WO2010071248A1

WO2010071248A1 - Enhanced chireix combiner

Info

Publication number: WO2010071248A1
Application number: PCT/KR2008/007493
Authority: WO
Inventors: Sang-Wook Nam; Sung-Ho Lee; Eunil Cho; Jaejun Lee
Original assignee: Snu R&Db Foundation
Priority date: 2008-12-17
Filing date: 2008-12-17
Publication date: 2010-06-24

Abstract

There are provided a enhanced Chireix combiner for linear amplification with nonlinear components(LINC) transmitter. In detail, the enhanced Chireix combiner includes: a first inductor, one end thereof being connected to a first input port and the other end thereof being connected to a GND; a first capacitor, one end thereof being connected to a second input port and the other end thereof being connected to the GND; a first transmission line, one end thereof being connected to the first input port and the other end thereof being connected to a load of an output port; a second transmission line, one end thereof being connected to the second input port and the other end thereof being connected to the load, wherein the first and the second transmission lines are realized by using metamaterial.

Description

[DESCRIPTION]

[Invention Title]

ENHANCED CHIREIX COMBINER

[Technical Field]

<i> The present invention relates to a Chireix combiner for linear amplification with nonlinear components(LINC) transmitter; and more particularly, to the Chireix combiner using metamaterial transmission line capable of easily combining the outphasing signals without any deterioration in efficiency, by referring to a relation between output load resistance and phase of the input signal.

[Background Art]

<2> Wireless communication is now omnipresent, making a life time of a battery especially critical for maintaining multiple functions of today's mobile equipment. To achieve long operation times in handheld equipment, many studies have focused on the structure of the power amplifier(hereinafter, PA) which is a main block of power consumption in most transmitters. One potential solution is a linear amplification with nonlinear components(LINC), as proposed by Chireix in 1935. LINC consists of two highly efficient nonlinear amplifiers and is one of the strongest candidates for a highly efficient PA. In a LINC system, an input signal containing both amplitude and phase modulation is divided into two constant envelope phase-modulated signals, and the divided signals are amplified respectively, and then the amplified branch signals are summed with a passive power combiner. In this way, maximum power is obtained when the two signals are in-phase, minimum power when the two signals are out of phase. Because the overall efficiency in the LINC system is affected by the combiner, the design of the combiner has been a critical issue.

[Disclosure]

[Technical Problem]

<3> There are three issues that need to be taken into consideration for the combiner: passivity, losslessness, and isolation. However, these attributes cannot be attained at the same time in a linear time-invariant system. As a result, there are numerous types of power combiners, each having their own merits and demerits.

<4> For a matched combiner, such as the Wilkinson combiner, as the phase difference between the two branches grows, the out-of-phase components of the combined signals are directed to the matched load of the input port and dissipated. The Wilkinson combiner leads to waste of power consumption and degradation of efficiency for a high peak to average power ratio (PAPR) signal with large out-of-phase differences.

<5> In the meantime, for a non-isolated combiners, such as a transformer and an LC balun, time-varying impedances are provided to PAs. If the PAs adopted in the non-isolated combiners act as ideal voltage sources, the dc power consumption will scale according to a load impedance if the reactance portion of the load impedance is well controlled. It can also act as a balun with impedance conversion. However, when the transformer or the LC balun is integrated into a chip using a lossy medium, such as the CMOS process, the power losses due to the weak magnetic coupling and the increase in area due to the finite quality factor of the transformer become serious. Therefore, it is important to reduce the number of inductors used in the nonisolated combiners to obtain high efficiency.

<6> Therefore, in recent years, many studies have been conducted to solve the problem of performance degeneration. One of the most attractive characteristic of LINC is the use of the Chireix power combiner. However, many devices that use the Chireix combiner have difficulty in converting a differential signal to a single output.

<7> Fig. 1 is a diagram illustrating a conventional structure of a Chireix combiner 100 which is a special nonisolating power combiner.

<8> Referring to Fig. 1, the conventional Chireix combiner 100 uses compensating reactive elements to enhance its power-combining efficiency. However, as the configuration of the Chireix combiner 100 is based on differential load, extra differential to single conversion is needed and the conversion process needs many passive components, resulting in decrease in output power and efficiency.

<9> To configure single-ended output of the Chireix combiner 100, two λ/4 transmission lines may be adopted therein. The combiner may have good efficiency when the amplifier is backed off from maximum output power, i.e., when the two input signals are not in-phase. However, the main drawback of the configuration using the two λ/4 transmission lines may be their large physical size. For example, when a frequency of an input signal is 200MHz, a wavelength corresponds to 1.5m, and thus, a size of each λ/4 transmission line reaches 37.5cm.

<io> As another solution for configuring the single-ended output of the Chireix combiner 100, the_. above-mentioned two λ/4 transmission lines may be replaced with lumped impedance inverters. However, since it uses too many inductors, the output configuration of PA may be complicated. Further, the efficiency may be deteriorated due to the finite inductor's quality factor. [Technical Solution]

<ii> It is, therefore, an object of the present invention to provide a configuration of an enhanced Chireix combiner for achieving a simple single- ended configuration without any deterioration in efficiency.

<i2> It is another object of the present invention to provide the configuration of the enhanced Chireix combiner capable of reducing the number of passive components, i.e., inductors, to be included therein.

<13> However, the objects of the present invention are not limited to the foregoing. [Advantageous Effects] <15> In accordance with the present invention, a single-ended transformation of the Chireix combiner may be embodied by simply adding a capacitor in one branch of a LINC transmitter and an inductor in the other branch thereof. <i6> Further, in accordance with the present invention, since a need for an external balun is eliminated, the efficiency of the Chireix combiner may be increased. <i7> Furthermore, in accordance with the present invention, since the number of passive components is reduced, the integration of the power amplifier and the combiner in a single chip can be facilitated. <i8> Furthermore, in accordance with the present invention, the values of the capacitance and the inductance can be optimized to the load resistance of

PA.

[Description of Drawings] <19> The above objects and features of the present invention will become more apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which: <20> Fig. 1 is a diagram illustrating a conventional structure of a Chireix combiner; <2i> Fig. 2 shows a quarter wave balun using metamaterial in accordance with one example embodiment of the present invention; <22> Fig. 3 illustrates a combined structure of the Chireix combiner and the balun using metamaterial in accordance with one example embodiment of the present invention; <23> Fig. 4 presents a simplified structure of Fig. 3 in accordance with one example embodiment of the present invention; <24> Fig. 5 presents an expanded structure of Fig. 4 in accordance with another example embodiment of the present invention; <25> Fig. 6 represents a graph showing a relation between an output load impedance looking at PA and a phase of the input signal in accordance with one example embodiment of the present invention;

<26> Fig. 7 indicates a block diagram of a LINC system adopting the enhanced Chireix combiner in accordance with one example embodiment of the present invention;

<27> Fig. 8 is a graph showing a simulated and measured efficiency of the enhanced Chireix combiner in accordance with one example embodiment of the present invention. [Best Mode]

<28> The configurations of the present invention for .accomplishing the above objects of the present invention are as follows.

<29> In one aspect of the present invention, there is provided a single- ended power combiner including: a Chireix combiner; and a balun which is combined with the Chireix combiner, wherein the balun is realized by using metamaterial .

<30> In another aspect of the present invention, there is provided a Chireix combiner using transmission line realized by metamaterial, the Chireix combiner including: a first inductor, one end thereof being connected to a first input port and the other end thereof being connected to a GND(ground) ; a first capacitor, one end thereof being connected to a second input port and the other end thereof being connected to the GND; a first transmission line, one end thereof being connected to the first input port and the other end thereof being connected to a load of an output port; a second transmission line, one end thereof being connected to the second input port and the other end thereof being connected to the load, wherein the first and the second transmission lines are realized by using metamaterial.

<3i> In still another aspect of the present invention, there is provided a Chireix combiner having at least two input ports and one output port, the Chireix combiner including: an inductor, one end thereof being connected to the first input port and the other end thereof being connected to a load of the output port; a capacitor, one end thereof being connected to the second input port and the other end thereof being connected to a load of the output port. [Mode for Invention]

<32> In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the present invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention. It is to be understood that the various embodiments of the present invention, although different from one another, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein in connection with one embodiment may be implemented within other embodiments without departing from the spirit and scope of the present invention. In addition, it is to be understood that the location or arrangement of individual elements within ■each disclosed embodiment may be modified without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled. In the drawings, like numerals refer to the same or similar functionality throughout the several views.

<33> The embodiments of the present invention will be described, in detail, with reference to the accompanying drawings.

<34>

<35> Chireix combiner and balun using metamaterial

<36>

<37> First, by referring to a conventional structure of Chireix combiner 100 shown in Fig, 1, a first input signal 140 with an amplitude of Vo and a phase of Φ is fed to one input port, and a second input signal 150 with an amplitude of Vo and a phase of -Φ is fed to the other input port. Herein, the first input signal 140 and^' the second input signal 150 may be derived from a first power amplifier and a second power amplif ier(not shown). <38> Further, the conventional Chireix combiner 100 includes : reactive components such as an inductor L_c 110 and a capacitor C_c 120 with one end thereof connected to each output of the power amplifiers and the other end thereof connected to the GND(ground) ,^" and an output load impedance. <39> Due to the inductor Lc 110 and the capacitor Cc 120, the Chireix combiner 100 provides time-varying impedances to the PAs as the phase difference between signals of the LINC amplifier changes. Therefore, the PAs can obtain their peak efficiency at a lower power in addition to the peak power, and the power where the peak efficiency occurs can be selected through the choice of the phase difference of the branches.

<40> According to the phase difference when the peak efficiency occurs, the values of the inductance Lc and the capacitance Cc are represented by formulas

(1) and (2):

<41>

<43>

<44> In the formulas (1) and (2), ω₀ represents operating fundamental frequency, 2Φ means outphasing angle between the input signals, and ROU_T corresponds to the output load impedance seen from the PA. <45> Herein, the formulas (1) and (2) may be derived by referring to a paper entitled "An outphasing power amplifier for a software-defined radio transmitter" by Moloudi et al . , presented in ISSCC Dig. Tech. Papers, Paper

31.6, pp.568-569, Feb. 2008. <46> Meanwhile, a balun using metamaterial which is combined with the conventional Chireix combiner 100 is shown in Fig. 2. <47> In accordance with one example embodiment of the present invention, a quarter wave balun 200 may be embodied by using plus λ/4 and minus λ/4 transmission lines based on metamaterial as shown in Fig. 2.

<48> Herein, the "balun" may be a type of electrical transformer that can convert electrical signals that are balanced about GND to signals that are unbalanced, and vice versa.

<49> Further, the "metamaterial (MTM)" may be broadly defined as artificial effectively homogeneous electromagnetic structures with' unusual properties not readily available in nature, and the "effectively homogeneous structure" means a structure whose average cell size should be at least smaller than the quarter of wavelength.

<50> Fig. 2 shows a quarter wave balun 200 using metamaterial in accordance with one example embodiment of the present invention.

<5i> In accordance with one example embodiment of ■ the present invention, the Chireix combiner 100 may be combined with a balun 200 including the plus quarter wave transmission line and the minus quarter wave transmission line which can be modeled into L, C components respectively as shown in regions 210, 220 of Fig. 2.

<52> Herein, the balun 200 using the plus and minus quarter wave transmission lines may be embodied by referring .to at least one of techniques well known to those skilled in the art such as a textbook entitled "Electromagnetic metamaterials: transmission line theory and microwave applications", by Caloz et al , published in 2006.

<53> According to the above-mentioned textbook, recently, a theory and implementation of a compact and practical LH-transmission line was developed, and the LH-transmission line is the electrically dual of the conventional transmission line, in which the inductance and capacitance have been interchanged, and realized by periodically loading a conventional transmission line with series capacitors and shunt inductors. Further, according to the above-mentioned textbook, the equivalent model of the LH- transmission line shows that it provides a negative phase delay or phase advance, in comparison with the conventional transmission line which has a positive phase delay. Herein, the above-mentioned textbook is incorporated in this specification by reference. Further, it is to be noted that the present invention should not be construed as being limited to the aforementioned techniques.

<54> Referring to Fig. 2, the balun 200 may be implemented by lumped reactive components in accordance with one example embodiment of the present invention. Further, the plus quarter wave transmission line may be realized by a shunt capacitor C_M 211, a series inductor L_M 212, and a shunt capacitor

C_M 213 and the minus quarter wave transmission line may be realized by a shunt inductor Lm 221, a series capacitor C_M 222 and a shunt inductor L_M 223. In this case, the "C_M 211- L_M 212 - Cu 213" structure and the "L_M 221 - C_B 222 - L_M

223" structure may provide a positive phase delay and a negative phase delay at a fundamental frequency, respectively. Thus, a differential signal at the two input branches becomes to be exactly in-phase on the two shunt output loads, i.e., 2RL(which will be explained later), guaranteeing complete isolation between PA differential branches. Therefore, in accordance with one example embodiment of the present . invention, the balun 200 can achieve the maximum output power even though input signals are out of phase. <55> The corresponding equations for ^' the inductance and the capacitance included in the balun 200 are represented by formulas (3)~(6):

<56> ω_z, = (3)

1

C* (5)

L (6)

<57> <58>

<59> In the formulas (3)-(6), ω₀ and Z₀ represent the fundamental frequency and characteristic impedance of the plus and minus quarter wave transmission line, respectively. <60> In the formula (4), since the characteristic impedance Zo is acquired by considering impedance at any location of a transmission line if looking toward the transmission line which is assumed to be infinitely long, it may be represented as the ratio of the voltage and the current at any location of the transmission line, and thus, the characteristic impedance can be expressed as the ratio of the inductance and the capacitance.

<6i> Herein, the formula (4) may be derived by referring to a textbook entitled "Field and Wave Electromagnetics" by David K. Cheng, published in 1989.

<62> As shown in Fig. 2, since the impedance of output load R_L 230 is 50Ω which is generally used in an antenna, the two branches can be considered as being separately connected to a 100Ω , i.e., 2R_L, in 180° phase displacement at the fundamental frequency.

<63> Further, as shown in Fig. 1 and Fig. 2, to avoid a wave reflection from the plus and the minus quarter wave transmission lines, it is desired to match, i.e., equalize, the impedance looking at PA ROUT with an input impedance Zj_n, looking toward the output load impedance RL at a point A of Fig. 2. In the balun 200 shown in Fig. 2, the input impedance Zj_n can be

2 determined as: the ratio of the square of the characteristic impedance Z₀ and the output load impedance RL, which is simplified to a following equation: Zj_n

<64> Consequently, the characteristic impedance Z₀ of the plus and the minus quarter wave transmission lines is represented as the geometric mean of the output load impedance 2R_L and the impedance looking at PA ROUT, as shown in a formula (7):

<65>

<67>

<68> Herein, the formula (7) may be derived by referring to a textbook entitled "Microwave Engineering" by David M. Pozar, published in 1990.

<69>

<70> Combined structure of Chireix combiner and balun using metamaterial

<71>

<72> In accordance with one example embodiment of the present invention, the conventional Chireix combiner 100 and the balun 200 using the metamaterial may be combined as fol lows'- <73> Fig. 3 illustrates a combined structure 300 of the conventional

Chireix combiner 100 and the balun 200 using the metamaterial in accordance with one example embodiment of the present invention. <74> Referring to Fig. 3, the capacitor C_M 213 in a region 310 and the inductor Lu 221 in the region 310 which are in parallel with the output load impedance RL 230 may be resonated out at the fundamental frequency. <75> Further, the inductor Lc 110 which was included in the conventional Chiriex combiner 100 in a region 320 and the capacitor C_M 211 in the region

320 may also be resonated out at the operating frequency. <76> Furthermore, the inductor L_M 223 in a region 330 and the capacitor Cc

120 which was included in the conventional Chiriex combiner 100 in the region 330 may also be resonated out at the operating frequency.

<77> Fig. 4 represents a simplified structure of Fig. 3 in accordance with one example embodiment of the present invention.

<78> Referring to Fig. 4, a first input signal 140 with an amplitude of V₀ and a phase of Φ is fed to one input port, and a second input signal 150 with an amplitude of V₀ and a phase of -Φ is fed to the other input port.

<79> Since three pairs of inductors and capacitors are resonated out at the operating frequency as mentioned above, the simplified structure of Fig. 3 is represented as Fig. 4.

<80> Further, Fig. 5 represents an expanded structure of Fig. 4 in accordance with another example embodiment of the present invention.

<8i> Referring to Fig. 5, the expanded structure 500 includes two enhanced Chireix combiners of Fig. 4. Further, the number of the enhanced Chireix combiners included in the expanded structure may also be increased to more than two(not shown).

<82> As shown in Fig. 5, the expanded structure 500 may have two pairs of input ports and each input port is connected to each output port of PAs. In detail, the expanded structure may have two pairs of inductors and capacitors 510-540, one end thereof being connected to each of the input ports 560-590 respectively and the other end thereof being connected to the output load R_L

550.

<83> As mentioned above, in accordance with another example embodiment of the present invention, the expanded structure 500 can be adopted to n LINC structures(n is an integer)-. In this case, since the impedance of output load R_L 550 is assumed to be 50Ω which is generally used as an antenna, the

2n branches of the n enhanced Chireix combiners can be considered as being separately connected to a n • 100Ω, i.e., 2n ^• R_L, in 180° phase displacement at the fundamental frequency. Accordingly, the corresponding equations for the inductances and the capacitances included in the expanded structure 500 are represented by formulas (8)-(9):

<84> c_v_ i ₌ i i i i_ ωo-Za ωo_Λfn-2Ri-ROUT ωo IQ-Jn-ROUT

Zo -Jn'2Rz,-RoTX- IQ*Jn-ROUT /_Q*

_<85> Φo ύ)o ϋ)o

<86>

<87> Meanwhile, by referring to the enhanced Chireix combiner of Fig. 3, since three pairs of inductors and capacitors are resonated out at the operating frequency, the multiplication of the capacitance C_M and the inductance L_M in the region 310, the multiplication of the inductance Lc and the capacitance C_M in the region 320, and the multiplication of the inductance LM and the capacitance Cc in the region 330 should have the same value, i.e., CM ^• L_JI = Lc ^• CM = L_M ^• Cc, in accordance with one example embodiment of the present invention. <88> Therefore, the values of capacitance C_c and inductance Lc in the formulas (1) and (2) are the same as those of capacitance C_M and inductance L_M in the formulas (5) and (6). By calculating the two equations, the relation between the phase of the input signal Φ and the impedance looking at PA R_OUT is represented by a formula (10):

<89> <90> ~²'-;/iB?fer⁰²- ⁽¹⁰⁾ <91>

<92> In the formula (10), the maximum obtainable value for the impedance ROU_T is 25Ω. Therefore, this equation is valid for PAs with R_OUT under 25Ω.

However, this is not a problem, because R_OUT is usually very small at high power .

<93> Fig. 6 is a graph showing a relation between the phase of the input signal Φ and the impedance R_OU_T in accordance with the present invention.

<94> Referring to Fig. 6, the phase of the input signal Φ at the peak efficiency may be determined by the output load impedance R_OUT- For example, when the output load impedance ROU_T is 10Ω, the peak efficiency in the enhanced Chireix combiner occurs in 20° phase of the input signal in the

LINC structure.

<95> Fig. 7 illustrates a Block diagram of the LINC system adopting the enhanced Chireix combiner in accordance with one example embodiment of the present invention.

<96> Referring to Fig. 7, by simply adding the capacitor Cu 741 and the inductor Lu 742 (which correspond to the capacitor 222 and the inductor 212 respectively) in each branch of the LINC transmitter, a single-ended transformation of the enhanced Chireix combiner 740 can be achieved. <97> In accordance with one example embodiment of the present invention, RF input signal is fed into a signal component separator 710 and then separated into two signals having different phase each other by the signal component separator 710. Thereafter, the two separated signals may be amplified by two power amplifiers 720, 730, respectively, and then finally the two amplified signals may be combined in the enhanced Chireix combiner 740. Therefore, in accordance with the present invention, the enhanced Chireix combiner 740 may^¬ be useful for the LINC transmitter. <98>

<99> Measurement results

<ioo> For measurement, the test board of the enhanced Chireix combiner 740 in accordance with the present invention was designed. The test board was made on loz, 0.762mm thickness R04350B printed circuit board. To minimize the effect of the nonideal voltage source and verify only effects of the inductor and the capacitor, it was designed to operate at a 50 MHz frequency. Therefore, in accordance with one example embodiment of the present invention, the physical length of the line may be very short compared to the wavelength of the input signals. For the input source, multiple parallelized video drivers(EL7156) with high driving capability were used as voltage sources. Further _(i a lOOpF capacitance and a 10OnH inductance were found to be for 10Ω load resistance, as well, the corresponding phase was 20° for the maximum efficiency.

<ioi> Fig. 8 shows a graph showing a simulated and a measured efficiency of the enhanced Chireix combiner 740 in accordance with one example embodiment of the present invention.

<iO2> Referring to Fig. 8, a solid line and a dotted line represents the simulated and the measured efficiency of the enhanced Chireix combiner according to the phase of the input signal, respectively. In accordance with one example embodiment of the present invention, to investigate only the performance of the proposed combiner, the efficiency of the drivers is deembeded from the result. From the measured result, the maximum 97% efficiency is obtained at 20° phase of input signal, as the same to the simulated result, and due to the finite quality factor of the inductor and the on-τesistance of voltage sources, the small efficiency drop is occurred.

<iO3> In accordance with one example embodiment of the present invention, overall trends of results are the same to the expected, and high performance PA driving low impedance may improve the combiner efficiency with aids of accurate modeling.

<iO4> Further, on-chip integration will reduce the mismatch between PAs and be useful for high frequency applications with small area.

<iO5> While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modification may be made without departing from the spirit and scope of the invention as defined in the following claims.

<i06> Accordingly, the thought of the present invention must not be confined to the explained embodiments, and the following patent claims as well as everything including variations equal or equivalent to the patent claims pertain to the category of the thought of the present invention.

Claims

[CLAIMS] [Claim 1]

<iO8> A single-ended power combiner comprising'- a Chireix combiner! and a balun which is combined with the Chireix combiner, wherein the balun is realized by using metamaterial .

[Claim 2]

<iO9> The power combiner of claim 1, wherein the balun includes a plus λ/4 transmission line and a minus λ/4 transmission line.

[Claim 3]

<iio> The power combiner of claim 1, wherein the power combiner has: a first input port connected to an output port of a first power amplifier," a second input port connected to an output port of a second power amplifier; and an output port connected to a load.

[Claim 4]

<πi> The power combiner of claim 3, wherein the balun is equivalent of: <ii2> an inductor located between the first input port and the output port connected to the load; and

<ii3> a capacitor located between the second input port and the output port connected to the load.

[Claim 5]

<ii4> The power combiner of claim 4, wherein, after an RF input signal is separated into a first input signal and a second input signal having respective phases by a signal separator, the first input signal and the second input signal are fed to an input port of the first power amplifier and an input port of the second power amplifier, respectively.

[Claim 6] <ii5> A Chireix combiner using transmission line realized by metamaterial, the Chireix combiner comprising-' <ii6> a first inductor, one end thereof being connected to a first input port and the other end thereof being connected to a GND(ground); <ii7> a first capacitor, one end thereof being connected to a second input port and the other end thereof being connected to the GND; <H8> a first transmission line, one end thereof being connected to the first input port and the other end thereof being connected to a load of an output port ; <ii9> a second transmission line, one end thereof being connected to the second input port and the other end thereof being connected to the load, <i20> wherein the first and the second transmission lines are realized by using metamateria1.

[Claim 7] <i2i> The Chireix combiner of claim 6, wherein if a wavelength of a signal fed to the first and the second input ports is λ , the first transmission line is a plus λ/4 transmission line and the second transmission line is a minus λ/4 transmission line.

[Claim 8] <122> The Chireix combiner of claim 6, wherein one end of the load of the output port is connected to the first and the second transmission lines and the other end of the load is connected to the GND.

[Claim 9] <123> The Chireix combiner of claim 8, wherein the first transmission line is equivalent of a first shunt capacitor, a first series inductor, and a second shunt capacitor, and the second transmission line is equivalent of a first shunt inductor, a first series capacitor, and a second shunt inductor, <124> and wherein the first inductor and the first shunt capacitor are in parallel; the second shunt capacitor and the first shunt inductor are in parallel with the load of the output port; and the second shunt inductor and the first capacitor are in parallel.

[Claim 10] <125> The Chireix combiner of claim 9, wherein at a operating fundamental frequency, the first inductor and the first shunt capacitor are resonated out, the second shunt capacitor and the first shunt inductor are resonated out, and the second shunt inductor and the first capacitor are resonated out.

[Claim 11] <i26> A Chireix combiner having at least two input ports and one output port, the Chireix combiner comprising: <i27> a first inductor, one end thereof being connected to a first input port and the other end thereof being connected to a load of the output port; <128> a first capacitor, one end thereof being connected to a second input port and the other end thereof being connected to the load of the output port.

[Claim 12] <i29> The Chireix combiner of claim 11, wherein, if 2Φ represents a phase difference between a signal fed to the first input port and a signal fed to the second input port, RL which represents an output load impedance is 50Ω, and ROUT represents an impedance looking at the first or the second input port, the 2Φ, the R_L, and the R_OUT satisfy the following equation:

[Claim 13]

<i3i> The Chireix combiner of claim 11, further comprising: <132> a second inductor, one end thereof being connected to a third input port and the other end thereof being connected to the load of the output port ; <133> a second capacitor, one end thereof being connected to a fourth input port and the other end thereof being connected to the load of the output port .

[Claim 14] <134> The Chiriex combiner of claim 11, wherein the Chireix combiner includes n LINC structures, each of n pairs including a capacitor and an inductor being disposed between each of the input ports and the Toad of the output port.