Radar sensing system suitable for intelligent furniture and sensing processing method
By combining a microwave transceiver module, a signal conditioning module, and a control and judgment module, the gain is dynamically adjusted to solve the interference and detection range adjustment problems of the radar sensing system, thereby achieving stable signal amplification and reliable detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LUOHE HONGHUANGLAN EIECTRONIC TECH CO LTD
- Filing Date
- 2026-02-04
- Publication Date
- 2026-04-28
AI Technical Summary
Existing radar sensing systems are susceptible to interference and their detection range cannot be adjusted flexibly and reliably.
It employs a microwave transceiver module, a signal conditioning module, and a control and judgment module. Gain closed-loop control is achieved through a gain-adjustable amplification unit and a feedback unit. Combined with signal filtering and amplification, the gain is dynamically adjusted to adapt to different scenarios, and the sensitivity is configured in conjunction with wireless communication.
It achieves stable signal amplification and reliable detection in different scenarios, suppresses interference, and ensures flexible adjustment of detection distance and system reliability.
Smart Images
Figure CN121934070A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of smart home technology, specifically to a radar sensing system and sensing processing method suitable for smart furniture. Background Technology
[0002] With the advancement of IoT and smart home technologies, furniture products are gradually evolving towards intelligence, user-friendliness, and energy efficiency. Among these, furniture control products such as vanity light controllers, smart mirror controllers, and cabinet light controllers commonly integrate human body sensing functionality to achieve automatic control effects such as "lights turn on when someone is present and turn off when they leave" or "lights remain on when someone is present." This automatic sensing control not only greatly enhances user experience and convenience but also achieves energy conservation and consumption reduction.
[0003] The inventors know that existing radar sensing methods mostly employ a simplified Doppler radar detection principle, utilizing peak detection of the induced signal to achieve radar sensing. That is, when an object is active nearby, the phase deviation between the received microwave signal and the transmitted signal, based on a composite microwave oscillation transmitting and receiving circuit, corresponds to a low-frequency shift signal. This shift signal is then compared by a comparator, and when the amplitude of the shift signal exceeds a certain value (a judgment threshold), a control signal is output, indicating the presence of a human or object activity.
[0004] However, the inventors of this application have discovered through long-term practice and research that in the traditional simple Doppler radar detection process, effective signal discrimination is based on a fixed gain amplifier and a comparison lock circuit. When the judgment threshold is lowered, there will be a problem of significant signal attenuation in scenarios such as near metal and walls, making it difficult to achieve effective signal detection and impossible to adjust the detection distance in different scenarios.
[0005] The information disclosed in this background section is intended only to enhance the understanding of the background technology of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention
[0006] In view of at least one of the above technical problems, this disclosure provides a radar sensing system and sensing processing method suitable for smart furniture, mainly solving the technical problems that existing radar sensing systems are susceptible to interference and the detection distance cannot be flexibly and reliably adjusted.
[0007] According to one aspect of this disclosure, a radar sensing system suitable for smart furniture is provided, comprising a microwave transceiver module for transmitting and receiving microwave signals and correspondingly outputting frequency shift-varying signals; a signal conditioning module electrically connected downstream of the signal output terminal of the microwave transceiver module for filtering and amplifying the frequency shift-varying signals and including at least one gain-adjustable amplification unit; and a control judgment module electrically connected to the signal conditioning module. The control judgment module includes a gain control unit for generating PWM control signals to dynamically adjust the gain of the gain-adjustable amplification unit; a feedback unit for acquiring the operating parameters of the gain-adjustable amplification unit to achieve closed-loop control of the gain of the gain-adjustable amplification unit; a signal judgment unit for receiving the conditioned frequency shift-varying signals and judging the target activity state; and a wireless communication unit for wirelessly communicating with an external terminal to receive configuration commands and / or sensing states.
[0008] In some embodiments of this disclosure, the radar sensing system further includes a voltage regulator unit for providing a stable voltage to the microwave transceiver module, the signal conditioning module, and the control judgment module.
[0009] In some embodiments of this disclosure, the microwave transceiver module includes an oscillator and mixer circuit based on a microwave transistor.
[0010] In some embodiments of this disclosure, the signal conditioning module includes a low-pass filter unit, a pre-amplifier unit, and the gain-adjustable amplification unit connected sequentially from upstream to downstream; the pre-amplifier unit includes a first operational amplifier whose inverting input terminal is electrically connected to the output terminal of the low-pass filter unit through a DC blocking capacitor and whose static output voltage is the midpoint voltage, and a first-order low-pass filter circuit disposed in the feedback channel of the first operational amplifier for filtering frequency-shifted signals.
[0011] In some embodiments of this disclosure, the gain-adjustable amplification unit includes a second operational amplifier and a gain-regulating MOS transistor whose drain is electrically connected to the inverting input terminal of the second operational amplifier; the gate of the gain-regulating MOS transistor is electrically connected to the PWM signal output port of the gain control unit.
[0012] In some embodiments of this disclosure, the PWM signal output by the gain control unit is filtered by a second-order low-pass filter to adjust the gain-adjustable amplification unit accordingly.
[0013] According to another aspect of this disclosure, a sensing processing method for a radar sensing system is provided, which is implemented based on the above-described radar sensing system and includes the following steps: (1) The microwave transceiver module transmits microwaves to the detection area and receives microwave reflected signals, and outputs corresponding sensing signals; the sensing signals are filtered and amplified based on the signal conditioning module. (2) The gain control unit outputs a PWM signal to adjust the gain of the gain-adjustable amplifier unit, and at the same time monitors the gain status of the gain-adjustable amplifier unit through the feedback unit and adjusts the duty cycle of the PWM signal accordingly until the gain-adjustable amplifier unit converges to the target gain. (3) The signal judgment unit performs analog-to-digital conversion on the conditioned induction signal and samples it accordingly to obtain a discrete sampling sequence; (4) Calculate the DC component of the sampling sequence within the initial predetermined time window; after calculating the cumulative sum of the absolute values of the differences between each sampling point in the sampling sequence and the DC component within the sensing time window, obtain the activity index value characterizing the intensity of the target activity; (5) Compare the activity index value with a preset judgment threshold, and determine that there is a valid target activity in the detection area when the activity index value exceeds the preset judgment threshold.
[0014] In some embodiments of this disclosure, in step (4), the anti-interference capability of the radar sensing system is improved by increasing the duration of the sensing time window.
[0015] In some embodiments of this disclosure, in step (5), the judgment threshold is dynamically adjusted according to the sensitivity setting instruction received by the wireless communication unit, and the judgment threshold is inversely proportional to the sensitivity.
[0016] One or more technical solutions provided in the embodiments of this application have at least one of the following technical effects or advantages: 1. The pre-amplification unit provides preliminary and stable amplification of weak signals with a narrow amplitude range, suppressing signal noise and ensuring stability. The gain-adjustable amplification unit ensures that any effective signal of any strength can be amplified to a suitable processing level without distortion, thus avoiding the problem that a fixed gain amplifier will cause saturation distortion of strong signals at close range when the gain is too high, and make it difficult to capture weak signals at long distance when the gain is too low.
[0017] 2. Through sampling feedback closed-loop calibration, the control judgment module can dynamically and accurately calibrate and lock the gain of the gain-adjustable amplifier unit, thereby actively compensating for the amplification gain deviation caused by factors such as the discreteness of device parameters and changes in operating temperature in the circuit. This ensures the high consistency of product performance in mass production and the long-term stability of the product within the allowable operating environment range, thus ensuring the reliability of the system operation.
[0018] 3. In the processing of the sensed signal, by establishing a DC component and using the accumulation of the absolute value of the deviation, combined with a flexibly configurable sensing time window, short-term pulse interference and slowly changing environmental noise can be effectively suppressed; and through the dynamic configuration of sensitivity via wireless communication, users can configure appropriate sensitivity according to specific application scenarios (such as bathrooms, kitchens, corridors, etc.), thereby achieving a balance between detection distance, micro-motion recognition, and avoiding false judgments and false alarms. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the overall circuit of a radar sensing system in one embodiment of this application.
[0020] In the above figures, 1 is the microwave transceiver module, 2 is the low-pass filter unit, 3 is the pre-amplifier unit, 4 is the gain-adjustable amplifier unit, 5 is the control and judgment module, and 6 is the voltage regulated power supply unit. Detailed Implementation
[0021] The programs involved or relied upon in the following embodiments are all conventional or simple programs in this technical field, and those skilled in the art can make conventional selections or adaptive adjustments according to specific application scenarios. Unless otherwise specified, the components involved in the following embodiments are all conventional commercially available products.
[0022] To better understand the technical solution of this application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific embodiments.
[0023] To address the technical problems of existing radar sensing systems being susceptible to interference and having inflexible and unreliable adjustment of detection range, see [reference needed]. Figure 1 This example discloses a radar sensing system suitable for smart furniture.
[0024] In this embodiment, to detect moving targets within the detection area, a microwave transceiver module is used to oscillate and transmit microwave signals. The phase deviation between the reflected microwave signal and the transmitted signal is used to reflect the activity of the target within the detection area. For details, see [link to details]. Figure 1In this example, an oscillator and mixer circuit is built around a microwave transistor Q201, which, together with an antenna ANT, enables microwave transmission and reception. The microwave oscillation circuit in this example relies heavily on the PCB layout. Specifically, different layouts of corresponding transmission lines on the PCB substrate can be considered as different LC distributed parameters. The PCB conductors (of different areas and lengths) corresponding to the base of the microwave transistor Q201, along with the grounded copper layer on the other side of the PCB substrate, form a distributed capacitance-inductance network as a frequency-selective resonator. Positive feedback from the collector to the base is achieved through spatial electromagnetic coupling, thus forming the oscillator circuit. This oscillator uses the inherent thermal noise of the microwave transistor Q201 as the initial excitation source. When the thermal noise at the base of the microwave transistor Q201 increases slightly, the collector current increases accordingly. This positive feedback from the collector to the base through spatial coupling further increases the base current, thus forming positive feedback and generating high-frequency oscillation. The oscillation is limited to a specific frequency by the distributed parameters (i.e., LC parameters) of the conductors.
[0025] Furthermore, in this embodiment, the microwave transistor Q201 is configured to operate in the low-current nonlinear region, thereby allowing the external microwave signal received by the collector of the microwave transistor via the antenna ANT to be transmitted through the antenna. f 1 Through spatial coupling with the base, and with the oscillation signal of the base itself. f 0 The mixed inputs are fed into the circuit, thus forming a mixer circuit. Furthermore, a product operation is performed within the nonlinear amplification region of the microwave transistor's base. Consequently, the signal output from the microwave transistor's emitter contains not only the signal... f 1 and signals f 0 ,besides f 0 - f 1 as well as f 0 + f 1 These two signals. When there are no moving objects in the detection area, the received signal is reflected. f 1 and f 0 The frequencies are the same, at this time f 0 - f 1 The signal approaches zero, while f 0 + f 1 The signal can reach several GHz, which is an extremely high frequency. Therefore, capacitor C206 is used to filter it out. f 0 +f 1 The signal is such that when there is no moving object in the detection area, the microwave transceiver module has virtually no signal output. Additionally, when a moving object is present in the detection area, the received signal is reflected... f 1 The frequency of a signal due to the Doppler effect caused by a moving object is compared to the signal frequency. f 0 It will change to some extent, specifically affected by the direction and speed of the moving object. f 1 signal compared to signal f 0 The value will increase or decrease accordingly. At this time, the frequency shift signal output by the emitter of the microwave transistor Q201 contains a certain low-frequency difference frequency signal (only a few hertz to several hundred hertz). f 0 - f 1 At the same time, it also includes f 0 + f 1 This high-frequency signal, reaching several GHz, is also filtered out using capacitor C206, while retaining... f 0 - f 1 The corresponding effective low-frequency signal.
[0026] In addition, in this example, the microwave transceiver module uses a 3.3V power supply to provide a suitable operating voltage for the entire circuit, ensuring the normal operation of the microwave transistor Q201 and other components. See also Figure 1 In this example, capacitors C201, C202, and C204 are also used to filter the power supply and stabilize the power supply voltage, reducing the adverse effects of changes in the collector current of the microwave transistor Q201 on the power supply, thus achieving decoupling. They also contribute the equivalent AC potential of the 3.3V power supply to GND in the microwave circuit to the microwave oscillation circuit. In this example, capacitors C201 and C202 are used for low-to-medium frequency decoupling, and capacitor C203 is used for high-frequency decoupling, filtering out high-frequency noise on the power line. See also... Figure 1 Resistors R201, R202, R203, and R204 are used to adjust the bias current of the microwave transistor Q210. Specifically, resistor R201 acts as a current-limiting resistor, and R202 acts as a base bias resistor. Thus, R201 and R202 together form a base bias network, which determines the base voltage through voltage division, thereby setting the quiescent operating point of the microwave transistor. Additionally, in this embodiment, see... Figure 1By routing traces through a PCB bend at the collector of the microwave transistor, a choke inductor is formed to block high-frequency oscillation signals.
[0027] When an object moves within the detection area, there will be a phase deviation between the microwave reflected signal received by the PCB-onboard antenna ANT and the transmitted microwave signal. This phase deviation will induce a low-frequency frequency shift signal at the microwave transistor Q201, which will be output from the emitter of the microwave transistor Q201 and enter the subsequent signal conditioning module for signal processing.
[0028] In particular, considering that when an object moves within the detection area, the frequency of the reflected signal varies depending on the direction and velocity of the object's movement, and that the reflected signal frequency changes differently at multiple angles, therefore, the reflected signal... f 1 It is not a single frequency component, but a complex signal group containing multiple components of different frequencies. Therefore, the oscillating signal f 0 With reflected signal f 1 After mixing, the difference frequency signal output from the emitter of microwave transistor Q201 f 0 - f 1 Similarly, it manifests as a low-frequency composite signal with a wide frequency band, ranging from a few hertz to hundreds of kilohertz. To extract the effective low-frequency components necessary for the target object's motion from this composite signal, in this embodiment, capacitor C206 is used to filter out high-frequency signals. However, this capacitor exhibits extremely low capacitive reactance for GHz-level signals, effectively filtering and absorbing high-frequency signals. For difference frequency signals below hundreds of kilohertz, the capacitor exhibits high capacitive reactance, allowing low-frequency signals to enter subsequent processing circuits. However, in practical applications, the effective energy representing human micro-movements is mainly concentrated in the frequency range of a few hertz to tens of hertz. Therefore, in this example, a low-pass filter unit is set downstream of the microwave transceiver module to filter the signal. Specifically, in this embodiment, see... Figure 1 The low-pass filter unit is a first-order RC low-pass filter circuit composed of resistor R205 and capacitor C207, used to filter out unused higher frequencies in the frequency-shifted signal output by the microwave transceiver module. In this example, the corner frequency of the first-order RC low-pass filter circuit composed of resistor R205 and capacitor C207 is... f =1 / (2 πRC )=15.9KHz, and then through Figure 1The low-pass filter unit shown filters out high-frequency signals above 15.9 kHz. In some other embodiments, the cutoff frequency parameter of the RC low-pass filter circuit (by adjusting the values of resistor R205 and / or capacitor C207) is adjusted to be lowered as needed to more accurately match the target signal frequency band and optimize the signal-to-noise ratio.
[0029] Furthermore, considering the limitations of low-power design in radar response systems suitable for smart furniture, the microwave radar transmit power of the microwave transceiver module is relatively low, resulting in a relatively weak difference frequency signal at its induction output. To facilitate subsequent signal detection and processing, the signal needs to be amplified from the microvolt level to the volt level, for example, to the full-scale input range of an ADC with a peak-to-peak value of approximately 3.3V. Therefore, in this example, the amplification factor reaches a maximum of tens of thousands of times. Through long-term practical research, the inventors discovered that if such a high gain is achieved using a single-stage amplifier, the amplifier circuit is highly susceptible to instability due to noise, power supply fluctuations, or component parameter drift. Moreover, bandwidth and phase margin are difficult to guarantee, and the overall anti-interference capability will significantly decrease. Therefore, in this embodiment, a two-stage amplification structure consisting of a pre-amplification unit and a gain-adjustable amplification unit arranged sequentially is adopted. This ensures both high gain and system performance. By rationally allocating the gain, the stability risks associated with single-stage amplification are effectively avoided, improving the overall signal-to-noise ratio and reliability of the system.
[0030] Specifically, in this embodiment, a pre-amplification unit is first used as the first-stage amplification structure to amplify the initial weak signal (tens to hundreds of microvolts) to the tens of millivolt level. See also Figure 1 In this embodiment, the pre-amplification unit includes a signal pre-amplification circuit composed of a first operational amplifier U301A. Resistors R301 and R302, and capacitor C301, are used to provide a bias voltage to the non-inverting input terminal of the first operational amplifier U301A. Considering that the maximum undistorted AC output amplitude is limited by the minimum of the difference between the quiescent operating point voltage and the positive power supply voltage, and the difference between the quiescent operating point voltage and the negative power supply voltage, the larger this smaller value, the larger the dynamic range of the input signal that the circuit can process before distortion. In this embodiment, by setting the values of resistors R301, R302, and capacitor C301, the quiescent output voltage of the first operational amplifier U301A is set to the midpoint value of the power supply voltage, thereby maximizing its linear dynamic range.
[0031] Additionally, see Figure 1Resistor R303 is electrically connected to the inverting input terminal of the first operational amplifier U301A for signal input. Resistor R304 is located in the feedback path between the inverting input and output terminals of the first operational amplifier U301A. The ratio of resistors R304 to R303 serves as the inverting amplification factor. In this example, the voltage amplification factor of the first operational amplifier U301A is 2M / 20K, which is 100 times. Furthermore, the inventors found through long-term practical research that signals above tens of hertz are not very effective for detecting human activity characteristics. Considering the speed requirements of the ADC detection by the microcontroller in the subsequent control and judgment module, [further details are needed]. Figure 1 By connecting capacitor C303 and resistor R304 in parallel, a first-order low-pass filter circuit is formed, and in this example, its cutoff frequency is... f =1 / (2 πRC The frequency is set to 8Hz, meaning signals below this cutoff frequency are amplified, while signals above it are filtered out. Thus, the filter circuit in the feedback channel of the first operational amplifier, consisting of capacitor C303 and resistor R304 connected in parallel, filters out frequencies above tens of hertz that are less useful for detecting human activity characteristics, while retaining low-frequency signals that have relatively low requirements for the microcontroller's ADC detection speed. This facilitates detection and recognition by the subsequent control and judgment module.
[0032] In this example, the pre-amplification unit is used to amplify the low-frequency AC signal output from the emitter of the microwave transistor Q201. However, considering that the static operating point of the emitter of the microwave transistor Q201 determines that there is a fixed DC bias voltage at its output, if this DC bias voltage is input to the first operational amplifier U301A along with the AC signal, it will directly affect the operating point setting of the first operational amplifier U301A, potentially causing its output saturation or limited dynamic range. Therefore, see... Figure 1 In this example, a DC blocking capacitor C302 is set between the microwave transceiver module and the pre-amplification unit. The capacitor can only pass AC signals for isolation, that is, it presents a high impedance to DC signals to block DC components. This isolates the DC bias voltage of the previous stage, and only the low-frequency AC signal needs to be amplified in the pre-amplification unit, ensuring that the pre-amplification unit and the previous microwave transceiver module do not interfere with each other.
[0033] The signal, after being amplified and filtered by the pre-amplification unit, is input to the gain-adjustable amplification unit, which serves as the second-stage amplification structure, for further amplification. In this embodiment, see... Figure 1The gain-adjustable amplification unit employs a non-inverting amplification structure. Specifically, the signal amplified by the pre-amplification unit is input to the non-inverting input of the second operational amplifier U301B. In practical applications, the distance and activity intensity of the target within the detection area vary significantly, leading to substantial differences in the intensity of the reflected signal. The inventors discovered in practice that traditional fixed-gain operational amplifiers cause output signal saturation and distortion at close range or during periods of strong activity, making it difficult to effectively detect distant or weak activity. Therefore, in this embodiment, the second operational amplifier is configured as a gain-adjustable operational amplifier, allowing it to dynamically adjust the amplification factor based on the real-time signal strength. This ensures that weak signals are fully amplified while strong signals remain undistorted, effectively covering the entire detection scenario.
[0034] Specifically, in this embodiment, see Figure 1 A gain-regulating MOSFET Q301 is placed at the inverting input terminal of the second operational amplifier U301B, and the drain of the gain-regulating MOSFET Q301 is electrically connected to the inverting input terminal of the second operational amplifier U301B. In the non-inverting amplifier circuit, the closed-loop voltage gain, i.e., the amplification factor, of the second operational amplifier U301B is proportional to the feedback resistor R306 and the equivalent resistance R of the gain-regulating MOSFET Q301. d The ratio of the gain control MOSFET Q301 to the gate voltage (G) is used to achieve gain control of the equivalent resistance R between the drain and source of Q301. d The adjustment achieves the purpose of adjusting the gain of the gain-controlled MOSFET Q301 to different amplification factors. In this embodiment, based on the variable resistance operating region characteristics of the gain-controlled MOSFET Q301, the MOSFET selected in this example has the characteristics of low transconductance and a wide variable resistance de-region range. Therefore, when the gate voltage of the gain-controlled MOSFET Q301 varies within a large range, the gain-controlled MOSFET Q301 can smoothly transition from a fully off high-resistance state to a deeply on low-resistance state. Therefore, by adjusting the voltage applied to the gate of the gain-controlled MOSFET Q301, the equivalent resistance R between its drain and source can be continuously and linearly changed. d This achieves the effect of adjusting the gain of the gain-controlled MOSFET Q301.
[0035] To adjust the gate voltage of the gain-regulating MOSFET Q301 and thus regulate the gain of the second operational amplifier, this embodiment includes a gain control unit. Specifically, in this example, the control module uses a microcontroller. The microcontroller outputs a PWM control signal through its output port. This signal is smoothed into a stable DC voltage by a second-order low-pass filter circuit composed of resistors R307 and R308, and capacitors C305 and C306Z. This voltage serves as the control voltage for the gate of the gain-regulating MOSFET Q301. In this example, the PWM duty cycle can be adjusted within the range of 0% to 100%, allowing the voltage applied to the MOSFET gate to vary within the range of 0 to 3.3V. Consequently, the equivalent resistance value R of the gain-regulating MOSFET Q301 is adjusted. d It can achieve a range from infinity, which is completely off, to zero ohms, which is close to being fully on. Therefore, by changing the duty cycle of the PWM control signal, the voltage gain of the gain-adjustable amplifier unit can be continuously and smoothly adjusted, thus realizing the gain-adjustable amplification function of the second operational amplifier.
[0036] However, through long-term practical research, the inventors have also discovered that if the PWM control signal is directly output from the control judgment module for gain adjustment of the gain control MOSFET Q301, on the one hand, different batches of MOSFETs have different threshold voltages, transconductance, and other parameters. Under the same control voltage, their equivalent on-resistance values differ, resulting in inconsistent product performance in final industrial production applications. On the other hand, the conduction characteristics of the MOSFET vary significantly with ambient temperature, and its equivalent on-resistance drifts with temperature changes, causing the gain value of the same product to be unstable in different seasons or operating temperature environments. This leads to uncontrolled changes in the detection sensitivity of the radar sensing system, resulting in poor product reliability. Furthermore, the relationship between the PWM control voltage and the equivalent on-resistance of the MOSFET is not ideally linear, especially near the deep linear region and the cutoff region, making the gain adjustment coarse and unable to achieve precise and linear gain control. Therefore, in this embodiment, see... Figure 1 Set a pull-up resistor R305 and connect it to the drain of the gain-regulating MOSFET Q301 to generate a DC potential at this connection node. See [link to documentation]. Figure 1 A feedback unit is set up, and a feedback signal line is led out from this node to the input port of the control judgment module. In this example, the potential signal at this DC potential (labeled as ADC2) is guided to the analog-to-digital converter input pin of the judgment control module for sampling through the feedback signal line. Thus, the control judgment module can read the voltage value of the corresponding ADC2 and combine it with the known circuit parameters to calculate in real time the current equivalent resistance R of the gain control MOSFET Q301. dThis allows the system to determine whether the second operational amplifier U301B is within the set gain range. When the actual operating gain of the second operational amplifier U301B fails to meet the set gain requirement, the gain control unit of the control judgment module adjusts the duty cycle of its output PWM signal until the equivalent resistance of the gain-regulating MOSFET Q301 meets the corresponding set gain requirement. Thus, through feedback adjustment, the duty cycle of the PWM control signal is dynamically adjusted, thereby precisely controlling the equivalent resistance of the gain-regulating MOSFET Q301, keeping it constant at the theoretical value required to achieve the target gain. This effectively solves the problems of device discreteness, temperature drift, and control accuracy and nonlinearity. The radar sensing system directly uses the final physical quantity (MOSFET equivalent resistance or operational amplifier gain) as the control target, eliminating all intermediate errors through closed-loop feedback, ensuring a high degree of consistency between the set gain value and the actual gain value, and ensuring adjustment accuracy and reliability. Furthermore, because the closed-loop system can adaptively compensate for the parameter discreteness of different MOSFETs, complex manual calibration for each product is eliminated in actual production, reducing process and labor costs, and greatly improving mass production efficiency and product consistency. In addition, the closed-loop calibration of the system can also offset the impact of temperature changes on the characteristics of the MOSFET in real time, so that the circuit gain remains constant within the operating temperature range, effectively avoiding temperature drift problems and improving the environmental adaptability and long-term reliability of the final mass-produced products.
[0037] Specifically, in this embodiment, the signal judgment unit of the control judgment module, i.e., through the ADC module inside the microcontroller, periodically samples the drain voltage of the gain-regulating MOS transistor Q301 via a feedback signal line. The node connected to this feedback signal line consists of a pull-up resistor R305 and the equivalent resistance R of the gain-regulating MOS transistor Q301. d This constructs a voltage divider circuit for the power supply voltage. By measuring the different voltage division values corresponding to the state of the external circuit, the equivalent resistance R can be calculated. d The value is used by the gain control unit to calculate the real-time equivalent resistance R. d The numerical value is compared with the preset equivalent resistance corresponding to the target gain, and the real-time equivalent resistance R is used. d When the value deviates from the preset equivalent resistance value, the duty cycle of the PWM control signal is adjusted proportionally until the real-time equivalent resistance R is reached. d The numerical value dynamically and gradually approaches and eventually stabilizes within an allowable error range near the preset equivalent resistance value.
[0038] See Figure 1The frequency shift signal, after being processed by the gain-adjustable amplification unit, is input to the signal judgment unit of the control judgment module for judgment processing. In this example, the signal judgment unit samples the input frequency shift signal at a fixed frequency based on its internal ADC module, converts it into a discrete digital sequence, and then determines the activity of the target object according to the activity judgment threshold corresponding to the user-set sensitivity parameter.
[0039] Furthermore, in this embodiment, the control judgment module also includes a wireless communication unit. In this example, the wireless communication unit uses low-cost Bluetooth communication to establish communication between the radar sensing system and the mobile control terminal, so as to receive sensitivity control commands sent by the mobile control terminal, or send the sensing status of the radar sensing system to the mobile control terminal. See also Figure 1 In this example, a voltage regulator unit is also provided. The 5V power input is output as 3.3V after passing through the voltage regulator chip U101 in the voltage regulator unit, which is used to provide a stable voltage to the microwave transceiver module, signal conditioning module and control judgment module.
[0040] This example also discloses a sensing processing method for a radar sensing system, which is implemented based on the aforementioned radar sensing system and specifically includes the following steps: (1) The microwave transceiver module transmits microwaves to the detection area and receives microwave reflection signals, and outputs corresponding sensing signals; the sensing signals are filtered and amplified based on the signal conditioning module.
[0041] To detect moving targets within the detection area, a microwave transceiver module first continuously transmits microwave signals of a specific frequency into the area under test and receives echoes reflected from the environment and the target. The presence of a moving target causes a shift between the echo frequency and the transmission frequency. After receiving the reflected signal, the microwave transceiver module mixes it and outputs a low-frequency analog induction signal containing target motion information. This induction signal is then input to a signal conditioning module, where it is filtered to remove noise and high-frequency interference, and amplified to increase the signal amplitude, making it suitable for subsequent analog-to-digital conversion and other signal processing.
[0042] (2) The gain control unit outputs a PWM signal to adjust the gain of the gain-adjustable amplifier unit. At the same time, the feedback unit monitors the gain status of the gain-adjustable amplifier unit and adjusts the duty cycle of the PWM signal accordingly until the gain-adjustable amplifier unit converges to the target gain.
[0043] When the sensed signal is amplified in the gain-adjustable amplification unit of the signal conditioning module, the gain control unit of the control judgment module outputs a PWM signal. This signal is converted into a DC voltage after being filtered by a second-order low-pass filter and applied to the gate of the gain-regulating MOSFET in the gain-adjustable amplification unit to control the equivalent resistance of the gain-regulating MOSFET, thereby adjusting the voltage gain of the gain control unit. Simultaneously, the feedback unit monitors the voltage of the gain-related circuit nodes in real time through the feedback signal line (ADC2 signal channel) and calculates the equivalent resistance of the current gain-regulating MOSFET based on this node voltage to determine the actual gain of the gain-adjustable amplification unit. Furthermore, the gain control unit of the control judgment module compares the actual equivalent resistance with the target equivalent resistance value corresponding to the preset target gain. If the actual gain is too low, the duty cycle of the PWM is automatically increased proportionally to improve the gain. If the actual gain is too high, the duty cycle is automatically decreased proportionally to reduce the gain. Through this closed-loop control, the actual equivalent resistance value (i.e., the actual gain) converges and stabilizes at the target equivalent resistance value (i.e., the target gain), thereby achieving compensation for device tolerances and temperature drift, ensuring the consistency and reliability of signal amplification in the finished equipment.
[0044] (3) The signal judgment unit performs analog-to-digital conversion on the conditioned induction signal and samples it accordingly to obtain a discrete sampling sequence.
[0045] The frequency shift-varying analog signal (ADC1) processed by the signal conditioning module is sent to the control and judgment module. The signal judgment unit controls its internal ADC module to sample the input analog signal at a fixed frequency, converting it into a series of discrete digital sample values to form a sampling sequence.
[0046] (4) Calculate the DC component of the sampling sequence within the initial predetermined time window; after calculating the cumulative sum of the absolute values of the differences between each sampling point in the sampling sequence and the DC component within the sensing time window, obtain the activity index value characterizing the intensity of the target activity.
[0047] After the sampling sequence is obtained through sampling processing by the signal judgment unit, activity features need to be extracted from the sampling sequence. Through long-term practice, the inventors discovered that traditional radar sensing carries a risk of misjudgment; that is, the sensing system may determine the presence of a target when there is no moving object in the detection area. The inventors found that the traditional Doppler signal detection method judges the sensing signal based on the difference frequency signal intensity value. It determines the presence of a valid sensor when the signal exceeds a certain value. Therefore, when a strong electromagnetic pulse is present, the system may misjudge the presence of a moving target in the detection area. To solve this misjudgment problem, the inventors attempted to adjust the judgment threshold to eliminate misjudgments. However, in practice, they found that increasing the judgment threshold reduces the sensitivity of the radar sensing system, leading to unreliable identification. Conversely, in applications requiring high sensitivity, lowering the judgment threshold increases the risk of misjudgment.
[0048] Therefore, in this embodiment, an initial predetermined time window lasting several seconds is first selected. The arithmetic mean of all sampled values within this window is calculated as the DC component of the sampling sequence, representing the background signal level under static conditions (i.e., no activity). Then, the deviation between each sampling point and the DC component in the sampling sequence is calculated, and its absolute value is taken to eliminate the influence of the fluctuation direction. The absolute value of the deviation reflects the amplitude of the fluctuation. Furthermore, within a sensing time window shorter than the initial predetermined time window, the sequence of absolute deviation values corresponding to each sampling point is summed to obtain the activity index value. This activity index value, by accumulating the total energy of the signal deviating from the static reference within the sensing time window, can effectively characterize the intensity and duration of the target activity.
[0049] In other embodiments, in order to improve the anti-interference capability of the radar sensing system, and considering that the duration of the interfering electromagnetic pulse is short while the signals generated by real human activities usually have a longer duration, this example increases the length of the sensing time window to improve the radar sensing system's ability to suppress short-time pulse interference. This allows the energy of the short-time interference pulse to be "diluted" in a longer accumulation window, thereby improving the signal-to-noise ratio at the processing method level.
[0050] (5) Compare the activity index value with the preset judgment threshold. If the activity index value exceeds the preset judgment threshold, it is determined that there is a valid target activity in the detection area.
[0051] After obtaining the activity index value, it is compared with the preset judgment threshold in real time. When the activity index value is greater than the preset judgment threshold, it is determined that there is a valid target activity in the detection area, and the control system of the smart furniture turns on the lights accordingly; when the activity index value is less than the preset judgment threshold, it is determined that there is no valid activity in the detection area.
[0052] In this example, the preset judgment threshold is dynamically adjusted based on the sensitivity setting command received by the wireless communication unit from the user terminal. Furthermore, there is an inverse relationship between the sensitivity level and the judgment threshold. A higher sensitivity setting corresponds to a lower judgment threshold, allowing even weaker signal fluctuations to trigger target activity detection, thus enabling the detection of more minute activities. Conversely, a lower sensitivity setting corresponds to a higher judgment threshold, requiring only stronger activity signals to trigger the detection. This effectively suppresses the risk of false alarms and enhances the anti-interference capability of the radar sensing system.
[0053] Although some preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.
[0054] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this application and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A radar sensing system suitable for smart furniture, characterized in that, The system includes a microwave transceiver module for transmitting and receiving microwave signals and correspondingly outputting frequency-shifted signals; a signal conditioning module electrically connected downstream of the signal output terminal of the microwave transceiver module for filtering and amplifying the frequency-shifted signals and including at least one stage of gain-adjustable amplification unit; and a control judgment module electrically connected to the signal conditioning module. The control judgment module includes a gain control unit for generating PWM control signals to dynamically adjust the gain of the gain-adjustable amplification unit; a feedback unit for acquiring the operating parameters of the gain-adjustable amplification unit to achieve closed-loop control of the gain of the gain-adjustable amplification unit; a signal judgment unit for receiving the conditioned frequency-shifted signals and judging the target activity state; and a wireless communication unit for wirelessly communicating with an external terminal to receive configuration commands and / or sensing status.
2. The radar sensing system according to claim 1, characterized in that, It also includes a voltage regulator unit for providing stable voltage to the microwave transceiver module, signal conditioning module, and control judgment module.
3. The radar sensing system according to claim 1, characterized in that, The microwave transceiver module includes an oscillator and mixer circuit based on a microwave transistor.
4. The radar sensing system according to claim 1, characterized in that, The signal conditioning module includes a low-pass filter unit, a pre-amplifier unit, and the gain-adjustable amplification unit, which are electrically connected sequentially from upstream to downstream. The pre-amplifier unit includes a first operational amplifier whose inverting input terminal is electrically connected to the output terminal of the low-pass filter unit through a DC blocking capacitor and whose static output voltage is the midpoint voltage, and a first-order low-pass filter circuit disposed in the feedback channel of the first operational amplifier for filtering the frequency shift signal.
5. The radar sensing system according to claim 1 or 4, characterized in that, The gain-adjustable amplification unit includes a second operational amplifier and a gain-regulating MOS transistor whose drain is electrically connected to the inverting input terminal of the second operational amplifier; the gate of the gain-regulating MOS transistor is electrically connected to the PWM signal output port of the gain control unit.
6. The radar sensing system according to claim 1, characterized in that, The PWM signal output by the gain control unit is filtered by a second-order low-pass filter and then used to adjust the gain-adjustable amplifier unit accordingly.
7. A sensing processing method for a radar sensing system, characterized in that, Implemented based on the radar sensing system of claim 1, it includes the following steps: (1) The microwave transceiver module transmits microwaves to the detection area and receives microwave reflected signals, and outputs corresponding sensing signals; the sensing signals are filtered and amplified based on the signal conditioning module. (2) The gain control unit outputs a PWM signal to adjust the gain of the gain-adjustable amplifier unit, and at the same time monitors the gain status of the gain-adjustable amplifier unit through the feedback unit and adjusts the duty cycle of the PWM signal accordingly until the gain-adjustable amplifier unit converges to the target gain. (3) The signal judgment unit performs analog-to-digital conversion on the conditioned induction signal and samples it accordingly to obtain a discrete sampling sequence; (4) Calculate the DC component of the sampling sequence within the initial predetermined time window; after calculating the cumulative sum of the absolute values of the differences between each sampling point in the sampling sequence and the DC component within the sensing time window, obtain the activity index value characterizing the intensity of the target activity; (5) Compare the activity index value with a preset judgment threshold, and determine that there is a valid target activity in the detection area when the activity index value exceeds the preset judgment threshold.
8. The sensing processing method according to claim 6, characterized in that, In step (4), the anti-interference capability of the radar sensing system is improved by increasing the duration of the sensing time window.
9. The sensing processing method according to claim 6, characterized in that, In step (5), the judgment threshold is dynamically adjusted according to the sensitivity setting instruction received by the wireless communication unit, and the judgment threshold is inversely proportional to the sensitivity.