A radio frequency receive front-end circuit with a shielded cavity

Abstract

The application discloses a radio frequency receiving front-end circuit with a shielding cavity and relates to the technical field of radio. The radio frequency receiving front-end circuit comprises a signal processing link, a power supply processing module, a shielding cavity and an interface assembly. The signal processing link and the power supply processing module are integrated on a PCB board. A middle cavity in the shielding cavity is internally provided with a positioning column and a threaded mounting hole for fixing the PCB board. The PCB board is clamped between the middle cavity and a lower cover plate through a cover plate screw. An SMA interface in the interface assembly is connected with a T1 radio frequency amplifier in the signal processing link in input mode. An SMA connector in the interface assembly is connected with a second intermediate frequency filter in the signal processing link in output mode. A U1 first mixer in the signal processing link is connected with an LO1 first local oscillator SMA connector in cooperation. The radio frequency receiving front-end circuit with the shielding cavity has excellent shielding performance, guarantees high-frequency signal integrity and realizes uniform heat dissipation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radio technology, in particular to a radio frequency receiving front-end circuit with a shielding cavity. BACKGROUND

[0002] In modern electronic systems such as wireless communication, radar detection, satellite navigation and radio frequency measurement, the radio frequency receiving system as the core front-end directly determines the sensitivity, dynamic range and signal quality of the whole system. However, with the continuous increase of the application frequency band, especially in the microwave frequency band such as Ku band (10.7GHz-12.7GHz), the receiver system faces multiple severe challenges in design and implementation: the low-noise amplifier needs to balance low noise and high gain under high frequency broadband; the mixer needs to achieve high linearity and low conversion loss under high local oscillator frequency; the filter network needs to have steep out-of-band suppression to resist strong image and adjacent channel interference; in addition, the whole link needs to solve the problems of electromagnetic shielding, thermal management and impedance matching in a limited volume to achieve high isolation, high stability and good producibility. SUMMARY

[0003] The purpose of the present application is to provide a radio frequency receiving front-end circuit with a shielding cavity, to improve the electrical performance index, to provide excellent shielding effectiveness, to ensure high frequency signal integrity, and to achieve uniform heat dissipation.

[0004] The present application provides a radio frequency receiving front-end circuit with a shielding cavity, comprising a signal processing link, a power supply processing module, a shielding cavity and an interface assembly; the signal processing link and the power supply processing module are integrated on a PCB board, the middle cavity in the shielding cavity is internally provided with a positioning column and a threaded mounting hole to fix the PCB board, and the PCB board is clamped between the middle cavity and the lower cover plate through a cover plate screw; the SMA interface in the interface assembly is input connected to the T1 radio frequency amplifier in the signal processing link; the SMA connector in the interface assembly is output connected to the second intermediate frequency filter in the signal processing link; the U1 first mixer in the signal processing link is connected in cooperation with the LO1 first local oscillator SMA connector, and the U2 second mixer 10 in the signal processing link is connected in cooperation with the LO2 second local oscillator SMA connector; the 6V power supply input connector in the interface assembly is connected to the FB7 magnetic bead and the FB8 magnetic bead in the signal processing link.

[0005] Preferably, the signal processing link comprises a T1 radio frequency amplifier, a F1 radio frequency filter, a U1 first mixer, a F4 filter, a T2 first intermediate frequency amplifier, a F3 first intermediate frequency filter, a B1 fixed attenuator, a U2 second mixer, R1, R2, R3 constitute a Pi attenuator, a F2 filter, a T3 second intermediate frequency amplifier, a X3 IPEX connector and a second intermediate frequency filter; the T1 radio frequency amplifier is connected in turn with the F1 radio frequency filter, the U1 first mixer, the F4 filter, the T2 first intermediate frequency amplifier, the F3 first intermediate frequency filter, the B1 fixed attenuator, the U2 second mixer, R1, R2, R3 constitute a Pi attenuator, the F2 filter, the T3 second intermediate frequency amplifier and the second intermediate frequency filter.

[0006] Preferably, the power supply processing module comprises FB7 magnetic beads and FB8 magnetic beads, FU1 fuse, D1 TVS diode, D2 rectifier diode, voltage stabilizing chip one, voltage stabilizing chip two, voltage stabilizing chip three, 5V test point one, 5V test point two and 5V test point three; the FB7 magnetic beads and the FB8 magnetic beads are connected in turn with the FU1 fuse, the D1 TVS diode, the D2 rectifier diode, the voltage stabilizing chip one, the voltage stabilizing chip two, the voltage stabilizing chip three, the 5V test point one, the 5V test point two and the 5V test point three.

[0007] Preferably, the interface assembly comprises an SMA interface input, a LO1 first local oscillator, a LO2 second local oscillator, an SMA connector output and a 6V power supply input connector; the SMA interface input, the SMA connector output, the LO1 first local oscillator SMA connector, the LO2 second local oscillator SMA connector and the 6V power supply input connector in the interface assembly are located on the outer side of the middle cavity.

[0008] Preferably, the shielding cavity comprises an upper cover plate, a middle cavity, a lower cover plate, cover plate screws, a middle cavity upper surface, a first frequency band cavity, a second frequency band cavity, SMA screw holes, a third frequency band cavity, a first slotted hole and a second slotted hole; the top of the middle cavity is the middle cavity upper surface, and the lower surface of the upper cover plate completely matches the middle cavity upper surface; the edges of the upper cover plate and the middle cavity are provided with corresponding screw holes, and the cover plate screws uniformly pass through the screw holes of the upper cover plate and the middle cavity; the middle cavity lower surface, the first slotted hole and the second slotted hole are processed by a milling cutter to be 1mm; the lower cover plate and the cover plate screws are M2 stainless steel cross countersunk screws.

[0009] Preferably, the bottom of the middle cavity is the middle cavity lower surface, and the upper surface of the lower cover plate completely matches the middle cavity lower surface; the edges of the lower cover plate are also provided with screw holes corresponding to the edges of the middle cavity, and the cover plate screws pass through the screw holes of the lower cover plate and the middle cavity; the SMA screw holes are provided on the side wall of the middle cavity, and the SMA screw holes are four-hole flange structures; the first slotted hole and the second slotted hole are provided on the lower surface of the middle cavity.

[0010] Therefore, the application adopts the above-mentioned radio frequency receiving front-end circuit with shielding cavity to improve the electrical performance index, provide excellent shielding performance, ensure high frequency signal integrity, and realize uniform heat dissipation.

[0011] The technical solutions of the application are described in further detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 Figure 1 is a PCB radio frequency surface schematic diagram of the radio frequency receiving front-end circuit with shielding cavity of the application;

[0013] Figure 2 Figure 2 is a PCB power supply surface schematic diagram of the radio frequency receiving front-end circuit with shielding cavity of the application;

[0014] Figure 3 Figure 3 is a shielding cavity top view of the radio frequency receiving front-end circuit with shielding cavity of the application;

[0015] Figure 4 Figure 4 is a shielding cavity bottom view of the radio frequency receiving front-end circuit with shielding cavity of the application;

[0016] Figure 5 Figure 5 is an intermediate cavity upper surface perspective schematic diagram of the radio frequency receiving front-end circuit with shielding cavity of the application;

[0017] Figure 6 Figure 6 is an intermediate cavity lower surface perspective schematic diagram of the radio frequency receiving front-end circuit with shielding cavity of the application.

[0018] REFERENCE NUMERALS

[0019] 1, SMA joint input; 2, T1 radio frequency amplifier; 3, F1 radio frequency filter; 4, U1 first mixer; 5, LO1 first local oscillator SMA joint; 6, F4 filter; 7, T2 first intermediate frequency amplifier; 8, F3 first intermediate frequency filter; 9, B1 fixed attenuator; 10, U2 second mixer; 11, LO2 second local oscillator SMA joint; 12, R1, R2, R3 constitute Pi type attenuator; 13, F2 filter; 14, T3 second intermediate frequency amplifier; 15, X3 IPEX connector; 16, second intermediate frequency filter; 17. SMA joint output; 18, 6V power input joint; 19, FB7 and FB8 magnetic beads; 20, FU1 fuse; 21, D1 TVS diode; 22, D2 rectifier diode; 23, voltage stabilizing chip one; 24, voltage stabilizing chip two; 25, voltage stabilizing chip three; 26, 5V test point one; 27, 5V test point two; 28, 5V test point three; 29, upper cover plate; 30, middle cavity; 31, lower cover plate; 32, cover plate screw; 33, middle cavity upper surface; 34, first frequency band cavity; 35, second frequency band cavity; 36, SMA screw hole; 37, third frequency band cavity; 38, first slot hole; 39, second slot hole; 40, middle cavity lower surface. DETAILED DESCRIPTION

[0020] The technical solutions of the present application are further described below by means of the drawings and examples.

[0021] Unless otherwise defined, the technical terms or scientific terms used in the present application shall be understood as the usual meaning understood by those skilled in the art to which the present application belongs.

[0022] The "first", "second" and similar words used in the present application do not represent any order, quantity or importance, but are only used to distinguish different components. "Include" or "contain" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connected" or "connected" and similar words are not limited to physical or mechanical connection, but can include electrical connection, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to represent the relative positional relationship, when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0023] Example one

[0024] As Figures 1-6As shown, the radio frequency receiving front-end circuit with a shielding cavity includes a signal processing link, a power supply processing module, a shielding cavity, and an interface assembly; the signal processing link and the power supply processing module are integrated on a PCB board, a middle cavity 33 in the shielding cavity is internally provided with a positioning column and a threaded mounting hole to fix the PCB board, and the PCB board is clamped between the middle cavity 33 and a lower cover plate 31 through a cover plate screw. The PCB board adopts a four-layer high-performance microwave board material Rogers RO4350B circuit board. The radio frequency surface is responsible for the main signal flow, and the power supply surface (and the bottom layer) adopts a complete plane design to provide low-noise, stable power supply and good grounding for the radio frequency components.

[0025] The upper cover plate 29, the middle cavity 30, and the lower cover plate 31 are uniformly fastened as a whole through the cover plate screw 32 to form a three-layer closed structure, completely wrap the PCB board carrying the signal processing link and the power supply processing module therein, and construct a Faraday cage type electromagnetic shielding space to block external electromagnetic interference and internal signal leakage. The radio frequency grounding layer of the PCB board is tightly connected with the metal body of the middle cavity 30 through a grounding via array to realize low-impedance grounding and guarantee the signal integrity of the signal processing link.

[0026] The power supply layer of the power supply processing module cooperates with the cavity grounding structure, suppresses high-frequency power supply noise by using FB7 and FB8 magnetic beads 19 and other components, and provides clean power supply for the signal processing link. The cavity metal body also serves as a heat sink, and the heat of the heating components on the PCB board is conducted to the outside through the PCB grounding layer, the internal air of the cavity, and the cavity metal body, thereby solving the heat dissipation problem of the high-frequency circuit.

[0027] The isolation wall in the middle cavity 30 divides a first frequency band cavity 34, a second frequency band cavity 35, and a third frequency band cavity 37 corresponding to different processing stages of the signal processing link; and the signal paths of different frequency bands on the PCB board are transmitted across the cavities through a first slotted hole 38 and a second slotted hole 39 of the middle cavity, which not only guarantees the electrical integrity of the signal path, but also avoids crosstalk between signals of different frequency bands through the physical isolation wall.

[0028] The SMA interface input 1 in the interface assembly is connected to the T1 radio frequency amplifier 2 in the signal processing link; the SMA connector output 17 in the interface assembly is connected to the second intermediate frequency filter 16 in the signal processing link; and the U1 first mixer 4 in the signal processing link is connected in cooperation with the LO1 first local oscillator SMA connector 5 to convert the Ku-band radio frequency signal into a first intermediate frequency signal.

[0029] The U2 second mixer 10 in the signal processing link cooperates with the LO2 second local oscillator SMA joint 11; the first intermediate frequency signal is down-converted to the L-band second intermediate frequency signal. The 6V power input joint 18 in the interface assembly connects the FB7 magnetic bead and the FB8 magnetic bead 19 in the signal processing link. The signal processing link includes T1 radio frequency amplifier 2, F1 radio frequency filter 3, U1 first mixer 4, F4 filter 6, T2 first intermediate frequency amplifier 7, F3 first intermediate frequency filter 8, B1 fixed attenuator 9, U2 second mixer 10, R1, R2, R3 constitute Pi type attenuator 12, F2 filter 13, T3 second intermediate frequency amplifier 14, X3 IPEX connector 15 and second intermediate frequency filter 16; T1 radio frequency amplifier 2 is connected in turn F1 radio frequency filter 3, U1 first mixer 4, F4 filter 6, T2 first intermediate frequency amplifier 7, F3 first intermediate frequency filter 8, B1 fixed attenuator 9, U2 second mixer 10, R1, R2, R3 constitute Pi type attenuator 12, F2 filter 13, T3 second intermediate frequency amplifier 14 and second intermediate frequency filter 16. X3 IPEX connector 15 provides debugging support for second intermediate frequency filter 16 and subsequent output link.

[0030] The radio frequency signal (10.7GHz-12.7GHz) is input through the SMA joint 1, passes through the T1 radio frequency amplifier 2, the signal is amplified by 22dB, and then passes through the F1 radio frequency filter 3. The F1 radio frequency filter 3 is a ceramic patch filter, which filters the input signal in the frequency range of (10.7GHz-12.7GHz) to filter out the input spurs. At the same time, for the radio frequency signal and the local oscillator signal (15GHz-16.7GHz) input through the LO1 first local oscillator SMA joint 5, the mirror spurious signal except the first intermediate frequency signal (4GHz-4.3GHz) generated by the U1 first mixer 4 is suppressed.

[0031] The first intermediate frequency signal (4GHz-4.3GHz) passes through the F4 filter 6 with a frequency range of (DC-10GHz), aiming to prevent the leakage of the local oscillator signal input by the LO1 first local oscillator SMA joint 5 along the link to the next stage. The first intermediate frequency signal (4GHz-4.3GHz) passes through the T2 first intermediate frequency amplifier 7, the signal is amplified by 20dB, and then passes through the F3 first intermediate frequency filter 8, which filters the first intermediate frequency signal in the frequency range of (4GHz~4.3GHz). The B1 fixed attenuator 9 is used to protect the U2 second mixer 10, ensuring that the power of the first intermediate frequency signal (4GHz~4.3GHz) reaching the U2 second mixer 10 interface is within the safe and linear working range, and the (5.15GHz) signal input by the LO2 second local oscillator SMA joint 11 is up-converted by the U2 second mixer 10, outputting the second intermediate frequency signal (0.85GHz~1.15GHz). The R1, R2, and R3 constitute a Pi-type attenuator 12 to improve port isolation. The output second intermediate frequency signal (0.85GHz~1.15GHz) passes through the F2 filter 13 with a frequency range of (DC~10GHz), aiming to prevent the leakage of the local oscillator signal input by the LO2 second local oscillator SMA joint 11 along the link to the next stage. The second intermediate frequency signal (0.85GHz~1.15GHz) passes through the T3 second intermediate frequency amplifier 14, the signal is amplified by 24dB, and then further passes through the second intermediate frequency filter 16 (0.85GHz~1.15GHz), and is output via the SMA joint 17.

[0032] The IPEX connector 15 is a debugging interface reserved for the second intermediate frequency filter 16 (0.85GHz~1.15GHz).

[0033] The total gain G of the receiving system in the index:

[0034] ;

[0035] Where, Gi is the gain (dB) of the i-th active device, Pi is the loss (dB) of the i-th passive device;

[0036] The noise figure NF of the receiving system in the index:

[0037] ;

[0038] The 1dB compression point P-1dB of the receiving system in the index:

[0039] ;

[0040] The OIP3 of the receiving system in the index:

[0041] ;

[0042] After calculation, high gain (40dB), low noise factor (2dB), high linearity (OIP325dBm), image and spurious suppression (≥50dBc) are all within the range of the index requirements.

[0043] The power supply processing module includes FB7 and FB8 magnetic beads 19, FU1 fuse 20, D1 TVS diode 21, D2 rectifier diode 22, voltage stabilizing chip one 23, voltage stabilizing chip two 24, voltage stabilizing chip three 25, 5V test point one 26, 5V test point two 27 and 5V test point three 28; the FB7 and FB8 magnetic beads 19 are connected with FU1 fuse 20, D1 TVS diode 21, D2 rectifier diode 22, voltage stabilizing chip one 23, voltage stabilizing chip two 24, voltage stabilizing chip three 25, 5V test point one 26, 5V test point two 27 and 5V test point three 28 in sequence.

[0044] The power supply surface of the PCB board, the 6V power supply signal is input through the 6V power supply connector 18, and the FB7 and FB8 magnetic beads 19 are used to prevent high-frequency noise from being propagated on the ground network, so as to provide a more pure reference ground for the radio frequency system. The 6V power supply signal passes through FU1 fuse 20, which is used to protect the circuit. If a short circuit, serious overload or other faults occur in the rear-end circuit, the current will increase rapidly, and FU1 fuse 20 will melt rapidly. The 6V power supply signal passes through D1 TVS diode 21 for overvoltage protection, and passes through D2 rectifier diode 22 for reverse polarity protection. The 6V power supply signal passes through voltage stabilizing chip one 23, and outputs a 5V signal, which is used to power T1 radio frequency amplifier 2, and 5V test point one 26 is used to test whether it meets the requirements; the 6V power supply signal passes through voltage stabilizing chip two 24, and outputs a 5V signal, which is used to power T2 first intermediate frequency amplifier 7, and 5V test point two 27 is used to test whether it meets the requirements; the 6V power supply signal passes through voltage stabilizing chip three 25, and outputs a 5V signal, which is used to power T3 second intermediate frequency amplifier 14, and 5V test point three 28 is used to test whether it meets the requirements.

[0045] The interface assembly includes SMA interface input 1, LO1 first local oscillator 5, LO second local oscillator 11, SMA connector output 17, 6V power supply input connector 18; the SMA interface input 1, SMA connector output 17, LO1 first local oscillator SMA connector 5, LO2 second local oscillator SMA connector 11 and power supply input connector 18 in the interface assembly are located on the outside of the middle cavity 32.

[0046] Shielding cavity includes upper cover plate 31, middle cavity 32, lower cover plate 33, cover plate screw 34, middle cavity upper surface 35, first frequency band cavity 36, second frequency band cavity 37, SMA screw hole 38, third frequency band cavity 39, first slot hole 40, second slot hole 41, middle cavity lower surface 42.

[0047] The top of the middle cavity 30 is the middle cavity upper surface 33, and the lower surface of the upper cover plate 31 completely matches the middle cavity upper surface 33; the edges of the upper cover plate 29 and the middle cavity 30 are both provided with corresponding screw holes, and the cover plate screws 32 (M2 stainless steel cross countersunk screws) uniformly penetrate the screw holes of the upper cover plate 29 and the middle cavity 30, and are fastened by multiple points to ensure that there is no gap between the upper cover plate 29 and the middle cavity 30, thereby avoiding electromagnetic leakage.

[0048] The bottom of the middle cavity 30 is the middle cavity lower surface 40 (a flat structure), and the upper surface of the lower cover plate 31 completely matches the middle cavity lower surface 40; the edges of the lower cover plate 31 are also provided with screw holes corresponding to the edges of the middle cavity 30, and the cover plate screws 32 penetrate the screw holes of the lower cover plate 31 and the middle cavity 30, which is consistent with the fastening mode of the upper cover plate 29, thereby realizing the seamless connection of the middle cavity 30 and the lower cover plate 31; at the same time, the PCB board carrying the signal processing link and the power supply processing module is clamped and fixed between the middle cavity lower surface 40 and the lower cover plate 31, and the positioning column and the threaded mounting hole in the middle cavity 30 can further accurately fix the PCB board, thereby ensuring the relative position stability of the PCB board and the middle cavity 30 (avoiding poor contact caused by vibration).

[0049] The upper cover plate 29, the middle cavity 30 and the lower cover plate 31 form a rigid whole through the cover plate screws 32, and all of them are made of AL6061-T6 aluminum alloy material (surface natural color conductive oxidation), which not only ensures the structural strength (adaptation to harsh environment anti-vibration / impact), but also realizes good electrical contact through the metal contact surface, thereby constituting a complete Faraday cage and realizing electromagnetic shielding.

[0050] The middle cavity 30 is provided with multiple metal isolation walls perpendicular to the middle cavity upper surface 33 / lower surface 40, which divides the internal space of the middle cavity 30 into three independent closed sub-cavities, and the three sub-cavities all penetrate the middle cavity upper surface 33 to the middle cavity lower surface 40, and are closed with the outside through the upper cover plate 29 and the lower cover plate 31.

[0051] The first frequency band cavity 34 is used for accommodating Ku band input modules (T1 radio frequency amplifier 2, F1 radio frequency filter 3, etc.) of a signal processing chain, and is physically isolated from other sub-cavities through an isolation wall to avoid Ku band signal interference with other frequency bands. The second frequency band cavity 35 is used for accommodating first intermediate frequency modules (U1 first mixer 4, T2 first intermediate frequency amplifier 7, etc.) of the signal processing chain, and carries 4-4.3 GHz intermediate frequency signal processing. The third frequency band cavity 37 is used for accommodating second intermediate frequency / L band modules (U2 second mixer 10, T3 second intermediate frequency amplifier 14, etc.) of the signal processing chain, and carries 0.85-1.15 GHz signal processing.

[0052] The side wall (a surface perpendicular to the upper surface 35 of the intermediate cavity and the lower surface 40 of the intermediate cavity) of the intermediate cavity 30 and the lower surface 40 of the intermediate cavity are provided with two types of functional holes, which are an integral structure of the intermediate cavity 32.

[0053] The SMA screw hole 36 is provided in the side wall of the intermediate cavity 30 and has a four-hole flange structure, which is used for fixing external SMA joints (such as SMA interface input 1 and SMA joint output 17) to ensure that the inner conductor of the SMA joint is accurately connected with the circuit (such as a radio frequency port on a PCB) in the sub-cavity inside the intermediate cavity 30, and at the same time, the flange structure ensures impedance matching and mechanical stability.

[0054] The first slotted hole 38 and the second slotted hole 39 are provided in the lower surface 40 of the intermediate cavity and are long strip holes with a width of 1 mm, which are used for allowing signal lines on the PCB to pass through the sub-cavities (such as a signal path from the first frequency band cavity 34 to the second frequency band cavity 35), thereby ensuring electrical continuity of the signals and reducing electromagnetic leakage between different sub-cavities through the narrow gap design of the slotted holes.

[0055] Therefore, the application adopts the above-mentioned radio frequency receiving front-end circuit with a shielding cavity, optimizes the two-stage down-conversion, multi-stage filtering and amplification chain architecture, and combines fixed and variable attenuators to perform fine level management, thereby improving electrical performance indicators. The shielding cavity structure of the upper cover plate, the intermediate cavity and the lower cover plate divides the cavity into multiple independent sub-chambers through an isolation wall, provides excellent shielding performance, and ensures high-frequency signal integrity. Uniform heat dissipation is achieved.

[0056] The above embodiments are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A radio frequency receiving front-end circuit with a shielded cavity, characterized in that, The system includes a signal processing link, a power processing module, a shielded cavity, and interface components. The signal processing link and power processing module are integrated on a PCB board. The shielded cavity has positioning posts and threaded mounting holes inside the middle cavity to fix the PCB board. The PCB board is clamped between the middle cavity and the lower cover plate by cover plate screws. The SMA interface input in the interface component connects to the T1 RF amplifier in the signal processing link. The SMA connector output in the interface component connects to the second intermediate frequency filter in the signal processing link. The U1 first mixer in the signal processing link connects to the LO1 first local oscillator SMA connector, and the U2 second mixer in the signal processing link connects to the LO2 second local oscillator SMA connector. The 6V power input connector in the interface component connects to the FB7 and FB8 ferrite beads in the signal processing link. The shielded cavity includes an upper cover plate, a middle cavity, a lower cover plate, cover plate screws, an upper surface of the middle cavity, and a first frequency band. The cavity comprises: a second-band cavity, SMA screw holes, a third-band cavity, a first slotted hole, a second slotted hole, and a lower surface of the intermediate cavity; the top of the intermediate cavity is its upper surface, and the lower surface of the upper cover plate is completely flush with the upper surface of the intermediate cavity; corresponding screw holes are provided on the edges of the upper cover plate and the intermediate cavity, and the cover plate screws evenly penetrate the screw holes of the upper cover plate and the intermediate cavity; the lower surface of the intermediate cavity, the first slotted hole, and the second slotted hole are machined 1mm using a milling cutter; the lower cover plate and cover plate screws are M2 stainless steel Phillips head countersunk screws; the bottom of the intermediate cavity is its lower surface, and the upper surface of the lower cover plate is completely flush with the lower surface of the intermediate cavity; the edge of the lower cover plate also has screw holes corresponding to the edge of the intermediate cavity, and the cover plate screws penetrate the screw holes of the lower cover plate and the intermediate cavity; SMA screw holes are opened on the side wall of the intermediate cavity, and the SMA screw holes are four-hole flange structures; the first slotted hole and the second slotted hole are opened on the lower surface of the intermediate cavity.

2. The radio frequency receiving front-end circuit with a shielded cavity according to claim 1, characterized in that, The signal processing link includes a T1 RF amplifier, an F1 RF filter, a U1 first mixer, an F4 filter, a T2 first IF amplifier, an F3 first IF filter, a B1 fixed attenuator, a U2 second mixer, R1, R2, and R3 forming a Pi-type attenuator, an F2 filter, a T3 second IF amplifier, an X3 IPEX connector, and a second IF filter. The T1 RF amplifier is sequentially connected to the F1 RF filter, the U1 first mixer, the F4 filter, the T2 first IF amplifier, the F3 first IF filter, the B1 fixed attenuator, the U2 second mixer, R1, R2, and R3 forming a Pi-type attenuator, the F2 filter, the T3 second IF amplifier, and the second IF filter.

3. The radio frequency receiving front-end circuit with a shielded cavity according to claim 1, characterized in that, The power processing module includes FB7 and FB8 ferrite beads, FU1 fuse, D1 TVS diode, D2 rectifier diode, voltage regulator chip one, voltage regulator chip two, voltage regulator chip three, 5V test point one, 5V test point two, and 5V test point three; FB7 and FB8 ferrite beads are connected in sequence to FU1 fuse, D1 TVS diode, D2 rectifier diode, voltage regulator chip one, voltage regulator chip two, voltage regulator chip three, 5V test point one, 5V test point two, and 5V test point three.

4. The radio frequency receiving front-end circuit with a shielded cavity according to claim 1, characterized in that, The interface assembly includes an SMA interface input, LO1 first local oscillator, LO2 second local oscillator, SMA connector output, and 6V power input connector; the SMA interface input, SMA connector output, LO1 first local oscillator SMA connector, LO2 second local oscillator SMA connector, and 6V power input connector in the interface assembly are located on the outside of the intermediate cavity.

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