Low-pass filter, radio frequency power amplifier and radio frequency power amplifier module

Abstract

The utility model provides a low pass filter, a radio frequency power amplifier and a radio frequency power amplifier module, the low pass filter comprises a first inductor, a first second harmonic suppression circuit, a third harmonic suppression circuit, a second inductor, a first capacitor, a higher harmonic suppression circuit and a second second harmonic suppression circuit; the first secondary harmonic suppression circuit comprises a second capacitor and a third inductor; the third harmonic suppression circuit is used for suppressing harmonic signals; the higher harmonic suppression circuit is used for suppressing higher harmonic signals; and the second secondary harmonic suppression circuit comprises a third capacitor and a fourth inductor. The low-pass filter can effectively reduce the influence of impedance failure on the output end of the low-pass filter, and even if the standing wave ratio of the output end of the low-pass filter is large, a good harmonic suppression effect can still be achieved.

Description

Technical Field

[0001] This utility model relates to the field of wireless communication technology, and in particular to a low-pass filter, a radio frequency power amplifier, and a radio frequency power amplifier module. Background Technology

[0002] The development of mobile communication has gone through different stages from 1G to 5G, and it has now achieved coverage of more than 95% of the population. However, in terms of geographical coverage, there are still areas such as high mountains, grasslands, forests and deserts that have not yet been covered.

[0003] The current goal of mobile communication development is to achieve the "5Ws" that include whoever, wherever, whenever, whomever, and whatever, meaning that anyone can communicate with anyone, anytime, anywhere, in any form.

[0004] The goal of enabling communication anywhere, a goal that has yet to be achieved despite advancements from 1G to 5G, can be addressed through satellite communication in the future. The integration of satellite communication with 5G has become a current hot topic. Undeniably, the integration of satellite communication into the mainstream of mobile communication is an industry consensus. Because satellites are farther from the ground, signal path loss is greater than in traditional 4G and 5G, placing higher demands on the power of radio frequency (RF) power amplifiers. Furthermore, as nonlinear components, RF power amplifiers generate harmonic signals that can interfere with other normally functioning devices. Therefore, suppressing harmonic signals from RF power amplifiers is particularly crucial in satellite communication systems.

[0005] In existing technologies, devices for suppressing harmonic signals from RF power amplifiers employ harmonic suppression networks or low-pass filters. A common low-pass filter is the Butterworth low-pass filter, whose input is connected to the output of the RF power amplifier, and whose output is connected to a downstream circuit, such as an antenna or chip. This low-pass filter includes four capacitors and five inductors. One capacitor and one inductor form a second harmonic suppression circuit, resonating at the second harmonic frequency, suppressing the second harmonic output of the RF power amplifier and preventing it from being transmitted to the next stage circuit. Another capacitor and another inductor form a third harmonic suppression circuit, resonating at the third harmonic frequency, suppressing the third harmonic frequency and preventing it from being transmitted to the next stage circuit. The remaining two capacitors and two inductors form a higher harmonic suppression circuit, used to suppress higher harmonic signals. The second, third, and higher harmonic suppression circuits together constitute the stopband of the low-pass filter. The main frequency signal is located within the passband of the low-pass filter and can be transmitted from the input to the output, thus achieving the effect of low-pass filtering.

[0006] Although the low-pass filter mentioned above can suppress harmonic signals, its output impedance is greatly affected. When the output impedance deviates from 50Ω, its ability to suppress harmonic signals will decrease. Utility Model Content

[0007] To address the shortcomings of the existing technologies, this invention proposes a new low-pass filter, an RF power amplifier, and an RF power amplifier module to solve the problem that the low-pass filter in the existing technology will reduce its ability to suppress harmonic signals after the impedance at its output terminal deviates by 50Ω.

[0008] To solve the above-mentioned technical problems, in a first aspect, the present invention provides a low-pass filter, which includes a first inductor, a first second harmonic suppression circuit, a third harmonic suppression circuit, a second inductor, a first capacitor, a higher harmonic suppression circuit, and a second second harmonic suppression circuit.

[0009] The first terminal of the first inductor serves as the input terminal of the low-pass filter;

[0010] The first second harmonic suppression circuit includes a second capacitor and a third inductor; the first terminal of the second capacitor is connected to the first terminal of the first inductor, the first terminal of the third inductor is connected to the second terminal of the second capacitor, and the second terminal of the third inductor is grounded;

[0011] The third harmonic suppression circuit is used to suppress harmonic signals. The input terminal of the third harmonic suppression circuit is connected to the second terminal of the first inductor, and the output terminal of the third harmonic suppression circuit is grounded.

[0012] The first end of the second inductor is connected to the input end of the third harmonic suppression circuit;

[0013] The first terminal of the first capacitor is connected to the second terminal of the second inductor, and the second terminal of the first capacitor is grounded.

[0014] The higher harmonic suppression circuit is used to suppress higher harmonic signals. The input terminal of the higher harmonic suppression circuit is connected to the first terminal of the first capacitor, and the output terminal of the higher harmonic suppression circuit serves as the output terminal of the low-pass filter.

[0015] The second harmonic suppression circuit includes a third capacitor and a fourth inductor. The first terminal of the third capacitor is connected to the output terminal of the higher harmonic suppression circuit, and the first terminal of the fourth inductor is connected to the second terminal of the third capacitor. The second terminal of the fourth inductor is grounded.

[0016] Preferably, the third harmonic suppression circuit includes a fourth capacitor and a fifth inductor. The first terminal of the fourth capacitor serves as the input terminal of the third harmonic suppression circuit, the first terminal of the fifth inductor is connected to the second terminal of the fourth capacitor, and the second terminal of the fifth inductor serves as the output terminal of the third harmonic suppression circuit.

[0017] Preferably, the high-order harmonic suppression circuit includes a sixth inductor and a fifth capacitor. The first end of the sixth inductor serves as the input terminal of the high-order harmonic suppression circuit, the first end of the fifth capacitor is connected to the second end of the sixth inductor, and the second end of the fifth capacitor serves as the output terminal of the low-pass filter.

[0018] Secondly, this utility model provides an RF power amplifier, which includes the low-pass filter described above.

[0019] Thirdly, this utility model provides an RF power amplifier module, which includes the RF power amplifier described above.

[0020] Compared with the prior art, the low-pass filter in this invention, through the combination of the second and first harmonic suppression circuits, can effectively reduce the impact of impedance failure at the output end of the low-pass filter. Even if the standing wave ratio at the output end is large, it can still achieve a good harmonic suppression effect. Attached Figure Description

[0021] The present invention will now be described in detail 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 in conjunction with the following drawings. In the drawings:

[0022] Figure 1 The circuit schematic diagram of the low-pass filter provided in this embodiment of the utility model;

[0023] Figure 2 A comparison chart of simulation results between the low-pass filter provided in this embodiment of the utility model and the low-pass filter provided in the prior art. Detailed Implementation

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0025] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] Example 1

[0028] This utility model embodiment provides a low-pass filter 100, combined with... Figure 1 As shown, it includes a first inductor L1, a first second harmonic suppression circuit 1, a third harmonic suppression circuit 2, a second inductor L2, a first capacitor C1, a higher harmonic suppression circuit 3, and a second second harmonic suppression circuit 4.

[0029] The first terminal of the first inductor L1 serves as the input terminal of the low-pass filter 100.

[0030] The first and second harmonic suppression circuit 1 includes a second capacitor C2 and a third inductor L3; the first end of the second capacitor C2 is connected to the first end of the first inductor L1, the first end of the third inductor L3 is connected to the second end of the second capacitor C2, and the second end of the third inductor L3 is grounded.

[0031] The third harmonic suppression circuit 2 is used to suppress harmonic signals. The input terminal of the third harmonic suppression circuit 2 is connected to the second terminal of the first inductor L1, and the output terminal of the third harmonic suppression circuit 2 is grounded.

[0032] In this embodiment, the third harmonic suppression circuit 2 includes a fourth capacitor C4 and a fifth inductor L5. The first end of the fourth capacitor C4 serves as the input terminal of the third harmonic suppression circuit 2, the first end of the fifth inductor L5 is connected to the second end of the fourth capacitor C4, and the second end of the fifth inductor L5 serves as the output terminal of the third harmonic suppression circuit 2.

[0033] The first terminal of the second inductor L2 is connected to the input terminal of the third harmonic suppression circuit 2.

[0034] The first terminal of the first capacitor C1 is connected to the second terminal of the second inductor L2, and the second terminal of the first capacitor C1 is grounded.

[0035] The high-order harmonic suppression circuit 3 is used to suppress high-order harmonic signals. The input terminal of the high-order harmonic suppression circuit 3 is connected to the first terminal of the first capacitor C1, and the output terminal of the high-order harmonic suppression circuit 3 serves as the output terminal of the low-pass filter 100.

[0036] In this embodiment, the high-order harmonic suppression circuit 3 includes a sixth inductor L6 and a fifth capacitor C5. The first end of the sixth inductor L6 serves as the input terminal of the high-order harmonic suppression circuit 3, and the first end of the fifth capacitor C5 is connected to the second end of the sixth inductor L6. The second end of the fifth capacitor C5 serves as the output terminal of the low-pass filter 100.

[0037] The second harmonic suppression circuit 4 includes a third capacitor C3 and a fourth inductor L4. The first end of the third capacitor C3 is connected to the output end of the high-order harmonic suppression circuit 3, the first end of the fourth inductor L4 is connected to the second end of the third capacitor C3, and the second end of the fourth inductor L4 is grounded.

[0038] The input terminal of the low-pass filter 100, the first inductor L1, the second inductor L2, the sixth inductor L6, the fifth capacitor C5, and the output terminal of the low-pass filter 100 constitute the main signal path.

[0039] In this embodiment, the low-pass filter 100 is modified by altering the design of the higher harmonic suppression circuit 3 and adding a second harmonic suppression circuit 4. When the capacitor and inductor are connected in series to ground, the capacitor value is C and the inductor value is L. The formula for calculating the harmonic frequency is as follows:

[0040]

[0041] With the capacitor and inductor grounded, the impedance at the output of the low-pass filter 100 is expressed as follows:

[0042]

[0043] When at the resonant frequency, it is represented as follows:

[0044] Z trap|f＝f0 =0;

[0045] The low-pass filter 100 has zero impedance in the main signal path. When the harmonic signal passes through, it will undergo total reflection and the phase will change by 180°. Therefore, the harmonic frequency cannot be transmitted to the next stage circuit, thus achieving a better harmonic suppression effect.

[0046] like Figure 2As shown, the first and second harmonic suppression circuit 1 resonates at a first frequency, and the second and second harmonic suppression circuit 4 resonates at a second frequency. The first resonant frequency is lower than the second resonant frequency, thus achieving the effect of broadband aluminum foil. With the introduction of the second and second harmonic suppression circuit 4, the low-pass filter 100 in this embodiment is less sensitive to impedance at its output terminal than low-pass filters in the prior art. Even when the output terminals of the two circuits are mismatched, the low-pass filter 100 in this embodiment can still achieve good filtering or harmonic suppression effects. Furthermore, by designing a high-order harmonic suppression circuit 3 formed by the sixth inductor L6 and the fifth capacitor C5, and connecting it in series in the main signal path, the low-pass filter 100 can utilize the parasitic parameter characteristics of the capacitor and inductor themselves, achieving a better suppression of high-order harmonic frequencies compared to low-pass filters in the prior art.

[0047] Compared with the prior art, the low-pass filter 100 in this embodiment, through the combination of the second second harmonic suppression circuit 4 and the first second harmonic suppression circuit 1, can effectively reduce the impact of impedance failure at its output terminal on the low-pass filter 100. Even if the standing wave ratio at its output terminal is large, it can still achieve a good harmonic suppression effect. In addition, by designing the high-order harmonic suppression circuit 3 formed by the sixth inductor L6 and the fifth capacitor C5 and connecting it in series in the main signal path, the suppression ratio of high-order harmonics can be increased, making it more suitable for radio frequency systems than the design scheme of increasing the order of the low-pass filter 100.

[0048] Example 2

[0049] This embodiment provides a radio frequency power amplifier, which includes the low-pass filter 100 from Embodiment 1. Since the radio frequency power amplifier in this embodiment includes the low-pass filter 100 from Embodiment 1, it can also achieve the same technical effect as the low-pass filter 100 in Embodiment 1, and will not be described in detail here.

[0050] Example 3

[0051] This embodiment provides an RF power amplifier module, which includes the RF power amplifier in Embodiment 2. Since the RF power amplifier module in this embodiment includes the RF power amplifier in Embodiment 2, it can achieve the same technical effect as the RF power amplifier in Embodiment 2, and will not be described in detail here.

[0052] It should be noted that the various embodiments described above with reference to the accompanying drawings are only illustrative of the present invention and not intended to limit its scope. Those skilled in the art should understand that any modifications or equivalent substitutions made to the present invention without departing from its spirit and scope should be covered within the scope of the present invention. Furthermore, unless the context otherwise requires, singular terms include plural forms, and vice versa. Additionally, unless specifically stated otherwise, all or part of any embodiment may be used in conjunction with all or part of any other embodiment.

Claims

1. A low-pass filter, characterized in that, The low-pass filter includes a first inductor, a first second harmonic suppression circuit, a third harmonic suppression circuit, a second inductor, a first capacitor, a higher harmonic suppression circuit, and a second second harmonic suppression circuit. The first terminal of the first inductor serves as the input terminal of the low-pass filter; The first second harmonic suppression circuit includes a second capacitor and a third inductor; the first terminal of the second capacitor is connected to the first terminal of the first inductor, the first terminal of the third inductor is connected to the second terminal of the second capacitor, and the second terminal of the third inductor is grounded; The third harmonic suppression circuit is used to suppress harmonic signals. The input terminal of the third harmonic suppression circuit is connected to the second terminal of the first inductor, and the output terminal of the third harmonic suppression circuit is grounded. The first end of the second inductor is connected to the input end of the third harmonic suppression circuit; The first terminal of the first capacitor is connected to the second terminal of the second inductor, and the second terminal of the first capacitor is grounded. The higher harmonic suppression circuit is used to suppress higher harmonic signals. The input terminal of the higher harmonic suppression circuit is connected to the first terminal of the first capacitor, and the output terminal of the higher harmonic suppression circuit serves as the output terminal of the low-pass filter. The second harmonic suppression circuit includes a third capacitor and a fourth inductor. The first terminal of the third capacitor is connected to the output terminal of the higher harmonic suppression circuit, and the first terminal of the fourth inductor is connected to the second terminal of the third capacitor. The second terminal of the fourth inductor is grounded.

2. The low-pass filter as described in claim 1, characterized in that, The third harmonic suppression circuit includes a fourth capacitor and a fifth inductor. The first terminal of the fourth capacitor serves as the input terminal of the third harmonic suppression circuit, the first terminal of the fifth inductor is connected to the second terminal of the fourth capacitor, and the second terminal of the fifth inductor serves as the output terminal of the third harmonic suppression circuit.

3. The low-pass filter as described in claim 1, characterized in that, The high-order harmonic suppression circuit includes a sixth inductor and a fifth capacitor. The first end of the sixth inductor serves as the input terminal of the high-order harmonic suppression circuit, the first end of the fifth capacitor is connected to the second end of the sixth inductor, and the second end of the fifth capacitor serves as the output terminal of the low-pass filter.

4. A radio frequency power amplifier, characterized in that, The radio frequency power amplifier includes a low-pass filter as described in any one of claims 1 to 3.

5. A radio frequency power amplifier module, characterized in that, The radio frequency power amplifier module includes the radio frequency power amplifier as described in claim 4.

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