JP2779515B2 - 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 for measuring 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 in the arrival time of the radio waves may be directly detected, and the time difference may be 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. 3 is a diagram showing the configuration of the transmission device 1 and the reception device 10 of the measurement system using the spread spectrum wave used for such a purpose.

In FIG. 3, a transmitting device 1 outputs a PN signal synchronized with a clock signal of a predetermined frequency f2 from a PN generator 2 to a modulator 3, spread modulates a carrier signal of a predetermined frequency f1, and generates a spread modulated signal. Is emitted from the antenna 4 into space as a measured object.

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.

The two correlation detectors 14 and 15 are mixer-type correlation multipliers
It consists of 14a, 15a and integrators 14b, 15b, and its output becomes the maximum level when the code phase of the PN signal on the transmitting side and the PN signal on the receiving side are synchronized. The signal is combined with a signal (root mean square) corresponding to the power intensity by the arithmetic unit 18 and input to the oscilloscope 19.

When the receiving apparatus 10 receives a direct wave from the transmitting apparatus 1, two PN generators 2 having a clock frequency difference of Δf,
When the code phase of the PN signal output from 16 is significantly different, there is no output because the correlation cannot be obtained. However, as the phase difference decreases, the correlation output increases, and as shown in FIG. It increases and reaches a maximum when it is almost synchronized (not completely synchronized due to Δf) (at time t1), and its correlation output thereafter decreases.

On the other hand, since the PN signal of the reflected wave reflected by the reflector R at a building or the like has a phase difference corresponding to the distance difference of the propagation path with respect to the direct wave, the correlation output of the reflected wave is , Increasing after the correlation output of the direct wave as shown in FIG.
It becomes maximum at the time of synchronization (t2) and decreases thereafter.

The maximum values A and B of the correlation output are proportional to the power intensities of the direct wave and the reflected wave, and are directly obtained by calculating the time difference T between the times t1 and t2 from the correlation output waveform displayed on the oscilloscope 19. The distance difference between the propagation paths of the wave and the reflected wave 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).

 Therefore, the resolution of measurement is 1 / f2.

<Problems to be Solved by the Invention> However, when the correlation output waveform proportional to the power intensity is observed on the screen as in the above-described receiving apparatus, the reflected wave (secondary, tertiary,. If the reflected wave (including the reflected wave) is extremely small, it becomes extremely difficult to measure the power and the distance difference as described above.

That is, the observation range (voltage lens) in the oscilloscope
The range that can be observed simultaneously without switching is 100 times (40d
B), measurement is not possible when the attenuation rate of the reflecting object is large.

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 apparatus using a spread spectrum wave according to the present invention comprises a device under test spread-modulated by a PN signal synchronized with a clock signal having a predetermined frequency f2. Transmitter that emits waves (1)
Receiving each measured wave emitted from the transmitting device and arriving with a time difference through different propagation paths, and having the same code sequence as the PN signal of the transmitting device and a frequency difference with respect to the predetermined frequency f2. A spread modulation signal modulated by a PN signal synchronized with a clock signal having Δf and each of the received measured waves are input to correlators (25, 35), and a correlation between the spread modulation signal and each of the measured waves is inputted. And display the correlation output on a display device (56)
A propagation path measurement using a spread-spectrum wave, comprising: a reception device that displays a correlation output waveform of each of the measured waves with respect to the spread-modulated signal with a larger time difference between arrival times of the respective measured waves. In the apparatus, the correlator multiplies each of the received measured waves by the spread modulation signal, converts the multiplication result into a predetermined intermediate frequency, and outputs the result. Bandpass filters (29, 39) that receive the output of the correlation multiplier and pass only the signal components in the intermediate frequency band
Logarithmic converters (30, 40) for logarithmically compressing and outputting the level of the signal passed through the band-pass filter, and baseband demodulating the output from the logarithmic converter, and outputting the demodulation result as a correlation output And a baseband demodulator (31, 41).

<Operation> As described above, according to the present invention, the correlation between each measured wave emitted from the transmission device and arriving with a time difference through different propagation paths and a spread modulation signal generated in the reception device is equal to or less than that. The correlation output is compressed by a logarithmic converter and output to a display device. For this reason, the correlation output waveform of the strong measured wave that has arrived without being attenuated is strongly compressed and displayed, and the correlation output of the weak measured wave that has arrived and has been attenuated is displayed without being strongly compressed.

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

FIG. 1 is a block diagram showing a receiving apparatus which receives a radio wave from the transmitting apparatus 1 as described above (FIG. 3) and observes its transmission level and reflection status.

In FIG. 1, reference numeral 22 denotes a received signal (wave under test) received by an antenna 21 and a local oscillation signal (frequency f) from a 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.

Reference numeral 24 divides the output signal from the frequency converter 22 into two signal components I and Q having phases different from each other by 90 degrees, and outputs them to the first and second correlation detectors 25 and 35 which are the correlators of this embodiment. Output phase shifter.

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 having a predetermined frequency f4 (for example, 129.3 MHz) input from the signal generator 23 via the distributor 51 with the PN signal from the PN signal generator 50. Note that the PN signal generator 50 outputs a predetermined frequency (f2−Δ
The PN signal synchronized with the clock of f) is generated.

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 distributor 51 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 29K.

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

A baseband demodulator 31 includes a mixer 32 and a low-pass filter (hereinafter, referred to as LPF) 33. The baseband demodulator 31 outputs an output from the logarithmic compressor 30 via a distributor 52 output from the signal generator 23. Frequency f5 (for example, 10.7 MHz
The frequency conversion is performed on the local oscillation signal of z), the band of the converted output is limited, and a correlation signal of the signal component I with respect to the spread modulation signal is output as a direct current.

Therefore, the output of the LPF 33 when the correlation between the spread modulation signal and the signal component I is obtained corresponds to the logarithmically compressed power intensity of one of the vector components 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
Logarithmically compressed at 0, the mixer 42 of the baseband demodulator 41 and L
Demodulated by PF43.

Numeral 55 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 (correlation output between the received wave and the spread modulation signal) is output from the Y-axis of the oscilloscope 56. Has been entered.

The PN signal generator 50 is configured to repeatedly generate a series of PN signals, and outputs a trigger signal to the oscilloscope 56 at each repetition, and the oscilloscope 56 synchronizes with the trigger signal for time. Sweep the axis.

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

When the code phase of the PN signal modulating the two signal components frequency-converted to the 140 MHz band is significantly different from the code phase of the PN signal from the PN signal generator 50 modulating the 129.3 MHz signal, the correlation multiplier is used. The multiplication outputs from 26 and 36 are not in the intermediate frequency band, and when the phases approach, beat signals of the intermediate frequency (10.7 MHz) are output from the BPFs 29 and 39.

The level of this beat signal is compressed by logarithmic compressors 30 and 40 and demodulated to DC levels by baseband demodulators 31 and 41, respectively.

Then, 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
2 and displayed logarithmically compressed on an oscilloscope 56, as shown in FIG. 2a.

On the other hand, it reflects off buildings and attenuates greatly (eg 60dB)
Then, a weak reflected wave input with a slight delay from the direct wave is also received and subjected to correlation detection in the same manner as described above, and the correlation output is output to the oscilloscope 56. Because the compression is not strongly compressed, the second
As shown in FIG. 3B, a relatively large mountain is displayed on the screen T seconds after the peak of the direct wave.

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

In this embodiment, the first and second correlation detectors 25, 35
Input to the calculator 55 and output the oscilloscope
Although the observation was made at 56, each detection output may be converted into a digital value by an AD converter before the calculation is performed. In this case, if the calculation data is stored, it can be printed later or displayed on the screen. And can be displayed.

<Other Embodiments of the Present Invention> The present invention is not limited to this embodiment, but includes a measuring apparatus having a receiving apparatus that demodulates a spread-modulated received wave with only one correlation detector. Can be similarly applied.

Further, in the above embodiment, the first and second correlation detectors 25,
Although frequency conversion by the frequency converter 22 was performed once in the previous stage of 35, without performing this frequency conversion, the antenna
The received wave received at 21 may be directly input to the first and second correlation detectors 25 and 35 via the phase shifter 24, and may be provided before or after the frequency converter 22; A frequency converter may be provided before or after 40.

<Effects of the Present Invention> As described above, the propagation path measuring apparatus using the spread spectrum wave of the present invention is capable of transmitting each measured wave emitted from the transmitting apparatus and arriving in a state with a time difference via different propagation paths. The reception device receives a correlation between each received measurement wave and a spread modulation signal generated in the reception device, and compresses the correlation output by a logarithmic converter to output a waveform to a display device. .

Therefore, the correlation output waveform of the strong measured wave arriving without attenuation and the correlation output waveform of the weak measured wave arriving with attenuation can be observed without switching the range, and the measurement of the propagation path can be performed. It can be done easily.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a screen diagram showing a receiving state of the embodiment. FIG. 3 is a block diagram showing the configuration of the conventional device, and FIG. 4 is a diagram showing an observation screen of the conventional device. 21 ... antenna, 22 ... frequency converter, 23 ... signal generator, 24 ... phase shifter, 25 ... first correlation detector, 26 ... correlation multiplier, 30 ... logarithmic compressor, 31 baseband demodulator, 35 second correlation detector, 36 correlation multiplier, 40
... logarithmic compressor, 41 ... baseband demodulator.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeru Kozono 1-6-1 Uchisaiwai-cho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (58) Field surveyed (Int. Cl. ⁶ , DB name) H04J 13 / 00-13/06

Claims (1)

(57) [Claims] 1. A PN synchronized with a clock signal having a predetermined frequency f2.
A transmitting apparatus (1) for emitting a measured wave spread-modulated by a signal, and receiving each of the measured waves emitted from the transmitting apparatus and arriving with a time difference through different propagation paths, and A spread modulation signal modulated with a PN signal synchronized with a clock signal having the same code sequence as the PN signal and having a frequency difference Δf with respect to the predetermined frequency f2, and the received measured waves are correlated with correlators (25, 35). ) To obtain a correlation between the spread modulated signal and each measured wave, and output the correlation output to a display device (56), whereby a correlation output waveform of each measured wave with respect to the spread modulated signal is obtained. In a propagation path measurement device using a spread spectrum wave, comprising: a reception device for displaying a time difference larger than the arrival time difference of each of the measured waves, wherein the correlator includes: each of the received measured waves and the spread modulation signal. And a correlation multiplier (26, 36) for converting the multiplication result into a predetermined intermediate frequency and outputting the intermediate frequency, and a band-pass filter receiving the output of the correlation multiplier and passing only the signal component of the intermediate frequency band (29, 39); a logarithmic converter (30, 40) for logarithmically compressing and outputting the level of the signal passed through the band-pass filter; baseband demodulation of the output from the logarithmic converter; And a baseband demodulator (31, 41) that outputs a correlation output as a correlation output.