Patent Description:
There is known a detection device that measures a distance to an object, a speed of the object, and the like using an electromagnetic wave or a sound wave. In such a detection device, it is known to use both a Doppler system and an FM-CW (Frequency Modulated Continuous Wave) system. These techniques are disclosed in Patent Document <NUM> (<CIT>), Patent Document <NUM> (<CIT>), and Patent Document <NUM> (<CIT>). Reference may also be made to: <CIT> which relates to an FMCW RADAR sensor for motor vehicles; <CIT> which relates to an obstacle detecting system; or <CIT> which relates to a watching device and watching system.

It is desirable to provide a detection device and a detection method that appropriately measure the motion and the distance of an object.

The present invention is defined by the appended independent claims to which reference should now be made. Specific embodiments are defined in the dependent claims. According to one arrangement of the present disclosure, there is provided a detection device including a transmitter configured to transmit an electromagnetic wave or a sound wave as a transmission signal, a receiver configured to receive a signal obtained by reflecting the transmission signal from an object, as a reception signal, a mixer configured to mix the transmission signal and the reception signal and output a mixed signal as an intermediate signal, and a detector configured to detect a motion of the object and a distance to the object from the intermediate signal, wherein the detector performs first sampling of the intermediate signal at a first sampling time in a first time interval when detecting the motion of the object, and the detector performs second sampling at a second sampling time in a second time interval smaller than the first time interval, between adjacent first sampling times when detecting the distance to the object.

According to another arrangement of the present disclosure, there is provided a detection method causing a processor to execute a process. The process includes detecting the motion of an object by performing first sampling of an intermediate signal at a first sampling time in a first time interval, the intermediate signal being obtained by mixing a transmission signal which is an electromagnetic wave or a sound wave and a reception signal obtained by reflecting the transmission signal on the object, and detecting a distance to the object by performing second sampling of the intermediate signal at a second sampling time in a second time interval smaller than the first time interval, between adjacent first sampling times.

According to the detection device and the detection method according to embodiments of aspects of the present disclosure, it is possible to appropriately measure the motion and the distance of the object.

The invention is described, by way of example only, with reference to the following drawings, in which:.

The detection device according to the present embodiment determines the position of the object, in other words, the distance from the detection device, while detecting a signal in a very low frequency band such as vibration of the body, such as heartbeat or respiration, or small vibration of a building or movement of the ground.

Since the motion velocity of such an object is small and the degree of change in distance is very small, it is not necessary to measure the distance frequently.

In the present embodiment, a Doppler signal is used to detect the motion or velocity of the object such as a slow shake, and the detected signal is sampled at a sampling frequency of about several hundred sps and at intervals of several milliseconds. On the other hand, an FM-CW signal is used to measure the distance of the object, and the detected signal is sampled at a sampling frequency of several tens of ksps and at intervals of several tens of microseconds. In this way, the difference between both sampling frequencies is made several hundred times. Therefore, the FM-CW signal can be sampled several hundred times during one sampling interval of the Doppler signal. As a result, the distance to the object can be determined before the analysis of the Doppler signal is completed.

At this time, it is preferable to appropriately perform switching between sampling of the Doppler signal and sampling of the FM-CW signal.

Embodiments will be described below with reference to the drawings.

<FIG> is a block diagram illustrating the periphery of a detection device according to a first embodiment. A detection device <NUM> includes a receiving unit <NUM>, a transmitting unit <NUM>, a mixer <NUM>, an oscillator <NUM>, a band separation filter <NUM>, a processing unit <NUM>, and a memory <NUM>. The processing unit <NUM> is, for example, a processor such as a CPU (Central Processing Unit) or a microcomputer, and functions as a detection unit <NUM> and a control unit <NUM> in cooperation with software. Further, the processing unit <NUM> executes detection processing. The memory <NUM> is a non-volatile memory or a volatile memory, and stores setting conditions for detection, data during calculation of information, a program, and the like. An external device <NUM> may be a processor different from the processor <NUM>. The external device <NUM> may be a higher-level application in the same processor as the processing unit <NUM>.

The control unit <NUM> outputs a control signal Vo for controlling the frequency of an oscillation signal So to the oscillator <NUM>. The oscillator <NUM> outputs an oscillation signal So having a frequency fo set based on the control signal Vo. The transmitting unit <NUM> outputs a transmission signal Rt having the same frequency as the oscillation signal So to an object <NUM> in the space via an antenna <NUM>. The transmission signal Rt is, for example, an electromagnetic wave such as a microwave or a millimeter wave, or an acoustic wave. When the transmission signal Rt is the electromagnetic wave, the frequency of the transmission signal Rt is, for example, <NUM> to <NUM>.

The transmission signal Rt is reflected at the object <NUM>. The receiving unit <NUM> receives a reception signal Rr via an antenna <NUM>. The reception signal Rr includes a signal reflected from the object <NUM>. The receiving unit <NUM> outputs a reception signal Sr to the mixer <NUM>. The mixer <NUM> mixes the oscillation signal So and the reception signal Sr, and outputs a mixed intermediate signal IF. The frequency of the intermediate signal IF corresponds to a difference between the frequency fo of the oscillation signal So and the frequency of the reception signal Sr. The band separation filter <NUM> separates the intermediate signal IF into an intermediate signal IF1 having a low frequency band and an intermediate signal IF2 having a high frequency band. Based on the intermediate signal IF1, the detection unit <NUM> detects the relative motion between the object <NUM> and the detection device <NUM>, such as the shake of the object <NUM>, and outputs corresponding information I1. For example, a Doppler method is used to detect the motion of the object <NUM>. The detection unit <NUM> detects the distance between the object <NUM> and the detection device <NUM> based on the intermediate signal IF2, and outputs corresponding information I2. For example, an FM-CW system is used for the detection of the distance.

The detection unit <NUM> outputs the information I1 and I2 to the external device <NUM>. When the detection unit <NUM> detects the motion of the object <NUM> by the Doppler method, the control unit <NUM> sets the frequency fo of the oscillation signal So to a constant frequency fo1. When a request Rq for distance measurement is input from the external device <NUM> to the control unit <NUM>, the control unit <NUM> controls the oscillator <NUM> so as to sweep the frequency fo of the oscillation signal So and causes the detection unit <NUM> to detect the distance by the FM-CW method.

The detection device <NUM> is installed, for example, in a room, and the object <NUM> is, for example, a human or an animal. At this time, the motion-related information I1 is, for example, vital information of a human or an animal, and corresponds to, for example, vibrations of the chest caused by heartbeat or respiration. In this case, the amount of motion of the object <NUM> is, for example, <NUM> to <NUM> (about <NUM> as an example), the frequency of vibration is, for example, <NUM> to <NUM> (about <NUM> as an example), and the velocity of the object <NUM> is, for example, <NUM>/s to <NUM>/s (about <NUM>/s as an example). Thus, the motion velocity of the object <NUM> is very slow. The motion of the object <NUM> detected by the detection device <NUM> may be a small vibration of the building or a vibration of the ground in addition to the vital information.

<FIG> is a flowchart illustrating processing executed by the processing unit <NUM> of the detection device <NUM> according to the first embodiment. <FIG> is a timing chart of the detection device <NUM> according to the first embodiment. <FIG> is an enlarged view of <FIG>. In <FIG> and <FIG>, fo represents the frequency of the oscillation signal So (the frequency of the transmission signal Rt), IF represents the voltage of the intermediate signal IF, sampling represents periods <NUM> and <NUM> during which the detection unit <NUM> samples the intermediate signal IF, and vertical dotted lines in the periods <NUM> and <NUM> represent sampling timings. In <FIG>, So denotes the voltage of the oscillation signal So. In <FIG> and <FIG>, black circles on solid lines of IF indicate voltages at sampling times SP1, SP1a, SP1b, and SP2 at which the intermediate signal IF is sampled. Hereinafter, the sampling of the intermediate signal IFI is referred to as "sampling SP1" and the sampling of the intermediate signal IF2 is referred to as "sampling SP2". The period <NUM> is a period during which the detection unit <NUM> performs the sampling SP1, and the period <NUM> is a period during which the detection unit <NUM> performs the sampling SP2.

As illustrated in <FIG>, the detection device <NUM> is activated by turning on the power of the detection device <NUM> or the like (S10). The processing unit <NUM> sets the sampling frequency (sampling interval T1) of the sampling SP1 of the intermediate signal IF1 (S12). For example, the sampling frequency is set to <NUM> sps and the sampling interval T1 is set to <NUM>. The number of sampling times is, for example, <NUM>. The control unit <NUM> sets the frequency of the oscillation signal So to a constant frequency fo0. The sampling frequency, sampling interval, sampling number of times and the like of the intermediate signal IF1 are set in advance and may be stored in the memory <NUM> or may be acquired from the external device <NUM>. The detection unit <NUM> starts sampling of the intermediate signal IF1 at time t1, and performs the sampling SP1 in the period <NUM> (S14).

As illustrated in <FIG>, the control unit <NUM> determines whether the request Rq for distance measurement is input (S16). The request Rq is input from, for example, the external device <NUM>. The request Rq may be input at regular intervals. If the determination of S16 is "No", the process returns to S14. By repeating S14 at interval T1, the sampling SP1 is executed at constant interval T1 in period <NUM>.

If the determination of S16 is "Yes", the detection unit <NUM> switches the sampling process from the sampling SP1 to the sampling SP2 (S18). For example, the sampling frequency of the sampling SP2 is <NUM> ksps and the sampling interval T2 is <NUM>. The sampling frequency of the sampling SP2 in the period <NUM> is set to <NUM> times, for example. The sampling frequency, sampling interval and sampling number of the intermediate signal IF2 are set in advance and may be stored in the memory <NUM> or may be acquired from the external device <NUM>.

In the example of <FIG>, the request Rq is input before the sampling time SP1a. At time t2 after the sampling time SP1a, the detection unit <NUM> switches sampling from the sampling SP1 to the sampling SP2. The control unit <NUM> sweeps the frequency fo of the oscillation signal So.

As illustrated in <FIG>, in the period <NUM>, the frequency fo of the oscillation signal So is fo0 and constant. When the request Rq is input, at time t21 after the sampling time SP1a, the control unit <NUM> sets the frequency fo to the frequency fo1 for executing the FM-CW system. Thereafter, the control unit <NUM> executes the sampling SP2 from time t22. A period <NUM> between the times t21 and t22 is a period until the oscillation signal So in which the frequency fo is changed from fo0 to fo1 is stabilized. At time t22, the frequency fo is stabilized at the frequency fo1. The period <NUM> is defined between the start time t22 of the sampling SP2 and the end time t31 of the sampling SP2. The frequency of the oscillation signal So is swept from time t22, and the frequency fo increases linearly from fo1 with time, and reaches fo2 at time t5. In the period between time t5 and time t31, the frequency fo decreases linearly from fo2 to fo1 with time.

As illustrated in <FIG>, the detection unit <NUM> performs the sampling SP2 of the intermediate signal IF2 (S20). The detection unit <NUM> determines whether the sampling SP2 is completed (S22). When the number of times of sampling does not reach the predetermined number of times of sampling, the detection unit <NUM> determines that S22 is No and returns to S20. By repeating S20 at interval T2, the sampling SP2 is executed at constant interval T2 in period <NUM>.

On the other hand, when the predetermined number of times of sampling is reached and Yes is determined in S22, the detection unit <NUM> switches sampling from the sampling SP2 to the sampling SP1 (S23). At this time, as illustrated in <FIG>, the control unit <NUM> sets the frequency fo of the oscillation signal So to a constant fo0 at time t31. A period <NUM> between the times t31 and t32 is a period until the oscillation signal So in which the frequency fo is changed from fo1 to fo0 is stabilized. At time t32, the frequency fo is stabilized at the frequency fo0. The period from time t32 is the period <NUM>.

As illustrated in <FIG>, the detection unit <NUM> calculates the distance of the object <NUM> using the FM-CW method based on the sampling data acquired in the period <NUM> (S24). The detection unit <NUM> outputs the information I2 corresponding to the calculated distance to the external device <NUM> (S26). The detection unit <NUM> determines whether the sampling SP1 is completed (S28). The detection unit <NUM> determines that S28 is No when a predetermined number of sampling times is not reached, and determines that S28 is Yes when a predetermined number of sampling times is reached. If S28 is "No", the process returns to S14.

As illustrated in <FIG> and <FIG>, the sampling SP1 is executed at sampling time SP1b when interval T1 has elapsed from sampling time SP1a after time t32. Thereafter, sampling SP1 is executed at interval T1 in period <NUM>. The interval between the sampling time SP1a and the sampling time SP1b is T1, which is the same as the interval T1 in the period <NUM>. For example, when the sampling frequency of the sampling SP2 is <NUM> ksps and the number of times of sampling performed in the period <NUM> is <NUM>, the length of the period <NUM> is <NUM>. Therefore, the period <NUM> falls within the interval T1 (<NUM>) of the sampling SP1.

As illustrated in <FIG>, when S28 is Yes, the detection unit <NUM> ends the sampling SP1 (S29). In the example of <FIG>, the period <NUM> ends at time t4. The detection unit <NUM> calculates the motion of the object <NUM> using the Doppler method based on the sampling data acquired in the period <NUM> (S30). The detection unit <NUM> outputs the calculated information I1 regarding the motion of the object <NUM> to the external device <NUM> (S32). The detection unit <NUM> determines whether or not a series of processes is ended (S34). For example, when the power supply is turned off or when there is a request for completion from the external device <NUM>, the detection unit <NUM> determines that S34 is Yes. If S34 is "No", the process returns to step S12, and if S34 is "Yes", the process ends.

<FIG> is a timing chart illustrating voltage changes of the intermediate signals IF, IF1 and IF2 with respect to time in the embodiment. As illustrated in <FIG>, in the intermediate signal IF, a periodic signal having a relatively low frequency is superimposed with a sharp signal having a high frequency. The band separation filter <NUM> separates the intermediate signal IF into a low-frequency intermediate signal IF1 and a high-frequency intermediate signal IF2, and outputs the intermediate signals IF1 and IF2 to the detection unit <NUM>. The intermediate signal IF1 is a signal when the motion and the velocity of the object <NUM> are detected by the Doppler method. The intermediate signal IF2 is a signal when the distance of the object is detected by the FM-CW method, and corresponds to the intermediate signal IF of the period <NUM> in <FIG> and <FIG>.

<FIG> is a timing chart illustrating the voltage change of the intermediate signal IF1 with respect to time in the first embodiment. An example in which the intermediate signal IF1 is a signal corresponding to the heart rate of a human or the like will be described. As illustrated in <FIG>, the intermediate signal IF1 becomes minimum at time t6 and becomes maximum at time t7. Heart rate can be measured by measuring the interval between times t6 and t7 or between adjacent times t6. It is also possible to measure the velocity of the object <NUM> from the frequency component when the intermediate signal IF1 is Fourier-transformed. In this case, the velocity V of the object <NUM> can be calculated by Equation <NUM>.

Wherein C is the velocity of light, Fiv is the frequency component of the intermediate signal IF1, and Fc is the frequency of the transmission signal Rt (frequency fo0 of the oscillation signal So). When a plurality of objects <NUM> exist and the motions (for example, heart rate) of the objects <NUM> are different from each other, the motion of each object <NUM> (for example, heart rates of the plurality of objects <NUM>) can also be measured.

<FIG> is a timing chart illustrating the voltage change of the intermediate signal IF2 with respect to time in the period <NUM>. As illustrated in <FIG>, the intermediate signal IF2 increases from time t22 to time t5, and the intermediate signal IF2 decreases from time t5 to time t31. A waveform having a short wavelength is superimposed on the intermediate signal IF2 illustrated in <FIG>. The frequency of the short-wavelength waveform corresponds to the distance to the object <NUM>. The distance R of the object <NUM> can be calculated by Equation <NUM>.

Wherein C is the velocity of light. Ts is a sweep period, which is a period between time t22 and time t5 or a period between time t5 and time t31. Fir denotes a frequency component of the intermediate signal IF2, and Bw denotes a displacement amount of the frequency fo, which is fo2-fo1. Fir can be calculated by Fourier transformation of the intermediate signal IF2, and the distance R to the object <NUM> can be calculated using Fir. In the period <NUM>, a sweep for increasing the frequency fo from fo1 to fo2 from time t22 to time t5 and a sweep for decreasing the frequency fo from fo2 to fo1 from time t5 to time t31 are performed. In this case, since the distance R to the object <NUM> can be measured in both the sweep period in which fo increases and the sweep period in which fo decreases, an average value of the distances R calculated in respective sweep periods may be used as the distance R to the object <NUM>. When the plurality of objects <NUM> exist, the distance R of the individual object <NUM> can also be measured.

An example of the sampling SP1 of the intermediate signal IF1 and the sampling SP2 of the intermediate signal IF2 will be described. Assuming that the ratio of the FM-CW frequency and the Doppler frequency is Z:<NUM>, the following equation <NUM> is obtained from the relationship between Equation <NUM> and Equation <NUM>.

As an example, the object <NUM> is a human and the heartbeat is measured. The motion velocity of the chest due to heartbeat is about <NUM>/s, for example. When <NUM> is used as Fc, Fiv becomes <NUM> from Equation <NUM>. Further, it is assumed that Bw is <NUM> and Ts is <NUM>. When the distance R of the object <NUM> is <NUM>, the condition for making measurement by the FM-CW method compatible with measurement by the Doppler method is Z = <NUM> from Equation <NUM>. Therefore, Fir = Fiv× <NUM>, that is, Fir is about <NUM>. On the other hand, when the distance R is changed from <NUM> to <NUM>, Z is <NUM> (Z = <NUM>) in order to make the FM-CW system compatible with the Doppler system. That is, the FM-CW frequency may be <NUM> times or more of the Doppler frequency. Here, when switching between the FM-CW system and the Doppler system, the band separation filter <NUM> is used to separate the intermediate signal IF1 at the time of measurement by the Doppler system from the intermediate signal IF2 at the time of measurement by the FM-CW system in order to prevent the intermediate signals IF detected by the respective systems from overlapping each other. If the difference between Fiv and Fir is set to <NUM> times (Fir = <NUM>) or more, which is higher than <NUM> times obtained by Equation <NUM>, the separation of the intermediate signals IF1 and IF2 by the filter becomes easier.

The sampling frequency of the sampling SP1 (IF1) is, for example, <NUM> sps to <NUM> sps, and the sampling frequency of the sampling SP2 (IF2) is, for example, <NUM> ksps to <NUM> ksps. As described above, since the difference between the frequencies of IF1 and IF2 is <NUM> times or more, the sampling frequency of the sampling SP2 is <NUM> times or more of the sampling frequency of the sampling SP1, and the sampling interval T2 is <NUM>/<NUM> times or less of the sampling interval T1. Since there is a <NUM>-fold difference in the sampling frequency, the sampling of the intermediate signal IF2 can be completed by generating a signal corresponding to the FM-CW system in a gap of the sampling interval T1. When the sampling interval T1 of the intermediate signal IF1 is <NUM> and the intermediate signal IF2 corresponding to the FM-CW system is sampled at <NUM> ksps, sampling data of <NUM> times can be obtained at the sampling interval T1.

According to the first embodiment, as illustrated in <FIG> and <FIG>, the detection unit <NUM> detects the motion of the object <NUM> by performing, on the intermediate signal IF1, the first sampling SP1 for sampling the intermediate signal IF1 at the first sampling time of the sampling interval T1 (first time interval). As illustrated in <FIG> and <FIG>, the detection unit <NUM> detects the distance to the object <NUM> by performing, on the intermediate signal IF2, the second sampling SP2 for sampling the intermediate signal IF2 at the second sampling time of the interval T2 (second time interval) between the adjacent sampling time SP1a and sampling time SP1b. When the motion of the object <NUM> is fast, the motion of the object <NUM> cannot be detected unless the sampling interval T1 is shortened. On the other hand, when the motion of the object <NUM> is slow, even if the sampling interval T1 is long, the motion of the object <NUM> can be detected sufficiently. When the motion of the object <NUM> is slow, the distance to the object <NUM> does not need to be detected frequently because the degree of change in distance is small. Therefore, the sampling SP2 is executed during the sampling interval T1. Thus, the detection unit <NUM> can complete the detection of the distance to the object <NUM> while detecting the motion of the object <NUM>. As an example in which the motion of the object <NUM> is slow, there is a case in which the object <NUM> is a human or an animal and the information I1 relating to the motion is vital information of the object <NUM>.

As illustrated in <FIG> and <FIG>, the transmitting unit <NUM> outputs the transmission signal having the constant frequency fo0 in the period <NUM> of the first period in which the detection unit <NUM> performs the first sampling SP1, excluding the period <NUM> (second period) in which the detection unit <NUM> performs the second sampling SP2. The transmission unit <NUM> outputs the transmission signal obtained by sweeping the frequency fo in the period <NUM>. Thus, the detection unit <NUM> can detect the distance of the object <NUM> using the FM-CW method while detecting the motion of the object using the Doppler method.

The band separation filter <NUM> separates the intermediate signal IF into the first intermediate signal IF1 of a first frequency band and a second intermediate signal IF2 of a second frequency band higher than the first frequency band, as illustrated in <FIG>, and outputs the separated signals to the detection unit <NUM>. The detection unit <NUM> performs the first sampling SP1 on the intermediate signal IF1 and performs the second sampling SP2 on the intermediate signal IF2. Therefore, the detection unit <NUM> can detect the motion from the intermediate signal IF1 and the distance from the intermediate signal IF2 in parallel.

The transmission signal Rt may be the electromagnetic wave or the acoustic wave, but in order to detect a slow motion, the frequency fo is preferably an electromagnetic wave of <NUM> or more and more preferably an electromagnetic wave of <NUM> or more.

<FIG> is a block diagram illustrating the periphery of a detection device according to a second embodiment. As illustrated in <FIG>, a detection device <NUM> according to the second embodiment includes an RF (Radio Frequency) processing unit <NUM>, an IF processing unit <NUM>, a conversion processing unit <NUM>, the processing unit <NUM>, and the memory <NUM>. The RF processing unit <NUM> is a circuit for processing high-frequency signals, and includes an LNA (Low Noise Amplifier) <NUM>, a PA (Power Amplifier) <NUM>, a phase shifter <NUM>, mixers 16a and 16b, amplifiers 17a and 17b, and the oscillator <NUM>. The IF processing unit <NUM> is a circuit for processing an intermediate signal, and includes a HPF (High Pass Filter) 22a, BPFs (Band Pass Filter) 22b and <NUM>, a LPF (Low Pass Filter) <NUM>, and amplifiers 24a, 24b, <NUM>, and <NUM>. The conversion processing unit <NUM> includes a multiplexer (MUX) <NUM>, analog-digital converters (ADC) 38a and 38b, and a digital-analog converter (DAC) <NUM>. The processing unit <NUM> is, for example, a processor, cooperates with software, and functions as the detection unit <NUM> and the control unit <NUM> of the first embodiment. The memory <NUM> is the same as the memory <NUM> of the first embodiment.

The DAC <NUM> converts a control signal, which is a digital signal output from the control unit <NUM>, into an analog signal. The LPF <NUM> suppresses a high frequency component of the control signal Vo which is an analog signal. The amplifier <NUM> amplifies the control signal Vo. The oscillator <NUM> is a VCO (Voltage Controlled Oscillator) and includes, for example, an inductor L1 and a variable capacitor C1 connected in parallel. When the capacitance of the variable capacitor C1 is changed by the control signal Vo, the frequency fo of the oscillation signal So is changed. The PA <NUM> corresponds to the transmitting unit <NUM> of the first embodiment, amplifies the oscillation signal So, and transmits the amplified signal as a transmission signal Rt from the antenna <NUM>.

The LNA <NUM> corresponds to the receiving unit <NUM> of the first embodiment, amplifies the reception signal Rr received via the antenna <NUM>, and outputs the amplified signal as the reception signal Sr. The mixer 16a mixes the reception signal Rr and the oscillation signal So, and outputs the mixed signal to the differential amplifier 17a via the capacitor C2. The amplifier 17a differentially amplifies the input signal and outputs the amplified signal as an intermediate signal IFI. The phase shifter <NUM> delays the phase of the oscillation signal So by <NUM> degrees. The mixer 16b mixes the reception signal Rr and the phase-shifted oscillation signal So, and outputs the mixed signal to the differential amplifier 17b via the capacitor C2. The amplifier 17b differentially amplifies the input signal and outputs the amplified signal as an intermediate signal IFQ.

The amplifiers 24a, 24b, <NUM>, the HPF 22a, the BPFs 22b and <NUM> correspond to the band separation filter <NUM> of the first embodiment. The BPF 22b suppresses the high and low frequency components of the intermediate signal IFI. The BPF 22b allows a signal of, for example, <NUM> to <NUM> to pass through and suppresses other signals. The amplifier 24b amplifies the filtered signal and outputs the amplified signal as an intermediate signal IF1. The HPF 22a suppresses the low frequency component of the intermediate signal IFI. The HPF 22a allows, for example, a signal of <NUM> or higher to pass through. The amplifier 24a amplifies the filtered signal and outputs the amplified signal as an intermediate signal IF2. The BPF <NUM> suppresses high frequency components and low frequency components of the intermediate signal IFQ. The BPF <NUM> passes a signal of <NUM> to <NUM>, for example, and suppresses other signals. The amplifier <NUM> amplifies the filtered signal and outputs the amplified signal as an intermediate signal IFQ.

The MUX <NUM> outputs the intermediate signal IF1 to the ADC 38a in the period <NUM> and outputs the intermediate signal IF2 to the ADC 38a in the period <NUM> according to an instruction from the detection unit <NUM>. The ADC 38a samples the intermediate signal IF1 and converts it into a digital signal in the period <NUM> and samples the intermediate signal IF2 and converts it into a digital signal in the period <NUM> according to an instruction from the detection unit <NUM>. The ADC 38b samples the intermediate signal IFQ and converts it into a digital signal according to an instruction from the detection unit <NUM>. Sampling of the intermediate signals IF1 and IFQ corresponds to sampling SP1 in the first embodiment. Sampling of the intermediate signal IF2 corresponds to sampling SP2 in the first embodiment. The ADCs 38a and 38b output the converted digital signals to the detection unit <NUM>. Other configurations are the same as those of the first embodiment.

<FIG> is a timing chart of the detection device according to the second embodiment. Fo denotes the frequency of the oscillation signal So, So denotes the voltage of the oscillation signal, IFI denotes the voltage of the intermediate signal IFI, and IFQ denotes the voltage of the intermediate signal IFQ.

The frequency fo0 in the period <NUM> can be switched to a plurality of channels. For example, when a plurality of detection devices <NUM> are used in the same place (for example, in the same room), the frequency fo0 of the oscillation signal So output from each detection device <NUM> is changed so that the transmission signals of the plurality of detection devices <NUM> do not interfere with each other. Fmax is the highest frequency fo0 among the plurality of channels, and fmin is the lowest frequency fo0 among the plurality of channels. The frequencies fo1 and fo2 in the period <NUM> are common to the plurality of detection devices <NUM>. Since the period <NUM> is very short, even if the frequencies fo1 and fo2 are common to the plurality of detection devices <NUM>, an interference between the detection devices <NUM> hardly occurs. The solid lines of IFI and IFQ correspond to IFI and IFQ when fo0 is fmax, and the dashed lines of IFI and IFQ correspond to IFI and IFQ when fo0 is fmin.

The period <NUM> between the times t21 and t22 is a period for changing the frequency fo from fmax to fo1 or from fmin to fo1. The period <NUM> between the times t31 and t32 is a period for changing the frequency fo from fo1 to fmax or from fo1 to fmin. The periods <NUM> and <NUM> are periods until the signal whose frequency fo is changed becomes stable.

By comparing the IFI with the IFQ, it can be determined whether the object <NUM> is away from or closer to the detection device <NUM>. In the example of <FIG>, in the period <NUM>, IFQ lags IFI by a period T3. In this case, it can be determined that the object <NUM> is closer to the detection device <NUM>. When the IFQ is ahead of the IFI, it can be determined that the object <NUM> is away from the detection device <NUM>. Thus, by using the IFI and I and IFQ, the detection unit <NUM> can determine whether the object <NUM> is closer to or away from the detection device <NUM>.

<FIG> is another example of a timing chart of the detection device according to the second embodiment. In the period <NUM>, the frequency fo rises from fo1 to fo2, and the period <NUM> ends. Therefore, the difference between the voltage at time t21 and the voltage at the end of period <NUM> of IFI and IFQ whose voltages change according to the sweep waveform of oscillation signal So becomes large. Therefore, even if the frequency fo is stabilized to fmax or fmin at time t32, a period <NUM> between time t32 and time t9 is required until the voltages of IFI and IFQ return to the voltage at time t21 and stabilize.

On the other hand, in <FIG>, in the period <NUM>, the frequency fo of the transmission signal is swept from the first frequency fo1 to the second frequency fo2, and then swept from the second frequency fo2 to the first frequency fo1. As a result, the frequency of the oscillation signal So at time t31 returns to the frequency at time t21. Therefore, the period from time t31 until the voltages of IF1 and IF2 return to the voltages at time t21 can be shorter than that in the case of <FIG>, and the voltages of IFI and IFQ are stabilized during the period <NUM>. Therefore, the detection by the Doppler method can be resumed earlier than that in the case of <FIG>.

In the present embodiment, the frequency of the oscillation signal So is swept from fo1 to fo2 during the period from time t22 to time t5, and the frequency of the oscillation signal So is swept from fo2 to fo1 during the period from time t5 to time t31. Therefore, the distance of the object <NUM> can be measured in the period from time t22 to time t5 and in the period from time t5 to time t31. The measurement accuracy of the distance can be improved by averaging the distances measured twice. In the first and second embodiments, an example in which fo2 is higher than fo1 has been described, but fo2 may be lower than fo1.

In any of the above aspects, the various features may be implemented in hardware, or as software modules running on one or more processors/computers.

Claim 1:
A detection device (<NUM>, <NUM>) comprising:
an oscillator (<NUM>) configured to output an oscillation signal (So);
a controller (<NUM>) configured to output a control signal for controlling a frequency of the oscillation signal to the oscillator (<NUM>);
a transmitter (<NUM>) configured to transmit an electromagnetic wave or a sound wave as a transmission signal having the same frequency as the oscillation signal (So);
a receiver (<NUM>) configured to receive a signal obtained by reflecting the transmission signal from an object, as a reception signal;
a mixer (<NUM>, 16a, 16b) configured to mix the oscillation signal and the reception signal and output a mixed signal as an intermediate signal; and
a detector (<NUM>) configured to detect a motion of the object and a distance to the object from the intermediate signal;
characterized in that
when a request (Rq) for distance measurement is not inputted from an external device (<NUM>), the controller controls the oscillator (<NUM>) so as to set the frequency (fo) of the oscillation signal (So) to a constant frequency (fo0), and the detector performs first sampling of the intermediate signal at first sampling times (Sp1) according to a first sampling frequency defined by a first time interval (T1) in a first sampling period (<NUM>) to detect the motion of the object,
when the request (Rq) for distance measurement is input from the external device, the controller controls the oscillator (<NUM>) so as to sweep the frequency (fo) of the oscillation signal (So), and the detector performs second sampling of the intermediate signal, at second sampling times (Sp2) according to a second sampling frequency defined by a second time interval (T2) smaller than the first time interval (T1) in a second sampling period (<NUM>) shorter than the first sampling period (<NUM>) to detect the distance to the object, the second sampling period (<NUM>) being between adjacent first sampling periods (<NUM>), and
the second sampling period (<NUM>) is shorter than the first time interval (T1).