Low noise amplifier and radio frequency front end module

Abstract

The invention provides a low-noise amplifier and a radio frequency front-end module, and the low-noise amplifier comprises an input matching circuit, a first-stage power amplification circuit, an inter-stage matching circuit, a second-stage power amplification circuit and an output matching circuit. The inter-stage matching circuit comprises a first inductor, a second inductor and a first capacitor; the second-stage power amplification circuit is of a cascode structure; and the output matching circuit comprises a third inductor and a fourth inductor which are coupled with each other. According to the low-noise amplifier, the high-frequency gain, the in-band gain flatness, the isolation degree, the stability and the output matching bandwidth of the low-noise amplifier can be improved.

Description

Low-noise amplifiers and RF front-end modules Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a low-noise amplifier and a radio frequency front-end module. Background Technology

[0002] Low-noise amplifiers (LNAs) are key modules in the RF receiver link, responsible for amplifying weak RF signals while introducing as little noise as possible. In single-ended input LNA designs, current-reused structures are used to reduce LNA power consumption.

[0003] The current multiplexing structure in related technologies has the following drawbacks:

[0004] 1. Insufficient high-frequency gain: In the current-reused structure of related technologies, the interstage matching only has the necessary capacitors for the RF path and the necessary inductors for the DC path. This will result in reduced high-frequency gain and low in-band gain flatness.

[0005] 2. Low isolation: The current multiplexing structure in related technologies is essentially a two-stage common source stage with low isolation. When matching, the input and output affect each other, which makes the matching network design difficult. At the same time, its low isolation will reduce the stability of the low noise amplifier and bring the risk of oscillation.

[0006] 3. Narrow output matching bandwidth: The current multiplexing structure in related technologies generally adopts LC matching for output matching, which makes it difficult to achieve a wide matching width.

[0007] Therefore, a new low-noise amplifier and RF front-end module are needed to solve the above problems. Summary of the Invention

[0008] To address the shortcomings of the aforementioned related technologies, this invention proposes a novel low-noise amplifier and RF front-end module to solve the problems of insufficient high-frequency gain, low isolation, and narrow output matching bandwidth in low-noise amplifiers using current-reused structures in related technologies.

[0009] To address the aforementioned technical problems, in a first aspect, the present invention provides a low-noise amplifier, comprising an input matching circuit, a first-stage power amplifier circuit, an inter-stage matching circuit, a second-stage power amplifier circuit, and an output matching circuit; the input terminal of the input matching circuit is used to receive radio frequency signals; the input terminal of the first-stage power amplifier circuit is connected to the output terminal of the input matching circuit and is used to connect a first bias voltage, and the ground terminal of the first-stage power amplifier circuit is grounded; the inter-stage matching circuit includes a first inductor, a second inductor, and a first capacitor; a first terminal of the first inductor is connected to the output terminal of the first-stage power amplifier circuit; a first terminal of the second inductor is connected to the second terminal of the first inductor; and a first terminal of the first capacitor is connected to the output terminal of the first-stage power amplifier circuit. The second terminal of the first inductor; the second-stage power amplifier circuit has a common-source, common-gate structure; the first input terminal of the second-stage power amplifier circuit is connected to the second terminal of the first capacitor and is used to apply a second bias voltage; the second input terminal of the second-stage power amplifier circuit is used to apply a third bias voltage; the ground terminal of the second-stage power amplifier circuit is connected to the second terminal of the second inductor and then grounded; the output matching circuit includes a third inductor and a fourth inductor coupled to each other; the first terminal of the third inductor is used to apply the operating voltage; the second terminal of the third inductor is connected to the output terminal of the second-stage power amplifier circuit; the first terminal of the fourth inductor is connected to the output terminal of the second-stage power amplifier circuit; the second terminal of the fourth inductor is used to output radio frequency signals.

[0010] Preferably, the low-noise amplifier further includes a second capacitor; the ground terminal of the second stage power amplifier circuit is connected to the second terminal of the second inductor and then grounded through the second capacitor in series.

[0011] Preferably, the low-noise amplifier further includes a resistor connected in series between the ground terminal of the second-stage power amplifier circuit and the second capacitor.

[0012] Preferably, the input matching circuit includes a third capacitor and a fifth inductor; the first terminal of the third capacitor serves as the input terminal of the input matching circuit, and the second terminal of the third capacitor serves as the output terminal of the input matching circuit; the first terminal of the fifth inductor is connected to the first terminal of the third capacitor, and the second terminal of the fifth inductor is grounded.

[0013] Preferably, the first-stage power amplifier circuit includes a first field-effect transistor (FET); the gate of the first FET serves as the input terminal of the first-stage power amplifier circuit, the drain of the first FET serves as the output terminal of the first-stage power amplifier circuit, and the source of the first FET serves as the ground terminal of the first-stage power amplifier circuit.

[0014] Preferably, the low-noise amplifier further includes a sixth inductor; the ground terminal of the first-stage power amplifier circuit is grounded through the sixth inductor connected in series.

[0015] Preferably, the second-stage power amplifier circuit includes a second field-effect transistor (FET) and a third field-effect transistor (FET); the gate of the second FET serves as the first input terminal of the second-stage power amplifier circuit, and the source of the second FET serves as the ground terminal of the second-stage power amplifier circuit; the gate of the third FET serves as the second input terminal of the second-stage power amplifier circuit, the source of the third FET is connected to the drain of the second FET, and the drain of the third FET serves as the output terminal of the second-stage power amplifier circuit.

[0016] Preferably, the low-noise amplifier further includes a fourth capacitor; the first terminal of the fourth capacitor is connected to the gate of the third field-effect transistor, and the second terminal of the fourth capacitor is grounded.

[0017] Preferably, the output matching circuit further includes a fifth capacitor; the second terminal of the fourth inductor is connected in series with the fifth capacitor to output a radio frequency signal.

[0018] Secondly, the present invention provides a radio frequency front-end module, which includes a low-noise amplifier as described above.

[0019] Compared with related technologies, the low-noise amplifier of the present invention can achieve gain mismatch between the first-stage power amplifier circuit and the second-stage power amplifier circuit by adding a first inductor in the inter-stage matching circuit, thereby improving the high-frequency gain and in-band gain flatness of the low-noise amplifier; by designing the second-stage power amplifier circuit as a common-source common-gate structure, the isolation of the low-noise amplifier can be improved, thereby reducing the influence of input matching and output matching, reducing the design difficulty of the matching network, and improving the stability of the circuit; by designing the output matching circuit to include a third inductor and a fourth inductor that are coupled to each other, two output poles can be provided for it, and the bandwidth of the output matching can be effectively improved by adjusting the frequency position of the two poles. Attached Figure Description

[0020] 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 more readily understood through the detailed description in conjunction with the following drawings. In the drawings: Figure 1 is a circuit diagram of a low-noise amplifier provided in an embodiment of the present invention. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: This embodiment of the invention provides a low-noise amplifier 100, as shown in Figure 1, which includes an input matching circuit 1, a first-stage power amplifier circuit 2, an inter-stage matching circuit 3, a second-stage power amplifier circuit 4, and an output matching circuit 5.

[0025] The input terminal of the input matching circuit 1 is used to receive the radio frequency signal RFIN.

[0026] The input matching circuit 1 includes a third capacitor C3 and a fifth inductor L5.

[0027] The first terminal of the third capacitor C3 serves as the input terminal of the input matching circuit 1, and the second terminal of the third capacitor C3 serves as the output terminal of the input matching circuit 1; the third capacitor C3 also serves as an input DC blocking capacitor.

[0028] The first terminal of the fifth inductor L5 is connected to the first terminal of the third capacitor C3, and the second terminal of the fifth inductor L5 is grounded; the fifth inductor L5 serves as the input matching inductor.

[0029] The input terminal of the first-stage power amplifier circuit 2 is connected to the output terminal of the input matching circuit 1 and is used to connect the first bias voltage Vg1. The ground terminal of the first-stage power amplifier circuit 2 is grounded.

[0030] The first-stage power amplifier circuit 2 includes a first field-effect transistor M1; the gate of the first field-effect transistor M1 serves as the input terminal of the first-stage power amplifier circuit 2, the drain of the first field-effect transistor M1 serves as the output terminal of the first-stage power amplifier circuit 2, and the source of the first field-effect transistor M1 serves as the ground terminal of the first-stage power amplifier circuit 2.

[0031] The low-noise amplifier 100 also includes a sixth inductor L6; the ground terminal of the first-stage power amplifier circuit 2 is grounded through the sixth inductor L6 in series; the sixth inductor L6 serves as the source degenerate inductor.

[0032] The interstage matching circuit 3 includes a first inductor L1, a second inductor L2, and a first capacitor C1.

[0033] The first terminal of the first inductor L1 is connected to the output terminal of the first-stage power amplifier circuit 2.

[0034] The first end of the second inductor L2 is connected to the second end of the first inductor L1; the second inductor L2 serves as the current-blocking inductor for the DC path in the interstage matching.

[0035] The first terminal of the first capacitor C1 is connected to the second terminal of the first inductor L1; the first capacitor C1 serves as the DC blocking capacitor for the RF path in interstage matching.

[0036] The second-stage power amplifier circuit 4 is a cascode structure (CSCG). The first input terminal of the second-stage power amplifier circuit 4 is connected to the second terminal of the first capacitor C1 and is used to connect the second bias voltage Vg2. The second input terminal of the second-stage power amplifier circuit 4 is used to connect the third bias voltage Vg3. The ground terminal of the second-stage power amplifier circuit 4 is connected to the second terminal of the second inductor L2 and then grounded.

[0037] The second-stage power amplifier circuit 4 includes a second field-effect transistor M2 and a third field-effect transistor M3.

[0038] The gate of the second field-effect transistor M2 serves as the first input terminal of the second-stage power amplifier circuit 4, and the source of the second field-effect transistor M2 serves as the ground terminal of the second-stage power amplifier circuit 4.

[0039] The gate of the third field-effect transistor M3 serves as the second input terminal of the second-stage power amplifier circuit 4. The source of the third field-effect transistor M3 is connected to the drain of the second field-effect transistor M2. The drain of the third field-effect transistor M3 serves as the output terminal of the second-stage power amplifier circuit 4.

[0040] The low-noise amplifier 100 also includes a fourth capacitor C4; the first end of the fourth capacitor C4 is connected to the gate of the third field-effect transistor M3, and the second end of the fourth capacitor C4 is grounded.

[0041] The output matching circuit 5 includes a third inductor L3 and a fourth inductor L4 that are coupled to each other; the coupling coefficient between the third inductor L3 and the fourth inductor L4 is k.

[0042] The first terminal of the third inductor L3 is connected to the operating voltage VDD, and the second terminal of the third inductor L3 is connected to the output terminal of the second-stage power amplifier circuit 4.

[0043] The first end of the fourth inductor L4 is connected to the output of the second-stage power amplifier circuit 4, and the second end of the fourth inductor L4 is used to output the radio frequency signal RFOUT.

[0044] The third inductor L3 and the fourth inductor L4 are coupled to each other, which can cause the reflection coefficient corresponding to the output return loss to have two poles. By adjusting the position of these two poles, the bandwidth of the output matching can be expanded. Specifically, by writing the input matching transfer function, the relationship between the third inductor L3 and the fourth inductor L4 and the frequency f at the two poles can be solved, and the bandwidth can be adjusted by the inductance value and the coupling coefficient k.

[0045] The output matching circuit 5 also includes a fifth capacitor C5; the second end of the fourth inductor L4 is connected in series with the fifth capacitor C5 to output the radio frequency signal RFOUT; the fifth capacitor C5 serves as the output DC blocking capacitor.

[0046] In this embodiment, the low-noise amplifier 100 also includes a second capacitor C2; the ground terminal of the second-stage power amplifier circuit 4 is connected to the second terminal of the second inductor L2 and then grounded through the second capacitor C2 in series. The second capacitor C2 in this embodiment is not a conventional large capacitor to serve as an ideal AC ground. Instead, when the capacitance value of the second capacitor C2 is small, it works in conjunction with the first inductor L1 to achieve a low negative resistance in the Zout1 (output impedance) transfer function looking backward from the first field-effect transistor M1 at high frequencies. This effectively improves the gain of the low-noise amplifier 100 at high frequencies and reduces high-frequency gain roll-off. Simultaneously, by increasing the isolation of the low-noise amplifier 100, adjusting circuit parameters, or adding negative feedback, the overall stability of the low-noise amplifier 100 can be maintained.

[0047] The low-noise amplifier 100 also includes a resistor R connected in series between the ground terminal of the second-stage power amplifier circuit 4 and the second capacitor C2; that is, the resistor R is connected in series between the source of the second field-effect transistor M2 and the second capacitor C2. By adding a resistor R between the source of the second field-effect transistor M2 and the second capacitor C2, a negative feedback can be provided to the second field-effect transistor M2. Compared with related technologies that add RC negative feedback between the gate and drain of the field-effect transistor, the design of the resistor R has less impact on the noise of the low-noise amplifier 100 and can improve the stability and gain flatness of the low-noise amplifier 100.

[0048] In the low-noise amplifier 100 of this embodiment, the radio frequency signal enters from the input terminal of the input matching circuit 1, is amplified by the first field-effect transistor M1, and then passes through the first inductor L1 and the first capacitor C1 before reaching the second field-effect transistor M2. After being amplified by the second field-effect transistor M2 and the third field-effect transistor M3, it is output by the output matching circuit 5. The operating voltage VDD of the DC path enters through the third inductor L3 in the output matching circuit 5. The current flows through the third field-effect transistor M3, the second field-effect transistor M2, the second inductor L2, the first inductor L1, the first field-effect transistor M1, and the sixth inductor L6 before reaching ground. The three field-effect transistors share the current and voltage margin.

[0049] Compared with related technologies, the low-noise amplifier 100 in this embodiment can achieve gain mismatch between the first-stage power amplifier circuit 2 and the second-stage power amplifier circuit 4 by adding a first inductor L1 to the interstage matching circuit 3, thereby improving the high-frequency gain and in-band gain flatness of the low-noise amplifier 100; by designing the second-stage power amplifier circuit 4 as a common-source common-gate structure, the isolation of the low-noise amplifier 100 can be improved, thereby reducing the influence of input matching and output matching, reducing the design difficulty of the matching network, and improving the stability of the circuit; by designing the output matching circuit 5 to include a third inductor L3 and a fourth inductor L4 that are coupled to each other, two output poles can be provided for it, and the bandwidth of the output matching can be effectively improved by adjusting the frequency position of the two poles.

[0050] Example 2 This example provides a radio frequency (RF) front-end module, which includes the low-noise amplifier 100 from Example 1. Since the RF front-end module in this example includes the low-noise amplifier 100 from Example 1, it can also achieve the same technical effects as the low-noise amplifier 100 in Example 1, and will not be described in detail here.

[0051] It should be noted that the various embodiments described above with reference to the accompanying drawings are merely 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 included within the scope of the present invention. Furthermore, unless the context otherwise requires, words appearing in the singular include those in the plural, 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-noise amplifier, characterized in that, The low-noise amplifier includes an input matching circuit, a first-stage power amplifier circuit, an inter-stage matching circuit, a second-stage power amplifier circuit, and an output matching circuit. The input terminal of the input matching circuit receives radio frequency signals. The input terminal of the first-stage power amplifier circuit is connected to the output terminal of the input matching circuit and is used to apply a first bias voltage. The ground terminal of the first-stage power amplifier circuit is grounded. The inter-stage matching circuit includes a first inductor, a second inductor, and a first capacitor. The first terminal of the first inductor is connected to the output terminal of the first-stage power amplifier circuit. The first terminal of the second inductor is connected to the second terminal of the first inductor. The first terminal of the first capacitor is connected to the second terminal of the first inductor. The second-stage power amplifier circuit has a common-source, common-gate structure. The first input terminal of the second-stage power amplifier circuit is connected to the second terminal of the first capacitor and is used to apply a second bias voltage. The second input terminal of the second-stage power amplifier circuit is used to apply a third bias voltage. The ground terminal of the second-stage power amplifier circuit is connected to the second terminal of the second inductor and then grounded. The output matching circuit includes a third inductor and a fourth inductor coupled to each other. The first terminal of the third inductor is used to apply the operating voltage, and the second terminal of the third inductor is connected to the output terminal of the second-stage power amplifier circuit. The first terminal of the fourth inductor is connected to the output terminal of the second-stage power amplifier circuit, and the second terminal of the fourth inductor is used to output a radio frequency signal.

2. The low-noise amplifier as described in claim 1, characterized in that, The low-noise amplifier also includes a second capacitor; the ground terminal of the second stage power amplifier circuit is connected to the second terminal of the second inductor and then grounded through the second capacitor in series.

3. The low-noise amplifier as described in claim 2, characterized in that, The low-noise amplifier also includes a resistor connected in series between the ground terminal of the second-stage power amplifier circuit and the second capacitor.

4. The low-noise amplifier as described in claim 1, characterized in that, The input matching circuit includes a third capacitor and a fifth inductor; the first terminal of the third capacitor serves as the input terminal of the input matching circuit, and the second terminal of the third capacitor serves as the output terminal of the input matching circuit; the first terminal of the fifth inductor is connected to the first terminal of the third capacitor, and the second terminal of the fifth inductor is grounded.

5. The low-noise amplifier as described in claim 1, characterized in that, The first-stage power amplifier circuit includes a first field-effect transistor (FET); the gate of the first FET serves as the input terminal of the first-stage power amplifier circuit, the drain of the first FET serves as the output terminal of the first-stage power amplifier circuit, and the source of the first FET serves as the ground terminal of the first-stage power amplifier circuit.

6. The low-noise amplifier as described in claim 1, characterized in that, The low-noise amplifier also includes a sixth inductor; the ground terminal of the first-stage power amplifier circuit is grounded through the sixth inductor connected in series.

7. The low-noise amplifier as claimed in claim 1, characterized in that, The second-stage power amplifier circuit includes a second field-effect transistor (FET) and a third field-effect transistor (FET). The gate of the second FET serves as the first input terminal of the second-stage power amplifier circuit, and the source of the second FET serves as the ground terminal of the second-stage power amplifier circuit. The gate of the third FET serves as the second input terminal of the second-stage power amplifier circuit, the source of the third FET is connected to the drain of the second FET, and the drain of the third FET serves as the output terminal of the second-stage power amplifier circuit.

8. The low-noise amplifier as described in claim 7, characterized in that, The low-noise amplifier also includes a fourth capacitor; the first terminal of the fourth capacitor is connected to the gate of the third field-effect transistor, and the second terminal of the fourth capacitor is grounded.

9. The low-noise amplifier as claimed in claim 1, characterized in that, The output matching circuit also includes a fifth capacitor; the second terminal of the fourth inductor outputs a radio frequency signal after being connected in series with the fifth capacitor.

10. A radio frequency front-end module, characterized in that, The radio frequency front-end module includes a low-noise amplifier as described in any one of claims 1 to 9.

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