Broadband impedance matching filtering high-pass circuit based on 75-ohm system

Abstract

The utility model provides a broadband impedance matching filtering high-pass circuit based on a 75 ohm system, which comprises a PCB (printed circuit board) and a microstrip line, the microstrip line is a strip-shaped wire embedded in the PCB, a snakelike matching inductor and a fan-shaped matching capacitor are combined, the snakelike matching inductor provides high-frequency inductive reactance compensation, the fan-shaped matching capacitor realizes capacitive reactance matching, and the microstrip line is a strip-shaped wire embedded in the PCB. Different connector interfaces can be adapted; the first snakelike resonance inductor, the second snakelike resonance inductor and the lumped parameter capacitor form a mixed parameter resonance branch knot, the bandwidth is widened, the bandwidth can reach 0-4.5 GHZ and is increased by 2 GHZ and one time compared with the bandwidth of a filter commonly used in an existing system, the common resonance capacitor and the common resonance inductor are combined to form the lumped parameter resonance branch knot, and the bandwidth is increased by 2 GHZ and one time compared with the bandwidth of a filter commonly used in an existing system. The filter has the advantages that out-of-band noise is restrained, the size is reduced, return loss is larger than 15 dB and is improved by 50% compared with the requirement of an existing filter, the structure can be applied to radar and television systems, the problems that a traditional circuit is limited in bandwidth and poor in matching flexibility are solved, and meanwhile high power is achieved.

Description

Technical Field

[0001] This utility model relates to the field of electrical technology, and more specifically, to a broadband impedance matching filter high-pass circuit based on a 75-ohm system. Background Technology

[0002] Existing 75-ohm system filters are mainly divided into two categories: one is the integration of LTCC filters, and the other is the PCB microstrip filter. Among them, the LTCC filter achieves filtering through stacked circuits, and the input and output are directly matched to 75 ohms. However, it has the following problems: narrow bandwidth, only 500MHz, poor return loss <8dB; weak out-of-band rejection capability, and poor consistency. The PCB microstrip filter has a slightly wider frequency band of 0-2.5GHz, but it is large in size, has fixed impedance matching, poor adaptability, and cannot be compatible with various RF connectors, such as F-type and N-type.

[0003] The existing patent number is CN108832907A, which discloses a broadband impedance matching network for a data transmission radio and its design method. The matching network includes a first resonant circuit, which comprises a first inductor and a first capacitor. The first inductor and the first capacitor are connected in parallel or series between the device to be matched and the terminal. The method includes obtaining the first impedance trajectory of the first reflection coefficient of the device to be matched on a Smith chart, and designing a broadband impedance matching network for the data transmission radio that can cause the first impedance trajectory to curl or twist based on the positional relationship between the first impedance trajectory and a preset return loss circle. The matching network includes a first resonant circuit composed of the first inductor and the first capacitor. When performing impedance matching on the device to be matched, the first inductor and the first capacitor are connected in series or parallel between the device to be matched and the terminal. Only through the above-mentioned matching network and its design method can the impedance matching bandwidth of the device to be matched be expanded, thus improving the impedance matching effect.

[0004] It still cannot meet broadband requirements: insufficient suppression of stray signals, such as stray signals in television systems. Utility Model Content

[0005] In view of this, this utility model proposes a 75-ohm impedance matching high-pass filter circuit that meets the requirements of broadband 0-4.5GHz and has high return loss; it achieves miniaturization and high integration, and is compatible with various RF connectors, such as F-type and N-type; it improves out-of-band rejection capability, such as ≥50dB rejection at 340MHz.

[0006] A broadband impedance-matched filter high-pass circuit based on a 75-ohm system includes a PCB board 2 and a microstrip line. The microstrip line is a strip-shaped trace embedded inside the PCB board 2. One end of the microstrip line is an input terminal 5-2, and the other end is an output terminal 5-1, used for receiving signal input and output. The circuit is characterized in that a first adjustable impedance matching network is connected near the input terminal 5-2 of the microstrip line. The first adjustable impedance matching network is composed of a first sector-shaped matching capacitor 4-2 and a first serpentine matching inductor 6-2 connected in parallel. A second adjustable impedance matching network is connected near the output terminal 5-1 of the microstrip line. The second adjustable impedance matching network is composed of a second sector-shaped matching capacitor 4-1 and a first serpentine matching inductor 6-2 connected in parallel. Two serpentine matching inductors 6-1 are connected in parallel. Through the first and second adjustable impedance matching networks, and by adjusting the capacitive and inductive values ​​of the second sector matching capacitor 4-1 and the second serpentine matching inductor 6-1, capacitive and inductive reactance compensation is achieved, which can meet the matching requirements of various RF connector interfaces. A lumped parameter resonant circuit is connected between the first and second adjustable impedance matching networks. The lumped parameter resonant circuit is composed of a common resonant capacitor 8 and a common resonant inductor 9, which effectively increases out-of-band rejection, achieving an effective rejection of 50dB at 340MHz. It has a better effect on spurious emissions in television systems and can be widely used in various television systems, effectively solving the first drawback.

[0007] Furthermore, the ordinary resonant capacitor 8 is a tuning capacitor, which is a high-precision, high-Q capacitor that can meet the requirement of return loss greater than 15dB, thus improving the return performance of current broadband filters.

[0008] Furthermore, a first serpentine resonant inductor 7-2 is connected between the first adjustable impedance matching network and the lumped parameter resonant circuit, and a second serpentine resonant inductor 7-1 is connected between the second adjustable impedance matching network and the lumped parameter resonant circuit. The first serpentine resonant inductor 7-2, the second serpentine resonant inductor 7-1, and the lumped parameter capacitor form a hybrid parameter resonant stub. The distributed parameter characteristics of the serpentine inductor enable it to exhibit a stable inductance value in the high-frequency range, while the lumped capacitor provides accurate capacitive reactance in the low-frequency range. When the two are combined, the frequency range is expanded, achieving wideband resonance and broadening the bandwidth.

[0009] Furthermore, a coupling capacitor 3 is provided between the first adjustable impedance matching network, the first serpentine resonant inductor 7-2, the ordinary resonant capacitor 8, the ordinary resonant inductor 9, the second serpentine resonant inductor 7-1, and the second adjustable impedance matching network. The coupling capacitor 3 is connected to the microstrip line and plays a matching role, which can effectively adjust the return loss. All the capacitors 3 combined can guarantee a broadband return loss of 1.5GHz-4GHz.

[0010] Furthermore, the coupling capacitor 3 is located close to the edge of the microstrip line and forms a 45° angle with the microstrip line to reduce parasitic coupling.

[0011] Furthermore, the PCB board 2 adopts an anti-polarity symmetrical structure. Specifically, the anti-polarity symmetrical structure of the PCB board 2 is manifested as follows: the input terminal 5-2 and the output terminal 5-1 are mirror-symmetrical about the central axis; the second sector matching capacitor 4-1 and the first sector matching capacitor 4-2 are mirror-symmetrical about the central axis; the second serpentine matching inductor 6-1 and the first serpentine matching inductor 6-2 are mirror-symmetrical about the central axis; the second serpentine resonant inductor 7-1 and the first serpentine resonant inductor 7-2 are mirror-symmetrical about the central axis; and the ordinary resonant capacitor 8 and the ordinary resonant inductor 9 are mirror-symmetrical about the central axis, thereby eliminating common-mode interference and improving signal integrity.

[0012] Furthermore, the PCB board 2 is fixed to the metal shielding cavity by screws 1 to reduce electromagnetic interference.

[0013] The beneficial effects of this utility model are as follows: This utility model proposes a broadband impedance matching filter high-pass circuit based on a 75-ohm system. It adopts a combination of serpentine matching inductors and fan-shaped matching capacitors. The serpentine matching inductors provide high-frequency inductive reactance compensation, and the fan-shaped matching capacitors achieve capacitive reactance matching, adapting to different connector interfaces. The first serpentine resonant inductor 7-2, the second serpentine resonant inductor 7-1, and the lumped parameter capacitor form a hybrid parameter resonant stub, which broadens the bandwidth to 0-4.5GHz, which is 2GHz higher than the bandwidth of commonly used filters in existing systems, doubling the bandwidth. The ordinary resonant capacitor 8 and the ordinary resonant inductor 9 are combined to form a lumped parameter resonant stub, which suppresses out-of-band noise and reduces the size. The return loss is greater than 15dB, which is 50% higher than the requirements of existing filters. This structure can be applied to radar and television systems, solving the problems of limited bandwidth and poor matching flexibility of traditional circuits, while also possessing high power. Attached Figure Description

[0014] Figure 1 This is a circuit diagram of a power supply circuit for a broadband impedance matching filter high-pass circuit based on a 75-ohm system according to this application.

[0015] Explanation of main component symbols

[0016] Screw 1, PCB board 2, coupling capacitor 3, first sector matching capacitor 4-2, second sector matching capacitor 4-1, input terminal 5-2, output terminal 5-1, first serpentine matching inductor 6-2, second serpentine matching inductor 6-1, first serpentine resonant inductor 7-2, second serpentine resonant inductor 7-1, ordinary resonant capacitor 8, ordinary resonant inductor 9.

[0017] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this utility model. Detailed Implementation

[0018] The following embodiments are described to aid in understanding this application. These embodiments are not, and should not be, construed in any way as limiting the scope of protection of this application.

[0019] In the following description, those skilled in the art will recognize that throughout this discussion, components may be described as individual functional units (which may include subunits), but those skilled in the art will recognize that various components or portions thereof may be divided into individual components or may be integrated together (including integrated within a single system or component).

[0020] Furthermore, the connection between components or systems is not intended to be limited to a direct connection; on the contrary, data between these components may be modified, reformatted, or otherwise altered by intermediate components. Additionally, other or fewer connections may be used. It should also be noted that the terms "connection," "link," or "input" should be understood to include direct connections, indirect connections via one or more intermediate devices, and wireless connections.

[0021] Example 1:

[0022] like Figure 1 As shown, a broadband impedance-matched filter high-pass circuit based on a 75-ohm system includes a PCB board 2 and a microstrip line. The microstrip line is a strip-shaped trace embedded inside the PCB board 2. One end of the microstrip line is an input terminal 5-2, and the other end is an output terminal 5-1, used for receiving signal input and output. The circuit is characterized in that a first adjustable impedance matching network is connected near the input terminal 5-2 of the microstrip line. The first adjustable impedance matching network is composed of a first sector-shaped matching capacitor 4-2 and a first serpentine matching inductor 6-2 connected in parallel. A second adjustable impedance matching network is connected near the output terminal 5-1 of the microstrip line. The second adjustable impedance matching network is composed of a second sector-shaped matching capacitor 4-1. The first adjustable impedance matching network and the second adjustable impedance matching inductor 6-1 are connected in parallel. Through these two networks, and by adjusting the capacitive and inductive values ​​of the second sector-shaped matching capacitor 4-1 and the second serpentine matching inductor 6-1, capacitive and inductive reactance compensation is achieved, satisfying the matching requirements of various RF connector interfaces. A lumped parameter resonant circuit is connected between the first and second adjustable impedance matching networks. This circuit consists of a common resonant capacitor 8 and a common resonant inductor 9, effectively increasing out-of-band rejection. At 340MHz, it effectively suppresses spurious emissions by 50dB, providing better performance for television systems and allowing for wide application in various television systems, effectively addressing the first drawback. (Can the positions of the common resonant capacitor 8 and the common resonant inductor 9 be interchanged?)

[0023] The ordinary resonant capacitor 8 is a tuning capacitor, which is a high-precision, high-Q capacitor that can meet the requirement of return loss greater than 15dB, thus improving the return performance of current broadband filters.

[0024] The first adjustable impedance matching network and the lumped parameter resonant circuit are connected by a first serpentine resonant inductor 7-2, and the second adjustable impedance matching network and the lumped parameter resonant circuit are connected by a second serpentine resonant inductor 7-1. The first serpentine resonant inductor 7-2, the second serpentine resonant inductor 7-1 and the lumped parameter capacitor form a hybrid parameter resonant stub. The distributed parameter characteristics of the serpentine inductor enable it to present a stable inductance value in the high frequency range, while the lumped capacitor provides accurate capacitive reactance in the low frequency range. The combination of the two expands the frequency range, realizes wideband resonance, and broadens the bandwidth.

[0025] A coupling capacitor 3 is provided between the first adjustable impedance matching network, the first serpentine resonant inductor 7-2, the ordinary resonant capacitor 8, the ordinary resonant inductor 9, the second serpentine resonant inductor 7-1, and the second adjustable impedance matching network. The coupling capacitor 3 is connected to the microstrip line and plays a matching role, which can effectively adjust the return loss. All the capacitors 3 can guarantee a broadband return loss of 1.5GHz-4GHz.

[0026] The PCB board 2 adopts an anti-polarity symmetrical structure, which is specifically manifested as follows: the input terminal 5-2 and the output terminal 5-1 are mirror-symmetrical about the central axis; the second sector matching capacitor 4-1 and the first sector matching capacitor 4-2 are mirror-symmetrical about the central axis; the second serpentine matching inductor 6-1 and the first serpentine matching inductor 6-2 are mirror-symmetrical about the central axis; the second serpentine resonant inductor 7-1 and the first serpentine resonant inductor 7-2 are mirror-symmetrical about the central axis; and the ordinary resonant capacitor 8 and the ordinary resonant inductor 9 are mirror-symmetrical about the central axis, thereby eliminating common-mode interference and improving signal integrity.

[0027] The PCB board 2 is fixed to the metal shielding cavity by screws 1 to reduce electromagnetic interference.

[0028] The beneficial effects of this utility model are as follows: This utility model proposes a broadband impedance matching filter high-pass circuit based on a 75-ohm system. It adopts a combination of serpentine matching inductors and fan-shaped matching capacitors. The serpentine matching inductors provide high-frequency inductive reactance compensation, and the fan-shaped matching capacitors achieve capacitive reactance matching, adapting to different connector interfaces. The first serpentine resonant inductor 7-2, the second serpentine resonant inductor 7-1, and the lumped parameter capacitor form a hybrid parameter resonant stub, which broadens the bandwidth to 0-4.5GHz, which is 2GHz higher than the bandwidth of commonly used filters in existing systems, doubling the bandwidth. The ordinary resonant capacitor 8 and the ordinary resonant inductor 9 are combined to form a lumped parameter resonant stub, which suppresses out-of-band noise and reduces the size. The return loss is greater than 15dB, which is 50% higher than the requirements of existing filters. This structure can be applied to radar and television systems, solving the problems of limited bandwidth and poor matching flexibility of traditional circuits, while also possessing high power.

[0029] Although this application discloses several aspects and embodiments, other aspects and embodiments will be obvious to those skilled in the art. Various modifications and improvements can be made without departing from the concept of this application, and these all fall within the scope of protection of this application. The various aspects and embodiments disclosed in this application are for illustrative purposes only and are not intended to limit this application. The actual scope of protection of this application is determined by the claims.

Claims

1. A broadband impedance-matched high-pass filter circuit based on a 75-ohm system, comprising a PCB board (2) and a microstrip line, wherein the microstrip line is a strip-shaped trace embedded inside the PCB board (2), one end of the microstrip line is an input terminal (5-2), and the other end is an output terminal (5-1), used for receiving signal input and output, characterized in that, A first adjustable impedance matching network is connected near the input terminal (5-2) of the microstrip line. The first adjustable impedance matching network is composed of a first sector matching capacitor (4-2) and a first serpentine matching inductor (6-2) connected in parallel. A second adjustable impedance matching network is connected near the output terminal (5-1) of the microstrip line. The second adjustable impedance matching network is composed of a second sector matching capacitor (4-1) and a second serpentine matching inductor (6-1) connected in parallel. By adjusting the capacitive and inductive values ​​of the second sector matching capacitor (4-1) and the second serpentine matching inductor (6-1) through the first and second adjustable impedance matching networks, capacitive and inductive reactance compensation can be achieved, which can meet the matching of various RF connector interfaces. A lumped parameter resonant circuit is connected between the first and second adjustable impedance matching networks. The lumped parameter resonant circuit is composed of a common resonant capacitor (8) and a common resonant inductor (9).

2. The broadband impedance matching filter high-pass circuit based on a 75-ohm system as described in claim 1, characterized in that: The ordinary resonant capacitor (8) is a tuning capacitor. The tuning capacitor is a high-precision, high-Q capacitor that can meet the requirement of return loss greater than 15dB.

3. The broadband impedance matching filter high-pass circuit based on a 75-ohm system as described in claim 1, characterized in that: A first serpentine resonant inductor (7-2) is connected between the first adjustable impedance matching network and the lumped parameter resonant circuit, and a second serpentine resonant inductor (7-1) is connected between the second adjustable impedance matching network and the lumped parameter resonant circuit. The first serpentine resonant inductor (7-2), the second serpentine resonant inductor (7-1), and the lumped parameter capacitor form a hybrid parameter resonant stub.

4. The broadband impedance matching filter high-pass circuit based on a 75-ohm system as described in claim 1, characterized in that: A coupling capacitor (3) is provided between the first adjustable impedance matching network, the first serpentine resonant inductor (7-2), the ordinary resonant capacitor (8), the ordinary resonant inductor (9), the second serpentine resonant inductor (7-1), and the second adjustable impedance matching network. The coupling capacitor (3) is connected to the microstrip line.

5. The broadband impedance matching filter high-pass circuit based on a 75-ohm system as described in claim 4, characterized in that: The coupling capacitor (3) is located close to the edge of the microstrip line and forms a 45° angle with the microstrip line.

6. The broadband impedance matching filter high-pass circuit based on a 75-ohm system as described in claim 1, characterized in that: The PCB board (2) adopts an anti-polarity symmetrical structure. Specifically, the anti-polarity symmetrical structure of the PCB board (2) is as follows: the input terminal (5-2) and the output terminal (5-1) are mirror-symmetrical about the central axis; the second sector matching capacitor (4-1) and the first sector matching capacitor (4-2) are mirror-symmetrical about the central axis; the second serpentine matching inductor (6-1) and the first serpentine matching inductor (6-2) are mirror-symmetrical about the central axis; the second serpentine resonant inductor (7-1) and the first serpentine resonant inductor (7-2) are mirror-symmetrical about the central axis; and the ordinary resonant capacitor (8) and the ordinary resonant inductor (9) are mirror-symmetrical about the central axis.

7. The broadband impedance matching filter high-pass circuit based on a 75-ohm system as described in claim 1, characterized in that: The PCB board (2) is fixed to the metal shielding cavity by screws (1).

Images