A bandpass filter circuit

Abstract

This utility model relates to a bandpass filter circuit, which includes a low-pass filter unit, a high-pass filter unit, and a power supply bias unit. The low-pass filter unit and the high-pass filter unit are connected together, and the power supply bias unit is connected to both the low-pass filter unit and the high-pass filter unit. The low-pass filter unit is used to suppress high-frequency noise interference above 2100Hz; the high-pass filter unit is used to filter out low-frequency noise interference below 1300Hz; a stable and matched operating voltage is provided to the operational amplifiers corresponding to the low-pass filter unit and the high-pass filter unit through a voltage divider method to ensure that the two-stage filter units are in optimal working condition. It can efficiently suppress out-of-band noise and AC ripple. After optimizing the signal waveform and improving the signal quality, the processed clean signal is sent to the decoding module and MCU for processing, providing key support for the reliable operation of the VHFDSC system.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, and in particular to a bandpass filter circuit. Background Technology

[0002] VHF Digital Selective Calling (VHFDSC) is one of the core technologies for maritime communication designated by the International Maritime Organization (IMO). Its core working principle is to carry digital call signals through specific audio frequencies (1300Hz and 2100Hz), where 1300Hz corresponds to the number "0" and 2100Hz corresponds to the number "1".

[0003] However, during actual VHF DSC signal transmission, the signal is highly susceptible to multi-source noise interference due to the complex marine environment and the inherent characteristics of the circuit, leading to severe signal distortion. The interference sources mainly fall into three categories: first, marine environmental noise, which superimposes low-frequency (2100Hz) interference components into the signal transmission link; second, inherent noise of the circuit system; and third, channel interference, as the VHF DSC band (156.525MHz) is easily affected by crosstalk from other maritime and civilian communication equipment.

[0004] The aforementioned noise interference has seriously threatened the reliability of VHF DSC communication: Firstly, signal distortion leads to an increased bit error rate at the receiver. When the core 1300Hz and 2100Hz signals are covered or superimposed by noise, the receiver's decoding module is prone to misidentification; secondly, severe noise interference can increase the frequency of signal interruptions, making it difficult to meet the requirements of continuous navigation safety monitoring.

[0005] In existing technologies, using conventional RC filters for audio signals to filter VHF DSC signals has significant drawbacks: Firstly, the passband range of conventional RC filters is difficult to accurately match the 1300Hz~2100Hz core frequency band of VHF DSC audio signals. The passband is either too wide (e.g., 300Hz~3000Hz) or too narrow (e.g., 1400Hz~1600Hz), resulting in attenuation of the 1300Hz and 2100Hz core signals; thus, it is difficult to meet application requirements. Utility Model Content

[0006] The purpose of this invention is to solve the problems of signal distortion, increased bit error rate, call failure, and communication interruption caused by noise interference during the transmission of VHF DSC audio signals. This bandpass filter employs a cascaded low-pass and high-pass filter structure, operating as a voltage follower via an operational amplifier, achieving a passband characteristic of 1300Hz~2100Hz (center frequency 1700Hz, bandwidth 800Hz). It effectively suppresses out-of-band noise and AC ripple, optimizes the signal waveform, and improves the stability and accuracy of VHF DSC communication.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A bandpass filter circuit, comprising: Low-pass filter unit, high-pass filter unit, and power supply bias unit; The low-pass filter unit and the high-pass filter unit are connected, and the power supply bias unit is connected to the low-pass filter unit and the high-pass filter unit respectively. The low-pass filter unit is used to suppress high-frequency noise interference above 2100Hz; the high-pass filter unit is used to filter out low-frequency noise interference below 1300Hz; a stable and matched operating voltage is provided to the operational amplifiers corresponding to the low-pass filter unit and the high-pass filter unit through a voltage divider method to ensure that the two-stage filter units are in the optimal working state.

[0008] Preferably, the low-pass filter unit includes resistors R1, R2, and R3.

[0009] Preferably, the low-pass filter unit includes capacitors C1, C2, C3, and C4.

[0010] Preferably, the low-pass filter unit includes an operational amplifier U1.

[0011] Preferably, the high-pass filter unit includes resistors R5 and R6.

[0012] Preferably, the high-pass filter unit includes capacitor C6, capacitor C7, capacitor C8, and operational amplifier U2.

[0013] Preferably, the power supply bias unit includes resistors R7, R8, R9, and R10.

[0014] Preferably, capacitor C1 is connected in series with resistors R1, R2, R3, and operational amplifier U1; capacitor C2 is disposed between resistors R1 and R2; capacitor C3 is disposed between resistor R3 and operational amplifier U1; one end of capacitor C4 is disposed between resistors R2 and R3, and the other end is connected to operational amplifier U1.

[0015] Preferably, the operational amplifier U1 is connected in series with capacitors C6, C7, C8 and operational amplifier U2; resistor R5 is placed between capacitors C6 and C7; one end of resistor R6 is placed between capacitors C7 and C8, and the other end is connected to operational amplifier U2.

[0016] Preferably, resistors R7 and R8 are disposed between capacitor C1 and resistor R1; resistors R9 and R10 are disposed between capacitor C8 and operational amplifier U2; and resistors R7, R8, R9, and R10 are connected in series.

[0017] Compared with existing technologies, the bandpass filter for VHF DSC systems in this embodiment aims to overcome key problems such as signal distortion, increased bit error rate, call failure, and communication interruption caused by noise interference during VHF DSC audio signal transmission, ensuring communication stability. This bandpass filter innovatively adopts a cascaded architecture of low-pass and high-pass filters, operating in voltage follower mode via an operational amplifier, accurately achieving a passband characteristic of 1300Hz~2100Hz (center frequency of 1700Hz, passband bandwidth of 800Hz). Its core advantage lies in its ability to efficiently suppress out-of-band noise and AC ripple. By optimizing the signal waveform and improving signal quality, the processed clean signal is then sent to the decoding module and MCU for further processing, providing crucial support for the reliable operation of the VHF DSC system. Attached Figure Description

[0018] The above and other objects, features, and advantages of exemplary embodiments of the present disclosure will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the present disclosure are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein: Figure 1 This is a schematic diagram of a bandpass filter circuit proposed in this utility model; Figure 2 This is a schematic diagram of the passband range of a bandpass filter proposed in this utility model; Figure 3 This is a schematic diagram of a bandpass filter circuit proposed in this utility model. Detailed Implementation

[0019] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0020] The specific embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0021] Reference Figure 1 The diagram shows a schematic of a bandpass filter circuit according to an embodiment of the present invention, including: a low-pass filter unit, a high-pass filter unit, and a power supply bias unit; The low-pass filter unit and the high-pass filter unit are connected, and the power supply bias unit is connected to the low-pass filter unit and the high-pass filter unit respectively. The low-pass filter unit is used to suppress high-frequency noise interference above 2100Hz; the high-pass filter unit is used to filter out low-frequency noise interference below 1300Hz; a stable and matched operating voltage is provided to the operational amplifiers corresponding to the low-pass filter unit and the high-pass filter unit through a voltage divider method to ensure that the two-stage filter units are in the optimal working state.

[0022] like Figure 2 As shown, the passband of the bandpass filter is 1300Hz~2100Hz, the center frequency is 1700Hz, and the bandwidth is 800Hz; the low-pass filter is used to suppress low-frequency noise above 2100Hz; and the high-pass filter is used to suppress high-frequency noise below 1300Hz.

[0023] In this embodiment of the invention, the coordinated operation of these three circuits ultimately forms a bandpass filter with a passband range of 1300Hz to 2100Hz, a center frequency of 1700Hz, and a bandwidth of 800Hz, which can accurately match the transmission requirements of VHFDSC audio signals (1300Hz and 2100Hz). The bandpass filter for VHF DSC (Very High Frequency Digital Selective Calling) systems described in this invention aims to overcome key problems such as signal distortion, increased bit error rate, call failure, and communication interruption caused by noise interference during VHF DSC audio signal transmission, ensuring communication stability. This bandpass filter innovatively employs a cascaded architecture of a low-pass filter and a high-pass filter, operating in voltage follower mode via an operational amplifier, accurately achieving a passband characteristic of 1300Hz~2100Hz (center frequency of 1700Hz, passband bandwidth of 800Hz). Its core advantage lies in its efficient suppression of out-of-band noise and AC ripple. By optimizing the signal waveform and improving signal quality, the processed clean signal is then sent to the decoding module and MCU for further processing, providing crucial support for the reliable operation of the VHF DSC system.

[0024] Reference Figure 3The diagram shows a schematic of a bandpass filter circuit according to an embodiment of the present invention. The low-pass filter unit includes resistors R1, R2 and R3, capacitors C1, C2, C3 and C4, and operational amplifier U1.

[0025] Specifically, in this embodiment of the present invention, the high-pass filter unit includes resistor R5, resistor R6, capacitor C6, capacitor C7, capacitor C8, and operational amplifier U2.

[0026] In a further embodiment of this utility model, the power bias unit includes resistors R7, R8, R9, and R10.

[0027] In terms of circuit structure, capacitor C1 is connected in series with resistors R1, R2, R3, and operational amplifier U1; capacitor C2 is positioned between resistors R1 and R2; capacitor C3 is positioned between resistor R3 and operational amplifier U1; one end of capacitor C4 is positioned between resistors R2 and R3, and the other end is connected to operational amplifier U1.

[0028] In a further embodiment of this utility model, the operational amplifier U1 is connected in series with capacitors C6, C7, C8 and operational amplifier U2; resistor R5 is disposed between capacitors C6 and C7; one end of resistor R6 is disposed between capacitors C7 and C8, and the other end is connected to operational amplifier U2.

[0029] In this embodiment of the present invention, resistors R7 and R8 are disposed between capacitor C1 and resistor R1; resistors R9 and R10 are disposed between capacitor C8 and operational amplifier U2; and resistors R7, R8, R9, and R10 are connected in series.

[0030] In the foregoing description of this specification, unless otherwise expressly specified and limited, the terms "fixed," "installed," "connected," or "joined" should be interpreted broadly. For example, the term "joined" can refer to a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can refer to the internal communication of two components or the interaction between two components. Therefore, unless otherwise expressly limited in this specification, those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0031] Based on the above description in this specification, those skilled in the art will also understand that terms used, such as "upper," "lower," "front," "rear," "left," "right," "length," "width," "thickness," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," "circumferential," "center," "longitudinal," "transverse," "clockwise," or "counterclockwise," are terms indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings of this specification. They are only for the purpose of facilitating the explanation of the present invention and simplifying the description, and do not imply that the device or element involved must have the specific orientation, or be constructed and operated in a specific orientation. Therefore, the above-mentioned orientation or positional relationship terms should not be understood or interpreted as limitations on the present invention.

[0032] Furthermore, the terms "first" or "second," etc., used in this specification to refer to numbers or ordinal numbers are for descriptive purposes only and should not be construed as indicating, explicitly or implicitly, relative importance or specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this specification, "a plurality of" means at least two, such as two, three, or more, unless otherwise explicitly specified.

[0033] While this specification has shown and described various embodiments of the present invention, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and essence of the present invention. It should be understood that various alternatives to the embodiments of the present invention described herein may be employed in the practice of the present invention. The appended claims are intended to define the scope of protection of the present invention and therefore cover the modular compositions, equivalents, or alternatives within the scope of these claims.

Claims

1. A bandpass filter circuit, characterized by, include: Low-pass filter unit, high-pass filter unit, and power supply bias unit; The low-pass filter unit and the high-pass filter unit are connected, and the power supply bias unit is connected to the low-pass filter unit and the high-pass filter unit respectively. The low-pass filter unit is used to suppress high-frequency noise interference above 2100Hz; the high-pass filter unit is used to filter out low-frequency noise interference below 1300Hz; a stable and matched operating voltage is provided to the operational amplifiers corresponding to the low-pass filter unit and the high-pass filter unit through a voltage divider method to ensure that the two-stage filter units are in the best working state.

2. The bandpass filter circuit of claim 1, wherein, The low-pass filter unit includes resistors R1, R2, and R3.

3. The bandpass filter circuit of claim 2, wherein, The low-pass filter unit includes capacitors C1, C2, C3, and C4.

4. The bandpass filter circuit of claim 3, wherein, The low-pass filter unit includes an operational amplifier U1.

5. The bandpass filter circuit of claim 4, wherein, The high-pass filter unit includes resistors R5 and R6.

6. The bandpass filter circuit of claim 5, wherein, The high-pass filter unit includes capacitors C6, C7, and C8, and operational amplifier U2.

7. The bandpass filter circuit of claim 6, wherein, The power bias unit includes resistors R7, R8, R9, and R10.

8. The bandpass filter circuit of claim 7, wherein, The capacitor C1 is connected in series with the resistors R1, R2, R3 and the operational amplifier U1; the capacitor C2 is located between the resistors R1 and R2; the capacitor C3 is located between the resistors R3 and the operational amplifier U1; one end of the capacitor C4 is located between the resistors R2 and R3, and the other end is connected to the operational amplifier U1.

9. The bandpass filter circuit of claim 8, wherein, The operational amplifier U1 is connected in series with capacitors C6, C7, C8 and operational amplifier U2; resistor R5 is placed between capacitors C6 and C7; one end of resistor R6 is placed between capacitors C7 and C8, and the other end is connected to operational amplifier U2.

10. The bandpass filter circuit of claim 9, wherein, The resistors R7 and R8 are positioned between the capacitor C1 and the resistor R1; the resistors R9 and R10 are positioned between the capacitor C8 and the operational amplifier U2; the resistors R7, R8, R9, and R10 are connected in series.

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