122   a   1  and connected in series to the third amplifying unit  122   a   1 . 
         [0045]    The third amplifying unit  122   a   1  includes ninth to twelfth FETs M 9 , M 10 , M 11 , and M 12 . The ninth FET M 9  has a drain connected in series to a source of the tenth FET M 10  to form a first cascode amplifying element. Also, the eleventh FET M 11  has a drain connected in series to a source of the twelfth FET M 12  to form a second cascode amplifying element. The first cascode amplifying element and the second cascode amplifying element are connected in parallel to each other to form a third amplifying unit  122   a   1 . 
         [0046]    Likewise, the fourth amplifying unit  122   a   2  includes thirteenth to sixteenth FETs M 13 , M 14 , M 15 , and M 16 . The thirteenth FET M 13  has a drain connected in series to a source of the fourteenth FET M 14  to form a third cascode amplifying element. Also, the fifteenth FET M 15  has a drain connected in series to a source of the sixteenth FET M 16  to form a second cascode amplifying element. The third cascode amplifying element and the fourth cascode amplifying element are connected in parallel to each other to form a fourth amplifying unit  122   a   2 . 
         [0047]    The third amplifying unit  122   a   1  and the fourth amplifying unit  122   a   2  are connected in series to each other between the driving power terminal Vdd and the ground, and thus can operate easily when a high voltage of the driving power Vdd is supplied. The tenth FET M 10  has a gate connected to a gate of the twelfth FET M 12  and the fourteenth FET M 14  has a gate connected to a gate of the sixteenth FET M 16  to form a virtual ground, thereby ensuring the signal to be amplified stably. 
         [0048]    Furthermore, the signals are separated through first separation voltages Rds connected to the input terminals of the first and second balanced RF signals RF out high+, RF out high−, RF out low+ and RF out low− and the output terminals of the secondarily-amplified balanced RF signal, respectively. The driving power Vdd is distributed by bias voltages Rd to supply necessary power source to each of the FETs. Also, a DC bias voltage is applied to the gates of the tenth FET M 10 , the twelfth FET M 12 , the fourteenth FET M 14  and the sixteenth FET M 16  by resistors Rf, respectively. 
         [0049]    Moreover, the ninth to twelfth FETs may be configured as an N-channel FET and the thirteenth to sixteenth FETs may be configured as a P-channel FET. Out of the first and second balanced RF signals, positive (+) first and second balanced RF signals RF in high+ and RF in low+ may be inputted to the gates of the ninth and thirteenth FETs M 9  and M 13 , respectively. Meanwhile, out of the first and second balanced RF signals, negative (−) first and second balanced RF signals RF in high− and RF in low− may be inputted to the eleventh and fifteenth FETs M 11  and M 15 , respectively. In addition, out of the secondarily-amplified balanced RF signal, a secondarily-amplified positive (+) balanced RF signal component RF out+ may be outputted from a node where the tenth and fourteenth FETs M 10  and M 14  have respective drains connected together. Meanwhile, out of the secondarily-amplified balanced RF signal, a secondarily-amplified negative (−) balanced RF signal component RF out− may be outputted from a node where the twelfth and sixteenth FETs M 12  and M 16  have respective drains connected together to have a phase difference of 180° from the secondarily-amplified positive (+) balanced RF signal component RF out+. 
         [0050]    The second and third secondary amplifiers are structured identically to the first secondary amplifier. In a brief description, the second secondary amplifier  122   b  includes a fifth amplifying unit  122   b   1  and a sixth amplifying unit  122   b   2 . The fifth amplifying unit  122   b   1  includes seventeenth to twentieth FETs M 17 , M 18 , M 19 , and M 20  structured identically to the ninth to twelfth FETs M 9 , M 10 , M 11 , and M 12 . The sixth amplifying unit  122   b   2  includes twenty first to twenty fourth FETs M 21 , MI 22 , MI 23 , and MI 24  structured identically to the thirteenth to sixteenth 16 FETs M 13 , M 14 , M 15 , and M 16 . 
         [0051]    Likewise, the third secondary amplifier  122   c  includes a seventh amplifying unit  122   c   1  and an eighth amplifying unit  122   c   2 . The seventh amplifying unit includes twenty fifth to twenty eighth FETs M 25 , M 26 , M 27 , and M 28  structured identically to the ninth to twelfth FETs M 9 , M 10 , M 11 , and M 12 . The eighth amplifying unit  122   c   2  includes twenty ninth to thirty second FETS M 29 , M 30 , M 31 , and M 32  structured identically to the thirteenth to sixteenth FETs M 13 , M 14 , M 15 , and M 16 . 
         [0052]    The first to third secondary amplifiers  22   a,    122   b,  and  122   c  are connected in parallel to one another to secondarily amplify a voltage level of the balanced RF signal amplified from the primary amplifier  121 . Here, corresponding ones of first to sixth output capacitors Co 1 , Co 2 , Co 3 , Co 4 , Co 5 , and Co 6  are connected to the output terminals of the first to third secondary amplifiers  122   a,    122   b  and  122   c,  respectively to block output of a DC component included in the secondarily-amplified balanced RF signal. Also, corresponding ones of the output terminals outputting the balanced RF signals having identical phases to each other are commonly connected. 
         [0053]    This allows the balanced RF signals outputted from the output terminals to be balanced in phase to decrease occurrence of harmonic waves, thereby enhancing efficiency. 
         [0054]    In addition, the primary amplifier  121  and the first to third secondary amplifiers  122   a,    122   b,  and  122   c  are grounded through a current balanced inductor L. 
         [0055]      FIGS. 4A and 4B  are graphs illustrating output signals of the primary amplifier and the second amplifier employed in the amplifier of the present embodiment. 
         [0056]      FIG. 4A  plots a balanced RF signal amplified by the primary amplifier employed in the amplifier according to the present embodiment. The balanced RF signal is amplified by about 10 dB from an input RF signal. Thus, a secondary amplifier is required to enable the RF signal to be amplified by 21 dB or more as the users generally require. 
         [0057]      FIG. 4B  plots a balanced RF signal secondarily amplified by a secondary amplifying group employed in the amplifying device according to the present embodiment. Here, the balanced RF signal amplified by the primary amplifier is secondarily amplified by 21 dB or more which is a level required by the users. The secondarily-amplified balanced RF signal has a squarer shape than the primarily-amplified balanced RF signal to reduce current consumption resulting from switching of the FETs. 
         [0058]    The RF signal amplifying device of the present embodiment converts an unbalanced RF signal into a balanced RF signal and amplifies a voltage of the balanced RF signal to a usable level to act as a driving amplifier of an RF signal power amplifying apparatus which can be connected to a rear end thereof. 
         [0059]    As set forth above, an RF signal amplifying device according to exemplary embodiments of the invention has a pair of cascode amplifiers and a pair of cascode inverting amplifiers connected in series to each other between a driving power and a ground, thus operating stably at a driving power having a high voltage of about 3.4 v. Also, the RF signal amplifying device can act as a driving amplifier supplying a necessary voltage to an RF signal power amplifying apparatus employed in a GSM/GPRS. Moreover, output terminals outputting a balanced RF signal having identical phases to each other are commonly connected to reduce harmonic waves and increase efficiency. 
         [0060]    In addition, some of the amplifiers have gates virtually grounded to ensure signals to be amplified stably. 
         [0061]    While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.