JP2767274B2 - Propagation path measurement device using spread spectrum waves - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field of the Present Invention> The present invention relates to a propagation path measuring apparatus that measures a propagation path of a radio wave using a spread spectrum wave spread and modulated with a PN signal (pseudo noise signal). About.

<Prior Art> (FIGS. 6 and 7) For example, when measuring the distance difference between propagation paths using radio waves, the difference between the arrival times of the radio waves may be directly detected and the time difference multiplied by the speed of light.

However, a normal transmission / reception system can only measure a large distance difference and is easily affected by noise.

For such a purpose, a measurement system using a spread spectrum wave, which is hardly affected by other communication or noise, and can measure even a small distance difference of a propagation path, has been conventionally used.

FIG. 6 is a diagram showing the configuration of the transmitting device 1 and the receiving device 10 of the measurement system using the spread spectrum wave used for such a purpose.

The transmitting device 1 outputs a PN signal synchronized with the clock signal of the predetermined frequency f2 from the PN generator 2 to the modulator 3, spread-modulates the carrier signal of the predetermined frequency f1, and uses the spread modulation signal as a wave to be measured. Fire from antenna 4 into space.

On the other hand, the receiving device 10 frequency-converts the signal received by the antenna 11 with a local oscillation signal having a predetermined frequency f3, and converts the converted signal from the frequency converter 12 into two , Q and input to the correlation detectors 14 and 15, respectively. Also, a PN signal synchronized with the clock signal of the frequency (f1−Δf) is output from the PN generator 16 to the modulator 17, and
The signal of the frequency (f1-f3) is spread-modulated, and the spread-modulated signal is input to two correlation detectors 14 and 15, and the received wave is subjected to correlation detection.

Note that the code sequence of the PN signal on the transmitting side and the PN signal on the receiving side are the same, and for example, 511 bits constitute one frame.

The two correlation detectors 14 and 15 are mixer-type correlation multipliers
It is composed of 14a, 15a and integrators 14b, 15b, and outputs a DC signal which becomes maximum when the codes of the PN signals on the transmitting side and the receiving side are synchronized. This maximum value corresponds to power components having a phase difference of 90 degrees of the received wave, and is combined with a signal (root mean square) corresponding to the power intensity by the arithmetic unit 18 and input to the oscilloscope 19.

FIG. 7 is a timing chart showing how the receiving device 10 receives a radio wave from the transmitting device 1 (FIG.
The horizontal scales of b and c indicate the boundaries of one frame of the PN signal.)

At the start of reception (at time t0), it is assumed that the PN signal of the direct wave from the transmitter 1 is advanced by the time Ts with respect to the PN signal of the receiver 10 (c in FIG. 7) as shown in FIG. 7A. Since the code phase difference between the two (that is, the time Ts) is large and the correlation cannot be obtained, a correlation output (d in FIG. 4) cannot be obtained. When the code phase difference between the two becomes smaller after a lapse of a predetermined time, the correlation output A for the direct wave increases with time, becomes maximum when both code phases are synchronized (t1), and thereafter, the correlation output decreases.

On the other hand, the PN signal of the reflected wave reflected by the reflector R at a building or the like (b in the figure) has a phase difference corresponding to the distance difference of the propagation path with respect to the direct wave. The correlation output B of the wave increases later than the correlation output A of the direct wave, reaches a maximum when both codes are synchronized (t2), and thereafter its output decreases.

Note that the maximum values Am and Bm of the correlation output are proportional to the power intensities of the direct wave and the reflected wave, and the time difference T between t1 and t2 is obtained from the correlation output waveform displayed on the oscilloscope 19, thereby obtaining a difference between the direct wave and the direct wave. The distance difference between the propagation paths of the reflected waves is obtained.

That is, the delay time per bit of the PN signal of the transmitting device 1 is 1 / f2, and the time between the frequency f2 and the frequency f2-Δf is shifted by 1 bit is 1 / Δf, so that T / (1 / Δf)
= T · Δf bits, and the distance difference L is L = (1 / f2) · T · Δf · C (m) (where C is the speed of light).

<Problems to be Solved by the Invention> However, since the PN signal on the receiving side is asynchronous with the PN signal on the transmitting side, the time position at which the correlation output waveform is obtained is
It greatly depends on the phase difference (Ts in time) between the frames of both PN signals at the start of reception. In order to display the correlation output waveform on the oscilloscope screen by one sweep, the PN signal of the receiver 10 and the direct wave Tm until the code phases of both PN signals are synchronized at a speed corresponding to the clock frequency difference Δf from the PN signal (the maximum time is 1 when Ts = 0 and 1
If M bits are used per frame, about M / Δf) is required.

Therefore, in order to observe the correlation output waveform, it is necessary to sweep the time axis of the oscilloscope at least at the time equal to or longer than the Tm time.In this case, the correlation output waveform is observed at the end of the time Tm. In this case, there is a disadvantage that the observation time before that time is wasted.

Further, as described above, if the oscilloscope sweep time becomes longer, it is possible to separate and judge the close direct wave and the reflected wave, for example, the direct wave and the reflected wave having a phase difference (time difference) of 1 bit on the screen. There was a drawback that it would not be possible.

For this reason, it is conceivable to observe the portion where the correlation output waveform is displayed by enlarging the time axis of the oscilloscope, but this method hindered the observation because it was not possible to determine where the correlation was obtained in the PN code .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a propagation path measuring device using a spread spectrum wave which solves this problem.

<Means for Solving the Problems> In order to solve the above problems, a propagation path measuring device using a spread spectrum wave of the first invention is spread-modulated by a PN signal synchronized with a clock signal of a predetermined frequency f2. Transmitter that emits the measured wave (1)
And each of the measured waves emitted from the transmitting device and arriving with a time difference through different propagation paths is received, and the same code string as the PN signal of the transmitting device and the frequency with respect to the predetermined frequency f2. A correlation PN signal synchronized with a clock signal having a difference Δf is generated from a correlation PN code generator (52), and spread-modulated by each of the received measured waves and the correlation PN signal by correlators (25, 35). By taking a correlation with the spread modulation signal, a propagation path measuring apparatus using a spread spectrum wave comprising: a receiving apparatus that obtains a correlation output of each measured wave with a time difference larger than the arrival time difference of the measured wave, The receiving device outputs a reset signal to the correlated PN code generator at regular intervals, and outputs a correlation signal output from the correlated PN code generator.
A reset circuit (65) for returning the code of the PN signal to the initial code; a shift circuit (53) for shifting the timing at which the reset circuit outputs a reset signal each time a switch operation is performed; and the reset circuit outputs a reset signal. A display device (46) for displaying a waveform of the output of the correlator as a display range from when the predetermined period elapses until the display period of the correlation output waveform of each of the measured waves by the switch operation. It can be moved with respect to the display range.

A transmission path measuring apparatus using a spread spectrum wave according to the second invention is a transmitting apparatus (1) for emitting a measured wave spread-modulated by an PN signal of an M-bit code string synchronized with a clock signal of a predetermined frequency f2. ) And each of the measured waves emitted from the transmitting device and arriving with a time difference through different propagation paths is received, and has the same code sequence as the PN signal of the transmitting device and the predetermined frequency f2. A correlation PN signal synchronized with a clock signal having a frequency difference Δf is generated from a correlation PN code generator (52), and is spread-modulated by the correlator (25, 35) with each of the received measured waves and the correlation PN signal. A propagation path measuring device using a spread spectrum wave, comprising: a receiving device that obtains a correlation output of each measured wave with a time difference larger than the arrival time difference of the measured wave by correlating with the spread modulated signal. The receiving device may further include a signal generator (23) that outputs the clock signal of the predetermined frequency f2, and a clock signal of the predetermined frequency f2 output from the signal generator every time a switch operation is performed. A shift circuit (53) for adding or removing pulses; a reference PN code generator (51) for outputting a reference PN signal of an M-bit code string synchronized with a clock signal output from the shift circuit; A first detector that outputs a first detection pulse each time a reference PN signal output from a code generator matches a predetermined code;
And a second detection pulse is output each time a correlation PN signal output from the correlation PN code generator matches a code shifted by N bits (N <M) from the predetermined code. A second code detection unit (64), and each time the first detection pulse and the second detection pulse are output in synchronization, the correlation PN signal output from the correlation PN code generator and the reference A reset circuit (65) for returning a reference PN signal output from a PN code generator to an initial code;
A display device (46) for displaying a waveform of the output of the correlator as a display range from a time when the signal returns to the initial code to a time when the code phase difference becomes N bits; The display position of the correlation output waveform can be moved with respect to the display range.

<Operation> Due to the above, by operating the switch of the shift circuit, the timing at which the correlated PN code generator returns to the initial code can be shifted, and the correlation output waveform between the measured signal and the spread modulation signal is displayed. It can be moved to any position in the display range of the device.

<Embodiment of the Present Invention> (FIGS. 1 and 2) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a main part of a receiving apparatus according to one embodiment, and FIG. 2 receives a radio wave from the transmitting apparatus 1 similar to that described above (FIG. 6) and observes its reception level and reflection status. FIG. 2 is a block diagram showing a receiving apparatus that performs the processing.

In FIG. 2, reference numeral 22 denotes a received signal (wave under test) received by the antenna 21 and a local oscillation signal (frequency f) from the signal generator 23.
This is a frequency converter that mixes with 3) and converts it to a predetermined frequency band (for example, 140 MHz band).

The signal generator 23 is a PLL-type generator using a rubidium oscillator as a signal reference source, and generates a highly accurate and stable signal.

Numeral 24 denotes a phase shifter which divides the output signal from the frequency converter 22 into two signal components I and Q having a phase difference of 90 degrees, and the two signal components are the first and second correlators of this embodiment. The signals are input to the correlation detectors 25 and 26.

One signal component I divided by the phase shifter 24 is input to the correlation multiplier 26 of the first correlation detector 25.

The correlation multiplier 26 is composed of, for example, a double-balanced mixer, and detects a correlation between the spread modulation signal input from the modulator 27 via the amplifier 28 and the signal component I.

The modulator 27 spread-modulates a signal of a predetermined frequency f4 (for example, 129.3 MHz) input from the signal generator 23 via the distributor 47 with a correlated PN signal from a correlated PN signal generator 50 described later.

Reference numeral 29 denotes a band-pass filter (hereinafter, referred to as a BPF) that passes a signal component of a predetermined intermediate frequency band (for example, 10.7 MHz) in the output from the correlation multiplier 26.

The frequency f4 of the signal output from the divider 47 is set to be equal to the difference between the frequency obtained by subtracting the frequency f3 of the local oscillation signal from the frequency f1 of the transmission carrier and the center frequency of the BPF 29.

Reference numeral 30 denotes a logarithmic compressor that logarithmically compresses and outputs the level of the passing output of the BPF 29.

Reference numeral 31 denotes a demodulator including a mixer 32 and a low-pass filter (hereinafter, referred to as LPF) 33. The demodulator 31 receives the output from the logarithmic compressor 30 and outputs the signal from the signal generator 23 to be input through a distributor 48. The frequency conversion is performed using a local oscillation signal having a predetermined frequency f5 (for example, 10.7 MHz), the band of the converted output is limited, and a correlation signal of the signal component I for the spread modulation signal is output.

Therefore, the output of LPF 33 when the code of the PN signal of the received wave and the spread modulation signal is synchronized indicates a signal corresponding to the logarithmically compressed power intensity of one vector component of the received wave.

Further, the other signal component Q is input to the correlation multiplier 36 of the second correlation detector 35.

The second correlation detector 35 has exactly the same configuration as the first correlation detector 25, and includes a multiplied output of the signal component Q and a spread modulation signal input from the modulator 37 via the amplifier 38. Signal of the intermediate frequency band of
The data is logarithmically compressed by 0 and demodulated by the mixer 42 and the LPF 43 of the demodulator 41.

Numeral 45 denotes an arithmetic unit for calculating the root mean square of the outputs of the first and second correlation detectors 25 and 35. This arithmetic output is used as the correlation output between the received wave and the spread modulation signal, and
Input to the axis. The maximum value of the calculation output corresponds to the power intensity of the received wave.

The correlation PN signal generator 50 has first and second PN code generators 51 and 52 as shown in FIG. A first PN code generator 51 as a reference PN code generator of this embodiment receives a first clock pulse of frequency f2 from a signal generator 23 via a shift circuit 53. Correlation PN of
A second PN code generator 52 as a code generator has a frequency f2
A second clock pulse of -Δf is input.

The first and second PN code generators 51 and 52 are configured to sequentially output a series of PN codes of the same code string in parallel in synchronization with a clock pulse. Generate a series of PN codes from C (0).

As shown in FIG. 3, the shift circuit 53 includes a pulse removing circuit 54 for removing a pulse from the first clock pulse.
And a pulse insertion circuit 57 for performing pulse insertion.

The pulse removing circuit 54 inputs a first clock pulse to one input terminal of the AND circuit 55, and when the switch S1 is pressed, the pulse removing circuit 54 changes from “H” level to “L” level in synchronization with the first clock pulse. Gate signal output circuit 56 for changing gate signal
, And the pulse is removed by inputting it to the other input terminal of the AND circuit 55.

The pulse insertion circuit 57 performs differential shaping on the output of the AND circuit 55 with the differential shaping circuit 58 and inputs the result to one input terminal of the OR circuit 59.The output obtained by inverting the output of the AND circuit 55 with the inverter 60 is a differential shaping circuit 61. And insert pulse output circuit
Enter in 62. When the switch S2 is pressed, the insertion pulse input circuit 62 supplies only one pulse from the partial shaping circuit 61 to the OR circuit 59 to perform pulse insertion.

In FIG. 1, reference numeral 63 denotes a first code detector which outputs a first coincidence pulse each time the PN code output in parallel by the first PN code generator 51 matches a predetermined initial code C (0); 64 is
Second code detection that outputs a second coincidence pulse each time the PN code output in parallel by the second PN code generator 52 matches the N-th PN code C (N) from the initial code C (0). It is a vessel.

A reset circuit 65 outputs an AND circuit 66 for calculating the logical product of the first and second coincidence pulses, and outputs an “H” level signal to the OR circuit 67 when the output of the AND circuit 66 rises to “H” level. A reset pulse generating circuit 68 for setting the output to the "L" level in response to the next first coincidence signal; and a power for outputting a reset pulse to the first PN code generator 51 and the OR circuit 67 when the power is turned on. And an on-reset circuit 69.

Note that the serial PN signal from the second PN code generator 52 is output to the modulators 27 and 37 as a correlated PN signal.

<Operation of Embodiment> As described above, a radio wave spread and modulated by a PN signal generated in synchronization with a clock signal of frequency f2 to a receiving apparatus configured as described above is received by the receiving apparatus. When the strong direct wave is emitted from the transmitting device 1 as a measurement wave, the strong direct wave is received by the antenna 21 and frequency-converted to, for example, a 140 MHz band by the local signal of the predetermined frequency f3 by the frequency converter 22, and the phase shifter 24 The signal components are divided into two signal components having different phases by 90 degrees, and the first and second correlation detectors 25 and 35 are respectively provided.
Is input to

Here, assuming that the received direct wave is PN-modulated at the timing of the frame shown in FIG. 4A and the power of the receiving apparatus is turned on at t0, the first, starting at t0 with the same initial code C (0), The PN codes of the second PN code generators 51 and 52 gradually shift in phase at a speed corresponding to the frequency Δf as shown in FIGS. 4C and 4D, and at t1, a direct wave (FIG. 4A).
Since the frame phase of the PN signal and the code phase of the correlation PN signal from the second PN code generator 52 start to be substantially synchronized, correlation signals of the intermediate frequency (10.7 MHz) are output from the BPFs 29 and 39,
Compressed by logarithmic compressors 30 and 40, demodulated by demodulators 31 and 41, respectively, and input to arithmetic unit 45, the root mean square of the correlation output of the two signal components, that is, the correlation output of the direct wave with respect to the spread modulation signal is can get. Since this correlation output is input to the oscilloscope 46 having a screen sweep frame from the time t0 to the next reset timing, as shown in FIG.
The level starts to increase from t1, the maximum becomes at t2 when the sign of the PN signal of the direct wave and the sign of the correlation PN signal are synchronized, and thereafter the correlation output waveform A of the direct wave is displayed which decreases until t3.

On the other hand, it reflects off buildings and attenuates greatly (eg 60dB)
A weak reflected wave input with a slight delay from the direct wave is also received in the same manner as described above, but the PN signal of the reflected wave slightly delayed from the PN signal of the direct wave (FIG. PN code generator
The correlation output waveform B of the reflected wave that peaks at t5 when the phase with the correlation PN signal of 52 is synchronized from t4 to t6 and is almost completely synchronized at t5 is relatively T seconds after the correlation output waveform A of the direct wave. It is displayed on the screen as a large mountain.

Therefore, it is possible to observe the presence / absence of a reflector on the radio wave propagation path, the amount of attenuation thereof, the distance difference of the path (using the above calculation), and the like from the size and time interval (T) of these peaks.

If the code of the PN signal of the first PN code generator 51 serving as the reference and the code of the PN signal of the second PN code generator 52 are shifted by N bits at t7, the correlation PN signal generator 50 First,
Since the first and second coincidence pulses from the second code detectors 63 and 64 are simultaneously output as shown in FIGS. 4E and 4F, the reset signal shown in FIG. When the signal is output to the PN code generator 52 and the next first coincidence pulse is input, the state returns to the state at t0.

Screen sweep frame of oscilloscope 46 (display area)
This is from the time when the second PN code generator 52 is reset as shown in FIG. 4 until the time when the second PN code generator 52 is reset. Therefore, if the shift circuit 53 is not operated,
The correlation output waveform shown in FIG. 4H is continuously displayed on the screen 46.

In this case, the time axis of the oscilloscope 46 sweeps repeatedly from t0 to t8, and the first PN signal from the second PN code generator 52 is used as a reference in one sweep time. Therefore, the correlation of the PN signal from the PN code generator 51 in the range of N bits is obtained, and the observation range (correlation range) is in the range of N bits.

In FIG. 4, the power-on timing is good, and the PN signal of the received wave and the correlated PN signal are within the N-bit observation range from the beginning, but as in the start of reception (t0) in FIG. ,
If the phases of the PN codes of the first and second PN code generators 51 and 52 lag behind the PN signals (a and b in the same figure) of the received waves (direct waves and reflected waves), both at t7 No correlation can be obtained within the N-bit observation range until the code of the PN signal is shifted by N bits.

Here, when the sign of both PN signals is reset at t8 and at any time t9, the switch S2 of the shift circuit 53 is pressed a predetermined number of times to insert a predetermined number of pulses between the first clock pulses. The frame phase of the code of the PN signal from the first PN code generator 51 advances by a predetermined time Tf.

The first PN phase shifted by Tf by this pulse insertion
Since the code generator 51 receives the first clock pulse in the advanced state thereafter, the code generator 51 outputs a PN signal whose phase is slightly advanced with respect to the PN signal (FIGS. 5a and 5b) of the received wave. I do.

Therefore, the correlation output waveforms A and B of the received wave (direct wave and reflected wave) are displayed on the oscilloscope screen from the next reset (t10) as shown in FIG. 5h.

Note that if pulse insertion or pulse removal for the first clock pulse is performed as needed, the frame phase of the PN signal code of the first PN code generator 51 serving as a reference becomes equal to the number of inserted pulses or the number of removed pulses. Therefore, the display position of the correlation output waveform shifts left and right on the oscilloscope screen.

<Another embodiment of the present invention> The present invention is not limited to this embodiment,
The present invention can be similarly applied to a measuring apparatus having a receiving apparatus that demodulates a spread-modulated received wave with only one correlation detector.

Further, in the above embodiment, the correlation output is converted to the intermediate frequency, and the level is logarithmically compressed and then demodulated.
The present invention can also be applied to a measuring device having a receiving device having a conventional configuration (FIG. 6).

<Effects of the present invention> As described above, in the propagation path measuring device of the first invention, the receiving device for receiving the measured wave emitted from the transmitting device is provided with a constant relative to the correlated PN code generator. A reset circuit that outputs a reset signal every period to return the code of the correlated PN signal to the initial code, a shift circuit that shifts the timing at which the reset circuit outputs the reset signal each time a switch operation is performed, And a display device for displaying the waveform of the output of the correlator as a display range from the output of the predetermined period to the elapse of the predetermined period, and displaying the display position of the correlation output waveform of each measured wave by operating a switch. You can move around the range.

Further, in the propagation path measuring device of the second invention, a signal generator that outputs a clock signal having the same frequency f2 as the clock signal of the PN signal on the transmitting device side,
A shift circuit that adds or removes a pulse from a clock signal of a predetermined frequency f2 output from the signal generator,
A reference PN code generator for outputting a reference PN signal of an M-bit code string synchronized with a clock signal output from the shift circuit; and a reference PN signal output from the reference PN code generator is output every time the reference PN signal matches a predetermined code. First code detection means for outputting one detection pulse, and correlation output from a correlation PN code generator
A second code detecting means for outputting a second detection pulse each time the PN signal matches a code shifted by N bits (N <M) from the predetermined code, and wherein the first detection pulse and the second detection pulse are A reset circuit that returns the correlated PN signal and the reference PN signal to the initial code every time they are output in synchronization, and a code phase difference of N after the correlated PN signal and the reference PN signal return to the initial code by the reset circuit. A display device for displaying the waveform of the output of the correlator as a display range until the number of bits is reached, so that the display position of the correlation output waveform of the measured wave can be moved with respect to the display range of the display device by operating a switch. I have.

For this reason, the correlation output waveform of the measured wave can be moved within the display range without expanding the display range of the display device, and the positional relationship between the sign of the correlated PN signal and the display range can be easily grasped. Accurate and accurate propagation path measurement.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of one embodiment of the present invention, FIG. 2 is a diagram showing an overall configuration of a receiving apparatus of one embodiment, and FIG. 3 is a block diagram showing a main part of FIG. is there. 4 and 5 are timing charts for explaining the operation of one embodiment. FIG. 6 is a block diagram showing the configuration of the conventional device, and FIG. 7 is a timing chart for explaining the operation of the conventional device. 23 ... signal generator, 50 ... correlation PN signal generator, 51 ... first PN code generator, 52 ... second PN code generator, 53 ...
Shift circuit, 54... Pulse removal circuit, 57... Pulse insertion circuit, 63... First sign detector, 64... Second sign detector, 65.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Satoshi Tanaka 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (58) Field surveyed (Int.Cl. ⁶ , DB name) H04J 13 / 00-13/06

Claims (2)

(57) [Claims] 1. A PN synchronized with a clock signal having a predetermined frequency f2.
A transmitting device (1) for emitting a measured wave spread-modulated by a signal, and receiving each of the measured waves emitted from the transmitting device and arriving with a time difference through different propagation paths, and transmitting the measured signal. A correlated PN code generator (52) generates a correlated PN signal synchronized with a clock signal having a frequency difference Δf with respect to the predetermined frequency f2 and having the same code sequence as the PN signal of A receiving apparatus that obtains a correlation output of each measured wave with a time difference larger than the arrival time difference of the measured wave by correlating the received measured waves with a spread modulation signal spread-modulated by the correlation PN signal. In the propagation path measuring apparatus using a spread spectrum wave comprising: the receiving device outputs a reset signal to the correlated PN code generator at regular intervals, and outputs the reset signal from the correlated PN code generator. Correlation PN
A reset circuit (65) for returning the sign of the signal to an initial code; a shift circuit (53) for shifting the timing at which the reset circuit outputs a reset signal each time a switch operation is performed; and the reset circuit outputs a reset signal. A display device (46) for displaying the waveform of the output of the correlator as a display range from when the predetermined period has elapsed until the predetermined period elapses, and the display position of the correlation output waveform of each of the measured waves is displayed by the switch operation. A propagation path measurement device using a spread spectrum wave, wherein the propagation path measurement device is movable with respect to a range. 2. An M signal synchronized with a clock signal having a predetermined frequency f2.
A transmitting device (1) for emitting a measured wave spread-modulated by a PN signal of a bit code sequence, and receiving each measured wave emitted from the transmitting device and arriving with a time difference through different propagation paths. At the same time, a correlated PN code generator (52) generates a correlated PN signal having the same code sequence as the PN signal of the transmitting device and synchronized with a clock signal having a frequency difference Δf with respect to the predetermined frequency f2. 25, 35), the correlation between each received wave under measurement and the spread modulation signal spread-modulated with the correlated PN signal is obtained, whereby the correlation of each measured wave with a time difference larger than the arrival time difference of the measured wave is obtained. In a propagation path measuring device using a spread spectrum wave, comprising a receiving device for obtaining an output, the receiving device receives a signal generator (23) for outputting a clock signal of the predetermined frequency f2, and receives a switch operation. A shift circuit (53) for adding or removing a pulse to or from a clock signal having a predetermined frequency f2 output from the signal generator, and an M-bit code synchronized with the clock signal output from the shift circuit. A reference PN code generator (51) for outputting a column of reference PN signals, and a first detection pulse for outputting a first detection pulse each time the reference PN signal output from the reference PN code generator matches a predetermined code. A code detecting means (63) for outputting a second detection pulse each time a correlation PN signal output from the correlation PN code generator matches a code shifted by N bits (N <M) from the predetermined code. Code detection means (64), and each time the first detection pulse and the second detection pulse are output in synchronization, the correlation PN signal output from the correlation PN code generator and the reference PN signal Reference output from code generator
A reset circuit (65) for returning the PN signal to the initial code; and a display range from when the correlation PN signal and the reference PN signal return to the initial code by the reset circuit until the code phase difference becomes N bits. A display device (46) for displaying a waveform of the output of the correlator, wherein a display position of the correlation output waveform of each of the measured waves can be moved with respect to the display range by the switch operation. Path measurement device using spread spectrum waves.