Power amplifier arrangement with enhanced bandwidth

Abstract

A power amplifier arrangement (100) is disclosed. The power amplifier arrangement (100) is a Doherty power amplifier based on two coupled transmission lines. The power amplifier arrangement (100) comprises a first power amplifier (P1) as a main amplifier and a second power amplifier (P2) as an auxiliary amplifier. The power amplifier arrangement (100) further comprises an input power splitter (PS) and a quadrature coupler (120), the quadrature coupler (120) comprising two coupling transmission lines (TL1 / TL2). The isolation port of the quadrature coupler is open. The coupling coefficient of the two coupled transmission lines (TL1 / TL2) is determined based on an output power back-off level of desired operation of the power amplifier arrangement (100). The characteristic impedance of the two coupled transmission lines is determined by the optimal load impedance of the first power amplifier (P1) and the coupling coefficient of the two coupled transmission lines. The load impedance of the quadrature coupler (120) is determined by the optimal impedance of the first power amplifier and the transition point zeta b of the voltage drive level.

Description

Technical Field

[0001] Embodiments herein relate to power amplifier arrangements. In particular, they relate to power amplifier arrangements with enhanced bandwidth. Furthermore, embodiments relate to electronic devices including power amplifier arrangements. Background Art

[0002] In wireless communication systems, transmitters use power amplifiers (PAs) to increase the power of radio frequency (RF) signals before transmission. The PA is expected to linearly amplify the input signal and generate an output signal with greater power but the same characteristics as the input signal.

[0003] As signal bandwidth increases, new frequency bands are being assigned to fifth- and sixth-generation (5G / 6G) wireless communication networks. To achieve high spectral efficiency and high-speed data transmission, 5G / 6G wireless communication networks use highly modulated signals with large peak-to-average power ratios (PAPRs). Furthermore, 3G, 4G, 5G, and 6G communication standards differ, and their modulation formats also differ. Different modulated signals have different PAPRs.

[0004] Therefore, a desirable power amplifier should have a wide bandwidth and high power-added efficiency (PAE) over a wide power back-off range from maximum output power. PAE is defined by the equation PAE = 100 × (Pout – Pin) / PDC, where PDC is the input DC power, Pout is the RF output power, and Pin is the PA's RF input power. It is desirable for the PA to operate near its saturation point, as this is where efficiency is highest. The amount by which the power level is reduced is known as power back-off. There are two types of power back-off: input power back-off (IPBO) and output power back-off (OPBO). IPBO refers to the power level at the PA input relative to the input power that produces maximum output power. OPBO refers to the power level at the PA output relative to the maximum possible output power level. For example, if the maximum output power level is +40 dBm and the amplifier's measured output power level is +34 dBm, the OPBO level is 6 dB.

[0005] To enhance PA efficiency during power back-off, the Doherty power amplifier (DPA) is the most widely used topology. A DPA consists of a main amplifier, an auxiliary amplifier, and an impedance inverter (e.g., a quarter-wavelength transmission line). Extending the bandwidth of a DPA has been extensively investigated, and various techniques have been proposed.

[0006] In "Enhancing Bandwidth and Back-Off Range of Doherty Power Amplifier with Modified Load Modulation Network," published by Yang Xu et al. in IEEE Transactions on Microwave Theory and Techniques, Vol. 69, No. 4, pp. 2291-2303, April 2021, a DPA was proposed in which the impedance inverter consists of three quarter-wavelength transmission lines with corresponding characteristic impedances.

[0007] In "A Novel Wideband and Reconfigurable High Average Efficiency Power Amplifier," published by D. Gustafsson et al. at the 2012 IEEE MTT-S Int. International Microwave Symposium Digest conference and proceedings in June 2012, and in "Wideband and Reconfigurable Doherty-Based Amplifier," published in 2017, EP 2 705 601 B1, a modified DPA was proposed in which the characteristic impedance of the quarter-wavelength transmission line is equal to the load impedance and equal to the impedance of the main amplifier in the low-power region (i.e., when the auxiliary amplifier is turned off). Therefore, the output impedance of the main amplifier is matched and frequency-independent. By tuning the DC supply voltage of the main amplifier, the peak PAE at power back-off is reconfigurable from less than 6 dB up to 10 dB of OPBO.

[0008] In “High-efficiency amplifier” US Pat. No. 6,922,102 B2 by RE Mayer et al., it is proposed to use a quadrature coupler in a DPA to improve the efficiency of the DPA at a back-off power level.

[0009] In "New output combiner for Doherty amplifiers," published in IEEE Microwave and Wireless Components Letters, Vol. 23, No. 1, pp. 31-33, January 2013, R. Giofre et al. discuss how quadrature couplers can be used to extend the bandwidth of DPAs. The quadrature coupler used here consists of four transmission lines, with the isolation ports of the quadrature coupler left open.

[0010] In "Wideband Doherty Power Amplifier in Quasi-Balanced Configuration" presented at the 20th IEEE Wireless and Microwave Technology Conference (WAMICON) in 2019, Y. Cao et al. proposed another quadrature coupler DPA, in which the isolation port of the quadrature coupler is grounded.

[0011] In “Linearity-enhanced quasi-balanced Doherty power amplifier with mismatch resilience through series / parallel reconfiguration for massive MIMO,” published in IEEE Transactions on Microwave Theory and Techniques, Volume 69, Issue 4, Pages 2319–2335, April 2021, Haifeng Lyu et al. proposed a reconfigurable DPA with tunable loads at isolated ports (open or short).

[0012] However, existing solutions have problems. For example, transmission line (TL)-based DPA has limited bandwidth, even though multi-TL inverters increase the bandwidth to some extent.

[0013] The modified DPA proposed by D. Gustafsson et al. requires a reduced voltage supply for the main amplifier. The reduced voltage supply for the main amplifier results in a reduced maximum power P of the main amplifier. max,main , which in turn gives a low power utilization factor, which is defined as P max,DPA / (P max,main +P max,aux. ), where P max,DPA is the power of DPA, P max,aux. is the power of the auxiliary amplifier.

[0014] Although the quadrature coupler-based DPA has better bandwidth performance than the TL-based DPA, the peak drain efficiency (PDE) is at an OPBO of 6 dB. Drain efficiency (DE) is the ratio of output RF power (Pout) to input DC power (PDC), defined as DE = Pout / PDC. It is not shown whether the quadrature coupler-based DPA is suitable for PDEs with deep OPBO (i.e., greater than 6 dB OPBO).

[0015] DPA based on coupled lines with grounded isolated ports requires a large coupling coefficient, k, to enhance bandwidth. Unfortunately, large k, such as greater than 0.8, is difficult to achieve in gallium nitride (GaN) or gallium arsenide (GaAs) semiconductor processes, where only side-by-side coupled lines with medium k are available. Summary of the Invention

[0016] It is therefore an object of embodiments herein to provide a power amplifier arrangement with improved bandwidth and efficiency at arbitrary power back-off levels.

[0017] Until now, the PAE of a quadrature coupler-based DPA was frequency-dependent in the low-power region because a coupled-line-based quadrature coupler was not used and the load resistance was not equal to the optimal back-off impedance of the main amplifier in the low-power region.

[0018] According to one aspect of the embodiments herein, this object is achieved by a power amplifier arrangement, the power amplifier arrangement being a Doherty power amplifier based on two coupled transmission lines, the power amplifier arrangement comprising a first power amplifier having an input and an output and a second power amplifier having an input and an output, the first power amplifier being a main amplifier and the second power amplifier being an auxiliary amplifier.

[0019] The power amplifier arrangement further comprises an input power splitter having an input and a first output and a second output.

[0020] The power amplifier arrangement further includes an orthogonal coupler having an input port, a through port, a coupled port, and an isolated port. The orthogonal coupler includes two coupled transmission lines, a first terminal of the first transmission line being the input port, a second terminal of the first transmission line being the through port, a first terminal of the second transmission line being the coupled port, and a second terminal of the second transmission line being the isolated port.

[0021] The input of the first power amplifier is coupled to the first output of the input power splitter; the output of the first power amplifier is coupled to the through port of the orthogonal coupler; the input of the second power amplifier is coupled to the second output of the input power splitter; the output of the second power amplifier is coupled to the coupled port of the orthogonal coupler; the input port of the orthogonal coupler is coupled to a load; and the isolated port of the orthogonal coupler is not connected to any component.

[0022] The coupling coefficient of the two coupled transmission lines is determined based on an output power back-off level at which the power amplifier arrangement is desired to operate.

[0023] According to some embodiments herein, a coupling coefficient of two coupled transmission lines may be determined to be equal to a transition point of a voltage drive level of a power amplifier arrangement. The transition point of the voltage drive level is a normalized voltage drive level at which the second power amplifier begins or is about to turn on, and the transition point of the voltage drive level is related to an output power back-off level.

[0024] In other words, the power amplifier arrangement according to the embodiments herein is a Doherty PA based on two coupled transmission lines forming an orthogonal coupler. The main amplifier and the load impedance are respectively connected to the two terminals of the first transmission line. The auxiliary amplifier is connected to one terminal of the second transmission line, and the other terminal is open. The load impedance is equal to the desired or optimal load impedance presented to the main amplifier in the low power region (i.e., when the auxiliary amplifier is turned off). The coupling coefficient of the two coupled transmission lines is selected based on the output power back-off level at which the power amplifier is expected to operate, and the PAE in the low power region is insensitive to frequency, thereby enhancing the bandwidth of the power amplifier arrangement according to the embodiments herein.

[0025] The power amplifier arrangement according to embodiments herein has several advantages:

[0026] Has wider bandwidth than traditional DPA;

[0027] It can have DE peak at any output power back-off level;

[0028] Coupled TLs with moderate coupling coefficients (eg, k≈0.5) are applicable, and such coupled lines can be easily realized in gallium nitride (GaN) or gallium arsenide (GaAs) semiconductor technologies, where only side-by-side coupled lines can be constructed.

[0029] Since the drain supply voltage of the main amplifier is equal to the drain supply voltage of the auxiliary amplifier, the power utilization factor is improved.

[0030] Thus, embodiments herein provide a power amplifier arrangement with improved bandwidth and efficiency at arbitrary power back-off levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Examples of embodiments herein are described in more detail with reference to the accompanying drawings, in which:

[0032] Figure 1 is a schematic block diagram illustrating a power amplifier arrangement according to embodiments herein;

[0033] Figure 2 is a simplified schematic block diagram illustrating a power amplifier arrangement according to embodiments herein;

[0034] Figure 3is a simplified diagram showing simulation results of drain efficiency versus output power at different normalized frequencies for a power amplifier arrangement according to embodiments herein;

[0035] Figure 4 is a simplified diagram showing simulation results of drain efficiency versus output power at different normalized frequencies for a power amplifier arrangement according to embodiments herein;

[0036] Figure 5 is a diagram showing simulation results of a conventional DPA regarding drain efficiency and output power; and

[0037] Figure 6 is a block diagram illustrating an electronic device / apparatus in which embodiments herein may be implemented. DETAILED DESCRIPTION

[0038] Figure 1 1 shows a schematic block diagram of a power amplifier arrangement 100 according to embodiments herein, which is a Doherty power amplifier based on two coupled transmission lines. The power amplifier arrangement 100 comprises a first power amplifier P1 having an input InM and an output OutM as a main amplifier Main in the Doherty power amplifier arrangement 100, and a second power amplifier P2 having an input InA and an output OutA as an auxiliary amplifier Aux. in the Doherty power amplifier arrangement 100.

[0039] The power amplifier arrangement 100 further comprises an input power splitter PS having an input port Pin and two output ports: a first output Out1 and a second output Out2.

[0040] The power amplifier arrangement 100 further includes a quadrature coupler 120 having an input port QC1, a through port QC3, a coupled port QC2, and an isolated port QC4. The quadrature coupler 120 includes two coupled transmission lines TL1 and TL2. A first terminal of the first transmission line TL1 is the input port QC1, and a second terminal of the first transmission line TL1 is the through port QC3. A first terminal of the second transmission line TL2 is the coupled port QC2, and a second terminal of the second transmission line TL2 is the isolated port QC4.

[0041] An input InM of the first power amplifier P1 is coupled to a first output Out1 of the input power splitter PS.

[0042] The output OutM of the first power amplifier P1 is coupled to the through port QC3 of the quadrature coupler 120 .

[0043] An input InA of the second power amplifier P2 is coupled to a second output Out2 of the input power splitter PS.

[0044] The output OutA of the second power amplifier P2 is coupled to the coupling port QC2 of the quadrature coupler 120 .

[0045] The input port QC1 of the quadrature coupler 120 is coupled to the load R L , the load R L Coupled to AC ground gnd.

[0046] The isolation port QC4 of the quadrature coupler 120 is open, ie, not connected to any component.

[0047] According to embodiments herein, the coupling coefficient of the two coupled transmission lines TL1 / TL2 is determined based on an output power back-off level at which the power amplifier arrangement 100 is desired to operate.

[0048] In the low power region (i.e. when the auxiliary amplifier P2 is turned off), the load R L If the characteristic impedances of the coupled lines TL1 and TL2 and the coupling coefficients are selected according to the design equations derived below, the DE of the low power region will be insensitive to frequency and thus the bandwidth of the power amplifier arrangement 100 will be enhanced.

[0049] In the following, the design equations will be derived and reference will be made to Figure 2 It is described how to design the power amplifier arrangement 100 for peak drain efficiency at any arbitrary OPBO level.

[0050] Figure 2 A simplified schematic diagram of a power amplifier arrangement 100 is shown, wherein a quadrature coupler 120 comprising two coupled transmission lines TL1 and TL2 is shown, and the main amplifier P1 and the auxiliary amplifier P2 are represented by voltage-controlled current sources jI3 and I2, respectively, wherein The isolated port (ie, the fourth port QC4) is open circuited, and the input port (ie, the first port QC1) is connected to the load impedance / resistance R L In a first order approximation, the parasitics of the transistors are neglected.

[0051] The length of the two coupled transmission lines TL1 , TL2 may be a quarter wavelength of the center frequency of the RF input signal to the power amplifier arrangement 100 .

[0052] For transverse electromagnetic (TEM) and symmetric transmission lines, the impedance matrix of a 4-port coupled transmission line is given by

[0053]

[0054] Among them, V1, V2, V3, and V4 are the voltages at the four ports, and I1, I2, I3, and I4 are the currents at the four ports, respectively. - =Z 0e -Z 0o And Z + =Z 0e +Z 0o Here, Z 0e and Z 0o are the even-mode and odd-mode impedances of the coupled transmission line, respectively. Z 0e and Z 0o and Z0= Correlation, and the coupling coefficient

[0055]

[0056]

[0057] Even mode and odd mode are the two main modes in which a signal propagates through a pair of coupled transmission lines. Odd mode impedance Z 0o It is defined as the impedance of a single transmission line when two coupled transmission lines are driven differentially with signals of equal amplitude and opposite polarity. Even-mode impedance Z 0e Defined as the impedance of a single transmission line when two coupled transmission lines are driven by common-mode signals of the same amplitude and polarity.

[0058] The fourth port QC4 is open circuit, so I4 = 0. The first port QC1 is connected to the first port QC1 through the resistor R L Termination, so V1 = -R L I1. Substituting these two equations into equation (1), we get

[0059]

[0060] When the auxiliary amplifier is off, I2 = 0 and the impedance at the third port QC3 is therefore given by

[0061]

[0062] When the auxiliary amplifier is off, the impedance Z3 of the main amplifier is equal to where R opt is the optimal load impedance of the main amplifier at full power, that is, the expected load impedance of the first power amplifier P1 at full power. opt The first power amplifier P1 delivers maximum output power. ξ is the normalized voltage drive level, where 0<ξ<1, and ξ bis the transition point of the normalized voltage drive level where the auxiliary amplifier starts or is about to turn on. ξ b and the output power back-off (OPBO) level P given by BO Related

[0063] P BO =-20log(ξ b )

[0064] Therefore, we can get

[0065]

[0066] Furthermore, at peak output power ξ = 1, the impedance of the main amplifier drops to:

[0067] Z3=R opt (6a)

[0068] The maximum current of the auxiliary amplifier is related to the maximum current of the main amplifier and is given by

[0069]

[0070] In equation (6b), -j represents the phase shift between I3 and I2.

[0071] Substituting equations (6a) and (6b) into equation (3) and using equation (5), we obtain

[0072]

[0073] Substituting equation (2) into equations (5) and (7), we obtain

[0074]

[0075] The optimal load impedance R of the main amplifier opt The maximum current of the main amplifier I m,max and the main amplifier supply voltage, ξ b Determined by the OPBO level for a given peak drain efficiency. For a given substrate in a semiconductor technology, the characteristic impedance Z0 of a coupled transmission line is determined by the width and spacing of the coupled transmission lines. For a given substrate in a semiconductor technology, the coupling coefficient k between two coupled transmission lines TL1 / TL2 is primarily determined by their spacing.

[0076] The coupling coefficient k (where k < 1) is a "free" parameter. k can be determined to be equal to ξ b :

[0077] k=ξ b (10)

[0078] In this case, according to equation (8), R L will be equal to It is the impedance of the main amplifier when the auxiliary amplifier is off. At peak output power, the impedance of the auxiliary amplifier is

[0079]

[0080] It is obtained by using equations (3), (6b) and (7).

[0081] The equations derived above describe how at any arbitrary OPBO level, i.e. for any transition point ξ of the voltage drive level b , building a wide-bandwidth PA for peak efficiency.

[0082] For any transition point ξ of the voltage drive level associated with the output power back-off level at which the power amplifier arrangement is desired to operate b , the coupling coefficient k of the two coupled transmission lines TL1 / TL2 can be based on the transition point ξ of the voltage driving level b For example, we can choose k = ξ b , i.e. the coupling coefficient of the two coupled transmission lines TL1 / TL2 can be determined to be equal to the voltage drive level ξ of the power amplifier arrangement 100 b For a given substrate of semiconductor technology, the coupling coefficient of the two coupled transmission lines TL1 / TL2 is mainly determined by their separation distance. Therefore, during the design phase, we can configure the separation distance of the two transmission lines TL1 / TL2 for a given substrate to obtain different coupling coefficients to match different ξ b .

[0083] Then, the optimal load impedance R for the main power amplifier can be determined opt At the optimum load impedance R opt The main power amplifier delivers maximum output power. The optimal load impedance of the main amplifier is R opt The maximum current I0 of the main amplifier, max and the main amplifier supply voltage.

[0084] Based on the optimal load impedance of the first power amplifier P1 and the coupling coefficient of the two coupled transmission lines TL1 / TL2, the characteristic impedance Z0 of the two coupled transmission lines TL1 / TL2 is determined by equation (9):

[0085]

[0086] When determining the maximum current of the main amplifier I m,max and OPBO level (i.e. ξ b ), the maximum current of the auxiliary amplifier I a,maxThe magnitude of is determined by equation (6b):

[0087]

[0088] Assuming that the maximum current is proportional to the device size, the ratio of the sizes of the auxiliary amplifier devices and the main amplifier devices in the power amplifier arrangement 100 can also be determined.

[0089] Based on the optimal load impedance R of the first power amplifier P1 opt The transition point of the voltage driving water when the second amplifier P2 starts or is about to turn on is equal to the transition point of the voltage driving water when the second amplifier P2 starts or is about to turn on. b , the load of the quadrature coupler is determined by the following equation:

[0090]

[0091] In order to demonstrate that the proposed power amplifier arrangement 100 can be used at different transition points ξ corresponding to different voltage drive levels of OPBO b The power amplifier arrangement 100 with the same main amplifier size and current is simulated. All main amplifiers have R = 50Ω and 1A. opt and I m,max , operating at different transition points of the voltage drive level and at different frequencies.

[0092] In order to make DE independent of frequency, k is chosen to be equal to ξ when the auxiliary amplifier is off. b For different transition points ξ equal to 0.4, 0.5 and 0.6 respectively b The relationship between drain efficiency (DE) and output power at different frequencies is Figure 3 The frequency marked in the figure is the normalized frequency f0=f / f c , where f c is the centre frequency. As can be seen, the power amplifier arrangement 100 has two DE peaks, one at the maximum output power and another at the output power back-off level corresponding to the transition point.

[0093] It can be seen that when the output power is less than the OPBO level, that is, when the output power is lower than the transition point, DE is independent of frequency. b =0.6, where Pout<36dBm, for ξ b =0.5, where Pout<35dBm, for ξ b =0.4, where Pout<34dBm, and the DE curves of different frequencies almost overlap with each other.

[0094] The deeper the peak of DE at the back-off power level, i.e., ξ bThe lower or smaller ξ is, the greater the maximum current of the auxiliary amplifier (see equation (6b)), and therefore the greater the maximum output power of the power amplifier arrangement 100. b , the maximum output power decreases as the frequency moves away from the center frequency. b This is not obvious when ξ is equal to 0.5 and 0.6. b =0.4, the maximum output power decreases as the frequency range increases. For example, when the normalized frequency f0 = 0.7 or 1.3, the maximum output power is 39dBm. When the frequency is at the center frequency (i.e. f0 = 1), the maximum output power is 42dBm.

[0095] When b = 0.4, a trade-off can be made between high DE and high output power. Figure 4 It shows that when k = 0.6, ξ b Figure 2 shows the relationship between DE and output power at different frequencies when k = 0.4. As can be seen, compared with k = 0.4, when k is increased from 0.4 to 0.6, at a normalized frequency equal to 1.3 or 0.7, the maximum output power decreases by approximately 1 dB from 42 dBm to 41 dBm, while the DE peak degrades from 76% to 61%.

[0096] However, the DE of the proposed power amplifier arrangement 100 is better than that of the conventional DPA where a quarter-wavelength TL replaces the quadrature coupler. b = 0.4, the relationship between DE and the output power of traditional DPA is Figure 5 As can be seen, the peak DE drops to 37% at a normalized frequency equal to 1.3 or 0.7, compared to 61% for the proposed power amplifier arrangement 100.

[0097] Thus, it has been demonstrated that the power amplifier arrangement 100 according to embodiments herein has several advantages:

[0098] Has wider bandwidth than traditional DPA;

[0099] It can have DE peak at any output power back-off level;

[0100] Coupled TLs with moderate coupling coefficients (eg, k≈0.5) are applicable, and such coupled lines can be easily realized in gallium nitride (GaN) or gallium arsenide (GaAs) semiconductor technologies, where only side-by-side coupled lines can be constructed.

[0101] Since the drain supply voltage of the main amplifier is equal to the drain supply voltage of the auxiliary amplifier, the power utilization factor is improved.

[0102] In summary, the power amplifier arrangement 100 according to the embodiments herein is a quadrature coupler-based DPA that can be designed to have an efficiency peak at any OPBO level. The quadrature coupler 120 can be implemented by two coupled transmission lines TL1 / TL2 having a length of a quarter wavelength at the center frequency of the RF signal. The isolation port of the quadrature coupler is open-circuited. The coupling coefficient k of the two coupled transmission lines TL1 / TL2 is determined based on the output power back-off level at which the power amplifier arrangement 100 is expected to operate. The coupling coefficient k can be equal to the transition point ξ of the voltage drive level of the power amplifier arrangement 100. b The characteristic impedance Z0 of the coupled transmission line TL1 / TL2 is determined by the optimal impedance of the main amplifier and the coupling coefficient k of the two coupled transmission lines TL1 / TL2. The load impedance R at the first port QC1 of the orthogonal coupler 120 is L The transition point ξ is determined by the optimum impedance and voltage drive level of the main amplifier. b Sure.

[0103] The power amplifier arrangement 100 according to embodiments herein may be used in various electronic devices or apparatuses or the like. Figure 6 A block diagram of an electronic device or apparatus 600 is shown. The electronic device or apparatus 600 includes a power amplifier arrangement 100 according to embodiments herein. The electronic device 600 may be a transmitter, a transceiver, a base station, a mobile device, a user equipment, a wireless communication device, or a radar for a communication system. The electronic device 600 may include other units, including a memory 620 and a processing unit 630.

[0104] The embodiments herein are not limited to the preferred embodiments described above. Various alternatives, modifications, and equivalents may be used. Those skilled in the art will appreciate that the power amplifier arrangement 100 according to the embodiments herein may be implemented in a printed circuit board having discrete transistors or any semiconductor technology (e.g., bipolar N-type metal oxide semiconductor (NMOS), P-type metal oxide semiconductor (PMOS), complementary metal oxide semiconductor (CMOS), silicon on insulator (SOI) CMOS, field effect transistor (FET), MOSFET technology, etc.).

[0105] When the word “comprise” or “comprising” is used, it should be interpreted as non-limiting, meaning “consisting at least of…” Therefore, the above embodiments should not be taken as limiting the scope of the present invention, which is defined by the appended claims.

Claims

1. A power amplifier arrangement (100), wherein: The power amplifier arrangement (100) is a Doherty power amplifier based on two coupled transmission lines, the power amplifier arrangement (100) comprising: a first power amplifier (P1) having an input (InM) and an output (OutM) as a main amplifier, and a second power amplifier (P2) having an input (InA) and an output (OutA) as an auxiliary amplifier; an input power splitter (PS) having an input (Pin) and a first output (Out1) and a second output (Out2); A quadrature coupler (120) having an input port (QC1), a through port (QC3), a coupled port (QC2), and an isolated port (QC4), wherein the quadrature coupler (120) comprises two coupled transmission lines (TL1 / TL2), a first terminal of a first transmission line (TL1) being the input port (QC1), a second terminal of the first transmission line (TL1) being the through port (QC3), a first terminal of a second transmission line (TL2) being the coupled port (QC2), and a second terminal of the second transmission line (TL2) being the isolated port (QC4); and wherein The input (InM) of the first power amplifier (P1) is coupled to the first output (Out1) of the input power splitter (PS); The output (OutM) of the first power amplifier (P1) is coupled to the through port (QC3) of the quadrature coupler (120); The input (InA) of the second power amplifier (P2) is coupled to the second output (Out2) of the input power splitter (PS); The output (OutA) of the second power amplifier (P2) is coupled to the coupling port (QC2) of the quadrature coupler (120); The input port (QC1) of the quadrature coupler (120) is coupled to a load (R L );as well as The isolated port (QC4) of the quadrature coupler (120) is not connected to any component; and wherein The coupling coefficient of the two coupled transmission lines (TL1 / TL2) is determined based on an output power back-off level at which the power amplifier arrangement (100) is desired to operate.

2. The power amplifier arrangement (100) according to claim 1, wherein The coupling coefficient of the two coupled transmission lines (TL1 / TL2) is determined to be equal to the transition point (ξ) of the voltage drive level of the power amplifier arrangement (100). b ), and wherein the transition point (ξ b ) is the voltage drive level at which the second amplifier (P2) starts and is related to the output power back-off level.

3. The power amplifier arrangement (100) according to any one of claims 1-2, wherein For a given substrate, the coupling coefficient of the two coupled transmission lines (TL1 / TL2) is determined by their separation distance.

4. The power amplifier arrangement (100) according to any one of claims 1 to 3, wherein The characteristic impedances of the two coupled transmission lines (TL1 / TL2) are determined based on an optimal load impedance of the first power amplifier (P1) and the coupling coefficient of the two coupled transmission lines (TL1 / TL2), wherein the first power amplifier (P1) delivers maximum output power under the optimal load impedance.

5. The power amplifier arrangement (100) according to claim 4, wherein The characteristic impedance of the two coupled transmission lines (TL1 / TL2) is given by the equation Determine, where Z0 is the characteristic impedance of the coupled transmission line, R opt is the optimal load impedance of the first power amplifier (P1), and k is the coupling coefficient of the two coupled transmission lines (TL1 / TL2).

6. The power amplifier arrangement (100) according to any one of claims 1 to 5, wherein The load impedance of the quadrature coupler (120) is determined based on the optimal load impedance of the first power amplifier (P1) and the output power back-off level.

7. The power amplifier arrangement (100) according to claim 6, wherein The load impedance of the quadrature coupler is given by the equation Determine, where R L is the load impedance, R opt is the optimal load impedance of the first power amplifier (P1), ξ b represents the voltage driving level when the second amplifier (P2) starts, the ξ b By equation P BO =-20log(ξ b ) is related to the output power back-off level, where P BO is the output power back-off level.

8. An electronic device (600) comprising a power amplifier arrangement (100) according to any one of claims 1-7.

9. The electronic device (600) according to claim 8 is any one of a transmitter, a transceiver, a base station, a mobile device, a user equipment, and a wireless communication device for a communication system.

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