JP2011232053A - Distance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand a measurable distance range to both a short distance side and a long distance side while suppressing a prolongation of a measurement period and a manufacturing cost, in a distance measuring device.SOLUTION: In the distance measuring device, power of a composite wave of a transmission wave frequency-swept by a frequency control circuit and a reflected wave is detected, and the detected signal is sampled by an analysis circuit in a specific processing period and a frequency component of the detected signal is analyzed. Then, a distance is calculated on the basis of the analysis result. The frequency control circuit performs sweeps in accordance with each of sweep patterns P1, P2, and P3 different in frequency sweep width from each other. Accordingly, when a distance to an object to be measured is any of short, middle, and long distances, a frequency of the detected signal can be brought within a frequency range analyzable by the analysis circuit, which enables any distance to be measured. Furthermore, in order to expand a measuring range to short/long distance sides, it is unnecessary to prolong the processing period or take, as the analysis circuit, an analysis circuit capable of high-speed operation.

Description

  The present invention relates to a distance measuring device that measures a distance to an object to be measured using radar waves or ultrasonic waves.

  Conventionally, the standing wave method and the FM-CW method are known as techniques for measuring the distance to an object to be measured using radar waves or ultrasonic waves, and distance measuring apparatuses of the respective methods are known. It has been.

  In any type of distance measuring device, the oscillation frequency of the signal source is swept, and a transmission wave having the same frequency as the swept oscillation frequency is radiated to the measurement object, and the transmission wave and the transmission wave are measured. A combined wave with the reflected wave generated by the reflection is detected. Then, the detection signal is amplified, sampled, frequency-analyzed, and the distance to the measurement object is calculated based on the analysis result.

  The difference between the above two methods is how to sweep the frequency of the transmission wave (hereinafter referred to as the transmission frequency). Therefore, in the above two methods, the combined waveform of the transmitted wave and the reflected wave is different, and the detection portion of the combined wave, the analysis content for the detection signal, and the like are also different.

  Hereinafter, the two types of distance measurement techniques will be described in detail. FIG. 8 shows the conventional principle of distance measurement by the standing wave method of the present invention. In the upper diagram in FIG. 8, the horizontal axis of the first quadrant indicates time t, the vertical axis indicates the transmission frequency f, and the horizontal axis of the second quadrant indicates the power p of the standing wave detected at an arbitrary detection point. Represents. The detection point is an arbitrary point on a straight line passing through the transmission wave radiation point and the measurement object.

  In this method, the transmission frequency f is swept so that the transmission frequency f is maintained for a certain period and is increased by a certain width. By this sweep, the transmission frequency f is modulated stepwise (see the first quadrant). The fixed holding period at each frequency f is set to be longer than the time required for the radar wave or ultrasonic wave to travel back and forth between the object to be measured, and for each holding period, The reflected wave whose phase is delayed by the reciprocation interferes, and a standing wave is generated as a synthesized wave.

The standing wave power p at the detection point is periodically increased or decreased according to the sweep of the transmission frequency (see the second quadrant). This principle will be described with reference to FIG. Here, it is assumed that the transmission frequency increases. This increase, the wave number of the transmitted wave W _T and the reflected wave W _R between the detection point D1 and the measurement object T1 is increased, therefore, the wave number of the standing wave W _S is increased, standing waves in the detection point D1 The phase of _WS is displaced. Thus, the amplitude of the standing wave W _S in the detection point D1 changes from A ₁ to A _2, standing wave power p is proportional to the amplitude changes. Therefore, by sweeping the transmission frequency, the phase of the standing wave W _S in the detection point D1 is swept over 2 [pi, standing wave power p will have a periodicity.

  Here, assuming that the fluctuation period of the standing wave power p due to the sweep of the transmission frequency, the distance to the measurement object T1, and the speed of light are Δf, d, and c, respectively, the following relational expression (1) Is established.

  Therefore, the distance d can be calculated by obtaining the fluctuation period Δf. By the way, when the standing wave power p is detected for an arbitrary period, a time series signal of the standing wave power p (hereinafter referred to as standing wave power signal) is obtained, and the standing wave power p is expressed as a time function. Can do. However, since the equation (1) does not include time as a variable, the distance d cannot be calculated only from the standing wave power signal and the equation (1).

Therefore, it is conceivable to convert the above equation (1) into a time domain equation. If the period corresponding to the fluctuation period Δf, the transmission frequency sweep width, and the sweep period are T _p , ΔF, and τ, respectively, the following equation (2) is obtained (see FIG. 8).

When the above equation (1) is substituted into the above equation (2) and the frequency of the standing wave power signal is f _p (= 1 / T _p ), the following equation (3) for the frequency f _p is derived. .

Thus, by measuring the frequency f _p of the standing wave power signal, and the measured value, the sweep width ΔF and sweep time τ which is set in advance, and a speed of light c, by substituting the above equation (3), the distance d can be obtained.

Next, the principle of distance measurement by the conventional and the FM-CW method of the present invention will be described with reference to FIG. Transmission wave W _T in this manner, by successive sweeps by the frequency sweep width ΔF the frequency sweep period tau, which is FM-modulated continuous wave sawtooth (CW wave). Reflected wave W _R is temporally overdue to the transmission wave W _T, the delay time Δt is the time required for radar waves or ultrasound reciprocates space distance d to the object of measurement . Difference in frequency between the reflected wave W _R and transmitted wave W _T This delay. If this frequency difference, that is, the beat frequency is f _b , the following relational expression (4) is established.

Delay Delta] t is, Δt = 2d / c (c : light velocity) and expressed, and substituting this expression in the equation (4), the following equation indicating the relationship between the beat frequency f _b and the distance d (5) determined It is done.

Thus, by measuring the beat frequency f _b, by substituting the above equation (5), it is possible to determine the distance d. The beat frequency f _b can be measured from the composite wave with the transmission wave W _T and the reflected wave W _R.

Figure 11 shows a waveform of the composite wave _{W C.} When the transmission frequency is swept, it occurs beat the composite wave W _C, the amplitude of the composite wave W _C is increased with a beat frequency f _b, repeat the reduction. Therefore, by detecting the composite wave W _C e.g. envelope, the beat signal from the composite wave W _C, i.e., to extract a beat signal, by measuring the frequency, to obtain a beat frequency f _b The distance d can be calculated from the above equation (5).

Meanwhile, as shown in the above formula (3) and (5) changes according to the distance d from the beat frequency f _b of the frequency f _p and a beat signal of the standing wave power signal, for example, the measurement object The lower the distance, the lower the distance, and the higher the distance. The standing wave power signal / beat signal is generally sampled and discretized by a frequency component analysis circuit (hereinafter referred to as an analysis circuit) during a finite sampling process, and further, these discrete values are high-speed. Fourier transform (FFT) is performed, whereby the frequency f _p of the standing wave power signal / beat frequency f _{b of the} beat signal is measured.

Therefore, in any of the conventional distance measuring devices of the above two methods, if the measurement object is too close to the device, as shown in FIG. 12A, the frequency f _p of the standing wave power signal / beat signal beat frequency f _b is too low, to the sampling period, the standing wave power signal / beat signal one or more wavelengths, it may be impossible to sample. Therefore, the frequency f _p / beat frequency f _b may not be obtained accurately.

On the other hand, when the measuring object is too far from the device, as shown in FIG. 12 (b), the frequency f _{p /} beat frequency f _b is too high, it may become more than half of the sampling frequency. Therefore, the Nyquist sampling theorem is not satisfied, aliasing occurs, and it may be difficult to calculate the frequency f _p / beat frequency f _b with high accuracy.

  That is, as shown in FIG. 13, when the distance from the apparatus to the measurement object is shorter or longer than the distance range corresponding to the frequency range that can be analyzed by the analysis circuit or the like, the distance corresponds to the distance. Even if a standing wave power signal / beat signal with a frequency is obtained, the frequency cannot be measured, and therefore distance measurement becomes difficult. Therefore, there has been a demand to expand the measurable distance range to both the short distance side and the long distance side.

  Therefore, in order to meet the above demand, it is conceivable to increase the sampling frequency and increase the sampling frequency in the analysis circuit. However, when the sampling process period is long, the period required for measurement (hereinafter referred to as the measurement period) becomes long. In addition, when the sampling frequency is increased, the amount of calculation becomes enormous and the calculation time becomes longer, and therefore the measurement period becomes longer. To prevent this, a high-performance analysis circuit capable of high-speed calculation is required. This is necessary and increases the manufacturing cost.

  By the way, the frequency of the transmission signal is shifted, the distance to the target object is measured based on the reflected wave reflected by the target object, the frequency shift of the transmission signal is increased if the target object is close, and the frequency shift is decreased if it is far. A distance measurement system that performs re-measurement is known (see, for example, Patent Document 1). In this distance measurement system, by increasing or decreasing the frequency shift, the object to be measured is specialized in a short distance range or a long distance range, and the measurement accuracy of each distance range is improved.

  Further, a radar device is known in which the distance to the measurement object is measured by the FM-CW method, and if the measured distance is less than the reference distance, the distance is measured again by the standing wave method (for example, Patent Document 2). In addition, a transmission signal having three or more types of frequency modulation is divided and radiated, and the received wave reflected by the target is mixed with the transmission signal to generate a beat signal. There is known a radar apparatus that calculates the distance (see, for example, Patent Document 3). However, it is difficult to solve the above problem in the distance measurement system and the radar apparatus.

Special table 2003-505699 gazette JP 2009-058335 A JP 2009-288223 A

  The present invention has been made to solve the above-described conventional problems, and expands the measurable distance range to both the short distance side and the long distance side while suppressing the extension of the measurement period and the increase in manufacturing cost. An object of the present invention is to provide a distance measuring device that can perform such a process.

  In order to achieve the above object, a distance measuring device of the present invention includes a frequency sweep unit that sweeps the oscillation frequency of a signal source, and a transmission unit that radiates a transmission wave having a frequency corresponding to the oscillation frequency swept by the frequency sweep unit. A receiving unit that receives a reflected wave generated by reflecting the transmission wave by an object to be measured, a detection unit that detects the power or amplitude of a combined wave of the transmission wave and the reflected wave, and the detection unit. A frequency component analysis unit that samples a detection signal for a specific processing period and analyzes the frequency component, and a distance calculation unit that calculates a distance to the measurement object based on an analysis result by the frequency component analysis unit. In the distance measuring apparatus provided, the frequency sweep unit stores in advance a plurality of sweep patterns having different sweep widths of the oscillation frequency, and among these sweep patterns, a sweep width is stored. From a wide sweep pattern in order, characterized by said sweeping in accordance with the sweep pattern.

  In this distance measuring apparatus, after the frequency sweeping unit starts sweeping according to the sweep pattern, when the distance calculation unit first calculates the distance, the sweeping by the next and subsequent sweep patterns is stopped. Is desirable.

  According to the present invention, the frequency of the detection signal proportional to the distance to the measurement object is set by the frequency component analysis unit regardless of the distance to the measurement object by sweeping according to any of the stored sweep patterns. It can be within the frequency range that can be analyzed. Therefore, the measurable distance range can be expanded to both the short distance side and the long distance side. Moreover, since it is not necessary to extend the processing period of the frequency component analysis unit corresponding to the low frequency detection signal in order to expand the measurement range on the short distance side, it is possible to prevent the measurement period from being extended. In addition, in order to expand the measurement range on the far side, it is not necessary to make the frequency component analysis unit high-performance capable of high-speed calculation corresponding to the high-frequency detection signal, so that the manufacturing cost can be suppressed. Furthermore, it is possible to preferentially measure from a short distance.

1 is an electrical block diagram of a distance measuring device according to a first embodiment of the present invention. The figure which shows the sweep pattern of the transmission frequency in the said apparatus. The figure which shows the relationship between the frequency of the detection signal of standing wave power in the said apparatus, and the distance to a measuring object. The flowchart of the sweep process of the transmission frequency in the said apparatus. The figure which shows the sweep pattern of the transmission frequency of the distance measuring device which concerns on the modification of the said embodiment. The electric block diagram of the distance measuring device which concerns on the 2nd Embodiment of this invention. The figure which shows the sweep pattern of the transmission frequency in the said apparatus. (A) (b) is a figure for demonstrating the distance measurement principle by the standing wave system of the past and this invention. The figure which shows the standing wave power fluctuation | variation in arbitrary points when a transmission frequency rises in the said system. The figure for demonstrating the distance measurement principle by the FM-CW system of the past and this invention The composite waveform figure of the transmission wave and reflected wave in the said system. (A) and (b) are diagrams showing standing wave power signal / beat signal waveforms when a measurement object is too close to the apparatus and too far from the apparatus in the conventional distance measuring apparatus. The figure which shows the relationship between the frequency of the said standing wave power signal / beat signal, and the distance to a measuring object.

Hereinafter, distance measuring devices according to various embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 shows a configuration of a distance measuring apparatus according to the first embodiment. The distance measuring device 1 is a distance measuring device that measures a distance d from the device to the measurement target T1 by a standing wave method.

The distance measuring device 1 includes a signal source 10, a frequency control circuit 11, a band selection circuit 12, and a transmission / reception circuit 13. The frequency control circuit 11 sweeps the oscillation frequency of the signal source 10. The band selection circuit 12 selects any one of a plurality of sweep patterns having different sweep widths of the oscillation frequency. Transceiver circuit 13, a frequency corresponding to the oscillation frequency, specifically, to a transmitting wave W _T is a radar wave or ultrasound having the same frequency as the oscillation frequency. The transmitting and receiving circuit 13, the transmission wave W _T receives reflected waves W _R generated is reflected by the measurement object T1.

The distance measuring apparatus 1 further includes a power detection circuit 14, a time axis conversion circuit 15, an amplification circuit 16, a frequency component analysis circuit (hereinafter referred to as an analysis circuit) 17, and a distance calculation circuit 18. Power detecting circuit 14 detects the power of the standing wave is a composite wave of the transmission wave W _T and the reflected wave W _R. The time axis conversion circuit 15 compresses or expands the time axis of the detection signal from the power detection circuit 14. The amplification circuit 16 amplifies the detection signal whose time axis is compressed or expanded by the time axis conversion circuit 15, and the analysis circuit 17 analyzes the frequency component of the amplified detection signal. The distance calculation circuit 18 calculates the distance d from the analysis result by the analysis circuit 17.

  The signal source 10 is constituted by, for example, a voltage controlled oscillation circuit, and oscillates at a frequency corresponding to the voltage input from the frequency control circuit 11 to the signal source 10, and outputs a signal having the oscillation frequency to the transmission / reception circuit 13. .

Frequency control circuit 11 (constituting the frequency sweep unit) sweeps the oscillation frequency of the signal source 10 by sweeping the input voltage to the signal source 10, thereby, the frequency of the transmitted wave W _T (hereinafter, referred to as transmission frequency ). The frequency control circuit 11 calculates the upper limit value of the oscillation frequency by adding the frequency sweep width of the sweep pattern selected by the band selection circuit 12 to the preset lower limit value at the time of sweeping the oscillation frequency. Then, the frequency control circuit 11 sweeps the oscillation frequency up and down at a constant frequency interval in the range from the lower limit value to the upper limit value, and sets the frequency value for each frequency for a fixed holding period. maintain. This holding period is set longer than the round-trip time by the radar wave or the ultrasonic wave between the transmission / reception circuit 13 and the measurement target T1, and a standing wave having a different frequency is generated for each holding period. In the sweep process, the oscillation frequency may be swept downward. Here, a period required for sweeping the frequency sweep width is referred to as a sweep period.

  The transmission frequency is modulated stepwise as shown in FIG. 8 by the sweep process by the frequency control circuit 11. The frequency interval and the holding period are the same during sweeping by one sweep pattern, but may be different or the same for each sweep pattern. The frequency interval and the holding period are not limited to the example illustrated in FIG.

  The band selection circuit 12 (which constitutes a frequency sweep unit) is constituted by a memory and a microprocessor, and the three types of sweep patterns are stored in advance in this memory. In each sweep pattern, a frequency sweep width and a sweep period are set. The frequency sweep width is different for each sweep pattern and is set according to the distance to be measured. Specifically, the frequency sweep width is set wider as the distance is shorter. The sweep periods of the respective sweep patterns are the same as each other. The microprocessor selects in order from sweep patterns having a wide frequency sweep width among the three types of sweep patterns. The number of types of the sweep patterns is not limited to the above, and the sweep periods of the sweep patterns may be different from each other.

The transmission / reception circuit 13 (transmission unit, reception unit) includes a patch antenna or the like. Transceiver circuit 13 emits the transmission wave W _T having the same frequency as the oscillation frequency whose frequency is swept by frequency control circuit 11 to the measurement object T1. The transmitting and receiving circuit 13, the transmission wave W _T receives reflected waves W _R generated is reflected by the measurement object T1. The signal source 10 and the transceiver circuit 13, are connected to electrically by a signal transmission line 19, such as a microstrip line for propagating a transmission wave W _T and the reflected wave W _R. Since the reflected waves W _R is weak, influence given to the signal oscillation of the reflected wave W _R is the signal source 10 is ignored.

  The power detection circuit 14 (detection unit) is configured by a diode or the like that detects the power of a standing wave at a specific point in the signal transmission line 19. The detection signal from the power detection circuit 14 corresponds to the standing wave power signal, and when the transmission frequency is swept, the detection value varies periodically.

  By the way, even if the frequency sweep width is the same, if the sweep period is changed, that is, if the sweep speed is different, the frequency of the standing wave power signal is changed (see FIG. 8). Therefore, if the distance d is simply calculated from the frequency of the standing wave power signal without performing correction in consideration of the sweep period, the distance d becomes an inaccurate value. Therefore, in order to obtain an accurate value of the distance d, the time axis when the time axis of the standing wave power signal is compressed or expanded at a compression / expansion rate corresponding to the sweep period and the sweep period is the reference sweep period. Correction to convert to axis is required.

  Therefore, the time axis conversion circuit 15 acquires information on the sweep period of the sweep pattern selected by the band selection circuit 12 from the frequency control circuit 11, and uses the detection signal at a compression / expansion rate corresponding to the acquired sweep period. Is compressed / expanded in the time axis direction to perform the above correction. In this correction, the ratio of the sweep period to the reference sweep period is obtained, and the reciprocal of the ratio is used as the compression / expansion rate.

  The amplification circuit 16 amplifies the peak value of the detection signal subjected to time axis conversion by the time axis conversion circuit 15 so as to become a value corresponding to the resolution by the analysis circuit 17.

  The analysis circuit 17 (frequency component analysis unit) measures the frequency of the detection signal by sampling, encoding, and fast Fourier transform (FFT) the detection signal amplified by the amplification circuit 16.

The distance calculation circuit 18 (distance calculation unit) calculates the distance d using the above equation (3) based on the frequency of the detection signal measured by the analysis circuit 17. In this calculation process, the frequency of the detection signal, the frequency sweep width of the sweep pattern selected by the band selection circuit 12, and the reference sweep period are substituted for f _p , ΔF, and τ in the above equation (3), respectively. , The distance d is calculated. When the distance d is first calculated in the sweep using the three types of sweep patterns, the distance calculation circuit 18 sends a notification signal notifying the calculation to the frequency control circuit 11. When the frequency control circuit 11 receives the notification signal in a specific waiting period after the sweep by the sweep pattern, the frequency control circuit 11 stops the sweep by the next and subsequent sweep patterns.

  FIG. 2 shows temporal changes in the transmission frequency swept by the frequency control circuit 11 based on the above three types of sweep patterns. The three types of sweep patterns P1, P2, and P3 have sweep periods that are substantially the same, and have different frequency sweep widths. Therefore, the frequency sweep speeds obtained by dividing the frequency sweep width by the sweep periods are different. . Since the lower limit value of the transmission frequency is constant, the upper limit value of the transmission frequency to be swept is different from each other in sweeping by the sweep patterns P1, P2, and P3. Each sweep pattern P1, P2, P3 has the widest frequency sweep width in the sweep pattern P1, then widens in the order of the sweep patterns P2, P3, and is selected by the band selection circuit 12 in this order. After the sweep by the sweep pattern P1 and after the sweep by the sweep pattern P2, the sweep based on the next sequential sweep pattern is started after the waiting period has elapsed.

By the way, as shown in the above equation (3), when the sweep period τ is constant and the distance d is short or long, the frequency f _p (in this embodiment, power detection is performed) by widening or narrowing the frequency sweep width ΔF. The frequency of the detection signal by the circuit 14) can be within a specific frequency range.

  Therefore, in this embodiment, the distance range to be measured is divided into a short distance, a medium distance, and a long distance (hereinafter referred to as a near, medium, and far distance), and the frequency sweep width (ΔF) of the sweep patterns P1, P2, and P3. ) Are set to sweep widths corresponding to the near, middle and far distances, respectively.

  Here, this correspondence will be described. As shown in FIG. 3, when the measurement target T1 is at a short distance from the apparatus, the frequency of the detection signal generated by sweeping the sweep pattern P1 falls within a frequency range that can be analyzed by the analysis circuit 17. As described above, the frequency sweep width of the sweep pattern P1 is set. Further, the frequency sweep width of the sweep pattern P2 is set so that the frequency of the detection signal generated by the sweep of the sweep pattern P2 is within the frequency range when the measurement target T1 is at an intermediate distance. . Further, the frequency sweep width of the sweep pattern P3 is set so that the frequency of the detection signal generated by the sweep of the sweep pattern P3 falls within the frequency range when the measurement target T1 is at a long distance. .

  Next, the transmission frequency sweep process in the frequency control circuit 11 will be described with reference to FIG. 4 in addition to FIG. FIG. 4 shows the procedure of the sweep process. The frequency control circuit 11 sets the variable i to 1 (S1), starts sweeping according to the sweep pattern Pi (S2), and receives the notification signal from the distance calculation circuit 18 within the waiting period thereafter ( (Yes in S3), the sweep by the next and subsequent sweep patterns is stopped (S4). After the sweep by the sweep pattern Pi, if the notification signal is not received within the waiting period (No in S3) and the variable i is not 3 (No in S5), the frequency control circuit 11 increments the variable i. (S6), and the process returns to S2. If the variable i is 3 in the process of S5 (Yes in S5), the sweep is terminated.

  In the distance measuring apparatus 1 of the present embodiment, the frequency of the detection signal proportional to the distance d is obtained by sweeping according to any of the sweep patterns P1, P2, and P3, and the distance d is short distance, medium distance, or far distance. Regardless of the distance, it can be within the frequency range that can be analyzed. Therefore, the measurable distance range can be expanded to both the short distance side and the long distance side. In addition, since it is not necessary to extend the processing period of the analysis circuit 17 in response to the low-frequency detection signal in order to expand the measurement range on the short distance side, it is possible to prevent the measurement period from being extended. Further, in order to expand the measurement range on the long distance side, it is not necessary to make the analysis circuit 17 high-performance capable of high-speed calculation in response to the high-frequency detection signal, and the amplifier circuit 16 is compatible with high-frequency. Since it is not necessary to make it into a thing, manufacturing cost can be held down.

  Moreover, it can measure preferentially from a short distance. Moreover, the distance range of the measurement object is divided into a short distance, a middle distance, and a long distance, and the sweep patterns P1, P2, and P3 correspond to these distances, respectively, so that the measurement accuracy of each distance is improved. Can do.

  Further, when the distance d to the measurement object is calculated (first) by the transmission frequency sweep according to the current (in order) sweep pattern, the sweep based on the next and subsequent sweep patterns is stopped and the measurement is performed. The distance to the object is fixed at the calculated distance d. Therefore, the time required for distance measurement can be shortened and the power consumption required for distance measurement can be reduced.

  The distance measuring device 1 of the present embodiment can be applied to, for example, a back sensor or a corner sensor that is mounted on a vehicle and measures the distance between the rear portion of the vehicle or a corner and an obstacle (measurement object) such as a wall. it can. In the distance measuring apparatus 1, since the distance to the measurement object is measured with priority from a short distance, an obstacle at a short distance of the vehicle can be detected earlier than an obstacle at a long distance. Therefore, when the notification circuit for notifying the user of the measurement result by the distance measuring device 1 with sound or light is provided in the vehicle, the notification circuit can quickly notify the presence of an obstacle at a short distance. Therefore, the period until the user recognizes an obstacle at a short distance can be shortened, and the possibility of collision between the vehicle and the obstacle can be reduced.

(Modification of the first embodiment)
FIG. 5 shows temporal changes in the transmission frequency in the distance measuring apparatus 1 according to a modification of the first embodiment. The frequency control circuit 11 repeats the sweep pattern selected by the band selection circuit 12 a plurality of times, for example, three times for each sweep pattern. The frequency control circuit 11 provides the waiting period during each of these times and also during sweeping by each sweep pattern, and when the notification signal is received during these waiting periods, Then, the sweep by the next and subsequent sweep patterns is stopped.

  In the above modification, the sweep of the transmission frequency by the sweep pattern is repeated for each sweep pattern, so that measurement omission is unlikely to occur, and therefore the reliability of distance measurement can be improved. Also in this modified example, effects equivalent to the various effects obtained by the distance measuring device of the first embodiment can be obtained. This modification can also be applied to a vehicle.

(Second Embodiment)
FIG. 6 shows a configuration of a distance measuring apparatus according to the second embodiment. This distance measuring device 1 is a distance measuring device that measures the distance d by the FM-CW method.

  The distance measuring device 1 includes a signal source 20, a frequency control circuit 21, a band selection circuit 22, a transmission / reception circuit 23, a beat signal component detection circuit (hereinafter referred to as a beat detection circuit) 24, an amplification circuit 25, a frequency A component analysis circuit (hereinafter referred to as an analysis circuit) 26, a distance calculation circuit 27, and a signal transmission line 28 are provided.

  The signal source 20, the band selection circuit 22 (which constitutes a frequency sweep unit), the transmission / reception circuit 23 (transmission unit, reception unit), and the signal transmission line 28 are the signal source 10 and the band selection circuit of the first embodiment, respectively. 12, the transmission / reception circuit 13, and the signal transmission line 19. The band selection circuit 22 stores in advance three types of sweep patterns equivalent to the band selection circuit 12. The number of types of sweep patterns is not limited to the above.

The frequency control circuit 21 (which constitutes a frequency sweep unit) sweeps the oscillation frequency of the signal source 20 by sweeping the input voltage to the signal source 20, and thereby sweeps the transmission frequency. The frequency control circuit 21 calculates the upper limit value of the oscillation frequency by adding the frequency sweep width of the sweep pattern selected by the band selection circuit 12 to the preset lower limit value at the time of sweeping the oscillation frequency. Then, the frequency control circuit 21 continuously sweeps up and sweeps the oscillation frequency in the range from the lower limit value to the upper limit value. By this sweep process, the transmission frequency is modulated in a sawtooth shape as shown in FIG. This modulation, the composite waveform of the reflected wave W _R and transmitted wave W _T becomes a waveform shown in FIG. 11, the composite wave including a beat signal. In the sweep process, the oscillation frequency may be swept downward.

  The beat detection circuit 24 (detection unit) detects the amplitude of the combined wave at a specific point in the signal transmission line 28, that is, detects an envelope of the combined wave, and extracts an beat signal from the combined wave. Etc.

  The amplification circuit 25 (amplification unit) and the analysis circuit 26 (frequency component analysis unit) apply the processing to the standing wave power detection signal by the amplification circuit 16 and the analysis circuit 17 to the beat signal, respectively.

The distance calculation circuit 27 (distance calculation unit) calculates the distance d using the above equation (5) based on the frequency of the detection signal measured by the analysis circuit 26. In this calculation process, f _b of formula _(5), [Delta] F, to tau, respectively, of the beat signal frequency (beat frequency), the frequency sweep width of the sweep pattern selected by the band selection circuit 12, the sweep pattern The sweep period is substituted and the distance d is calculated. The distance calculation circuit 27 has a function of sending a notification signal in the same manner as the distance calculation circuit 18 of the first embodiment, and the frequency control circuit 21 is the same as the frequency control circuit 11 of the first embodiment. Has a function of stopping the sweep based on the reception of the notification signal (see FIG. 4).

  FIG. 7 shows temporal changes in the transmission frequency swept by the frequency control circuit 21 based on the above three types of sweep patterns. In the sweep process shown in FIG. 2, the transmission frequency is modulated stepwise, whereas in the sweep process shown in FIG. 7, the transmission frequency is continuously swept by the frequency control circuit 21 and is linear. Is modulated.

  Also in the distance measuring device 1 of the present embodiment, various effects equivalent to those of the first embodiment can be obtained. Note that this embodiment can also be applied to a vehicle, as in the first embodiment.

  In addition, this invention is not limited to the structure of the said 1st Embodiment, its modification, and 2nd Embodiment, According to the intended purpose, various deformation | transformation are possible. For example, in the oscillation frequency sweeping process by the frequency control circuit 11 or the frequency control circuit 21, an arbitrary oscillation frequency may be set as the center or upper limit of the frequency sweep width, and the oscillation frequency may be swept using the center or upper limit oscillation frequency as a reference. Good. Further, the band selection circuit 12 or the band selection circuit 22 may sweep in accordance with the sweep pattern in order from the sweep pattern having the highest sweep speed among the sweep patterns P1, P2, and P3. Further, the transmission / reception circuit 13 may be a horn antenna, a waveguide may be used instead of the signal transmission line 19, and the power detection circuit 14 may be configured by a directional coupler. Moreover, you may combine the said modification and the said 2nd Embodiment.

1 Distance measuring device 10, 20 Signal source 11, 21 Frequency control circuit (configures a frequency sweep unit)
12, 22 Band selection circuit (constitutes frequency sweep unit)
13, 23 Transceiver circuit (transmitter, receiver)
14 Power detection circuit (detection unit)
17, 26 Frequency component analysis circuit (frequency component analysis unit)
18, 27 Distance calculation circuit (distance calculation unit)
24 Beat component detection circuit (detection unit)
P1, P2, P3 sweep pattern

Claims (2)

A frequency sweep unit that sweeps the oscillation frequency of the signal source;
A transmitter that radiates a transmission wave having a frequency corresponding to the oscillation frequency swept by the frequency sweep unit;
A receiving unit that receives a reflected wave generated by reflecting the transmission wave by a measurement object;
A detector that detects the power or amplitude of the combined wave of the transmitted wave and the reflected wave;
Sampling a detection signal by the detection unit for a specific processing period and analyzing the frequency component;
In a distance measuring device comprising: a distance calculating unit that calculates a distance to a measurement object based on an analysis result by the frequency component analyzing unit;
The frequency sweep unit previously stores a plurality of sweep patterns having different sweep widths of the oscillation frequency, and sweeps according to the sweep pattern in order from a sweep pattern having a wide sweep width among the sweep patterns. A distance measuring device characterized by being characterized.   The frequency sweep unit, after starting sweeping according to the sweep pattern, when the distance calculation unit first calculates a distance, the frequency sweep unit stops sweeping by the next and subsequent sweep patterns. The distance measuring device described in 1.

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