JP5712116B2 - Strain measuring method and strain measuring apparatus - Google Patents

Strain measuring method and strain measuring apparatus Download PDF

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JP5712116B2
JP5712116B2 JP2011265784A JP2011265784A JP5712116B2 JP 5712116 B2 JP5712116 B2 JP 5712116B2 JP 2011265784 A JP2011265784 A JP 2011265784A JP 2011265784 A JP2011265784 A JP 2011265784A JP 5712116 B2 JP5712116 B2 JP 5712116B2
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稔久 藤原
稔久 藤原
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Nippon Telegraph and Telephone East Corp
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Description

本発明は、伝送路の歪特性を測定する技術に関する。   The present invention relates to a technique for measuring distortion characteristics of a transmission line.

テレビ放送などのＲＦ映像信号を伝送する同軸伝送路の品質の測定は、同軸伝送路の品質を直接測るのではなく、伝送路に流れる信号品質を測定していた。アナログ放送の場合、ノイズはホワイトノイズ、歪は縞模様などのように別の現象として確認できていたが、デジタル放送では、同軸伝送路の特性（ノイズ、歪）の両方が同じＢＥＲ（ビット誤り率）の劣化として現れるため、故障原因の特定を難しくしている。   Measurement of the quality of a coaxial transmission line that transmits an RF video signal, such as television broadcasting, is not the direct measurement of the quality of the coaxial transmission line, but the quality of the signal flowing through the transmission line. In the case of analog broadcasting, noise was confirmed as a separate phenomenon such as white noise and distortion was a striped pattern. However, in digital broadcasting, both the characteristics (noise and distortion) of the coaxial transmission line are the same. Rate), it is difficult to identify the cause of the failure.

実験室においては、マルチチャネル信号発生器（ＣＷ信号を放送信号の数・周波数分送出する装置）を利用し、スペクトラムアナライザを受信器に用いて同軸伝送路のノイズ・歪を測定することができる。   In the laboratory, it is possible to measure the noise and distortion of a coaxial transmission line by using a multi-channel signal generator (apparatus that transmits CW signals for the number and frequency of broadcast signals) and using a spectrum analyzer as a receiver. .

また、特許文献１には、ＣＡＴＶシステムの伝送路の周波数特性を測定するためにホワイトノイズを用いる発明が開示されている。   Patent Document 1 discloses an invention that uses white noise to measure the frequency characteristics of a transmission line of a CATV system.

特開平６−３７６７６号公報JP-A-6-37676

しかしながら、マルチチャネル信号発生器は高価で、大型であり、ユーザ宅内の同軸ケーブル区間を測定するために用いることは難しい。   However, multi-channel signal generators are expensive and large, and are difficult to use to measure coaxial cable sections in a user's home.

本発明は、上記に鑑みてなされたものであり、簡易な方法で同軸伝送路の歪を測定することを目的とする。   The present invention has been made in view of the above, and an object thereof is to measure the distortion of a coaxial transmission line by a simple method.

第１の本発明に係る歪測定方法は、テレビ放送信号を伝送する同軸ケーブルで接続された伝送路の歪を測定する歪測定方法であって、ホワイトノイズを発生して前記伝送路に入力するステップと、前記伝送路を伝送した前記ホワイトノイズの出力信号レベルを測定するステップと、前記伝送路に入力するホワイトノイズの入力信号レベルを変化させるステップと、前記入力信号レベルを変化させた後に前記出力信号レベルを測定し、前記入力信号レベルの変化に対する前記出力信号レベルの変化が非線形で追従する場合に歪が発生したと判断するステップと、を有することを特徴とする。   A distortion measurement method according to a first aspect of the present invention is a distortion measurement method for measuring distortion of a transmission line connected by a coaxial cable for transmitting a television broadcast signal, and generates white noise and inputs the white noise to the transmission line. Measuring the output signal level of the white noise transmitted through the transmission line; changing the input signal level of white noise input to the transmission line; and after changing the input signal level, Measuring the output signal level, and determining that distortion has occurred when the change in the output signal level with respect to the change in the input signal level follows non-linearly.

上記の歪測定方法において、前記入力信号レベルに対する前記出力信号レベルを測定した測定結果それぞれについて、前記測定結果のうち前記入力信号レベルが低い前記測定結果を通る基準直線から前記測定結果それぞれについて前記出力信号レベルが圧縮されている圧縮度合いを求めるステップと、圧縮度合いとその圧縮度合いのときに歪が発生した入力信号レベルのマージンを示すバックオフを対応付けたバックオフテーブルを参照し、前記測定結果それぞれの圧縮度合いから前記バックオフを求めて前記伝送路の歪が発生した入力信号レベルを算出するステップと、を有することを特徴とする。   In the above distortion measurement method, for each measurement result obtained by measuring the output signal level with respect to the input signal level, the output for each measurement result from a reference straight line passing through the measurement result having the low input signal level among the measurement results. A step of obtaining a compression level in which the signal level is compressed, and a measurement result obtained by referring to a backoff table in which a compression level is associated with a backoff indicating a margin of an input signal level in which distortion occurs at the compression level. Calculating the input signal level at which the distortion of the transmission path has occurred by obtaining the back-off from each degree of compression.

第２の本発明に係る歪測定装置は、テレビ放送信号を伝送する同軸ケーブルで接続された伝送路の歪を測定する歪測定装置であって、ホワイトノイズを発生して前記伝送路に入力するホワイトノイズ発生手段と、前記伝送路を伝送した前記ホワイトノイズの出力信号レベルを測定する測定手段と、前記ホワイトノイズ発生手段が前記ホワイトノイズの入力信号レベルを変化させたときに、前記入力信号レベルの変化に対する前記出力信号レベルの変化が非線形で追従する場合に歪が発生したと判断する歪判定手段と、を有することを特徴とする。   A distortion measuring apparatus according to a second aspect of the present invention is a distortion measuring apparatus that measures distortion of a transmission line connected by a coaxial cable that transmits a television broadcast signal, and generates white noise and inputs the generated noise to the transmission line. White noise generating means, measuring means for measuring the output signal level of the white noise transmitted through the transmission line, and the input signal level when the white noise generating means changes the input signal level of the white noise. Distortion determining means for determining that distortion has occurred when the change in the output signal level with respect to the change follows non-linearly.

上記歪測定装置において、前記入力信号レベルに対する前記出力信号レベルを測定した測定結果それぞれについて、前記測定結果のうち前記入力信号レベルが低い前記測定結果を通る基準直線から前記測定結果それぞれについて前記出力信号レベルが圧縮されている圧縮度合いを求め、圧縮度合いとその圧縮度合いのときに歪が発生した入力信号レベルのマージンを示すバックオフを対応付けたバックオフテーブルを参照し、前記測定結果それぞれの圧縮度合いから前記バックオフを求めて前記伝送路の歪が発生した入力信号レベルを算出する入力判定手段を有することを特徴とする。   In the distortion measurement apparatus, for each measurement result obtained by measuring the output signal level relative to the input signal level, the output signal for each measurement result from a reference straight line passing through the measurement result having the low input signal level among the measurement results. The level of compression is obtained, and the compression of each of the measurement results is referred to by referring to a backoff table that associates the degree of compression with a backoff indicating a margin of the input signal level at which the distortion occurs at the degree of compression. It has an input determining means for calculating the input signal level where the transmission path distortion occurs by obtaining the back-off from the degree.

本発明によれば、簡易な方法で同軸伝送路の歪を測定することができる。   According to the present invention, the distortion of the coaxial transmission line can be measured by a simple method.

本実施の形態における歪測定装置を含む全体構成図である。1 is an overall configuration diagram including a strain measuring device in the present embodiment. 本実施の形態で利用するホワイトノイズを示す模式図である。It is a schematic diagram which shows the white noise utilized in this Embodiment. ホワイトノイズの信号レベルを変化させて同軸区間の通過損失を測定する様子を示す図である。It is a figure which shows a mode that the signal loss of a white noise is changed and the passage loss of a coaxial area is measured. 図３の測定結果を横軸に入力パワー、縦軸に出力をとりプロットした飽和特性グラフである。4 is a saturation characteristic graph in which the measurement results of FIG. 3 are plotted with the input power on the horizontal axis and the output on the vertical axis. 基準直線をプロットして圧縮度合いを求める様子を示す図である。It is a figure which shows a mode that a reference | standard straight line is plotted and the compression degree is calculated | required. 各入力パワーにおける圧縮度合いの測定結果の例を示す図である。It is a figure which shows the example of the measurement result of the compression degree in each input power. 飽和特性グラフにバックオフを描画した例を示す図である。It is a figure which shows the example which drawn the back-off on the saturation characteristic graph. 各測定点のバックオフを求めるバックオフテーブルの例を示す図である。It is a figure which shows the example of the back-off table which calculates | requires the back-off of each measurement point. 測定結果の例を示す図である。It is a figure which shows the example of a measurement result. 本実施の形態における歪測定装置の表示例を示す図である。It is a figure which shows the example of a display of the distortion | strain measuring apparatus in this Embodiment.

以下、本発明の実施の形態について図面を用いて説明する。   Hereinafter, embodiments of the present invention will be described with reference to the drawings.

図１は、本実施の形態における歪測定装置を含む全体構成図である。本実施の形態における歪測定装置は、ホワイトノイズ発生器１１と測定器１２を有する。   FIG. 1 is an overall configuration diagram including a strain measuring apparatus according to the present embodiment. The distortion measuring apparatus in the present embodiment includes a white noise generator 11 and a measuring instrument 12.

ホワイトノイズ発生器１１は、全ての周波数でほぼ同じ信号レベルのホワイトノイズを発生し、テレビ放送信号を伝送する同軸ケーブルで接続された伝送路である同軸区間１００に入力する。同軸区間１００内には、ブースタ、分配器などの機器を含む。   The white noise generator 11 generates white noise having substantially the same signal level at all frequencies, and inputs the white noise to a coaxial section 100 that is a transmission path connected by a coaxial cable that transmits a television broadcast signal. The coaxial section 100 includes devices such as a booster and a distributor.

測定器１２は、スペクトラムアナライザであり、同軸区間１００を伝送したホワイトノイズの出力信号レベルを周波数領域で測定し、歪の測定、正常な入力レベルの判定をする。   The measuring instrument 12 is a spectrum analyzer, and measures the output signal level of white noise transmitted through the coaxial section 100 in the frequency domain to measure distortion and determine a normal input level.

図２に示すように、歪の測定は、ホワイトノイズ発生器１１でデジタル放送のＲＦ信号の周波数帯域を含むホワイトノイズを発生し、発生したホワイトノイズの入力信号レベルを変化させて、測定器１２で出力信号レベルの変化を追うことにより行う。同軸区間１００に入力したホワイトノイズの入力信号レベルの変化に対する測定器１２で測定した出力信号レベルの変化が非線形に追従する場合に歪が発生したと判断する。同軸区間１００が完全な直線性を持つ場合、ホワイトノイズ発生器１１で上げた入力信号レベルに比例して測定器１２で測定されるホワイトノイズの出力信号レベルも大きくなる。同軸区間１００にブースタを含む場合、ホワイトノイズの入力信号レベルを上げていくとブースタの出力が限界に達して飽和し、上げた入力信号レベルに比べて測定器１２で測定されるホワイトノイズの出力信号レベルの増加量が低下する。低下した量が所定の値（例えば１ｄＢ）に達した時に歪が発生したと判定する。例えば、ホワイトノイズの入力信号レベルを３ｄＢ上げたときに、測定器１２において２ｄＢしか出力信号レベルが上がっていない場合に歪が発生したと判断する。   As shown in FIG. 2, the distortion is measured by generating white noise including the frequency band of the digital broadcast RF signal with the white noise generator 11, and changing the input signal level of the generated white noise, thereby measuring the instrument 12. This is done by following the change in the output signal level. When the change in the output signal level measured by the measuring instrument 12 with respect to the change in the input signal level of white noise input to the coaxial section 100 follows non-linearly, it is determined that distortion has occurred. When the coaxial section 100 has perfect linearity, the output signal level of white noise measured by the measuring instrument 12 increases in proportion to the input signal level raised by the white noise generator 11. When the booster is included in the coaxial section 100, when the input signal level of white noise is increased, the output of the booster reaches a limit and is saturated, and the output of white noise measured by the measuring instrument 12 compared to the increased input signal level. The increase in signal level is reduced. It is determined that distortion has occurred when the reduced amount reaches a predetermined value (for example, 1 dB). For example, when the input signal level of white noise is increased by 3 dB, it is determined that distortion has occurred when the output signal level of the measuring instrument 12 is only increased by 2 dB.

次に、この歪量から正常な入力信号レベルを判定する手順について説明する。測定器１２で測定されるホワイトノイズの増加量の圧縮度が、所定の値を超えたときには、既に、ブースタへの正常な入力信号レベルを超過している場合がある。これはホワイトノイズによる簡易測定では、微細な圧縮度を検出できないためである。これを補うためには、所定の圧縮レベルを観測した入力信号レベルから、所定のマージン（バックオフ）を圧縮が発生した入力信号レベル引いた値を以って、歪が発生する入力信号レベルと判定する。判定をより正確なものにするために、圧縮度を検出できる複数の入力信号レベルからもとめた入力信号レベルの平均を計算する。以下、処理の流れを説明する。   Next, a procedure for determining a normal input signal level from the distortion amount will be described. When the degree of compression of the increase amount of white noise measured by the measuring instrument 12 exceeds a predetermined value, the normal input signal level to the booster may already be exceeded. This is because fine compression cannot be detected by simple measurement using white noise. In order to compensate for this, the input signal level at which a predetermined compression level is observed is subtracted from the input signal level at which compression is generated by subtracting a predetermined margin (backoff) from the input signal level at which the predetermined compression level is observed. judge. In order to make the determination more accurate, an average of the input signal levels obtained from a plurality of input signal levels capable of detecting the degree of compression is calculated. Hereinafter, the flow of processing will be described.

まず、ホワイトノイズの入力信号レベルを変化させて同軸区間１００の通過損失を低レベル側から順次測定する。図３に示す例では、標準入力（０ｄＢｍ／２．１ＧＨｚ）に対して、−３０，−２０，−１０，０，＋１０，＋２０ｄＢの入力パワーでホワイトノイズを入力し、標準入力の通過特性を基準にした正規化出力を求める。   First, the input signal level of white noise is changed, and the passage loss of the coaxial section 100 is sequentially measured from the low level side. In the example shown in FIG. 3, white noise is input with input power of −30, −20, −10, 0, +10, and +20 dB with respect to the standard input (0 dBm / 2.1 GHz), and the pass characteristic of the standard input is obtained. Find the standardized normalized output.

続いて、測定対象の帯域の正規化出力を入力パワー毎に平均して飽和特性グラフを描画する。図４に示す例では、ＵＨＦ帯（４７０−７７０ＭＨｚ）の正規化出力を入力パワー毎に平均し、横軸に入力パワー、縦軸に正規化出力をとって測定点を飽和特性グラフにプロットした。   Subsequently, the normalized output of the band to be measured is averaged for each input power, and a saturation characteristic graph is drawn. In the example shown in FIG. 4, the normalized output in the UHF band (470-770 MHz) is averaged for each input power, the input power is plotted on the horizontal axis, and the normalized output is plotted on the vertical axis, and the measurement points are plotted on a saturation characteristic graph. .

続いて、飽和特性グラフに入力パワーの低い測定点を通る基準直線を描き、各測定点について、基準直線からの圧縮度合いを検査する。図５に飽和特性グラフに基準直線を描いた様子を示す。本実施の形態では、測定点のうちからピボットと呼ぶ固定の点を選び、ピボットを通る傾き１の直線を基準直線として描画する。ピボットとなる点は任意に設定可能である。図５では、入力パワーが−２０ｄＢの測定点（図５中の●）をピボットとした。そして、ピボットの入力パワーを超える測定点について、基準直線からの圧縮度合いを検査する。図５に示す例では、ピボットとした測定点の入力パワー（−２０ｄＢ）を超える−１０，０，＋１０，＋２０ｄＢの測定点について圧縮度合いを求めた。図６に測定結果を示す。   Subsequently, a reference line passing through a measurement point with low input power is drawn on the saturation characteristic graph, and the degree of compression from the reference line is inspected for each measurement point. FIG. 5 shows a state in which a reference straight line is drawn on the saturation characteristic graph. In the present embodiment, a fixed point called a pivot is selected from the measurement points, and a straight line having an inclination of 1 passing through the pivot is drawn as a reference straight line. The point used as a pivot can be set arbitrarily. In FIG. 5, a measurement point (● in FIG. 5) where the input power is −20 dB is defined as a pivot. Then, the degree of compression from the reference straight line is inspected for measurement points that exceed the input power of the pivot. In the example shown in FIG. 5, the degree of compression was obtained for measurement points of −10, 0, +10, +20 dB exceeding the input power (−20 dB) of the measurement point as a pivot. FIG. 6 shows the measurement results.

そして、圧縮度合いから歪が発生する入力信号レベルＹを求めて飽和特性グラフに描画する。図７に、飽和特性グラフに歪が発生する入力信号レベルＹを描画した例を示す。入力信号レベルＹは、各測定点の入力信号レベルからその測定点での圧縮度合いに対応するバックオフを減算した値を平均することで算出する。このとき圧縮度合いが所定の範囲内のものは測定誤差としてバックオフ算出対象から外す。圧縮度合いに対応するバックオフは、圧縮度合いとバックオフとを対応付けたバックオフテーブルから求める。図９にバックオフテーブルの例を示す。   Then, the input signal level Y at which distortion occurs from the degree of compression is obtained and drawn on the saturation characteristic graph. FIG. 7 shows an example in which the input signal level Y at which distortion occurs in the saturation characteristic graph is drawn. The input signal level Y is calculated by averaging the value obtained by subtracting the back-off corresponding to the degree of compression at the measurement point from the input signal level at each measurement point. At this time, a compression degree within a predetermined range is excluded from the backoff calculation target as a measurement error. The backoff corresponding to the degree of compression is obtained from a backoff table in which the degree of compression is associated with the backoff. FIG. 9 shows an example of the back-off table.

ここで、歪が発生する入力信号レベルＹの算出処理を具体的に説明する。本実施の形態では、圧縮度合いが１ｄＢ以内のものは測定誤差としてバックオフ算出対象からはずすので、入力パワーが−１０，０ｄＢの測定点はバックオフ算出対象から外す。入力パワーが１０ｄＢの圧縮度合いは−１．４ｄＢであるので、バックオフテーブルからバックオフはＸ２となる。入力パワーが２０ｄＢの圧縮度合いは−２．６ｄＢであるのでバックオフはＸ５となる。そして、各測定点の入力パワーからバックオフを引いた値を平均して歪が発生する入力信号レベルＹを求める。つまり、Ｙ＝ａｖｅｒａｇｅ（１０−Ｘ２，２０−Ｘ５）を計算して入力信号レベルＹを求める。   Here, the calculation process of the input signal level Y in which distortion occurs will be specifically described. In the present embodiment, since the compression level within 1 dB is excluded from the backoff calculation target as a measurement error, the measurement point with the input power of −10, 0 dB is excluded from the backoff calculation target. Since the compression degree when the input power is 10 dB is -1.4 dB, the back-off is X2 from the back-off table. Since the compression degree when the input power is 20 dB is -2.6 dB, the back-off is X5. Then, an input signal level Y at which distortion occurs is obtained by averaging values obtained by subtracting back-off from the input power at each measurement point. That is, Y = average (10−X2, 20−X5) is calculated to obtain the input signal level Y.

そして、入力信号レベルＹと判定基準値Ｓの大小を比較して正常な入力レベルであるか否かを判定する。例えば、判定基準値Ｓを０ｄＢとすると、図８で示した例は、入力信号レベルＹが０ｄＢよりも小さいので判定結果はＮＧとなる。   Then, the input signal level Y and the determination reference value S are compared to determine whether the input level is normal. For example, if the determination reference value S is 0 dB, the determination result is NG because the example shown in FIG. 8 has the input signal level Y lower than 0 dB.

次に、ユーザ宅で歪測定を行う例について説明する。   Next, an example in which distortion measurement is performed at the user's home will be described.

ユーザ宅では、デジタル放送信号は、屋根等に設置されたアンテナで受信され、ブースタを経由して分配器により各部屋のＲＦ端子に伝送されてテレビに入力される。また、光ネットワークを用いたＩＰ再送信サービスを利用する場合は、デジタル放送信号がユーザ宅内のＯＮＵ（Ｏｐｔｉｃａｌ Ｎｅｔｗｏｒｋ Ｕｎｉｔ）まで光信号で伝送されてＯＮＵで電気信号に変換される。そして、電気信号に変換されたデジタル放送信号は、ブースタを経由して分配器により各部屋のＲＦ端子に伝送される。   At the user's house, the digital broadcast signal is received by an antenna installed on a roof or the like, transmitted to the RF terminal of each room by a distributor via a booster, and input to the television. When an IP retransmission service using an optical network is used, a digital broadcast signal is transmitted as an optical signal to an ONU (Optical Network Unit) in the user's house and converted into an electric signal by the ONU. The digital broadcast signal converted into an electric signal is transmitted to the RF terminal of each room by a distributor via a booster.

まず、ホワイトノイズ発生器１１をアンテナあるいはＯＮＵの出力先に接続し、測定器１２をテレビに入力される同軸ケーブルに接続する。   First, the white noise generator 11 is connected to an antenna or an ONU output destination, and the measuring device 12 is connected to a coaxial cable input to the television.

そして、ホワイトノイズ発生器１１からホワイトノイズを発生してユーザ宅内の同軸区間に入力し、測定器１２で同軸区間に入力されたホワイトノイズを検出する。   Then, white noise is generated from the white noise generator 11 and input to the coaxial section in the user's home, and the white noise input to the coaxial section is detected by the measuring device 12.

その後、ホワイトノイズの入力信号レベルを変化させた後に、測定器１２で同軸区間を伝送したホワイトノイズの出力信号レベルを測定し、入力信号レベルの変化に対する出力信号レベルの変化が非線形で追従する場合に歪が発生したと判断する。   After that, after changing the white noise input signal level, the measuring device 12 measures the white noise output signal level transmitted through the coaxial section, and the change in the output signal level with respect to the change in the input signal level follows non-linearly. It is determined that distortion has occurred.

図９に、横軸に周波数（ＭＨｚ）、縦軸にゲイン圧縮（ｄＢ）を取った正常時の測定結果と異常時の測定結果の例を示す。ここでは、ケーブルテレビや地上デジタル放送の周波数帯域（約９０〜７７０ＭＨｚ）、ＢＳ・ＣＳデジタル放送の周波数帯域（約１〜２ＧＨｚ）においてゲイン圧縮が１ｄＢに達したときに歪が発生したと判断する。   FIG. 9 shows an example of a normal measurement result and an abnormal measurement result with the frequency (MHz) on the horizontal axis and the gain compression (dB) on the vertical axis. Here, it is determined that distortion has occurred when the gain compression reaches 1 dB in the frequency band of cable television or terrestrial digital broadcasting (about 90 to 770 MHz) and the frequency band of BS / CS digital broadcasting (about 1 to 2 GHz). .

図９（ａ）の正常時測定結果では、トータル入力レベルが１１０ｄＢｕＶで歪が発生しているのに対し、図９（ｂ）の異常時測定結果では、トータル入力レベルがより小さい９０ｄＢｕＶで歪が発生している。図９（ｂ）では、同軸区間１００に設置されたブースタの飽和が早いか発振していると考えられる。   In the normal measurement result in FIG. 9A, distortion occurs when the total input level is 110 dBuV, whereas in the abnormal measurement result in FIG. 9B, distortion occurs at 90 dBuV where the total input level is smaller. It has occurred. In FIG. 9B, it is considered that the booster installed in the coaxial section 100 is saturated early or oscillates.

図１０は、本実施の形態における測定器１２の表示例を示す図である。   FIG. 10 is a diagram showing a display example of the measuring instrument 12 in the present embodiment.

図１０に示す表示例では、テレビ放送に利用される周波数帯を８つに分類し、８つの周波数帯それぞれについて歪特性を測定して表示している。   In the display example shown in FIG. 10, the frequency bands used for television broadcasting are classified into eight, and distortion characteristics are measured and displayed for each of the eight frequency bands.

以上説明したように、本実施の形態によれば、ホワイトノイズ発生器１１でホワイトノイズを発生させてユーザ宅内の同軸区間１００に入力し、ホワイトノイズの入力信号レベルを変化させて、測定器１２で同軸区間１００を伝送したホワイトノイズの出力信号レベルの変化を測定し、その変化が非線形で追従する場合に歪が発生したと判断することにより、簡易な方法で同軸伝送路の歪を測定することができる。   As described above, according to the present embodiment, white noise is generated by the white noise generator 11 and input to the coaxial section 100 in the user's home, and the input signal level of the white noise is changed. Measure the distortion of the coaxial transmission line by a simple method by measuring the change in the output signal level of the white noise transmitted through the coaxial section 100 and determining that distortion has occurred when the change follows non-linearly. be able to.

１１…ホワイトノイズ発生器
１２…測定器
１００…同軸区間 11 ... White noise generator 12 ... Measuring instrument 100 ... Coaxial section

Claims (4)

テレビ放送信号を伝送する同軸ケーブルで接続された伝送路の歪を測定する歪測定方法であって、
ホワイトノイズを発生して前記伝送路に入力するステップと、
前記伝送路を伝送した前記ホワイトノイズの出力信号レベルを測定するステップと、
前記伝送路に入力するホワイトノイズの入力信号レベルを変化させるステップと、
前記入力信号レベルを変化させた後に前記出力信号レベルを測定し、前記入力信号レベルの変化に対する前記出力信号レベルの変化が非線形で追従する場合に歪が発生したと判断するステップと、
を有することを特徴とする歪測定方法。 A distortion measurement method for measuring distortion of a transmission line connected by a coaxial cable for transmitting a television broadcast signal,
Generating white noise and inputting it into the transmission line;
Measuring an output signal level of the white noise transmitted through the transmission path;
Changing an input signal level of white noise input to the transmission path;
Measuring the output signal level after changing the input signal level and determining that distortion has occurred when the change in the output signal level with respect to the change in the input signal level follows non-linearly;
A strain measurement method comprising: 前記入力信号レベルに対する前記出力信号レベルを測定した測定結果それぞれについて、前記測定結果のうち前記入力信号レベルが低い前記測定結果を通る基準直線から前記測定結果それぞれについて前記出力信号レベルが圧縮されている圧縮度合いを求めるステップと、
圧縮度合いとその圧縮度合いのときに歪が発生した入力信号レベルのマージンを示すバックオフを対応付けたバックオフテーブルを参照し、前記測定結果それぞれの圧縮度合いから前記バックオフを求めて前記伝送路の歪が発生した入力信号レベルを算出するステップと、
を有することを特徴とする請求項１記載の歪測定方法。 For each measurement result obtained by measuring the output signal level relative to the input signal level, the output signal level is compressed for each measurement result from a reference line passing through the measurement result having the low input signal level among the measurement results. Determining the degree of compression;
Refer to a back-off table in which a compression level and a back-off indicating a margin of an input signal level in which distortion occurs at the compression level are associated with each other. Calculating the input signal level at which distortion of
The strain measuring method according to claim 1, wherein: テレビ放送信号を伝送する同軸ケーブルで接続された伝送路の歪を測定する歪測定装置であって、
ホワイトノイズを発生して前記伝送路に入力するホワイトノイズ発生手段と、
前記伝送路を伝送した前記ホワイトノイズの出力信号レベルを測定する測定手段と、
前記ホワイトノイズ発生手段が前記ホワイトノイズの入力信号レベルを変化させたときに、前記入力信号レベルの変化に対する前記出力信号レベルの変化が非線形で追従する場合に歪が発生したと判断する歪判定手段と、
を有することを特徴とする歪測定装置。 A distortion measuring device that measures distortion of a transmission line connected by a coaxial cable that transmits a television broadcast signal,
White noise generating means for generating white noise and inputting it into the transmission line;
Measuring means for measuring an output signal level of the white noise transmitted through the transmission line;
Distortion determining means for determining that distortion has occurred when the change in the output signal level with respect to the change in the input signal level follows non-linearly when the white noise generating means changes the input signal level of the white noise When,
A strain measuring apparatus comprising: 前記入力信号レベルに対する前記出力信号レベルを測定した測定結果それぞれについて、前記測定結果のうち前記入力信号レベルが低い前記測定結果を通る基準直線から前記測定結果それぞれについて前記出力信号レベルが圧縮されている圧縮度合いを求め、圧縮度合いとその圧縮度合いのときに歪が発生した入力信号レベルのマージンを示すバックオフを対応付けたバックオフテーブルを参照し、前記測定結果それぞれの圧縮度合いから前記バックオフを求めて前記伝送路の歪が発生した入力信号レベルを算出する入力判定手段を有することを特徴とする請求項３記載の歪測定装置。   For each measurement result obtained by measuring the output signal level relative to the input signal level, the output signal level is compressed for each measurement result from a reference line passing through the measurement result having the low input signal level among the measurement results. A compression level is obtained, and a back-off table in which a compression level and a back-off indicating a margin of an input signal level in which distortion occurs at the compression level is referred to, and the back-off is calculated based on the compression level of each measurement result. 4. The distortion measuring apparatus according to claim 3, further comprising an input determination unit that calculates and calculates an input signal level at which the distortion of the transmission path has occurred.
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