JP4191920B2 - Rounding interference measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to, for example, a wraparound disturbance measuring apparatus used for a medium wave, a short wave, a terrestrial / satellite / cable television relay transmitter, and other digital transmissions.
[0002]
[Prior art]
Currently, digitalization of terrestrial television broadcasting that is being broadcast in analog is underway, but from the viewpoint of effective use of frequency resources, the same program called SFN (Single Frequency Network) is used at the same frequency. Adoption of a broadcasting network for broadcasting is being considered. As one implementation method, a broadcast wave relay SFN method in which broadcast waves are received and retransmitted by a relay station has been studied, but in order to realize SFN by broadcast wave relay, cancellation of wraparound interference of relay stations is performed. Has become an issue.
[0003]
The situation of the sneak disturbance is expressed by the signal delay time and the level of the sneak path, and greatly depends on the sneak environment such as the surrounding environment of the relay station. In a station having a simple sneak disturbance environment with a small number of sneak waves, it is possible to improve the D / U by increasing the degree of separation between the transmitting antenna and the receiving antenna. On the other hand, it is impossible to improve D / U by countermeasures against antennas in a station having a multiple sneak jam environment where a large number of sneak currents exist.
[0004]
As a countermeasure, it is necessary to equip the relay station with a sneak canceller for multiple sneaking. In this case, since the hardware configuration is complicated and expensive, it is necessary to estimate from the planning stage of the relay station. However, at the planning stage, since broadcast waves are not actually transmitted, there is a problem that the wraparound environment of the relay station cannot be predicted.
[0005]
[Problems to be solved by the invention]
As described above, there is a problem that the wraparound environment cannot be predicted at the planning stage of installing the OFDM relay station.
[0006]
The present invention has been made in view of the above circumstances, and can measure the sneak interference of the target OFDM relay station quantitatively, and conduct a preliminary survey for predicting the sneak environment at the stage of planning digital broadcasting. It is an object of the present invention to provide a sneak jammer measuring device that can be used for the above.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the sneak disturbance measuring apparatus according to the present invention is used for a relay station that relays a standard television broadcast from a master station, and quantitatively measures a sneak jam when relaying an OFDM broadcast wave. A test signal generating means for generating a test signal generated by modulating a video carrier component of the standard television broadcast signal with a pseudo OFDM (orthogonal frequency division multiplexing) signal, and the standard television Switching means for sending out the test signal instead of the reception signal of John broadcast wave, and delay profile creating means for detecting a correlation between the signal received when the test signal is sent and the test signal to obtain a delay profile It is characterized by doing.
[0008]
Further, in the above-mentioned configuration, in the state where the received signal of the standard television broadcast wave is retransmitted by the switching setting of the switching means, the video peak power of the received signal is detected, and the electric field of the master station transmitted wave is detected. Intensity data is acquired, the image peak power of the received signal at the time of the test signal transmission is detected, the electric field fluctuation of the local station sneak wave is monitored, and the wraparound D is compared with the field intensity data of the master station transmission wave. And a wraparound D / U ratio variation range confirmation means for confirming the variation range of the / U ratio.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0010]
FIG. 1 shows a configuration of an embodiment to which a wraparound disturbance measuring apparatus according to the present invention is applied, assuming that a standard television (NTSC) broadcast relay apparatus is used for OFDM terrestrial digital television broadcasting. FIG.
[0011]
In FIG. 1, the RF input signal received by the receiving antenna 11 is frequency-converted from the radio frequency band to the intermediate frequency band by the reception conversion unit 12 and becomes an IF signal. The IF signal is compensated for transmission path distortion by the compensator 13 and then supplied to the transmission conversion unit 14 via a switching unit (SW) 211 constituting a wraparound disturbance measuring device 21 to be described later. To the original radio frequency band. The output signal of the transmission conversion unit 14 is amplified by the amplifier 15 and then transmitted from the transmission antenna 16 to the space.
[0012]
In contrast to the NTSC broadcast relay device, the measuring device 21 according to the present invention is configured as follows. First, the test signal generator 212 modulates the video carrier portion of the NTSC signal with a pseudo OFDM signal and converts it to an intermediate frequency band to generate a test signal.
[0013]
FIG. 2 shows an example of a test signal generated by the test signal generator 212. FIG. 2 (a) is an NTSC signal with a certain value added as a video signal, and FIG. 2 (b) is a video carrier. This is a pseudo OFDM signal using a frequency band. The test signal generation unit 212 generates these NTSC signals and pseudo OFDM signals, switches them to pseudo OFDM signals in the video carrier portion of the NTSC signals, and derives them as shown in FIG. 2 (c). An NTSC signal obtained by modulating a video carrier with an OFDM signal is generated. A test signal is obtained by converting the NTSC signal to an intermediate frequency band.
[0014]
The test signal of the intermediate frequency band generated in this way is supplied to the switching unit 211 and also supplied to the correlation detection unit 213.
[0015]
The switching unit 211 switches the input system according to a test ON / OFF signal from an instruction input device (not shown). When the test is ON, the test signal generated by the test signal generation unit 212 is derived, and when the test is OFF, compensation is performed. A normal NTSC signal from the generator 13 is derived.
[0016]
When a test signal is selected by the switching unit 211 when the test is ON, the test signal is transmitted from the transmission antenna 16 to the space via the transmission conversion unit 14 and the amplifier 15 and received by the reception antenna 11 by wraparound. The reception signal at this time is supplied to the reception conversion unit 214 of the measurement apparatus 21, converted into an intermediate frequency band signal, and then supplied to the correlation detector 213 and the peak detector 215.
[0017]
The correlation detector 213 obtains a delay amount and an amplitude / phase change amount due to wraparound by taking a cross-correlation between the test signal from the test signal generator 212 and the received signal from the reception conversion unit 214. Information obtained by the correlation detector 213 is averaged by the averaging processing unit 216 and output as a delay profile indicating an impulse response of the sneak path.
[0018]
On the other hand, the peak detector 215 detects the image peak power from the output of the reception conversion unit 212 both when receiving a normal NTSC transmission wave and when receiving a test signal. Thereby, the electric field fluctuation of the parent station transmission wave and the electric field fluctuation of the local station sneak wave are monitored.
[0019]
The operation of the above configuration will be described with reference to FIG.
[0020]
First, in the broadcast time zone of the NTSC transmission wave, the switching unit 211 is set on the compensator output side by a test OFF command, and relay transmission is performed. At this time, in the measurement device 21, the received signal is captured and converted into an intermediate frequency band by the reception conversion unit 214, and the image peak power is detected by the peak detector 215. Thereby, the electric field strength data of the master station transmission wave can be acquired and its fluctuation can be monitored.
[0021]
Next, when the NTSC transmission wave is paused, the switching unit 211 is set to the test signal side by the test ON command, the test signal carrying the pseudo OFDM signal is transmitted from the transmission antenna 16, and the sneak signal received by the reception antenna 11 Capture. This sneak signal is converted into an intermediate frequency band by the reception conversion unit 214 and supplied to the peak detector 215, and the image peak power is detected. Thereby, the electric field fluctuation | variation of a local station sneak wave can be monitored, and the fluctuation | variation range of a wraparound D / U ratio can be confirmed by comparing with the electric field strength data of a master station transmission wave.
[0022]
The output of the reception conversion unit 214 is supplied to the correlation detector 213 together with the test signal output from the test signal generator 212, and the delay amount and amplitude / phase change amount due to the wraparound are obtained by the correlation detection, and the average processing unit 216 is obtained. By the above averaging, a delay profile indicating the impulse response of the sneak path is obtained.
[0023]
Therefore, by using the measuring apparatus having the above configuration, it is possible to estimate the sneak environment unique to the station from the delay profile data, and to check the fluctuation range of the sneak D / U ratio from the data of the parent station electric field strength. it can. This makes it possible to predict the wraparound environment of the digital TV relay station by utilizing the current analog TV relay station.
[0024]
In the above embodiment, the test signal is described as being generated by switching between the NTSC signal and the pseudo OFDM signal. However, the waveform data of the test signal is stored in advance in a memory device such as a ROM, and is read out and output as appropriate. May be.
[0025]
【The invention's effect】
As described above, according to the present invention, it is possible to quantitatively measure the sneak interference of the target OFDM relay station, and it can be used for a preliminary survey for predicting the sneak environment at the stage of digital broadcasting planning. A wraparound disturbance measuring device can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment to which a wraparound disturbance measuring apparatus according to the present invention is applied.
FIG. 2 is a waveform diagram showing an example of a test signal generated by a test signal generation unit 212 of the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Reception antenna 12 ... Reception conversion part 13 ... Compensator 14 ... Transmission conversion part 15 ... Amplifier 16 ... Transmission antenna 21 ... Circulation disturbance measuring device 211 ... Switching part (SW)
212 ... Test signal generation unit 213 ... Correlation detection unit 214 ... Reception conversion unit 215 ... Peak detector 216 ... Average processing unit

Claims (3)

Using a relay station for receiving and relaying television broadcast wave of the NTSC system from the master station, a wraparound interference measuring apparatus for quantitatively measuring the wraparound interference when relaying an OFDM broadcast wave,
A test signal generating means for generating a test signal by replacing a video carrier portion in the NTSC television broadcast signal with a pseudo OFDM (orthogonal frequency division multiplexing) signal using a frequency band of the NTSC video carrier ;
Switching means for sending the test signal to the relay transmission unit in place of the reception signal of the NTSC television broadcast wave in accordance with a test execution command given at the time of relay suspension of the NTSC television broadcast wave ;
A wraparound disturbance measuring apparatus comprising delay profile creating means for obtaining a delay profile by detecting a correlation between a signal received when the test signal is transmitted and the test signal. The switch setting before Symbol switching means, in a state in which retransmits the received signal of the television broadcasting wave of the NTSC system, by detecting the video peak power of the received signal, the field strength data of the parent station transmission waves Obtaining and detecting the image peak power of the received signal at the time of sending the test signal, monitoring the electric field fluctuation of the local station sneak wave, and comparing it with the field strength data of the master station transmission wave, the sneak D / U ratio The wraparound disturbance measuring apparatus according to claim 1, further comprising: a wraparound D / U ratio variation range confirming unit configured to confirm a variation range of the sneak path.   The wraparound disturbance measuring apparatus according to claim 1, wherein the test signal generating means includes a memory device in which waveform data of the test signal is stored.

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