JP2922702B2 - Ranging system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ranging system, and more particularly, to a ranging system based on a Manchesterized PN signal. For example, positioning systems, sonars,
It is applied to radar and the like.

[0002]

2. Description of the Related Art As a well-known document describing the prior art according to the present invention, there is "Spread Spectrum Communication System" (Mitsuo Yokoyama Science and Technology Publishing Company, 1988, pp. 538-548). Spread spectrum communication is a method of performing communication using a specific pseudo-noise (PN) signal. However, it is possible to measure distance with high accuracy by utilizing the wideband property of a spread spectrum signal and the correlation characteristic of a spread spectrum code. The literature describes a system using a PN signal such as an M-sequence or a JPL code. Also, "Delay Locked Loop for Manchester Coded PN Signal" (Takaaki Hasegawa and three others, IEICE Transactions, Vol.J-73-BI, No.8, pp.663-665 1990) Describes the configuration, various characteristics, advantages, and the like of a delay locked loop when a Manchester-encoded PN signal is used as a spread signal for spread spectrum communication. "Pulse compression multiplexing sonar using real orthogonal pseudo-noise sequences" (Yoshihiro Tanada et al., IEICE technical report, SSTA90-37 1990) uses real orthogonal pseudo-noise sequences as transmission codes. A system for performing distance measurement using a PN signal is described.

[0003] A pulse compression method, which is a method of distance measurement using a sharp autocorrelation function of a pseudo noise signal, is well known and has been applied to radars and sonars. The resolution of the distance measurement is determined by the resolution of the delay time measurement by the autocorrelation pulse, and specifically depends on the correlation pulse width. The autocorrelation pulse width of the PN signal converted into a pseudo-noise code NRZ, which is often used, is about twice the chip length when the code length is sufficiently long. Assuming a constant chip length, the narrower the autocorrelation pulse width, the better the time resolution. Therefore,
Narrow pseudo noise signal having a main lobe width of the correlation function in time resolution improvement was required.

When the chip length is shortened to increase the time resolution, the transmission signal becomes a wide band signal. However, when a relatively short distance is measured using ultrasonic waves, the signal becomes a transmitter. Since the bandwidth of the ultrasonic transducer is not very wide in practice, a method of reducing the bandwidth of the transmission signal without changing the chip length by converting the PN signal into the SSB has been considered. However, when using the NRZ PN signal,
The SSB signal has the problem that the signal has the maximum power at the end of the band, has the maximum gain near the center of the band, does not match the normal transducer characteristic, and the spectrum is distorted due to transmission and reception, and the correlation characteristic is degraded. there were.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and improves the time resolution at the time of delay time measurement by using a Manchesterized PN signal in which a main rope of an autocorrelation function has a length of 2/3 chip. , And also Manchester P
It is an object of the present invention to provide a distance measurement system with less spectrum distortion in transmission and reception even when SSB is used by using N.

[0006]

To achieve the above object, the present invention provides (1)
A ranging signal that transmits a spread signal using a carrier wave such as radio waves, sound waves, or light using a pseudo-noise code, and measures the distance between transmission and reception based on the time delay between the transmission and reception of the reflected wave or direct wave. In the system, the pseudo-noise signal was Manchester-encoded as a spread signal, and (2) the time required for transmission / reception from the correlation output pulse signal obtained using the same Manchester PN signal matching filter on the reception side as on the transmission side. And (3) the receiving side has a PN signal generator for generating the same Manchester PN signal as the transmitting side, and receiving from the PN signal generator A reference signal advanced by １ ／ of the chip length of the PN signal and a reference signal delayed by ３ of the chip length of the PN signal are extracted, and the phase of the reference signal and the received PN signal is extracted. The distance between the transmitter and the receiver is measured by measuring the time required for transmission and reception in real time using a 2/3 · Δ delay lock loop that detects a PN signal synchronized with the reception PN signal by taking And even
(4) In the above (2) or (3), an SSB transmission signal that transmits only the upper band component or the lower band component of the frequency component of the Manchester PN signal to be transmitted is used. 5) The above (1) or (4)
Wherein a transmission signal obtained by adding a pilot signal for coherent detection to a DSB signal and an SSB signal to be transmitted is used. Hereinafter, a description will be given based on examples of the present invention.

FIG. 1 is a block diagram for explaining an embodiment (claim 1) of a distance measuring system according to the present invention.
Is a clock signal source, 2 is a frequency divider, 3 is an NRZ (non-return zero) -PN signal generator, 4 is an EX-OR (exclusive OR) circuit, 5 is a level converter, and 6 is a carrier signal generator , 7 is a multiplier, 8 is an amplifier, 9 is an ultrasonic transducer (for transmission), 10 is a transmission-side timing detector, 1
1 is an ultrasonic transducer (for receiving), 12 is an amplifier, 13 is a frequency converter, 14 is a PN signal detector, 15
Is a time delay measuring instrument.

Various codes such as an M-sequence code and a Gold code are used for the spread code. The present invention aims to increase the distance measurement resolution by using a Manchester-converted signal of these codes. Therefore, the embodiment will be described by taking an M-sequence code generally used as a spread code. A code length of 7 as shown in FIG.
When the chip M-sequence code is used, the Manchester spread signal is given in FIG. Manchester P
The N signal is, for example, an EX-OR of a PN signal from the PN signal generator 3 and a clock signal having a frequency twice as high as the chip rate of the PN signal, and level conversion by the level converter 5. Obtainable. This signal is multiplied by a carrier wave and transmitted. Although the case of a distance measurement system using an ultrasonic wave as a carrier wave at a relatively short distance is shown, a radio wave or light may be used as the carrier wave. Also,
The form of distance measurement is intended to measure the distance between two points using a direct wave from a transmitter, but a system that measures the distance to a certain object using a reflected wave like a radar may be used. The receiver determines the reception time by performing correlation detection or synchronization detection in order to extract the same signal as the Manchesterized PN signal generated in the transmitter. The time delay τ from the time of transmission is determined by the time delay measurement unit 15. The distance L between the transmitter and the receiver is calculated by measurement. L is calculated as L = cτ, where L is the sound speed of c.

FIG. 4 is a diagram showing a method of detecting a received signal using correlation detection. In the figure, reference numeral 21 denotes an ultrasonic transducer (for reception), 22 denotes an amplifier, 23 denotes a carrier signal detector,
24 is a multiplier, 25 is an LPF (low-pass filter), 2
6 is a comparator, 27 is a matched filter, 28 is an absolute value circuit, 29 is a comparator, 30 is a time delay measuring device (counter), and 31 is a matched filter.

[0010] The transmitted Manchesterized P is transmitted to the receiver.
A matched filter 31 for N signals is prepared, and when a signal is received, a pulsed autocorrelation signal is output. By measuring the time from the start of transmission until the correlation pulse output is obtained, the distance between the transmitter and the receiver can be determined. Note that the configuration is such that the carrier signal is extracted and the received signal is subjected to homodyne detection.
A configuration in which a correlation signal is detected by a W matched filter and an envelope detector may be used. FIG. 5 shows the correlation output when the Manchesterized PN signal as shown in FIG. 3 is used. Compared with FIG. 6 showing the correlation output of the M-sequence signal without Manchester conversion in FIG.
It can be seen that when the width of the probe is changed to Manchester, the width is reduced by 1/3 chip length, and therefore the time resolution is improved when the same chip rate is used. The method using correlation detection has the advantage that it can be configured with a simple system, but has the problem that it becomes difficult to identify the correlation pulse output if there is a multipath signal or the like. To solve this problem, a system based on synchronization detection is preferable.

FIG. 7 is a diagram showing a method of detecting a received signal using synchronization detection. In the drawing, reference numerals 32a and 32b denote multipliers,
a and 33b are absolute value circuits, 34 is an adder, 35 is a loop filter, 36 is a voltage control clock, 37 is a Manchester PN signal generator, 38 is a 2 / 3Δ delay circuit,
9a and 39b are level converters, 40 is a timing output generator, 41a is a ・ Δ delay circuit, 41b to 41f are Δ delay circuits, and 42 is an AND circuit. The receiver has a synchronization circuit for synchronously following the received Manchesterized PN signal, a so-called delay lock loop (DLL).
The delay lock loop has a reference signal generator that generates a Manchester PN signal having the same sign as the transmitted Manchester PN signal, and uses the output PN signal and a signal having a time delay of 2/3 chip length as a reference signal. Correlate with the received PN signal. That is, the received signal is correlated with the received PN signal as a reference signal using a signal having a time progress of 1/3 chip length and a signal having a time delay of 1/3 chip length. At this time, the delay discrimination characteristic of the synchronous loop is as shown in FIG. FIG. 9 shows the delay discrimination characteristic of the PN signal not converted to Manchester in the case of the 1Δ type.

The inclination of the linear portion passing through the origin is steeper in the case of Manchester, and there is an advantage that a phase error when noise is mixed is reduced. By observing the pattern of the PN signal extracted by the DLL synchronization detection, the delay time required for transmission and reception is measured. For example, in the case of the Manchesterized PN signal shown in FIG. 3, the pattern of "+1, -1" is repeated only once, so that the PN signal for six chips is observed and "+1, -1, +1" , -1, +1,
A pulse may be generated when a pattern of -1 "comes. Each transmitter / receiver is provided with this function, and the time required for transmission / reception is determined by comparing the time at which the pulse is generated.
That is, since the propagation time of the carrier is known, the distance between the transmitter and the receiver can be measured.

In the above embodiment, a carrier signal is extracted from the received signal by square detection or the like, the frequency of the received PN signal is converted to baseband, and the system is configured to perform synchronous detection using the baseband DLL. In order to eliminate the uncertainty of the correlation output value due to the uncertainty of the phase (0 and π) of the detected carrier signal, an absolute value circuit is used for each arm filter. Although the above-described embodiment is based on homodyne detection, a system using non-coherent DLL by converting the frequency to an intermediate frequency signal by so-called heterodyne detection may be used. In that case, DL
Each of the L arm filters is constituted by a multiplier, a band-pass filter, an envelope detector, a square detector, or the like.

The system according to the first to third aspects is a method for transmitting the upper and lower side bands of the Manchesterized PN signal. However, the transmission band may be limited, for example, when using ultrasonic waves. In such a case, as a method of narrowing the transmission band without lowering the chip rate of the PN signal related to the resolution, there is a method of transmitting the PN signal by the SSB method (the above-mentioned known document). Conventionally, this method has been applied to PN signals that are not converted to Manchester. An embodiment in which this method is applied to a Manchesterized PN signal (Claim 4) is shown in FIG.
(A) and (b) show. FIG. 1A is a configuration diagram of a transmitter, and FIG. 2B is a configuration diagram of a receiver. In the figure, 51 is a clock signal source,
52 is a 2 frequency divider, 53 is an NRZ-PN signal generator, 54
Is an EX-OR (exclusive OR) circuit, 55 is a level converter, 56 is a carrier signal source, 57 is a multiplier, and 58 is a transmission signal.
This is a filter that limits the band of the signal, and is a high-pass filter.
(HPF), low-pass filter (LPF), band-pass filter
Filter (BPF). 59 is an amplifier, 60 is an ultrasonic transducer (for transmission), 6
1 is an ultrasonic transducer (for reception), 62 is an amplifier, 63 is BPF1, 64a and 64b are multipliers, 65
a, 65b are BPF2, 66a, 66b are envelope detection,
67 is an adder, 68 is a loop filter, 69 is a voltage control clock, 70 is a Manchesterized PN signal generator, 7
1 is a 2 / 3.DELTA. Delay circuit, 72a and 72b are level converters, 73 is a timing output generator, and 74 is a time delay measuring device. In the transmitter of FIG. 10A, the band is limited using the high-pass filter 58 before transmission from the ultrasonic transducer 60, and only the upper band component is transmitted. The lower band wave may be transmitted using a low-pass filter, or the high-pass filter and the low-pass filter
BPF may be used .

FIG. 10B shows an example in which a non-coherent DLL is used as a configuration example of the receiver. The received signal passes through a wideband bandpass filter BPF1 having a bandwidth for allowing the spread signal to pass, and is then despread by the reference PN signal to become a narrowband signal. Then, after passing through a narrow band-pass filter BPF2, envelope detection is performed by envelope detectors 66a and 66b, and a time error signal ε (t) is obtained.
The measurement of the propagation time t can be performed similarly to the system of FIG. Also, if one sideband can be sufficiently suppressed by the band characteristics of an ultrasonic transducer serving as a transmission source when ultrasonic waves are used as a carrier and an antenna serving as a radiation source when radio waves are used as a carrier, the carrier wave frequency can be reduced. Is set to the upper or lower limit frequency of the band characteristic of the transducer or the antenna, the SSB signal can be transmitted.

FIG. 11 shows an envelope of the spectrum of the Manchester PN signal. NRZ without Manchester
Compared to FIG. 12, which shows the spectral envelope of the PN signal, the signal power spectrum of the Manchesterized PN signal is concentrated near the center of the transmission band, whereas the NRZ
It can be seen that the -PN signal gathers at the edge of the band. When limiting the band, not limited to the band characteristics of the ultrasonic transducer, deterioration of the filter characteristics at the end of the band is inevitable.
Therefore, if the spectrum of the signal itself is concentrated at the center of the limited band, the system becomes simpler, and since the transmission PN signal also has less spectral distortion, there is an advantage that the deterioration of the autocorrelation characteristic is reduced. Will have.

When homodyne detection is performed in the receiver according to claim 1 or 4, since the signal to be transmitted does not include a carrier signal component, the carrier signal is not included in the DSB signal by a method such as square detection. It must be extracted, which complicates the circuit configuration of the receiver. Meanwhile, SSB
It is very difficult to extract a carrier signal from a signal. In such a case, in order to facilitate homodyne detection on the receiver side in such a case, a transmission signal obtained by adding a carrier pilot signal to the frequency-converted Manchesterized PN signal is used.

FIG. 13 shows an example of the configuration of a transmitter when the SSB signal used in claim 5 is used and an example of the configuration of a carrier signal detector of a receiver. In the figure, 81 is a carrier signal source,
82 is a multiplier, 83 is a band limiting filter , 84 is an amplitude adjuster, 85 is an adder, 86 is an amplifier, 87 is an ultrasonic transducer (for transmission), 88 is an ultrasonic transducer (for reception), 89 is an amplifier , 90a and 90b are BP
F and 91 are multipliers, and 92 is a low-pass filter . P
The system described in claims 1 to 4 is applicable to the extraction of the N signal. The Manchesterized PN signal is transmitted from the transducer after being added with a pilot signal of a carrier frequency which has been appropriately adjusted in amplitude. On the receiving side, a pilot signal is extracted using a band filter, the pilot signal is removed from the received signal by a band filter, and homodyne detection is performed. With this,
No DC component is included after detection. Also,
LPF converts the baseband PN signal after homodyne detection.
It is a filter for taking out. Note that the carrier signal may be extracted using a synchronization circuit such as a PLL instead of using the bandpass filter as in this embodiment.

[0019]

As apparent from the above description, the present invention has the following effects. (1) Effect on Claim 1: Manchesterized P
By using the N signal, the normal P
The time resolution is higher than when N signals are used, and more accurate distance measurement is possible. (2) Effect on Claim 2: Since a correlation pulse output signal with the received PN signal can be obtained asynchronously using a matched filter for the Manchesterized PN signal, accurate distance measurement can be performed with a simple system configuration. . (3) Effect on Claim 3: Synchronous detection of a received PN signal using a 2/3 · Δ delay lock loop relating to a Manchesterized PN signal makes it highly accurate and less susceptible to noise such as a multipath signal. Distance measurement becomes possible. (4) Effect on Claim 4: By transmitting the Manchesterized PN signal by the SSB method, it is possible to measure distance with high time resolution, while maintaining a short chip length, less subject to band limitation in transmission / reception and transmission processes. Becomes (5) Effect on Claim 5 By superimposing a carrier signal as a pilot signal on a transmitted Manchester PN signal, a receiver using synchronous detection can be realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of a distance measuring system according to the present invention.

FIG. 2 is a diagram illustrating an NRZ-PN signal.

FIG. 3 is a diagram illustrating a Manchesterized PN signal.

FIG. 4 is a diagram illustrating a method of detecting a received signal using correlation detection.

FIG. 5 is a diagram illustrating an autocorrelation characteristic of a Manchesterized PN signal.

FIG. 6 is a diagram illustrating an autocorrelation characteristic of an NRZ-PN signal.

FIG. 7 is a diagram illustrating a detection method of a received signal using synchronization detection.

FIG. 8 is a diagram showing a 2/3 · Δ delay discrimination characteristic of a Manchesterized PN signal.

FIG. 9 is a diagram illustrating 1Δ delay discrimination characteristics of an NRZ-PN signal.

FIG. 10 is a diagram showing another embodiment of the distance measuring system according to the present invention.

FIG. 11 is a diagram showing a Manchesterized PN signal.

FIG. 12 is a diagram illustrating an NRZ-PN signal.

FIG. 13 is a configuration diagram of a transmitter and a receiver when an SSB signal is used.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Clock signal source, 2 ... 2 frequency divider, 3 ... NRZ (non-return zero) -PN signal generator, 4 ... EX-OR (exclusive OR) circuit, 5 ... Level converter, 6 ... Carrier signal Generator, 7 Multiplier, 8 Amplifier, 9 Ultrasonic transducer (for transmission), 10 Transmitter timing detector,
11: Ultrasonic transducer (for reception), 12: Amplifier, 13: Frequency converter, 14: PN signal detector, 15
… Time delay measuring instrument.

Continuation of the front page (56) References JP-A-5-7196 (JP, A) JP-A-4-367132 (JP, A) JP-A-4-347942 (JP, A) JP-A-4-252513 (JP) JP-A-4-47819 (JP, A) JP-A-3-184446 (JP, A) JP-A-2-246542 (JP, A) "Radar technology part 2", published by the Society of Electronics and Communication Engineers, Showa First edition issued on April 30, 43, p. 119-p. 124 (12.5 coded pulse radar) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 7/00-7/64 G01S 13/00-17/88

Claims (5)

(57) [Claims] A spread signal is transmitted using a carrier wave such as a radio wave, a sound wave, or light using a pseudo-noise code, and a time delay between transmission and reception of a reflected wave or a direct wave from a transmission time to a reception time is used. In a distance measuring system for measuring the distance, a pseudo noise signal is subjected to Manchester encoding as a spread signal. 2. The receiving side has the same Manchester P as the transmitting side.
The distance between the transmitter and the receiver is measured by measuring the time required for transmission and reception from a correlation output pulse signal obtained using a matched filter for N signals.
The ranging system described. 3. The receiving side has the same Manchester P as the transmitting side.
A PN signal generator that generates an N signal; a reference signal that is one third of the chip length of the PN signal and a reference signal that is one third chip delayed with respect to the received PN signal from the PN signal generator; And a real-time transmission / reception using a 2 / 3.DELTA. Delay lock loop that detects a PN signal synchronized with the received PN signal by correlating the reference signal with the received PN signal. The distance measuring system according to claim 1, wherein the distance between the transmitter and the receiver is measured by measuring time. 4. The distance measurement according to claim 2, wherein an SSB transmission signal that transmits only the upper band component or the lower band component of the frequency component of the transmitted Manchester PN signal is used. system. 5. The distance measuring system according to claim 1, wherein a transmission signal obtained by adding a pilot signal for coherent detection to a DSB signal and an SSB signal to be transmitted is used.