Radio frequency band-pass filter circuit

Abstract

The utility model discloses a radio frequency band-pass filter circuit, and belongs to the technical field of filtering. The system mainly comprises a high-frequency signal acquisition unit used for being electrically connected with an ultrahigh frequency sensor, and the high-frequency signal acquisition unit converts a high-frequency electromagnetic wave signal into a voltage signal and inputs the converted signal to an amplification circuit unit for amplification processing; the output end of the amplifying circuit unit is electrically connected with the primary filter; the first-stage filter is used for filtering the electric signals with the frequency value smaller than f1; the electric signal processed by the primary filter is electrically connected with the input end of the low-pass filter, and the output end of the low-pass filter outputs a power-on electric signal to the MCU main control chip; and the cut-off frequency of the low-pass filter is f2. The circuit is simple and reasonable in design, can accurately and effectively screen out the frequency band of a flashover signal, is high in noise reduction capability, is high in anti-interference performance, is low in production cost, is high in cost performance, is low in fault rate, is high in reliability, and is very high in market competitiveness.

Description

Technical Field

[0001] This utility model belongs to the field of filtering technology, and more specifically, it relates to a high-performance radio frequency bandpass filter circuit with simple and reliable circuit design, low cost, strong noise reduction capability, and strong anti-interference capability. Background Technology

[0002] Cables are a critical component of power transmission. Flashover can lead to short circuits and other faults, posing significant safety hazards. Flashover frequencies range from 100MHz to 1.5GHz. By monitoring cable flashovers, potential problems can be detected promptly, allowing for appropriate maintenance measures to prevent faults and ensure the stable operation of the power system.

[0003] Chinese patent CN102064787B, with authorization announcement date May 21, 2014, and invention titled "A Radio Frequency Bandpass Filtering Circuit," discloses a radio frequency bandpass filtering circuit that mainly includes: a first resonant module for receiving radio frequency signals and suppressing radio frequency signals at a preset first resonant frequency; frequency selection for radio frequency signals at a preset second resonant frequency and suppressing other radio frequency signals besides the preset second resonant frequency; and a second resonant unit for receiving the radio frequency signals output by the first resonant module and suppressing radio frequency signals at a preset third resonant frequency. The first resonant module includes a first capacitor, a second capacitor, a first inductor, and a first varactor diode. The first terminal of the first capacitor is connected to the input terminal and grounded through the second capacitor; the second terminal of the first capacitor is grounded through the first inductor; the cathode of the first varactor diode is connected to the first terminal of the first capacitor, and the anode is connected to the second terminal of the first capacitor. Alternatively, the first resonant module includes a first resonant unit and a frequency selection circuit unit. The first resonant unit receives radio frequency (RF) signals and suppresses RF signals at a preset first resonant frequency. The frequency selection circuit unit selects the RF signal at a second resonant frequency from the RF signals output by the first resonant unit and suppresses other RF signals besides the preset second resonant frequency. The second resonant unit includes a third inductor, a fifth capacitor, a third varactor diode, and a sixth capacitor. The first terminal of the third inductor is connected to the input terminal, and the second terminal is connected to the output terminal. The fifth capacitor, the third varactor diode, and the sixth capacitor, connected in series, are connected in parallel with the third inductor. The anode of the third varactor diode is grounded through a first resistor. With this scheme, the traditional RF bandpass filter circuit achieves suppression of RF signals at the zero point, thereby effectively suppressing spurious signals on the left and right sides of the near end of the RF signal.

[0004] However, traditional RF bandpass filter circuits are relatively complex to design, have many types of components, and have relatively high procurement costs, resulting in high overall production costs. In addition, since the failure of any component will cause the entire filter circuit to malfunction, too many components will reduce the reliability of the entire circuit. Utility Model Content

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-performance, cost-effective radio frequency bandpass filter circuit that features simple and reliable circuit design, low cost, strong noise reduction capability, and strong anti-interference capability.

[0006] This utility model is achieved through the following technical solution:

[0007] A radio frequency bandpass filter circuit includes a high-frequency signal acquisition unit for electrical connection with an ultra-high frequency sensor. The high-frequency signal acquisition unit converts high-frequency electromagnetic wave signals into voltage signals and inputs the converted signals to an amplifier circuit unit for amplification. The output of the amplifier circuit unit is electrically connected to a first-stage filter via a high-speed switching diode VD1. The first-stage filter includes a resistor R14 and a capacitor C8 connected in parallel. The first-stage filter is used to filter out electrical signals with frequencies less than f1. The electrical signal processed by the first-stage filter is then electrically connected to the input of a low-pass filter via an impedance matching resistor R8. The output of the low-pass filter outputs a bandpass signal to an MCU main control chip via an impedance matching resistor R9 and a diode VD2. The cutoff frequency of the low-pass filter is f2, and the low-pass filter includes a capacitor C5 and a resistor R11 connected in parallel.

[0008] Preferably, the value of f1 is 100MHz and the value of f2 is 1500MHz.

[0009] Preferably, a three-stage filter is electrically connected between the diode VD2 and the MCU main control chip; the three-stage filter includes a resistor R12 and a capacitor C7 connected in parallel; the cathode of the diode VD2 is electrically connected to one end of the resistor R12, one end of the capacitor C7, and the MCU main control chip through the impedance matching resistor R10; the other end of the resistor R12 and the other end of the capacitor C7 are both electrically connected to the ground terminal AGND.

[0010] Preferably, the high-frequency signal acquisition unit includes an RF pickup chip U2 and an external interface PEX for connecting an ultra-high frequency sensor. Pins 2 and 3 of the external interface PEX are electrically connected to the ground terminal AGND. Pin 1 of the external interface PEX is electrically connected to the ground terminal AGND via an RF coupling capacitor C6, a noise reduction resistor R16, an RF coupling capacitor C9, and a symmetrical resistor R15. The two ends of the resistor R16 are electrically connected to pins 2 and 3 of the RF pickup chip U2, respectively. Pin 1 of the RF pickup chip U2 is electrically connected to one end of a filter capacitor C4, the positive terminal of an electrolytic capacitor E2, and one end of a resistor R2. The other end of the resistor R2 is electrically connected to the power supply terminal VCC-A5V. The other end of the filter capacitor C4, the positive terminal of the electrolytic capacitor E2, and the positive terminal of the electrolytic capacitor E2 are also electrically connected. The negative terminal of electrolytic capacitor E2 is electrically connected to ground AGND; pin 4 of RF pickup chip U2 is electrically connected to one end of filter capacitor C10, the positive terminal of electrolytic capacitor E3, and one end of resistor R17. The other end of resistor R17 is electrically connected to power supply VCC-A5V. The negative terminal of electrolytic capacitor E3 and the other end of filter capacitor C10 are both electrically connected to ground AGND; pins 5 and 6 of RF pickup chip U2 are both electrically connected to ground AGND; pin 7 of RF pickup chip U2 is electrically connected to the input terminal of the amplifier circuit unit through feedback resistor R13 and impedance matching resistor R5; pin 8 of RF pickup chip U2 is electrically connected between feedback resistor R13 and impedance matching resistor R5.

[0011] Preferably, the radio frequency pickup chip U2 is model AD8313.

[0012] Preferably, the amplification circuit unit includes an amplifier U1. Pin 3 of amplifier U1 is electrically connected to the output terminal of the high-frequency signal acquisition unit; pin 4 of amplifier U1 is electrically connected to the ground terminal AGND; pin 2 of amplifier U1 is electrically connected between proportional resistors R3 and R4. The other end of proportional resistor R3 is electrically connected to the ground terminal AGND, and the other end of proportional resistor R4 is electrically connected to the ground terminal AGND via a filter capacitor C1 and to pin 6 of amplifier U1; pin 6 of amplifier U1 is electrically connected to the high-speed switching diode VD1 via impedance matching resistors R6 and R7; pin 7 of amplifier U1 is electrically connected to the ground terminal AGND via capacitor C3, capacitor C2, electrolytic capacitor E1, and also via resistor R1 to the power supply terminal VCC-A5V.

[0013] Preferably, the amplifier U1 is model AD8008.

[0014] Compared with the prior art, the beneficial effects of this utility model are:

[0015] 1. The circuit design of this utility model is simple and reasonable, and can accurately and effectively select the frequency band of flashover signal. The circuit has strong noise reduction capability and strong anti-interference capability.

[0016] 2. This utility model uses fewer types and quantities of components, resulting in low production costs, high cost-effectiveness, low failure rate, and high reliability. It has strong market competitiveness and can be widely used in technical fields that require screening specific signal frequency bands, especially in the field of cable partial discharge safety monitoring. Attached Figure Description

[0017] Figure 1 These are the circuit schematics of Embodiment 1 and Embodiment 2 of this utility model.

[0018] Figure 2 This is the circuit principle of embodiment 3 of the present invention. Figure 1 .

[0019] Figure 3 This is the circuit principle of embodiment 3 of the present invention. Figure 2 .

[0020] In the diagram: 1. High-frequency signal acquisition unit; 2. Amplification circuit unit; 3. MCU main control chip. Detailed Implementation

[0021] To enable readers to better understand the design intent of this utility model, the technical solution described below is further described in conjunction with embodiments. It should be noted that directional terms that may appear in the following paragraphs, including but not limited to "up," "down," "left," "right," "front," and "back," are based on the visual orientation shown in the accompanying drawings and should not be considered as limitations on the scope of protection or technical solution of this utility model. Their purpose is solely to facilitate a better understanding of the technical solution described in this utility model by those skilled in the art.

[0022] In this specification, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0023] Example 1

[0024] like Figure 1As shown, a radio frequency bandpass filter circuit includes a high-frequency signal acquisition unit 1 for electrical connection with an ultra-high frequency sensor. The radio frequency pickup chip U2 of the high-frequency signal acquisition unit 1 converts the high-frequency electromagnetic wave signal into a voltage signal and inputs this converted signal to an amplifier circuit unit 2 for amplification. The output terminal of the amplifier circuit unit 2 is electrically connected to a first-stage filter via a high-speed switching diode VD1. The first-stage filter includes a resistor R14 and a capacitor C8 connected in parallel. The first-stage filter is used to filter out electrical signals with frequencies less than f1. The electrical signal processed by the first-stage filter is then electrically connected to the input terminal of a low-pass filter via an impedance matching resistor R8. The output terminal of the low-pass filter outputs a bandpass signal to the MCU main control chip 3 via an impedance matching resistor R9 and a diode VD2. The cutoff frequency of the low-pass filter is f2, and the low-pass filter includes a capacitor C5 and a resistor R11 connected in parallel. Specifically, the output of amplifier circuit unit 2 is electrically connected to the anode of high-speed switching diode VD1 to prevent signal reverse transmission. The cathode of high-speed switching diode VD1 is electrically connected to one end of resistor R14 and capacitor C8, and then to one end of impedance matching resistor R8. The other ends of resistor R14 and capacitor C8 are both electrically connected to ground AGND. The other end of impedance matching resistor R8 is electrically connected to the input of low-pass filter. The output of low-pass filter is electrically connected to the anode of diode VD2 via impedance matching resistor R9. The cathode of diode VD2 transmits the signal to MCU main control chip 3. Diode VD2 acts as a unidirectional conductor, preventing signal return. The first-stage filter composed of resistor R14 and capacitor C8 filters out signals with frequencies below f1, meaning signals with frequencies below f1 are suppressed and cannot pass through. The cutoff frequency of the low-pass filter composed of capacitor C5 and resistor R11 is f2, meaning signals with frequencies above f2 cannot pass through the low-pass filter. Therefore, this embodiment allows electrical signals with frequencies between f1 and f2 to pass through. The circuit between the high-speed switching diode VD1 and diode VD2 in this embodiment forms a bandpass filter, fixing the frequency range between f1 and f2.

[0025] The circuit design in this embodiment is simple and reasonable, and can accurately and effectively filter the frequency band of flashover signal. The circuit has strong noise reduction capability and strong anti-interference capability. It uses few types and quantities of components, resulting in low production cost, high cost performance, low failure rate, and high reliability. It has strong market competitiveness and can be widely used in technical fields that require filtering specific signal frequency bands.

[0026] Example 2

[0027] Based on Embodiment 1, this embodiment continues to describe in detail the technical features involved therein and the functions and roles of these technical features in this utility model, so as to help those skilled in the art to fully understand the technical solution of this utility model and reproduce it.

[0028] Continue as Figure 1 As shown, in this embodiment, a three-stage filter is electrically connected between diode VD2 and the MCU main control chip 3. The three-stage filter specifically includes a resistor R12 and a capacitor C7 connected in parallel; the cathode of diode VD2 is electrically connected to one end of resistor R12, one end of capacitor C7, and the MCU main control chip 3 via impedance matching resistor R10; the other ends of resistor R12 and capacitor C7 are both electrically connected to the ground terminal AGND. The three-stage filter further reduces noise in the output signal, making the bandpass signal transmitted to the MCU main control chip 3 more accurate, and further improving the circuit's anti-interference and noise reduction performance. In this embodiment, the value of f1 is 100MHz and the value of f2 is 1500MHz. This embodiment can accurately filter the cable flashover signal frequency band and can be widely used in the field of cable partial discharge safety monitoring technology.

[0029] Example 3

[0030] Based on Embodiment 1 or Embodiment 2, this embodiment continues to describe in detail the technical features involved therein and the functions and roles of these technical features in this utility model, so as to help those skilled in the art to fully understand the technical solution of this utility model and reproduce it.

[0031] like Figure 2 , Figure 3As shown, the high-frequency signal acquisition unit 1 in this embodiment further includes an external interface PEX for connecting an ultra-high frequency sensor. Pins 2 and 3 of the external interface PEX are electrically connected to the ground terminal AGND. Pin 1 of the external interface PEX is electrically connected to the ground terminal AGND via an RF coupling capacitor C6, a noise reduction resistor R16, an RF coupling capacitor C9, and a symmetrical resistor R15. The two ends of the resistor R16 are electrically connected to pins 2 and 3 of the RF pickup chip U2, respectively. The model of the RF pickup chip U2 in this embodiment is AD8313. Pin 1 of RF pickup chip U2 is electrically connected to one end of filter capacitor C4, the positive terminal of electrolytic capacitor E2, and one end of resistor R2. The other end of resistor R2 is electrically connected to the power supply terminal VCC-A5V. The other end of filter capacitor C4 and the negative terminal of electrolytic capacitor E2 are both electrically connected to ground terminal AGND. Pin 4 of RF pickup chip U2 is electrically connected to one end of filter capacitor C10, the positive terminal of electrolytic capacitor E3, and one end of resistor R17. The other end of resistor R17 is electrically connected to the power supply terminal VCC-A5V. The negative terminal of electrolytic capacitor E3 and the other end of filter capacitor C10 are both electrically connected to ground terminal AGND. Pins 5 and 6 of RF pickup chip U2 are both electrically connected to ground terminal AGND. Pin 7 of RF pickup chip U2 is electrically connected to the input terminal of amplifier circuit unit 2 through feedback resistor R13 and impedance matching resistor R5. Pin 8 of RF pickup chip U2 is electrically connected between feedback resistor R13 and impedance matching resistor R5. Radio frequency (RF) coupling capacitors C6 and C9 couple the high-frequency signal sensed by the UHF sensor to the input of the RF pickup chip U2, blocking the DC signal. Resistor R16 acts as a noise reduction resistor and also provides impedance matching, reducing input noise and signal loss. Resistor R15 is a symmetrical resistor with a resistance of 0 ohms, providing a reference level for the negative terminal of the high-frequency signal. Resistors R2 and R17 further filter the power supply entering the RF pickup chip U2. Electrolytic capacitors E2, C4, E3, and C10 further stabilize the voltage, ensuring a stable and clean DC voltage for the RF pickup chip U2. The output of the RF pickup chip U2 is connected to impedance matching resistor R5 and feedback resistor R13, with feedback resistor R13 connected to pin 7 of the RF pickup chip U2 as the feedback signal. Thus, the high-frequency signal is converted into a relevant voltage signal, resulting in a stable and clean signal.

[0032] In this embodiment, amplifier circuit unit 2 specifically includes amplifier U1, which is model AD8008. Pin 3 of amplifier U1 is electrically connected to the output terminal of high-frequency signal acquisition unit 1, that is, pin 3 of amplifier U1 is electrically connected to the other end of impedance matching resistor R5. Pin 4 of amplifier U1 is electrically connected to ground terminal AGND. Pin 2 of amplifier U1 is electrically connected between proportional resistors R3 and R4. The other end of proportional resistor R3 is electrically connected to ground terminal AGND; the other end of proportional resistor R4 is electrically connected to ground terminal AGND via filter capacitor C1 and to pin 6 of amplifier U1; pin 6 of amplifier U1 is electrically connected to high-speed switching diode VD1 via impedance matching resistors R6 and R7; pin 7 of amplifier U1 is electrically connected to ground terminal AGND via capacitor C3, capacitor C2, electrolytic capacitor E1, and also via resistor R1 to the power supply terminal VCC-A5V. Amplifier U1 is powered by a single-ended power supply, and the amplification ratio is determined by proportional resistors R3 and R4. Pin 2 of amplifier U1 is the negative input terminal, and pin 3 is the positive input terminal. The impedance of amplifier U1 is adjusted by impedance matching resistors R6 and R7. Amplifier circuit unit 2 amplifies the voltage signal converted by high-frequency signal acquisition unit 1 to improve signal strength. The circuit design is simple and reasonable, and the signal is stable and distortion-free.

[0033] In summary, this is merely a preferred embodiment of the present utility model and is not intended to limit the scope of the present utility model. All equivalent variations and modifications made in accordance with the shape, structure, features and spirit of the claims of the present utility model should be included within the scope of the claims of the present utility model.

Claims

1. A radio frequency bandpass filter circuit, characterized in that: The system includes a high-frequency signal acquisition unit (1) for electrical connection with an ultra-high frequency sensor. The high-frequency signal acquisition unit (1) converts the high-frequency electromagnetic wave signal into a voltage signal and inputs the converted signal to an amplifier circuit unit (2) for amplification. The output of the amplifier circuit unit (2) is electrically connected to a first-stage filter via a high-speed switching diode VD1. The first-stage filter includes a resistor R14 and a capacitor C8 connected in parallel. The first-stage filter is used to filter out electrical signals with a frequency value less than f1. The electrical signal processed by the first-stage filter is then electrically connected to the input of a low-pass filter via an impedance matching resistor R8. The output of the low-pass filter outputs a band-pass signal to the MCU main control chip (3) via an impedance matching resistor R9 and a diode VD2. The cutoff frequency of the low-pass filter is f2. The low-pass filter includes a capacitor C5 and a resistor R11 connected in parallel.

2. The radio frequency bandpass filter circuit according to claim 1, characterized in that: The value of f1 is 100MHz, and the value of f2 is 1500MHz.

3. The radio frequency bandpass filter circuit according to claim 1, characterized in that: The diode VD2 is also electrically connected to the MCU main control chip (3) via a three-stage filter; the three-stage filter includes a resistor R12 and a capacitor C7 connected in parallel; the cathode of the diode VD2 is electrically connected to one end of the resistor R12, one end of the capacitor C7, and the MCU main control chip (3) via an impedance matching resistor R10; the other end of the resistor R12 and the other end of the capacitor C7 are electrically connected to the ground terminal AGND.

4. The radio frequency bandpass filter circuit according to claim 1, characterized in that: The high-frequency signal acquisition unit (1) includes an RF pickup chip U2 and an external interface PEX for connecting an ultra-high frequency sensor. Pins 2 and 3 of the external interface PEX are electrically connected to the ground terminal AGND. Pin 1 of the external interface PEX is electrically connected to the ground terminal AGND via an RF coupling capacitor C6, a noise reduction resistor R16, an RF coupling capacitor C9, and a symmetrical resistor R15. The two ends of the resistor R16 are electrically connected to pins 2 and 3 of the RF pickup chip U2, respectively. Pin 1 of the RF pickup chip U2 is electrically connected to one end of the filter capacitor C4, the positive terminal of the electrolytic capacitor E2, and one end of the resistor R2. The other end of the resistor R2 is electrically connected to the power supply terminal VCC-A5V. The other end of the filter capacitor C4 and the electrolytic capacitor E2 are electrically connected to the power supply terminal VCC-A5V. The negative terminal of capacitor E2 is electrically connected to the ground terminal AGND; pin 4 of RF pickup chip U2 is electrically connected to one end of filter capacitor C10, the positive terminal of electrolytic capacitor E3, and one end of resistor R17. The other end of resistor R17 is electrically connected to the power supply terminal VCC-A5V. The negative terminal of electrolytic capacitor E3 and the other end of filter capacitor C10 are electrically connected to the ground terminal AGND; pins 5 and 6 of RF pickup chip U2 are electrically connected to the ground terminal AGND; pin 7 of RF pickup chip U2 is electrically connected to the input terminal of the amplifier circuit unit (2) through feedback resistor R13 and impedance matching resistor R5; pin 8 of RF pickup chip U2 is electrically connected between feedback resistor R13 and impedance matching resistor R5.

5. The radio frequency bandpass filter circuit according to claim 4, characterized in that: The radio frequency pickup chip U2 is model AD8313.

6. The radio frequency bandpass filter circuit according to claim 1, characterized in that: The amplifier circuit unit (2) includes amplifier U1. Pin 3 of amplifier U1 is electrically connected to the output terminal of the high-frequency signal acquisition unit (1). Pin 4 of amplifier U1 is electrically connected to the ground terminal AGND. Pin 2 of amplifier U1 is electrically connected between proportional resistor R3 and proportional resistor R4. The other end of proportional resistor R3 is electrically connected to the ground terminal AGND. The other end of proportional resistor R4 is electrically connected to the ground terminal AGND via filter capacitor C1 and to pin 6 of amplifier U1. Pin 6 of amplifier U1 is electrically connected to the high-speed switching diode VD1 via impedance matching resistor R6 and impedance matching resistor R7. Pin 7 of amplifier U1 is electrically connected to the ground terminal AGND via capacitor C3, to the ground terminal AGND via capacitor C2, to the ground point AGND via electrolytic capacitor E1, and to the power supply terminal VCC-A5V via resistor R1.

7. The radio frequency bandpass filter circuit according to claim 6, characterized in that: The amplifier U1 is model AD8008.

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