JP7151466B2 - rangefinder - Google Patents

Description

The present disclosure relates to a ranging device that measures a distance to a target device.

Distance measuring devices that measure the distance to a target device are used in various fields, and their uses are under investigation. For example, it is mounted on a vehicle and used to measure the distance to surrounding vehicles. It is also used, for example, to measure the distance between a radio base station and a mobile terminal. Further, for example, it is being considered to measure the distance from the vehicle to a smart key, which is installed in a vehicle and configured by a dedicated key, a smartphone, or the like. In Cited Document 1, a distance measuring device is applied to a mobile terminal in order to measure the position of the mobile terminal, and a plurality of distance measurement signals with mutually different frequencies transmitted from a plurality of fixed stations (base stations) are used. A method for locating a mobile terminal is disclosed. Specifically, for each fixed station, the distance from each fixed station is measured using the phase difference of a plurality of distance measurement signals having mutually different frequencies, and the position is determined based on the obtained distance from each fixed station. A method of identifying is disclosed.

JP 2003-207557 A

In the method of transmitting a plurality of signals with different frequencies and measuring the distance based on the phase difference between these signals, as in the distance measurement method of Patent Document 1, the transmitted signal for distance measurement (hereinafter referred to as "measurement range signals") can be received as multipath propagated and superimposed signals. For example, the ranging signal can be received as a signal wave in which a direct wave that propagates directly from the ranging device to the target device and a ground reflected wave that propagates after being reflected by the ground are superimposed. For this reason, depending on the distance between the distance measuring device and the target device, the direct wave and the ground reflected wave interfere with each other, which lowers the signal reception level and causes variations in the distance measurement results, resulting in low reliability. There is a problem that the distance is measured by

Note that multipath is not limited to waves reflected from the ground, and may include reflected waves from various objects existing between the rangefinder and the target device. distance may be measured with low reliability. Therefore, there is a demand for a technique capable of suppressing deterioration in the reliability of ranging results when ranging signals are received through multipaths.

The present disclosure can be implemented as the following forms.

A ranging device (10) is provided for measuring the distance to a target device (20). This ranging device comprises a ranging signal receiver (112) for receiving a plurality of ranging signals composed of a plurality of signals of different frequencies transmitted from the target device, and the plurality of received ranging signals. A distance calculation unit (116) that calculates the distance using the phase difference of the distance, and a low reliability that specifies whether the distance calculated by the distance calculation unit is in a low-reliability situation where variations may occur. and a ranging signal retransmission requesting section (115) requesting the target apparatus to retransmit the plurality of ranging signals when the low reliability status is identified. Prepare. The ranging signal retransmission request unit, when determined to be in the low-reliability situation, a frequency group different from the first frequency group (fL, fH) of the plurality of ranging signals already received. and requests the target device to transmit the plurality of ranging signals composed of signals of a second frequency group (fL+Δf, fH+Δf) different from each other.

According to the distance measuring device of the above aspect, when it is determined that the reliability is low and the distance calculated by the distance calculation unit may vary, the first distance measurement signal of the plurality of distance measurement signals already received Since the target device is requested to transmit a plurality of distance measurement signals including signals of the second frequency group that is different from the frequency group, deterioration of the distance measurement result can be suppressed. A plurality of ranging signals composed of signals of the second frequency group different from each other are transmitted from the target device in response to such a request, and propagation path loss and received signals are reduced when the ranging signals are received through multipaths. This is because the strength may be improved compared to receiving a plurality of ranging signals consisting of signals of the first frequency group.

The present disclosure can also be implemented in various forms other than the rangefinder. For example, it can be realized in the form of a vehicle control device, a vehicle system, a distance measurement method, a computer program for realizing such a method, a storage medium storing such a computer program, or the like.

1 is an explanatory diagram showing a schematic configuration of a vehicle system including a distance measuring device as one embodiment of the present disclosure; FIG. 3 is a block diagram showing the functional configuration of the distance measuring device; FIG. 4 is a flow chart showing the procedure of distance measurement processing according to the first embodiment; 4 is a flow chart showing the procedure of a distance measurement routine according to the first embodiment; FIG. 4 is an explanatory diagram showing an example of propagation path loss when a ranging signal is received by multipath; 9 is a flow chart showing the procedure of distance measurement processing according to the second embodiment; 11 is a flow chart showing the procedure of distance measurement processing according to the third embodiment; 10 is a flow chart showing the procedure of a ranging routine according to the third embodiment;

A. First embodiment:
A1. Device configuration:
A vehicle system 400 shown in FIG. 1 is a system that realizes remote keyless entry by wirelessly communicating with a distance measuring device 10 as a so-called vehicle-mounted device mounted in a vehicle 500 and a portable device 20 as an electronic key. be. Remote keyless entry means that when the user of the vehicle 500 operates the operation unit 25 of the portable device 20, the doors of the vehicle 500 are opened, unlocked, locked, etc., according to the operation. Note that smart entry may be implemented instead of or in addition to remote keyless entry. Smart entry means that when the user of the vehicle 500 carries the portable device 20 and enters an area in the vicinity of the vehicle 500 where wireless communication is possible, the doors of the vehicle 500 are unlocked, or the user pulls out the portable device 20 . It means that the vehicle 500 is started by operating a predetermined switch while sitting in the driver's seat while carrying. The distance measuring device 10 functions as an in-vehicle device for remote keyless entry, and also functions as a device for measuring the distance between the vehicle 500 and the portable device 20 . In this embodiment, the portable device 20 corresponds to a subordinate concept of the target device in the present disclosure.

The distance measuring device 10 and the portable device 20 transmit and receive LF (Low Frequency) band signals (hereinafter referred to as “LF signals”) and UHF (Ultra High Frequency) band signals (hereinafter referred to as “UHF signals”). (called) are sent and received. The LF band means a frequency band from 30 kHz to 300 kHz, for example. Also, the UHF band means a frequency band from 300 MHz to 3 GHz, for example.

Portable device 20 includes control unit 21 , storage unit 22 , LF reception unit 23 , UHF communication unit 24 , operation unit 25 and vibration detection unit 26 . The control unit 21 controls the portable device 20 as a whole. The control unit 21 may be implemented, for example, by having a CPU (not shown) and executing a control program stored in the storage unit 22 in advance. The control unit 21 transmits a plurality of ranging signals each having a different frequency to the ranging device 10 via the UHF communication unit 24 in a ranging process to be described later. Further, in order to realize remote keyless entry, the control unit 21 transmits, for example, the details of the operation performed by the operation unit 25 to the distance measuring device 10 via the UHF communication unit 24 as a UHF signal.

The storage unit 22 includes a non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read-Only Memory), and stores the frequency of the signal received from the distance measuring device 10 in the distance measurement process described later in addition to the control program described above. . The LF receiver 23 receives LF signals. The LF receiver 23 has an antenna and a receiver circuit. The receiving circuit amplifies and encodes the received LF signal, and passes digital data extracted from the received LF signal to the control unit 21 . The UHF communication unit 24 transmits and receives UHF signals. The UHF communication section 24 has an antenna, a receiving circuit, and a transmitting circuit. The receiving circuit amplifies and encodes the received UHF signal, and transfers digital data extracted from the received UHF signal to the control unit 21 . Further, the transmission circuit modulates and amplifies the carrier wave based on transmission data passed from the control unit 21 . The operation unit 25 has switches (not shown) for instructing opening/closing, unlocking, locking, etc. of the doors of the vehicle 500 described above. The vibration detection unit 26 includes a vibration sensor and detects vibrations of the portable device 20 . Specifically, the portable device 20 is configured to be able to detect vibrations that occur when the user of the vehicle 500 carries and moves the portable device 20 . Any type of sensor may be used as the vibration sensor. For example, a contact sensor such as an acceleration sensor and a speed sensor, or a non-contact sensor such as a displacement sensor may be used. The vibration detection unit 26 is electrically connected to the control unit 21, and upon detecting vibration, notifies the control unit 21 of the detection. The control unit 21 includes information indicating “vibration detected” in the distance measurement signal and transmits the distance measurement signal to the distance measurement device 10 when vibration is detected in the distance measurement process to be described later. If no vibration is detected, the control unit 21 includes information indicating “no vibration” in the distance measurement signal and transmits the distance measurement signal to the distance measurement device 10 .

As shown in FIG. 2 , the distance measuring device 10 includes a control device 100 , an LF transmission section 200 and a UHF communication section 300 . The control device 100 controls the distance measuring device 10 as a whole. In this embodiment, the control device 100 is configured by an ECU (Electronic Control Unit), and has a configuration in which a CPU 110 , an EEPROM 120 and a RAM 130 are connected to each other via an internal bus 140 . The EEPROM 120 stores in advance a range finding control program and a vehicle-mounted device program. The CPU 110 develops and executes a ranging control program using the RAM 130, thereby performing a ranging signal transmission requesting section 111, a ranging signal receiving section 112, a vibration detection signal receiving section 113, and a received signal strength measuring section. It functions as a section 114 , a ranging signal retransmission request section 115 , a distance calculating section 116 , a low-reliability situation specifying section 117 and a ranging control section 118 .

The ranging signal transmission request unit 111 transmits a request signal requesting transmission of a plurality of ranging signals to the portable device 20 . As will be described in detail in the range finding process to be described later, in the present embodiment, the portable device 20 transmits two range finding signals made up of signals with different frequencies. The ranging signal receiver 112 receives a plurality of ranging signals transmitted from the portable device 20 . The vibration detection signal receiving unit 113 identifies whether or not the mobile device 20 is vibrating based on the information indicating the presence or absence of vibration included in the ranging signal. Received signal strength measuring section 114 measures the received signal strength indicator (RSSI: Received Signal Strength Indication) of the UHF signal received via UHF communication section 300 . The ranging signal retransmission request unit 115 requests the portable device 20 to retransmit a plurality of ranging signals.

Distance calculation unit 116 measures the distance between vehicle 500 and portable device 20 using the plurality of received ranging signals. More specifically, the distance calculation unit 116 obtains the distance R between the vehicle 500 and the portable device 20 using the following formula (1).
θd=2×π×fd(R/c) (1)
In the above formula (1), fd indicates the frequency difference (difference frequency) between the two ranging signals, θd indicates the phase of the difference frequency fd when the ranging signal is received, and c is the light intensity. Indicates speed.

The low-reliability condition identifying unit 117 identifies whether or not there is a condition in which the distance calculated by the distance calculating unit 116 may vary (hereinafter referred to as “low-reliability condition”). “The calculated distance may vary” means that the obtained distance may vary when transmitting and receiving the ranging signal and calculating the distance based on the obtained ranging signal are executed multiple times. It means that it can occur. In general, the distances calculated in such situations are less reliable. A specific method for determining whether or not the reliability status is low will be described later. A ranging control unit 118 controls overall ranging processing, which will be described later. It should be noted that specific processing executed by each of the functional units 111 to 118 described above will be described in the distance measurement processing described later.

Further, the CPU 110 functions as an authentication unit 119 by deploying and executing a program for the in-vehicle device using the RAM 130 . Authentication unit 119 executes control for realizing remote keyless entry. Specifically, a process of transmitting an LF signal using the LF transmission unit 200, a process of receiving a UHF signal transmitted from the portable device 20 as a response to the LF signal using the UHF communication unit 300, Authentication processing based on the information contained in the received UHF signal, and in the case of authentication success, processing for instructing the ECU for door opening/closing control to unlock the door, open/close the door, and the like are executed.

The LF transmission section 200 transmits an LF signal. The LF transmission unit 200 includes an antenna and a transmission circuit, and modulates and amplifies a carrier wave using transmission data passed from the control device 100 . The UHF communication unit 300 transmits and receives UHF signals. The UHF communication section 300 has the same configuration as the UHF communication section 24 of the portable device 20 described above.

Distance measurement device 10 performs distance measurement processing, which will be described later, thereby suppressing deterioration in the reliability of distance measurement results when the distance measurement signal is received by multipath, while maintaining distance between vehicle 500 and portable device 20. measure the distance between The measured distance between the vehicle 500 and the portable device 20 may be used for various purposes. For example, when the distance becomes shorter than a predetermined threshold value, the light of the vehicle 500 may be turned on or blinked. Further, for example, the longer the distance, the higher the security level of the vehicle 500 may be used.

A2. Ranging process:
The distance measurement process shown in FIG. 3 is executed when the power of the distance measurement device 10 is turned on. The ranging control unit 118 transmits an activation trigger to the portable device 20 via the UHF communication unit 300 (step S105). When the operation unit 25 is not operated, the portable device 20 operates in a power saving mode in which only some functional units are active. Such a power saving mode is also called a sleep mode, and in the present embodiment, the functional unit that accepts the operation of the operation unit 25, the reception of the UHF signal transmitted from the distance measuring device 10, the extraction of information contained in the UHF signal, etc. This is an operation mode in which only the functional unit (for example, the UHF communication unit 24) that performs the function is active, and the LF reception unit 23, the vibration detection unit 26, and the like are inactive. In step S105 described above, the portable device 20 operating in the power saving mode as described above is operated in the normal operating mode, that is, in the mode in which all functional units are active, by the UHF signal serving as an activation trigger. is sent. In the portable device 20 , the control section 21 transmits a UHF signal as a response signal via the UHF communication section 24 upon receiving the UHF signal that serves as the activation trigger.

The ranging control unit 118 sets the counter N to 0 (step S110). Details of the counter N will be described later. The ranging control unit 118 starts the timer T1 (step S115). A timer T1 is a time for measuring the upper limit time for waiting for reception of a UHF signal as a response signal to the activation trigger described above. The ranging control unit 118 determines whether or not there is a response to the activation trigger from the portable device 20 (step S120), and if it is determined that there is no response (step S120: NO), whether the timer T1 has expired. (step S125). If it is determined that the timer T1 has not expired (step S125: NO), the process returns to step S120. On the other hand, if it is determined that the timer T1 has expired (step S125: YES), the ranging control unit 118 resets the timer T1 (step S130), and the process returns to step S105. If the portable device 20 is far from the vehicle 500 and does not receive the UHF signal as the activation trigger transmitted from the range finder 10, the portable device 20 does not transmit a response signal. will expire.

If it is determined that there is a response from the portable device 20 (step S120: YES), a distance measurement routine is executed (step S135). As shown in FIG. 4, in the ranging routine, first, the ranging signal transmission request unit 111 converts the request signal of the lower (Lo side) frequency fL of the two frequencies of the ranging signal as a UHF signal. It transmits via the UHF communication unit 300 (step S205). A "request signal" is a signal for requesting transmission of a ranging signal. In this embodiment, the initial value of frequency fL is 940 MHz. As will be described later, frequency fL can be changed. In the portable device 20 , the control section 21 is configured to transmit, as a UHF signal, a ranging signal having the same frequency as that of the request signal via the UHF communication section 24 upon receiving the request signal. Further, the control unit 21 includes information indicating the presence or absence of vibration in the ranging signal as described above.

In the ranging device 10, the ranging signal receiving section 112 receives the ranging signal of the Lo side frequency fL transmitted from the portable device 20 via the UHF communication section 300 (step S210). At this time, the ranging signal receiver 112 stores in the EEPROM 120 the frequency of the ranging signal (Lo-side frequency fL), the change in phase from the start of reception, and the presence or absence of vibration. In addition, received signal strength measuring section 114 stores the received signal strength of the ranging signal in EEPROM 120 .

In the ranging device 10, the ranging signal transmission request unit 111 transmits the request signal of the higher (Hi side) frequency fH of the two frequencies of the ranging signal as a UHF signal via the UHF communication unit 300. (step S215). In this embodiment, the initial value of frequency fH is 945 MHz. As described below, frequency fH can be changed. In the portable device 20 , when receiving such a request signal, the control section 21 transmits a distance measurement signal of frequency fH on the Hi side as a UHF signal via the UHF communication section 24 .

In the ranging device 10, the ranging signal receiving section 112 receives the ranging signal of the Hi side frequency fL transmitted from the portable device 20 via the UHF communication section 300 (step S220). At this time, the ranging signal receiver 112 stores in the EEPROM 120 the frequency of the ranging signal (Lo-side frequency fL), the change in phase from the start of reception, and the presence or absence of vibration. In addition, received signal strength measuring section 114 stores the received signal strength of the ranging signal in EEPROM 120 .

In the distance measuring device 10, the distance calculation unit 116 calculates the frequency and phase of the ranging signal with the Lo side frequency fL received in step S210 and the frequency and phase of the ranging signal with the Hi side frequency fH received in step S220. is used to calculate the distance between the vehicle 500 and the portable device 20 based on the above equation (1) (step S225). Note that the calculated distance is stored in the EEPROM 120 . After execution of step S225, step S140 is executed as shown in FIG. Note that the two frequencies of the ranging signal used in the ranging routine described above, that is, the Lo-side frequency fL and the Hi-side frequency fH, correspond to a subordinate concept of the first frequency group in the present disclosure.

The low-reliability state identification unit 117 determines whether or not the state is a low-reliability state based on the following criteria (step S140). That is, the low-reliability-status identification unit 117 determines whether or not the following condition (i) or (ii) is satisfied, and if at least one of the conditions is satisfied, the low-reliability status is not determined. judge. On the other hand, if neither condition (i) nor condition (ii) is satisfied, it is determined that "there is a low reliability situation".
(i) the RSSI of the ranging signal is greater than or equal to the strength threshold;
(ii) The ranging signal indicates "vibration detected".

If the RSSI of the ranging signal is less than the strength, the low RSSI condition may be due to multipath signal reception. For example, there is a possibility that a direct wave that propagates directly from the portable device 20 to the vehicle 500 and a ground-reflected wave that propagates after being reflected by the ground interfere with each other, resulting in a low RSSI. In general, the reliability of the distance calculated based on the received ranging signal in such conditions is low. Moreover, when vibration is not detected in the portable device 20, the portable device 20 may remain at the same position. In such a case, since the distance between the portable device 20 and the vehicle 500 does not change, if the RSSI is low due to multipath reception, that situation will continue. Therefore, in the present embodiment, as a case where such a situation can occur, when vibration is not detected in the portable device 20, that is, when the ranging signal indicates "no vibration detected", the reliability is low. I'm trying to judge that there is.

In step S140, if at least one of the conditions (i) and (ii) is satisfied, that is, if it is determined that the reliability is not low (step S140: YES), the ranging control unit 118 The distance measurement result is determined (step S145). That is, the distance calculated in step S225 of the distance measurement routine described above is determined as the distance between the vehicle 500 and the portable device 20. FIG. The ranging control unit 118 transmits an end trigger to the portable device 20 via the UHF communication unit 300 (step S150). In the portable device 20, upon receiving the termination trigger transmitted from the distance measuring device 10, the control unit 21 shifts the operation mode of the portable device 20 from the normal mode to the power saving mode. After executing step S150, the distance measuring device 10 returns to step S105 described above.

In step S140 described above, if neither condition (i) nor condition (ii) is satisfied, that is, if it is determined that the reliability is low (step S140: NO), the ranging signal retransmission request unit 115 sets the frequency obtained by changing the Lo-side frequency fL by Δf as a new Lo-side frequency fL, and sets the frequency obtained by changing the Hi-side frequency fH by Δf as a new Hi-side frequency fH ( step S155). The ranging control unit 118 increments the counter N by 1 (step S160). That is, the counter N is a counter that indicates the number of times step S155 is executed, and more specifically, a counter that counts the number of times that the Lo-side frequency fL and the Hi-side frequency fH are changed by Δf. In this embodiment, Δf is a negative number and is −10 MHz. Note that Δf may be set to any frequency other than −10 MHz.

The ranging control unit 118 determines whether or not the value of the counter N is smaller than a predetermined upper limit number of times X (step S165). If it is determined that the value of the counter N is smaller than the predetermined upper limit number of times X (step S165: YES), the aforementioned distance measurement routine (step S135) is executed. Therefore, in this case, the two frequencies of the ranging signal are each changed by Δf from the previously executed ranging routine. For example, when the number of times is 1, the Lo-side frequency fL is changed from 940 MHz to 930 MHz, and the Hi-side frequency fH is changed from 945 MHz to 935 MHz. executed. Note that the two frequencies of the ranging signal used in the ranging routine to be executed again, that is, the Lo side frequency fL+Δf and the Hi side frequency fH+Δf correspond to a subordinate concept of the second frequency group in the present disclosure.

The reason why the frequency of the ranging signal is changed and the ranging routine is executed again in the low reliability situation as described above will be explained with reference to FIG.

In FIG. 5, the horizontal axis indicates the distance between antennas (m), and the vertical axis indicates the propagation path loss (dB). Note that the distance between antennas on the horizontal axis is the antenna for UHF signal transmission/reception of the portable device 20 (an antenna possessed by the UHF communication unit 24) and the antenna for UHF signal transmission/reception of the distance measuring device 10 (an antenna possessed by the UHF communication unit 300). antenna). Further, in FIG. 5, the thin solid-line curve LN0 indicates the propagation loss (radio signal gain) of the ranging signal when there is no ground reflection, and the thick solid-line curve LN1 and the thick dashed-line curve LN2 both indicate the direct It shows propagation path loss (gain of radio signal) in multipath of wave and ground reflected wave. It should be noted that the curves LN1 and LN2 differ from each other in the frequencies of the ranging signals used. More specifically, the frequency of the ranging signal when curve LN2 is obtained is lower than the frequency of the ranging signal when curve LN1 is obtained.

As shown in FIG. 5, when there is no ground reflection, that is, when only direct waves propagate, the propagation path loss (radio signal gain) gradually decreases as the distance between the antennas increases, as shown by the curve LN0. Become. On the other hand, in the case of multipath signal propagation, the propagation path loss increases or decreases according to the distance between the antennas. For example, on the curve LN1, when the antenna distance is the distance D1, the propagation path loss L1 is minimal within the distance range shown in FIG. , the propagation path loss is greater than the propagation path loss L1. For example, at a distance D2 that is shorter than the distance D1, in other words, at a position closer to the vehicle 500, the propagation path loss L2 is greater than the propagation path loss L1 at the position at the distance D1.

Here, when the propagation path loss (radio signal gain) is low, the received signal strength indicator (RSSI) is low. Therefore, for example, when the portable device 20 exists at a position where the distance between the antennas is the distance D1, the RSSI of the ranging signal becomes a low value, which can be lower than the strength threshold. FIG. 5 schematically shows the propagation path loss threshold Lth corresponding to the intensity threshold in step S140. As shown in FIG. 5, when the portable device 20 is located at a position where the distance between the antennas is the distance D1, the RSSI value of the ranging signal is below the intensity threshold, and step S155 is executed to perform the ranging. Both the signal frequencies fL and fH decrease by Δf. In this case, the propagation path loss changes from the curve LN1, for example, like the curve LN2 in FIG. As a result, when the portable device 20 exists at a position where the distance between the antennas is the distance D1, the propagation path loss becomes the propagation path loss L2 larger than the threshold value Lth. For this reason, the received signal strength of the ranging signal is also greater than or equal to the threshold. Therefore, in the present embodiment, the received signal strength of the ranging signal is increased by changing the frequency of the ranging signal by Δf. He is trying to suppress the deterioration of the reliability of the distance result.

Also, changing the frequency by Δf to change the propagation path loss from the curve LN1 to the curve LN2 corresponds to the change in the distance between the antennas due to the movement of the portable device 20 . Specifically, when the distance between the antennas changes from the distance D1 to the distance D2 without changing the frequency of the ranging signal, the propagation path loss changes from the propagation path loss L1 to the propagation path loss L2. As a result, the propagation path loss exceeds the threshold Lth, and the received signal strength of the ranging signal also exceeds the strength threshold. The case where the inter-antenna distance changes from the distance D1 to the distance D2 means that the portable device 20 approaches the vehicle 500 . In this way, by moving the portable device 20, it is possible to prevent the state in which the received signal strength is low compared to the case where the distance between the antennas remains at the distance D1, and to escape from the low-reliability state. have a nature.

As shown in FIG. 3, when it is determined in step S165 that the value of the counter N is not smaller than the predetermined upper limit number of times X (step S165: NO), the distance measurement control unit 118 resets the counter N. (Step S170), and specify the provisional distance measurement result (Step S175). In this embodiment, in step S175, the distance measurement result with the largest RSSI value among the X measurement results is identified as the provisional distance measurement result. Note that an average value of the X measurement results, the largest value or the smallest value among the X measurement results, or the like may be specified as the provisional distance measurement result. After step S175 is executed, step S145 described above is executed. In step S145, which is executed after step S175, the provisional distance measurement result specified in step S175 is determined as the official distance measurement result.

According to the distance measuring device 10 of the first embodiment described above, when it is determined that the low-reliability situation is such that the distance calculated by the distance calculation unit 116 may vary, A request is made to the portable device 20 to transmit a plurality of ranging signals composed of signals in frequency groups (frequency fL+Δf and frequency fH+Δf) that are different from the frequency group (frequency fL and frequency fH) of the ranging signal. Therefore, it is possible to suppress deterioration of the distance measurement result. In response to such a request, a plurality of ranging signals made up of signals of a frequency group (frequency fL + Δf and frequency fH + Δf) are transmitted from the portable device 20, and the propagation path when such ranging signals are received by multipath This is because loss (radio signal gain) and received signal strength may be improved compared to receiving a plurality of ranging signals composed of signals of frequency groups (frequency fL and frequency fH).

Further, in the ranging device 10, when the received signal strength when a plurality of ranging signals are received is equal to or less than a predetermined strength, the low reliability state is specified. can be specified with high accuracy.

Further, when the portable device 20 receives the request signal from the range finder 10, it transmits a signal having the same frequency as the request signal as the range finder signal. Since the distance measurement signal transmission request section 111 is provided for transmitting a plurality of request signals of frequency fH) to the portable device 20, the frequency of the distance measurement signal can be controlled by controlling the frequency of the request signal. Therefore, the processing load for frequency control in the portable device 20 can be reduced.

Further, when the range finder 10 is identified as being in a low reliability state, the range finder 10 transmits a plurality of request signals of a frequency group (frequency fL+Δf and frequency fH+Δf) to the portable device 20. can control the frequency of the ranging signal. Therefore, the processing load for frequency control in the portable device 20 can be reduced.

B. Second embodiment:
The configurations of the range finder 10 and the vehicle system 400 of the second embodiment are the same as those of the range finder 10 and the vehicle system 400 of the first embodiment. Detailed description is omitted. The distance measurement process of the second embodiment shown in FIG. 6 executes step S110a instead of step S110, and steps S176, S178, S180, S182, S184, S186, S182, S184, S186 instead of steps S140 and S155 to S175. It differs from the distance measurement process of the first embodiment shown in FIG. 3 in that S188, S190, and S192 are executed. Other procedures in the distance measurement process of the second embodiment are the same as those of the distance measurement process of the first embodiment, so the same steps are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the first embodiment, the distance is calculated only once using the same frequency group, for example, the ranging signals of the frequencies fL and fH. . Further, in the first embodiment, the criterion for determining whether or not the reliability state is low is whether or not the above condition (i) or (ii) is satisfied. criteria are used. A specific description will be given below with reference to FIG.

After executing step S105, the ranging control unit 118 sets the counters N1 and N2 to 0 (step S110a). The counter N1 is a counter for counting the number of times the distance measurement is executed without changing the frequency of the distance measurement signal. The counter N2 is the same counter as the counter N of the first embodiment. That is, the counter N2 is a counter for counting the number of times the Lo-side frequency fL and the Hi-side frequency fH are changed by Δf.

After executing the ranging routine (step S135), the ranging control unit 118 determines whether the counter N1 is smaller than the upper limit value Y (step S176). The upper limit value Y may be set to any number of times, such as 10 times, 20 times, or 100 times. If it is determined that the counter N1 is smaller than the upper limit value Y (step S176: YES), the ranging control unit 118 increases the counter N1 by 1 (step S178). After execution of step S178, the process returns to step S135 and the distance measurement routine is executed again. Unlike the first embodiment, when step S135 is executed after steps S176 and S178 are executed, the frequency of the ranging signal is not changed. Therefore, the ranging routine is executed with the ranging signal having the same frequency as that of the previous ranging routine.

If it is determined in step S176 that the counter N1 is not smaller than the upper limit value Y (step S176: NO), the distance measurement control unit 118 resets the counter N1 (step S180). The low-reliability state identification unit 117 determines whether or not the state is a low-reliability state based on the following criteria (step S182). That is, the low-reliability condition identification unit 117 obtains the standard deviation of Y distance measurement results obtained in total, that is, the standard deviation of the distances calculated Y times, and determines whether the standard deviation is smaller than a predetermined threshold. is determined, and when the standard deviation is smaller than the threshold, it is determined that "there is no low-reliability situation". On the other hand, if the standard deviation is equal to or greater than the threshold, it is determined that the state is "low reliability".

When the standard deviation of the Y distance measurement results, ie, the distances calculated Y times, is smaller than the threshold, the variation in the measurement results is small and the reliability of the measurement results is high. On the other hand, if the standard deviation is not smaller than the threshold, the measurement results will vary greatly and the reliability of the measurement results will be low. Therefore, in the second embodiment, whether or not the standard deviation of Y distance measurement results is smaller than a predetermined threshold is used as a criterion for determining whether or not the reliability is low.

If it is determined in step S182 that the standard deviation is lower than the threshold, that is, the low reliability condition is not met (step S182: YES), steps S145 and S150 described above are performed. On the other hand, when the standard deviation is not lower than the threshold, that is, when it is determined that the reliability is low (step S182: NO), the ranging control unit 118 increases the counter N2 by 1 (step S184). ), and it is determined whether or not the incremented counter N2 is smaller than a predetermined upper limit number of times X (step S186). Steps S184 and S186 are similar to steps S160 and S165 of the first embodiment.

When it is determined that the counter N2 is smaller than the predetermined upper limit number of times X (step S186: YES), the ranging signal retransmission request unit 115 changes the frequency obtained by changing the Lo frequency fL by Δf as the new Lo frequency. fL is set, and a frequency obtained by changing the Hi-side frequency fH by Δf is set as a new Hi-side frequency fH (step S188). This step S188 is the same processing as step S155 of the first embodiment. After execution of step S188, the above-described step S135 (distance measurement processing) is executed. Therefore, the distance measurement processing executed in this case differs from the previously executed distance measurement routine in that the two frequencies of the distance measurement signal are each changed by Δf, as in the first embodiment. In this way, distance calculation using the changed frequencies (frequency fL+Δf and frequency fH+Δf) is performed Y times.

In step S186 described above, if it is determined that the counter N2 is not smaller than the predetermined upper limit number of times X (step S186: NO), the distance measurement control unit 118 resets the counter N2 (step S190). A distance result is identified (step S192). This step S192 is the same processing as step S175 of the first embodiment. After execution of step S192, steps S145 and S150 described above are executed.

The range finder 10 of the second embodiment described above has the same effects as the range finder 10 of the first embodiment. In addition, when the standard deviation of the distances calculated Y times is not smaller than a predetermined threshold value, the low-reliability state is identified, so whether the low-reliability state can be identified with high accuracy. .

C. Third embodiment:
The configurations of the range finder 10 and the vehicle system 400 of the third embodiment are the same as those of the range finder 10 and the vehicle system 400 of the first embodiment. Detailed description is omitted. 7 differs from FIG. 3 in that step S140a is executed instead of step S140, step S155 is omitted, and step S167 is additionally executed. It is different from the distance measurement processing of the first embodiment shown. Since other procedures in the distance measurement process of the third embodiment are the same as those of the distance measurement process of the first embodiment, the same procedures are denoted by the same reference numerals, and detailed description thereof will be omitted. Also, the distance measurement routine of the third embodiment shown in FIG. 8 differs from the measurement routine of the first embodiment shown in FIG. Differs from distance routines.

As shown in FIG. 8, in the ranging routine (step S135), the ranging signal transmission request unit 111 transmits a plurality of request signals in the Lo-side frequency group as UHF signals via the UHF communication unit 300 ( Step S205a). The Lo-side frequency group means a total of M frequencies fL1 to fLM. This Lo-side frequency group is a frequency group different from each other, and in this embodiment, is a frequency group having a constant frequency difference from the nearest frequency. Specifically, there are a total of five frequency groups of 940 MHz, 930 MHz, 920 MHz, 910 MHz and 900 MHz. In step S205a, it means that a total of M (five) request signals for each Lo side frequency are transmitted. Having received such multiple transmission requests, the portable device 20 transmits multiple ranging signals in the Lo-side frequency group.

In the ranging device 10, the ranging signal receiving section 112 receives a plurality of ranging signals of the Lo side frequency group fL1 to fLM transmitted from the portable device 20 via the UHF communication section 300 (step S210a). At this time, the ranging signal receiving section 112 stores the frequency of the ranging signal (Lo-side frequency group fL1 to fLM) and the phase change from the start of reception in the EEPROM 120 .

In the ranging device 10, the ranging signal transmission requesting unit 111 transmits a plurality of request signals of the Hi-side frequency group fH1 to fHM as UHF signals via the UHF communication unit 300 (step S215a). This Hi-side frequency group is a frequency group different from each other, and in this embodiment, is a frequency group having a constant frequency difference from the nearest frequency. Specifically, there are a total of five frequency groups of 945 MHz, 935 MHz, 925 MHz, 915 MHz and 905 MHz. Having received such multiple transmission requests, the portable device 20 transmits multiple ranging signals in the Hi-side frequency group.

In the ranging device 10, the ranging signal receiving section 112 receives a plurality of ranging signals in the Hi-side frequency group fH1 to fLM transmitted from the portable device 20 via the UHF communication section 300 (step S215a). At this time, the ranging signal receiving section 112 stores the frequency of the ranging signal (Hi-side frequency group fH1 to fHM) and the phase change from the start of reception in the EEPROM 120 .

As described above, in this embodiment, the Lo-side frequency groups fL1 to fLM are 940 MHz, 930 MHz, 920 MHz, 910 MHz, and 900 MHz, and the Hi-side frequency groups fH1 to fHM are 945 MHz, 935 MHz, 925 MHz, 915 MHz and 905 MHz. Therefore, the distance measurement signal received by the distance measurement device 10 in the distance measurement routine of the present embodiment is a set of mutually different Lo-side frequencies and Hi-side frequencies. It can be said that there are a plurality of sets of ranging signals in which the frequency difference between the two frequencies between sets is equal to each other by 5 MHz. Specifically, the range finder 10 has a first set (940 MHz, 945 MHz), a second set (930 MHz, 935 MHz), a third set (920 MHz, 925 MHz), and a fourth set (910 MHz, 915 MHz). , and the fifth set (900 MHz, 905 MHz), that is, a total of five frequency sets of ranging signals are received in the ranging routine.

The distance calculation unit 116 calculates the distance for each set of frequencies using the phase of the ranging signal (step S225a). That is, the distance is obtained using the phase difference (5 MHz) and the phase of each ranging signal for each of the first to fifth sets of frequencies. Therefore, a total of five calculation results are obtained as the distance between the portable device 20 and the vehicle 500 .

As shown in FIG. 7, after executing the distance measurement routine (step S135), the low-reliability-state specifying unit 117 determines whether or not the low-reliability state exists according to the following criteria (step S140a). That is, the low-reliability condition identification unit 117 obtains a total of M (five) distance measurement results for each frequency set, that is, obtains the standard deviation of the distances calculated five times. It is determined whether or not the standard deviation is smaller than the threshold, and if the standard deviation is smaller than the threshold, it is determined that "there is no low reliability situation". On the other hand, if the standard deviation is equal to or greater than the threshold, it is determined that the state is "low reliability".

If it is determined in step S140a that the standard deviation is less than the threshold, ie, the low reliability condition is not met (step S140a: YES), steps S145 and S150 described above are performed. On the other hand, if the standard deviation is not less than the threshold value, that is, if it is determined that the reliability is low (step S140a: NO), steps S160 and S165 described above are executed.

If it is determined in step S165 that the value of the counter N is not smaller than the predetermined upper limit number of times X (step S165: NO), steps S170 and S175 are executed as in the first embodiment. On the other hand, if it is determined that the value of the counter N is smaller than the predetermined upper limit number of times X (step S165: YES), the ranging signal retransmission request unit 115 changes the Lo side frequency group fL1 to fLM by Δf, respectively. A new Lo-side frequency group fL1+Δf to fLM+Δf is set as a new frequency group on the Lo side, and frequencies obtained by changing the Hi-side frequency group fH1 to fHM by Δf are set as new Hi-side frequencies fH1+Δf to fHM+Δf (step S167). ). After execution of step S167, a distance measurement routine (step S135) is executed.

In the third embodiment, the Lo-side frequency group and the Hi-side frequency group are both five frequency groups, but may be an arbitrary number of frequency groups. Also, the frequency difference between the two frequencies may be different between each frequency set. For example, it may be the first set (940 MHz, 945 MHz) and the second set (930 MHz, 932 MHz).

The range finder 10 of the third embodiment described above has the same effects as the range finder 10 of the first embodiment. In addition, distances are calculated using distance measurement signals of a plurality of sets of frequencies, which are sets of Lo-side frequencies and Hi-side frequencies that are different from each other, and the frequencies are different between the sets. When the standard deviation is not smaller than the predetermined threshold value, the low-reliability condition is specified, so whether the low-reliability condition is specified can be accurately specified.

D. Other embodiments:
(D1) In each embodiment, the distance measuring device 10 functions as an in-vehicle device in remote keyless entry, but it does not have to function as an in-vehicle device. It may be mounted on the vehicle 500 as a device separate from the on-vehicle device. Further, the distance measuring device 10 may be applied to a device other than the vehicle 500. More specifically, the ranging device 10 may be applied to a mobile communication system including a mobile communication terminal and a base station that performs wireless communication with the terminal. . For example, the ranging device 10 may be applied to the mobile communication terminal, and processing for optimizing transmission/reception power may be performed based on the distance calculated by the ranging device 10 . In such a configuration, the base station corresponds to a subordinate concept of the target device in the present disclosure.

(D2) In the first embodiment, the criterion for determining whether or not the reliability status is low was "whether or not (i) condition or (ii) condition is established." The disclosure is not so limited. For example, it may be "whether (i) the condition is satisfied". In such a configuration, it may be determined that the low-reliability state exists when (i) the condition is not satisfied, and that the low-reliability state is not determined when the (i) condition is satisfied. Further, in such a configuration, the processing related to vibration detection of the portable device 20 and the configuration related to vibration detection of the portable device 20 such as the vibration detection unit 26 and the vibration detection signal reception unit 113 may be omitted. Alternatively, for example, it may be "whether (ii) condition is established". In such a configuration, it may be determined that the low-reliability state exists when (ii) the condition is not satisfied, and that the low-reliability state is not determined when the (ii) condition is satisfied. Moreover, in such a configuration, the processing related to the measurement of the received signal strength and the configuration related to the measurement of the received signal strength such as the received signal strength measurement unit 114 may be omitted. It should be noted that it is also possible to determine whether or not the reliability status is low by appropriately combining the determination criteria of each embodiment.

(D3) In the first embodiment, information indicating the presence or absence of vibration was included in the ranging signal, but the present disclosure is not limited to this. Such information may be included in a signal separate from the ranging signal and transmitted to the ranging device 10 . In such a configuration, the distance measurement signal may be transmitted as a distance measurement signal without including any information, in other words, without modulating the carrier wave of the predetermined frequency.

(D4) Instead of the condition (ii) in the first embodiment, any condition that can determine whether the mobile device 20 is moved may be used. For example, in a configuration in which the portable device 20 has a function of identifying the current position and repeatedly transmits information indicating the identified current position to the distance measuring device 10, it is possible to ask whether the current position of the portable device 20 has changed. The condition may be used in place of the (ii) condition.

(D5) In each embodiment, the frequency of the ranging signal is controlled by controlling the frequency of the request signal, but the present disclosure is not limited to this. Aside from the request signal, a signal for designating the frequency of the ranging signal may be transmitted to the portable device 20 as a signal of the designated frequency. Further, for example, the request signal may be transmitted to the portable device 20 including information indicating the designated frequency.

(D6) In each embodiment, the frequency of the request signal and the ranging signal was in the frequency range of 900 MHz to 945 MHz, but may be in any other range of frequencies in the UHF frequency band. Also, the request signal and the ranging signal have been transmitted and received as UHF signals, but may be transmitted and received as LF signals. In such a configuration, a configuration for transmitting the LF signal may be added to the portable device 20 and a configuration for receiving the LF signal may be added to the distance measuring device 10 . Also, signals of frequencies in arbitrary frequency bands other than the UHF band and LF band may be transmitted and received as the request signal and the ranging signal.

(D7) In the first and second embodiments, the change amount (Δf) of the Lo-side frequency fL and the change amount (Δf) of the Hi-side frequency fH that are changed when it is determined that the reliability state is low. were equal to each other, they may alternatively be different values. However, it is required that the changed Lo-side frequency fL and the Hi-side frequency fH are different frequencies. Similarly, in the third embodiment, the change amount (Δf) of the Lo side frequency group fL1 to fLM and the change amount (Δf) of the Hi side frequency group fH1 to fHM may be different values.

(D8) In each embodiment, the distance is calculated using the frequency difference between two mutually different frequencies. good too.

(D9) The ranging device 10 and techniques thereof described in the present disclosure were provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. It may also be implemented by a dedicated computer. Alternatively, the ranging device 10 and techniques described in this disclosure may be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the ranging device 10 and techniques described in this disclosure may be a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. It may also be implemented by one or more dedicated computers configured in combination. The computer program may also be stored as computer-executable instructions on a computer-readable non-transitional tangible recording medium.

The present disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from the scope of the present disclosure. For example, the technical features in each embodiment corresponding to the technical features in the form described in the outline of the invention are used to solve some or all of the above problems, or Substitutions and combinations may be made as appropriate to achieve part or all. Also, if the technical features are not described as essential in this specification, they can be deleted as appropriate.

10 ranging device, 112 ranging signal receiving unit, 115 ranging signal retransmission request unit, 116 distance calculating unit, 117 low reliability situation specifying unit

Claims (8)

A ranging device (10) for measuring a distance to a target device (20),
a ranging signal receiver (112) for receiving a plurality of ranging signals composed of a plurality of signals of different frequencies transmitted from the target device;
a distance calculation unit (116) that calculates the distance using the phase difference of the plurality of received ranging signals;
a low-reliability situation identification unit (117) that identifies whether the distance calculated by the distance calculation unit is in a low-reliability situation in which variations may occur;
a ranging signal retransmission request unit (115) that requests the target device to retransmit the plurality of ranging signals when the low reliability condition is identified;
with
The ranging signal retransmission request unit, when determined to be in the low-reliability situation, a frequency group different from the first frequency group (fL, fH) of the plurality of ranging signals already received. and requesting the target device to transmit the plurality of ranging signals composed of signals of a second frequency group (fL+Δf, fH+Δf) different from each other. The distance measuring device according to claim 1,
further comprising a received signal strength measuring unit (114) for measuring received signal strength when the plurality of ranging signals are received,
The range finder, wherein the low reliability condition identification unit identifies the low reliability condition when the measured received signal strength is less than a predetermined strength threshold. In the distance measuring device according to claim 1 or claim 2,
further comprising a vibration detection signal receiving unit (113) for receiving a vibration detection signal transmitted from the target device, the vibration detection signal indicating the presence or absence of vibration detected by the target device;
The range finder, wherein the low reliability condition identification unit identifies the low reliability condition when the received vibration detection signal indicates that there is no vibration. In the rangefinder according to any one of claims 1 to 3,
The ranging signal receiving unit receives the plurality of ranging signals of the first frequency group a plurality of times,
The distance calculation unit calculates the distance each time the plurality of ranging signals of the first frequency group are received,
The range finder, wherein the low-reliability condition identification unit identifies the low-reliability condition when the standard deviation of the distances calculated a plurality of times is lower than a predetermined threshold value. The distance measuring device according to claim 4,
The ranging signal receiving unit receives the plurality of ranging signals of the first frequency group a predetermined number of times,
The distance calculation unit calculates the distance each time using a phase difference between the plurality of ranging signals of the first frequency group received at that time,
The low-reliability situation identification unit determines, when the standard deviation of the distances calculated for each of the plurality of ranging signals of the first frequency group received each time is lower than the threshold, A ranging device that identifies a low reliability situation. The distance measuring device according to claim 4,
The plurality of ranging signals of the first frequency group are a plurality of sets of two frequencies different from each other, the frequencies being different between each set and the frequency difference between the two frequencies being equal between each set. including a plurality of sets of ranging signals;
The distance calculation unit calculates the distance for each of the plurality of sets using a phase difference between the ranging signals of the two frequencies;
The low-reliability situation identifying unit identifies the low-reliability situation when the standard deviation of the distances calculated for each of the plurality of pairs is lower than the threshold,
The ranging signal retransmission request unit provides a plurality of sets of two different frequencies for the target device when the low reliability situation is identified, and the frequencies are different between the sets. and a plurality of sets of ranging signals having two frequencies in which the frequency difference between the two frequencies is equal between each set and different from the first frequency group, the plurality of ranging signals in the second frequency group A ranging device that claims to be transmitted as a ranging signal. In the rangefinder according to any one of claims 1 to 6,
The target device is configured to transmit a signal having the same frequency as the request signal as the ranging signal when receiving the request signal from the ranging device,
A ranging device, further comprising a ranging signal transmission request unit (111) that transmits the plurality of request signals of the first frequency group to the target device. The distance measuring device according to claim 7,
A ranging device, wherein the ranging signal retransmission request unit transmits a plurality of the request signals of the second frequency group to the target device when the low reliability condition is identified.

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