Electromagnetic wave musical sound sensing control system

Abstract

An electromagnetic wave musical sound sensing control system comprises an electromagnetic wave transceiver, a microcontroller, a band-pass filter, a down-conversion module, an audio power amplifier and a loudspeaker. The system is based on the FMCW radar principle, and the distance between the hand and the radar is linearly mapped into an intermediate frequency signal; carrying out splicing processing on intermediate frequency signals of data truncation between Chirp through a missing segment backfilling algorithm based on template matching, and eliminating time domain discontinuity; after 20kHz band-pass filtering, the intermediate frequency is down-converted to a range which can be perceived by human ears of 20Hz-20kHz by using an analog multiplier and a low-pass filter, and a loudspeaker is driven to produce sound; pitch changes in real time along with the gesture distance, and non-contact audio interaction is achieved; the system has the advantages of real-time response, continuous and natural tone and simple structure, and is suitable for scenes of music interaction, education, rehabilitation and the like.

Description

Technical Field

[0001] This invention relates to the field of audio frequency control technology, and in particular to an electromagnetic wave music sensing and control system. Background Technology

[0002] Audio frequency control is a core function in modern audio technology, widely used in electronic musical instruments, voice interaction, human-computer interfaces, assistive devices, rehabilitation training, and creative arts. The essence of frequency control is to dynamically adjust the pitch (i.e., frequency) of the audio output based on changes in the user's input signal, achieving interactive and controllable sound output. With the development of human-computer interaction and artificial intelligence, non-contact control has gradually become a research hotspot. Common forms include gesture recognition (based on cameras, TOF (Time of Flight) sensors, millimeter-wave radar, etc.) which can detect hand movements for controlling volume, play / sleep, etc. Although some technologies (such as MIDI (Musical Instrument Digital Interface) control and camera gesture recognition) have been applied to audio control, they generally suffer from problems such as response latency, poor recognition robustness, and high user learning costs.

[0003] Patent application CN202210945573.6 discloses a method for realizing the hearing of ultrasound. The core of this method is based on frequency modulation. It collects ultrasound signals, converts the sound waves into electrical signals for processing, and then converts the electrical signals back into sound waves for human hearing. Initially, the ultrasound signals are collected through a high-frequency oscillation circuit composed of piezoelectric materials, power supply, resistors, and inductors, which directly collects the sound wave signals and inputs them into an operational amplifier. The sound wave frequency is obtained through a frequency analyzer or magnetic tape recorder, and Fourier expansion is performed. The modulation frequency is calculated based on the first harmonic frequency using the sum-product formula, and the modulation signal is output to the circuit through a signal generator. The two signals first enter an active nonlinear multiplier, which modulates and mixes the uncorrelated signals through shifting and addition. The mixed signal then passes through a low-pass filter with a cutoff frequency of 20kHz, and the filtered signal is amplified by a power amplifier, which can directly drive headphones to produce sound, allowing people to hear ultrasound. Its disadvantages are: the ultrasonic method requires first collecting ultrasonic waves using piezoelectric materials, then performing offline Fourier expansion and modulation calculations using a frequency analyzer or magnetic tape recorder, and finally driving the signal generator, resulting in a complex process and significant time delay. The ultrasonic method relies on multiple independent modules such as piezoelectric transducers, high-frequency oscillation circuits, frequency analyzers, and magnetic tape recorders, resulting in numerous components, complex debugging, large overall size, and high production and maintenance costs. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, the present invention aims to provide an electromagnetic wave music sensing and control system that uses a non-contact, precise and controllable method to dynamically control the audio output frequency based on the movement of the human hand. When the hand movement causes a corresponding change in the intermediate frequency signal output by the electromagnetic transceiver, the system accurately maps this change to an audio frequency within the range of human hearing perception, thereby obtaining an intuitive and smooth interactive experience and achieving the frequency control effect of human-computer interaction.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An electromagnetic wave music sensing and control system, comprising: An electromagnetic transceiver is used to transmit frequency-modulated continuous wave signals and receive echo signals reflected from the hand. After mixing, it outputs an intermediate frequency signal. The frequency of the intermediate frequency signal is proportional to the distance between the hand and the radar. The microcontroller is used to perform analog-to-digital conversion sampling of the intermediate frequency signal and to perform template matching-based missing segment backfilling processing to convert the intermediate frequency signal into a continuous time-domain signal, which is then output as an analog signal via the microcontroller's DAC. The bandpass filter module is connected to the output of the microcontroller and is used to filter out signals outside the frequency band and smooth the output. Its passband bandwidth is 20kHz. The lower cutoff frequency is determined based on the closest value of the hand distance radar, and the upper cutoff frequency is determined based on the farthest value of the hand distance radar. The downconversion module includes an analog multiplier and a low-pass filter. The analog multiplier multiplies the intermediate frequency signal after bandpass filtering with the reference local oscillator signal and outputs a mixed signal containing sum and difference frequency components. The low-pass filter has a cutoff frequency of 20kHz and is used to filter out the sum frequency component and retain the difference frequency audio signal that falls within the range of human hearing. An audio amplifier module is used to amplify the difference frequency audio signal; A loudspeaker is used to play amplified audio signals, and its pitch responds in real time to changes in the distance of a hand gesture.

[0006] The microcontroller performs template-matching-based missing segment backfilling to eliminate the time-domain discontinuity of the intermediate frequency signal caused by the idle time between chirps of continuous wave signals, thus preventing audio signal breaks, pops, or noise after down-conversion; the specific process includes: After the electromagnetic transceiver detects a target ahead, it generates a periodic signal, the frequency of which corresponds one-to-one with the distance to the target. Because the radar transmits at intervals, there will be a data gap in the middle of the periodic signal generated by the radar. The missing data is filled in using a template matching-based missing segment backfilling algorithm, as detailed below: 1) During the chirp duration of each continuous wave signal, the intermediate frequency signal is sampled by the ADC to obtain intermediate frequency data segments; 2) Select a segment of intermediate frequency data at the end of the current continuous wave signal Chirp, determine whether this segment of data is trending upward or downward, and record the value of the interruption point as a reference value; 3) Based on the filtering criteria of "consistent trend + similar reference value amplitude", search for matching data segments after the breakpoint starting from the current Chirp data start position; 4) Then fill in the missing data with the matching data to form a continuous periodic signal over a period of time.

[0007] The range that the human ear can perceive is a signal frequency of 20Hz-20kHz.

[0008] The method for determining whether the data at the end of the Chirp is in an upward or downward trend is as follows: Select the first n data points of the data at the end of the Chirp, and use a voting-based trend indicator to see if the number of "positive / non-negative" values ​​in the adjacent differences of the first n data points exceeds the number of "negative" values. If the number of positive / non-negative values ​​is greater, it is judged as an upward trend; otherwise, it is judged as a downward trend.

[0009] The reference local oscillator signal is a sinusoidal signal with a fixed frequency, and its frequency is configured so that the difference frequency audio signal falls within the range of human hearing perception of 20Hz to 20kHz.

[0010] The electromagnetic transceiver uses a frequency modulated continuous wave (FMCW) radar, and the frequency modulation slope of the transmitted signal is adjustable.

[0011] The electromagnetic wave sound sensing and control system is used to construct non-contact audio interactive devices, including: audio art installations, children's music education equipment, upper limb motor rehabilitation training auxiliary equipment, or intelligent speaker gesture control systems; wherein, the user changes the distance between their hand and the radar by moving their hand in space, and adjusts the pitch of the output audio in real time to achieve intuitive and smooth sound interaction feedback.

[0012] A method for operating an electromagnetic wave music sound sensing and control system specifically includes the following steps: Step 1: Map the distance between the hand and the radar antenna into an intermediate frequency signal. An FMCW signal with a frequency that varies linearly with time is transmitted via an electromagnetic transceiver. This signal is reflected upon encountering a hand target and captured by a receiving antenna. Due to the time delay τ between the transmitted and echo signals, which is proportional to the target distance d, and because the transmitted signal is a linear frequency modulated wave, the intermediate frequency (IF) signal output after mixing has a fixed frequency, the value of which is determined by the following formula: Where S is the frequency modulation slope and c is the speed of light; thus, the change in the distance between the hand and the radar is linearly mapped to the change in the intermediate frequency. Step 2: Perform template matching-based missing segment backfilling on the intermediate frequency signal. The FMCW radar has idle time between adjacent continuous wave signal chirps, causing the output intermediate frequency signal to be discontinuous in the time domain, resulting in audio breaks or noise; to address this, the microcontroller executes the following sub-steps: 1) During the chirp duration of each continuous wave signal, the intermediate frequency signal is sampled by the ADC to obtain intermediate frequency data segments; 2) Select a segment of data at the end of the current continuous wave signal Chirp, determine whether this segment of data is trending upward or downward, and record the value of the interruption point as a reference value; 3) Based on the filtering criteria of "consistent trend + similar reference value amplitude", search for matching data segments after the breakpoint starting from the current Chirp data start position; 4) Then fill in the missing data with the matching data to form a continuous periodic signal over a period of time; Step 3: Perform bandpass filtering on the intermediate frequency signal after it becomes continuous in the time domain. The intermediate frequency signal processed in step 2 is input into the bandpass filter module. The passband bandwidth of the bandpass filter is 20kHz. Its lower cutoff frequency is the frequency output by the radar when the hand is closest to the radar, and its upper cutoff frequency is the frequency output by the radar when the hand is furthest from the radar. It is used to filter out high-frequency noise outside the band and retain the intermediate frequency signal in the effective ranging frequency band. Step 4: Down-convert the intermediate frequency signal to an audio frequency band that the human ear can perceive. The intermediate frequency signal after bandpass filtering is mixed with a low-frequency local oscillator signal of a fixed frequency in an analog multiplier to generate a mixed signal containing the sum frequency and the difference frequency. The high-frequency sum frequency component is then filtered out by a low-pass filter with a cutoff frequency of 20 kHz, leaving only the difference frequency component. The frequency of this difference frequency signal falls within the range of human hearing of 20 Hz–20 kHz and is used as the audio signal output. Step 5: Amplify the audio signal and play it. The difference frequency audio signal is input to the audio power amplifier module for power amplification to provide sufficient energy to drive the speaker; the speaker converts the amplified electrical signal into sound waves to form real-time audio feedback; the user can dynamically adjust the output pitch by changing the distance between their hand and the radar, thus achieving non-contact music control.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A multi-level mapping mechanism from distance to intermediate frequency (IF) to audio: Steps 1-2 convert distance changes to IF changes (using the principle of frequency-modulated radar and a missing segment backfilling algorithm based on template matching); Steps 3-4 convert IF changes to audio changes (using a down-conversion circuit); thus achieving the goal of controlling pitch with the user's hand movements. This multi-level mapping mechanism has high real-time performance and high physical consistency.

[0014] 2. Template matching-based missing segment backfilling algorithm: Step 2 uses template matching-based missing segment backfilling and data filling algorithms to achieve temporal continuity of intermediate frequency signals between radar continuous wave signals and chirps, so that the audio output after downconversion is continuous, natural and without jumps. This solution has advantages such as high real-time performance, strong physical consistency, natural audio output and low hardware cost, and is a key technology to ensure high-quality interaction of "hand movement - audio feedback".

[0015] 3. Mapping method for a specific distance range (e.g., 0.4 meters) to a set intermediate frequency bandwidth (e.g., 20kHz): Step 1 of this invention utilizes frequency modulation slope control to map the hand movement range (e.g., the 0.4-meter range from 1 meter to 1.4 meters) to a continuous, linearly adjustable intermediate frequency range (e.g., 50kHz to 70kHz), ensuring that the output audio has sufficient dynamic range and audible resolution. This mapping method can precisely adjust the system's sensitivity and response resolution.

[0016] 4. Application scenario design combining non-contact control and audio feedback interaction: Steps 1-5 of this invention can be used to build a gesture-based audio interaction system, such as audio art installations, children's educational products, rehabilitation assistive devices, and intelligent speaker control platforms. Its core feature is that the pitch can be directly controlled through the spatial movement of the hand, thereby obtaining an intuitive and smooth interactive experience.

[0017] 5. Adjustable design of intermediate frequency range and down-conversion parameters: Step 1 of this invention supports the flexible setting of the mapping between the top intermediate frequency and audio by adjusting parameters such as the radar frequency modulation slope, the filter bandwidth and local oscillator frequency in steps 3-4 of this invention, so as to adapt to the frequency control requirements of different scenarios (such as broadband sound effects vs. narrowband prompt tones).

[0018] In summary, compared to traditional methods, this invention addresses the problem in FMCW radar where idle time exists between each chirp, causing discontinuity in the intermediate frequency (IF) signal in the time domain. This discontinuity manifests as audio breaks, pops, or noise after down-conversion. At the end of each chirp, this invention uses data acquired by an ADC to extract the data trend. Before the next chirp begins, a segment matching the trend is selected from the previous data to fill the gaps. This achieves a natural continuation of the IF signal in the time domain, splicing it into a continuous IF signal sequence. This invention achieves real-time, non-contact distance-frequency mapping, resulting in faster and more intuitive response. The radar directly transmits and receives swept-frequency signals. The IF frequency is linearly proportional to the distance between the hand and the radar. A microprocessor performs template matching-based missing segment backfilling to achieve temporal continuity of the IF signal. The DAC output is an analog signal that is bandpass filtered and then frequency-converted to the audible range before being sent to the speaker. The entire process from "manual input to sound" is completed within milliseconds, requiring no Fourier analysis or additional equipment, significantly improving real-time performance. High hardware integration significantly reduces cost and size. The core requires only one electromagnetic wave transceiver system, microprocessor, multiplier, filter circuit, and power amplifier circuit, eliminating the need for a piezoelectric receiver and high-frequency Fourier analyzer. Components are universal, mass production reduces costs, and overall size and power consumption are easier to control. The audio adjustable range is wider and more continuous. The system is more robust and has stronger anti-interference capabilities. Expandable mapping and interactive functions broaden its applicability. For example, by simply adjusting the radar modulation slope S, bandpass filter, and down-conversion local oscillator frequency, the audio range corresponding to different hand distances can be arbitrarily defined. Attached Figure Description

[0019] Figure 1 This is a block diagram of the audio generation system of the present invention.

[0020] Figure 2 This is a schematic diagram of the intermediate frequency signal output of the actual electromagnetic transceiver of the present invention.

[0021] Figure 3 This invention extracts the data change trend at the end of the Chirp.

[0022] Figure 4 To find matching data fragments after the breakpoint in this invention.

[0023] Figure 5 This diagram shows how the matching data of the present invention fills in the interrupted area. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of the present invention.

[0025] An electromagnetic wave music sensing and control system, comprising: 1. Electromagnetic wave transceiver Physical connection: The transmitter is connected to the RF local oscillator and outputs the FMCW signal to the transmitting antenna; the receiver obtains the hand reflection echo through the receiving antenna, mixes it with the local oscillator signal in the mixer, and outputs the intermediate frequency signal.

[0026] Functional association: Mapping changes in hand distance to changes in intermediate frequency is the physical input source for the entire system.

[0027] At this time, the output intermediate frequency signal is discontinuous in the time domain, such as... Figure 2 The second step requires making the data between Chirps continuous. 2. Microcontroller (ADC + template matching-based missing segment backfilling + DAC) Physical connection: Intermediate frequency signal output from electromagnetic transceiver → Microcontroller ADC; Digital processing is completed internally by the microcontroller → DAC outputs continuous intermediate frequency signal.

[0028] Functional association: ADC: Samples intermediate frequency signals to obtain digital data; Digital processing: Executes a template matching-based missing segment backfilling algorithm to solve the data truncation problem between different chirs; ensures the continuity and smoothness of the intermediate frequency signal, and avoids audio output breaks or noise.

[0029] DAC: Converts the processed continuous intermediate frequency signal back into an analog signal for subsequent filtering and down-conversion.

[0030] The processed intermediate frequency (IF) is continuous in the time domain, with no missing data segments, such as... Figure 5 3. Bandpass filter module Physical connection: Microcontroller DAC output → Bandpass filter → Downconversion module.

[0031] Functional correlation: Filters out irrelevant frequency components and retains only the target intermediate frequency band (such as 50kHz–70kHz), improving signal purity and anti-interference capability.

[0032] 4. Down-conversion module (multiplier + low-pass filter) Physical connection: Bandpass filter output → Multiplier (mixed with low-frequency local oscillator signal) → Low-pass filter → Audio power amplifier module.

[0033] Functional association: Multiplier: Multiplies the smoothed intermediate frequency signal with the low-frequency local oscillator signal to generate the sum frequency and difference frequency; Low-pass filter: filters out high-frequency components and retains only the difference frequency components, so that the signal falls into the audible frequency range of 20 Hz-20 kHz.

[0034] Core function: To achieve spectrum shifting from intermediate frequency to audio frequency.

[0035] 5. Audio Amplifier Module Physical connection: Downconverter module output → Power amplifier → Audio output module.

[0036] Functional association: Amplifies the audio signal to provide sufficient energy to drive the speaker.

[0037] 6. Audio output module (speaker) Physical connection: power amplifier output → speaker.

[0038] Functional integration: Converts electrical signals into sound waves to create real-time audio feedback. Pitch dynamically changes with the distance from the hand, enabling non-contact music control.

[0039] A working method of an electromagnetic wave music sound sensing and control system, see [link to documentation]. Figure 1 Specifically, it includes the following steps: Step 1: Map the distance between the hand and the radar antenna into an intermediate frequency signal. A frequency-modulated continuous wave (FMCW) signal with a linearly varying frequency over time is transmitted via an electromagnetic transceiver. This signal is reflected upon encountering a hand target and captured by a receiving antenna. Due to the time delay τ between the transmitted and echo signals, which is proportional to the target distance d, and because the transmitted signal is a linearly frequency-modulated wave, the intermediate frequency (IF) signal output after mixing has a fixed frequency, the value of which is determined by the following formula: Where S is the frequency modulation slope and c is the speed of light; by controlling the frequency modulation slope It can precisely adjust the intermediate frequency range (e.g., 50kHz-70kHz) corresponding to a certain distance range (e.g., 1m-1.4m), so that the change in the distance between the hand and the radar is linearly mapped to the change in the intermediate frequency. Step 2: Perform template matching-based missing segment backfilling on the intermediate frequency signal. Because the FMCW radar has idle time between adjacent continuous wave signal chirps, the output intermediate frequency signal is discontinuous in the time domain, resulting in audio breaks or noise; therefore, the microcontroller executes the following sub-steps: 1) During the chirp duration of each continuous wave signal, the intermediate frequency (IF) signal is sampled using an ADC to obtain IF data segments, such as... Figure 2 ; 2) Select a segment of data at the end of the current continuous wave signal chirp, determine whether this segment shows an upward or downward trend, and record the value of the break point as a reference value, such as... Figure 3 ; 3) Since the data is a periodic signal, based on the filtering criteria of "consistent trend + similar reference amplitude," search for matching data segments after the break point, starting from the current Chirp data start position. For example... Figure 4 ; 4) Then fill in the gaps with the matching data to form a continuous periodic signal over a period of time, such as... Figure 5 .

[0040] Step 3: Perform bandpass filtering on the intermediate frequency signal after it becomes continuous in the time domain. The intermediate frequency signal, after template matching-based missing segment backfilling, is input into the bandpass filter module. The passband bandwidth of the bandpass filter is 20 kHz, and its lower cutoff frequency is determined based on the closest distance between the hand and the radar, and its upper cutoff frequency is determined based on the farthest distance. It is used to filter out out-of-band high-frequency noise and retain the intermediate frequency signal within the effective ranging frequency band. Step 4: Down-convert the intermediate frequency signal to an audible audio frequency band. The intermediate frequency signal after bandpass filtering is mixed with a low-frequency local oscillator signal of a fixed frequency in an analog multiplier to generate a mixed signal containing the sum frequency and the difference frequency. The high-frequency sum frequency component is then filtered out by a low-pass filter with a cutoff frequency of 20 kHz, leaving only the difference frequency component. The frequency of this difference frequency signal falls within the audible range of 20 Hz–20 kHz and is used as the audio signal output. The mixing principle is as follows: Let the intermediate frequency signal be The reference local oscillator (LO) signal is: Inputting both into the multiplier, the output is: Expand using trigonometric identities: The output can be seen to contain two frequency components: and High-frequency components are filtered out by a low-pass filter with a cutoff frequency of 20kHz. Only the difference frequency component is retained, thus obtaining the down-converted audio signal; Step 5: Amplify the audio signal and play it. The difference frequency audio signal is input to the audio power amplifier module for power amplification to provide sufficient energy to drive the speaker; the speaker converts the amplified electrical signal into sound waves to form real-time audio feedback; the user can dynamically adjust the output pitch by changing the distance between their hand and the radar, thus achieving non-contact music control.

[0041] The closest distance to the hand is 1 m, corresponding to a lower intermediate frequency cutoff frequency of 50 kHz; the furthest distance is 1.4 m, corresponding to an upper intermediate frequency cutoff frequency of 70 kHz.

[0042] This embodiment demonstrates that, compared with the prior art, the physical consistency mapping link of "distance-mid frequency-audible audio" in this invention provides more intuitive interaction and more real-time response.

[0043] like Figure 1 As shown, this invention uses an FMCW electromagnetic transceiver as the front-end sensing unit. The change in distance between the hand and the radar antenna is directly converted into a change in intermediate frequency after mixing under a linear frequency modulation system (as shown in the embodiment). The correspondence is clear in physical meaning and monotonicity, avoiding the recognition uncertainty and system lag caused by traditional image / gesture recognition or offline spectrum analysis, and ensuring the consistency and interpretability of "hand displacement - pitch change" from the source.

[0044] This invention addresses the critical issue of "intermediate frequency time domain discontinuity" caused by gaps between FMCW radar chirps by proposing a core algorithm of "missing segment backfilling based on template matching," which significantly improves audio continuity and listening quality.

[0045] The FMCW radar has idle time between adjacent chirps, resulting in periodic "missing segments" in the intermediate frequency signal. Figure 2 The missing information is visually demonstrated: there are interruptions in the intermediate frequency waveforms of each chirp. If directly down-converted to the audible frequency band, this easily manifests as breaks, pops, or noise at the audio output. To solve this problem, this invention introduces real-time, lightweight backfilling processing at the microcontroller level: like Figure 3 As shown, first extract a segment of data from the end of the current Chirp and determine the trend (rising / falling), while recording the amplitude of the breakpoint as a reference; like Figure 4As shown, based on the condition of "consistent trend + similar reference value amplitude", find the segment that matches the break point from the current Chirp start segment; like Figure 5 As shown, matching segments are filled into missing segments, thereby splicing the originally segmented intermediate frequency sequence into a time-continuous periodic signal.

[0046] This algorithm is designed directly around the engineering goal of "continuous audio output". It has low computational cost, is suitable for real-time implementation on MCUs, and does not rely on complex FFT / offline analysis equipment. It is a key technology to support the realization of high-quality "hand movement-audio feedback" interaction.

[0047] The present invention has a simpler structure, fewer components, and higher integration, reducing size and cost while improving its engineering feasibility.

[0048] from Figure 1 As can be seen from the system block diagram, the main links of this invention consist of: an electromagnetic transceiver, a microcontroller (ADC + backfill algorithm + DAC), a bandpass filter, an analog multiplier + a low-pass filter (down-conversion), an audio power amplifier, and a speaker.

[0049] Compared with existing ultrasonic solutions, this invention does not require a piezoelectric transducer and its high-frequency oscillation / acquisition link, nor does it require the collaboration of multiple modules such as a frequency analyzer, magnetic tape recorder, and external signal generator. Therefore, it has advantages in terms of system complexity, debugging difficulty, maintenance cost, overall size and power consumption control, and is suitable for product integration.

[0050] The end-to-end link of this invention enables a continuous, low-latency human-computer interactive pitch control experience.

[0051] This invention completes the closed-loop process by using radar mixing to obtain the intermediate frequency → real-time backfilling by the MCU to achieve time-domain continuity → analog output by the DAC → analog down-conversion to obtain the audible difference frequency → power amplifier to drive the speaker. Figure 1 This avoids the long chain of acquisition-offline analysis-calculation modulation-regeneration / driving in existing ultrasound solutions, making the feedback from hand movement to pitch change more direct and coherent, which is conducive to obtaining an intuitive and smooth interactive experience.

Claims

1. An electromagnetic wave music sound sensing and control system, characterized in that, include: An electromagnetic transceiver is used to transmit frequency-modulated continuous wave signals and receive echo signals reflected from the hand. After mixing, it outputs an intermediate frequency signal. The frequency of the intermediate frequency signal is proportional to the distance between the hand and the radar. The microcontroller is used to perform analog-to-digital conversion sampling of the intermediate frequency signal and to perform template matching-based missing segment backfilling processing to convert the intermediate frequency signal into a continuous time-domain signal, which is then output as an analog signal via the microcontroller's DAC. The bandpass filter module is connected to the output of the microcontroller and is used to filter out signals outside the frequency band and smooth the output. Its passband bandwidth is 20kHz. The lower cutoff frequency is determined based on the closest value of the hand distance radar, and the upper cutoff frequency is determined based on the farthest value of the hand distance radar. The downconversion module includes an analog multiplier and a low-pass filter. The analog multiplier multiplies the intermediate frequency signal after bandpass filtering with the reference local oscillator signal and outputs a mixed signal containing sum and difference frequency components. The low-pass filter has a cutoff frequency of 20kHz and is used to filter out the sum frequency component and retain the difference frequency audio signal that falls within the range of human hearing. An audio amplifier module is used to amplify the difference frequency audio signal; A loudspeaker is used to play amplified audio signals, and its pitch responds in real time to changes in the distance of a hand gesture.

2. The electromagnetic wave music sensing and control system according to claim 1, characterized in that, After the electromagnetic transceiver detects a target ahead, it generates a periodic signal, the frequency of which corresponds one-to-one with the distance to the target. Because the radar transmits at intervals, there will be a data gap in the middle of the periodic signal generated by the radar. The missing data is filled in using a template matching-based missing segment backfilling algorithm, as detailed below: 1) During the chirp duration of each continuous wave signal, the intermediate frequency signal is sampled by the ADC to obtain intermediate frequency data segments; 2) Select a segment of intermediate frequency data at the end of the current continuous wave signal Chirp, determine whether this segment of data is trending upward or downward, and record the value of the interruption point as a reference value; 3) Based on the filtering criteria of "consistent trend + similar reference value amplitude", search for matching data segments after the break point starting from the current Chirp data start position; 4) Then fill in the missing data with the matching data to form a continuous periodic signal over a period of time.

3. The electromagnetic wave music sensing and control system according to claim 1, characterized in that, The range that the human ear can perceive is a signal frequency of 20Hz-20kHz.

4. The electromagnetic wave music sensing and control system according to claim 1, characterized in that, The method for determining whether the data at the end of the Chirp is in an upward or downward trend is as follows: Select the first n data points of the data at the end of the Chirp, and use a voting-based trend indicator to see if the number of "positive / non-negative" values ​​in the adjacent differences of the first n data points exceeds the number of "negative" values. If the number of positive / non-negative values ​​is greater, it is judged as an upward trend; otherwise, it is judged as a downward trend.

5. The electromagnetic wave music sensing and control system according to claim 1, characterized in that, The reference local oscillator signal is a sinusoidal signal with a fixed frequency, and its frequency is configured so that the difference frequency audio signal falls within the range of human hearing perception of 20Hz to 20kHz.

6. The electromagnetic wave music sensing and control system according to claim 1, characterized in that, The electromagnetic transceiver uses an FMCW radar, and the frequency modulation slope of the transmitted signal is adjustable.

7. The electromagnetic wave sound sensing and control system according to claim 1 is applied to the construction of a non-contact audio interactive device, comprising: Audio art installations, children's music education equipment, upper limb motor rehabilitation training auxiliary equipment, or intelligent speaker gesture control systems; in which users can change the distance between their hands and the radar by moving their hands in space, and adjust the pitch of the output audio in real time to achieve intuitive and smooth sound interaction feedback.

8. The method of operating the electromagnetic wave music sound sensing and control system according to any one of claims 1-7, characterized in that, Specifically, the following steps are included: Step 1: Map the distance between the hand and the radar antenna into an intermediate frequency signal. An FMCW signal with a frequency that varies linearly with time is transmitted via an electromagnetic transceiver. This signal is reflected upon encountering a hand target and captured by a receiving antenna. Due to the time delay τ between the transmitted and echo signals, which is proportional to the target distance d, and because the transmitted signal is a linear frequency modulated wave, the intermediate frequency (IF) signal output after mixing has a fixed frequency, the value of which is determined by the following formula: Where S is the frequency modulation slope and c is the speed of light; thus, the change in the distance between the hand and the radar is linearly mapped to the change in the intermediate frequency. Step 2: Perform template matching-based missing segment backfilling on the intermediate frequency signal. The FMCW radar has idle time between adjacent continuous wave signal chirps, causing the output intermediate frequency signal to be discontinuous in the time domain, resulting in audio breaks or noise; to address this, the microcontroller executes the following sub-steps: 1) During the chirp duration of each continuous wave signal, the intermediate frequency signal is sampled by the ADC to obtain intermediate frequency data segments; 2) Select a segment of data at the end of the current continuous wave signal Chirp, determine whether this segment of data is trending upward or downward, and record the value of the interruption point as a reference value; 3) Based on the filtering criteria of "consistent trend + similar reference value amplitude", search for matching data segments after the break point starting from the current Chirp data start position; 4) Then fill in the missing data with the matching data to form a continuous periodic signal over a period of time; Step 3: Perform bandpass filtering on the intermediate frequency signal after it becomes continuous in the time domain. The intermediate frequency signal processed in step 2 is input into the bandpass filter module. The passband bandwidth of the bandpass filter is 20 kHz. Its lower cutoff frequency is the frequency output by the radar when the hand is at the closest distance to the radar, and its upper cutoff frequency is the frequency output by the radar when the hand is at the farthest distance to the radar. It is used to filter out high-frequency noise outside the band and retain the intermediate frequency signal in the effective ranging frequency band. Step 4: Down-convert the intermediate frequency signal to an audio frequency band that the human ear can perceive. The intermediate frequency signal after bandpass filtering is mixed with a low-frequency local oscillator signal of a fixed frequency in an analog multiplier to generate a mixed signal containing the sum frequency and the difference frequency. The high-frequency sum frequency component is then filtered out by a low-pass filter with a cutoff frequency of 20 kHz, leaving only the difference frequency component. The frequency of this difference frequency signal falls within the range of human hearing of 20 Hz–20 kHz and is used as the audio signal output. Step 5: Amplify the audio signal and play it. The difference frequency audio signal is input to the audio power amplifier module for power amplification to provide sufficient energy to drive the speaker; the speaker converts the amplified electrical signal into sound waves to form real-time audio feedback; the user can dynamically adjust the output pitch by changing the distance between their hand and the radar, thus achieving non-contact music control.

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