Weak signal detection circuit

Abstract

The utility model discloses a weak signal detection circuit, and relates to the technical field of signal detection. Specifically, the non-inverting input end of a first comparator A1 is connected to a signal to be detected, and the inverting input end of the first comparator A1 is connected to the output end of a first amplifier D1; the non-inverting input end of the second comparator A2 is connected to the first power supply, and the inverting input end of the second comparator A2 is connected to the output end of the first amplifier D1; the first end of the bidirectional switch F is connected to the inverted input end of the first amplifier D1; the inverting input end of the third comparator A3 is connected with the second power supply circuit, the positive input end of the third comparator A3 is connected with a reference signal, and the output end of the third comparator A3 is connected with the base electrode of the triode Q1; the relay B1 controls the second end of the bidirectional switch F to be connected with the output end of the first comparator A1 or the output end of the second comparator A2. The objective of the utility model is to realize detection of weak signals when target signals are very weak and the frequency coverage range is wide.

Description

Technical Field

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

[0002] Visibility is a key indicator in meteorological monitoring, widely used in transportation, aerospace, navigation, environmental monitoring, and other fields. Accurate visibility measurement is crucial for ensuring public safety, improving traffic efficiency, and mitigating meteorological disasters.

[0003] Currently, there are many types of visibility measurement devices on the market, but forward-scattering visibility meters are widely used due to their simple structure, relatively low price, and easy maintenance. Forward-scattering visibility meters calculate atmospheric visibility by detecting the forward scattering of light by suspended particles in the air. They are particularly suitable for measuring visibility in low-visibility conditions.

[0004] The operating principle of a forward-scattering visibility meter is based on light scattering theory. At its core, a beam of light is emitted into the atmosphere. When this light encounters suspended particles in the air (such as fog, haze, and dust), it is scattered, with forward scattering being the most pronounced. By measuring the intensity of the forward-scattered light signal and combining it with parameters such as the scattering angle, the concentration of suspended particles in the atmosphere can be inferred, thereby estimating visibility.

[0005] However, one characteristic of forward scattered signals is that they are typically very weak, especially in high-visibility conditions. To accurately extract the weak forward scattered signal from the ambient background, traditional designs typically use a bandpass filter to eliminate unwanted interference signals, allowing only signals within a specific frequency range of the scattered light to pass. This approach can suppress ambient light interference to a certain extent, improving signal effectiveness and accuracy.

[0006] However, the practical application of bandpass filters has some limitations. First, the passband width of a bandpass filter is limited. As the passband width decreases, the difficulty and cost of manufacturing the filter increase significantly. Furthermore, the accuracy of a bandpass filter's frequency selectivity is physically limited. An overly narrow passband can cause signal distortion or loss of some effective information, affecting subsequent signal processing. This means that when the target signal is very weak and covers a wide frequency range, relying solely on bandpass filters for filtering is difficult to achieve ideal results, resulting in reduced visibility measurement accuracy.

[0007] Therefore, when the target signal is very weak and the frequency coverage range is wide, how to detect the weak signal has become a technical problem that needs to be solved urgently. Utility Model Content

[0008] The main purpose of the utility model is to provide a weak signal detection circuit, which aims to detect weak signals when the target signal is very weak and the frequency coverage range is wide.

[0009] In order to achieve the above object, the present invention proposes a weak signal detection circuit, comprising:

[0010] A first comparator A1, a second comparator A2, a third comparator A3, a first amplifier D1, a transistor Q1, a diode G1, a bidirectional switch F, and a relay B1;

[0011] The non-inverting input terminal of the first comparator A1 is connected to the signal to be measured, and the inverting input terminal of the first comparator A1 is connected to the output terminal of the first amplifier D1; the non-inverting input terminal of the second comparator A2 is connected to the first power supply, and the inverting input terminal of the second comparator A2 is connected to the output terminal of the first amplifier D1;

[0012] A first end of the bidirectional switch F is connected to an inverting input end of a first amplifier D1, a non-inverting input end of the first amplifier D1 is grounded, and an output end of the first amplifier D1 is connected to a low-pass filter;

[0013] The inverting input terminal of the third comparator A3 is connected to the second power supply circuit, the non-inverting input terminal of the third comparator A3 is connected to the reference signal, the output terminal of the third comparator A3 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to the cathode of the diode G1, the anode of the diode G1 is connected to the third power supply, and the emitter of the transistor Q1 is grounded;

[0014] The first end of the relay B1 is connected to the output end of the third comparator A3, and the second end of the relay B1 is connected to the first end of the bidirectional switch F, for controlling the second end of the bidirectional switch F to be conductive with the output end of the first comparator A1 or the output end of the second comparator A2.

[0015] In one embodiment of the present application, the second power supply circuit includes:

[0016] Resistor R1, resistor R2, resistor R3, and capacitor C1; wherein the first end of resistor R3 is connected to the inverting input end of the third comparator A3; the first end of resistor R1 is connected to the second power supply, the second end of resistor R1 is connected to the first end of resistor R2, the second end of resistor R2 is connected to the fourth power supply, the second end of resistor R3 is connected between the second end of resistor R1 and the first end of resistor R2, and the two ends of capacitor C1 are respectively connected to the two ends of resistor R2.

[0017] In one embodiment of the present application, a resistor R4 is connected in series between the diode G1 and the third power source.

[0018] In one embodiment of the present application, the first comparator A1 , the second comparator A2 , the third comparator A3 , the first amplifier D1 , the transistor Q1 , the bidirectional switch F, and the relay B1 are integrated into a chip.

[0019] In one embodiment of the present application, a capacitor C2 is further included, a first end of the capacitor C2 is connected to the positive end of the chip power supply voltage, and a second end of the capacitor C2 is connected to a fifth power supply.

[0020] In an embodiment of the present application, a capacitor C3 is further included, a first end of the capacitor C3 is connected to the negative end of the chip power supply voltage, and a second end of the capacitor C3 is connected to a sixth power supply.

[0021] The above technical solution, through the coordination of multiple comparators and amplifiers, can effectively distinguish the useful components of the measured signal from the reference signal, and remove high-frequency noise through a low-pass filter to achieve signal purification. Using a bidirectional switch F and relay B1 control, flexible switching between different signal sources is possible, allowing the circuit to process a variety of input signals and adapt to different detection needs. The first amplifier D1 can amplify weak signals and cooperate with the low-pass filter to further improve the signal-to-noise ratio, ensuring that the detected signal is accurate and reliable. The combination of transistor Q1 and diode G1 effectively prevents reverse current flow, protecting the stable operation of the entire circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0023] Figure 1 This is a schematic structural diagram of the first embodiment of the present utility model. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and do not constitute a limitation to the present invention.

[0025] like Figure 1 As shown, in order to achieve the above purpose, the utility model proposes a weak signal detection circuit, comprising:

[0026] A first comparator A1, a second comparator A2, a third comparator A3, a first amplifier D1, a transistor Q1, a diode G1, a bidirectional switch F, and a relay B1;

[0027] The non-inverting input terminal of the first comparator A1 is connected to the signal to be measured, and the inverting input terminal of the first comparator A1 is connected to the output terminal of the first amplifier D1; the non-inverting input terminal of the second comparator A2 is connected to the first power supply, and the inverting input terminal of the second comparator A2 is connected to the output terminal of the first amplifier D1;

[0028] A first end of the bidirectional switch F is connected to an inverting input end of a first amplifier D1, a non-inverting input end of the first amplifier D1 is grounded, and an output end of the first amplifier D1 is connected to a low-pass filter;

[0029] The inverting input terminal of the third comparator A3 is connected to the second power supply circuit, the non-inverting input terminal of the third comparator A3 is connected to the reference signal, the output terminal of the third comparator A3 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to the cathode of the diode G1, the anode of the diode G1 is connected to the third power supply, and the emitter of the transistor Q1 is grounded;

[0030] The first end of the relay B1 is connected to the output end of the third comparator A3, and the second end of the relay B1 is connected to the first end of the bidirectional switch F, for controlling the second end of the bidirectional switch F to be conductive with the output end of the first comparator A1 or the output end of the second comparator A2.

[0031] Specifically, the non-inverting input of the first comparator A1 is connected to the signal to be measured, the inverting input of the first comparator A1 is connected to the output of the first amplifier D1, and the output of the first comparator A1 can be connected to the second end of the bidirectional switch F. The non-inverting input of the second comparator A2 is connected to the first power supply, the inverting input of the second comparator A2 is connected to the output of the first amplifier D1, and the output of the second comparator A2 can be connected to the second end of the bidirectional switch F. The positive input of the third comparator A3 is connected to the reference signal. The inverting input of the third comparator A3 is connected to the second power supply circuit. The output of the third comparator A3 is connected to the base of the transistor Q1 and the first end of the relay B1.

[0032] The inverting input terminal of the first amplifier D1 is connected to the first terminal of the bidirectional switch F. The non-inverting input terminal of the first amplifier D1 is grounded. The output terminal of the first amplifier D1 is connected to the low-pass filter. The base of the transistor Q1 is connected to the output terminal of the third comparator A3. The collector of the transistor Q1 is connected to the cathode of the diode G1. The emitter of the transistor Q1 is grounded. The cathode of the diode G1 is connected to the collector of the transistor Q1. The anode of the diode G1 is connected to the third power supply. The first terminal of the relay B1 is connected to the output terminal of the third comparator A3. The second terminal of the relay B1 is connected to the first terminal of the bidirectional switch F.

[0033] A first end of the bidirectional switch F is connected to the inverting input of the first amplifier D1 , and a second end of the bidirectional switch F is controlled by the relay B1 and connected to the output of the first comparator A1 or the output of the second comparator A2 .

[0034] The first comparator A1 compares the difference between the measured signal and the amplifier output to generate an output signal. This is used to detect the relationship between the measured signal and the amplified signal and provide a signal to the bidirectional switch. The second comparator A2 compares the first power supply voltage with the amplifier output signal to generate an output signal. This is used to detect the difference between the power supply signal and the amplified signal and provide a reference signal for bidirectional switch control.

[0035] The third comparator A3 compares the reference signal with the voltage of the second power supply circuit, controls the transistor and the relay, controls the on and off of the relay, and further controls the working state of the bidirectional switch.

[0036] The first amplifier D1 amplifies the input signal, and its output is further processed by a low-pass filter. The input signal is amplified to provide an amplified signal for subsequent filtering and comparison.

[0037] Transistor Q1 is controlled by the third comparator A3 to conduct. When Q1 is on, current is allowed to flow through diode G1. As a switching element, it is controlled by the third comparator to determine whether current flows through the diode. Diode G1 controls the current flow direction, ensuring unidirectional current flow, thus protecting the circuit from reverse current flow. Bidirectional switch F controls signal switching, determining whether to connect to the first or second comparator based on the control of relay B1. It is used to switch signals, turning on or off between different comparators.

[0038] The relay B1 is controlled by the third comparator and is used to control the state of the bidirectional switch.

[0039] The circuit workflow is:

[0040] When the signal to be measured enters the circuit, it is compared by the first comparator A1 and then output to the first amplifier D1 through the bidirectional switch F. The first amplifier D1 amplifies the signal output by the first comparator A1 and generates a corresponding output signal.

[0041] The second comparator A2 compares the power signal with the signal output by the first amplifier D1 to determine whether a specific condition is met and generates a signal output.

[0042] The third comparator A3 controls transistor Q1 and relay B1 through the reference signal and the voltage of the second power supply circuit. In the initial state, relay B1 directs the first comparator A1, connecting the first comparator A1 to the first amplifier D1. When the reference signal is greater than the reference voltage provided by the second power supply circuit, the third comparator A3 outputs a high-level signal to trigger the relay, directing relay B1 to the second comparator A2, connecting the second comparator to the first amplifier D1.

[0043] The amplified signal passes through a low-pass filter to remove high-frequency noise and realize the detection and processing of weak signals.

[0044] The above technical solution, through the coordination of multiple comparators and amplifiers, can effectively distinguish the useful components of the measured signal from the reference signal, and remove high-frequency noise through a low-pass filter to achieve signal purification. Using a bidirectional switch F and relay B1 control, flexible switching between different signal sources is possible, allowing the circuit to process a variety of input signals and adapt to different detection needs. The first amplifier D1 can amplify weak signals and cooperate with the low-pass filter to further improve the signal-to-noise ratio, ensuring that the detected signal is accurate and reliable. The combination of transistor Q1 and diode G1 effectively prevents reverse current flow, protecting the stable operation of the entire circuit.

[0045] In one embodiment of the present application, the second power supply circuit includes:

[0046] Resistor R1, resistor R2, resistor R3, and capacitor C1; wherein the first end of resistor R3 is connected to the inverting input end of the third comparator A3; the first end of resistor R1 is connected to the second power supply, the second end of resistor R1 is connected to the first end of resistor R2, the second end of resistor R2 is connected to the fourth power supply, the second end of resistor R3 is connected between the second end of resistor R1 and the first end of resistor R2, and the two ends of capacitor C1 are respectively connected to the two ends of resistor R2.

[0047] Specifically, a first end of resistor R1 is connected to the second power supply. A second end of resistor R1 is connected to the first end of resistor R2 and to the second end of resistor R3. A first end of resistor R2 is connected to the second end of resistor R1. A second end of resistor R2 is connected to the fourth power supply, and both ends of capacitor C1 are connected to the ends of resistor R2. A first end of resistor R3 is connected to the inverting input of a third comparator A3. A second end of resistor R3 is connected between the second end of resistor R1 and the first end of resistor R2.

[0048] Resistors R1 and R2 form a voltage divider circuit, providing a stable voltage for resistor R3 and capacitor C1. This circuit is used to reduce the voltage of the second power supply and ensure voltage stability in subsequent circuits. Resistor R2 and capacitor C1 work together to filter signals. Together with resistor R1, they divide the voltage and adjust it to an appropriate voltage. Together with capacitor C1, they filter and suppress noise. Resistor R3 is connected to the inverting input of the third comparator A3, providing the comparator with a voltage regulated by the voltage divider circuit. This divided voltage is then directed to the inverting input of the third comparator A3 as a comparison reference voltage.

[0049] The circuit works as follows:

[0050] The voltage at the first terminal of resistor R1 is 3.3 V, and the voltage at the second terminal of resistor R2 is the voltage of the second power supply. As a result, the voltage between resistors R1 and R2 is fixed at the difference between 3.3 V and the voltage of the second power supply. Due to the circuit voltage division principle, the voltage between resistors R1 and R2 can be determined based on the ratio of resistors R1 to R2. This is the voltage output to the third comparator A3 through resistor R3. This voltage serves as a reference voltage for comparison with a reference signal, thereby controlling the output of the third comparator A3.

[0051] Using the aforementioned technical solution in reverse, the voltage divider circuit provides a stable reference voltage to the third comparator via resistors R1 and R2, enabling the comparator to accurately compare signals and avoiding errors caused by voltage fluctuations. The low-pass filter formed by capacitor C1 and resistor R2 effectively filters out high-frequency noise interference, making the circuit's operation more stable and reliable. Noise filtering is particularly important when detecting weak signals. The combination of resistors and capacitors also protects the third comparator from transient power supply interference, extending the circuit's service life.

[0052] In one embodiment of the present application, a resistor R4 is connected in series between the diode G1 and the third power source.

[0053] With this technical solution, resistor R4 limits the current through diode G1, preventing damage from overcurrent when the diode is conducting. Excessive current during forward conduction can cause the diode to overheat or even be damaged. The series resistor R4 limits the current, protecting the diode and the stable operation of the circuit.

[0054] In one embodiment of the present application, the first comparator A1 , the second comparator A2 , the third comparator A3 , the first amplifier D1 , the transistor Q1 , the bidirectional switch F, and the relay B1 are integrated into a chip.

[0055] Using the above technical solution, an integrated design integrates multiple components into a single chip, forming a phase-sensitive detector. This component includes a multiplier, a low-pass filter, and a reference signal source. The multiplier is the core component of the phase-sensitive detector. It multiplies the input signal and the reference signal to produce an output signal related to the phase difference between the two signals. The low-pass filter is used to filter out the high-frequency components in the multiplier output and extract the required DC or low-frequency signal. The reference signal source is used to generate a reference signal with the same frequency and a certain phase difference as the input signal. Integrating these components into a single chip significantly reduces the physical size of the entire circuit. The integrated design reduces external wiring, reduces problems such as poor contact, broken connections, and electromagnetic interference, and improves the system's reliability and anti-interference capabilities.

[0056] In one embodiment of the present application, a capacitor C2 is further included, a first end of the capacitor C2 is connected to the positive end of the chip power supply voltage, and a second end of the capacitor C2 is connected to a fifth power supply.

[0057] With the above technical solution, capacitor C2 and the power supply form a filter, which can smooth the power supply voltage and filter out high-frequency noise and interference in the power supply, reducing the impact of fluctuations on the chip and improving the circuit's anti-interference ability.

[0058] In an embodiment of the present application, a capacitor C3 is further included, a first end of the capacitor C3 is connected to the negative end of the chip power supply voltage, and a second end of the capacitor C3 is connected to a sixth power supply.

[0059] With the above technical solution, capacitor C3 and the power supply form a filter, which can smooth the power supply voltage and filter out high-frequency noise and interference in the power supply, reducing the impact of fluctuations on the chip and improving the circuit's anti-interference ability.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention specification and drawings under the utility model concept, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A weak signal detection circuit, characterized in that: include: A first comparator A1, a second comparator A2, a third comparator A3, a first amplifier D1, a transistor Q1, a diode G1, a bidirectional switch F, and a relay B1; The non-inverting input terminal of the first comparator A1 is connected to the signal to be measured, and the inverting input terminal of the first comparator A1 is connected to the output terminal of the first amplifier D1; the non-inverting input terminal of the second comparator A2 is connected to the first power supply, and the inverting input terminal of the second comparator A2 is connected to the output terminal of the first amplifier D1; A first end of the bidirectional switch F is connected to an inverting input end of a first amplifier D1, a non-inverting input end of the first amplifier D1 is grounded, and an output end of the first amplifier D1 is connected to a low-pass filter; The inverting input terminal of the third comparator A3 is connected to the second power supply circuit, the non-inverting input terminal of the third comparator A3 is connected to the reference signal, the output terminal of the third comparator A3 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to the cathode of the diode G1, the anode of the diode G1 is connected to the third power supply, and the emitter of the transistor Q1 is grounded; The first end of the relay B1 is connected to the output end of the third comparator A3, and the second end of the relay B1 is connected to the first end of the bidirectional switch F, for controlling the second end of the bidirectional switch F to be conductive with the output end of the first comparator A1 or the output end of the second comparator A2.

2. The weak signal detection circuit according to claim 1, wherein: The second power supply circuit includes: Resistor R1, resistor R2, resistor R3, and capacitor C1; wherein the first end of resistor R3 is connected to the inverting input end of the third comparator A3; the first end of resistor R1 is connected to the second power supply, the second end of resistor R1 is connected to the first end of resistor R2, the second end of resistor R2 is connected to the fourth power supply, the second end of resistor R3 is connected between the second end of resistor R1 and the first end of resistor R2, and the two ends of capacitor C1 are respectively connected to the two ends of resistor R2.

3. The weak signal detection circuit according to claim 1, wherein: A resistor R4 is connected in series between the diode G1 and the third power supply.

4. The weak signal detection circuit according to claim 1, wherein: The first comparator A1 , the second comparator A2 , the third comparator A3 , the first amplifier D1 , the transistor Q1 , the bidirectional switch F, and the relay B1 are integrated into a chip.

5. The weak signal detection circuit according to claim 4, wherein: It also includes a capacitor C2, a first end of the capacitor C2 is connected to the positive end of the chip power supply voltage, and a second end of the capacitor C2 is connected to a fifth power supply.

6. The weak signal detection circuit according to claim 4, wherein: It also includes a capacitor C3, a first end of the capacitor C3 is connected to the negative end of the chip power supply voltage, and a second end of the capacitor C3 is connected to the sixth power supply.

Images