Detection system and method for detecting motion of an object

Abstract

The invention relates to a detection system for detecting a motion of an object by utilizing at least two devices adapted to transmit and receive radio frequency signals. The system (110) comprises a control unit (111) for controlling the at least two devices such that at least one of the at least two devices is a transmitting device (120) transmitting a radio frequency signal having a transmission signal frequency and such that at least one of the at least two devices is a receiving device (130) receiving a radio frequency signal indicative of a reflection of the transmitted radio frequency signal of the object, a signal frequency providing unit (112) for providing the transmission signal frequency at which the radio frequency signal has been transmitted, and a detection unit (113) for detecting the motion of the object by performing passive Doppler sensing based on the received radio frequency signal and the provided transmission signal frequency.

Description

Technical Field

[0001] This invention relates to a detection system, method, and computer program for detecting the motion of an object. Background Technology

[0002] Today, the use of radio frequency (RF) sensing to detect motion in networks of multiple devices used in home and office applications is gaining increasing attention. The basic idea of ​​RF sensing is that network devices (including, for example, lighting fixtures, smart switches, smart application devices, etc.) form a radio network by frequently exchanging messages, the amplitude of which is then monitored and compared, for example, with a baseline signal to determine changes in the network device's environment. These changes can be interpreted, for example, as human movement, inactivity, or changes in the state of objects (such as a door opening or closing). However, monitoring the amplitude of the exchanged messages is a complex and error-prone process, often leading to false alarms or false negatives, such as misdetecting people in a room. Because RF sensing is frequently used to control the functions of network devices (e.g., lighting), inaccurate RF sensing results cause interference in network device applications and are highly undesirable. Therefore, providing networks of network devices with motion detection systems that allow for higher accuracy would be advantageous. Summary of the Invention

[0003] One object of the present invention is to provide a detection system, a method, and a computer program that allow for improved detection of motion of objects in the environment of the detection system.

[0004] In a first aspect of the invention, a detection system is provided for detecting motion of an object by utilizing at least two devices suitable for transmitting and receiving radio frequency signals, wherein the system comprises a) a control unit for controlling the at least two devices such that at least one of the at least two devices is a transmitting device for transmitting a radio frequency signal having a transmission signal frequency, and such that at least one of the at least two devices is a receiving device for receiving a radio frequency signal indicating the reflection of the radio frequency signal transmitted by the object; b) a signal frequency providing unit for providing a transmission signal frequency at which the radio frequency signal has been transmitted; and c) a detection unit for detecting motion of the object by performing passive Doppler sensing based on the received radio frequency signal and the provided transmission signal frequency.

[0005] Because the detection unit is adapted to detect motion of an object by performing passive Doppler sensing based on a received radio frequency signal transmitted by one of the at least two devices and received by the other of the at least two devices, and the frequency of the provided transmitted signal, passive Doppler sensing can be performed based on knowledge of the transmitted signal frequency; that is, it is not necessary to determine the transmitted signal frequency based on the received radio frequency signal itself. This allows for high-precision motion detection using radio frequency signals. Therefore, the detection system allows for improved motion detection.

[0006] A detection system for detecting the motion of an object utilizes at least two devices adapted to transmit and receive radio frequency signals. An object can refer to, for example, a living organism or a physical object, particularly a moving one. A living organism can refer to a human or animal; and an object can refer to any object, such as a robotic appliance or a door. In a preferred embodiment, the detection system is adapted to detect the motion of a human near at least two devices. Generally, simple objects (such as a robotic cleaner in a room) provide simple Doppler signals, i.e., the object has only one velocity. More complex objects or organisms include more complex Doppler signals because different parts of a complex object or organism typically move at different velocities in different directions. These more complex Doppler signals can also be considered Doppler features and allow for easy differentiation between different objects and their behaviors.

[0007] Preferably, the two devices are network devices that are part of a network formed by at least these two network devices. However, the network may also include more than two network devices, in which case the detection system may utilize all or only a portion of the network devices as at least two network devices for performing motion detection. A network of network devices is typically formed by communication between the network devices, where the communication between the network devices can be based on any known communication protocol, such as WiFi, ZigBee, Bluetooth, etc. Therefore, it is preferred that the two devices of the network devices include a network device communication unit, wherein the network device communication unit is adapted to transmit and receive wireless signals (especially radio frequency signals) and / or wired signals. For example, the network device communication unit may include a network device transceiver for receiving and transmitting radio frequency signals, or a transmitter for transmitting radio frequency signals and a receiver for receiving radio frequency signals. In particular, the at least two devices may be smart network devices, i.e., any device that includes a communication unit for transmitting and receiving wireless signals (especially radio frequency signals), but which otherwise implements the functions of a corresponding conventional device. For example, such a smart network device may be a smart home device, in which case the corresponding conventional function may be the function of a conventional home device (such as lighting equipment or household appliances). In a preferred embodiment, the at least two devices refer to a smart optical module, a smart plug, or a smart switch.

[0008] The detection system can be part of a network comprising at least two devices, for example, provided as software or hardware in one of the network devices or distributed across multiple network devices communicating with each other. However, the detection system can also be a standalone system or part of one or more devices that are not part of the network but can communicate with at least one device that is preferably part of the network. For example, the detection system can be provided as software running on a handheld computing device or in another network, which can communicate with the network or at least one device that is preferably part of the network, for example, via a gateway. If the at least two devices are not part of the network, the detection system can be provided as part of one of the two devices (e.g., as software or hardware provided in one of the at least two devices) and can be adapted to communicate with two of the at least two devices via wired or wireless communication protocols. Furthermore, also in this case, the detection system can be a standalone system provided outside of the at least two devices, for example, on a handheld computing device, a network solution, or any other computing device adapted to communicate with the at least two devices.

[0009] The control unit is adapted to control at least two devices. Furthermore, if more than two devices are provided, for example, as part of a network of multiple network devices, the control unit may be adapted to control all or some of these devices. Generally, the control unit may be adapted to control at least two devices by sending control commands to at least two devices, which, when executed by the at least two devices, result in providing the functions of the at least two devices indicated by the control commands.

[0010] Specifically, the control unit is adapted to control at least one of at least two devices, enabling it to act as a transmitting device for transmitting radio frequency (RF) signals with a transmission signal frequency. The transmission signal frequency can refer to a single frequency or a frequency range. Furthermore, the control unit can also be adapted to control sensing devices, enabling the transmission of more than one RF signal, each with a different sensing signal frequency. Specifically, the transmitted RF signals are transmitted at a transmission signal frequency within a predetermined signal frequency range—for example, within the signal frequency range defined by the 2.4 GHz ZigBee standard, or within the frequency range of WiFi standard communication, which is approximately 2.5 GHz, 50 GHz, or even 60 GHz. Within such a predefined frequency range, the control unit can be adapted to control the transmitting device, enabling it to transmit RF signals with a specific transmission signal frequency selected from the available range. However, the RF signals with transmission signal frequencies transmitted by the transmitting device can also be predetermined, for example, by the hardware of the transmitting device or by rules provided within the transmitting device, such that in this case, the control unit controls the transmitting device solely by causing it to transmit RF signals with transmission signal frequencies indicated by the transmitting device itself. If the at least two devices refer to network devices, it is preferred that the transmitting network device utilizes its network device communication unit, particularly the transmitter of the network device communication unit, for transmitting radio frequency signals having a transmission signal frequency. However, if the transmitting network device includes a network device communication unit applicable only to wired network communication or only to network communication in a range other than the radio frequency range, the network device may include additional units for transmitting radio frequency signals. In a preferred embodiment, the radio frequency signal transmitted by the transmitting device refers to a communication signal within the network, i.e., a signal used for communication between network devices.

[0011] The control unit is also adapted to control at least one of the at least two devices to act as a receiving device for receiving radio frequency signals, which indicate the reflection of radio frequency signals transmitted by an object. Specifically, the control unit may be adapted to control the receiving device such that it monitors signals received within a predetermined frequency range in which reflection of transmitted radio frequency signals (particularly when reflected by an object) is expected. Preferably, if the receiving device refers to a network device, the receiving device utilizes a network device communication unit (particularly a receiver of the network device communication unit) to receive the reflected radio frequency signals. However, the receiving device may also include a dedicated receiving unit that is not part of the network device communication unit used to receive the reflected radio frequency signals. The transmitting device and the receiving device generally do not refer to the same device among the at least two devices. Therefore, if only two devices are used, one of the two devices is the transmitting device and the other of the two devices is the receiving device. In particular, the at least two devices are independent of each other and are not provided in the same location. Preferably, the transmitting device and the receiving device are provided with a specific predetermined distance from each other, wherein the distance is preferably greater than 1 m, more preferably greater than 2 m. Therefore, in a preferred embodiment, the control unit's control of at least two devices includes selecting which of the at least two devices will act as a transmitting device and which of the at least two devices will act as a receiving device. Specifically, if more than two devices (i.e., multiple devices) are provided, the selection may include selecting one or more devices to act as a transmitting device and selecting one or more devices to act as a receiving device based on, for example, the location of the multiple devices, the characteristics of the multiple devices (e.g., whether the devices include radio frequency transmitting and / or receiving units), and / or the availability of the devices. Thus, the control unit is generally adapted to control the formation of device pairs, where one device in such a device pair is considered the transmitting device of the device pair, and the other device is considered the receiving device of the device pair. However, overlapping pairs can also be considered, such that, for example, one device acts as a transmitting device in one device pair and a receiving device in another device pair, or that the transmitting device is the same for different device pairs, but the receiving device is different for each pair. In the last case, all device pairs including the same transmitting device can be considered to form a device group. Device pairs or groups can be distinguished by differentiating the signals transmitted by the transmitting devices of each device pair or group. For example, the control unit may be adapted to control each transmitting device in a pair or group of devices to transmit radio frequency signals at different times or by utilizing different transmission signal frequencies.

[0012] Generally, the control unit can be adapted to control the transmitting and / or receiving devices in a scanning mode, wherein the scanning mode allows for directional scanning of at least a portion of the sensing area. Preferably, in the scanning mode, the control unit is adapted to control the sensing and / or receiving devices to perform directional transmission and / or reception. For example, using known directional methods, the sensing devices can be controlled to subsequently direct radio frequency signals to different areas of a room to systematically scan for the presence of motion in the room. However, in other embodiments, the control unit can be adapted to control the transmitting and / or receiving devices to perform non-directional transmission, particularly transmitting and / or receiving signals simultaneously in / from multiple directions.

[0013] Furthermore, the detection system includes a signal frequency providing unit for providing a transmission signal frequency at which the radio frequency signal has been transmitted. The signal frequency providing unit may be, for example, a storage unit storing the transmission signal frequency (which is, for example, a predetermined transmission signal frequency), or it may be connected to a storage unit storing the transmission signal frequency. The signal frequency providing unit may also be adapted as a receiving unit for receiving the transmission signal frequency, for example, from a control unit controlling the transmitting device or from the transmitting device itself, and then providing the received transmission signal frequency. For example, the transmitting device may be adapted to monitor and provide the transmission signal frequency of the radio frequency signal it transmits, and provide the transmission signal frequency to the signal frequency providing unit to provide the transmission signal frequency. In particular, the signal frequency providing unit may be part of the transmitting device and may then be adapted to communicate with the detection unit to provide the transmission signal frequency. Generally, for all embodiments, if the control unit controls more than one transmitting device, the signal frequency providing unit may be adapted to provide the transmission signal frequency for each transmitting device, particularly when the transmitting devices use different transmission signal frequencies.

[0014] The detection unit is then adapted to detect the motion of an object by performing passive Doppler sensing based on the received radio frequency signal and the provided transmission signal frequency. Typically, passive Doppler sensing involves performing Doppler analysis on the received signal, where the receiver of the signal differs from the transmitter, i.e., the transmitter is provided at a different location than the receiver. In this invention, passive Doppler sensing is based not only on the received radio frequency signal but also on knowledge of the transmission signal frequency, i.e., knowledge of the transmitted radio frequency signal. This has the advantage that the complex and error-prone analysis of the received radio frequency signal used to extract the transmission signal frequency from the received radio frequency signal can be omitted. In particular, known Doppler analysis can be performed based on the received radio frequency signal and the provided transmission signal frequency. Doppler analysis is based on the principle that the frequency of a wave reflected from a moving object will change depending on the speed of the moving object. Therefore, by providing the detection unit with the received radio frequency signal and the provided transmission signal frequency, the detection unit can determine whether the received radio frequency signal includes at least one signal portion having a frequency offset relative to the provided transmission signal frequency, which indicates the presence of motion of the object. To detect the motion of an object based on the received radio frequency signal and the frequency of the transmitted signal, the detection unit can be adapted to extract the frequency shift (i.e., perform Doppler analysis) from the received radio frequency signal indicating the motion of the object using any known software or hardware solution, such as signal frequency analysis methods, signal mixing methods, etc. Furthermore, the detection unit is preferably adapted to distinguish between living organisms and simple objects, for example, based on the complexity of the Doppler analysis results. For example, for a simple object, the result typically includes only one velocity, while for a living organism, the result is expected to result in more than one definite velocity, i.e., velocity characteristics. The detection unit can then be adapted to further analyze the velocity characteristics, for example, to determine the identity of the organism, average velocity, respiratory movements, direction of movement, etc., based on the velocity characteristics. For example, the detection unit can be adapted to determine whether more than one Doppler frequency shift can be detected in the spectrum of the received signal, and can determine that this indicates the presence of a living organism.

[0015] In one embodiment, the control unit is further adapted to: control the at least two devices such that each of the at least two devices acts as a transmitting device, each transmitting a radio frequency signal with a different signal frequency; and control the at least two devices such that each device acts as a receiving device to receive a reflection of a radio frequency signal transmitted by an object corresponding to the radio frequency signal transmitted by the corresponding other device, wherein the detection unit is adapted to perform passive Doppler sensing based on the received radio frequency signal. Therefore, in this embodiment, the control unit is adapted to control devices available as transmitting and receiving devices, such that device pairs or groups are formed as overlapping device pairs or groups. Specifically, in this embodiment, a device group can be defined for each device capable of acting as a transmitting device, wherein the device group then includes the device acting as a transmitting device and all other devices capable of receiving the reflected radio frequency signal from the transmitting device as receiving devices. Thus, a transmitting device capable of receiving a radio frequency signal can also act as a transmitting device in its own group and a receiving device in other groups. The detection unit is then adapted to perform passive Doppler sensing, i.e., Doppler analysis, based on the received radio frequency signal. For example, the detection device can be adapted to perform passive Doppler sensing for each group independent of each other, preferably based on the results of Doppler analysis of all pairs in that group. However, the detection unit can also be adapted to perform passive Doppler sensing using radio frequency signals received from different groups. For example, the detection unit can be adapted to compare the results of passive Doppler sensing performed by different pairs within a group or by different groups, and apply logical rules to the comparison to determine whether the result actually relates to the movement of an object (especially a human) or is caused by other reasons (e.g., noise, vibration of the device itself, etc.). In particular, to reduce the impact of vibration, for example, caused by processes within the device or in the device environment, on motion detection, it is preferable that the detection unit is adapted to compare the passive Doppler sensing results of all device pairs, where the receiving device of one pair is the transmitting device of another pair, and vice versa. Thus, passive Doppler sensing results preferably based on different transmitted signal frequencies and corresponding to substantially the same detection area (in particular, the area between the two devices forming two device pairs) can be compared, and logical rules can be applied to the comparison to determine whether the detection result is caused by the movement of an object. For example, if the passive Doppler sensing result indicates that the object is moving at a different speed, the detection result is likely not caused by a moving object, but rather likely caused by, for example, noise.

[0016] In one embodiment, the control unit is adapted to control the transmitting device to detect radio frequency (RF) signals generated by reflections of transmitted RF signals emitted by the device itself, and wherein the detection unit is adapted to monitor the detected RF signals and further detect motion of an object based on the monitored RF signals. Specifically, the transmitting device is adapted to monitor RF signals generated by reflections of transmitted RF signals emitted by the device itself that are not reflected by the object. The signal frequency providing unit may then be adapted to provide the detected RF signals to the detection unit. The detection unit is then adapted to monitor the detected RF signals detected by the transmitting device. Monitoring may include, for example, determining temporal variations in the detected RF signals. In particular, sudden changes (i.e., within a predetermined short time range) may indicate events that should be considered when detecting motion of an object. Preferably, the detection unit is adapted to monitor the detected RF signals by monitoring frequencies occurring in the detected RF signals. In particular, preferably, the detection unit identifies narrow frequency bands in the spectrum of the detected RF signals, i.e., signals within a frequency range smaller than a predetermined range, preferably, according to the Doppler relationship, this range refers to velocity variations of 20 cm / s, more preferably 10 cm / s. Such narrow frequencies are typically the result of vibrations of the transmitting device itself or the environment surrounding the transmitting device. Therefore, when the application of the detection system is intended to detect the movement of an object (preferably a human), it is preferable that the detection unit is adapted to filter out the identified narrow frequency range in the received radio frequency signal using the identified narrow frequency range, since it can be anticipated that the received radio frequency signal also includes frequencies in the identified narrow band, i.e., frequencies that indicate excitation in the spectrum, however, this excitation is likely not caused by the movement of the object. The detection unit is then adapted to determine the movement of the object by performing passive Doppler sensing based on the filtered received radio frequency signal.

[0017] In one embodiment, the detection unit is adapted to: determine an excitation within a frequency range in the spectrum of the received radio frequency signal, wherein the excitation is substantially constant over a predetermined time period; and perform passive Doppler sensing based on the received radio frequency signal by filtering out the frequency range in the spectrum of the received radio frequency signal. Since the motion of an object (especially a human) can be expected to be non-constant over long periods, an excitation within a frequency range that is substantially constant over a long period is likely not caused by the object's movement, but rather by, for example, vibrations in the environment or noise. Depending on the application of the detection system, it is preferable, for example, to determine the predetermined time period based on the timescale of the expected motion of the object to be detected. For example, if the object whose motion should be detected is a human, the predetermined time period could refer to several minutes (e.g., 3 or 4 minutes), since it is highly unlikely that the motion of a human, for example, in a small room, would remain unchanged during such a time period. Therefore, the substantially constant excitation observed in the received radio frequency signal—i.e., the excitation that is constant over a predetermined range of more than several minutes—is likely not caused by the object's motion and can be filtered out. In this context, the term "substantially constant" refers to an excitation occurring at the same frequency or frequency range during the predetermined time period, with an amplitude not less than a noise threshold.

[0018] In a preferred embodiment, the detection unit may be adapted to determine the occurrence of an excitation within a frequency range narrower than a predetermined frequency range, and to perform passive Doppler sensing based on the received radio frequency signal by filtering out the narrow frequency range in the spectrum of the received radio frequency signal. Specifically, if the motion of the object to be detected refers to human motion, the excitation in the frequency range of the received radio frequency signal caused by a moving human can be expected to be broadened or obscured over a wide frequency range, for example, because different parts of the human body move at different speeds, such as arms and legs moving at speeds different from the human torso. Therefore, the excitation of the received radio frequency signal occurring within a very narrow frequency range is likely not caused by the motion of a human or actually any living organism, but rather by vibrations of mechanical components in the environment of the transmitting or receiving device. Preferably, according to the Doppler relationship, the predetermined frequency range refers to a velocity variation of 20 cm / s, more preferably 10 cm / s. Therefore, by filtering out the excitation—which is likely caused by a motion source (which should not be detected relative to the application of the detection system) or refers to any kind of noise in the environment of the detection system—the accuracy of motion detection can be improved, especially considering the specific application of the detection system.

[0019] In one embodiment, the detection unit is adapted to determine the I-channel and Q-channel based on the received radio frequency signal, and to perform passive Doppler sensing based on the I-channel and Q-channel.

[0020] Specifically, the detection unit can determine the I-channel by multiplying the received radio frequency signal by a signal including the frequency of the provided transmitted signal, and the Q-channel by multiplying the received radio frequency signal again by a signal including the frequency of the provided transmitted signal (where one of these two signals is phase-shifted, for example, by 90°), thus determining the I-channel and Q-channel. Preferably, the detection unit is then adapted to construct a complex signal from the Q-channel and the I-channel, where the I-channel refers to the imaginary part of the complex signal and the Q-channel refers to the real part of the complex signal. Then, preferably, the motion of the object is detected using the complex signal. Specifically, preferably, the spectrum of the complex signal is determined by the detection unit, for example, by performing a Fourier transform of the complex signal and detecting the motion of the object based on the spectrum of the complex signal. For example, such a constructed complex signal can show positive and negative frequencies in the spectrum, where the excitation in the positive frequencies indicates motion with a motion component toward the receiving device, while the negative frequencies indicate motion with a motion component away from the receiving device. However, the exact relationship between the motion and the determined frequencies depends on the phase shift used to construct the Q-channel. Generally, independent of the precise phase shift used, the construction of the complex signal allows for the precise determination not only of the object's velocity but also, at least relative to the receiving device, of the object's direction of motion. Furthermore, in complex signals (especially in the spectrum of complex signals), motion not caused by an object (especially a human) but by, for example, vibrations in the device environment can be distinguished even more clearly. Specifically, noise caused by vibrations in the environment results in excitation in the spectrum of complex signals at both positive and negative frequencies, since vibrations include both motion components. In contrast, the general movement of an object (like a human) involves a more fixed direction and therefore results in excitation only at either positive or negative frequencies. Therefore, it is preferable that the detection unit is adapted to identify excitations in the spectrum of complex signals caused by vibrations, for example, by filtering the frequency range in which the excitation occurs from the received radio frequency signal since the excitation exists at both positive and negative frequencies, and by performing Doppler analysis based on the filtered received radio frequency signal. In this case, it should be noted that the breathing movements of a person who is not moving in other ways can also be considered vibrations and can therefore be detected by monitoring positive and negative frequencies using the methods described above.

[0021] In one embodiment, the control unit is further adapted to control the transmitting device to transmit an additional radio frequency (RF) signal having a frequency different from the transmitted signal frequency, and to control the receiving device to receive an additional RF signal generated by the reflection of the additional RF signal from the object, wherein the detection unit is further adapted to perform passive Doppler sensing based on the additional received RF signal. Therefore, in this embodiment, each transmitting device controlled by the control unit is adapted to transmit two RF signals with different transmitted signal frequencies, such that each receiving device controlled by the control unit can receive two RF signals reflected from the object based on the two different transmitted RF signals. Since the Doppler effect (i.e., the frequency shift due to motion in the reflected RF signal) is frequency-dependent for a moving object, different frequency shifts can be detected in the two different received RF signals according to the principle of the Doppler effect. Typically, the transmitting signal frequency providing unit in this case is adapted to provide two transmitting signal frequencies to the detection unit.

[0022] In a preferred embodiment, the detection unit is adapted to perform passive Doppler sensing based on the additional received radio frequency (RF) signal by comparing it with the received RF signal. Preferably, this comparison refers to subtracting the additional received RF signal from the received RF signal in the frequency domain, wherein the detection unit is adapted to detect motion based on the signal obtained by the subtraction. Typically, due to the principle of the Doppler effect, the actual motion of an object results in excitations in different frequency ranges of the two different received RF signals, while noise caused by, for example, vibrations in the device environment, typically results in excitations in a frequency range independent of the transmitted signal frequency. Therefore, by subtracting the two received RF signals from each other, frequency excitations located in the same frequency range can be removed, and the detection unit can then apply Doppler analysis to the signal obtained by the subtraction, which does not contain excitations in the frequency range caused by noise. In another preferred embodiment, the detection unit can be adapted to perform passive Doppler sensing by performing Doppler analysis on two independent received RF signals using the corresponding transmitted signal frequency provided for each signal. The detection unit can then be adapted to compare the results of the two independent Doppler analyses to perform passive Doppler sensing. For example, if a real moving object (e.g., a human) is present, each of two independent Doppler analyses will result in a substantially identical determined velocity for that object. However, if the result of the Doppler analysis is caused by noise, it is likely that different velocities will be determined in each independent Doppler analysis, indicating that the corresponding signal is not caused by a real moving object, but possibly by noise or vibration. Therefore, the detection unit can be adapted to apply logical rules to the comparison of two results from two independent Doppler analyses to perform passive Doppler sensing. The logical rules can be predetermined, or they can be learned rules, for example, learned by the detection unit during a training phase, where the detection unit faces different environmental situations, and the desired result of passive Doppler sensing is also provided to the detection unit as input (e.g., provided by a user), and the detection unit is then adapted to use known machine learning algorithms to learn logical rules that can be applied to achieve the desired result of passive Doppler sensing. Therefore, it is preferable that the comparison refers to performing Doppler analysis on two signals that are independent of each other, and comparing the results of the Doppler analysis in terms of consistency.

[0023] In one embodiment, performing Doppler analysis includes applying a threshold filter to the received radio frequency (RF) signal in the frequency domain. Specifically, the received RF signal can be provided in the frequency domain, for example, by applying a Fast Fourier Transform (FFT). In the frequency domain, the received RF signal can optionally be further modified, for example, by squaring the received RF signal. The threshold, then, can be predetermined, for example, based on calibration measurements or experience, and is provided to the threshold filter. The threshold filter then increases all signal portions of the received RF signal in the frequency domain that are above the predetermined threshold and decreases all signal portions of the received RF signal that are outside the threshold. The decrease and increase can be based on predetermined values, respectively, which can refer to an applied function (e.g., a scaling function) depending on the difference between the signal portion and the threshold, etc. Motion can then be determined based on the filtered received RF signal. This filtering allows for more accurate determination of motion.

[0024] In one embodiment, the control unit is adapted to control the transmitting device to utilize two radio frequency signals with different transmitted signal frequencies (e.g., 2.4 GHz and 5.8 GHz). In this embodiment, the execution of Doppler sensing may include determining a confidence vector of motion; for example, the detection unit may include dedicated logic containing the confidence vector of motion. Each component of this vector describes the probability of motion relative to the receiving device within a velocity range. Preferably, the confidence vector is updated every 100 ms by analyzing the received radio frequency signals originating from two different transmitted signals (here, from 2.4 GHz and 5.8 GHz frequency signals). For both transmitted signal frequencies, the detection unit may be adapted to perform the following as part of a Doppler analysis: A low-pass filter with a predetermined cutoff frequency of, for example, 120 Hz is provided to each received radio frequency signal, which is then sampled at a predetermined sampling frequency (e.g., 240 Hz). The detection unit is then adapted to calculate a short fast Fourier transform (SFT) that produces a spectrum every 100 ms using the last 256 received samples. The spectrum is then a set of domains, where each domain contains a frequency range that can be mapped to a relative velocity range, which can be mapped to the confidence vector of motion. Therefore, the detection unit can be adapted to subsequently use the spectrum to construct a power spectrum by squaring the amplitude of the spectrum. For each domain in the power spectrum whose value is higher than a selected threshold, the corresponding component of the confidence vector can then be increased. For each domain in the power spectrum whose value is lower than the selected threshold, the corresponding component of the confidence vector can then be decreased. The detection unit is then adapted to determine, after the confidence vector has been updated, that motion is detected when the maximum value of all components exceeds 0.5; otherwise, the detection unit is adapted to determine that no motion exists.

[0025] In one embodiment, the detection unit is further adapted to perform radio frequency (RF) sensing based on the amplitude of the received signal, wherein the detection unit is adapted to perform passive Doppler sensing as a substitute for or supplement to RF sensing, based on a sensing result determined for at least one of at least two devices and / or based on the device state of at least one of at least two devices. Specifically, the detection unit may be adapted to perform RF sensing using known RF algorithms, such as those described, for example, in WO 2020 / 043606A1. Preferably, the detection unit is adapted to apply predetermined logical rules to determine, based on the results of RF sensing, whether passive Doppler sensing should be performed, for example, within a predetermined time period, as a substitute for or supplement to RF sensing. The predetermined logical rules may be applicable to the system application and may depend on the circumstances. For example, the detection unit may be adapted to perform RF sensing normally, and if the detection unit determines that the results of RF sensing may be unreliable (i.e., may not meet predetermined quality standards), the detection unit may be adapted to additionally perform passive Doppler sensing (e.g., as described in the embodiments above) to verify the results of RF sensing. In another example, if at least one device is in sleep mode, for example when people are not expected to be in the area during the night, the detection unit may be adapted to periodically apply passive Doppler sensing (instead of radio frequency sensing) to detect motion in the area, wherein if passive Doppler sensing detects motion, the detection unit may be adapted to additionally initiate the execution of radio frequency sensing, for example by waking up the device, to obtain more information about the determined motion in the area.

[0026] In one embodiment, two pairs of devices are used to detect motion, wherein a control unit is adapted to control each pair of devices such that each pair includes at least a transmitting device and a receiving device, wherein the control unit is also adapted to control the transmitting and receiving devices such that radio frequency signals of different frequencies are used by the two pairs of devices for passive Doppler sensing, wherein a detection unit is adapted to independently perform passive Doppler sensing for each pair of devices and further detect motion based on a comparison of the obtained detection results. In particular, it is preferred that the detected motion refers to minute movements or vibrations of an object. In this context, minute movements are defined as movements of small size and / or small duration, where “small” in this context means a size less than 10 cm and a duration less than 1 minute. For example, minute movements can refer to periodic movements of the human body, such as breathing movements or heartbeat movements. Therefore, in this embodiment, it is preferred that the system is specifically tuned such that the motion of the object refers to the detected vibrational movement or minute movements of the object. In many of the above embodiments, it is preferred to eliminate these vibrations or minute movements from the motion detection of the object. However, in other applications, it is advantageous to specifically detect vibrations, for example, in the case of machine monitoring for monitoring machine function, where the vibration of the machine typically indicates changes in state within the machine. Therefore, the principles for vibration removal discussed above can now also be applied to adapt the detection unit to the vibration or minute movement of the object being detected.

[0027] In one embodiment, the results of motion detection are used to control the functions of a device. For example, preferably, the device refers to a lighting device, and the lighting function is controlled based on motion detection. However, other functions may also be additionally or alternatively controlled by the results of motion detection performed by the system.

[0028] In one aspect of the invention, a detection method is provided for detecting motion of an object by utilizing at least two devices suitable for transmitting and receiving radio frequency signals, wherein the method comprises a) controlling the at least two devices such that at least one of the at least two devices is a transmitting device transmitting a radio frequency signal having a transmission signal frequency, and such that at least one of the at least two devices is a receiving device receiving a radio frequency signal indicating the reflection of the radio frequency signal transmitted by the object; b) providing a transmission signal frequency at which the radio frequency signal has been transmitted; and c) detecting motion of the object by performing passive Doppler sensing based on the received radio frequency signal and the provided transmission signal frequency.

[0029] In another aspect of the invention, a computer program product for detecting motion is provided, wherein the computer program product includes program code means that causes the detection system according to claim 1 to perform the detection method according to claim 14.

[0030] It should be understood that the detection system, the method, and the computer program described above have similar and / or identical preferred embodiments, particularly those defined in the dependent claims.

[0031] It should be understood that the preferred embodiments of the present invention may also be any combination of the dependent claims or the above embodiments with the corresponding independent claims.

[0032] These and other aspects of the invention will become clear and explained with reference to the embodiments described below. Attached Figure Description

[0033] In the following figures:

[0034] Figure 1 Two radio frequency (RF) devices used in a detection system for controlling RF devices are illustrated schematically and exemplaryly.

[0035] Figure 2 A detection method for detecting the motion of an object is illustrated schematically and exemplary. Detailed Implementation

[0036] Figure 1 Two radio frequency (RF) devices 120 and 130 and a detection system 110 are illustrated schematically and exemplary. Preferably, the RF devices 120 and 130 are part of a network formed by at least two RF devices 120 and 130, wherein optionally, the network includes... Figure 1 An additional radio frequency device, not shown, may also be controlled by the detection system 110. However, for better overview, the following discussion will focus only on... Figure 1 The two radio frequency devices 120 and 130 shown illustrate the principles of the invention, and these explained principles can then be applied to systems comprising more than two radio frequency devices 120 and 130. It is particularly noted here that the two radio frequency devices 120 and 130 refer to completely different devices and are not located in the same position, but are provided with a distance between them preferably greater than 1 m, more preferably greater than 3 m.

[0037] The detection system 110 may be a standalone system that communicates with at least two radio frequency devices 120, 130; or it may be provided as part of one of the at least two radio frequency devices 120, 130, for example, provided within a housing or as part of the software and / or hardware provided in one of the at least two devices 120, 130. Preferably, if the at least two radio frequency devices 120, 130 are part of a network, the detection system is also part of the network (e.g., as part of one of the devices in the network) or distributed across multiple devices in the network. In this case, communication between the detection system 110 and the at least two devices 120, 130, and optionally other network devices may be part of general network communication, i.e., messages to and from the detection system 110 are sent as part of a communication protocol used by the network.

[0038] The detection system 110 includes a control unit 111, a signal frequency providing unit 112, and a detection unit 113. The control unit 111 is adapted to control radio frequency devices 120 and 130. Specifically, the control unit 111 is adapted to control the radio frequency device 120 as a transmitting device that transmits a radio frequency signal 121 having a transmission signal frequency. Furthermore, the control unit 111 is adapted to control the radio frequency device 130 as a receiving device that receives a radio frequency signal 131, which is the result of reflection from the radio frequency signal 121 of an object (in this case, a person 140 moving in direction 141). Due to the Doppler effect, the reflected signal 131 received by the radio frequency device 130 includes information about the movement 141 of the person 140; specifically, the signal 131 reflected from the person 140 undergoes a frequency shift relative to the transmitted radio frequency signal 121. Preferably, the transmitted radio frequency signal 121 is also transmitted as part of general network communication, i.e., refers to general network communication signals that include, for example, messages for another network device. However, the transmitted radio frequency signal 121 may also be a dedicated signal transmitted solely for motion detection.

[0039] The signal frequency providing unit 112 is adapted to provide the transmission signal frequency of the transmitted radio frequency signal 121. Specifically, the detection system 110 communicates with the radio frequency device 120, which acts as a transmitting device, such that the radio frequency device 120 can provide information about the transmission signal frequency to the signal frequency providing unit 112. For example, the signal frequency providing unit 112 may be adapted to initiate communication of the radio frequency device 120 preferably via a network communication signal containing the transmission signal frequency. However, in other embodiments, the radio frequency device 120, acting as a transmitting device, may be adapted to provide the transmission signal frequency to the signal frequency providing unit 112 itself, or the transmission signal frequency may be predetermined and stored in a memory from which the signal frequency providing unit 112 can read the transmission signal frequency. The signal frequency providing unit 112 is then adapted to provide the transmission signal frequency to the detection unit 113.

[0040] Detection unit 113 is adapted to detect the motion of person 140 by performing passive Doppler sensing based on the received radio frequency signal 131 and the frequency of the provided transmitted signal. Passive Doppler sensing includes at least Doppler analysis based on the received radio frequency signal 131 and the frequency of the provided transmitted signal. For example, detection unit 113 may be adapted to multiply an electronic representation of the received radio frequency signal 131 with an electronic representation of a periodic signal having the frequency of the transmitted signal via hardware or software. Optionally, a low-pass filter may also be provided on the resulting multiplied signal such that the filtered signal includes only frequencies below a predetermined frequency threshold. Mathematically, the signal multiplication and low-pass filtering can be considered as determining the difference between two input signals, where the excitation in the non-zero frequency range of the resulting signal is due to the Doppler effect of the moving person 140 on the transmitted radio frequency signal 121. In a first approximation, the excitation frequency can be considered to be directly proportional to the relative velocity of the moving person 140. Therefore, the movement 141 and even the velocity of person 140 can be determined based on the excitation frequency. However, the detection unit 113 can also be adapted to incorporate more complex analysis methods into passive Doppler sensing. For example, the detection unit 131 can also utilize the I-channel and Q-channel to determine the Doppler frequency shift caused by the movement 141 of the person 140.

[0041] The following describes some further, more detailed embodiments and applications of the detection system 110. In the embodiments described below, at least two devices are part of a network of network devices that can be controlled by a control unit. Generally, the network can be based on different network communication protocols, such as WiFi, Bluetooth, Zigbee, etc.

[0042] In one embodiment, the network refers to, for example, a WiFi network (e.g., 2.4 GHz). In this case, the control unit can be adapted to control the network devices to transmit radio frequency signals in an ultra-wideband frequency range on non-overlapping frequencies. This non-overlap can be achieved by using available channels, but it can also be achieved by using completely different frequencies (e.g., 2.4 GHz and 60 GHz for the WiFi communication protocol). Furthermore, the transmission signal frequencies of all network devices, i.e., the channels used, can be provided to the detection unit. However, if the detection unit is part of each network device, the detection unit of each network device can be provided only with the transmission signal frequencies of adjacent network devices. Using passive Doppler sensing, the detection unit (optionally, each detection unit of each network device independently) can then attempt to sense motion, for example, by looking for non-zero frequency components in the product of the received radio frequency signal and a signal with the corresponding transmission signal frequency. Furthermore, the detection unit can be adapted to identify possible noise sources (such as vibrations), which can manifest as, for example, narrow-frequency-range excitations in the received radio frequency signal and are typically caused by mechanical vibration or electromagnetic interference. The identification of noise in the received radio frequency signal can be based on monitoring the low spectrum of the transmitted radio frequency signal that is not reflected by an object. Specifically, each network device can also receive radio frequency signals generated by its own transmitted signals, which are not reflected by the object. The excitation frequency in these monitored signals, which have a narrow frequency range and often appear abruptly in the monitored signal, can then be identified. Therefore, in passive Doppler sensing, such frequencies can then be ignored by the detection unit. Additionally or alternatively, vibration monitoring can be achieved by the detection unit by analyzing the Doppler spectrum of the received radio frequency signal. A constant, narrow-frequency excitation—that is, one that does not shift in the spectrum for more than, for example, 500 ms—can then be identified as vibration and filtered out for Doppler sensing. Furthermore, the detection unit can be adapted to employ two channels with a phase shift of, for example, 90°, namely, channels c1(t) and c2(t) of the I and Q channels. Based on these channels, the detection unit can be adapted to construct a new signal s(t) = c1(t) + i c2(t), where i is an imaginary number. Based on the complex Fourier transform of this new signal, Doppler sensing can be performed, for example, by subtracting the positive spectrum from the negative spectrum of the complex Fourier transform and performing Doppler analysis on the result.

[0043] In one embodiment, the network can be further adapted to perform radio frequency (RF) sensing, for example, by exchanging short network messages and by monitoring amplitude changes in these messages, which indicate temporal changes in the environment. In this case, detection can be adapted to double-confirm the results of RF sensing through temporary switching of passive Doppler sensing. This has the advantage that the default operating mode of the network devices is standby power friendly.

[0044] In one embodiment, the network can also be adapted to utilize 5.8 GHz multichannel. For example, the control unit can be adapted to provide a trigger signal or cause one of the network devices to provide a trigger signal, based on which the network device is adapted to transmit two radio frequency signals, one in the 5.8 GHz range and one in the 24 GHz range. The detection unit can then be adapted to analyze the two spectra of the received signals and subtract the overlapping portions. The insight in this embodiment is that motion signals typically appear in different parts of the spectrum and will therefore still be present in the resulting spectrum. Conversely, vibrations occurring at similar frequencies in both spectra will therefore cancel each other out by subtraction in the resulting spectrum. Generally, the detection device can be adapted to assign a lower transmit signal frequency (e.g., 2.4 GHz) to the transmitter expected to suffer more vibration (e.g., due to its proximity to a vibration source) and a higher transmit signal frequency (e.g., 60 GHz) to the transmitter expected to suffer less vibration.

[0045] The presence of vibrations or singular spikes in the received signal is sometimes related to the periodicity of temperature changes and is a result of the expansion and / or contraction of mechanical components in network devices. This is especially true if the network device includes lighting functionality, as the light is being turned on or off. Generally, false alarms due to movement or presence caused by vibration are not a major problem when the light has just been turned on, since someone should be present anyway. However, such false alarms are undesirable when the light has just been turned off. Therefore, to avoid false alarms in passive Doppler sensing or RF sensing results, the detection unit can be adapted to start with either sensing method and then additionally execute the other only during difficult off-time periods (e.g., 0 to 30 minutes after the light has been turned off) to maximize the robustness of detection to vibration and achieve a fully standby power system.

[0046] In one embodiment, instead of attempting to avoid the effects of vibration, it is desirable to detect the vibration of a specific object. In this case, the detection unit can be adapted to control a transmitting device to send a radio frequency signal with a transmission signal frequency that is sensitive to the mechanical vibration of the transmitting device itself and / or objects in its field of view. For example, lighting equipment can thus be used to monitor the vibration of heating, ventilation, and air conditioning (HVAC) units near an office ceiling. In this example, a sudden increase in vibration of the HVAC equipment may cause vibration of nearby lighting equipment and indicate an impending HVAC equipment failure. The system described above can then be used to monitor such vibration events. In another exemplary application, the detection device can be adapted to employ passive Doppler sensing, optionally with additional radio frequency sensing, to monitor the activation time of a machine (such as a conveyor belt) and, for example, to monitor changes in machine vibration patterns that indicate impending damage to machine parts. Based on such monitoring, maintenance can be proactively scheduled to avoid more serious damage to the machine and unplanned downtime.

[0047] In one embodiment, the control unit may be adapted to select transmitting and receiving devices such that two different pairs of devices are assigned to monitor a moving environment, with the two pairs having overlapping sensing fields of view. The control unit may, for example, control the first pair to use a transmitting signal frequency within the 5 GHz WiFi range, while controlling the second pair to use a transmitting signal frequency within the 60 GHz WiFi range. The detection unit may then be adapted to perform passive Doppler sensing based on the received signals from the two pairs, for example, to perform drop detection of a person or package in a warehouse. Drops are typically characterized by an acceleration of 1g followed by a deceleration of approximately -5g. By simultaneously monitoring the target area at two different frequencies, it is possible to detect both drop detection and the presence of a person. For example, the detection unit may be adapted to use a 5.8 GHz signal for drop detection, as the fall of an object often results in a large frequency difference, which is visible in the spectrum of the received signal from the 5.8 GHz device pair. To detect the presence of a person, for example, by sensing respiration, the detection unit may be adapted to utilize a higher frequency that tends to provide a higher resolution spectrum. Furthermore, when rigid objects fall to the floor, they will vibrate briefly after impacting the floor. Therefore, the detection unit can also be adapted to monitor the vibration of an object, for example, that has just fallen from a warehouse shelf / forklift, in order to assess the force with which the object has impacted the floor.

[0048] Figure 2 A method for detecting movement of an object is illustrated schematically and exemplary. Method 200 includes a first step 210: controlling at least two radio frequency devices (e.g., Figure 1The radio frequency devices 120 and 130 shown are configured such that at least one of the at least two devices is a transmitting device that transmits a radio frequency signal (e.g., radio frequency signal 121) having a transmission signal frequency; and at least one of the at least two radio frequency devices 120 and 130 is a receiving device that receives a radio frequency signal (e.g., radio frequency signal 131) generated by reflection of the radio frequency signal transmitted by the object. In a further step 220, the method includes providing a transmission signal frequency at which the radio frequency signal has already been transmitted, for example for use in the next step 230. In step 230, motion of the object is detected, for example, by performing passive Doppler sensing based on the received radio frequency signal and the provided transmission signal frequency, according to the principles explained above.

[0049] The following explains some general principles. Radio frequency (RF) sensing is a technology that is gaining increasing attention. The basic idea is that a system of wireless RF devices exchanges messages about the amplitude of their signals being monitored. Any change in amplitude indicates a change in the environment near both the transmitter and receiver RF devices. RF sensing can utilize standard wireless RF devices. For example, most ZigBee devices use 2.4 GHz signals, although the ZigBee standard can also be implemented at 868 MHz. Many modern WiFi devices now use both 2.4 GHz and 5 GHz signals, and in a few years they may even use 60 GHz WiFi signals.

[0050] In recent years, so-called passive Doppler sensing has been developed. This technology is challenging because it requires identifying both the signal from a moving object and the carrier frequency within the signal. However, compared to standard radio frequency detection, the advantage of using passive Doppler detection lies in the wealth of information that can be obtained.

[0051] Generally, the higher the frequency (i.e., the shorter the wavelength), the more susceptible a sensing system using radio frequency (RF) signals to transmit or receive mechanical vibrations is to the impact. For example, mechanical vibrations from sources such as blinds in lighting fixtures used as network equipment can severely affect the performance of mass-market 5.8 GHz RF sensors. Therefore, when utilizing RF sensing, there is a need for carefully designed sensing algorithms that take into account robustness to vibration. Furthermore, it is known that conventional preventative maintenance addresses 18% of machine problems, while 82% of machine failures are due to random or unknown factors. The prior art also teaches that the 82% of unknown factors are best identified through continuous monitoring of the machine and addressed using predictive maintenance. It is known that, often, the motor itself within the machine is an early indicator of the risk of unplanned downtime. It is known, in particular, that vibration and temperature sensors reveal the condition of motors (e.g., motors used in conveyor belts). To track motor operation 24 hours a day, based on the aforementioned invention, it is proposed to employ vibration sensing using the detection system described above to determine, for example, the average total usage time of the machine, which helps in understanding the threshold for preventative or periodic maintenance. For example, using the obtained data, it can be concluded that a usage threshold of 2500 hours is still acceptable, but preventative maintenance should be scheduled around 2000 hours to limit the risk of unplanned downtime. Specifically, the detection system described above can be used to monitor machine vibration without requiring vibration sensors to be directly attached to the machine. For example, by carefully monitoring vibration frequencies and patterns, a baseline of the motor's condition can be established, and ultimately, the motor's health status can be estimated. For instance, for several months, the motor's vibration level remains consistent with a predetermined baseline, making maintenance unnecessary. However, eventually, the vibration frequency and / or amplitude begin to increase, for example, because motor components have worn thinner. Based on the difference from the baseline, it can be determined that the motor components need to be replaced as soon as possible.

[0052] In another application, the detection system can be used for automatic lighting control. The requirements for automatic lighting control are often very stringent. Turning on the lights when someone enters should be rapid, but turning them on when no one is present (i.e., false alarms) is highly undesirable. In some applications, light activation also incorporates safety elements; for example, in a multi-aisle warehouse, turning on the lights at an intersection between two islands warns a forklift that is approaching the intersection. Furthermore, if radio frequency sensing is applied to lighting control in most applications, the sensing performance depends on the light state itself; for example, false alarms when the lights are off are highly undesirable because they cause a very noticeable system malfunction (i.e., failure). The above invention allows these problems to be overcome by providing passive Doppler sensing for controlling lighting systems as a complement to or replacement for radio frequency sensing.

[0053] Preferably, for passive Doppler transmission, two different transmission signal frequencies (e.g., 2.4 GHz WiFi and 5 GHz WiFi) are used to eliminate false triggering due to vibration, as described in detail above. In particular, using two transmission signal frequencies can be advantageous in applications where strong vibrations are expected—e.g., where office lighting troughs are installed in the ceiling of a system near HVAC ducts, or where pendant lights in a warehouse are placed near heavy machinery. Furthermore, in addition to vibrations of the transmitting and / or receiving devices themselves, vibrations of objects within the field of view of the sensing system can also cause false triggering. This can also be addressed by utilizing two different frequencies as the transmission signal frequencies as described above.

[0054] Furthermore, to allow for reduction of the impact of vibration, the detection system described above can be adapted to control network device systems (e.g., lighting systems) and can be adapted to apply passive Doppler sensing, which ignores narrow-frequency excitation if the network device system is off. In this case, the detection unit can be adapted to filter the received signal, for example, by using I and Q channels and subtracting the positive frequency from the negative frequency. Preferably, in a lighting system, passive Doppler sensing is applied by the detection unit in the off state and / or only after the RF sensing has observed a trigger (e.g., the presence of a person). In one embodiment, two different frequency carriers (i.e., two different transmitted signal frequencies) are used for passive Doppler sensing, and the two signals are compared to identify vibrations present in the device or in the sensed field of view. The comparison can be made in the frequency domain, and the resulting spectrum can be subtracted. The frequency at which vibration occurs is independent of the carrier frequency, while the Doppler effect is dependent on the carrier frequency. Therefore, by subtracting the resulting spectrum, vibration can be removed from the signal, but the actual motion is preserved. Additionally or alternatively, the comparison can be made in the time domain by comparing the energy present in the two channels. Further motion analysis is only performed if both channels are sufficiently above the predetermined threshold.

[0055] Preferably, passive Doppler sensing is performed during the device's cooling phase. During the cooling phase, the microwave carrier frequency emitted by the device can interfere with nearby radio frequency sensors due to carrier shift. Therefore, although the first pair of lights implies different carrier frequencies (i.e., transmission signal frequencies), the adjacent second pair of lights performs sensing within the radio frequency range. Due to temperature changes in the first pair of lights, their carrier frequencies change and may become the same as the carrier frequency of the second pair. Thus, the sensing of the first and second pairs of lights can interfere with each other. However, this can only occur on one channel (i.e., the transmission signal frequency) at a time. Therefore, performing passive Doppler sensing based on multiple different transmission signal frequencies can help identify and avoid this problem. This embodiment can also be applied during the device's power-on phase.

[0056] In one embodiment, it is preferable to turn off the transmission of radio frequency signals if the device (e.g., a light) has been off for a considerable amount of time (e.g., more than 30 minutes) to save energy and reduce unwanted wireless smoke.

[0057] By studying the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement other variations of the disclosed embodiments in practicing the claimed invention.

[0058] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0059] A single unit or device can perform the functions of several items listed in the claims. The mere fact that certain measures are referenced in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously.

[0060] Processes performed by one or more units or devices (e.g., control of at least two devices, provision of radio frequency signals, and detection of motion, etc.) can be performed by any other number of units or devices. These processes can be implemented as program code devices of computer programs and / or as dedicated hardware.

[0061] Computer program products may be stored / distributed on suitable media, such as optical storage media or solid-state media, provided together with or as part of other hardware; but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0062] Any reference numerals in the claims should not be construed as limiting the scope.

[0063] This invention relates to a detection system for detecting motion of an object by utilizing at least two devices adapted to transmit and receive radio frequency signals. The system includes: a control unit for controlling the at least two devices such that at least one of the at least two devices is a transmitting device that transmits a radio frequency signal having a transmission signal frequency, and such that at least one of the at least two devices is a receiving device that receives the radio frequency signal, the radio frequency signal indicating the reflection of the transmitted radio frequency signal from the object; a signal frequency providing unit for providing a transmission signal frequency at which the radio frequency signal has been transmitted; and a detection unit for detecting motion of the object by performing passive Doppler sensing based on the received radio frequency signal and the provided transmission signal frequency.

Claims

1. A detection system for detecting motion (141) of an object (140) by utilizing at least two devices (120, 130) adapted to transmit and receive radio frequency signals (121, 131), wherein the system (110) comprises: A control unit (111) controls the at least two devices (120, 130) such that at least one of the at least two devices (120, 130) is a transmitting device (120) that transmits a radio frequency signal (121) having a transmission signal frequency, and at least one of the at least two devices (120, 130) is a receiving device (130) that receives a radio frequency signal (131) indicating the reflection of a radio frequency signal transmitted by the object (140). A signal frequency providing unit (112) is used to provide the transmission signal frequency, at which the radio frequency signal (121) has already been transmitted, and The detection unit (113) is used to detect the motion (141) of the object (140) by performing passive Doppler sensing based on the received radio frequency signal (131) and the provided transmission signal frequency. The detection unit (113) is adapted to: determine an excitation within a frequency range in the spectrum of the received radio frequency signal (131), wherein the excitation occurs at the same frequency or frequency range within a predetermined time period and its amplitude is not less than a noise threshold; and perform the passive Doppler sensing based on the received radio frequency signal (131) by filtering out the excitation within the frequency range in the spectrum of the received radio frequency signal (131).

2. The detection system according to claim 1, wherein the control unit (111) is further adapted to: control the at least two devices (120, 130) such that each of the at least two devices (120, 130) acts as a transmitting device (120), each transmitting device (120) transmitting a radio frequency signal (121) having a different signal frequency; and control the at least two devices (120, 130) such that each device acts as a receiving device (130) to receive a radio frequency signal (131), the radio frequency signal (131) indicating the reflection of a radio frequency signal (121) transmitted by an object (140) corresponding to a radio frequency signal (121) transmitted by the corresponding other device, wherein the detection unit (113) is adapted to perform passive Doppler sensing based on the received radio frequency signal (131).

3. The detection system according to any one of claims 1 and 2, wherein the control unit (111) is adapted to control the transmitting device (120) to detect the radio frequency signal generated by the reflection of the transmitted radio frequency signal (121) transmitted by itself, and wherein the detection unit (113) is adapted to monitor the detected radio frequency signal and also to detect the motion (141) of the object (140) based on the monitored radio frequency signal.

4. The system according to any one of claims 1 and 2, wherein the detection unit (113) is adapted to determine the I channel and the Q channel based on the received radio frequency signal (131), and to perform the passive Doppler sensing based on the I channel and the Q channel.

5. The detection system according to any one of claims 1 and 2, wherein the control unit (111) is further adapted to control the transmitting device (120) to transmit an additional radio frequency signal at a frequency different from the frequency of the transmitted signal, and to control the receiving device (130) to receive an additional radio frequency signal generated by the reflection of the additional radio frequency signal from the object (140), and wherein the detection unit (113) is further adapted to perform the passive Doppler sensing based on the additional received radio frequency signal.

6. The detection system according to claim 5, wherein the detection unit (113) is adapted to further perform the passive Doppler sensing based on the additionally received radio frequency signal by comparing the additionally received radio frequency signal with the received radio frequency signal (131).

7. The system of claim 6, wherein the comparison refers to subtracting the additional received radio frequency signal from the received radio frequency signal (131) in the frequency domain, wherein the detection unit (113) is adapted to detect motion (141) based on the signal obtained by the subtraction.

8. The system of claim 6, wherein the comparison refers to performing Doppler analysis on two independent signals and comparing the results of the Doppler analysis in terms of consistency.

9. The system according to any one of claims 1 and 2, wherein the detection unit (113) is further adapted to perform radio frequency sensing based on the amplitude of the received signal, and wherein the detection unit (113) is adapted to perform passive Doppler sensing as an alternative to or supplement to radio frequency sensing, based on a sensing result determined for at least one of the at least two devices (120, 130) and / or based on the device state of at least one of the at least two devices (120, 130).

10. The system according to any one of claims 1 and 2, wherein two pairs of devices are used for motion detection, wherein the control unit (111) is adapted to control each pair of devices such that each pair of devices includes at least a transmitting device and a receiving device, wherein the control unit (111) is also adapted to control the transmitting device and the receiving device such that radio frequency signals of different frequencies are used by the two pairs of devices for passive Doppler sensing, wherein the detection unit (113) is adapted to independently perform the passive Doppler sensing on each pair of devices and further detect motion based on a comparison of the obtained detection results.

11. The system of claim 10, wherein the detected motion refers to minute movement or vibration of the object.

12. The system according to any one of claims 1 and 2, wherein the result of motion detection is used to control the function of the device.

13. A detection method for detecting motion of an object by utilizing at least two devices suitable for transmitting and receiving radio frequency signals, wherein the method (200) comprises: Control (210) the at least two devices such that at least one of the at least two devices is a transmitting device that transmits a radio frequency signal having a transmission signal frequency, and such that at least one of the at least two devices is a receiving device that receives a radio frequency signal indicating the reflection of a radio frequency signal transmitted by the object. Provide (220) the transmission signal frequency, the radio frequency signal has been transmitted at the transmission signal frequency, and The motion of the object is detected (230) by performing passive Doppler sensing based on the received radio frequency signal and the frequency of the provided transmitted signal. The method further includes determining an excitation within a frequency range in the spectrum of the received radio frequency signal (131), wherein the excitation occurs at the same frequency or frequency range within a predetermined time period and its amplitude is not less than a noise threshold, and performing the passive Doppler sensing based on the received radio frequency signal (131) by filtering out the excitation within the frequency range in the spectrum of the received radio frequency signal (131).

14. A computer program product for detecting motion, wherein the computer program product includes program code means that causes the detection system of claim 1 to perform the detection method of claim 13.

Images