JP2000115087A - Delay profile measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To find propagation conditions without using a special radio wave and a special receiver by using an existent radio wave. SOLUTION: An FFT(fast Fourier transform) computing element 1 converts a base-band signal to a frequency-axis signal through an FFT process and a pilot signal extractor 2 extracts only a pilot signal for amplitude and phase equalization which is arranged on the frequency axis from the frequency axis signal outputted from the FFT computing element 1. Then an amplitude and phase frequency characteristic detector 3 interpolates the pilot signal for amplitude and phase equalization and generates and outputs a frequency characteristic signal regarding the amplitude and phase. An IFFT(inverse fast Fourier transformation) computing element 4 finds the time-base signal of the output of the amplitude and phase frequency characteristic detector 3 and detects the electric energy to a delay time. The electric energy which is thus detected is displayed as a delay profile on a display unit 5 in a predetermined form and saved in a data storage device 6 when necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a delay profile measuring apparatus for measuring a radio wave propagation condition in a radio communication and broadcasting system such as a medium wave, a short wave, an ultra short wave and an ultra high frequency wave. The present invention relates to a method for measuring a delay profile of an OFDM signal in which a pilot signal is arranged at a position.

[0002]

2. Description of the Related Art Conventionally, an electric field intensity measuring device has been generally used for measuring a radio wave propagation state. This device is a system that measures the received electric field strength, but the electric field intensity measured by this device measures the combined electric field intensity of the direct wave and the reflected wave from the transmitting antenna, so that each of the direct wave and the reflected wave is measured. It was not possible to measure the propagation characteristics separately.

However, in the next generation terrestrial digital broadcasting currently being developed in Japan, a so-called single frequency network (SFN) in which a plurality of transmitting stations emit broadcast waves at the same frequency is also planned. Yes,
It is difficult to grasp a detailed propagation state only by measuring the combined electric field of a plurality of waves.

[0004] As a system for separating and measuring a plurality of radio waves, there is a "linear frequency modulation system" applied to, for example, a pulse compression radar. This technology is illustrated in FIG.
As shown in (b), when a signal whose frequency changes linearly with time is transmitted and the receiving side demodulates through a network (FIG. 5 (c)) whose delay time changes linearly with frequency, the received waveform becomes As shown in FIG. 5 (d), the delay time of a plurality of received radio waves can be measured by utilizing a sharp impulse waveform.

Although the above technique has a sufficient performance as a system for separating and measuring a plurality of received radio waves, a special radio wave is emitted and received by a special receiver for measuring a delay profile. However, there is a drawback in that a dedicated facility is required for this purpose. In addition, in this system, it is necessary to emit a special radio wave to measure the delay profile, so the broadcast and communication services are interrupted, or the measurement can be performed only during the time when these services are not performed. is there.

[0006]

As described above, in the measurement of the delay profile according to the prior art, it is necessary to emit a special radio wave and to receive the radio wave with a special receiver, which requires a dedicated facility. There is a disadvantage that. Also,
Since it is necessary to emit a special radio wave, there is a drawback that broadcasting and communication services are interrupted, or measurement can be performed only during a time period in which these services are not provided.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a delay profile measuring apparatus which can determine a propagation condition using an existing radio wave without using a special radio wave or a special receiver. To provide.

[0008]

To solve the above-mentioned problems, a delay profile measuring apparatus according to the present invention has the following characteristic configuration.

(1) FFT means for performing FFT processing on a digital baseband OFDM signal in which a pilot signal for amplitude / phase equalization is arranged at a predetermined carrier position, and the pilot signal is obtained from an FFT output of this means. A pilot signal extracting means for extracting, a specific estimating means for estimating an amplitude frequency characteristic and a phase frequency characteristic of an input signal from the pilot signal extracted by the means, an IFFT processing of the characteristic value estimated by this means, and an amplitude value And IFFT means for detecting a phase value.

(2) In the configuration of (1), further, display means for displaying the detected values of the amplitude value and the phase value obtained by the IFFT means on a screen, and detected amount storing means for storing the detected amounts. Prepare.

In the above configuration, the pilot signal arranged in the OFDM signal is extracted, and the power level delay profile is obtained from the amplitude and phase frequency characteristics of the pilot signal.
Propagation conditions are determined using existing radio waves without using special radio waves and special receivers.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS.

FIG. 1 shows a configuration of a delay profile measuring apparatus according to the present invention, which is installed at an arbitrary position as an input signal and is a digital baseband obtained by receiving and detecting a digital broadcast wave by an OFDM transmission system. A signal is provided. This signal is subjected to FFT processing by an FFT calculator 1 and converted from a signal on the time axis into a signal on the frequency axis, and then sent to the pilot signal extractor 2. The pilot signal extractor 2 extracts a pilot signal for amplitude and phase equalization, which is arranged on the frequency axis of the baseband signal. Here, the amplitude frequency characteristic and the phase frequency characteristic of the pilot signal are obtained. Each characteristic result is subjected to IFFT processing by the IFFT calculator 4, and the power amount with respect to the delay time is detected from the signal on the time axis. The detection result is displayed on the display 5 in the form of a delay profile, and is appropriately stored in the data storage 6.

In the above configuration, the measurement contents will be described below.

First, a synthesized wave when a desired wave is disturbed by multipath can be expressed as a vector as shown in FIG. In the frequency characteristic at this time, as shown in FIG. 3, dips occur at frequency intervals according to the reciprocal of the delay time. Therefore, in the delay profile measuring apparatus having the above configuration, the FFT operation unit 1 performs FFT processing on the baseband signal to convert the baseband signal into a frequency axis signal, and the pilot signal extractor 2 outputs the frequency axis signal of the FFT operation unit 1 The amplitude and amplitude are located on the frequency axis from the signal.
Only the pilot signal for phase equalization is extracted.

Subsequently, the amplitude / phase frequency characteristic detector 3 interpolates the pilot signal for amplitude / phase equalization to generate and output frequency characteristic signals relating to amplitude and phase. The IFFT calculator 4 obtains the time axis signal of the output of the amplitude / phase frequency characteristic detector 3, and detects the power amount with respect to the delay time. The detected power amount is displayed on the display 5 in a predetermined format as shown in FIG. 5 as a delay profile, and is stored in the data storage 6 if necessary.

According to the above processing, the pilot signal arranged in the OFDM signal is extracted, and the delay profile of the power level is obtained from the amplitude and phase frequency characteristics of the pilot signal. , The propagation condition can be obtained by using existing radio waves.

[0018]

As described above, according to the present invention, OFDM
The pilot signal allocated to the signal is extracted, and the delay profile of the power level is determined from the frequency characteristics of the amplitude and phase of the pilot signal.Therefore, existing radio waves can be used without using special radio waves or special receivers. Thus, a delay profile measuring device capable of determining a propagation condition can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a delay profile measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram expressing a combined wave in a case where interference is added to a desired wave by multipath in a vector manner.

FIG. 3 is a characteristic diagram showing frequency characteristics of the composite wave shown in FIG. 3;

FIG. 4 is an exemplary view showing a delay profile of a power amount according to the embodiment;

FIG. 5 shows a conventional multiple radio wave separation and measurement system.
FIG. 3 is a diagram for explaining a linear frequency modulation method already applied to a pulse compression radar.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... FFT calculator 2 ... Pilot signal extractor 3 ... Amplitude / phase frequency characteristic detector 4 ... IFFT calculator 5 ... Display 6 ... Data storage

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[Procedure amendment]

[Submission Date] September 6, 1999 (September 9, 1999)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

(1) FFT processing means for performing FFT processing on a digital baseband OFDM signal in which a pilot signal for amplitude / phase equalization is arranged at a predetermined carrier position, and an FFT output of this means Pilot signal extracting means for extracting the pilot signal from the input signal, characteristic estimating means for estimating an amplitude frequency characteristic and a phase frequency characteristic of an input signal from the pilot signal extracted by this means, and a characteristic value estimated by this means Processing to detect the amplitude value and the phase value, and based on the detection result,
Characteristic to calculate distribution of ability as delay profile information
Analysis means .

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

(2) In the configuration of (1), the characteristic solution
Display means for screen display the distribution of electric energy for the delay time difference obtained by the analysis means, the power amount for the time direction
Information storage means for storing information .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

In the above configuration, a pilot signal arranged in the OFDM signal is extracted from the FFT output , and the extracted
Each frequency of amplitude and phase of OFDM signal from Ilot signal
After estimating the characteristics, IFFT processing is applied to the amplitude and phase values.
Is detected, and from the detection result, the amount of power with respect to the delay time difference
The delay profile information by calculating the distribution of
As a result, it is possible to determine the propagation conditions using existing radio waves without using special radio waves and special receivers.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

Subsequently, the amplitude / phase frequency characteristic detector 3 interpolates the pilot signal for amplitude / phase equalization to generate and output frequency characteristic signals relating to amplitude and phase. The IFFT calculator 4 obtains the time axis signal of the output of the amplitude / phase frequency characteristic detector 3, and detects the power amount with respect to the delay time. The detected power amount is displayed as a delay profile on the display 5 in a predetermined format as shown in FIG. 4 , and stored in the data storage 6 if necessary.

[Procedure amendment 6]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Taku Suga 5-2-2-8 Akasaka, Minato-ku, Tokyo Inside the Next Generation Digital Television Broadcasting System Research Laboratories (72) Inventor Takao Hirakura Sachi-ku, Kawasaki-shi, Kanagawa No. 1 Komukai Toshiba-cho F-term in Toshiba Komukai Plant (reference) 5K042 AA00 AA06 BA11 CA02 CA23 DA00 DA01 DA04 DA15 DA19 EA15 FA00 GA00 HA02 LA09

Claims (2)

[Claims] 1. An FFT means for performing FFT processing on a digital baseband OFDM signal in which a pilot signal for amplitude / phase equalization is arranged at a predetermined carrier position, and extracting the pilot signal from an FFT output of the means. A pilot signal extracting means for performing the above, a specific estimating means for estimating an amplitude frequency characteristic and a phase frequency characteristic of an input signal from the pilot signal extracted by the means, an IFFT processing of the characteristic value estimated by this means, A delay profile measuring device comprising: IFFT means for detecting a phase value. 2. The apparatus according to claim 1, further comprising: display means for displaying on a screen the detected values of the amplitude value and the phase value obtained by said IFFT means; and detected amount storing means for storing the detected amounts. 2. The delay profile measurement device according to 1.