JP2762302B2 - C / N measurement circuit for magnetic disk - Google Patents
C / N measurement circuit for magnetic diskInfo
- Publication number
- JP2762302B2 JP2762302B2 JP1195199A JP19519989A JP2762302B2 JP 2762302 B2 JP2762302 B2 JP 2762302B2 JP 1195199 A JP1195199 A JP 1195199A JP 19519989 A JP19519989 A JP 19519989A JP 2762302 B2 JP2762302 B2 JP 2762302B2
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- level
- noise
- track
- filter
- Prior art date
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- Testing Electric Properties And Detecting Electric Faults (AREA)
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Description
【発明の詳細な説明】 ［産業上の利用分野］ この発明は、磁気ディスクのC/N測定回路に関するも
のである。The present invention relates to a magnetic disk C / N measurement circuit.
［従来の技術］ 情報処理装置の記録媒体として使用される磁気ディス
クにおいては、磁気媒体に起因する広い周波数範囲のノ
イズがあり、このノイズが記録データの読み出し信号に
混入してデータエラーの原因となる。このようなノイズ
は媒体の素材に起因するので、厳密には個々のディスク
ごとに異なるものであるが、便宜上ロットごとに磁気デ
ィスクを抜き取り、適当なトラックを選定してノイズが
測定検査される。2. Description of the Related Art A magnetic disk used as a recording medium of an information processing apparatus has noise in a wide frequency range caused by the magnetic medium, and this noise mixes with a read signal of recorded data to cause a data error. Become. Since such noise is caused by the material of the medium, it is strictly different for each disk. For convenience, the magnetic disk is extracted for each lot, and an appropriate track is selected and the noise is measured and inspected.
第３図は、磁気ディスクに存在するノイズの分布と従
来の測定方法を説明するもので、書き込み回路により被
検査磁気ディスクの任意の１トラックに対して適当な周
波数fc、例えば2.5MHzの正弦波のテスト信号ｃを書き込
み、これを読み出し回路により読み出す。読み出された
信号Sdにはテスト信号ｃとともに斜線で示す媒体ノイズ
ｎが含まれている。ノイズｎは周波数ｆが高くなるに従
って漸次低下するが、例えば5MHz以上のものはデータエ
ラーに影響がないものとされる。なお、読み出された信
号Sdには媒体ノイズｎのほかに読み出し回路に固有のノ
イズｎAが重畳されている。テスト信号のレベルＣとノ
イズ信号のレベルＮとの比であるC/Nを測定する従来の
測定方法は、スペクトルアナライザを使用して、信号Sd
に含まれているテスト信号ｃとノイズｎS＝（ｎ＋ｎA）
のレベルをそれぞれ定量分析し、また、読み出し回路自
体についてその固有のノイズｎAを測定分析して差し引
きし、演算によりc/n（またはC/N）求めるものである。FIG. 3 illustrates the distribution of noise present on the magnetic disk and the conventional measuring method. The write circuit uses a sine wave of an appropriate frequency fc, for example, 2.5 MHz, for any one track of the magnetic disk to be inspected. Is written and read out by the readout circuit. The read signal Sd includes the medium noise n indicated by oblique lines together with the test signal c. The noise n gradually decreases as the frequency f increases. For example, a noise of 5 MHz or more is assumed to have no influence on the data error. The read signal Sd is superimposed with noise nA inherent to the read circuit in addition to the medium noise n. A conventional measurement method for measuring C / N, which is a ratio between the level C of the test signal and the level N of the noise signal, uses a spectrum analyzer to measure the signal Sd.
Test signal c and noise nS = (n + nA)
Are quantitatively analyzed, and the inherent noise nA of the readout circuit itself is measured and analyzed and subtracted, and c / n (or C / N) is obtained by calculation.
［解決しようとする課題］ 上記のスペクトルアナライザによるC/Nの測定方法
は、ノイズの周波数分布が精密に測定されるもので、磁
気媒体の素材の厳密な試験には適切な方法であるが、検
査には数十秒の長時間を要し、生産現場において大量の
ディスクに対する検査方法としては適当ではない。な
お、生産現場における検査としては、ノイズの周波数分
布は必ずしも必要でなく、データエラーに影響する周波
数範囲のトータルのノイズレベルを測定すればこと足り
るものである。[Problem to be Solved] The C / N measurement method using the above spectrum analyzer is a method that accurately measures the frequency distribution of noise, and is an appropriate method for a strict test of a material of a magnetic medium. Inspection takes a long time of several tens of seconds, and is not suitable as a method for inspecting a large number of disks at a production site. In the inspection at the production site, the frequency distribution of noise is not always necessary, and it is sufficient to measure the total noise level in a frequency range that affects data errors.
この発明は以上に鑑みてなされたもので、テスト信号
ｃのレベルＣに対して影響する周波数範囲について、ト
ータルのノイズレベルＮのC/Nを迅速に測定する回路を
提供することを目的とするものである。The present invention has been made in view of the above, and has as its object to provide a circuit for quickly measuring the C / N of the total noise level N in a frequency range that affects the level C of the test signal c. Things.
［課題を解決するための手段］ このような目的を達成するこの発明のC/N測定回路の
特徴は、磁気ディスクのトラックからテスト信号を読み
出す読み出し回路と、この読み出し回路により読み出さ
れたテスト信号ｃとノイズとの合成信号Sdを適当な周波
数の変調信号により変調する変調部と、この変調部から
変調された合成信号Sdを含む変調波を受けてその側帯波
に含まれるテスト信号ｃを抽出して出力する単峰フィル
タと、変調部から変調波を受けてテスト信号ｃを除去し
た側波帯の信号を出力する、いわゆるバンド・リジェク
ト・フィルタであるノッチフィルタと、このノッチフィ
ルタより出力される信号を適当な帯域幅で抽出する帯域
フィルタと、この帯域フィルタの出力信号のレベルのト
ラック１周分の第１の積分値、テスト信号を読み出すこ
となく読み出し回路を動作させて得られる帯域フィルタ
の出力信号のレベルのトラック１周分の第２の積分値お
よび単峰フィルタの出力信号のレベルのトラック１周分
の第３の積分値をそれぞれ発生する積分器と、第１の積
分値を第１のノイズレベルＮSとし、第２の積分値を第
２のノイズレベルＮAとし、第３の積分値をテスト信号
のレベルＣとして積分器から得て第１のノイズレベルＮ
Sと第２のノイズレベルＮAとの差（ＮS−ＮA）をノイズ
信号のレベルＮとして求める算出回路とを備えていて、
レベルＣとレベルＮとの比を算出するものである。[Means for Solving the Problems] The C / N measurement circuit of the present invention that achieves the above object is characterized by a read circuit for reading a test signal from a track of a magnetic disk and a test read by the read circuit. A modulator for modulating a composite signal Sd of the signal c and the noise with a modulation signal of an appropriate frequency; receiving a modulation wave including the composite signal Sd modulated from the modulator to generate a test signal c included in a sideband thereof; A single-peak filter that extracts and outputs a signal, a notch filter that is a so-called band reject filter that receives a modulated wave from the modulator and outputs a signal in a sideband from which the test signal c is removed, A band filter for extracting a signal to be processed with an appropriate bandwidth, a first integrated value of a level of an output signal of the band filter for one round of a track, and a test signal. The second integral value for one round of the track of the output signal level of the bandpass filter obtained by operating the readout circuit without outputting the signal and the third integral value for one round of the track of the output signal level of the single peak filter are obtained. The integrators respectively generated, the first integrated value is a first noise level NS, the second integrated value is a second noise level NA, and the third integrated value is a test signal level C from the integrator. First noise level N
A calculating circuit for calculating a difference (NS-NA) between S and the second noise level NA as a noise signal level N,
The ratio of the level C to the level N is calculated.
［作用］ 以上の構成によるC/N測定回路においては、被検査磁
気ディスクの任意の１トラックに書き込まれた、一定周
波数の正弦波のテスト信号ｃとノイズの合成信号Sdが読
み出されて変調部により適当な周波数の変調信号により
変調される。変調された信号には、上下の２つの側帯波
があるので、その一方をとりこれに含まれているテスト
信号ｃを単峰フィルタにより抽出する。またその側帯波
よりノッチフィルタによりテスト信号ｃが除去されてノ
イズｎSが適当な帯域幅の帯域フィルタにより抽出され
る。ただし、このノイズｎSには、磁気ディスクの媒体
に起因するノイズｎのほかに読み出し回路に固有のノイ
ズｎAが含まれている。なお、このように信号Sdに変調
方法を適用する理由は、変調しない直接的な方法に比較
してテスト信号ｃとノイズｎSが安定に抽出でき、また
各フィルタの構成が容易であるからである。[Operation] In the C / N measurement circuit having the above configuration, a test signal c of a sine wave having a constant frequency and a composite signal Sd of noise written on an arbitrary track of the magnetic disk to be inspected are read and modulated. The signal is modulated by a modulation signal of an appropriate frequency by the unit. Since the modulated signal has two upper and lower sidebands, one of them is taken and the test signal c contained therein is extracted by a single peak filter. The test signal c is removed from the sideband wave by a notch filter, and noise nS is extracted by a bandpass filter having an appropriate bandwidth. However, the noise nS includes the noise nA inherent to the read circuit in addition to the noise n caused by the magnetic disk medium. The reason why the modulation method is applied to the signal Sd is that the test signal c and the noise nS can be extracted more stably and the configuration of each filter is easy compared to the direct method without modulation. .
以上により抽出されたテスト信号ｃ、ノイズｎS、お
よびノイズｎAはそれぞれ積分器により、１トラック間
について積分され、それぞれに対する積分値Ｃ、ＮS、
およびＮAがえられる。算出回路としてデータ処理部に
おいて、ＮS−ＮAを演算して磁気媒体のノイズｎに対す
る積分値Ｎを求め、これよりC/Nが演算される。以上に
おける１トラックの積分区間は、トラックの起点を示す
インデックス信号により制御されるものである。The test signal c, the noise nS, and the noise nA extracted as described above are respectively integrated for one track by an integrator, and the integrated values C, NS, and
And NA are obtained. In a data processing section as a calculation circuit, NS-NA is calculated to obtain an integral value N for noise n of the magnetic medium, and C / N is calculated from this. The integration section of one track described above is controlled by an index signal indicating the starting point of the track.
［実施例］ 第１図は、この発明による磁気ディスクのC/N測定回
路の実施例におけるブロック構成図を示し、第２図は第
１図に対するテスト信号とノイズの分離抽出に対する信
号波形の説明図である。[Embodiment] FIG. 1 is a block diagram showing an embodiment of a C / N measuring circuit for a magnetic disk according to the present invention. FIG. 2 is an illustration of a signal waveform for separation and extraction of a test signal and noise with respect to FIG. FIG.
第１図において、被検査の磁気ディスク１に対して、
磁気ヘッド1aが切り替えスイッチ２により書き込み回路
３に接続され、これより供給される一定周波数ｆC、例
えば2.5MHzの正弦波のテスト信号ｃが書き込みアンプ4a
を経て、適当な１トラックに書き込まれる。次に、スイ
ッチ２の切り替えにより磁気ヘッド1aが測定回路に接続
され、テスト信号ｃとノイズｎSの合成信号Sdが読み出
しアンプ4bを経て低域フィルタ５に入力して無害な高周
波数成分がカットされる。低域フィルタ５の出力信号を
第２図の（Ａ）で示す。この出力信号（Ａ）は変調部６
において適当な周波数fm、例えば12.5MHzの変調信号に
より変調されて、第２図の（Ｂ）の変調波が作られる。
なお、変調部６は変調器（MOD）6aと発振器（OSC）6bと
により構成され、変調器6aとしてバランス型のものを使
用すると、変調波（Ｂ）は変調信号fmを伴なわない上下
の側帯波よりなる。例えば下部側帯波においては、テス
ト信号ｃの周波数f0は10.0MHzであり、これをノッチフ
ィルタ7aにより除去して信号（Ｃ）とし、周波数f0を中
心とする帯域幅ＢW、例えば5.0MHzの帯域フィルタ８に
よりノイズｎSが抽出され、これを（D1）で示す。ま
た、読み出し回路に固有のノイズｎAについては、テス
ト信号ｃの読み出しを停止し、上記と同一方法で測定し
て信号（D2）がえられる。次に、同一トラックについて
単峰フィルタ7bによりテスト信号ｃが抽出されて、信号
（Ｅ）がえられ、これらのノイズｎS、ｎAおよびテスト
信号ｃは切り替えスイッチ９により切り替えられ、それ
ぞれアンプ10を経て整流器11により整流され、積分器12
aに入力して１トラック間について積分されてそれぞれ
に対する積分値ＮS,NA、Ｃがえられる。ここで、１トラ
ック間の積分は、磁気ディスク１に設けられたトラック
の起点を示すインデックス信号INDを検出器12bにより検
出し、これを積分器12aに与えて積分区間を制御するも
のである。In FIG. 1, with respect to the magnetic disk 1 to be inspected,
The magnetic head 1a is connected to the write circuit 3 by the changeover switch 2, and a test signal c of a constant frequency fc, for example, a sine wave of 2.5 MHz supplied thereto is supplied to the write amplifier 4a.
Is written to an appropriate track. Next, by switching the switch 2, the magnetic head 1a is connected to the measuring circuit, and the combined signal Sd of the test signal c and the noise nS is input to the low-pass filter 5 via the readout amplifier 4b, and harmless high-frequency components are cut. You. The output signal of the low-pass filter 5 is shown in FIG. This output signal (A)
Is modulated by a modulation signal having an appropriate frequency fm, for example, 12.5 MHz to produce a modulated wave shown in FIG. 2B.
The modulator 6 is composed of a modulator (MOD) 6a and an oscillator (OSC) 6b. When a balanced type modulator is used as the modulator 6a, the modulated wave (B) is shifted up and down without the modulation signal fm. Consists of sideband waves. For example, in the lower sideband, the frequency f 0 of the test signal c is 10.0 MHz, which is removed by the notch filter 7a and the signal (C), the bandwidth BW centered at frequency f 0, for example, 5.0MHz of noise nS is extracted by the band filter 8 and is shown in (D 1). Also, the specific noise nA to the readout circuit, stops reading of the test signal c, the signal (D 2) will be obtained by measuring by the above same method. Next, a test signal c is extracted from the same track by the single-peak filter 7b, and a signal (E) is obtained. These noises nS and nA and the test signal c are switched by the changeover switch 9, and each of them passes through the amplifier 10. Rectified by rectifier 11 and integrated by integrator 12
The values are integrated into one track, and integrated values NS, NA, and C for each track are obtained. Here, the integration between one track is such that the detector 12b detects an index signal IND indicating the starting point of the track provided on the magnetic disk 1, and supplies this to the integrator 12a to control the integration section.
以上によりえられた各積分値はA/D変換器13によりデ
ジタル化されてデータ処理部14に入力し、積分値ＮSと
ＮAの差分（ＮS−ＮA）より磁気媒体のノイズＮが求め
られ、C/N比が演算されて出力部15に出力される。Each of the integrated values obtained as described above is digitized by the A / D converter 13 and input to the data processing unit 14. The noise N of the magnetic medium is obtained from the difference (NS-NA) between the integrated values NS and NA. The C / N ratio is calculated and output to the output unit 15.
［発明の効果］ 以上の説明により明らかなように、この発明による磁
気ディスクのC/N測定回路においては、被検査の磁気デ
ィスクの任意の１トラックに書き込まれたテスト信号ｃ
は、磁気媒体のノイズｎと読み出し回路に固有のノイズ
ｎAとよりなるノイズｎSと合成されて信号Sdが読み出さ
れ、テスト信号ｃと各ノイズがフィルタにより分離抽出
されて積分器に入力し、それぞれに対する積分値Ｃ、Ｎ
Sがえられる。また、ノイズｎAに対しては、テスト信号
ｃの読み出しを停止した状態で測定されて上記と同様に
積分値ＮAが求められ、データ処理部において各積分値
よりC/Nが演算されるもので、測定は同一のトラックに
対して２回と、読み出し回路に対する１回の都合３回で
終了し、従来のスペクトルアナライザによる測定方法に
比較して、測定時間が著しく短縮されるもので、生産現
場において大量の磁気ディスクに対して効率の高いC/N
測定ができる効果には大きいものがある。[Effects of the Invention] As is clear from the above description, in the C / N measurement circuit for a magnetic disk according to the present invention, the test signal c written on any one track of the magnetic disk to be inspected.
The signal Sd is read out by combining the noise nS consisting of the noise n of the magnetic medium and the noise nA unique to the readout circuit, and the test signal c and each noise are separated and extracted by the filter and input to the integrator, Integral value C, N for each
S is obtained. The noise nA is measured in a state where the reading of the test signal c is stopped, the integrated value NA is obtained in the same manner as described above, and C / N is calculated from each integrated value in the data processing unit. , Measurement is completed twice in the same track and once in the readout circuit, which is three times, and the measurement time is remarkably reduced as compared with the conventional measurement method using a spectrum analyzer. Efficient C / N for large number of magnetic disks
There are significant effects that can be measured.
第１図は、この発明による磁気ディスクのC/N測定回路
の実施例におけるブロック構成図、第２図は第１図の各
部に対する信号波形図、第３図は、磁気ディスクのノイ
ズと従来のC/N測定方法の説明図である。 １…磁気ディスク、1a…磁気ヘッド、2,9…切り替えス
イッチ、３…書き込み回路、4a,4b,10…アンプ、５…低
域フィルタ、６…変調部、6a…変調器、6b…発振器、7a
…ノッチフィルタ、7b…単峰フィルタ、８…帯域フィル
タ、11…整流器、12a…積分器、12b…インデックス検出
器、13…A/D変換器、14…データ処理部、15…出力部。FIG. 1 is a block diagram of an embodiment of a C / N measuring circuit for a magnetic disk according to the present invention, FIG. 2 is a signal waveform diagram for each part in FIG. 1, and FIG. FIG. 4 is an explanatory diagram of a C / N measurement method. DESCRIPTION OF SYMBOLS 1 ... Magnetic disk, 1a ... Magnetic head, 2, 9 ... Changeover switch, 3 ... Writing circuit, 4a, 4b, 10 ... Amplifier, 5 ... Low-pass filter, 6 ... Modulating part, 6a ... Modulator, 6b ... Oscillator, 7a
... Notch filter, 7b ... single peak filter, 8 ... bandpass filter, 11 ... rectifier, 12a ... integrator, 12b ... index detector, 13 ... A / D converter, 14 ... data processing unit, 15 ... output unit.
Claims (1)
に対して書き込まれた一定周波数のテスト信号を読み出
して行う、該テスト信号のレベルＣとノイズ信号のレベ
ルＮの比C/Nを測定する測定回路において、 前記トラックから前記テスト信号を読み出す読み出し回
路と、この読み出し回路により読み出されたテスト信号
ｃとノイズとの合成信号Sdを適当な周波数の変調信号に
より変調する変調部と、この変調部から変調された該合
成信号Sdを含む変調波を受けてその側帯波に含まれる前
記テスト信号ｃを抽出して出力する単峰フィルタと、前
記変調部から前記変調波を受けて前記テスト信号ｃを除
去した側波帯の信号を出力するノッチフィルタと、この
ノッチフィルタより出力される信号を適当な帯域幅で抽
出する帯域フィルタと、前記帯域フィルタの出力信号の
レベルの前記トラック１周分の第１の積分値、前記テス
ト信号を読み出すことなく前記読み出し回路を動作させ
て得られる前記帯域フィルタの出力信号のレベルの前記
トラック１周分の第２の積分値および前記単峰フィルタ
の出力信号のレベルの前記トラック１周分の第３の積分
値をそれぞれ発生する積分器と、前記第１の積分値を第
１のノイズレベルＮSとし、前記第２の積分値を第２の
ノイズレベルＮAとし、前記第３の積分値を前記テスト
信号の前記レベルＣとして前記積分器から得て前記第１
のノイズレベルＮSと前記第２のノイズレベルＮAとの差
（ＮS−ＮA）を前記ノイズ信号の前記レベルＮとして求
める算出回路とを備え、前記レベルＣと前記レベルＮと
の比を算出する磁気ディスクのC/N測定回路。1. A ratio C / N of a level C of a test signal and a level N of a noise signal, which is read and read out from a test signal of a constant frequency written on an arbitrary track of a magnetic disk to be inspected. A reading circuit for reading the test signal from the track; a modulation unit for modulating a composite signal Sd of the test signal c and noise read by the reading circuit with a modulation signal of an appropriate frequency; A unimodal filter that receives a modulated wave including the synthesized signal Sd modulated from a modulator, extracts and outputs the test signal c included in a sideband of the modulated wave, and receives the modulated wave from the modulator to perform the test. A notch filter for outputting a signal in a sideband from which the signal c has been removed, a band filter for extracting a signal output from the notch filter with an appropriate bandwidth, A first integrated value of the level of the output signal of the filter for one round of the track, and the level of the output signal of the bandpass filter obtained by operating the read circuit without reading the test signal for one round of the track; An integrator for generating a second integral value and a third integral value for one round of the track of the level of the output signal of the single-peak filter, and the first integral value as a first noise level NS; The second integrated value is obtained from the integrator as the second noise level NA, and the third integrated value is obtained as the level C of the test signal from the integrator.
And a calculating circuit for calculating a difference (NS-NA) between the noise level NS and the second noise level NA as the level N of the noise signal, and calculating a ratio between the level C and the level N. Disk C / N measurement circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1195199A JP2762302B2 (en) | 1989-07-27 | 1989-07-27 | C / N measurement circuit for magnetic disk |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1195199A JP2762302B2 (en) | 1989-07-27 | 1989-07-27 | C / N measurement circuit for magnetic disk |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0357975A JPH0357975A (en) | 1991-03-13 |
| JP2762302B2 true JP2762302B2 (en) | 1998-06-04 |
Family
ID=16337103
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1195199A Expired - Lifetime JP2762302B2 (en) | 1989-07-27 | 1989-07-27 | C / N measurement circuit for magnetic disk |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2762302B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8525509B2 (en) | 2007-12-04 | 2013-09-03 | Headway Technologies, Inc. | Low cost simplified spectrum analyzer for magnetic head/media tester |
-
1989
- 1989-07-27 JP JP1195199A patent/JP2762302B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0357975A (en) | 1991-03-13 |
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