A K-band limiting low-noise amplifier

Abstract

The present invention discloses a K-band limiting low-noise amplifier, which belongs to the field of radio frequency microelectronics technology. The amplifier comprises an input matching module, a diode limiting module, an inter-stage matching module, a low-noise amplifier module, and an output matching module, which are sequentially connected in cascade. The input matching module is used to achieve impedance matching between the radio frequency signal input end and the diode limiting module, and transmit the radio frequency signal. The diode limiting module is used to limit the radio frequency signal and transmit it. The inter-stage matching module is used to achieve impedance matching between the diode limiting module and the low-noise amplifier module. The low-noise amplifier module is used to amplify and transmit the limited radio frequency signal. The output matching module is used to achieve impedance matching between the low-noise amplifier module and the radio frequency signal output end, and output the amplified radio frequency signal. The present invention can limit the amplitude of the input signal so that it remains within the range that the low-noise amplifier circuit can withstand, thereby ensuring the stability and reliability of the entire system.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency microelectronics technology, and more particularly to a K-band amplitude limiting low noise amplifier. Background Art

[0002] Currently, in RF receiving systems, the low-noise amplifier (LNA) is located at the front end of the receiving chain and is an indispensable component of the signal chain. Its main function is to amplify weak RF signals and enhance them so that subsequent signal processing can be carried out effectively.

[0003] However, in complex electromagnetic environments, unexpected high-power signal spikes or spurious signals may occur. For example, in radar, satellite communication and other systems, the power level of the received signal may fluctuate greatly. Such sudden strong signals not only pose challenges to the receiving system, but may even cause damage to the low-noise amplifier.

[0004] Due to the design limitations of traditional low-noise amplifiers, they typically lack the ability to automatically limit input signals and have low power handling capabilities, resulting in an inability to effectively protect against strong signals exceeding their tolerance range. Once a high-power signal exceeds its design capacity, the low-noise amplifier may fail or malfunction, compromising the signal processing stability and reliability of the entire system, impacting its normal operation.

[0005] Therefore, how to solve the lack of adaptive processing capabilities for such high-power signals has become an important technical challenge in the current design of RF receiving systems. Summary of the Invention

[0006] In light of this, the present invention provides a K-band limiting low-noise amplifier that at least partially addresses the aforementioned issues with prior art low-noise amplifiers, such as a lack of automatic limiting capability, low power handling, and unstable signal processing. This invention utilizes cascaded limiters to limit the amplitude of the input signal, keeping it within the acceptable range of the low-noise amplifier circuit, thereby ensuring the stability and reliability of the entire system.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A K-band limiting low-noise amplifier provided in an embodiment of the present invention comprises: an input matching module, a diode limiting module, an inter-stage matching module, a low-noise amplification module and an output matching module which are cascaded in sequence;

[0009] The input matching module is used to achieve impedance matching between the RF signal input terminal and the diode limiter module, and transmit the received RF signal to the diode limiter module;

[0010] The diode limiting module is used to limit the RF signal and transmit the limited RF signal to the inter-stage matching module;

[0011] The inter-stage matching module is used to achieve impedance matching between the diode limiting module and the low-noise amplification module, and transmit the limited RF signal to the low-noise amplification module;

[0012] The low noise amplification module is used to amplify the limited RF signal and transmit it to the output matching module;

[0013] The output matching module is used to achieve impedance matching between the low-noise amplification module and the radio frequency signal output end, and output the amplified radio frequency signal from the radio frequency signal output end.

[0014] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following advantages:

[0015] 1. Large power capacity: In the present invention, by adding a parallel diode branch to the first-stage limiting circuit in the diode limiting module, the heat dissipation area is effectively increased while ensuring that the PIN diode is not damaged due to excessive power, thereby significantly improving the power capacity of the low-noise amplifier.

[0016] 2. Low noise coefficient: In the present invention, by connecting inductors L1 and L2 in parallel with two PIN diode branches respectively, the first-stage limiting circuit is equivalent to an ideal open circuit when a small signal is input. This can reduce its insertion loss while maintaining the high power capacity of the first-stage limiting circuit, thereby further reducing the overall circuit noise.

[0017] 3. High gain: In the present invention, the first-stage amplifier circuit of the low-noise amplifier module is designed by adopting a common-source common-gate structure, which reduces the capacitive feedback between the transistor input and output, increases the output impedance of the amplifier at this stage, and effectively improves the high-frequency gain of the entire low-noise amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0019] Figure 1 This is a schematic diagram of the structure of the K-band limiting low noise amplifier of the present invention;

[0020] Figure 2 This is a circuit diagram of a K-band limiting low-noise amplifier according to the present invention;

[0021] Figure 3 This is a comparison chart of the insertion loss results of the PIN diode limiter in the K-band limiting low-noise amplifier of the present invention (with and without parallel inductors L1 and L2);

[0022] Figure 4 This is a voltage standing wave ratio diagram of the K-band limiting low noise amplifier of the present invention;

[0023] Figure 5 This is a small signal gain diagram of the K-band limiting low noise amplifier of the present invention;

[0024] Figure 6 This is a noise figure diagram of the K-band limiting low noise amplifier of the present invention.

[0025] In the accompanying drawings: input matching module (1); diode limiter module (2); inter-stage matching module (3); low-noise amplifier module (4); output matching module (5); first-stage amplifier circuit (A1); second-stage amplifier circuit (A2);

[0026] PIN diodes (D1-D14); transmission lines (TL1-TL18); capacitors (C1-C13); resistors (R1-R12); transistors (M1-M3); inductors (L1, L2); and a DC bias supply (Vd). DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments 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.

[0028] like Figure 1 As shown, an embodiment of the present invention discloses a K-band limiting low noise amplifier, which includes: an input matching module 1, a diode limiting module 2, an inter-stage matching module 3, a low noise amplification module 4 and an output matching module 5, which are cascaded in sequence;

[0029] The input matching module 1 is used to achieve impedance matching between the RF signal input terminal IN and the diode limiter module 2, and transmit the received RF signal to the diode limiter module 2;

[0030] The diode limiter module 2 is used to limit the RF signal and transmit the RF signal to the inter-stage matching module 3;

[0031] The inter-stage matching module 3 is used to achieve impedance matching between the diode limiting module 2 and the low-noise amplifier module 4, and transmit the limited RF signal to the low-noise amplifier module 4;

[0032] The low noise amplifier module 4 is used to amplify the limited RF signal and transmit it to the output matching module 5;

[0033] The output matching module 5 is used to achieve impedance matching between the low-noise amplification module 4 and the radio frequency signal output terminal OUT, and output the amplified radio frequency signal from the radio frequency signal output terminal OUT.

[0034] The main body of the present invention adopts a cascade connection between a limiter and a low-noise amplifier to increase the power capacity of the low-noise amplifier, which can limit the amplitude of the input signal to keep it within the range that the low-noise amplifier circuit can withstand, thereby ensuring the stability and reliability of the entire system.

[0035] The following is a detailed description of each of the above modules:

[0036] Further, such as Figure 2 As shown, the input matching module 1 includes: a capacitor C1, transmission lines TL1 and TL2;

[0037] One end of the capacitor C1 of the input matching module 1 is connected to the RF signal input terminal IN, and the other end is connected to one end of the transmission lines TL1 and TL2; the other end of the transmission line TL1 is suspended, and the other end of the transmission line TL2 is connected to the input end of the diode limiter module 2;

[0038] The capacitor C1 is a DC blocking capacitor for isolating DC, and the transmission lines TL1 and TL2 are used for impedance matching and bandwidth optimization.

[0039] Further, such as Figure 2 As shown, the diode limiting module 2 includes: a PIN diode for input signal limiting (i.e., a first-stage limiting circuit and a second-stage limiting circuit); inductors L1 and L2 for impedance resonance, transmission lines TL3 and TL5 for impedance matching, and a short-circuit transmission line TL4 for impedance matching and DC grounding.

[0040] The first-stage limiter circuit is composed of twelve PIN diodes D1-D12 connected in series-parallel; the second-stage limiter circuit is composed of two PIN diodes D13-D14 connected in parallel.

[0041] Specifically, the anode of diode D1 is grounded, and its cathode is connected to the anode of diode D2, the cathode of diode D2 is connected to the anode of diode D3, and the cathode of diode D3 is connected to one end of transmission lines TL2, TL3 and inductors L1, L2 respectively;

[0042] The anode of the diode D4 is grounded, and the cathode thereof is connected to the anode of the diode D5. The cathode of the diode D5 is connected to the anode of the diode D6. The cathode of the diode D6 is connected to one end of the transmission lines TL2 and TL3 and the inductors L1 and L2.

[0043] The anode of the diode D7 is connected to the transmission lines TL2 and TL3 and one end of the inductors L1 and L2, and the cathode of the diode D7 is connected to the anode of the diode D8. The cathode of the diode D8 is connected to the anode of the diode D9, and the cathode of the diode D9 is grounded.

[0044] The anode of diode D10 is connected to the transmission lines TL2 and TL3 and one end of the inductors L1 and L2, and the cathode of diode D10 is connected to the anode of diode D11. The cathode of diode D11 is connected to the anode of diode D12, and the cathode of diode D12 is grounded.

[0045] The other ends of inductors L1 and L2 are grounded;

[0046] The other end of the transmission line TL3 is connected to the transmission lines TL4 and TL5, the other end of the transmission line TL4 is grounded, and the other end of the transmission line TL5 is connected to the diodes D13 and D14;

[0047] The anode of the diode D13 is grounded, and the cathode thereof is connected to the input terminal of the inter-stage matching module 3;

[0048] The cathode of the diode D14 is grounded, and the anode thereof is connected to the input end of the inter-stage matching module 3 .

[0049] The first-stage limiting circuit is composed of twelve PIN diodes D1-D12 connected in a series-parallel structure. By increasing the number of series diode pairs from the traditional two parallel branches to four parallel branches, this further ensures that the PIN diodes will not be damaged by excessive power while effectively increasing the heat dissipation area, significantly improving the power capacity of the low-noise amplifier.

[0050] The above-mentioned second-stage limiting circuit is composed of two PIN diodes D13-D14 connected in parallel. The short-circuited transmission line TL4 not only participates in the inter-stage matching of the two-stage limiting circuit, but also provides zero bias gate voltage for the transistor M1 in the first-stage amplifier circuit A1 of the subsequent low-noise amplifier module 3.

[0051] Inductors L1 and L2 are connected in parallel with the two PIN diode branches, respectively, making the first-stage limiting circuit equivalent to an ideal open circuit at small signals. This can reduce its insertion loss while maintaining the high power capacity of the first-stage limiting circuit, thereby further reducing the overall circuit noise.

[0052] Further, such as Figure 2 As shown, the inter-stage matching module 3 includes transmission lines TL6, TL7, and TL8;

[0053] One end of the transmission line TL6 serves as the input end of the inter-stage matching module 3 and is connected to one end of the transmission line TL5, diodes D13, and D14 respectively. The other end of the transmission line TL6 is connected to one end of the transmission lines TL7 and TL8.

[0054] The other end of the transmission line TL7 is suspended, and the other end of the transmission line TL8 is connected to the input end of the low noise amplifier module 4;

[0055] Further, such as Figure 2 As shown, the low noise amplification module 4 includes: a first stage amplification circuit A1 and a second stage amplification circuit A2;

[0056] The input end of the first stage amplifier circuit A1 is connected to the output end of the inter-stage matching module 3; the output end of the second stage amplifier circuit A2 is connected to the input end of the output matching module 5; the output end of the first stage amplifier circuit A1 is connected to the input end of the second stage amplifier circuit A2.

[0057] Further, such as Figure 2 As shown, the first stage amplifier circuit A1 includes: transistors M1, M2, resistors R1-R7, capacitors C2-C7, transmission lines TL9-TL12, and a DC voltage source Vd;

[0058] The gate of transistor M1 is connected to the output end of the inter-stage matching module 3, the source is connected to one end of the first parallel branch formed by capacitor C2 and resistor R1, and the drain is connected to one end of the transmission line TL9; and the other end of the first parallel branch is grounded;

[0059] The gate of transistor M2 is connected to one end of capacitor C3 and resistor R2 respectively, the source is connected to the other end of transmission line TL9, and the drain is connected to one end of transmission line TL10; the other end of capacitor C3 is grounded;

[0060] The other end of the resistor R2 is respectively connected to the resistor R3, the second parallel branch formed by the resistor R4 and the capacitor C5, and one end of the resistor R5; the other end of the second parallel branch is grounded;

[0061] The other end of the resistor R3 is connected to one end of the capacitor C4; the other end of the capacitor C4 is grounded;

[0062] The other end of the resistor R5 is connected to one end of the resistor R6 and the positive electrode of the DC voltage source Vd respectively;

[0063] The other end of the resistor R6 is connected to one end of the capacitor C6; the other end of the capacitor C6 is grounded;

[0064] The other end of the transmission line TL10 is connected to one end of the transmission line TL11 and the input end of the second-stage amplifier A2; the other end of the transmission line TL11 is connected to the resistor R7 and one end of the transmission line TL12; the other end of the resistor R7 is connected to one end of the capacitor C7; the other end of the capacitor C7 is grounded; the other end of the transmission line TL12 is connected to the positive electrode of the DC voltage source Vd.

[0065] Further, such as Figure 2 As shown, the second stage amplifier circuit A2 includes: a transistor M3, resistors R8-R11, capacitors C8-C12, and transmission lines TL13-TL17;

[0066] The gate of transistor M3 is connected to capacitor C8 and one end of transmission lines TL13 and TL14, the source is connected to one end of a third parallel branch formed by capacitor C10 and resistor R11, and the drain is connected to one end of transmission line TL15; the other end of the third parallel branch is grounded;

[0067] The other end of capacitor C8 is the input end of the second stage amplifier circuit A2, and is connected to the output end of the first stage amplifier circuit A1;

[0068] The other end of the transmission line TL13 is connected to one end of the resistors R8 and R9; the other end of the resistor (R9) is grounded;

[0069] The other end of the resistor R8 is connected to the capacitor C9; the other end of the capacitor (C9) is grounded;

[0070] The other end of the transmission line TL14 is connected to the resistor R10 and then connected in series with the capacitor C11;

[0071] The other end of capacitor C11 is connected to one end of transmission lines TL15, TL16, and TL18 (devices of output matching module 5);

[0072] The other end of the transmission line TL16 is connected to the resistor R12 and the transmission line TL17;

[0073] The other end of the resistor R12 is connected to the capacitor C12; the other end of the capacitor C12 is grounded;

[0074] The other end of the transmission line TL17 is connected to the positive electrode of the DC voltage source Vd;

[0075] The transistors (M1, M2, M3) are all coplanar waveguide transistors.

[0076] The first-stage amplifier circuit A1 adopts a common-source common-gate structure design, which reduces the capacitive feedback between the transistor input and output, increases the output impedance of this stage of the amplifier, and effectively improves the high-frequency gain of the entire low-noise amplifier.

[0077] Furthermore, if Figure 2As shown, the output stage matching circuit 5 includes a transmission line TL16, and the transmission line TL16, resistor R12, capacitors C12 and C13 of the second stage amplifier circuit A2;

[0078] The output stage matching circuit 5 has some overlapped components with the second stage amplifier circuit A2, because some components on the DC bias network of the second stage amplifier circuit A2 participate in the output matching;

[0079] One end of the transmission line TL18 is connected to the transmission lines TL15 and TL16 and the capacitor C11, and the other end is connected to the capacitor C13; the other end of the capacitor C13 is connected to the RF signal output terminal OUT;

[0080] As an important application of the K-band limiting low noise amplifier of the present invention, the present invention also provides a radio frequency chip of a 20-30GHz limiting low noise amplifier, whose circuit structure is the same as that of the above-mentioned K-band limiting low noise amplifier. The chip fully utilizes the corresponding beneficial effects and effects of the above-mentioned limiting low noise amplifier.

[0081] Figure 3 A comparison chart of the insertion loss simulation results of the PIN diode limiter provided for the 20-30 GHz limiting low noise amplifier of the embodiment of the present invention is shown. The vertical axis is: IL (Insertion Loss) in decibels (dB), and the horizontal axis is: Freq (GHz) frequency. This simulation compares the insertion loss curves before and after the inductors L1 and L2 (solid line) are connected in parallel with the two diode branches (dotted solid line). Without parallel inductors L1 and L2: the insertion loss is large, and the in-band insertion loss flatness is poor, with the high-low difference reaching 1.2dB. With parallel inductors L1 and L2: the insertion loss is significantly reduced, especially at high and low frequencies, and the in-band insertion loss flatness is effectively improved, with the high-low difference being only 0.35dB. Therefore, it can be seen that the parallel inductors L1 and L2 can significantly reduce their insertion loss and improve the in-band insertion loss flatness.

[0082] Figure 4 This is a simulation graph of the voltage standing wave ratio (VSWR) of a 20-30 GHz limiting low-noise amplifier according to an embodiment of the present invention. The vertical axis is VSWR (voltage standing wave ratio), and the horizontal axis is frequency (GHz). The solid line in the graph represents VSWR_in, the input standing wave ratio, and the dotted solid line represents VSWR_out, the output standing wave ratio. This graph shows how the input and output voltage standing wave ratios of the limiting low-noise amplifier vary with frequency. The voltage standing wave ratio of the limiting low-noise amplifier is less than 1.6 within the passband, indicating good impedance matching performance.

[0083] Figure 5This is a small signal gain simulation diagram of the 20-30 GHz limiting low noise amplifier of the embodiment of the present application; the vertical axis is: Gain (dB) (gain) in decibels (dB), and the horizontal axis is: Freq (GHz); in the figure, the limiting low noise amplifier has a maximum gain of 21.5 dB in the 20-30 GHz frequency band, and the gain curve is relatively flat, indicating that it has stable high-frequency gain.

[0084] Figure 6 This is a simulation graph of the noise figure of a 20-30 GHz limiting low-noise amplifier (LNA) according to an embodiment of the present application. The vertical axis is NF (dB), representing the noise figure in decibels (dB), and the horizontal axis is Freq (GHz). This graph shows how the noise figure of the LNA changes with frequency. The LNA has a noise figure of less than 2.5 dB in the 20-30 GHz frequency band, with a minimum noise figure of 2.1 dB, indicating a low noise level.

[0085] In summary, it can be seen that the maximum gain of the simulated limiting low-noise amplifier is 21.5dB, the operating frequency band is 20GHz to 30GHz, the voltage standing wave ratio in the passband is less than 1.6, the noise figure in the passband is within 2.5dB, and the minimum noise figure is 2.1dB.

[0086] Specifically, the K-band limiting low-noise amplifier provided by the present invention exhibits excellent performance, including high power handling, good impedance matching, high-frequency gain, and low noise. These properties make the amplifier promising for broad application in radio frequency receiving systems, such as radar and satellite communications.

[0087] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0088] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A K-band limiting low noise amplifier, characterized in that: include: An input matching module (1), a diode limiting module (2), an inter-stage matching module (3), a low-noise amplification module (4) and an output matching module (5) are sequentially cascaded; The input matching module (1) is used to achieve impedance matching between the radio frequency signal input terminal (IN) and the diode limiter module (2), and transmit the received radio frequency signal to the diode limiter module (2); The diode limiting module (2) is used to limit the radio frequency signal and transmit the limited radio frequency signal to the inter-stage matching module (3); The inter-stage matching module (3) is used to achieve impedance matching between the diode limiting module (2) and the low-noise amplification module (4), and transmit the limited radio frequency signal to the low-noise amplification module (4); The low-noise amplification module (4) is used to amplify the limited radio frequency signal and transmit it to the output matching module (5); The output matching module (5) is used to achieve impedance matching between the low-noise amplification module (4) and the radio frequency signal output terminal (OUT), and output the amplified radio frequency signal from the radio frequency signal output terminal (OUT); The input matching module (1) comprises: a capacitor C1, a transmission line TL1 and a transmission line TL2; One end of the capacitor C1 is connected to the RF signal input terminal (IN), and the other end is connected to one end of the transmission line TL1 and the transmission line TL2 respectively; The other end of the transmission line TL1 is suspended, and the other end of the transmission line TL2 is connected to the input end of the diode limiter module (2); The diode limiting module (2) comprises: a first-stage limiting circuit, a second-stage limiting circuit, inductors L1 and L2, and transmission lines TL3, TL4, and TL5; The first stage limiting circuit is composed of twelve PIN diodes D1-D12 connected in a series-parallel structure; The second stage limiting circuit is composed of two PIN diodes D13-D14 connected in parallel; The anode of the diode D1 is grounded, and its cathode is connected to the anode of the diode D2. The cathode of the diode D2 is connected to the anode of the diode D3. The cathode of the diode D3 is connected to one end of the transmission lines TL2 and TL3 and the inductors L1 and L2 respectively. The anode of the diode D4 is grounded, and the cathode thereof is connected to the anode of the diode D5. The cathode of the diode D5 is connected to the anode of the diode D6. The cathode of the diode D6 is connected to one end of the transmission lines TL2 and TL3 and the inductors L1 and L2 respectively. The anode of the diode D7 is connected to the transmission lines TL2, TL3 and one end of the inductors L1, L2, and the cathode of the diode D7 is connected to the anode of the diode D8, the cathode of the diode D8 is connected to the anode of the diode D9, and the cathode of the diode D9 is grounded; The anode of the diode D10 is connected to the transmission lines TL2, TL3 and one end of the inductors L1, L2, and the cathode is connected to the anode of the diode D11, the cathode of the diode D11 is connected to the anode of the diode D12, and the cathode of the diode D12 is grounded; The other ends of the inductors L1 and L2 are grounded; The other end of the transmission line TL3 is connected to the transmission lines TL4 and TL5, the other end of the transmission line TL4 is grounded, and the other end of the transmission line TL5 is connected to the cathode of the diode D13 and the anode of D14 respectively; The anode of the diode D13 is grounded, and the cathode thereof is connected to the input end of the inter-stage matching module (3); The cathode of the diode D14 is grounded, and the anode thereof is connected to the input end of the inter-stage matching module (3).

2. A K-band limiting low noise amplifier according to claim 1, characterized in that: The inter-stage matching module (3) comprises: transmission lines TL6, TL7, and TL8; One end of the transmission line TL6 serves as the input end of the inter-stage matching module (3), and the other end is connected to one end of the transmission lines TL7 and TL8 respectively; The other end of the transmission line TL7 is suspended, and the other end of the transmission line TL8 is connected to the input end of the low-noise amplifier module (4).

3. The K-band limiting low noise amplifier according to claim 1, wherein: The low-noise amplification module (4) comprises: a first-stage amplification circuit A1 and a second-stage amplification circuit A2; The input end of the first-stage amplifier circuit A1 is connected to the output end of the inter-stage matching module (3); The output end of the first stage amplifier circuit A1 is connected to the input end of the second stage amplifier circuit A2; The output end of the second-stage amplifier circuit A2 is connected to the input end of the output matching module (5).

4. The K-band limiting low noise amplifier according to claim 3, characterized in that: The first-stage amplifier circuit A1 includes: transistors M1, M2, resistors R1-R7, capacitors C2-C7, transmission lines TL9-TL12, and a DC voltage source (Vd); The gate of the transistor M1 is connected to the output end of the inter-stage matching module (3), the source is connected to one end of a first parallel branch formed by the capacitor C2 and the resistor R1, and the drain is connected to one end of the transmission line TL9; the other end of the first parallel branch is grounded; The gate of the transistor M2 is connected to one end of the capacitor C3 and the resistor R2 respectively, the source is connected to the other end of the transmission line TL9, and the drain is connected to one end of the transmission line TL10; The other end of the capacitor C3 is grounded; The other end of the resistor R2 is respectively connected to the resistor R3, the second parallel branch formed by the resistor R4 and the capacitor C5, and one end of the resistor R5; The other end of the resistor R3 is connected to one end of the capacitor C4; the other end of the capacitor C4 is grounded; The other end of the second parallel branch is grounded; The other end of the resistor R5 is connected to one end of the resistor R6 and the positive electrode of the DC voltage source (Vd); The other end of the resistor R6 is connected to one end of the capacitor C6; the other end of the capacitor C6 is grounded; The other end of the transmission line TL10 is connected to one end of the transmission line TL11 and the input end of the second stage amplifier A2 respectively; The other end of the transmission line TL11 is connected to the resistor R7 and one end of the transmission line TL12; The other end of the resistor R7 is connected to one end of the capacitor C7; the other end of the capacitor C7 is grounded; The other end of the transmission line TL12 is connected to the positive electrode of the DC voltage source (Vd).

5. The K-band limiting low noise amplifier according to claim 4, characterized in that: The second stage amplifier circuit A2 includes: a transistor M3, resistors R8-R12, capacitors C8-C12, and transmission lines TL13-TL17; The gate of the transistor M3 is connected to the capacitor C8 and one end of the transmission lines TL13 and TL14 respectively, the source is connected to one end of a third parallel branch formed by the capacitor C10 and the resistor R11, and the drain is connected to one end of the transmission line TL15; the other end of the third parallel branch is grounded; The other end of the capacitor C8 serves as the input end of the second-stage amplifier circuit A2 and is connected to the output end of the first-stage amplifier circuit A1; The other end of the transmission line TL13 is connected to one end of the resistors R8 and R9 respectively; The other end of the resistor R8 is connected to one end of the capacitor C9; the other end of the capacitor C9 is grounded; the other end of the resistor R9 is grounded; The other end of the transmission line TL14 is connected to the resistor R10 and then connected in series with the capacitor C11; The other end of the capacitor C11 is connected to the other end of the transmission line TL15 and one end of the transmission line TL16 respectively; The other end of the transmission line TL16 is connected to one end of the transmission line TL17 and the resistor R12 respectively; The other end of the resistor R12 is connected to one end of the capacitor C12; the other end of the capacitor C12 is grounded; The other end of the transmission line TL17 is connected to the positive electrode of the DC voltage source Vd.

6. The K-band limiting low noise amplifier according to claim 5, characterized in that: The transistors M1 , M2 , and M3 are all coplanar waveguide transistors.

7. The K-band limiting low noise amplifier according to claim 6, characterized in that: The output matching module 5 includes a transmission line TL18 and a transmission line TL16 of the second stage amplifier circuit A2, a resistor R12, and capacitors C12 and C13; One end of the transmission line TL18 is connected to the other end of the transmission line TL15, one end of the transmission line TL16, and the other end of the capacitor C11, and the other end of the transmission line TL18 is connected to one end of the capacitor C13; The other end of the capacitor C13 is connected to the RF signal output end (OUT).

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