Differential balun circuit, power amplifier and radio frequency chip

Abstract

The utility model relates to the technical field of wireless communication, and provides a differential balun circuit, a power amplifier and a radio frequency chip, which comprise a primary coil, a secondary coil mutually coupled with the primary coil and a control switch network, the first end of the primary coil is used for being connected with an input signal, the second end of the primary coil is grounded, the center tap end of the secondary coil is grounded, the input end of the control switch network is used for being connected with external direct-current voltage, the first output end of the control switch network is connected with the first differential output end of the secondary coil, and the second output end of the control switch network is connected with the second differential output end of the secondary coil. The second output end of the control switch network is connected with the second differential output end of the secondary coil, and the control switch network is used for controlling the inductance value of the secondary coil. According to the differential balun circuit, the function of adjusting parameters such as the conversion ratio of the balun can be realized under the condition that the Q value is not sacrificed.

Description

Technical Field

[0001] The utility model relates to the technical field of wireless communications, and in particular to a differential balun circuit, a power amplifier and a radio frequency chip. Background Art

[0002] The continuous advancement of communication technology, especially the rapid development of 5G in recent years, has brought people a brand new communication experience. However, the RF transceiver at the core of communication systems faces even more severe performance challenges. As the most energy-consuming module in the transmitter, the performance of the power amplifier is crucial to the entire RF transmitter system. Communication systems are placing increasingly stringent demands on power amplifiers. Currently, 5G communication systems widely utilize more complex modulation technologies to achieve faster and more efficient data transmission. Driven by this demand, power amplifier performance, such as efficiency, linearity, and bandwidth, has faced greater challenges. How to simultaneously meet the requirements of high efficiency and high linearity over a wider frequency range has become a hot topic in current power amplifier research.

[0003] In existing applications, differential power amplifiers are often used to achieve better linearity at higher power levels. The balun, a common component in differential structures, plays a crucial role in the overall performance of the power amplifier. A commonly used balun structure includes a primary coil, a secondary coil coupled to the primary coil, and two LC resonant circuits, each connected to the two output terminals of the secondary coil. The primary coil is single-ended, while the secondary coil is differential. A balun is used to transmit and match single-ended signals between the two stages. To improve power amplifier performance, a second-order resonant network is often added to the two differential input ports to suppress second-order harmonics. However, the balun is often implemented using stripline or microstrip lines, and once the size is determined, it cannot be adjusted. Furthermore, the second-order resonant network often affects the performance of the fundamental small signal, resulting in problems such as gain reduction in the low-power region. Utility Model Content

[0004] In view of the above deficiencies in the prior art, the present invention proposes a differential balun circuit to solve the problems of difficult parameter adjustment and gain reduction in the prior differential balun.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] An embodiment of the present invention provides a differential balun circuit, comprising a primary coil, a secondary coil coupled to the primary coil, and a control switch network; the first end of the primary coil is used to connect to an input signal, the second end of the primary coil is grounded, the middle tap end of the secondary coil is grounded, the input end of the control switch network is used to connect to an external DC voltage, the first output end of the control switch network is connected to the first differential output end of the secondary coil, the second output end of the control switch network is connected to the second differential output end of the secondary coil, and the control switch network is used to control the inductance value of the secondary coil.

[0007] Preferably, the control switch network includes a first capacitor, a first inductor and a first diode;

[0008] The first end of the first capacitor is connected to the first end of the first inductor and serves as the input end of the control switch network; the second end of the first capacitor is grounded, the second end of the first inductor is connected to the cathode of the first diode and serves as the second output end of the control switch network, and the anode of the first diode serves as the first output end of the control switch network.

[0009] Preferably, the differential balun circuit further includes a capacitor unit, a first end of the capacitor unit is connected to the middle tap end of the secondary coil, and the middle tap end of the secondary coil is connected to ground after being connected in series with the capacitor unit.

[0010] Preferably, the secondary coil includes a first coil and a second coil, and the capacitor unit includes a second capacitor and a third capacitor;

[0011] The first end of the first coil serves as the first differential output end of the secondary coil, the second end of the first coil is connected to the first end of the second capacitor, and the second end of the second capacitor is grounded;

[0012] The first end of the second coil serves as the second differential output end of the secondary coil, the second end of the second coil is connected to the first end of the third capacitor, and the second end of the third capacitor is grounded; the second end of the first coil and the second end of the second coil together serve as the middle tap end of the secondary coil.

[0013] Preferably, the second capacitor and the third capacitor are both adjustable capacitors.

[0014] Preferably, the capacitor unit includes a fourth capacitor, a first end of the fourth capacitor is connected to the middle tap end of the secondary coil, and a second end of the fourth capacitor is grounded.

[0015] In a second aspect, the present invention provides a power amplifier including the above-mentioned differential balun circuit.

[0016] In a third aspect, the present invention provides a radio frequency chip including the above-mentioned power amplifier.

[0017] Compared with the related art, in an embodiment of the present invention, the primary coil and the secondary coil are coupled to each other, the first end of the primary coil is used to connect the input signal, the second end of the primary coil is grounded, the middle tap end of the secondary coil is grounded, the input end of the control switch network is used to connect the external DC voltage, the first output end of the control switch network is connected to the first differential output end of the secondary coil, the second output end of the control switch network is connected to the second differential output end of the secondary coil, and the control switch network is used to control the inductance value of the secondary coil. The parameter adjustable function such as the conversion ratio of the balun can be achieved without sacrificing the Q value (quality factor of the inductor). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be described in detail below with reference to the accompanying drawings. The above and other aspects of the present invention will become clearer and easier to understand through the detailed description made with reference to the following drawings.

[0019] Figure 1 A circuit diagram of a differential balun circuit provided in an embodiment of the present utility model;

[0020] Figure 2 A schematic diagram of a common-mode equivalent circuit of a differential balun circuit provided in an embodiment of the present utility model;

[0021] Figure 3 Schematic diagram of the differential mode equivalent circuit of the differential balun circuit provided in an embodiment of the present utility model.

[0022] Among them, 100 is a differential balun circuit, 10 is a control switch network, and 20 is a capacitor unit. DETAILED DESCRIPTION

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of the application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0024] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] First, see Figure 1-Figure 3 As shown, an embodiment of the present invention provides a differential balun circuit 100, comprising a primary coil L1, a secondary coil L2 coupled to the primary coil L1, and a control switch network 10. A first end of the primary coil L1 is connected to an input signal 1, a second end of the primary coil L1 is grounded, and a center tap end of the secondary coil L2 is grounded. An input end of the control switch network 10 is connected to an external DC voltage Vsw, a first output end of the control switch network 10 is connected to a first differential output end 2 of the secondary coil L2, and a second output end of the control switch network 10 is connected to a second differential output end 3 of the secondary coil L2. The control switch network 10 is used to control the inductance of the secondary coil L2. This allows for adjustable parameters such as the balun's conversion ratio without sacrificing the Q value (the quality factor of the inductor).

[0027] In this embodiment, the control switch network 10 includes a first capacitor C1, a first inductor L01, and a first diode D1. The first end of the first capacitor C1 is connected to the first end of the first inductor L01 and serves as the input end of the control switch network 10. The second end of the first capacitor C1 is grounded, the second end of the first inductor L01 is connected to the cathode of the first diode D1 and serves as the second output end of the control switch network 10, and the anode of the first diode D1 serves as the first output end of the control switch network 10. The first capacitor C1 is used to remove coupling between the primary coil L1 and the secondary coil L2, and the first inductor L01 functions as a choke inductor. The voltage of the first diode D1 is controlled by adjusting the voltage value of the DC voltage Vsw. When this voltage value is greater than the turn-on voltage of the first diode D1, the first diode D1 conducts; when this voltage value is less than the turn-on voltage of the first diode D1, the first diode D1 is turned off. By switching the two states of the first diode D1, the inductance of the secondary coil L2 can be controlled, thereby achieving the adjustable function of parameters such as the conversion ratio of the entire balun without affecting the Q value of the two-stage coil of the balun.

[0028] Specifically, such as Figure 3 As shown in the figure, since there is no capacitor in the equivalent circuit of the differential-mode signal, the fundamental signal can pass directly through the balun in this differential-mode situation without being affected by the harmonic network. Alternatively, an adjustable capacitor can be connected to the ground terminal of secondary coil L2, which can be adjusted to an optimal value during the commissioning phase to ensure optimal amplifier performance.

[0029] In this embodiment, the differential balun circuit 100 further includes a capacitor unit 20, with the middle tap end of the secondary coil L2 connected in series with the capacitor unit 20 and then grounded. By including the capacitor unit 20 for suppressing second-order harmonics, the second harmonics can be suppressed with little impact on the fundamental signal. Adjusting the value of the capacitor unit 20 adjusts the second harmonic state, controls the secondary impedance, and ensures overall amplifier performance. Furthermore, the second-order harmonics can be controlled without affecting the fundamental signal.

[0030] In this embodiment, the secondary coil L2 includes a first coil L21 and a second coil L22, and the capacitor unit 20 includes a second capacitor C2 and a third capacitor C3; the first end of the first coil L21 serves as the first differential output end 2 of the secondary coil L2, the second end of the first coil L21 is connected to the first end of the second capacitor C2, and the second end of the second capacitor C2 is grounded; the first end of the second coil L22 serves as the second differential output end 3 of the secondary coil L2, the second end of the second coil L22 is connected to the first end of the third capacitor C3, and the second end of the third capacitor C3 is grounded; the second end of the first coil L21 and the second end of the second coil L22 serve together as the middle tap end of the secondary coil L2. Figure 2 As shown, the secondary coil L2 is configured as a first coil L21 and a second coil L22 to achieve a common-mode function. The common-mode signal at the first differential output terminal 2 and the second differential output terminal 3 of the secondary coil L2 can both see the capacitor connected in parallel to ground, thereby short-circuiting the second-order harmonic to ground.

[0031] In this embodiment, the second capacitor C2 and the third capacitor C3 are both adjustable capacitors.

[0032] In this embodiment, the capacitor unit 20 includes a fourth capacitor C4. A first end of the fourth capacitor C4 is connected to the center tap of the secondary coil L2, and a second end of the fourth capacitor C4 is grounded. Furthermore, the fourth capacitor C4 is an adjustable capacitor and can be adjusted to an optimal value during the commissioning phase to ensure optimal amplifier performance.

[0033] In a second aspect, the present invention provides a power amplifier including the above-mentioned differential balun circuit 100 .

[0034] In a third aspect, the present invention provides a radio frequency chip including the above-mentioned power amplifier.

[0035] It should be noted that the various embodiments described above with reference to the accompanying drawings are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Those skilled in the art should understand that any modifications or equivalent substitutions to the present invention that do not depart from the spirit and scope of the present invention are intended to be encompassed within the scope of the present invention. Furthermore, unless the context otherwise requires, words appearing in the singular include the plural form, and vice versa. Furthermore, unless otherwise specified, all or part of any embodiment may be used in combination with all or part of any other embodiment.

Claims

1. A differential balun circuit, characterized in that: The invention comprises a primary coil, a secondary coil coupled to the primary coil, and a control switch network; the first end of the primary coil is used to connect to an input signal, the second end of the primary coil is grounded, the center tap end of the secondary coil is grounded, the input end of the control switch network is used to connect to an external DC voltage, the first output end of the control switch network is connected to the first differential output end of the secondary coil, the second output end of the control switch network is connected to the second differential output end of the secondary coil, and the control switch network is used to control the inductance value of the secondary coil.

2. The differential balun circuit according to claim 1, wherein: The control switch network includes a first capacitor, a first inductor and a first diode; The first end of the first capacitor is connected to the first end of the first inductor and serves as the input end of the control switch network; the second end of the first capacitor is grounded, the second end of the first inductor is connected to the cathode of the first diode and serves as the second output end of the control switch network, and the anode of the first diode serves as the first output end of the control switch network.

3. The differential balun circuit according to claim 2, wherein: The differential balun circuit further includes a capacitor unit, and the middle tap end of the secondary coil is connected in series with the capacitor unit and then grounded.

4. The differential balun circuit according to claim 3, wherein: The secondary coil includes a first coil and a second coil, and the capacitor unit includes a second capacitor and a third capacitor; The first end of the first coil serves as the first differential output end of the secondary coil, the second end of the first coil is connected to the first end of the second capacitor, and the second end of the second capacitor is grounded; The first end of the second coil serves as the second differential output end of the secondary coil, the second end of the second coil is connected to the first end of the third capacitor, and the second end of the third capacitor is grounded; the second end of the first coil and the second end of the second coil together serve as the middle tap end of the secondary coil.

5. The differential balun circuit according to claim 4, wherein: The second capacitor and the third capacitor are both adjustable capacitors.

6. The differential balun circuit according to claim 3, wherein: The capacitor unit includes a fourth capacitor, a first end of the fourth capacitor is connected to the middle tap end of the secondary coil, and a second end of the fourth capacitor is grounded.

7. A power amplifier, characterized in that: Comprising the differential balun circuit as described in any one of claims 1-6.

8. A radio frequency chip, characterized in that: Comprising the power amplifier as claimed in claim 7.

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