JPH0681106B2 - Radio wave propagation characteristics measurement method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for instantaneously measuring delay characteristics and amplitude characteristics of multiple waves generated by reflection, diffraction, scattering, etc. in a radio wave propagation path.

[Conventional technology]

The radio waves propagating from the transmitter to the receiver do not all propagate at the shortest distance, but due to reflection, diffraction, scattering, etc., components that arrive at the receiver after the radio waves propagated at the shortest distance are generated. Such components are called multiple waves. In order to evaluate the radio wave propagation path from the transmitter to the receiver, it is necessary to measure the delay characteristics and the amplitude characteristics of such multiple waves.

Conventionally, a frequency correlation method, a PN signal correlation method, a television broadcast wave utilization method, a frequency sweep method and the like have been used as methods for measuring the radio wave propagation characteristics. These measuring methods will be described below.

(I) Frequency correlation method In the frequency correlation method. The frequency correlation function ρΔf (m) between reception points having different reception electric field strengths is obtained by using two frequencies having very close frequency differences Δf. Frequency correlation function ρ
Δf (m) is It is represented by. Here, x (n), y (n): electric field strength of each frequency, N: number of data used for calculation, m: position shift, <m>: integer not exceeding m. By using this relational expression, the propagation path length difference of the multiple waves is estimated by comparing with the propagation model calculated in advance.

For this method, refer to IEICE Technical Report AP81-2.
It is explained in detail in "3. Urban Propagation Model and Frequency Correlation Characteristics".

(Ii) PN signal correlation method The property that the autocorrelation function of a PN signal becomes maximum when the same waveform is synchronized in time is used.

The transmitting side transmits a PN signal having a highly accurate reference time. The receiving side generates a PN signal having the same waveform as the transmitting side while variably setting the delay time, and performs correlation detection with the signal coming from the transmitting side. At this time, the delay time of the PN signal on the receiving side that maximizes the output of the correlation detection becomes equal to the delay time due to the difference in the lengths of the multiple wave propagation paths. Therefore, the ratio between the detection output value of the main wave and the relative detection output value becomes the relative multiple wave amplitude value.

According to this method, it is possible to simultaneously obtain the propagation delay characteristic and the relative amplitude characteristic of the multiple wave from the correlation detection output and the received PN signal delay time.

This method is described in “Correlation Bandwidth and Delay Spread Multipath Propagation Statistics for 910MHz Urban Mobile Radio Channels”, IEEE Transaction No. COM-23, No. 11, 1975. Pages 1271-1280 ("Cor
relationBandwidth and Delay Spread Multipath Propa
gation Statistics for 910 MHz Urban Moble RadioCha
nnels ", IEEE Trans.COM-23, No.11, pp1271-1280,1975)
Are described in detail in.

(Iii) Carrier wave pulse method On the transmitting side, the carrier wave of the frequency to be measured is intermittently transmitted at short time intervals. On the receiving side, the received multiple waves are directly detected and their characteristics are measured.

(Iv) Television Broadcast Wave Utilization Method In this measurement method, the phase difference of the color burst signal and the delay time of the horizontal synchronizing signal included in the television broadcast wave are measured, and the delay path difference is obtained from these measured values.

A phase difference occurs between the reference received signal and the measured received signal in the color subcarrier of the color burst signal depending on the propagation path length difference. By measuring this phase difference, the propagation path length difference can be obtained. However, it is only necessary to measure the phase difference of the color burst signal,
(3.58MHz) is indistinguishable from an integer multiple of the wavelength. Therefore, the delay time of the horizontal synchronizing signal is used to determine an approximate time.

(V) Frequency sweep method The carrier frequency on the transmitting side is swept, and the amplitude frequency characteristic of the propagation path is obtained from each received level. The propagation path length difference can be obtained from this frequency characteristic.

[Problems to be solved by the invention]

 However, each of the above methods has the following drawbacks.

(I) Frequency Correlation Method In this method, the number of multiple waves existing in innumerable is estimated by a finite (about two waves) model, and therefore the error becomes large in a complicated multiple wave model. In addition, the amount of calculation for estimating the model is large, and the estimated value cannot be obtained instantaneously. Furthermore, with this method, it is difficult to estimate the amplitude characteristic.

(Ii) PN signal correlation method This method requires a highly accurate frequency reference on both the transmitting side and the receiving side to perform correlation detection. There are restrictions and it is not possible to obtain measurement results quickly.

(Iii) Carrier wave pulse method In this method, a discontinuous carrier wave is measured. Therefore, in order to improve accuracy, it is necessary to make the pulse width extremely narrow. It is difficult to stably receive and demodulate radio waves with such a very narrow pulse width due to the characteristics of the receiver.Therefore, the receiver is accurately calibrated with a narrow pulse width and the amplitude characteristics of incoming radio waves are measured accurately. It's not easy to do.

(Iv) Television Broadcast Wave Utilization This method uses a color burst signal with high phase accuracy from a television broadcasting station, so the delay time can be measured with high accuracy. Two receiving systems are required, and the accuracy cannot be obtained unless the systems are mutually calibrated, resulting in a large-scale device.

In addition, since multiple waves cannot be separated, measurement cannot be performed when two or more multiple waves exist.

Furthermore, when attempting to measure in an arbitrary section, it is necessary to make the phase of the color burst signal of the transmission signal as accurate as that used by a television broadcasting station.

(V) Frequency sweep method Since multiple waves are not measured directly, the error is large, and it is difficult to measure instantaneously because it is necessary to synchronize the transmitting side and the receiving side.

The present invention solves the above problems and provides a method for measuring radio wave propagation characteristics, which allows direct and simultaneous measurement of the propagation delay time due to the propagation path length of multiple waves and the level of each wave. The purpose is to

[Means for solving problems]

The measurement method of the present invention is a radio wave propagation characteristic measurement method for measuring delay characteristics and amplitude characteristics of a signal propagating through a radio wave propagation path including a plurality of propagation paths generated by reflection, scattering, or diffraction, and on the transmission side, A reference signal with a pulse width that is long enough to obtain a substantially constant amplitude on the receiving side, and a measurement signal with a short pulse width compared to the delay time difference caused by the lengths of the plurality of propagation paths are set according to the measured frequency. Amplitude-modulated and transmitted, and at the receiving side, the amplitude of the received measurement signal that arrived via each propagation path is corrected by the received amplitude value of the reference signal to obtain the amplitude characteristic, and the delay is delayed from the time difference of the received measurement signal. It is characterized by obtaining characteristics.

[Work]

The measuring method of the present invention can directly and instantaneously measure the amplitude and the delay time of the wave propagating the shortest distance for each of the multiple waves generated in the radio wave propagation path. Since the signal to be transmitted / received includes the reference of the amplitude value, the measurement accuracy is high and the processing is not required by the computer or the like for obtaining the measurement result. Therefore, it is possible to simultaneously measure the propagation delay characteristic and the amplitude characteristic of multiple waves at the same time.

〔Example〕

FIG. 1 shows a block diagram of a measuring apparatus for carrying out the method of the present invention.

The transmission signal generation unit 1 transmits the transmission antenna 3 via the transmission unit 2.
Connected to. The radio wave transmitted from the transmitting antenna 3 reaches the receiving antenna 4 via the radio wave propagation path 7. The receiving antenna 4 is connected to the measuring unit 6 via the receiving unit 5.

The radio wave propagation path 7 includes a main wave propagation path for propagating a radio wave at the shortest distance and a multiwave propagation path for propagating multiple waves generated by reflection, refraction, scattering and the like.

FIG. 2 shows a transmission signal output from the transmission signal generator 1.

The transmission signal output from the transmission signal generator 1 includes a reference signal 8 serving as a reference for time and amplitude, and a measurement signal 9 for measuring delay time and amplitude of multiple waves. With respect to this measurement signal 9, on the reception side, the amplitude of the reception measurement signal arriving via each propagation path is corrected by the reception amplitude value of the reference signal to obtain the amplitude characteristic, and from the time difference of the reception measurement signal, The delay characteristic can be obtained.

Here, the amplitude values of the reference signal 8 and the measurement signal 9 are A and B, respectively, and the time widths are C and D, respectively. Also,
The cycle time of the transmission signal is E, and the time from the measurement signal 9 to the next reference signal 8 is F. The pulse width of the time width C of the reference signal 8 is set to a value capable of holding the reference amplitude value in a part of the waveform even when waveform distortion occurs due to multiple waves in the radio wave propagation path 7. The time F is set longer than the maximum value of the propagation delay time to be measured. Time width D
Is set to be shorter than the minimum value of the propagation delay time due to the multipath.

FIG. 3 shows the output waveform of the transmitter 2.

The transmitter 2 amplitude-modulates the transmission signal at a frequency symmetrical to the measurement. This amplitude-modulated signal is transmitted from the transmitting antenna 3, reaches the receiving antenna 4 via the radio wave propagation path 7, and is detected by the receiving unit 5.

FIG. 4 shows an example of the waveform of the received signal detected by the receiver 5.

The received signal includes a received reference signal 8'corresponding to the reference signal 8 and a received measurement signal corresponding to the measurement signal. The received measurement signals are the main wave signal 9 ⁽⁰⁾ passing through the main wave propagation path and the multiple wave signals 9 ⁽¹⁾ , 9 ⁽²⁾
9 ⁽³⁾ , including ... Received reference signal 8 'amplitude and receiving measurement signals, respectively _{A', B 0 ', B} 1', B 2 ', B 3', ...
Is. Due to the propagation path length, the multiple wave signals 9 ⁽¹⁾ , 9 ⁽²⁾ , 9 ⁽³⁾ , ... Have delay times F ₁ , F ₂ , F ₃ after the main wave signal 9 ⁽⁰⁾ arrives. , ... comes after.

Here, even when the reception reference signal 8'is distorted by multiple waves, the reference amplitude value can be held by appropriately selecting the pulse width of the reference signal 8 on the transmission side. The propagation path length difference is obtained by dividing the speed of light by the delay times F ₁ , F ₂ , F ₃ , ....

FIG. 5 shows another example of the waveform of the received signal.

In this example, the amplitude A'of the received reference signal 8'and the main wave signal 9 '
The ratio of ^{(0) to} the amplitude B ₀ ′ is the amplitude A of the reference signal 8 on the transmitting side.
And the amplitude B of the measurement signal 9 are different. At this time, the absolute measurement of the amplitude ratio of the main wave can be performed by B '= (A' / A) × B.

FIG. 6 shows a received waveform including multiple wave components of the reference signal.

When the received waveform includes the multiple wave component 10 of the reference signal, the time interval between the reference signal 8 and the measurement signal 9 is selected to be equal to or greater than the maximum delay time of the multiple wave to be measured on the transmission side. As a result, the multiple wave component 10 of the reference signal can be prevented from occurring in the area of the received measurement signal.

FIG. 7 shows another received waveform including multiple wave components of the reference signal.

The transmission signal generator 1 alternately generates a transmission signal that does not include the measurement signal 9 and a transmission signal that includes the reference signal 8 and the measurement signal 9 for each cycle. The measuring unit 6 stores the multiple wave component of the reference signal in the period G that does not include the measurement signal 9, and corrects the received signal in the period H that includes the measurement signal 9 by this value.

In the above embodiments, a dedicated device was used on the transmission side, but the present invention can be similarly implemented by using a television signal as a transmission signal. The television signal uses amplitude modulation called vestigial sideband modulation, and uses a horizontal synchronizing signal as a reference signal. In that case, the measurement can be performed without the need to provide a special transmitter.

The table shows a comparison between the measuring method of the present invention and the conventional method.

[Effects of the Invention] As described above, the radio wave propagation characteristic measuring method of the present invention is characterized in that the delay time and the amplitude value due to the propagation path length of multiple waves generated by reflection, diffraction, scattering, etc. in the radio wave propagation path Two characteristics can be measured instantaneously and simultaneously. Therefore, many measurements in a short time are possible,
Further, there is an effect that the above two characteristics can be measured even while traveling by a car or the like.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a measuring apparatus for carrying out the present invention. FIG. 2 is a diagram showing a waveform of a transmission signal output from the transmission signal generator. FIG. 3 is a diagram showing an output waveform of the transmitter. FIG. 4 is a diagram showing an example of a received signal waveform. FIG. 5 is a diagram showing another example of the received signal waveform. FIG. 6 is a diagram showing a received waveform including multiple wave components of a reference signal. FIG. 7 is a diagram showing another received waveform including multiple wave components of the reference signal. 1 ... Transmission signal generating section, 2 ... Transmission section, 3 ... Transmission antenna, 4 ... Reception antenna, 5 ... Reception section, 6 ...
Measuring unit, 7 ... Radio wave propagation path, 8 ... Reference signal, 8 '...
… Reception reference signal, 9 …… Measurement signal, 9 ⁽⁰⁾ …… Main wave signal,
9 ⁽¹⁾ , 9 ⁽²⁾ , 9 ⁽³⁾ …… Multiple wave signal, 10 …… Multiple wave component of the reference signal.

Claims (1)

[Claims] 1. A radio wave propagation characteristic measuring method for measuring a delay characteristic and an amplitude characteristic of a signal propagating through a radio wave propagation path including a plurality of propagation paths generated by reflection, scattering or diffraction. Amplitude modulation of a reference signal with a long pulse width to obtain a substantially constant amplitude and a measurement signal with a short pulse width compared to the delay time difference caused by the lengths of the above multiple propagation paths with the measured frequency. Then, on the receiving side, the amplitude of the received measurement signal arriving via each propagation path is corrected by the received amplitude value of the reference signal to obtain the amplitude characteristic, and the delay characteristic is calculated from the time difference of the received measurement signal. A method for measuring the characteristics of radio wave propagation, which is characterized by finding.