JPH042984A - Range finder - Google Patents

Abstract

PURPOSE:To dispense with two oscillating means and, in addition, an oscillator of high precision to be used for an instrument and thereby to reduce the cost by prohibiting input of an output signal of an oscillating means to either a first or second frequency-dividing means periodically for a prescribed period. CONSTITUTION:A first frequency-divider 4 divides the frequency of an output pulse (a) of an oscillator 2 into 1/8 and outputs a pulse (b) thus obtained to drive a first M-series generator 10. A second frequency-divider 6 divides the frequency of a pulse (c) supplied from a prohibiting means 8 into 1/8 and outputs a pulse (d) thus obtained to drive a second M-series generator 12. An AND gate 820 prohibits the output pulse (a) of the oscillator 2 from being inputted to the second frequency-divider 6 through counters 804 and 806. Every time when the output pulse (a) is counted by fifty-six, in other words, the input pulse to the second frequency-divider 6 is delayed by one clock. According to this constitution, a phase difference occurs between M-series pulses generated by the first and second M-series generating means 10 and 12 and thus a distance to an object of detection can be determined without using two oscillating means.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a distance meter using M-sequence pulses.

[Prior Art] FIG. 3 shows an example of the configuration of distance Ml using conventional M-sequence pulses. Before explaining the configuration and operation of the conventional example shown in this figure, the M-sequence pulse will be explained. M
The sequence pulse is a pulse having pseudo-randomness,
It can be produced by an M-sequence generator consisting of a shift 1-register and an exclusive-OR (EX-OR) gate. The correlation function of M-sequence pulses is defined by the following equation,
It has an extremely sharp peak.

r R(τ) = fo M (,t) M (t-τ)d
t・-・・・・(1) Here, M (1; ) is time t
, T is the period of the M-sequence code, and τ is the amount of delay. To explain the correlation function of this M-sequence pulse using an M-sequence (1101001) with a length of 7 codes as an example, τ
In the case of = 0, M(t) = M(t-τ) = (1101001), so the correlation function R (0 to 1) between 1 and O is 1
and -1 respectively;! When Pi, x) 1
1-1 1-1-1 1 1+1. +1+1-1-1. +l+i,=7=R(0)
becomes.

Next, if there is a deviation of 1 pixel, that is, M(t)=
(110100'') and M(!, -τ) = (101001,],), the correlation function R (1 pip 1-) is 1 1-1 1. -1-1 1 x) 3--1 1-1-4 1 1 L-1-1-1-1-1-1, +1=-L=R(1).

Even if there is a deviation of 2 to 6 bits i between M (with) and M (with -), the correlation function R(τ) will be -1. However, once the 7 bits have passed from 1 to 1, it returns to the original state, so the correlation function becomes 7 again. Therefore, the correlation function of the M sequence of code length L (L is a positive integer) is as shown in FIG. Note that in FIG. 4, Δ indicates the time of one code.

FIG. 5 is a time chart showing signals of various parts of the conventional example shown in FIG. Below, with reference to Figure 5, the third
The conventional example shown in FIG.

The first M-sequence generator 10 receives the output of the first oscillator 2A as a clock pulse and generates an M-sequence pulse (2).

This M-sequence pulse P is emitted from the transmitting antenna 14 toward the detection object 16, and its reflected wave is transmitted to the receiving antenna 1.
8, the received M sequence pulse r becomes the received M sequence pulse r and is sent to the multiplier 2.
given to 4.

Further, the M-sequence pulse P is also given to the multiplier 20.

The second M-sequence generator] 2 receives the output of the second oscillator 2B as a tarok pulse and generates an M-sequence pulse q. This M-sequence pulse q is directly applied to multipliers 20 and 24. As is clear from equation (1), the correlation function of two M-sequence pulses can be determined by a combination of a multiplier and an integrator.

That is, the combination of multiplier 20 and integrator 22 transmits M
Generate a correlation function X between the sequence pulse P and the M sequence pulse g,
The combination of multiplier 24 and integrator 26 generates and outputs a correlation function y between received M-sequence pulse r and M-sequence pulse g.

The first and second M-sequence generators 10 and 12 both generate M-sequences with code lengths L and the same pattern. When the frequencies of the output pulses of the second oscillators 2A and 2B are f and fb, f and f are slightly different, and there is a relationship of f < f. Let T be the period of the M-sequence pulse generated by the first M-sequence generator 10, and Tb be the period of the M-sequence pulse g generated by the second M-sequence generator 12.

becomes. Since these two M-sequence pulses P and q have slightly different frequencies, a state where the phases completely match and a state where the phases are shifted are periodically repeated.

Therefore, if the phases of two M-sequence pulses and q match at a certain time t, then the correlation function X is
A peak waveform as shown in FIG. 5 is obtained.

The width 2W of this peak waveform is given by: On the other hand, since the received M-sequence pulse r is emitted from the transmitting antenna 14, reflected by the detection object 16, and further reaches the receiving antenna 18 due to the propagation delay τ according to the distance Q, the correlation function y is When X reaches its peak, it remains -1.

However, after time τ', the phases of the M-sequence pulse 9 and the received M-sequence pulse r match, and the correlation function y reaches its peak. Note that here, Therefore, by opening the time difference τ' between the peaks of the two correlation functions X and y and calculating τ from equation (5), the distance Q to the detected object can be calculated as follows. Note that in equation (6), C is the speed of light.

[Problems to be Solved by the Invention] The conventional distance H1 shown in FIG. 3 requires two oscillators, and as shown in equation (6), the distance 1
The measurement accuracy of 'fol n depends on the frequency accuracy of the two oscillators, and the oscillator frequencies fa and f of 2-]
, must be slightly different, so the two oscillators are required to have high precision, which poses a problem in that the cost 1~ becomes extremely high.

SUMMARY OF THE INVENTION An object of the present invention is to provide a distance meter that uses a 1M sequence pulse, which requires only one oscillator and does not require high oscillator accuracy.

[Means for Solving the Problems] The distance meter of the present invention includes a first
a frequency dividing means, a second frequency dividing means having the same frequency dividing ratio as that of the first frequency dividing means and frequency dividing the output signal of the oscillating means; a prohibition means for periodically prohibiting input of the output signal of the oscillation means to one of the oscillation means for a predetermined period;
The sequence generating means generates M-sequence pulses, and the second M-sequence generating means generates M-sequence pulses in accordance with the output signal of the second frequency dividing means.

[Function] At the distance n1 according to the present invention having the above configuration, input of the output signal of the oscillation means to one of the first and second frequency dividing means is periodically prohibited for a predetermined period. A phase difference occurs in the M-sequence pulses generated by the 2M-sequence generation means, and the distance to the detection object can be determined without using two oscillation means.

[Example] FIG. 1 shows the configuration of an embodiment of the distance n1 of the present invention.

In this embodiment, the code length of the M-sequence code is 7, and the phase of two M-sequence pulses is shifted by 178 pi 1- for each period of the M-sequence consisting of 56 pulses. Note that 1 bit means one code of the M sequence code.

An oscillator 2 (oscillation means) outputs an output pulse (tarok pulse) a of a predetermined frequency. A first frequency divider 4 (first frequency dividing means) consisting of a binary counter receives the output pulse a of the first oscillator 2 at its tarock terminal, and converts the pulse b of the output pulse of the oscillator 2 to a frequency of 1/8 into a first M series. Generator 1.
0 (first M sequence generation means). A second frequency dividing means n (second frequency dividing means) consisting of a binary counter receives the output pulse a of the oscillator 2 at its clock terminal via the inhibiting means 8, and divides the output pulse a of the oscillator 2 into a frequency of 1/8 of the output pulse a of the oscillator. The pulse d is output to the second M-sequence generator]2 (second M-sequence generating means).

The inhibiting means 8 inhibits the input of the output pulse a of the oscillator 2 to the second frequency divider 61\ for 1 period I-time every cycle of the M series, that is, every time 56 pulses a are generated from the oscillator 2. do.

The inhibiting means 8 includes a NOT gate 802 which outputs a pulse e which is an inversion of the output pulse a of the oscillator 2, a binary counter 804 which receives the pulse e at a clock terminal and counts the number of pulses e, and a third gate of this counter 804. A binary counter 806 inputs the signal QD to the counter 1 through the tarlock terminal and receives the number, and the 0th, 1st, and 2nd pins of the counter 804 - signals QA, QB, and Q.
NOT game 1-808 that inverts each C and outputs it.
, 810 and 812, and 808 to these NOT games 1
．． 810 and 812, the third pin 1-signal QD of counter 804, and the O-th and first bit signals QA and QB of counter 806 as inputs. AND
Connected to output g of game 1-814 and output e of NOT game 1-802, output f is connected to counters 804 and 80.
816 to AND game 1 supplied to the clear input of 6,
A N I) NOT to invert the output of game 1-814
gate 818 and an AN1) gate with one input connected to the output of oscillator 2, the other input connected to the output of NOT gate 1-818, and the output connected to the clock input of divider-by-2 6. It has l-820.

NOT Game 1-808.810 and 812 and A
ND gate 814 is provided to detect that counters 804 and 806 have counted 56 output pulses a from oscillator 2.

That is, counters 804 and 806 divide pulse a into 5
When 66 clicks start from 1, the counter 804's 0th, 1st,
2nd and 3rd pits 1 ~ signals QA, QB, QC and Q
D and the Oth and third pins 1 to QA and Q10 of the counter 806 are L, L, II, and H, respectively.
, H, so the output g of AND game 1-814 is ■]
Therefore, 566 pulses a can be detected.

8Nr,) When the output g of the game 1-814 becomes I-1, the output of the NO'r game 1-81847) becomes L4,
A N D signals 1 to 820 prohibit the output pulse a of the oscillator 2 from being input to the second frequency divider 6 .

The first M-sequence generator 10 generates the output pulse b of the first frequency divider 4.
An M-sequence pulse is generated according to the following. A second M-sequence generator 2 generates an M-sequence pulse q according to the output pulse d of the second frequency divider 6. The transmitting antenna 14 (transmitting means) emits M-sequence pulses P toward the detected object 16 . The receiving antenna 18 (receiving means) receives the M-sequence pulse reflected by the detection object 16, and receives the M-sequence pulse reflected by the detection object 16.
It is applied to the multiplier 24 as a sequence pulse r.

Multiplier 20 multiplies M-sequence pulses r and q generated by first and second M-sequence generators 10 and 12. Multiplier 2
4 generates the received M-sequence pulse r and the M-sequence pulse q generated by the second M-sequence generator 12; The correlation function x & small output. The integrator 26 integrates the output of the multiplier 24 and outputs a correlation function y between the M-sequence pulses q and r.

a multiplier 20 and an integrator 22 (first correlation function generating means);
The correlation function X+'l outputted from the multiplier 24 and the integrator 26 (second correlation function generating means) is input to the calculating unit 28 (calculating means) and is calculated.

Note that the first and second M-sequence generators 10 and 12, the transmitting and receiving antennas 14 and 8, the multipliers 20 and 24, and the integrators 22 and 26 are conventional Same as component.

FIG. 2 shows signals of various parts of the embodiment of FIG. 1.

The operation of the embodiment shown in FIG. 1 will be described below with reference to FIG.

The first frequency divider 4 divides the frequency of the output pulse a of the oscillator 2 into
A pulse l whose frequency is divided by /8] is outputted to drive the first M-sequence generator 'O'. The second frequency divider 6 outputs a pulse d obtained by dividing the frequency of the pulse C supplied from the inhibiting means 8 by '/8, and drives the second M-sequence generator 12.

Counters 804 and 806 invert the output pulse a of oscillator 2 by NOT gate 802 and send pulse e to run 1. When 56 pulses e are sent to run 1, counter 804's 0th, 1st, The second and third bits QA, QB, QC and QD are respectively L,
L, H, and the Oth and 1st picks of the counter 806
-Q A and QB become T-1,H. Also, NO
T gates 808, 810 and 812 each receive the L output and output 1-1. Therefore, AND gate 81
4's inputs are all I], and the outputs of games 1 to 814 are g
becomes H. As a result, the output of the NOT game 1-14 becomes L, and the AND game 1-820 prohibits the output pulse a of the oscillator 2 from being input to the second frequency divider 6.

After that, at the same time as the pulse e is raised,
The output f of 816 becomes H, and the counters 804 and 80
6 is reset I~, and the prohibition of inputting the output pulse a of the oscillator 2 to the second frequency divider 6 is canceled.

Therefore, in the embodiment shown in FIG. 1, every time 56 output pulses a of the oscillation Pl:'j2 are counted, the input pulse to the second frequency divider 6 is delayed by one clock. .

As mentioned above, the code length of the M sequence is 7, and the frequency division ratios of the first and second frequency dividers 4 and 6 are 8, so 7
X 8 =56 pulses constitute one cycle of the M sequence. Therefore, for each cycle of the M-sequence, the M-sequence pulse q generated by the second M-sequence generator 12 is shifted in phase by 1/8 bit from the M-sequence pulse generated by the]-th M-sequence generator 10. Then, in the arithmetic unit 28, the correlation function x,
By calculating y, the distance Q to the detection object 16 can be determined as in the conventional example shown in FIG. however,
In the case of the embodiment shown in FIG. 1, Lk (7) is obtained by '2. Here, L is the code length and k is the frequency division ratio.

Therefore, Q can be determined regardless of the oscillation frequency of the divider 2. However, in deriving equation (7), it is assumed that the period of the oscillator 2 is sufficiently small with respect to τ, so the frequency of the oscillator 2 is not completely limited.

In the embodiment shown in FIG. 1, the oscillator 2 to the second frequency divider 6
Although the input of the output pulse of the oscillator 2 is periodically prohibited for a predetermined period of time, the input of the output pulse of the oscillator 2 to the first frequency divider 4 may be prohibited for a predetermined period of time. .

[Effects of the Invention] As described in -1- below, according to the distance it of the present invention, the output signal of the oscillation means is input to either the first or second frequency dividing means periodically for a predetermined period. Since this is prohibited, a phase difference occurs between the M-sequence pulses generated by the first and second M-sequence generating means, and there is no need to use two oscillation means. Oscillators tend to not need to be highly accurate, so
Cost 1- can be greatly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the distance meter of the present invention, FIG. 2 is a block diagram showing signals of each part of the embodiment shown in FIG. 1, and FIG. is the conventional distance n1
FIG. 4 is a waveform diagram showing the correlation function of the M-sequence of the code length. FIG. 5 is a time chart showing the signals of each part of the conventional example shown in FIG. 3. It is. 2. Oscillator, 4, 6... Frequency divider, 8... Prohibition means, 1
0.12...M sequence generator, 14...Transmission antenna, 16...Detection object, 18...Reception antenna, 2o,
24... Multiplier, 22.26... Integrator, 28...
Arithmetic unit.

Claims (1)

[Scope of Claims] Oscillation means for outputting a pulse signal of a predetermined frequency; first frequency division means for frequency dividing the output signal of the oscillation means; and a frequency division unit having a frequency division ratio that is the same as the frequency division ratio of the first frequency division means. a second frequency dividing means for dividing the output signal of the oscillating means, and periodically inputting the output signal of the oscillating means to either one of the first and second frequency dividing means; prohibiting means for prohibiting a period of time; first M-sequence generation means for generating M-sequence pulses according to the output signal of the first frequency dividing means; and second M-sequence generation means for generating M-sequence pulses according to the output signal of the second frequency dividing means. means; transmitting means for transmitting the M-sequence pulses generated by the first M-sequence generating means toward a detection object; receiving means for receiving the M-sequence pulses reflected from the detection object; and the first M-sequence generating means. first correlation function generating means for calculating a correlation function between the M-sequence pulses generated by the M-sequence pulses and the M-sequence pulses generated by the second M-sequence generating means; A second correlation function generation means for calculating a correlation function with the M-sequence pulse generated by the means, and a calculation means for calculating a distance from the output signals of the first and second correlation function generation means to the detected object. distance meter.