Power synthesis balun and power amplifier circuit

Abstract

The invention provides a power synthesis balun and a power amplifier circuit. The balun comprises at least two differential signal input ends, a single-ended signal output end, a plurality of coupling transmission lines, an adjustable coupling ground structure and a direct current bias circuit. The coupling transmission line comprises a differential end transmission line connected with the differential signal input end and a single-end transmission line connected with the single-end signal output end, and the differential end transmission line and the single-end transmission line convert differential signals into single-end signals through electromagnetic coupling; the adjustable coupling ground structure is arranged below the coupling transmission line. And the direct current bias circuit is connected with the differential end transmission line. In-phase superposition is carried out on the current on each single-ended transmission line at the single-ended signal output end, so that current power synthesis of multiple paths of signals is carried out. The distance between the coupling transmission line and the ground can be flexibly adjusted, so that odd-even mode impedance of the Balun is changed in a larger range, and the impedance conversion range is expanded.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of millimeter wave and sub-terahertz integrated circuit, and particularly relates to a power combining balun and power amplifier circuit. BACKGROUND

[0002] In a wireless communication system in a millimeter wave and sub-terahertz frequency band, the application scenario of short-distance and high-data-rate wireless communication and the large free-space path loss require a transmitter system to have a power amplifier with high gain, high output power and high linearity. In order to improve the output power, power combining needs to be performed. The design idea of a coupled-line balun uses an odd-mode and even-mode impedance analysis method to capture the magnetic coupling and electric coupling between two adjacent lines to realize the conversion between balance and unbalance and support wideband impedance matching. At the same time, the power combining between multiple paths can be realized in a voltage or current combining manner to improve the output power. However, the current on-chip coupled-line balun has a limited odd-mode and even-mode impedance adjustment range and low design freedom, which limits the impedance transformation range and makes it difficult to meet the demand of a millimeter wave and sub-terahertz frequency band power amplifier for high gain, high output power and high linearity. SUMMARY

[0003] The present application provides a power combining balun and power amplifier circuit to solve the defect that the current on-chip coupled-line balun has a limited odd-mode and even-mode impedance adjustment range and low design freedom, which makes it difficult to meet the demand of a millimeter wave and sub-terahertz frequency band power amplifier for high gain, high output power and high linearity. The technical solution provided by the present application is as follows: In a first aspect, the present application provides a power combining balun, comprising: at least two differential signal input terminals for receiving differential signals; a single-ended signal output terminal for outputting a combined single-ended signal; a plurality of coupled transmission lines, the coupled transmission lines comprising differential-end transmission lines connected to the differential signal input terminals and single-ended transmission lines connected to the single-ended signal output terminal, the differential-end transmission lines and the single-ended transmission lines being connected through electromagnetic coupling to convert the differential signals into single-ended signals; an adjustable coupled ground structure arranged below the coupled transmission lines for adjusting the odd-mode impedance and the even-mode impedance of the power combining balun by adjusting the relative position of the adjustable coupled ground structure and the coupled transmission lines; a direct current biasing circuit connected to the differential-end transmission lines; wherein the currents on the single-ended transmission lines are superimposed in phase at the single-ended signal output terminal to perform current power combining of multiple signals.

[0004] Optionally, the adjustable coupled ground structure comprises one or more bottom coupled ground conductors arranged on different metal layers.

[0005] Optionally, the DC bias circuit comprises a DC blocking capacitor connected between the DC bias terminal and the ground.

[0006] Optionally, the DC bias circuit further comprises: edge DC bias ports respectively corresponding to each differential transmission line; a center DC bias port corresponding to the power combining terminal of each differential transmission line; the DC blocking capacitor is connected between the edge DC bias port and the center DC bias port and the ground.

[0007] Optionally, the electrical length of the differential transmission line and the single-ended transmission line is less than one quarter of the wavelength of the operating frequency.

[0008] Optionally, the relative arrangement of the differential transmission line and the single-ended transmission line is any of the following: vertical coupling, arranged on different metal layers; horizontal coupling, arranged on the same metal layer; side coupling, arranged on different metal layers with horizontal offset.

[0009] Optionally, when the differential transmission line and the single-ended transmission line are arranged in a horizontal coupling manner, the coupling strength is adjusted by adjusting the horizontal spacing d between the differential transmission line and the single-ended transmission line.

[0010] Optionally, further comprising a connection transmission line, the multiple single-ended transmission lines are connected to one end of the connection transmission line after being merged, and the other end of the connection transmission line is connected to the single-ended signal output terminal.

[0011] Optionally, the number of differential signal input terminals is two, and the input signals of the two differential signal input terminals have the same phase.

[0012] In a second aspect, the present application further provides a power amplifier circuit, comprising: a plurality of power amplifier units; the power combining balun as described in the first aspect; wherein the differential output terminals of the plurality of power amplifier units are connected to the at least two signal input ports of the power combining balun one by one, and the DC bias circuit of the power combining balun is used to provide DC bias for the plurality of power amplifier units. The application provides a power combining balun, which constructs a multi-path parallel distributed architecture as a core architecture for realizing power combination and signal conversion.

[0013] Other features and advantages of the present application will be set forth in the descriptions that follow and in part will be apparent from the description or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the description and the drawings.

[0014] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically described with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0016] Figure 1is an equivalent model diagram of the power combining balun provided by the application.

[0017] Figure 2 is a structure top view of the power combining balun provided by the application.

[0018] Figure 3 is a structure side view of the power combining balun provided by the application.

[0019] Figure 4 is a vertical coupling schematic diagram of the differential end transmission line and the single end transmission line provided by the application.

[0020] Figure 5 is an enlarged structure diagram of the power combining balun provided by the application.

[0021] Figure 6 is an equivalent model diagram of the power amplifier circuit provided by the application.

[0022] Figure 7 is a structure top view of the power amplifier circuit provided by the application.

[0023] Reference signs: 100, coupling transmission line; 101, differential end transmission line; 102, single end transmission line; 103, bottom layer coupling ground conductor; 104, connecting transmission line; 201, first differential input port; 202, second differential input port; 203, single end signal output end; 204, edge DC bias port; 205, center DC bias port; 301, DC blocking capacitor. DETAILED DESCRIPTION

[0024] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be clearly and completely described below with reference to the drawings in the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0025] The present application provides a power combining balun, which is a highly integrated passive network realizing four functions of power combining, balanced conversion, impedance matching and DC feeding in the millimeter wave / sub-terahertz frequency band. In the form of current power combining, the functions of DC bias application, power combining, differential signal to single end signal conversion and wideband impedance matching can be realized at the same time. Referring to Figure 1 and Figure 2 As shown in the drawings, the power combining balun comprises at least two differential signal input ends (such as Figure 1The application comprises at least two differential signal input ends (201, 202), one single-end signal output end 203, a plurality of coupling transmission lines 100, an adjustable coupling ground structure and a direct current bias circuit.

[0026] The at least two differential signal input ends are used for receiving differential signals and are connected to the differential output ends of two or more power amplifier units. These input ends are designed to be symmetrically distributed to ensure that each signal has the same amplitude and phase.

[0027] The coupling transmission line 100 comprises differential end transmission lines 101 connected to the differential signal input ends and single-end transmission lines 102 connected to the single-end signal output end 203. The coupling transmission line 100 specifically comprises two end lines (i.e. two differential end transmission lines 101) of a differential signal and a single-end transmission line 102 located between them. Specifically, a differential signal (containing a positive and a negative signal component with opposite phases) is input from the two differential end transmission lines 101. Due to the symmetry of the structure, the positive and negative components of the differential signal will simultaneously undergo electromagnetic coupling with the single-end transmission line 102 in the middle. On the single-end transmission line 102, the currents induced by the positive and negative signal components have the same phase, so they will directly superimpose in phase in the single-end transmission line 102, thereby converting and combining into a single-end signal.

[0028] The single-end signal output end 203 is used for outputting the combined single-end signal. One end of each single-end transmission line 102 is short-circuited to ground, and the other end is connected to the single-end signal output end 203. The currents of the single-end transmission lines 102 flow to the single-end signal output end 203 and superimpose in phase to perform current power combination of multiple signals. Due to the input signal being in phase and the structure being symmetrical, the currents induced on the single-end transmission lines 102 of each path are also in phase. These in-phase currents superimpose in phase at the single-end signal output end 203, thereby realizing current power combination and improving the total output power.

[0029] The adjustable coupling ground structure is arranged below the coupling transmission line 100, and is used to adjust the odd-mode impedance and the even-mode impedance of the power combining balun by adjusting the relative position of the adjustable coupling ground structure and the coupling transmission line 100. The adjustable coupling ground structure is an active impedance adjustment component rather than a simple reference ground. The adjustable coupling ground structure and the coupling transmission line 100 above the adjustable coupling ground structure form a new and adjustable coupling channel. By adjusting the vertical distance between the adjustable coupling ground structure and the coupling transmission line 100 or the design (such as the width and shape) of the adjustable coupling ground structure, the electromagnetic environment formed by the differential-end transmission line 101, the single-end transmission line 102 and the adjustable coupling ground structure can be changed. This change directly reflects a wide range and flexible change of the odd-mode impedance and the even-mode impedance, and a wider range of impedance transformation ratios can be achieved, so that the extremely low optimal output impedance (Zopt, usually several ohms) of the sub-terahertz power amplifier can be efficiently matched, and the power transmission efficiency is improved.

[0030] The direct current bias circuit is connected with the differential-end transmission line 101, and is used to provide a direct current bias voltage for a power amplifier transistor connected therewith. The direct current bias circuit uses the differential-end transmission line 101 of the balun itself to deliver a direct current, without the need of an additional dedicated line that may destroy symmetry and introduce parasitic effects. The design of the direct current bias circuit ensures that the injection point of the direct current bias presents a radio frequency ground to a radio frequency signal, so as to ensure that the injection of the direct current bias does not interfere with the integrity of the radio frequency signal. This design provides a symmetric, stable and low-loss direct current bias for multiple power amplifier units, and ensures that all the power amplifier units can work cooperatively and linearly, and high linearity output is achieved.

[0031] The power combining balun provided by the application constructs a multi-path parallel distributed architecture as a core architecture for realizing power combining and signal conversion. The architecture contains at least two differential signal input ends, and each signal is converted from balanced to unbalanced through electromagnetic coupling between the differential end transmission line 101 and the single-end transmission line 102. The currents of each single-end transmission line 102 are finally superimposed in phase at the single-end signal output end 203, thereby efficiently combining the output powers of multiple power amplifier units, significantly improving the total output power while maintaining the inherent high gain characteristics of the power amplifier units. The application also innovatively introduces an adjustable coupling ground structure under the coupling line structure, with high design freedom. The structure is not a passive ground layer, but an active impedance control component. By adjusting the relative position of the differential end transmission line 101 and the single-end transmission line 102 above it, the odd-mode and even-mode impedances can be flexibly changed in a wide range, expanding the impedance transformation range, thereby realizing efficient and wide-range impedance matching for each signal path in the distributed architecture. This design can efficiently transform the extremely low optimal output impedance (Zopt) of the power amplifier unit to the standard load impedance (such as 50Ω), minimize matching loss, significantly improve power conversion efficiency, and provide a good impedance environment for the high gain performance of the power amplifier unit. The application also seamlessly integrates the direct current bias circuit into the above-mentioned distributed architecture. The circuit is directly connected to the differential end transmission line 101, and uses the differential end transmission line 101 in the distributed architecture to supply direct current bias to multiple power amplifier units in the distributed architecture, ensuring that the injection of direct current bias does not interfere with the integrity of the radio frequency signal, thereby providing symmetric, stable and low-loss direct current bias for all power amplifier units, ensuring that each power amplifier unit operates in the optimal linear region, and finally realizing high linearity output while ensuring the high gain characteristics of each power amplifier unit.

[0032] In an alternative embodiment, with reference to Figure 3As shown, the adjustable ground coupling structure includes one or more bottom layer coupling ground conductors 103 arranged in different metal layers. By adjusting the electromagnetic coupling degree between the coupling ground conductors and the coupling transmission line 100, the odd mode impedance and the even mode impedance of the power combining balun are flexibly regulated. The adjustment of the structure includes vertical dimension regulation and horizontal dimension regulation. The vertical dimension regulation refers to controlling the vertical distance between the bottom layer coupling ground conductor 103 and the upper coupling transmission line 100 by selecting the metal layer in which the bottom layer coupling ground conductor 103 is arranged. According to the principle of capacitive coupling, the vertical distance determines the coupling strength; the decrease of the vertical distance increases the capacitive coupling and the influence on the odd / even mode impedance. The horizontal dimension regulation is achieved by designing the two-dimensional shape and size of the bottom layer coupling ground conductor 103, including adjusting the width, length and hollow pattern thereof. Different shapes of the conductors affect the edge field distribution and then modulate the electromagnetic field. By comprehensively optimizing the vertical position and horizontal pattern of the bottom layer coupling ground conductor 103, fine and wide range regulation of the electromagnetic environment in three-dimensional space is achieved, so as to realize accurate control of the odd / even mode impedance.

[0033] By introducing the bottom layer coupling ground conductor 103, the present application expands the impedance adjustment from the two-dimensional design limited to the width and spacing of the coupling line to the three-dimensional design of optimizing the coupling line itself and the coupling ground structure below, significantly improves the design flexibility, and can realize extremely low or extremely high odd / even mode impedance values that cannot be achieved by traditional structures, thereby providing conditions for matching extreme impedance. The impedance transformation ratio is determined by the odd / even mode impedance, and the expansion of the range of the odd / even mode impedance directly expands the range of the impedance transformation ratio, so that the balun can efficiently transform the optimal output impedance of the sub-terahertz power amplifier to the standard load impedance, and the improvement of the matching efficiency translates into higher output power.

[0034] In an optional embodiment, the direct current bias circuit includes a direct current blocking capacitor 301 connected between the direct current bias end and the ground. The direct current bias circuit is connected with the differential end transmission line 101, and the direct current bias ends of the differential end transmission line 101 are connected to the ground through the direct current blocking capacitor 301, so as to realize the ground short circuit of the radio frequency signal. The direct current bias and the radio frequency signal share the same physical transmission line structure (i.e. the differential end transmission line 101). The direct current blocking capacitor 301 provides a low impedance path to the ground for the radio frequency signal, while preventing the direct current component from leaking to the ground potential, thereby realizing effective isolation of the direct current bias and the radio frequency signal. Specifically, the direct current bias voltage is applied to the direct current bias end (such as the direct current bias end 102) through the direct current blocking capacitor 301, and the radio frequency signal is applied to the differential end transmission line 101 through the direct current bias end (such as the direct current bias end 102). The direct current bias voltage and the radio frequency signal are isolated from each other. Figure 1The DC bias circuit injects a DC current to the power amplifier transistor through the differential end transmission line 101 to establish a static working point for the power amplifier transistor. The DC blocking capacitor 301 is connected between the DC bias end and the ground, which functions to isolate the RF and DC. In the DC frequency band, the DC blocking capacitor 301 presents high impedance (open circuit) to effectively prevent the DC bias current from leaking to the ground potential, thereby stably applying the DC voltage to the transistor. In the RF frequency band, the DC blocking capacitor 301 presents low impedance (short circuit) to provide a low-impedance return path for the RF signal to the ground, thereby preventing the RF signal from leaking to the DC power supply and ensuring the integrity of the RF signal.

[0035] The DC bias circuit of the present application realizes the isolation between the RF path and the DC bias through the DC blocking capacitor 301, ensures the integrity of the RF signal transmission, and avoids the interference of the DC component on the RF performance. The integrated design utilizes the differential end transmission line 101 to deliver the DC bias, eliminates the parasitic parameters and asymmetry introduced by the additional feeding wires, provides symmetrical and low-loss DC bias for the multiple power amplifier units, ensures the cooperative work of the power amplifier units, and improves the linearity of the power amplifier units. The DC blocking capacitor 301 provides a low-impedance grounding path for the RF signal, effectively suppresses the potential oscillation mode, and enhances the working stability of the power combining balun and the power amplifier units connected thereto.

[0036] In an optional embodiment, the DC bias circuit further includes an edge DC bias port 204 and a center DC bias port 205. The edge DC bias port 204 is respectively arranged for each differential end transmission line 101 to provide independent DC bias current for each differential end transmission line 101. The center DC bias port 205 is arranged for the power combining end of each differential end transmission line 101. The DC blocking capacitor 301 is connected between the edge DC bias port 204 and the center DC bias port 205 and the ground to form a RF short-circuit path to the ground.

[0037] The coupling line balun currently applied in integrated circuit design is mostly analyzed by coupling line theory and realized in the form of transformer. The transformer form of coupling line balun is beneficial to direct current biasing, but the two ends of the coupling line are connected to each other in short circuit, resulting in the asymmetry of the active path in multi-path synthesis. In the present application, one end of the differential-end transmission line 101 is open circuit, and the other end is the power synthesis end; one end of the single-end transmission line 102 is short circuit to ground, and the other end is connected to the single-end signal output end 203. Such boundary conditions of one end open circuit and one end short circuit, or one end short circuit and one end connected to the output, provide a physical basis for designing a highly symmetrical signal path, and fundamentally avoid the inherent asymmetry brought by the traditional transformer structure. On this basis, the present application designs the edge direct current biasing port 204 corresponding to each differential-end transmission line 101, and the center direct current biasing port 205 corresponding to the power synthesis end. The edge direct current biasing port 204 provides independent and symmetrical direct current biasing injection points for each power amplifier unit, and the center direct current biasing port 205 provides supplementary biasing for the common node of the power synthesis end. Such multi-node collaborative biasing design ensures that the direct current path to each power amplifier transistor has high symmetry, thereby ensuring the consistency of the static working point of each power amplifier unit, completely solving the problem of performance mismatch of the active path caused by asymmetric power supply, and also suppressing the common-mode oscillation problem caused by asymmetry during multi-path power synthesis.

[0038] In an optional embodiment, the electrical length of the differential-end transmission line 101 and the single-end transmission line 102 is less than one quarter of the wavelength of the working frequency. The reduction of the electrical length directly reduces the physical size of the transmission line on the chip, significantly reduces the layout area, and is beneficial to the design of high-integration compact circuits. At the same time, the shorter transmission line structure effectively reduces its inherent parasitic resistance, parasitic inductance and parasitic capacitance between the substrate, thereby reducing the loss of the passive device itself and helping to improve the power synthesis efficiency.

[0039] The traditional quarter-wave transmission line usually only presents the best performance near the center frequency, so its working bandwidth is narrow. The transmission line with an electrical length significantly less than one quarter of the wavelength used in the present application has reduced sensitivity of phase response to frequency, so that the amplitude balance and phase balance of the balun can be maintained in a wider frequency band, thereby effectively expanding the working bandwidth of the power synthesis balun and supporting wideband and high-data-rate communication applications.

[0040] In an optional embodiment, the relative arrangement of the differential-end transmission line 101 and the single-end transmission line 102 is any of the following: In vertical coupling, the two components are placed on different metal layers, such as the top and bottom layers, or adjacent metal layers in a vertical direction. Signals are coupled through the interlayer dielectric, and the coupling strength is determined by the dielectric thickness, dielectric constant, and transmission line spacing. For a specific arrangement, refer to... Figure 4 As shown, the differential transmission line 101 is on the top layer, and the single-ended transmission line 102 is on the bottom layer. Vertical coupling isolates the differential transmission line 101 and the single-ended transmission line 102 through a dielectric, reducing direct electromagnetic coupling. Simultaneously, the differential transmission line 101 itself, due to its symmetry, can suppress common-mode noise, further reducing interference to the single-ended transmission line 102. In the vertical coupling configuration, the widths of the differential transmission line 101 and the single-ended transmission line 102 need to be adjusted according to the impedance transformation requirements.

[0041] In the horizontal coupling method, both differential transmission lines are arranged on the same metal layer, and coupling is achieved by adjusting the line spacing. The differential transmission line 101 can adopt an edge-coupled or wide-side-coupled structure, while the single-ended transmission line 102 is arranged parallel to one side or in the middle of the differential transmission line 101. As a specific arrangement, the differential transmission line 101 is on the left, and the single-ended transmission line 102 is on the right. In the horizontal coupling configuration, the widths of the differential transmission line 101 and the single-ended transmission line 102, as well as the horizontal spacing between them, need to be adjusted according to the impedance transformation requirements.

[0042] In the side-coupling method, the two transmission lines are arranged on different metal layers and are horizontally offset. The differential transmission line 101 is located on the upper layer, and the single-ended transmission line 102 is located on the lower layer and offset by a certain distance (e.g., the offset is 50% of the line width), forming oblique coupling. Side coupling, combined with vertical isolation and horizontal offset, allows for more flexible adjustment of the impedance transformation range of the balun. In the side-coupling form, the horizontal spacing between the differential transmission line and the single-ended transmission line 102 can be adjusted according to the impedance transformation requirements.

[0043] In an optional embodiment, when the differential transmission line 101 and the single-ended transmission line 102 are horizontally coupled, the coupling strength is adjusted by changing the horizontal spacing d between them. A smaller horizontal spacing d enhances the interaction between the electric and magnetic fields between the transmission lines, increasing the coupling coefficient; a larger horizontal spacing d weakens the field interaction, decreasing the coupling coefficient. This method achieves linear and continuous control of the coupling characteristics by changing a single physical parameter, without requiring changes to the metal layer or dielectric material, offering high design flexibility and process compatibility.

[0044] By adjusting the horizontal spacing d, the coupling coefficient can be changed in a large range, thus providing the desired odd and even mode impedance values. This direct regulation mechanism overcomes the limitation of fixed coupling strength in traditional fixed spacing design, and improves the degree of freedom of impedance matching design. Stronger coupling strength helps to expand the operating bandwidth of the balun. By optimizing the horizontal spacing d, a flat coupling frequency response can be obtained, thus maintaining a stable impedance transformation ratio in a wide frequency band, supporting the operation of wideband signals. The horizontal coupling structure does not require vertical vias or cross-layer connections, maintaining the low-loss characteristics of the transmission line structure, while facilitating the miniaturization and compactness of chip layout. This horizontal coupling method regulates the coupling characteristics through a single geometric parameter, while considering the process friendliness and low-loss requirements, and is suitable for millimeter wave integrated circuit applications sensitive to size, loss and cost.

[0045] In an optional embodiment, referring to Figure 1 The power combining balun further includes a connecting transmission line 104, the multi-path single-ended transmission line 102 is connected to one end of the connecting transmission line 104 after merging, and the other end of the connecting transmission line 104 is connected to the single-ended signal output end 203 for adjusting the imaginary part of the output impedance to achieve impedance matching. The connecting transmission line 104 is a transmission line segment with precisely designed characteristic impedance and electrical length. One end is connected to the center connection point of the multi-path single-ended transmission line 102, and the other end constitutes the single-ended signal output end 203 of the entire balun. The connecting transmission line 104 and the single-ended transmission line 102 are located in the same metal layer, and the parameters such as characteristic impedance, length and width are optimized according to the requirements of the overall matching network.

[0046] The present application introduces a new impedance transformation dimension through the connecting transmission line 104, whose characteristic impedance and electrical length can be used as additional design parameters to finely adjust the impedance value from the combining point to the load, especially to compensate and tune the imaginary part (reactive part) of the impedance. In the millimeter wave frequency band, there are unavoidable parasitic capacitance and inductance at the combining node. The connecting transmission line 104 can cancel the parasitic capacitance through its series inductance effect, or through other tuning methods, finally achieving conjugate impedance matching at the target frequency point, so that maximum power is transmitted to the load. By optimizing the parameters of the connecting transmission line 104, the bandwidth of impedance matching can be widened, so that the power combining balun maintains a low return loss in a wider frequency range, thus improving the operating bandwidth of the entire power amplifier circuit. The connecting transmission line 104 helps to balance the phase of the two signals reaching the output end, ensuring good phase linearity in a wide frequency band.

[0047] The power combining balun provided by the application adopts a Y-shaped structure, is suitable for current power combining of two-way to multi-way active circuits, and simultaneously solves the DC feeding problem of the Y-shaped coupling line balun. Specifically, a plurality of differential-end transmission lines 101 are used as branches, the power combining ends of which are commonly connected to a single-end signal output end 203, forming a Y-shaped main trunk, providing a low-impedance common connection point for multi-way currents, and being an ideal layout for current power combining. When a plurality of differential signals with the same phase and amplitude are input to each differential-end transmission line 101, the same-phase currents are induced on each single-end transmission line 102 through electromagnetic coupling. All the induced currents are connected to the single-end signal output end 203 and are superimposed in the same phase, so as to add the output powers of a plurality of power amplifier units arithmetically, significantly improve the total output power, and naturally support two-way to multi-way expansion.

[0048] In view of the problems of the traditional Y-shaped structure DC feeding, such as the need for external network introduction, easy destruction of symmetry and introduction of loss, the DC bias circuit is directly integrated in the radio frequency structure. The DC bias end is directly applied to the differential-end transmission line 101, and the differential-end transmission line 101 is used as a DC transmission channel to realize physical path sharing of the radio frequency signal and the DC bias. The DC bias end and the ground are connected through a DC blocking capacitor 301, which provides a low impedance at the radio frequency and provides a ground short circuit path for the radio frequency signal, so as to realize effective isolation of the radio frequency and the DC. The DC bias voltage is stably applied to the transmission line to supply power for the transistor, and the radio frequency signal is grounded through the capacitor to prevent leakage to the power supply end, thereby ensuring the normal functions of the balanced conversion and combining. The integrated design directly uses the existing differential-end transmission line 101 as a part of the balun to transport DC, ensures the symmetry of the DC path of each power amplifier unit, avoids additional wiring to introduce parasitic parameters and asymmetry, significantly reduces the DC loss and power supply imbalance risk, and ensures the cooperative linear work of all power amplifier units.

[0049] In an optional embodiment, the number of the differential signal input ends is two, and the input signals of the two differential signal input ends have the same phase.

[0050] Reference Figure 1 , Figure 2 and Figure 3As shown, the power combining balun comprises two completely symmetrical differential signal input ports, i.e. a first differential input port 201 and a second differential input port 202. Each port receives a differential form of radio frequency input signal. The two input signals not only have equal amplitude, but also maintain a strict in-phase relationship. The two signals are respectively connected to two independent electromagnetic coupling pairs composed of differential end transmission lines 101 and corresponding single end transmission lines 102. The two symmetrical differential end transmission lines 101 are open in the middle and are respectively connected to the first differential input port 201 and the second differential input port 202. The middle part of the two single end transmission lines 102 is directly connected, and the current power combining is realized by connecting the transmission line 104 through the terminated single end signal output end 203. The two sides of the two single end transmission lines 102 are respectively shorted to the ground. The edges of the two single end transmission lines 102 are respectively independently grounded, which ensures that the first differential input port 201 and the second differential input port 202 are adjacent on the same side of the coupling line power combining balun. The two electromagnetic coupling pairs are mirror-symmetric in physical layout, which ensures that the electromagnetic paths experienced by the two signals from input to synthesis are completely consistent.

[0051] The two in-phase input signals induce in-phase currents on the single end transmission lines 102 after being converted by the respective differential end transmission lines 101 and single end transmission lines 102. These currents are vectorially superimposed at the single end signal output end 203, realizing the arithmetic addition of power, thereby significantly improving the total output power. The synthesis efficiency directly depends on the phase consistency of the input signal, and the symmetrical physical layout ensures that the synthesis process approaches the theoretical limit. The in-phase characteristics of the input signal combined with the symmetrical layout ensure that the synthesized single end signal has low amplitude imbalance and phase error. Symmetrical and in-phase excitation can effectively suppress odd mode resonance and unnecessary common mode signals in the transmission line, prevent them from causing destructive interference at the synthesis point, and improve the linearity and spurious-free dynamic range of the power combining balun. The two symmetrical and in-phase inputs make the entire balun work in the designed balanced mode, which is beneficial to maintain the optimal odd-even mode impedance ratio, ensure the performance stability of the impedance matching network in a wide frequency band, and reduce energy reflection caused by mismatch. Symmetrical and in-phase input reduces the output power fluctuation caused by phase deviation, reduces the sensitivity of circuit performance to small changes in component parameters and environmental interference, and improves the working reliability.

[0052] Reference Figure 1As shown, the power combining port 205 of the two-way differential transmission line 101 is applied with DC excitation, and the edge DC bias excitation port and the DC blocking capacitor 301 are applied independently to the two sides of the differential transmission line 101. The power combining balun realizes current power combining of the two-way power amplifier (N=2). When the single-ended signal is connected in Ground-Signal-Ground (GSG), the output port impedance RN=N*50=100. When the power amplifier is power combined, the power amplifier output has the optimal output power differential impedance Zopt, so the power combining balun needs to transform Zopt to the 100-ohm single-ended output impedance.C iso The DC blocking capacitor 301 is represented by C dev The equivalent capacitance needed by the power combining balun to match the impedance is represented by C opt The equivalent resistance needed by the power combining balun to match the impedance is represented by R dev and R opt together represent the optimal impedance matching point of the power amplifier.

[0053] Referring to Figure 5 As shown, the width of the differential transmission line 101 of the power combining balun is w d , the width of the single-ended transmission line 102 is w s , the horizontal spacing between the differential transmission line 101 and the single-ended transmission line 102 is d, the differential transmission line 101 and the single-ended transmission line 102 have the same length l, the height of the differential transmission line 101 from the bottom layer of the coupling ground conductor 103 is h d , and the height of the single-ended transmission line 102 from the bottom layer of the coupling ground conductor 103 is h s . The above parameters jointly determine the odd-mode impedance Z 0o and the even-mode impedance Z 0e of the power combining balun, and further determine the impedance transformation ratio of the power combining balun. The output impedance of the single-ended signal output port 203 can be adjusted by connecting the transmission line 104 to the output impedance of the single-ended transmission line 102, so as to finally realize the matching of the output impedance. The electrical length of the differential transmission line 101 and the single-ended transmission line 102 is β×l, where β is the phase constant and l is the physical length of the transmission line. Y 0o and Y 0e represent the odd-mode admittance and the even-mode admittance, respectively, the odd-mode impedance Z 0o =1 / Y 0o , and the even-mode impedance Z 0e =1 / Y 0e .

[0054] The first differential input port 201 and the second differential input port 202 have the same phase. When power synthesis is performed, the first differential input signal is coupled to the corresponding single-ended transmission line 102 through the first differential input port 201, the second differential input signal is coupled to the corresponding single-ended transmission line 102 through the second differential input port 202, and the two signals are superimposed in phase at the single-ended signal output end 203 to perform current power synthesis.

[0055] As a specific embodiment, the application is based on a CMOS process and adopts a side coupling form. The width of the differential transmission line 101 is w d = 18 um, the line width of the single-ended transmission line 102 is w s = 8 um, the horizontal spacing between the differential transmission line 101 and the single-ended transmission line 102 is d = 10 um, and the length of the differential transmission line 101 and the single-ended transmission line 102 is l = 60 um. The differential transmission line 101 and the single-ended transmission line 102 are in different metal layers and are placed on the bottom layer coupling ground conductor 103. The application realizes impedance transformation from the single-path optimal output power differential impedance Zopt = 10 + j14 to the GSG impedance R = 50 after two-path synthesis.

[0056] It should be noted that although the above is described by taking two-path input as an example, those skilled in the art should understand that the power synthesis balun structure described in the application can be naturally extended to multi-path (N > 2). Only the number of differential signal input ends and coupling transmission lines 100 needs to be increased accordingly, and all input signals need to be in phase, so that N-path power synthesis can be realized. The working principle, impedance matching method and direct current feeding structure are consistent with those in the two-path synthesis in the embodiment.

[0057] The power amplifier circuit provided by the application is described below. The power amplifier circuit described below can be referred to in conjunction with the power synthesis balun described above.

[0058] The power amplifier circuit provided by the application, as shown in Figure 6 and Figure 7 , includes a plurality of power amplifier units and a power synthesis balun as described above.

[0059] The plurality of power amplifier units serve as an output network of the circuit, and the differential output ends thereof are connected in one-to-one correspondence with the at least two signal input ports (i.e. 201 and 202 in Figure 6 ) of the power synthesis balun, and the direct current bias circuit of the power synthesis balun is used to provide direct current bias for the plurality of power amplifier units.

[0060] By operating multiple power amplifier units in parallel and combining their output powers in phase in the power combining balun, the total output power of the power amplifier circuit is approximately multiplied, overcoming the bottleneck of limited power handling capability of a single power amplifier unit, and achieving higher output power and power density. The adjustable coupling structure in the power combining balun ensures efficient transformation of the extremely low optimal output impedance (Zopt, usually only a few ohms) of each power amplifier unit to a standard load impedance (such as 50Ω), greatly reducing the energy reflection loss caused by impedance mismatch, thereby significantly improving the power addition efficiency of the power amplifier circuit. The integrated DC bias circuit within the balun provides symmetrical, stable and low-loss DC power supply for all power amplifier units using the differential end transmission line 101 of the balun itself. This design avoids the parasitic effects and power supply imbalance caused by traditional long wire feeding, ensuring that each power amplifier unit operates in the optimal linear region and effectively suppresses gain compression and distortion caused by asymmetric power supply, ensuring high linearity output. The power combining balun, with its wideband characteristics conferred by the coupling line design and adjustable ground structure, enables the power amplifier circuit to maintain good impedance matching and power combining efficiency over a wide frequency range, making it suitable for wideband modulation signals and high data rate transmission systems.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A power combining balun, characterized in that, include: At least two differential signal input terminals are provided for receiving differential signals; A single-ended signal output terminal is used to output the synthesized single-ended signal; Multiple coupled transmission lines, the coupled transmission lines including a differential end transmission line connected to the differential signal input terminal and a single-ended transmission line connected to the single-ended signal output terminal, the differential end transmission line and the single-ended transmission line are electromagnetically coupled to convert the differential signal into a single-ended signal; An adjustable coupling structure is disposed below the coupled transmission line for adjusting the odd-mode impedance and even-mode impedance of the power combining balun by adjusting its relative position to the coupled transmission line; A DC bias circuit is connected to the differential transmission line. The currents on each of the single-ended transmission lines are superimposed in phase at the single-ended signal output terminal to perform current power synthesis of multiple signals.

2. The power combining balun according to claim 1, wherein the adjustable coupling structure comprises one or more bottom coupling conductors disposed on different metal layers.

3. The power combining balun according to claim 1 or 2, characterized in that, The DC bias circuit includes a DC blocking capacitor connected between the DC bias terminal and ground.

4. The power combining balun according to claim 3, characterized in that, The DC bias circuit also includes: Edge DC bias ports are set up corresponding to each differential transmission line; The center DC bias port is set corresponding to the power combining terminal of each differential transmission line; The DC blocking capacitor is connected between the edge DC bias port and the center DC bias port and ground.

5. The power combining balun according to claim 1, characterized in that, The electrical length of the differential transmission line and the single-ended transmission line is less than one-quarter of the wavelength of the operating frequency.

6. The power combining balun according to claim 1, characterized in that, The relative arrangement of the differential transmission line and the single-ended transmission line can be any of the following: Vertical coupling, with both components arranged in different metal layers; The two components are horizontally coupled and arranged on the same metal layer. The two components are arranged in a side-coupled manner, with the two components placed on different metal layers and having a horizontal offset.

7. The power combining balun according to claim 6, characterized in that, When the differential transmission line and the single-ended transmission line are horizontally coupled, the coupling strength is adjusted by adjusting the horizontal spacing between the differential transmission line and the single-ended transmission line.

8. The power combining balun according to claim 1, characterized in that, It also includes a connecting transmission line, where multiple single-ended transmission lines are combined and connected to one end of the connecting transmission line, and the other end of the connecting transmission line is connected to the single-ended signal output terminal.

9. The power combining balun according to claim 1, characterized in that, The differential signal input terminals are two in number, and the input signals of the two differential signal input terminals are in phase.

10. A power amplifier circuit, characterized in that, include: Multiple power amplifier units; The power synthesis balun as described in any one of claims 1 to 9; The differential output terminals of the plurality of power amplifier units are respectively connected to at least two signal input ports of the power combining balun, and the DC bias circuit of the power combining balun is used to provide DC bias to the plurality of power amplifier units.

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