A light energy integration system based on a target side photovoltaic receiver and a transmission waveform design method

Abstract

The application discloses a kind of light through energy integration system and transmitting waveform design method based on target side photovoltaic receiver, system first generates MLS sequence, simultaneously to original signal PAM modulation obtains PAM sequence, using PAM sequence as slow envelope to MLS sequence is modulated with envelope, obtains envelope modulated signal, envelope modulated signal is superimposed after digital-analog conversion direct current component to complete ac-dc coupling, output analog electric signal.Transmitter converts analog electric signal into optical signal, part of optical signal is reflected back to the transmitting end to realize distance perception, part of optical signal is converted into electric signal by photovoltaic receiver, electric signal extracts ac-dc signal, direct current signal is used for energy collection, and alternating current signal is used for information decoding.The application uses flexible MLS-PAM envelope modulation waveform, which can realize more lightweight, energy-saving and universal system design, break the cascade constraint of low-bandwidth photovoltaic sampling rate, and realize flexible compromise of through, energy and function.

Description

Technical Field

[0001] This invention relates to an integrated optical communication and sensing system, specifically to an integrated optical communication and sensing system based on a target-side photovoltaic receiver and a method for designing the transmitted waveform, belonging to the field of wireless optical communication technology. Background Technology

[0002] The Industrial Internet of Things (IIoT) significantly improves the observability and controllability of industrial systems by deploying sensing terminals on a large scale in key equipment and production lines to build high-fidelity industrial digital twins. Sensor-Integrated Communication (ISAC) extracts physical environment features while completing information exchange, greatly improving resource utilization and is considered a key technological paradigm for empowering the IIoT. However, the rapid growth and expansion of edge nodes has led to a rapid increase in continuous power supply and maintenance costs, especially in remote or extreme operating scenarios where personnel cannot reach. Wireless Power Transfer (WPT), as a contactless power supply method, provides a solution for the long-term operation of large-scale low-power terminals. Driven by the 6G vision, future network infrastructure is expected to support high-speed data exchange and centimeter-level precision sensing in a sustainable manner, giving rise to the Sensor-Integrated Communication and Power Transfer (ICSPT) architecture to achieve multi-dimensional integrated gains. At the same time, the contradiction between radio frequency (RF) spectrum congestion and growing business demands continues to intensify, and electromagnetic interference and security constraints are also faced in complex industrial environments. Optical wireless technology has natural advantages in spectrum resources, sensing accuracy and energy efficiency, and possesses electromagnetic immunity and enhanced security characteristics. It is considered an important carrier for breaking through radio frequency bottlenecks, thereby promoting the development of optical communication and sensing integrated technology (O-ICSPT).

[0003] Regarding the integrated optical communication, sensing, and energy harvesting system, the applicant previously filed two invention patents. Patent application number 202510172128.4, entitled "Integrated Optical Communication, Sensing, and Energy Harvesting System," first proposed and experimentally verified an optical integrated system that simultaneously supports communication, sensing, and energy transmission. Experimental results show that the transmitted waveform of the integrated optical communication, sensing, and energy harvesting system can be equivalently decomposed into an alternating current (AC) component for communication and sensing and a direct current (DC) component for energy transmission, which work collaboratively through superposition and coupling. Based on this waveform structure characteristic, patent application number 202511977650.6, entitled "An Integrated Optical Communication, Sensing, and Energy Harvesting System and Transmitted Waveform Design Method," further proposed a hybrid waveform design scheme combining inter-AC amplitude allocation and AC-DC amplitude allocation. This achieves a flexible trade-off between communication, sensing, and energy harvesting performance in the integrated optical communication, sensing, and energy harvesting system, and utilizes a beam splitter-free integrated design of the target-side photodiode (PD) and photovoltaic (PV) to achieve a lighter hardware architecture. The aforementioned integrated optical communication and sensing systems all employ a hybrid PD / PV receiver architecture on the target side. This architecture leverages the rapid response of PD to high-frequency AC signals and the efficient power conversion capability of PV to DC components, making it highly attractive for energy-constrained industrial IoT terminals that require high-speed communication. However, the hybrid PD / PV architecture faces some limitations in practical deployment. On one hand, the PD requires an external power supply to provide a reverse bias voltage to maintain its linear operating range, inevitably introducing additional static power consumption on the target side. On the other hand, the photosensitive area of ​​the PD is typically only on the order of square millimeters, making the system extremely sensitive to spatial alignment errors and terminal attitude jitter. Furthermore, the hybrid PD / PV architecture does not achieve true hardware reuse, increasing the hardware complexity of the receiver. Therefore, exploring integrated optical communication and sensing systems based on target-side photovoltaic receivers is clearly necessary for industrial IoT terminals facing extreme energy scarcity, dynamic spatial topology changes, and stringent constraints on size, weight, and power consumption (SWaP).

[0004] Despite their significant application potential, the application of target-side photovoltaic (PV) receiver architectures in integrated optical communication and sensing systems still faces dual bottlenecks in communication rate and sensing resolution. Typically, the cutoff frequency of commercial PV devices is only in the range of hundreds of hertz to several megahertz, significantly lower than traditional PD receiver links. This inherent constraint drastically compresses the available modulation bandwidth and directly limits the digital-to-analog (D / A) conversion sampling rate at the transmitter. While applying an external negative bias voltage can extend the PV bandwidth and thus improve the communication rate to some extent, this approach is limited in effectiveness and deviates from the design intent of a receiver without additional static power consumption. Multiple-input multiple-output (MIMO) technology is an effective means of expanding the communication capacity of PV receivers. However, the low bandwidth of PV devices introduces a new contradiction in integrated optical communication and sensing systems. Specifically, the limited D / A sampling rate at the transmitter restricts the sampling rate of the analog-to-digital (A / D) conversion of the sensed echo signal, thereby worsening the distance resolution, which is closely related to the A / D sampling rate. Even if an A / D sampling rate much higher than that of D / A is forcibly applied to the echo signal, this strategy of relying on ultra-high upsampling to compensate for the sampling rate difference will significantly amplify the interpolation error and introduce severe spectral artifacts, ultimately leading to waveform reconstruction distortion and a sharp decline in the accuracy of time delay estimation.

[0005] Transmit waveform design is a core element determining the overall performance of an integrated optical-sensing-energy system in terms of communication, sensing, and energy harvesting. While the DC component inherently imposes pruning constraints on the AC waveform, it is not inherently limited by the sampling rate. AC waveform design can serve as a key means to overcome the aforementioned sampling rate bottleneck. The design of the AC waveform essentially corresponds to the waveform design problem in optical-sensing integration (O-ISAC). Around optical-sensing integration, various waveform design schemes have been proposed, including Orthogonal Frequency Division Multiplexing (OFDM), Pulse Amplitude Modulation (PAM), and OFDM Embedded Maximum Longest Sequence (MLS). OFDM-based waveforms are more suitable for communication, while pulse-based waveforms are better suited for sensing requirements. MLS is widely used in various sensing systems due to its superior correlation characteristics. Inspired by this, existing integrated optical-sensing-energy systems use OFDM or time-domain hybrid maximum longest sequence (MLS)-OFDM as the AC waveform. However, the above typical waveforms and their combinations are only suitable for larger DAC sampling rates and are difficult to directly adapt to the low bandwidth constraints of photovoltaic receivers.

[0006] Therefore, it is urgent to propose an integrated optical communication and energy sensing system architecture for industrial IoT terminals that are extremely energy-scarce, dynamically changing in spatial topology, and subject to stringent power consumption constraints, and to design corresponding waveforms for this architecture. Summary of the Invention

[0007] To address the constraints of existing target-side hybrid PD / PV receiver integrated optical communication, sensing, and energy-saving architectures in terms of energy consumption, dynamic operating conditions, and hardware multiplexing, as well as the significant degradation of sensing resolution caused by using photovoltaic receivers on the target side, this invention aims to propose an integrated optical communication, sensing, and energy-saving system and a transmit waveform design method based on a target-side photovoltaic receiver. This invention employs a flexible MLS-PAM envelope modulation waveform, enabling a lighter, more energy-efficient, and universally applicable system design. It breaks the cascading constraints of low-bandwidth photovoltaic sampling rates and allows for flexible trade-offs among communication, sensing, and energy-saving technologies.

[0008] The technical solution of this invention is implemented as follows:

[0009] An integrated optical-sensing-energy system based on a target-side photovoltaic receiver includes a sensing signal generator, a digital-to-analog converter (DAC), a transmitter, a photovoltaic receiver, an information decoding module, an energy harvesting module, and a sensing processing module for generating integrated sensing digital signals. The sensing signal generator, DAC, and transmitter are located at the transmitting end, while the photovoltaic receiver, information decoding module, and energy harvesting module are located at the receiving end. A power coupling unit is provided between the DAC and the transmitter. The sensing signal generator includes an MLS modulation unit, a PAM modulation unit, and an envelope modulation unit. The MLS modulation unit generates an MLS sequence using a linear feedback shift register based on primitive polynomials. The PAM modulation unit modulates the input raw signal using PAM to obtain a PAM sequence. The envelope modulation unit uses the PAM sequence as a slow envelope to perform envelope modulation on the MLS sequence, resulting in an MLS-PAM envelope-modulated AC signal. The MLS-PAM envelope-modulated AC signal is converted to an analog signal by a digital-to-analog converter and then enters the power coupling unit. The power coupling unit superimposes a DC component onto the MLS-PAM envelope-modulated AC signal to achieve AC-DC coupling. The power coupling unit outputs an analog electrical signal after AC-DC power coupling. The transmitter converts the analog electrical signal into an optical signal, which is simultaneously connected to the sensing and processing module and the photovoltaic receiver. The photovoltaic receiver outputs the received optical signal as an electrical signal. This electrical signal is then processed by a power separation unit to extract the DC and AC signals. The DC signal is connected to the energy harvesting module, and the AC signal is connected to the information decoding module.

[0010] Furthermore, the sensing processing module includes a light reflector, a photodiode, and an analog-to-digital converter (ADC). The reflector is located at the receiving end, and the photodiode and ADC are located at the transmitting end. The light beam reflected by the light reflector is converted into an analog electrical signal by the photodiode, and the analog electrical signal is converted into a digital signal by the ADC. The original MLS-PAM envelope modulation AC signal output by the sensing signal generator is connected to the upsampling module. The upsampling module upsamples the time-domain samples of the MLS-PAM envelope modulation AC signal generated by the sensing signal generator at the same upsampling rate. The output of the upsampling module and the output of the ADC are connected to the cross-correlation module, respectively. The cross-correlation module uses a time-domain cross-correlation method to perform distance measurement using the time-domain samples of the MLS-PAM envelope modulation AC signal generated by the sensing signal generator and the MLS-PAM envelope modulation AC signal converted by the ADC, thereby achieving sensing capability.

[0011] Furthermore, the information decoding module includes an analog-to-digital converter and a PAM demodulation module. The AC signal separated by the power separation unit is converted into a digital signal by the analog-to-digital converter, and the digital signal enters the PAM demodulation module. In the PAM demodulation module, the digital signal is processed by synchronization to obtain a discrete received signal sequence y[n]. PAM symbol decision is achieved using incoherent detection based on envelope statistics. The average amplitude of the k-th symbol time interval is taken as the envelope estimate. As shown in the following formula,

[0012]

[0013] This refers to the number of discrete-time samples corresponding to each PAM symbol; assuming the original envelope amplitude corresponding to the training sequence is a. tr And its corresponding received signal envelope is estimated as z tr Then the least squares estimates of the equivalent channel gain g and baseline offset o , Calculated as

[0014]

[0015] Where X=[a tr [1] Based on the extracted channel feature parameters, the equivalent envelope amplitude of all received symbols is equalized according to the following formula.

[0016]

[0017] The amplitude of the received PAM symbol after equalization;

[0018] Subsequently, the PAM sign decision is made according to the maximum likelihood criterion using the following formula.

[0019]

[0020] The amplitude of the finally recovered received PAM symbol;

[0021] The final recovered PAM symbol is inversely mapped to a binary bit sequence to obtain the decoding result.

[0022] Furthermore, the energy harvesting module supplies power to various loads by separating the DC signal from the power separation unit.

[0023] This invention also provides a method for designing the transmitted waveform of an integrated optical-to-energy sensing system, wherein the integrated optical-to-energy sensing system is the aforementioned target-side photovoltaic receiver-based integrated optical-to-energy sensing system, and the method is carried out according to the following steps.

[0024] 1) First, generate an MLS sequence, and then simultaneously perform PAM modulation on the original signal to obtain a PAM sequence;

[0025] 2) Using a PAM sequence as a slow envelope to perform envelope modulation on a fast MLS sequence, an MLS-PAM envelope-modulated AC signal is obtained;

[0026] 3) The MLS-PAM envelope modulation AC signal is converted from digital to analog. The normalized MLS-PAM envelope modulation AC signal is mapped to the quantized output level according to the preset inter-peak voltage. Then, a DC component is superimposed on the MLS-PAM envelope modulation AC signal to complete AC-DC coupling, thereby generating an analog electrical signal for driving the transmitter.

[0027] 4) The analog electrical signal is converted into an optical signal by the transmitter. The optical signal is the transmitted waveform of the optical communication and sensing integrated system. The transmitted waveform contains an AC component and a DC component. The AC component carries communication and sensing information, while the DC component provides the main energy source. The transmitted waveform is processed accordingly to realize information decoding, sensing processing and energy harvesting.

[0028] Furthermore, let the bipolar MLS sequence of length L be denoted as m[l], l∈{0,1,…,L-1}; the amplitude set of the unipolar PAM sequence of order M is... , The average level amplitude is ;

[0029] The peak amplitude ratio α is defined as the ratio of the minimum to the maximum value in the amplitude set of a PAM sequence, expressed as:

[0030]

[0031] The amplitude set of a PAM sequence is represented as follows:

[0032]

[0033] Let i be the level index corresponding to the k-th PAM symbol in the PAM sequence. k , Then the envelope symbol amplitude sequence is defined as

[0034]

[0035] Each PAM symbol in the PAM sequence lasts for N seconds. rep If there are N MLS base sequence periods, then the number of discrete-time samples corresponding to each PAM symbol is N. sps =N rep L; Let the set of discrete-time indices corresponding to the k-th MLS-PAM envelope modulation symbol be denoted as The AC waveform within the k-th symbol interval is represented as follows:

[0036]

[0037] Where m[·] is periodically extended with period 𝐿; the entire MLS-PAM envelope modulation AC sequence is

[0038]

[0039] in This represents the floor operator.

[0040] Furthermore, the peak amplitude ratio α is set as an adjustable parameter to achieve a continuously adjustable tradeoff between communication reliability and sensing robustness; and in conjunction with the DC component configuration, a joint tradeoff is achieved between the performance of communication, sensing and energy harvesting.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The optical communication and sensing integrated system of the present invention uses a pure photovoltaic receiver on the target side, which breaks the constraints of the existing hybrid PD / PV architecture in terms of additional static power consumption, dynamic operating condition adaptability and deep hardware reuse, and can realize a lighter, more energy-efficient and universal system design.

[0043] 2. The flexible MLS-PAM envelope modulation waveform proposed in this invention decouples the AC signal bandwidth from the envelope signal bandwidth by introducing a multiplicative structure of a slow pulse amplitude modulation envelope and a fast MLS sequence inside the AC signal, thus solving the problem of drastic degradation of sensing resolution caused by low bandwidth of photovoltaics.

[0044] 3. This invention further proposes a performance trade-off mechanism, innovatively setting the peak-to-amplitude ratio of the pulse amplitude modulation level as an adjustable parameter, thus achieving a continuously adjustable trade-off between communication reliability and sensing robustness. This trade-off mechanism, in conjunction with the DC component configuration, achieves a joint trade-off between communication and sensing performance. Attached Figure Description

[0045] Figure 1 - A schematic diagram of the integrated optical communication and sensing system of the present invention, equipped with a photovoltaic receiver on the target side.

[0046] Figure 2 - The MLS-PAM envelope modulation waveform design criteria and related characteristic diagrams proposed in this invention; wherein, (a) waveform design criteria; (b) cross-correlation comparison of different waveforms.

[0047] Figure 3 -Characteristic diagrams of MLS-PAM envelope modulation waveforms under different peak amplitude ratios according to the present invention; wherein, (a) waveform clusters; (b) cross-correlation curves.

[0048] Figure 4 - Schematic diagram of the experimental device for the integrated optical communication and sensing system of the present invention, which is equipped with a photovoltaic receiver on the target side.

[0049] Figure 5 - Equal power Vpp mapping for different α schemes in this embodiment of the invention; wherein, (a) a lookup table of simulated average AC transmit power α and Vpp; (b) verification of the analysis model P(α, Vpp) relative to the simulation results; (c) equal power Vpp-α mapping curve with (α0, Vpp0) as reference.

[0050] Figure 6 - Performance curves of the integrated optical communication, sensing, and energy harvesting system under different Vpp0 and bias current settings of this invention; wherein, (a)-(c) respectively reflect the changes in communication, sensing, and energy harvesting performance with Vpp0; (d)-(f) respectively reflect the changes in communication, sensing, and energy harvesting performance with bias current.

[0051] Figure 7 - A schematic diagram of the performance of the integrated optical communication and sensing system under different peak amplitude ratios (P / V) of the present invention; wherein, (a) performance changes with P; (b) symbols received by the selected target end at the marker point; (c) cross-correlation curve at the marker point; (d) I-V characteristics at the marker point.

[0052] Figure 8 - A schematic diagram of the performance of the integrated optical communication and sensing system under dynamic conditions of the present invention; wherein, (a) the performance varies with the link distance; and (b) the performance varies with the incident angle. Detailed Implementation

[0053] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0054] See Figure 1 This invention discloses an integrated optical-sensing-energy system based on a target-side photovoltaic receiver, comprising a sensing signal generator, a digital-to-analog converter (DAC), a transmitter, a photovoltaic receiver, an information decoding module, an energy harvesting module, and a sensing processing module for generating integrated sensing digital signals. The sensing signal generator, DAC, and transmitter are disposed at the transmitting end, while the photovoltaic receiver, information decoding module, and energy harvesting module are disposed at the receiving end. A power coupling unit is provided between the DAC and the transmitter. The sensing signal generator includes an MLS modulation unit, a PAM modulation unit, and an envelope modulation unit. The MLS modulation unit generates an MLS sequence using a linear feedback shift register based on primitive polynomials. The PAM modulation unit modulates the input original signal using PAM to obtain a PAM sequence. The envelope modulation unit uses the PAM sequence as a slow envelope to perform envelope modulation on the MLS sequence, resulting in an MLS-PAM envelope-modulated AC signal. The MLS-PAM envelope modulated AC signal is converted by a digital-to-analog converter and then enters the power coupling unit. The power coupling unit superimposes a DC component onto the MLS-PAM envelope modulated AC signal to achieve AC-DC coupling. The power coupling unit outputs an analog electrical signal after AC-DC power coupling. The transmitter is a laser diode (LD), used to convert the analog electrical signal into an optical signal. The optical signal is simultaneously connected to the sensing and processing module and the photovoltaic receiver. The photovoltaic receiver outputs the received optical signal as an electrical signal. This electrical signal is then processed by a power separation unit to extract the DC and AC signals. The DC signal is connected to the energy harvesting module, and the AC signal is connected to the information decoding module.

[0055] Unlike existing hybrid PD / PV receivers with integrated optical communication and sensing capabilities on the target side, the proposed integrated optical communication and sensing system utilizes a pure photovoltaic receiver on the target side. This invention employs a large-area photovoltaic array to simultaneously capture AC signals and DC energy, effectively reducing the system's sensitivity to spatial alignment while significantly minimizing power consumption. Furthermore, to support the retroreflection echo link, a retroreflector is installed at the target node to enhance echo signal quality and improve sensing distance and accuracy. Specifically, this invention uses a flexible, lightweight retroreflective film at the target node instead of a traditional corner cube reflector, greatly improving the ease of terminal deployment. Given that the transmitting end typically possesses ample energy reserves and hardware resources, the echo detection link still utilizes a wide-bandwidth photodiode (PD) to ensure reliable reception of high-frequency AC echo signals.

[0056] This invention mainly involves four parts: MLS-PAM envelope waveform generation, information decoding module, sensing and processing module, and energy harvesting module. These four parts will be described in detail below.

[0057] 1. Flexible MLS-PAM envelope waveform generation

[0058] The AC signal uses MLS as the sensing basis sequence and PAM envelope as the communication sequence. First, the MLS and PAM sequences are generated separately. A bipolar MLS sequence of length L (denoted as m[l], l∈{0,1,…,L-1}) is generated using a linear feedback shift register based on primitive polynomials. The amplitude set of a unipolar PAM symbol of order M is... , Its average level amplitude is .

[0059] The peak amplitude ratio α is defined as the ratio of the minimum to the maximum value in the PAM amplitude set, which determines the dynamic modulation range of the PAM level, and is expressed as:

[0060]

[0061] Given α and This allows us to determine the amplitude set of the complete PAM symbols used for communication mapping.

[0062]

[0063] A piecewise constant PAM amplitude sequence is used as a slow envelope to perform envelope modulation on a fast MLS sequence. Let the k-th ( The level index corresponding to each PAM symbol is i. k Then the envelope symbol amplitude sequence is defined as

[0064]

[0065] To illustrate this mapping mechanism more intuitively, a 2-PAM modulation example is given below without loss of generality. In this case, the envelope signal a[k] switches between two amplitude states, and its corresponding level set is simplified as follows:

[0066]

[0067] Each slow PAM symbol lasts for N seconds. rep If there are N MLS base sequence periods, then the number of discrete-time samples corresponding to each PAM symbol is N. sps =N rep L. Let the set of discrete-time indices corresponding to the k-th MLS-PAM envelope modulation symbol be denoted as Then the AC waveform in the k-th symbol interval is represented as

[0068]

[0069] Where m[·] is periodically extended with period 𝐿. Therefore, the entire MLS-PAM envelope modulation AC sequence can be written as

[0070]

[0071] in This represents the floor operator.

[0072] The detailed process of MLS-PAM envelope modulation waveform generation is as follows: Figure 2 As shown in (a), by constructing a multiplicative coupling structure between the slow PAM envelope and the fast MLS sequence within the AC waveform, the envelope component and the chip-level component can be configured at different time scales. Thanks to this multiplicative structure, the envelope level is stable within a single symbol interval, thus facilitating signal demodulation by the target-side photovoltaic receiver using the envelope statistical characteristics. Figure 2 (b) The cross-correlation results further confirm the advantages of the proposed multiplicative design. The PAM envelope waveform remains almost constant within each symbol interval, and the correlation output is mainly controlled by sparse envelope transitions rather than the actual propagation delay. Therefore, it cannot form a clear correlation peak, leading to significant ranging errors. In contrast, the MLS–PAM envelope modulation waveform, by preserving fast chip-level transitions, can generate a stable and prominent correlation peak dominated by the MLS autocorrelation characteristics, thus enabling high-precision sensing.

[0073] Figure 3 (a) shows the MLS-PAM envelope modulation waveforms generated under different peak amplitude ratios α. Observation reveals that α not only determines the minimum Euclidean distance of the PAM level set but also controls the overall dynamic range of the MLS-PAM envelope modulation signal. At a fixed average amplitude... Under the constraint, increasing α will cause A1 and A M As α approaches 1, the power distribution of the AC waveform becomes more uniform and increasingly closer to the ideal MLS sequence shape, thus enhancing perception performance by improving correlation. Figure 3 As shown in (b), the correlation peaks become increasingly prominent. In contrast, reducing α can improve the robustness of communication decisions by increasing the level spacing, but the increased envelope ripple leads to an imbalance in the time-domain power distribution and weakens the quality of the correlation peaks, thereby deteriorating sensing performance. Therefore, α provides a continuously adjustable tradeoff between communication reliability and sensing robustness, and together with the DC component configuration, determines the joint tradeoff between communication, sensing, and energy harvesting performance.

[0074] After D / A conversion, the normalized MLS-PAM envelope modulation signal is mapped to the quantized output level according to a preset peak-to-peak voltage (Vpp). A DC component is superimposed on this AC signal to complete AC-DC coupling, thereby generating an analog electrical signal for driving a laser diode (LD). The emitted optical signal thus contains both AC and DC components. The AC component carries communication and sensing information, while the DC component provides the primary energy source for photovoltaic energy harvesting, thus achieving deep integration of communication, sensing, and energy harvesting on a single optical link.

[0075] 2. Information Decoding Module

[0076] The information decoding module includes an analog-to-digital converter and a FAM demodulation module. A portion of the optical signal output by the transmitter is detected by the photovoltaic receiver on the target side, and the AC signal is extracted by the power separation unit. This AC signal is converted from analog to digital, and the digital signal enters the FAM demodulation module. In the FAM demodulation module, the digital signal is processed for synchronization to obtain a discrete received signal sequence y[n]. PAM symbol decision is achieved using incoherent detection based on envelope statistics. The mean amplitude of the k-th symbol time interval is taken as the envelope estimate.

[0077]

[0078] Linear fitting of the equivalent channel gain g and baseline offset o is performed using least squares (LS) criterion. Assume the original envelope amplitude corresponding to the training sequence is a. tr And its corresponding received signal envelope is estimated as z tr Then the least squares estimates of g and o can be calculated as follows:

[0079]

[0080] Where X=[a tr [1]. Based on the extracted channel feature parameters, the equivalent envelope amplitude of all received symbols is equalized.

[0081]

[0082] Subsequently, a PAM symbol decision is made based on the maximum likelihood (ML) criterion.

[0083]

[0084] The decoded result can be obtained by inversely mapping the recovered PAM symbols to a binary bit sequence. The performance of the information decoding module is evaluated by the bit error rate (BER).

[0085] 3. Sensing and Processing Module

[0086] The sensing processing module of this invention includes a light reflector, a photodiode, and an analog-to-digital converter (ADC). The reflector, consisting of a reflective film, is located on the receiving end, while the photodiode and ADC are located on the transmitting end. A portion of the light signal output from the transmitter is reflected back to the transmitting end by the light reflector. The reflected light beam undergoes photoelectric conversion by the photodiode, converting it into an analog electrical signal. The analog electrical signal is then converted into a digital signal by the ADC. The original MLS-PAM envelope modulation AC signal output from the sensing signal generator is connected to an upsampling module. The upsampling module upsamples the time-domain samples of the MLS-PAM envelope modulation AC signal generated by the sensing signal generator at the same upsampling rate. The outputs of the upsampling module and the ADC are connected to a cross-correlation module. The cross-correlation module uses a time-domain cross-correlation method to perform distance measurement using the time-domain samples of the MLS-PAM envelope modulation AC signal generated by the sensing signal generator and the MLS-PAM envelope modulation AC signal converted by the ADC, thereby achieving sensing capability.

[0087] Distance resolution of the present invention Depends on the sampling rate f of the A / D converter at the transmitting end s (Unit: Sa / s), expressed as

[0088]

[0089] in It is the speed of light. Clearly, f s The higher the value, the finer the precision of the delay quantization. However, there is an upsampling factor T=f between the echo link and the transmit link. s / f st , where f st This is the sampling rate of the D / A converter at the transmitting end. With a fixed f... s Under these conditions, the bandwidth limitation of the target-side photovoltaic receiver architecture forces f st The signal is extremely compressed, leading to a sharp increase in the upsampling factor. This ultra-large upsampling factor causes strong interpolation errors and spectral artifacts, ultimately degrading sensing performance. The MLS-PAM envelope waveform proposed in this invention achieves decoupling between the macroscopic AC bandwidth and the microscopic envelope bandwidth by nesting a multiplicative structure of a slow PAM envelope and a fast MLS chip within the AC signal. This mechanism allows the transmitter to maintain a high f-value even with limited overall bandwidth. stThis ensures that, within acceptable distance resolution, the system can control the overall oversampling factor within a suitable range with low distortion.

[0090] By analyzing the echo signal y s [n] and x s [n] Perform sliding cross-correlation to complete the Time-of-Flight (ToF) measurement, where x s [n] is the local upsampled version of the original MLS-PAM envelope modulated AC signal. Maximum likelihood estimation of time of flight. It can be represented as

[0091]

[0092] Where L w It is the length of the time-domain window used to truncate the signal and calculate the cross-correlation accumulation. Estimated distance. Depend on The performance of the sensing processing module is evaluated using the root mean square error of the ranging (RMSE).

[0093] 4. Energy Harvesting Module

[0094] The output electrical signal of the target-side photovoltaic receiver is processed by a power separation unit to extract the DC signal, which is then connected to the load. Achieving energy harvesting, in which This represents the set of candidate load resistors. The DC component of the photovoltaic output mainly depends on the average intensity of the incident beam and is used to continuously power the end-side load. The output voltage and output current at the DC port satisfy V(R) L )=I(R L )R L This means that the instantaneous states of both will dynamically drift along the current-voltage characteristic curve as the external load impedance changes. Therefore, the output power of the DC port can be expressed as P(R L )=V(R L ) I(R L ). Through load sets Scan within range R L The maximum harvestable power is uniquely determined by the maximum power point (MPP). The energy (HE) harvested at this point is calculated as follows:

[0095]

[0096] Where V MPP and I MPP These represent the output voltage and output current measured at the DC port when the maximum power point is achieved, respectively.

[0097] Let A eLet the effective photosensitive area of ​​the photovoltaic system be represented by the energy harvesting density of the integrated photovoltaic system. It characterizes the energy extraction capability achievable per unit photovoltaic area under maximum power point matching conditions.

[0098] To clearly describe the beneficial effects of the system framework and waveform design method, the following embodiments are provided to comprehensively evaluate the proposed integrated optical communication and sensing system. A hardware experimental platform for the integrated optical communication and sensing system was built for conceptual experimental verification. The system block diagram and experimental setup are shown below. Figure 4 As shown.

[0099] First, an MLS-PAM envelope modulation waveform was generated offline in MATLAB and loaded into an arbitrary waveform generator (AWG, UNI-T UTG9604T) to complete the D / A conversion. The analog AC waveform was set to a specific Vpp (unit: V) and then superimposed with the DC component (unit: V). Subsequently, a red laser diode LD (Ushio HL63603TG) was driven to emit an optical signal.

[0100] The light beam, after propagating through free space, is used for communication, energy harvesting, and ranging. The receiver integrates a photovoltaic (Triple-junction GaAs) module and a reflective film (3M 4090). A portion of the optical power is absorbed by the photovoltaic module and converted into electrical power. This electrical power is then decoupled into AC and DC power by a power separation circuit consisting of inductors and capacitors. The AC signal is sampled and recorded by a mixed-signal oscilloscope (OSC, Tektronix MSO044B) and forwarded to an offline digital module for communication signal demodulation. The DC power is impedance-matched via a sliding rheostat and its energy is measured by a digital power meter (Chroma 66205). Simultaneously, another portion of the beam is reflected back to the transmitter by the reflective film, captured by an avalanche photodiode (APD, Hamamatsu C12702-11), and converted into an electrical signal. This echo signal is sampled and recorded by an OSC (Tektronix MDO32), and the time of flight is estimated using sliding cross-correlation to obtain the distance between the transmitter and receiver.

[0101] The detailed experimental parameters are as follows: MLS base sequence length is L=15; PAM modulation order is M=2; each PAM symbol lasts for N. rep =10 MLS cycles; AWG sampling rate is f st =500 MSa / s; OSC sampling rate is f s =2.5 GSa / s; PV photosensitive area is 1 cm² 2 The reflective film measures 75 mm x 100 mm; the APD photosensitive area is 1 mm². 2Based on the above configuration, the effective communication bandwidth is 500 / (15 × 10) = 3.33 MHz. The distance resolution is 3 × 10⁻⁶. 8 / (2×2.5×10 9 Furthermore, all bit error rate tests were performed under no-load conditions, and all energy harvesting results were measured under maximum power point conditions.

[0102] 1. Isopower Vpp mapping under different peak amplitude ratios

[0103] To ensure fair comparisons across different peak amplitude ratio (α) configurations, maintaining a consistent transmit power budget is crucial. Given that different α values ​​inherently produce different average transmit powers under a fixed peak-to-peak voltage (Vpp), direct comparisons without calibration would result in low-α waveforms transmitting with lower actual power. Therefore, we derived and applied an equal-power mapping calibration method to Vpp in our experiments.

[0104] For 2-PAM modulation, the symbol amplitude takes the value a[k]∈{A1,A2}. M Assuming that 0 and 1 are equally probable in the pseudo-random information bitstream, then these two discrete levels, after mapping, have equal probabilities of appearing in the long sequence. MLS is a bipolar sequence, and its chip value set is {1, -1} with approximately equal probabilities of appearance. The final generated discrete-time AC sequence. Therefore, the obtained discrete-time AC sequence satisfies x AC [n]{-A M ,-A1,A1,A M}, where the probability of each element appearing is approximately 0.25. Since x AC The mean of [n] is zero, and its variance (i.e., average AC power) can be expressed as:

[0105]

[0106] In the experiment, the high level was calibrated as A. M =Vpp / 2, then the low level is A1=α×Vpp / 2. Therefore, the average transmit power of the AC signal is expressed as:

[0107]

[0108] When Vpp is fixed, the average transmit power increases with increasing α. To enforce equal power constraints across all α configurations, a baseline configuration α0 is introduced, with its corresponding Vpp denoted as the reference value Vpp0. All configurations are subject to constraints that must satisfy...

[0109]

[0110] This leads to the analytical expression for the equal power Vpp mapping relationship.

[0111]

[0112] like Figure 5 As shown in (a) and (b), the numerical simulation results are in high agreement with the analytical power model P(α,Vpp). Furthermore, Figure 5 (c) The derived mapping curves were plotted, confirming the accuracy and reliability of the power calibration method.

[0113] Based on this model, the present invention implements specific Vpp adjustments in actual measurements. The configuration with α=0.2 is selected as the baseline (α0=0.2), and its driving voltage is used as the reference value Vpp0. For other α configurations, their Vpp values ​​are adjusted according to formula (17) to maintain a constant transmit power. For example, when Vpp0=4.5 V, the calibrated corresponding Vpp values ​​for the α=0.4, 0.6, and 0.8 configurations are 4.275 V, 3.915 V, and 3.6 V, respectively. This equal-power mapping method is used throughout the rest of the present invention.

[0114] 2. Feasibility of the integrated photovoltaic receiver-optical-communication-sensing system on the target side

[0115] First, the feasibility of an integrated system for supporting photovoltaic receiver targets was verified. Figure 6 This demonstrates the changes in system performance across multiple dimensions under conditions of fixed Vpp or fixed bias current. Among these, Figure 6 (a) Figure 6 (b) Figure 6 (c) reflects the changes in communication, sensing and energy harvesting performance with Vpp0, respectively; Figure 6 (d) Figure 6 (e) and Figure 6(f) reflects the changes in communication, sensing, and energy harvesting performance with bias current. In this section, the distance between the transmitter and receiver is set to 1.45 m, and the LD beam is projected onto the photovoltaic and reflective film surfaces at a positive incident angle. AC power increases with increasing Vpp, while DC power increases with increasing bias current. When Vpp is small, the AC signal exhibits a low signal-to-noise ratio. When the bias current is small, the overall optical power is weak, and low-amplitude AC signals may fall into the LD's cutoff region, resulting in severe cutoff clipping distortion. Conversely, if Vpp or bias current is too large, high-amplitude AC signal peaks will enter the LD's nonlinear saturation region, causing saturation clipping distortion. Due to the aforementioned nonlinear clipping effect, both communication BER and ranging RMSE show a trend of first improving and then deteriorating. Since Vpp is mainly used to control the dynamic range of the AC signal, its impact on the overall energy harvesting performance is negligible. The DC component dominates energy harvesting, therefore, the energy increases monotonically with increasing bias current.

[0116] With the photovoltaic receiver at the receiving end, the integrated optical communication and sensing system demonstrated in this invention achieves a 7% forward error correction coding threshold (i.e., 3.8 × 10⁻⁶). -3 Under these conditions, a communication rate of 3.33 Mbps was achieved, while simultaneously achieving 3.7 W / m² with a peak energy harvest of approximately 0.37 mW. 2 The MLS-PAM envelope modulation waveform successfully broke the cascade constraint of low bandwidth photovoltaics on sampling rate, achieving a distance resolution of 6 cm and a minimum ranging RMSE close to 1 cm. These experimental results strongly validate the feasibility of the target-side photovoltaic receiver-optical-communication-sensing integrated system.

[0117] 3. Flexibility of MLS–PAM envelope modulation waveforms

[0118] Next, this invention will further verify the inherent flexibility of the MLS-PAM envelope modulation waveform. In this section, Vpp0 is set to 4.5 V, the bias current is fixed at 6.5 V, and other experimental conditions remain consistent with the previous section. Figure 7 (a) illustrates the performance variations of the integrated optical communication and sensing system under different peak amplitude ratios α. As a key control parameter for the AC waveform structure, α determines not only the absolute level interval of the PAM communication symbols but also the dynamic range of the MLS-PAM envelope modulation waveform. Under the condition that the average amplitude remains constant, increasing α will cause the extreme levels A1 and A... MThe signals converge. This compression of the signal space directly reduces the decision margin of envelope detection, leading to a decrease in communication performance. Simultaneously, a larger α can suppress amplitude fluctuations in the AC waveform, resulting in a smoother instantaneous power distribution that more closely approximates the ideal MLS waveform profile. This envelope smoothing effect helps form sharper correlation peaks, thereby improving ranging accuracy. Adjusting α is independent of the bias current and has negligible impact on energy harvesting performance. Therefore, as α increases, communication performance deteriorates, sensing performance improves, while energy harvesting performance remains essentially unchanged. Figure 7 (b) to 7(d) provide for Figure 7 Detailed observations of the marked points in (a) include typical received time-domain symbols captured by the information decoding module, cross-correlation curves in the sensing processing module, and IV characteristic curves of the energy harvesting module. These results strongly confirm the role of α in regulating the performance of the integrated optical-sensing-energy system.

[0119] 4. Performance evaluation under actual dynamic operating conditions

[0120] Finally, this section uses an α=0.2 configuration to evaluate the practical impact of dynamic physical conditions (including link distance and beam incident angle on the photovoltaic / reflective film) on the performance of the integrated optical-to-energy sensing system. In this subsection, the reference drive voltage Vpp0 is set to 4.5 V and the bias current is set to 7 V.

[0121] Figure 8 (a) illustrates the impact of link distance on the performance of the integrated optical-sensing and energy-sensing system when the LD beam is incident perpendicularly onto the target plane. As the propagation distance increases, the cross-sectional area of ​​the beam spot increases. At close range, the light energy is highly concentrated. Although the beam spot completely covers the effective photosensitive area of ​​the photovoltaic, the extremely high light intensity causes severe nonlinear distortion of the AC signal due to the carrier saturation effect of the photovoltaic material. Simultaneously, due to the small size of the central beam spot, only a limited amount of light power is captured by the reflective film, resulting in a very weak sensing echo signal reflected back to the transmitter. With a moderate increase in distance, the beam spot naturally diffuses, and the local light intensity decreases. This change not only alleviates the signal distortion caused by the photovoltaic saturation effect but also allows more light power to reach the reflective film, thereby enhancing the echo signal. However, if the link distance continues to increase, the macroscopic beam divergence effect will dominate. At this point, the light power captured by both the photovoltaic and the reflective film will suffer increasingly severe attenuation. Therefore, with increasing link distance, both BER and RMSE exhibit a trend of first decreasing and then increasing. In contrast, since DC power decreases monotonically with distance, the system's energy performance shows a continuous deterioration trend as the link distance increases.

[0122] Figure 8 (b) Further demonstrates the performance of the integrated optical-sensing and energy-sensing system when the beam is incident on the target plane at different angles. As the incident angle increases, the geometric projection effect reduces the effective illuminated area. Simultaneously, the oblique incidence effect exacerbates reflection loss and weakens photon penetration. This results in a decrease in effective incident power, causing performance indicators such as BER, RMSE, and EH to gradually deteriorate with increasing incident angle. Notably, the microprism reflective film deployed at the receiver exhibits excellent retroreflective capability. Even with relatively large angular deviations, the reflective film can redirect the beam back to the source direction, effectively preventing a sharp attenuation of the echo signal intensity. Compared to traditional diffuse or specular reflection, this characteristic highlights the advantages of retroreflection in adapting to changes in target orientation.

[0123] Finally, it should be noted that the above examples of the present invention are merely illustrative and not intended to limit the implementation of the invention. Although the applicant has described the present invention in detail with reference to preferred embodiments, those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A spectral-sensing-energy integrated system based on a target-side photovoltaic receiver, comprising a spectral signal generator for generating a spectral-sensing integrated digital signal, a digital-to-analog converter, a transmitter, a photovoltaic receiver, an information decoding module, an energy harvesting module, and a sensing processing module; the spectral signal generator, digital-to-analog converter, and transmitter are disposed at the transmitting end, and the photovoltaic receiver, information decoding module, and energy harvesting module are disposed at the receiving end; a power coupling unit is provided between the digital-to-analog converter and the transmitter; characterized in that: The sensing signal generating device includes an MLS modulation unit, a PAM modulation unit, and an envelope modulation unit. The MLS modulation unit generates an MLS sequence using a linear feedback shift register based on primitive polynomials. The PAM modulation unit modulates the input original signal using PAM to obtain a PAM sequence. The envelope modulation unit uses the PAM sequence as a slow envelope to perform envelope modulation on the MLS sequence, resulting in an MLS-PAM envelope-modulated AC signal. The MLS-PAM envelope-modulated AC signal is converted by a digital-to-analog converter and then enters a power coupling unit. The power coupling unit superimposes a DC component into the MLS-PAM envelope-modulated AC signal to complete AC / DC coupling. The power coupling unit outputs an analog electrical signal after AC / DC power coupling. The transmitter converts the analog electrical signal into an optical signal, which is simultaneously connected to the sensing processing module and the photovoltaic receiver. The photovoltaic receiver outputs the received optical signal as an electrical signal. The electrical signal is separated into DC and AC signals by a power separation unit. The DC signal is connected to the energy harvesting module, and the AC signal is connected to the information decoding module.

2. The integrated optical communication and energy sensing system based on a target-side photovoltaic receiver according to claim 1, characterized in that, The sensing processing module includes a light reflector, a photodiode, and an analog-to-digital converter (ADC). The reflector is located at the receiving end, and the photodiode and ADC are located at the transmitting end. The light beam reflected by the light reflector is converted into an analog electrical signal by the photodiode, and the analog electrical signal is converted into a digital signal by the ADC. The original MLS-PAM envelope modulation AC signal output by the sensing signal generator is connected to the upsampling module. The upsampling module upsamples the time-domain samples of the MLS-PAM envelope modulation AC signal generated by the sensing signal generator at the same upsampling rate. The output of the upsampling module and the output of the ADC are connected to the cross-correlation module. The cross-correlation module uses a time-domain cross-correlation method to perform distance measurement using the time-domain samples of the MLS-PAM envelope modulation AC signal generated by the sensing signal generator and the MLS-PAM envelope modulation AC signal converted by the ADC, thereby achieving sensing capability.

3. The integrated optical communication and energy sensing system based on a target-side photovoltaic receiver according to claim 2, characterized in that, The light reflector is a reflective film.

4. The integrated optical and electrical sensing system based on a target-side photovoltaic receiver according to claim 1, characterized in that, The information decoding module includes an analog-to-digital converter and a PAM demodulation module. The AC signal separated by the power separation unit is converted into a digital signal by the analog-to-digital converter, and the digital signal enters the PAM demodulation module. In the PAM demodulation module, the digital signal is processed by synchronization to obtain a discrete received signal sequence y[n]. PAM symbol decision is achieved by incoherent detection based on envelope statistics. The mean amplitude of the k-th symbol time interval is taken as the envelope estimate. As shown in the following formula, This refers to the number of discrete-time samples corresponding to each PAM symbol; assuming the original envelope amplitude corresponding to the training sequence is a. tr And its corresponding received signal envelope is estimated as z tr Then the least squares estimates of the equivalent channel gain g and baseline offset o , Calculated as Where X=[a tr [1] Based on the extracted channel feature parameters, the equivalent envelope amplitude of all received symbols is equalized according to the following formula. The amplitude of the received PAM symbol after equalization; Subsequently, the PAM sign decision is made according to the maximum likelihood criterion using the following formula. The amplitude of the finally recovered received PAM symbol; The final recovered PAM symbol is inversely mapped to a binary bit sequence to obtain the decoding result.

5. The integrated optical communication and energy sensing system based on a target-side photovoltaic receiver according to claim 1, characterized in that, The energy harvesting module provides power to various loads by separating the DC signal from the power separation unit.

6. The integrated optical communication and energy sensing system based on a target-side photovoltaic receiver according to claim 1, characterized in that, The power separation unit consists of an inductor and a capacitor.

7. A method for designing the transmitted waveform of an integrated optical-to-energy sensing system, wherein the integrated optical-to-energy sensing system is the integrated optical-to-energy sensing system based on a target-side photovoltaic receiver as described in claim 1, characterized in that: Follow these steps: 1) First, generate an MLS sequence, and then simultaneously perform PAM modulation on the original signal to obtain a PAM sequence; 2) Using a PAM sequence as a slow envelope to perform envelope modulation on a fast MLS sequence, an MLS-PAM envelope-modulated AC signal is obtained; 3) The MLS-PAM envelope modulation AC signal is converted from digital to analog. The normalized MLS-PAM envelope modulation AC signal is mapped to the quantized output level according to the preset inter-peak voltage. Then, a DC component is superimposed on the MLS-PAM envelope modulation AC signal to complete AC-DC coupling, thereby generating an analog electrical signal for driving the transmitter. 4) The analog electrical signal is converted into an optical signal by the transmitter. The optical signal is the transmitted waveform of the optical communication and sensing integrated system. The transmitted waveform contains an AC component and a DC component. The AC component carries communication and sensing information, while the DC component provides the main energy source. The transmitted waveform is processed accordingly to realize information decoding, sensing processing and energy harvesting.

8. The method for designing the emission waveform of an integrated optical communication and sensing system according to claim 7, characterized in that: The MLS sequence is generated using a linear feedback shift register based on primitive polynomials.

9. The method for designing the transmission waveform of an integrated optical communication and sensing system according to claim 7, characterized in that: Let m[l] be the bipolar MLS sequence of length L, where l∈{0,1,…,L-1}; and let m[l] be the amplitude set of the unipolar PAM sequence of order M. , The average level amplitude is ; The peak amplitude ratio α is defined as the ratio of the minimum to the maximum value in the amplitude set of a PAM sequence, expressed as: The amplitude set of a PAM sequence is represented as follows: Let i be the level index corresponding to the k-th PAM symbol in the PAM sequence. k , Then the envelope symbol amplitude sequence is defined as Each PAM symbol in the PAM sequence lasts for N seconds. rep If there are N MLS base sequence periods, then the number of discrete-time samples corresponding to each PAM symbol is N. sps =N rep L; Let the set of discrete-time indices corresponding to the k-th MLS-PAM envelope modulation symbol be denoted as The AC waveform within the k-th symbol interval is represented as follows: Where m[·] is periodically extended with period 𝐿; the entire MLS-PAM envelope modulation AC sequence is in This represents the floor operator.

10. The method for designing the emission waveform of an integrated optical communication and sensing system according to claim 9, characterized in that: The peak amplitude ratio α is set as an adjustable parameter to achieve a continuously adjustable tradeoff between communication reliability and perception robustness; It also works in conjunction with the DC component configuration to achieve a combined compromise in the performance of communication, sensing, and energy harvesting.

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