JPH05264724A - Range finder - Google Patents

Abstract

PURPOSE:To provide a range finder having high frequency utilization efficiency and simple constitution by utilizing an SS communication method. CONSTITUTION:A transmitting part 1 has a PNG 11, a carrier wave generating part 12, a multiplier 13 and a high frequency part 14, wherein a transmission SS signal is transmitted from an antenna 15 to an automobile 3 to be measured and also a reference bit signal of a PN code is sent from the PNG 11 to a time calculating part 25 of a receiving part 2 to start counting. The receiving part 2 inputs a received SS signal via a high frequency part 22 to a correlator 23 to correlate with a reference PN code which is preset there. If an autocorrelated waveform signal is thus obtained, counting at the time calculating part 25 is stopped to calculate the time so far, and a distance calculating part 26 calculates, a distance based on the result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is a spread spectrum (S
S) The present invention relates to improvement of a distance measuring device suitable for in-vehicle use or the like using a communication method.

[0002]

2. Description of the Related Art Since the propagation paths of all high-frequency signals have a constant value, it is possible to measure the distance between two points by determining the time difference between the transmitted waveform and the received signal waveform.
Generally, as a method of measuring the distance between two points (reference point and measurement point), there is a method of emitting a radio wave from the reference point and receiving a reflected wave reflected at the measurement point at the reference point. In this case, the value of the distance d between the two points is given by d = (C / 2) τ (1) C: speed of light τ: propagation time.

[0003]

However, for example, when a distance measuring device by such a method is mounted on an automobile to detect other vehicles located in front of and behind the own vehicle and to measure the distance, Therefore, it is necessary to use frequencies different from each other, and in the case where they are installed in front of and behind the vehicle body, the frequency of twice the number of automobiles is used. This is not preferable in terms of feasibility and frequency utilization efficiency.

It is an object of the present invention to provide a distance measuring device having a simple structure with high feasibility and frequency utilization efficiency by utilizing the SS communication system.

[0005]

In order to achieve the above-mentioned object, the present invention is a distance measuring device provided on a measuring object and comprising a transmitting section and a receiving section, wherein the transmitting section generates a PN code. A PN code generator, spreading modulation means for spreading and modulating a carrier wave based on the PN code, and a transmitting antenna for transmitting a spread modulated signal, and the receiving section receives a signal reflected from a device under test. A correlator that correlates the received signal with a predetermined signal and outputs a correlation signal when the correlation is obtained, based on the reference bit signal of the PN code of the PN code generator of the transmitter and the correlation signal from the correlator hand,
The gist of the invention is that it comprises a time calculation unit that calculates the time difference between them and a distance calculation unit that calculates the distance to the object to be measured based on the time difference. In this case, the transmission unit is the PN
The code may be generated intermittently at predetermined time intervals.

[0006]

The diffused modulated signal transmitted from the transmitter is reflected by the object to be measured, and the obtained received signal is correlated with a predetermined signal. The time difference between them is obtained based on the reference bit signal of the PN code of the transmitter and the correlation signal, and the distance to the object to be measured can be known from the time difference.

[0007]

Embodiments of the present invention shown in the drawings will be described below.
FIG. 1 shows an embodiment of a distance measuring apparatus according to the present invention, in which 1 is a transmitting unit and 2 is a receiving unit (measuring unit). The transmitter 1 includes a PN code generator (PNG) 11, a carrier wave generator 12, and a multiplier 13.
(Phase modulator), high frequency unit 14, and transmission antenna 15. The receiving unit 2 includes a receiving antenna 21, a high frequency unit 22, a correlator 23, a detection and waveform shaping unit 24, a time calculation unit 25, and a distance calculation unit 26.

In FIG. 1, a transmitter 1 multiplies a carrier wave from a carrier wave generator 12 by a PN code generated by a PNG 11 (Pseudo Noise Generator).
3 performs phase modulation of the carrier wave and transmits an SS (Spread Spectrum) signal from the antenna 15 via the high frequency unit 14 and at the same time transmits the reference bit signal of the PN code to the time calculation unit 25 of the receiving unit 2. Then, the time calculation unit 25 starts counting.

The receiving section 2 receives the SS signal reflected from another vehicle 3 and, via the high frequency section 22, the correlator 2
Enter in 3. The correlator 23 obtains the correlation between the received PN code included in the received SS signal and the reference PN code equal to the PN code included in the transmitted SS signal preset in the correlator 23. Then, when the received PN code and the reference PN code match, an autocorrelation waveform signal having a relatively large amplitude is obtained. The obtained autocorrelation waveform signal is detected by the detection and waveform shaping section 24, further converted into a digital signal and input to the time calculation section 25, and the time calculation section 25 stops counting. The time calculator obtains the time from the generation of the reference bit signal to the generation of the autocorrelation waveform signal. Then, based on the result, the distance calculation unit 26 calculates the distance using the equation (1).

In this case, as shown in FIG. 2A, when the transmission PN code is continuously transmitted, another vehicle 3
If the delay time T1 indicating the deviation of the received PN code included in the received SS signal, which is the reflected wave from the reference signal, from the reference bit of the transmitted PN code included in the transmitted SS signal is within one cycle of the PN code, the normal delay time Can be measured. But,
As shown in FIG. 2B, if the delay time exceeds one cycle of the PN code, there is a possibility that the delay time T2 may be erroneously measured by the received PN code of the previous cycle.

Therefore, in such a case, as shown in FIG. 3A, the transmission PN code is intermittently transmitted at a predetermined time interval T3, and the time calculation unit 25 counts from the reference bit signal of the transmission PN code. To start. In this way, if the autocorrelation waveform signal by the received PN code cannot be obtained within the predetermined time, the time calculation unit 25 initializes the count content. In this way, the transmission S is intermittently performed.
By transmitting the S signal, it is possible to measure the normal delay time.

Therefore, the distance measuring device having the configuration shown in FIG. 1 for performing the above operation and the antennas 15 and 21 for transmission and reception
It is possible to detect another vehicle located in front of or behind the vehicle and to measure the distance by using the directional antenna as the. When this device is installed in a large number of automobiles, it is possible to deal with the same frequency by using different types of PN codes, which is very effective in terms of frequency utilization efficiency. is there.

If the reference PN code set in the correlator 23 in the configuration shown in FIG. 1 is switchable, directional antennas for transmission and reception are installed in front of and behind the vehicle body, A directional antenna for reception is connected to a range finder using a coupler, and a PN code included in a transmission SS signal transmitted forward from the directional antenna for transmission and a transmission SS transmitted backward. The types of the PN code included in the signal are made different, the forward transmission PN code and the backward transmission PN code are alternately transmitted at a predetermined time interval T3, and the delay time of each is measured to determine the forward and backward directions. It is possible to detect another vehicle located in the vehicle and measure the distance with the same receiver.

[0014]

As described above, according to the present invention, it is possible to provide a distance measuring device having a simple structure with high feasibility and high frequency utilization efficiency.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the above embodiment.

FIG. 3 is a diagram illustrating another operation of the above embodiment.

[Explanation of symbols]

 1 Transmitter 2 Receiver 11 PNG 12 Carrier wave generator 23 Correlator 25 Time calculator 26 Distance calculator

Claims (2)

[Claims] 1. A range finder provided on a measuring object, comprising a transmitter and a receiver, wherein the transmitter is a PN code generator for generating a PN code, and spreads a carrier wave based on the PN code. It comprises a spread modulation means for modulating and a transmitting antenna for transmitting a spread modulated signal, and the receiving section is a receiving antenna for receiving the signal reflected from the DUT, and a correlation between the received signal and a predetermined signal is obtained. At this time, a correlator that outputs a correlation signal, a time calculation unit that calculates a time difference between them based on the reference bit signal of the PN code of the PN code generator of the transmission unit and the correlation signal from the correlator, and the time difference A distance measuring device comprising a distance calculating unit for calculating a distance to a measured object based on the distance measuring unit. 2. The distance measuring apparatus according to claim 1, wherein the transmitting unit intermittently generates the PN code at predetermined time intervals.