JP2007086015A - Range finder, and range finding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a range finder and a range finding method capable of enhancing range finding precision. <P>SOLUTION: This range finder/range finding method is provided with a transmission part 2 for transmitting a radio signal having a pulse at a prescribed period, a reception part 3 for receiving a direct wave 8 transmitted from the transmission part 2 and a reflected wave 9 reflected by an object, a time difference acquisition part 46 for counting an arrival time difference that is a time till reception of the reflected wave 9 after the direct wave 8 is received by the reception part 3, and a distance calculation part 47 for calculating a distance from the range finder 1 to the range-finding object 10, based on the arrival time difference counted by the time difference acquisition part 46. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a distance measuring apparatus using an ultra wide band (UWB) radio signal. And it is related with the ranging method utilized for such a ranging apparatus.

  In recent years, attention has been paid to an ultra wide band (UWB) communication system that performs ultra-wideband communication using a pulse signal sequence composed of pulse signals synchronized with a predetermined cycle timing as one of high-speed wireless transmission systems. Yes. As one aspect of UWB communication, there is known one that performs communication using a pulse signal sequence composed of extremely fine pulse signals such as a pulse width of 1 nsec or less without using a carrier wave. A distance measuring device that measures the distance to an object by using such a pulse signal sequence of UWB communication as a radar pulse is known (see, for example, Patent Document 1).

Such a distance measuring device transmits a UWB radio signal pulse from a transmitting device to an object to be measured, receives a UWB pulse reflected from the object, and calculates the time taken from transmission to reception. By measuring the time, the time required for the wireless signal to reciprocate between the distance measuring device and the object is measured, and the distance from the distance measuring device to the object is calculated based on this reciprocating time.
JP-T 8-511341

  By the way, in the distance measuring apparatus as described above, even if the time measurement is started after transmitting the UWB pulse, the transmitted UWB pulse signal is output to the antenna via a transmission circuit such as an amplifier or a filter. As a result, the round trip time of the radio signal to be measured includes the delay time of such a transmission circuit, and the measurement accuracy of the round trip time of the radio signal is reduced. There was an inconvenience that the accuracy decreased. In particular, when a distance measuring device is used as a wall sensor used to detect pipes and reinforcing bars existing behind the walls of a building, a resolution of, for example, about 1 mm to 10 cm is required as the distance measuring accuracy. There is a great need for distance measurement accuracy improvement in distance devices.

  The present invention has been made in view of such a problem, and an object thereof is to provide a distance measuring device capable of improving distance measuring accuracy. And it aims at providing the ranging method utilized for such a ranging apparatus.

  In order to achieve the above object, a distance measuring device according to the first means of the present invention is a distance measuring device that measures a distance from a predetermined object, and is a wireless device having a pulse at a predetermined cycle. A transmitter that transmits a signal, a radio signal transmitted from the transmitter, a receiver that receives a reflected signal of the radio signal reflected by the object, and a radio signal received by the receiver It is characterized by comprising a time measuring unit that measures the arrival time difference that is the time until the reflected signal is received, and a distance calculation unit that calculates the distance based on the arrival time difference timed by the time measuring unit. .

  Further, in the distance measuring device described above, the timing unit includes a sampling unit that samples a signal received by the receiving unit in a time shorter than a time width of the pulse, and the sampling value sampled by the sampling unit, A time difference acquisition unit that acquires a difference between a timing indicating a radio signal and a timing indicating the reflected signal as the arrival time difference is provided.

  Further, in the distance measuring apparatus described above, the time measuring unit includes a sampling unit that samples the signal received by the receiving unit at a sampling period different from the period of the pulse by a difference time which is a time shorter than the time width of the pulse. A time difference acquisition unit that calculates the arrival time difference based on a difference between a timing indicating the radio signal and a timing indicating the reflected signal in the sampling value sampled by the sampling unit.

  The distance measuring device described above further includes a differential time setting unit that receives the setting of the differential time.

  In the distance measuring apparatus described above, the timing unit further includes an evaluation unit that generates an evaluation value by evaluating the sampling value sampled by the sampling unit for each preset number that continues in time series. The time difference acquisition unit uses the evaluation value generated by the evaluation unit instead of the sampling value.

  In the distance measuring apparatus described above, the evaluation unit generates the evaluation value by averaging the sampling values for each of the consecutive numbers in time series.

  In the distance measuring apparatus described above, the evaluation unit generates the evaluation value by integrating the sampling values for each of the consecutive numbers in time series.

  Further, in the distance measuring device described above, the evaluation unit includes an integrator that integrates the sampling values for each of the consecutive numbers in time series, and uses the integration value of the integrator as the evaluation value. Yes.

  In the distance measuring apparatus, the evaluation unit includes an AD conversion circuit that converts the sampling value into a digital value, and an integration circuit that integrates the digital value generated by the AD conversion circuit. Is used as the evaluation value.

  The distance measuring device described above further includes a number setting unit that receives the setting of the number.

  And the distance measuring method according to the second means of the present invention is a distance measuring method for measuring the distance to a predetermined object, the step of transmitting a radio signal having a pulse at a predetermined period; The step of receiving the transmitted radio signal and the reflected signal of the radio signal reflected by the object, and the arrival time difference that is the time from when the radio signal is received until the reflected signal is received is measured. And a step of calculating the distance based on the measured arrival time difference.

  In the distance measuring apparatus and distance measuring method configured as described above, a wireless signal having a pulse is transmitted at a predetermined period, a transmitted wireless signal and a reflected signal reflected by an object are received, and the wireless signal is received. The arrival time difference, which is the time from when the reflected signal is received, is timed, and the distance to the predetermined object is calculated based on the timed arrival time difference. As a result of not including the delay time in the transmission circuit for transmitting, distance measurement accuracy can be improved.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a block diagram showing an example of the configuration of the distance measuring apparatus according to the first embodiment of the present invention. A distance measuring device 1 shown in FIG. 1 includes a transmission unit 2, a reception unit 3, a signal processing unit 4, a transmission antenna 5, a reception antenna 6, and a display unit 7. The transmission unit 2 is a circuit unit that supplies a signal having a pulse at a predetermined cycle to the transmission antenna 5 and emits a UWB wireless signal from the transmission antenna 5. The transmission unit 2 includes an oscillation circuit 21, a timing control circuit 22, a pulse control circuit 23, a pulse A drive circuit 24, a short pulse generation circuit 25, and a band pass filter (band pass filter) 26 are provided.

  The receiving unit 3 is a circuit unit that receives the direct wave 8 of the UWB wireless signal radiated from the transmitting antenna 5 and the reflected wave 9 (reflected signal) reflected by the distance measuring object 10. A timing control circuit 32, a pulse control circuit 33, a pulse drive circuit 34, a short pulse generation circuit 35, a filter 36, a high frequency amplification circuit 37, and a mixer 38 are provided.

  The signal processing unit 4 measures the arrival time difference that is the time from when the direct wave 8 is received by the reception unit 3 to when the reflected wave 9 is received, and based on the arrival time difference, the distance measurement device 1 performs distance measurement. A circuit unit for calculating the distance to the object 10, which includes a filter 41, an average processing unit 42 (evaluation unit), a number setting unit 43, an integration circuit 44, an AD conversion circuit 45, a time difference acquisition unit 46, and a distance calculation unit 47. Prepare. In this case, the average processing unit 42, the integration circuit 44, the AD conversion circuit 45, and the time difference acquisition unit 46 correspond to an example of a time measuring unit.

  The display unit 7 is configured using, for example, a liquid crystal display device, and displays the distance to the distance measuring object 10 obtained by the signal processing unit 4.

  The oscillation circuit 21 outputs the transmission clock signal CLK to the timing control circuit 22 at the pulse period Tcyc of the transmission pulse. The timing control circuit 22 outputs a timing signal for controlling the pulse generation timing to the pulse control circuit 23 based on the transmission clock signal CLK from the oscillation circuit 21. The pulse control circuit 23 outputs a control signal for causing the pulse drive circuit 24 and the short pulse generation circuit 25 to generate a pulse. For example, the pulse control circuit 23 generates a preset number of pulses in the pulse drive circuit 24 and the short pulse generation circuit 25. Let The pulse drive circuit 24 amplifies the control signal from the pulse control circuit 23 and outputs the amplified signal to the short pulse generation circuit 25.

  The short pulse generation circuit 25 is configured using, for example, a step recovery diode (SRD) or the like, and according to the control signal output from the pulse drive circuit 24, a short pulse having a pulse width for the UWB radio signal of 1 nsec or less, for example, a pulse A short pulse signal having a width of 10 psec to 900 psec is generated. The band pass filter 26 shapes the signal output from the short pulse generation circuit 25 and outputs the signal to the transmitting antenna 5 as a pulse signal A. The transmission antenna 5 radiates a UWB radio signal to the outside according to the pulse signal A output from the bandpass filter 26.

  The oscillation circuit 31, timing control circuit 32, pulse control circuit 33, pulse drive circuit 34, short pulse generation circuit 35, and filter 36 are the oscillation circuit 21, timing control circuit 22, pulse control circuit 23, pulse drive circuit 24, short The pulse generation circuit 25 and the band pass filter 26 are configured in substantially the same manner, and the pulse signal B substantially equal to the pulse signal A is output from the filter 36 to one input terminal of the mixer 38.

  Further, the oscillation circuit 31 outputs a sampling clock signal CLKS indicating the period of the sampling period Ts for sampling the received signal to the timing control circuit 32. Further, the timing control circuit 32 outputs a sampling signal SS indicating the timing for sampling the received signal to the average processing unit 42 in accordance with the sampling clock signal CLKS output from the oscillation circuit 31, the integration circuit 44, and the conversion A control signal indicating the operation timing of the circuit 45 is output.

  The receiving antenna 6 receives the direct wave 8 and the reflected wave 9 and outputs the received signal C to the high frequency amplifier circuit 37. The high frequency amplifier circuit 37 amplifies the reception signal C and outputs it to the other input terminal of the mixer 38. The output signal of the mixer 38 is output as a received signal D to the average processing unit 42 via the filter 41.

  The number setting unit 43 is a setting switch that receives the setting of the number of sampling values that causes the averaging processing unit 42 to perform the averaging process. For example, one or a plurality of dip switches or a rotary switch that is an example of a multi-contact switch is used.

  The average processing unit 42 (sampling unit) samples the output signal of the filter 41 in accordance with the sampling signal SS output from the timing control circuit 32, and sets the number of sampling values set by the number setting unit 43 in chronological order. The voltage is averaged every time, and a voltage indicating the average value is output to the integrating circuit 44.

In this case, in order to receive a UWB short pulse signal having a pulse width of 10 psec to 900 psec with high resolution, the timing control circuit 32 sets an average calculation period Ta that is an average value calculation period in the average processing unit 42 to, for example, 1 psec to 90 psec. The period of the sampling signal SS, that is, the sampling period Ts is set so that For example, if the number of average processes by the average processor 42 is M, Ts = Ta / M. If the average calculation period Ta is 1 psec, the distance resolution in the air is obtained by integrating time and the speed of light, and 1 (psec) × 3 × 10 ⁸ (m / sec) / 2 = 150 (μm). Become. Similarly, if the average calculation period Ta is 10 psec, the distance resolution in air is 3 mm.

  The integration circuit 44 temporarily holds a voltage indicating the average value of the sampling values output from the average processing unit 42 in synchronization with the average calculation cycle Ta, and outputs the voltage to the AD conversion circuit 45. The AD conversion circuit 45 converts the voltage indicating the average value of the sampling values held by the integration circuit 44 into a digital value in synchronization with the average calculation period Ta, and outputs the digital value as the average value data E to the time difference acquisition unit 46.

  The time difference acquisition unit 46 and the distance calculation unit 47 temporarily store, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and data. A RAM (Random Access Memory) and its peripheral circuits are configured to function as a time difference acquisition unit 46 and a distance calculation unit 47 by executing a control program stored in the ROM.

  The time difference acquisition unit 46 acquires the difference between the timing indicating the direct wave 8 and the timing indicating the reflected wave 9 as the arrival time difference based on the average value (evaluation value) of the sampling values output from the AD conversion circuit 45. The distance calculation unit 47 calculates the distance L from the distance measuring device 1 to the distance measurement object 10 based on the arrival time difference acquired by the time difference acquisition unit 46 and causes the display unit 7 to display the distance L.

  Next, the operation of the distance measuring apparatus 1 configured as described above will be described. FIG. 2 is a signal waveform diagram for explaining the operation of the distance measuring apparatus 1. First, the short pulse signal P <b> 1 is generated by the transmitter 2 at a predetermined cycle set in advance, for example, 50 nsec, and is output as the pulse signal A to the transmission antenna 5. Then, the transmission antenna 5 radiates the pulse signal A as a UWB radio signal.

  Then, a part of the UWB radio signal radiated from the transmission antenna 5 reaches the reception antenna 6 directly and is received as the direct wave 8 by the reception antenna 6. Further, another part of the UWB radio signal radiated from the transmission antenna 5 reaches the distance measurement object 10 and is reflected, and is received as a reflected wave 9 by the reception antenna 6.

  Then, the direct wave 8 and the reflected wave 9 received by the reception antenna 6 are output to the reception unit 3 as a reception signal C, amplified and mixed by the reception unit 3, and then output to the signal processing unit 4 as a reception signal D. Further, the received signal D is output to the average processing unit 42 via the filter 41.

  The received signal D is sampled by the average processing unit 42 according to the sampling signal SS from the timing control circuit 32. In FIG. 2, white circles in the received signal D indicate sampling points by the average processing unit 42, and the signal level of the received signal D at the sampling points is acquired as a sampling value by the average processing unit 42. Further, the averaging processing unit 42 averages the sampling values consecutive in time series for each number M set by the number setting unit 43, and outputs a voltage indicating the average value to the integration circuit 44.

  FIG. 2 shows an example in which “5” is set in the number setting unit 43, and the average processing unit 42 averages five consecutive sampling values in a time series order, and a voltage indicating the average value. Is output to the integrating circuit 44.

  Then, a voltage indicating the average value of the sampling values obtained by the average processing unit 42 is temporarily held by the integration circuit 44 in synchronization with the average calculation cycle Ta and output to the AD conversion circuit 45, and the AD conversion circuit 45 45 is converted into a digital value in synchronization with the average calculation period Ta, and is output to the time difference acquisition unit 46 as average value data E.

  Here, as shown in FIG. 2, the reception signal D has a noise superimposed on the signal component, and the signal level is raised or lowered due to the influence of noise or the like. On the other hand, the average value data E has a smooth waveform by averaging the M (5) sampling values by the average processing unit 42, reducing the noise component, and the S / N ratio (signal-to-noise ratio). Can be improved. In this case, for example, if the noise component overlapping the signal component is random noise, it is known that the S / N ratio is improved by approximately the square root of M.

  Thereby, the S / N ratio in the received signal D can be improved, the stability of receiving the UWB radio signal by the receiving unit 3 can be improved, the stability of the ranging operation can be improved, and the ranging accuracy can be improved. .

  Next, the time difference acquisition unit 46 acquires the difference between the timing indicating the direct wave 8 and the timing indicating the reflected wave 9 in the average value data E as the arrival time difference Tx. Specifically, as shown in FIG. 2, the average value data E includes a short pulse signal P1 in the direct wave 8 and a short pulse between the distance measuring device 1 and the distance measuring object 10 in the reflected wave 9. A short pulse signal P2 in the reflected wave 9 delayed by the round trip of the signal P1 is included. The time difference acquisition unit 46 acquires the peak timing of the short pulse signal P1 in the average value data E as the timing T1 indicating the direct wave 8, and the peak timing of the short pulse signal P2 in the average value data E is the reflected wave 9. And the difference between the timing T1 and the timing T2 is calculated as the arrival time difference Tx.

Next, the distance calculation unit 47 calculates the distance L between the distance measuring device 1 and the distance measurement object 10 based on the arrival time difference Tx calculated by the time difference acquisition unit 46. FIG. 3 is an explanatory diagram for explaining a method of calculating the distance L. As shown in FIG. 3, the distance between the center of the transmission antenna 5 and the center of the reception antenna 6 is 2L ₁ , the distance between the center of the transmission antenna 5 and the distance measurement object 10 is L ₂ , and the distance measurement object If the distance between the object 10 and the center of the receiving antenna 6 is L ₂ and the velocity of the radio wave is V, the distance L between the distance measuring device 1 and the object 10 to be measured, that is, the transmitting antenna 5 and the receiving antenna. The distance L from the center point with respect to 6 to the distance measuring object 10 is expressed by the following equation (1).

  Then, the distance L calculated based on the formula (1) by the distance calculation unit 47 is displayed on the display unit 7.

  Thereby, the difference between the timing T1 and the timing T2 in the direct wave 8 and the reflected wave 9 received by the receiving antenna 6 is calculated as the arrival time difference Tx, and the distance L is calculated based on the arrival time difference Tx. Tx does not include the delay time of a transmission circuit such as an amplifier or a filter unlike the distance measuring device according to the background art described above, and therefore, the measurement accuracy of the distance L based on the arrival time difference Tx can be improved. it can.

  In addition, although the time difference acquisition part 46 showed the example which acquires the arrival time difference Tx based on the average value data E obtained by averaging several sampling values by the average process part 42, the sampling by the average process part 42 is shown. The arrival time difference Tx may be acquired using the sampling value of the received signal D as it is without performing the value averaging process.

  In addition, although an example in which the average processing unit 42 samples and averages the received signal D has been shown, for example, only sampling is performed at the position of the average processing unit 42, and the average processing is performed after the integrating circuit 44 or AD. You may make it carry out in the back | latter stage of the conversion circuit 45. FIG.

(Second Embodiment)
Next, a distance measuring apparatus using the distance measuring method according to the second embodiment of the present invention will be described. FIG. 4 is a block diagram showing an example of the configuration of the distance measuring apparatus 1a according to the second embodiment of the present invention. The distance measuring device 1a shown in FIG. 4 is different from the distance measuring device 1 shown in FIG. 1 in the following points. That is, in the distance measuring device 1a shown in FIG. 4, the oscillation circuit 21 is disposed in the receiving unit 3a, and the receiving unit 3a further includes a differential time setting unit 39. The signal processing unit 4 a includes a distance calculation unit 47 a instead of the distance calculation unit 47.

  The difference time setting unit 39 receives a setting of the difference time Td that is the difference between the pulse period Tcyc of the transmission pulse and the sampling period Ts. For example, one or a plurality of dip switches, a rotary switch that is an example of a multi-contact switch, or the like The period of the transmission clock signal CLK output from the oscillation circuit 21 is set to the pulse period Tcyc of the transmission pulse, and the period of the sampling clock signal CLKS output from the oscillation circuit 31 is set to pulse. By setting the cycle different from the cycle Tcyc by the difference time Td, for example, Tcyc + Td, the sampling cycle Ts in the signal processing unit 4 is different from the pulse cycle Tcyc of the transmission pulse by the difference time Td.

  For example, the difference time setting unit 39 sets the oscillation frequency of the oscillation circuit 21 to 20 MHz if the pulse period Tcyc is 50 nsec, and outputs from the oscillation circuit 31 if the difference time Td is set to 1.25 psec. The period of the sampling clock signal CLKS is set to 19.9995 MHz so as to be different from the pulse period Tcyc by 1.25 psec. The differential time setting unit 39 may set the cycle of the sampling clock signal CLKS to, for example, Tcyc−Td.

  The distance calculation unit 47a is different from the distance calculation unit 47 in that the distance L is calculated based on the equation (2) described later instead of the equation (1). Since other configurations and operations are the same as those of the distance measuring apparatus 1 shown in FIG. 1, the description thereof will be omitted, and the characteristic operations of the present embodiment will be described below.

  FIG. 5 is a timing chart for explaining the operation of the distance measuring apparatus 1a shown in FIG. As shown in FIG. 5, the short pulse signal P1 is generated at a predetermined cycle, for example, 50 nsec cycle, by the transmitter 2a according to the cycle of the transmission clock signal CLK output from the oscillation circuit 21, and the pulse The signal A is output to the transmission antenna 5. Then, the transmission antenna 5 radiates the pulse signal A as a UWB radio signal.

  Then, a part of the UWB radio signal radiated from the transmission antenna 5 reaches the reception antenna 6 directly and is received as the direct wave 8 by the reception antenna 6. Further, another part of the UWB radio signal radiated from the transmission antenna 5 reaches the distance measurement object 10 and is reflected, and is received as a reflected wave 9 by the reception antenna 6.

  Then, the direct wave 8 and the reflected wave 9 received by the reception antenna 6 are output to the reception unit 3 as the reception signal C, amplified and mixed by the reception unit 3, and then output to the signal processing unit 4a as the reception signal D. Further, the received signal D is output to the average processing unit 42 via the filter 41.

  On the other hand, in response to the sampling clock signal CLKS output from the oscillation circuit 31, the timing control circuit 32 outputs a sampling signal SS indicating the sampling timing to the average processing unit 42, and the average processing unit 42 samples the received signal D. Is done.

  In FIG. 5, white circles in the reception signal D indicate sampling points by the average processing unit 42, and the signal level of the reception signal D at the sampling points is acquired as a sampling value by the average processing unit 42. In this case, the sampling period Ts is set to a period different from the pulse period Tcyc by the difference time Td by the difference time setting unit 39. For example, if the difference time Td is set to 1.25 psec, Ts = 50 nsec + 1. 25 psec = 50.00125 nsec.

  Then, sampling is performed at a timing shifted by the difference time Td for each pulse period Tcyc by the average processing unit 42. For example, when sampling a pulse having a pulse width of 100 psec, a plurality of periods per one pulse are taken. Sampling is performed at 100 ps / 1.25 psec = 80 points. As a result, it is possible to sample the pulse waveform with a resolution of 1.25 psec while performing sampling with a sampling period of 50.00125 nsec.

  Then, as shown in FIG. 6, the sampling values obtained over a plurality of periods are set by the average processing unit 42 by the number setting unit 43 in the same manner as the average processing in the signal processing unit 4 described above. The sampling values that are continuous in time series for each M are averaged, and a voltage indicating the average value is output to the integration circuit 44. Then, a voltage indicating the average value of the sampling values obtained by the average processing unit 42 is temporarily held by the integration circuit 44 in synchronization with the average calculation cycle Ta and output to the AD conversion circuit 45, and the AD conversion circuit 45 45 is converted into a digital value in synchronization with the average calculation period Ta, and is output to the time difference acquisition unit 46 as average value data E.

  Here, as shown in FIG. 6, in the received signal D, noise is superimposed on the signal component, and the signal level is raised or lowered due to the influence of noise or the like. On the other hand, the average value data E has a smooth waveform by averaging the M (5) sampling values by the average processing unit 42, reducing the noise component, and the S / N ratio (signal-to-noise ratio). Can be improved. Thereby, the S / N ratio in the received signal D can be improved, the stability of receiving the UWB radio signal by the receiving unit 3 can be improved, the stability of the ranging operation can be improved, and the ranging accuracy can be improved. .

  Next, the time difference acquisition unit 46 acquires the peak timing of the short pulse signal P1 in the average value data E as the timing T1 indicating the direct wave 8, and the peak timing of the short pulse signal P2 in the average value data E is the reflected wave. 9 is obtained, and the difference between the timing T1 and the timing T2 is calculated as the arrival time difference Txa.

  Next, based on the arrival time difference Txa calculated by the time difference acquisition unit 46 by the distance calculation unit 47a, the distance L between the distance measuring device 1 and the distance measurement object 10 based on the following equation (2). Is calculated.

  Then, the distance L calculated based on the formula (2) by the distance calculation unit 47a is displayed on the display unit 7.

  Generally, when a signal waveform is acquired by sampling and time is measured based on the signal waveform, the resolution of time measurement is equal to the sampling period. Therefore, in order to obtain a time resolution of 1.25 psec by sampling, it is necessary to perform signal processing by sampling at a sampling frequency of 1.25 psec, that is, 800 GHz. However, in order to perform signal processing by sampling a received signal at a sampling frequency of 800 GHz, it is necessary to operate a signal processing circuit that performs signal processing such as sampling at an operating frequency of 800 GHz or higher, and such high-speed operation. It is not easy to realize a possible signal processing circuit.

  On the other hand, in the distance measuring apparatus 1a, the necessary time resolution can be obtained by performing sampling at a sampling period that is different from the pulse period Tcyc by a difference time Td equal to the pulse period Tcyc and the required time resolution. By sampling a received signal having a pulse period Tcyc of 50 nsec (20 MHz) at a sampling period of 50.00125 nsec (19.9995 MHz), a time resolution of 1.25 psec is obtained. That is, since sampling can be performed with a sampling period longer than the time resolution, the time resolution in the measurement of the arrival time difference Txa is improved while suppressing an increase in the operating frequency of the signal processing unit 4a, and the measurement accuracy of the arrival time difference Txa is improved. As a result of the improvement, it becomes easy to improve the distance measurement accuracy of the distance L.

  Further, since the user can set the differential time Td using the differential time setting unit 39, the ranging resolution can be set for each application, and the application range of the ranging device 1a can be expanded. For example, when the distance measuring device 1a is used as a wall sensor and a distance near the distance measuring device 1a is detected and the distance resolution is required, the difference time Td is decreased and the distance resolution is set higher. When the distance measuring device 1a is used to detect a distant person or object, it is possible to use the distance measuring device 1a by increasing the difference time Td and reducing the distance resolution.

  The differential time setting unit 39 can individually set one or both of the pulse period Tcyc (the period or frequency of the transmission clock signal CLK) and the sampling period Ts (the period or frequency of the sampling clock signal CLKS). The user may set the differential time Td by using the differential time setting unit 39 to set a sampling cycle Ts that differs from the pulse cycle Tcyc by the differential time Td.

  Moreover, although the time difference acquisition part 46 showed the example which acquires arrival time difference Txa based on the average value data E obtained by averaging several sampling values by the average process part 42, the sampling by the average process part 42 was shown. The arrival time difference Txa may be obtained using the sampling value of the received signal D as it is without performing the value averaging process.

(Third embodiment)
Next, a distance measuring apparatus using the distance measuring method according to the third embodiment of the present invention will be described. FIG. 7 is a block diagram showing an example of the configuration of the distance measuring apparatus 1b according to the third embodiment of the present invention. The distance measuring device 1b shown in FIG. 7 is different from the distance measuring device 1a shown in FIG. 4 in the following points. 7 includes an integration circuit 48 (sampling unit and evaluation unit) and an integration operation control unit 49 instead of the average processing unit 42, the integration circuit 44, and the number setting unit 43.

  The integration operation control unit 49, in response to the sampling signal SS output from the timing control circuit 32, an integration start timing signal SS1 that causes the integration circuit 48 to start integration, and an integration end timing signal SS2 that causes the integration circuit 48 to end integration. And an integration reset timing signal SS3 for initializing the integration value of the integration circuit 48 is output to the integration circuit 48, and a predetermined number M of sampling values are integrated by the integration circuit 48. The number M may be settable by a setting switch such as a dip switch.

  The integration circuit 48 samples the output signal of the filter 41 in accordance with the sampling signal SS output from the timing control circuit 32 as in the average processing unit 42 shown in FIG. Then, the integration circuit 48 integrates the sampling values consecutive in the time series order based on the integration start timing signal SS1, the integration end timing signal SS2, and the integration reset timing signal SS3 from the integration operation control unit 49, and the integration value is obtained. The indicated voltage is output to the AD conversion circuit 45.

  The distance measuring device 1b is different in that the integrated voltage by the integrating circuit 48 is used instead of the average processing in the average processing unit 42 in the distance measuring device 1a. Since other configurations and operations are the same as those of the distance measuring device 1a shown in FIG. 4, the description thereof will be omitted, and the characteristic operations of the present embodiment will be described below. FIG. 8 is a timing chart for explaining the operation of the integrating circuit 48 in the distance measuring apparatus 1b. The timing chart shown in FIG. 8 shows an example in which the number M set in the integral operation control unit 49 is 4.

  First, the reception signal D is output from the reception unit 3 a to the integration circuit 48 via the filter 41. The integration circuit 48 starts integration of the reception signal D in synchronization with the rise of the integration start timing signal SS1, stops integration in synchronization with the fall of the integration start timing signal SS2, and holds the integration value. Is done. Further, the integration of the received signal D is started again in synchronization with the rise of the next integration start timing signal SS1 by the integration circuit 48, and the integration is stopped in synchronization with the fall of the integration start timing signal SS2. Is retained.

  Thus, after the start and stop of the integration are repeated M times (four times in FIG. 8) set in the integration operation control unit 49, the integration value of the integration circuit 48 is taken in by the AD conversion circuit 45, It is AD converted and output as integral value data F to the time difference acquisition unit 46, and the time difference acquisition unit 46 acquires the arrival time difference Txa based on the integral value data F instead of the average value data E. Thereafter, the integration value of the integration circuit 48 is initialized based on the integration reset timing signal SS3.

  That is, the time difference acquisition unit 46 only needs to be able to detect a peak in the integral value data F, and thus the integral value data F can be used instead of the average value data E. As a result, the integration circuit 48 can be used in place of the average processing unit 42 that performs the average processing of the sampling values, so that the circuit can be simplified.

  As shown in FIG. 9, the integration operation control unit 49 is not provided, but instead an integration circuit 50 (evaluation unit) configured using a digital adder or the like is provided, and each sampling point obtained by the integration circuit 48 is obtained. After the sampling value at is converted into a digital value by the AD conversion circuit 45, the M sampling values set in the number setting unit 43 are integrated using the integration circuit 50, and the time difference is obtained as the integration value data F. A configuration for outputting to the unit 46 may be adopted. Further, the integrated value in the integrating circuit 50 may be further divided by M and output to the time difference acquisition unit 46 as average value data E.

  In this case, the integration and averaging of the sampling values can be performed by digital calculation, so that the calculation process is easy and the number of integrations can be easily set according to the number M set in the number setting unit 43. It is.

It is a block diagram which shows an example of a structure of the ranging device which concerns on the 1st Embodiment of this invention. It is a signal waveform diagram for demonstrating operation | movement of the ranging apparatus shown in FIG. It is explanatory drawing for demonstrating the calculation method of the distance between objects. It is a block diagram which shows an example of a structure of the ranging device which concerns on the 2nd Embodiment of this invention. It is a timing chart for demonstrating operation | movement of the ranging apparatus shown in FIG. It is a timing chart for demonstrating operation | movement of the ranging apparatus shown in FIG. It is a block diagram which shows an example of a structure of the ranging device which concerns on the 3rd Embodiment of this invention. It is a timing chart for demonstrating operation | movement of the integration circuit shown in FIG. It is a block diagram which shows the modification of the integration circuit shown in FIG.

Explanation of symbols

1, 1a, 1b, 1c Ranging device 2, 2a Transmitter 3, 3a Receiver 4, 4a Signal processor 5 Transmit antenna 6 Receive antenna 7 Display unit 8 Direct wave 9 Reflected wave 21 Oscillator circuit 22 Timing control circuit 31 Oscillator Circuit 32 Timing control circuit 39 Difference time setting unit 42, 42a Average processing unit 43 Number setting unit 44 Integration circuit 45 AD conversion circuit 46 Time difference acquisition unit 47, 47a Distance calculation unit 48 Integration circuit 49 Integration operation control unit 50 Integration circuit

Claims (11)

A distance measuring device for measuring a distance from a predetermined object,
A transmitter that transmits a radio signal having a pulse at a predetermined period;
A reception unit that receives a radio signal transmitted from the transmission unit and a reflected signal in which the radio signal is reflected by the object;
A timing unit that counts an arrival time difference that is a time from when the wireless signal is received by the receiving unit until the reflected signal is received;
A distance measuring device comprising: a distance calculating unit that calculates the distance based on a difference in arrival time measured by the time measuring unit. The timekeeping section is
A sampling unit that samples the signal received by the receiving unit in a time shorter than the time width of the pulse;
The time difference acquisition part which acquires the difference of the timing which shows the said radio | wireless signal, and the timing which shows the said reflected signal in the sampling value sampled by the said sampling part as said arrival time difference is provided. Ranging device. The timekeeping section is
A sampling unit that samples the signal received by the receiving unit at a sampling period different from the period of the pulse by a difference time that is a time shorter than the time width of the pulse;
The time difference acquisition part which calculates the said arrival time difference based on the difference of the timing which shows the said radio | wireless signal in the sampling value sampled by the said sampling part, and the timing which shows the said reflected signal is provided. The described distance measuring device. The distance measuring device according to claim 3, further comprising a difference time setting unit that receives the setting of the difference time. The timekeeping unit further includes an evaluation unit that evaluates the sampling value sampled by the sampling unit for each preset number that is continuous in time series and generates an evaluation value,
The distance measuring device according to any one of claims 2 to 4, wherein the time difference acquisition unit uses an evaluation value generated by the evaluation unit instead of the sampling value. The ranging device according to claim 5, wherein the evaluation unit generates the evaluation value by averaging the sampling values for each of the numbers that are consecutive in time series. 6. The distance measuring apparatus according to claim 5, wherein the evaluation unit generates the evaluation value by integrating the sampling values for each of the consecutive numbers in time series order. The distance measuring device according to claim 7, wherein the evaluation unit includes an integrator that integrates the sampling values for each of the consecutive numbers in time series order, and uses the integration value of the integrator as the evaluation value. apparatus. The evaluation unit includes an AD conversion circuit that converts the sampling value into a digital value, and an integration circuit that integrates the digital value generated by the AD conversion circuit, and uses the integrated value of the integration circuit as the evaluation value. The distance measuring device according to claim 7. The distance measuring apparatus according to claim 5, further comprising a number setting unit that receives the setting of the number. A distance measuring method for measuring a distance to a predetermined object,
Transmitting a wireless signal having a pulse at a predetermined period;
Receiving the transmitted radio signal and the reflected signal of the radio signal reflected by the object;
Measuring the arrival time difference which is the time from when the wireless signal is received until the reflected signal is received;
And a step of calculating the distance based on the time difference of arrival time.

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