Signal filter circuit and signal detection device

Abstract

The utility model discloses a signal filtering circuit and a signal detection device, and relates to the technical field of signal filtering. The signal filter circuit comprises an n-shaped LC filter circuit, an RC filter circuit and a decoupling capacitor circuit. The n-type LC filter circuit can filter out a first frequency component with the frequency higher than the first cut-off frequency of the n-type LC filter circuit. And the RC filter circuit can filter a second frequency component of which the frequency is lower than the second cut-off frequency of the RC filter circuit. Wherein the frequency of the second frequency component is lower than that of the first frequency component. The coupling capacitance circuit can further filter the environmental clutter component in the input signal. Therefore, components below the second cut-off frequency can be effectively filtered, and meanwhile, environmental clutter components can be removed, so that required pure signals are obtained. The circuit is easy to implement, durable, low in cost and suitable for sensor type signal detection devices such as needle pressure detection devices.

Description

Technical Field

[0001] The utility model relates to the technical field of signal filtering, in particular to a signal filtering circuit and a signal detection device. Background Art

[0002] Signal filtering circuits play an important role in electronic and communication systems. Their main function is to improve the performance and reliability of the system by removing or suppressing unnecessary components in the signal.

[0003] However, existing filters, such as active filters, are mostly complex in circuit implementation and high in cost, and are not suitable for signal filtering in sensor-type signal detection devices such as acupressure detection devices. Utility Model Content

[0004] The main purpose of the utility model is to provide a signal filtering circuit, aiming to solve the problem that the existing filtering circuit is complex in circuit implementation, high in cost and not suitable for signal filtering of sensor-type signal detection devices.

[0005] To achieve the above-mentioned purpose, the signal filtering circuit proposed in the present invention includes:

[0006] a Π-type LC filter circuit, wherein an input end of the Π-type LC filter circuit is connected to a signal input end of the signal filter circuit, and the Π-type LC filter circuit is used to filter out a first frequency component of an input signal;

[0007] an RC filter circuit, wherein the input end of the RC filter circuit is connected to the output end of the Π-type LC filter circuit, and the RC filter circuit is used to filter out a second frequency component of the input signal; wherein the frequency of the second frequency component is lower than the frequency of the first frequency component;

[0008] A decoupling capacitor circuit, wherein the input end of the decoupling capacitor circuit is connected to the output end of the RC filter circuit, and the output end of the decoupling capacitor circuit is connected to the signal output end of the signal filter circuit; the decoupling capacitor circuit is used to filter out the environmental noise components of the input signal.

[0009] In one embodiment, the Π-type LC filter circuit includes N-stage Π-type LC circuits, and the Π-type LC circuit has an input end and an output end;

[0010] When N is 1, the input end of the first-stage Π-type LC circuit is the input end of the Π-type LC filter circuit, and the output end of the first-stage Π-type LC circuit is the output end of the Π-type LC filter circuit;

[0011] When N is greater than 1, the N-stage Π-type LC circuits are connected in series with each other, the input end of the first-stage Π-type LC circuit is the input end of the Π-type LC filter circuit, and the output end of the N-stage Π-type LC circuit is the output end of the Π-type LC filter circuit.

[0012] In one embodiment, the Π-type LC circuit includes a first capacitor, a second capacitor, and a first inductor;

[0013] One end of the first capacitor and one end of the first inductor are connected to the input end of the Π-type LC circuit; the other end of the first inductor and one end of the second capacitor are connected to the output end of the Π-type LC circuit; the other end of the first capacitor and the other end of the second capacitor are grounded.

[0014] In one embodiment, the RC filter circuit includes an M-level RC circuit, wherein the RC circuit has an input terminal and an output terminal;

[0015] When M is 1, the input end of the first-stage RC circuit is the input end of the RC filter circuit, and the output end of the first-stage RC circuit is the output end of the RC filter circuit;

[0016] When M is greater than 1, the M-level RC circuits are connected in series with each other, the input end of the first-level RC circuit is the input end of the RC filter circuit, and the output end of the N-level RC circuit is the output end of the RC filter circuit.

[0017] In one embodiment, the RC circuit includes a first resistor and a third capacitor; one end of the first resistor is connected to the input end of the RC circuit; the other end of the first resistor and one end of the third capacitor are connected to the output end of the RC circuit; and the other end of the third capacitor is grounded.

[0018] In one embodiment, the decoupling capacitor circuit includes a fourth capacitor, one end of the fourth capacitor and the input end of the decoupling capacitor circuit are connected to the output end of the decoupling capacitor circuit, and the other end of the fourth capacitor is grounded.

[0019] In one embodiment, the capacitor is a chip capacitor or a plug-in capacitor.

[0020] The present utility model further provides a signal detection device, which includes the signal filtering circuit as described above.

[0021] In one embodiment, the signal detection device further includes a sensor and a signal processing chip, the signal output end of the sensor is connected to the signal input end of the signal filtering circuit, and the signal input end of the signal processing chip is connected to the signal output end of the signal filtering circuit.

[0022] In one embodiment, the sensor includes a first pressure-sensitive resistor, a second pressure-sensitive resistor, a third pressure-sensitive resistor, and a fourth pressure-sensitive resistor;

[0023] Among them, the power supply end of the sensor, one end of the first pressure-sensing resistor and one end of the second pressure-sensing resistor are connected; the first output end of the sensor, the other end of the second pressure-sensing resistor and one end of the fourth pressure-sensing resistor are connected; the ground end of the sensor, the other end of the fourth pressure-sensing resistor and one end of the third pressure-sensing resistor are connected; the second output end of the sensor, the other end of the third pressure-sensing resistor and the other end of the first pressure-sensing resistor are connected.

[0024] The technical solution of the present utility model adopts a signal filtering circuit, including a Π-type LC filter circuit, an RC filter circuit and a decoupling capacitor circuit. Among them, the Π-type LC filter circuit and the RC filter circuit can respectively filter out different frequency components in the input signal. Among them, the Π-type LC filter circuit can filter out noise components with frequencies higher than its first cut-off frequency; while the RC filter circuit can filter out noise components with frequencies lower than its second cut-off frequency. Among them, the first cut-off frequency is higher than the second cut-off frequency, which can ensure that useful signal components are retained between the two cut-off frequencies. The coupling capacitor circuit can further filter out environmental noise components in the input signal, especially when connected to a signal processing chip, it can effectively reduce interference from the chip's neighbors. In this way, the utility model can effectively filter out noise components below the second cut-off frequency and above the first cut-off frequency, while also removing environmental noise components, thereby obtaining a pure signal between the two cut-off frequencies. Since the utility model only contains capacitors, resistors and inductors, the circuit structure is simple, durable and low-cost, making it very suitable for sensor-type signal detection devices with strict cost requirements, such as acupressure detection devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0026] Figure 1 An electronic circuit diagram of an embodiment of a signal filtering circuit provided by the present utility model;

[0027] Figure 2 An electronic circuit diagram of another embodiment of the signal filtering circuit provided by the present invention;

[0028] Figure 3A schematic structural diagram of an embodiment of a signal detection device provided by the present invention;

[0029] Figure 4 This is an electronic circuit diagram of a sensor of an embodiment of a signal detection device provided by the present invention.

[0030] Description of Figure Numbers:

[0031]

[0032] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0035] In addition, the descriptions of "first," "second," etc. in this utility model are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this utility model.

[0036] Existing sensor-based signal detection devices typically use active filters, such as operational amplifier filters, for filtering. This results in complex circuit implementation and high cost. However, in cost-sensitive sensor-based signal detection devices, such as acupressure detection devices, these active filters are no longer suitable. Therefore, a simple, low-cost, durable, and reliable filtering circuit is urgently needed.

[0037] The present invention provides a signal filtering circuit 100 .

[0038] See also Figure 1 In one embodiment of the present invention, the signal filtering circuit 100 includes:

[0039] The Π-type LC filter circuit 110 has an input end connected to the signal input end of the signal filter circuit 100, and is used to filter out the first frequency component of the input signal.

[0040] An RC filter circuit 120, wherein the input end of the RC filter circuit 120 is connected to the output end of the Π-type LC filter circuit 110, and the RC filter circuit 120 is used to filter out a second frequency component of the input signal; wherein the frequency of the second frequency component is lower than the frequency of the first frequency component;

[0041] The decoupling capacitor circuit 130 has its input connected to the output of the RC filter circuit 120 and its output connected to the signal output of the signal filter circuit 100. The decoupling capacitor circuit 130 is used to filter out environmental noise components of the input signal.

[0042] In this embodiment, the Π-type LC filter circuit 110 can be composed of two capacitors placed on both sides and an inductor placed between the two sides to form a Π-type circuit, which can be used for filtering. It should be noted that the Π-type LC filter circuit 110 can be used to filter out medium- and high-frequency clutter components of the input signal. Based on the values ​​of the capacitors and inductors, the Π-type LC filter circuit 110 can be set to a specific first cutoff frequency, and can filter out clutter components above the second cutoff frequency, that is, filter out the first frequency component of the input signal.

[0043] In this embodiment, the RC filter circuit 120 can be composed of a resistor and a capacitor and can be used for filtering. It should be noted that the RC filter circuit 120 can be used to filter out low- and medium-frequency noise components of the input signal. Based on the values ​​of the resistor and capacitor, the RC filter circuit 120 can be set to a specific second cutoff frequency, thereby filtering out noise components below the second cutoff frequency, that is, filtering out the second frequency component of the input signal.

[0044] In this embodiment, the decoupling capacitor circuit 130 can be composed of a single capacitor and can be used to filter out DC bias or low-frequency noise in the circuit. It should be noted that power supply fluctuations, electromagnetic interference, and interference caused by the switching or operation of electrical equipment in the circuit environment can easily cause environmental noise. When the signal filtering circuit 100 provided in this embodiment is connected to a signal processing chip, the capacitor in the decoupling capacitor circuit 130 can be placed close to the signal input terminal of the signal processing chip to filter out interference from the chip's neighboring devices.

[0045] It should be noted that the capacitor in this embodiment may be a chip capacitor or a plug-in capacitor.

[0046] In this embodiment, the Π-type LC filter circuit 110 can filter out the first frequency component of the input signal, and the RC filter circuit 120 can filter out the second frequency component of the input signal. Among them, the first frequency component is a noise component with a frequency higher than the first cut-off frequency of the Π-type LC filter circuit 110, and the second frequency component is a noise component with a frequency lower than the second cut-off frequency of the RC filter circuit 120, and the first cut-off frequency is higher than the second cut-off frequency. The coupling capacitor circuit can filter out the environmental noise component of the input signal, and when connected to a signal processing chip, it can filter out the chip's neighboring interference. In this way, this embodiment can filter out the noise components and environmental noise components outside the second cut-off frequency and the first cut-off frequency, and obtain a pure signal between the second cut-off frequency and the first cut-off frequency. Moreover, this embodiment only includes capacitors, resistors, and inductors, so the circuit is relatively simple, durable, and low-cost, and is suitable for sensor-type signal detection devices with relatively strict cost requirements, such as acupressure detection devices.

[0047] In the present invention, a Π-type LC filter circuit 110 and an RC filter circuit 120 are used to filter out different frequency components in the input signal respectively. Among them, the Π-type LC filter circuit 110 can filter out the noise components with frequencies higher than its first cut-off frequency; while the RC filter circuit 120 filters out the noise components with frequencies lower than its second cut-off frequency. In addition, the first cut-off frequency is higher than the second cut-off frequency, which can ensure that useful signal components are retained between the two cut-off frequencies. The coupling capacitor circuit can further filter out the environmental noise components in the input signal, especially when connected to a signal processing chip, it can effectively reduce the interference from the chip's neighbors. In this way, the present invention can effectively filter out the noise components below the second cut-off frequency and above the first cut-off frequency, and at the same time remove the environmental noise components, thereby obtaining a pure signal between the two cut-off frequencies. Since the present invention only contains capacitors, resistors and inductors, the circuit structure is simple, durable and low-cost, and is very suitable for sensor-type signal detection devices with strict cost requirements, such as acupressure detection devices.

[0048] See also Figure 2 In one embodiment of the present invention, the Π-type LC filter circuit 110 includes N-stage Π-type LC circuits 111, and the Π-type LC circuit 111 has an input end and an output end;

[0049] When N is 1, the input end of the first-stage Π-type LC circuit 111 is the input end of the Π-type LC filter circuit 110, and the output end of the first-stage Π-type LC circuit 111 is the output end of the Π-type LC filter circuit 110;

[0050] When N is greater than 1, N stages of π-type LC circuits 111 are connected in series with each other, the input end of the first stage of the π-type LC circuit 111 is the input end of the π-type LC filter circuit 110, and the output end of the Nth stage of the π-type LC circuit 111 is the output end of the π-type LC filter circuit 110.

[0051] It should be noted that N is a positive integer.

[0052] In one embodiment, N is 1, and the Π-type LC filter circuit 110 is a first-stage Π-type LC circuit, including a Π-type LC circuit segment. It has a relatively simple frequency response, a simple structure, and is easy to design and implement. It is suitable for filtering sensor input signals with less stringent frequency requirements.

[0053] It should be noted that the transition band (the transition region from the passband to the stopband) of a single-stage π-type LC circuit is relatively wide, resulting in a relatively flat filtering slope, which cannot provide sufficient filtering depth and accuracy. To improve filtering depth and accuracy, in another embodiment, the π-type LC filter circuit 110 is an N-stage π-type LC circuit, where N is greater than 1. A more complex frequency response curve can be achieved by cascading multiple π-type LC circuit segments. As the number of stages increases, the transition band becomes steeper and the filtering slope also becomes steeper. This enables the filter to more accurately control the frequency response and is suitable for high-precision sensor signal processing scenarios requiring higher-order filtering characteristics.

[0054] See also Figure 2 In one embodiment of the present invention, the Π-type LC circuit 111 includes a first capacitor C1, a second capacitor C2 and a first inductor L1;

[0055] One end of the first capacitor C1 and one end of the first inductor L1 are connected to the input end of the Π-type LC circuit 111; the other end of the first inductor L1 and one end of the second capacitor C2 are connected to the output end of the Π-type LC circuit 111; the other end of the first capacitor C1 and the other end of the second capacitor C2 are grounded.

[0056] In this embodiment, the first capacitor C1 primarily filters out AC components in the low- to medium-frequency range, as the capacitive reactance of a capacitor increases with decreasing frequency. Connected in parallel in the circuit, it allows DC and medium- and low-frequency components to pass through. The first inductor L1 primarily filters out high-frequency AC components, as the inductive reactance of an inductor increases with increasing frequency. Connected in series in the circuit, it blocks high-frequency AC components while allowing DC and medium- and low-frequency components to pass through. To prevent the circuit from resonating with components within the circuit at a certain frequency, or the transmitted signal from resonating with the circuit formed by the first capacitor C1 and the first inductor L1, which could affect the normal operation of the circuit, a second capacitor C2 is added at the output end to form a Pi-type LC circuit 111.

[0057] It should be noted that, considering signal transmission, the characteristic impedance of the Π-type LC circuit 111 can be designed to be 50Ω, and the calculation formula is: (Here, L is the inductance of the inductor in the π-type LC circuit 111, measured in Henrys; C is the capacitance of the capacitor, measured in Coulombs, and the calculated result is expressed in Ω.) Furthermore, the characteristic impedance of the wiring on the PCB can be set to 50Ω to achieve impedance matching and reduce signal reflections along the transmission path. Thus, the π-type LC circuit 111 of this embodiment exhibits virtually no insertion loss.

[0058] See also Figure 2 In one embodiment of the present invention, the RC filter circuit 120 includes an M-stage RC circuit 121, and the RC circuit 121 has an input terminal and an output terminal;

[0059] When M is 1, the input end of the first-stage RC circuit 121 is the input end of the RC filter circuit 120, and the output end of the first-stage RC circuit 121 is the output end of the RC filter circuit 120;

[0060] When M is greater than 1, M stages of RC circuits 121 are connected in series, the input end of the first stage RC circuit 121 is the input end of the RC filter circuit 120 , and the output end of the Mth stage RC circuit 121 is the output end of the RC filter circuit 120 .

[0061] It should be noted that M is a positive integer.

[0062] In one embodiment, M is 1, and the RC filter circuit 120 is a first-stage RC circuit including one RC circuit segment. It has a relatively simple frequency response, a simple structure, and is easy to design and implement. It is suitable for filtering sensor input signals with less stringent frequency requirements.

[0063] It should be noted that if the transition band (the transition region from the passband to the stopband) of a first-stage RC circuit is wide, its filtering slope will be relatively flat, and it will not provide sufficient filtering depth and accuracy. To improve filtering depth and accuracy, in another embodiment, the RC filter circuit 120 is an M-stage RC circuit, where M is greater than 1, and a more complex frequency response curve can be achieved by cascading multiple RC circuit segments. As the number of stages increases, the transition band becomes steeper and the filtering slope becomes steeper, which enables the filter to more accurately control the frequency response and is suitable for high-precision sensor signal processing scenarios that require higher-order filtering characteristics.

[0064] See also Figure 2In one embodiment of the present invention, the RC circuit 121 includes a first resistor R1 and a third capacitor C3; one end of the first resistor R1 is connected to the input end of the RC circuit 121; the other end of the first resistor R1 and one end of the third capacitor C3 are connected to the output end of the RC circuit 121; the other end of the third capacitor C3 is grounded.

[0065] In this embodiment, the first resistor R1 can be set to 50Ω, and the capacitance of the third capacitor C3 can be set at the uF level. This can achieve the purpose of passing direct current, reducing the amplitude of the AC signal, and preventing high-frequency noise and clutter. When the RC circuit 121 is connected in series with the Π-type LC filter circuit 110 of the previous stage, the third capacitor C3 (the capacitance is usually at the uF level) and the previous stage Π-type LC filter circuit 110 (its capacitance is usually at the nF level) can form a combined capacitive filtering structure. The capacitance of the previous stage Π-type LC filter circuit 110 is relatively small and the impedance is relatively large, which is mainly responsible for filtering out high-frequency clutter. The capacitance of the RC circuit 121 of this stage is relatively large and the impedance is relatively small, which can further reduce the AC component of noise and harmonics other than direct current, thereby better filtering out clutter. In this way, the DC component is maintained, while the AC component of high-frequency noise and clutter at this stage is significantly reduced. In addition, the filtering structure composed of the resistor of this stage and the capacitor of the decoupling capacitor circuit 130 of the subsequent stage can effectively filter out clutter interference. Among them, the resistor can evenly consume all the current components passing through, including signals and interference, thereby helping to further suppress clutter.

[0066] See also Figure 2 In one embodiment of the present invention, the decoupling capacitor circuit 130 includes a fourth capacitor C4, one end of the fourth capacitor C4, the input end of the decoupling capacitor circuit 130 and the output end of the decoupling capacitor circuit 130 are connected, and the other end of the fourth capacitor C4 is grounded.

[0067] It should be noted that the capacitance of the fourth capacitor C4 can be determined based on the frequency of the noise on the power line. For example, high-frequency noise requires a smaller capacitance (e.g., 0.1 μF), while low-frequency noise requires a larger capacitance (e.g., 10 μF). To cover a wider frequency range, in one embodiment, the decoupling capacitor circuit 130 may further include multiple capacitors of different capacitances connected in parallel to form the fourth capacitor C4 for filtering out noise.

[0068] The present invention also proposes a signal detection device, which includes a signal filtering circuit 100. The specific structure of the signal filtering circuit 100 refers to the above embodiment. Since the signal detection device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0069] See also Figure 3In one embodiment of the present invention, the signal detection device also includes a sensor 200 and a signal processing chip 300, the signal output end of the sensor 200 is connected to the signal input end of the signal filtering circuit 100, and the signal input end of the signal processing chip 300 is connected to the signal output end of the signal filtering circuit 100.

[0070] In this embodiment, the sensor 200 can collect electrical signals corresponding to various physical phenomena. The signal filtering circuit 100 then filters the original electrical signal output by the sensor 200 in order to retain useful signal components and transmit these pure signals to the signal processing chip 300. The signal processing chip 300 can further process and analyze this part of useful signals to obtain the final result data. Among them, the sensor 200 can be a temperature detection sensor, a piezoelectric sensor, an accelerometer, etc. The signal processing chip 300 may include an analog front-end circuit, a microcontroller, etc., for performing tasks such as signal amplification, digitization, and analysis. The result data can be used for monitoring, control, or feedback to other systems.

[0071] See also Figure 4 In one embodiment of the present invention, the sensor 200 includes a first pressure-sensing resistor RV1, a second pressure-sensing resistor RV2, a third pressure-sensing resistor RV3 and a fourth pressure-sensing resistor RV4;

[0072] Among them, the power supply terminal VDD of the sensor 200, one end of the first pressure-sensing resistor RV1 and one end of the second pressure-sensing resistor RV2 are connected; the first output terminal V1 of the sensor 200, the other end of the second pressure-sensing resistor RV2 and one end of the fourth pressure-sensing resistor RV4 are connected; the ground terminal GND of the sensor 200, the other end of the fourth pressure-sensing resistor RV4 and one end of the third pressure-sensing resistor RV3 are connected; the second output terminal V2 of the sensor 200, the other end of the third pressure-sensing resistor RV3 and the other end of the first pressure-sensing resistor RV1 are connected.

[0073] In this embodiment, the first pressure-sensing resistor RV1 , the second pressure-sensing resistor RV2 , the third pressure-sensing resistor RV3 and the fourth pressure-sensing resistor RV4 form a bridge pressure sensor, which can be applied to signal detection devices such as acupuncture pressure detection devices.

[0074] See also Figure 1 、 Figure 2 、 Figure 3 and Figure 4In one embodiment of the present invention, the sensor 200 can be a bridge-type pressure sensor composed of 4 chip resistors, powered by a DC power supply VDD (specifically 5V), and the sensed pressure is a differential signal of common mode VDD / 2. The normal voltage range of the differential signal is 0.2uV to 200uV, generally 30uV; the detection feature involved is that the differential signal is not static, but dynamically intermittent, with a dynamic detection cycle every approximately 50ms. Within one cycle, the pressure increases from zero to a maximum value, stabilizes for approximately 20ms in the middle, and then quickly returns to zero. Each cycle should be detected approximately 40 times, so the dynamic time-varying detection frequency is 800Hz.

[0075] In this embodiment, the Π-type LC filter circuit 110 can be a first-stage Π-type LC circuit or a second-stage Π-type LC circuit. The Π-type LC filter circuit 110 mainly filters out the mid- and high-frequency parts of the signal, has a filter cutoff frequency of approximately 150 kHz, and a characteristic impedance of approximately 50Ω.

[0076] The RC filter circuit 120 can be a first-level RC circuit, which mainly filters out the medium and low frequency parts in the signal, with a filter cut-off frequency of about 3KHz and a series direct impedance of about 50Ω. The decoupling capacitor circuit 130 mainly removes environmental interference near the pins of the signal processing chip 300, and the filter frequency is about a universal 0.3MHz. Specifically, the first inductor L1 can be a molded package inductor. Among them, the inductance value of the inductor is 47uH, the tolerance of the inductance value is ±10%, the maximum allowable current passing through the inductor is 350mA, and the package size of the inductor is 3 mm x 3 mm x 1.5 mm. Specifically, the first capacitor C1 and the second capacitor C2 can be the same chip capacitor. Among them, the capacitance value is 20nF, the tolerance is ±10%, the operating voltage of the capacitor is 50V, the dielectric material of the capacitor is X5R material (a dielectric type of ceramic capacitor), and the package size of the capacitor is 0.06 inches x 0.03 inches.

[0077] It should be noted that when the Π-type LC filter circuit 110 is a first-stage Π-type LC circuit and the RC filter circuit 120 is a first-stage RC circuit, noise and interference three times or more of the fundamental frequency signal (800Hz) in the output signal of the bridge pressure sensor are basically filtered out (a cutoff frequency that is too low will damage the fundamental frequency signal), and the coupled noise of the environmental circuit is filtered out when the signal enters the signal processing chip 300, and the signal transmission reflection is small and the loss is low.

[0078] It should be noted that to improve filtering depth and accuracy, the π-type LC filter circuit 110 can be configured as a two-stage π-type LC circuit, and the RC filter circuit 120 as a single-stage RC circuit. In this case, noise and interference three times or more of the fundamental frequency signal (800 Hz) in the output signal of the bridge pressure sensor can be better filtered out. Coupled noise from the environmental circuit is also filtered out when the signal enters the signal processing chip 300, and signal transmission has minimal reflections and losses. This results in more accurate detection results derived from analysis and processing by the signal processing chip 300.

[0079] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A signal filtering circuit, characterized in that: include: a Π-type LC filter circuit, wherein an input end of the Π-type LC filter circuit is connected to a signal input end of the signal filter circuit, and the Π-type LC filter circuit is used to filter out a first frequency component of an input signal; an RC filter circuit, wherein the input end of the RC filter circuit is connected to the output end of the Π-type LC filter circuit, and the RC filter circuit is used to filter out a second frequency component of the input signal; wherein the frequency of the second frequency component is lower than the frequency of the first frequency component; A decoupling capacitor circuit, wherein the input end of the decoupling capacitor circuit is connected to the output end of the RC filter circuit, and the output end of the decoupling capacitor circuit is connected to the signal output end of the signal filter circuit; the decoupling capacitor circuit is used to filter out the environmental noise components of the input signal.

2. The signal filtering circuit according to claim 1, wherein: The Π-type LC filter circuit includes N-stage Π-type LC circuits, and the Π-type LC circuit has an input end and an output end; When N is 1, the input end of the first-stage Π-type LC circuit is the input end of the Π-type LC filter circuit, and the output end of the first-stage Π-type LC circuit is the output end of the Π-type LC filter circuit; When N is greater than 1, the N-stage Π-type LC circuits are connected in series with each other, the input end of the first-stage Π-type LC circuit is the input end of the Π-type LC filter circuit, and the output end of the N-stage Π-type LC circuit is the output end of the Π-type LC filter circuit.

3. The signal filtering circuit according to claim 2, wherein: The Π-type LC circuit includes a first capacitor, a second capacitor and a first inductor; One end of the first capacitor and one end of the first inductor are connected to the input end of the Π-type LC circuit; the other end of the first inductor and one end of the second capacitor are connected to the output end of the Π-type LC circuit; the other end of the first capacitor and the other end of the second capacitor are grounded.

4. The signal filtering circuit according to claim 1, wherein: The RC filter circuit includes an M-level RC circuit, and the RC circuit has an input end and an output end; When N is 1, the input end of the first-stage RC circuit is the input end of the RC filter circuit, and the output end of the first-stage RC circuit is the output end of the RC filter circuit; When N is greater than 1, the M-level RC circuits are connected in series with each other, the input end of the first-level RC circuit is the input end of the RC filter circuit, and the output end of the N-level RC circuit is the output end of the RC filter circuit.

5. The signal filtering circuit according to claim 4, wherein: The RC circuit includes a first resistor and a third capacitor; one end of the first resistor is connected to the input end of the RC circuit; the other end of the first resistor and one end of the third capacitor are connected to the output end of the RC circuit; the other end of the third capacitor is grounded.

6. The signal filtering circuit according to claim 1, wherein: The decoupling capacitor circuit includes a fourth capacitor, one end of the fourth capacitor and the input end of the decoupling capacitor circuit are connected to the output end of the decoupling capacitor circuit, and the other end of the fourth capacitor is grounded.

7. The signal filtering circuit according to any one of claims 3, 5 and 6, wherein: The capacitor is a chip capacitor or a plug-in capacitor.

8. A signal detection device, characterized in that: The method comprises the signal filtering circuit according to any one of claims 1 to 7.

9. The signal detection device according to claim 8, wherein: The signal detection device further includes a sensor and a signal processing chip. The signal output end of the sensor is connected to the signal input end of the signal filtering circuit, and the signal input end of the signal processing chip is connected to the signal output end of the signal filtering circuit.

10. The signal detection device according to claim 9, wherein: The sensor includes a first pressure-sensitive resistor, a second pressure-sensitive resistor, a third pressure-sensitive resistor and a fourth pressure-sensitive resistor; Among them, the power supply end of the sensor, one end of the first pressure-sensing resistor and one end of the second pressure-sensing resistor are connected; the first output end of the sensor, the other end of the second pressure-sensing resistor and one end of the fourth pressure-sensing resistor are connected; the ground end of the sensor, the other end of the fourth pressure-sensing resistor and one end of the third pressure-sensing resistor are connected; the second output end of the sensor, the other end of the third pressure-sensing resistor and the other end of the first pressure-sensing resistor are connected.

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