JP2001202601A - Recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the rise time of a recording current and to shorten current settling time after overshoot for the purpose of supplying a current waveform, with which a current is inverted at right timing, for magnetic recording. SOLUTION: The rise characteristics of the recording current and shortening of the current settling time are attained by using reflected currents generated between a recording head 29 and a transmission line 21 and between a writer 26 and the transmission line 21. Concretely, the rise time is shortened by forming overshoot from the first reflected current on the side of the recording head 29. When the reflected current returns to the side of the writer 26, the polarity of the reflected current is inverted by inverting the current with the negative code of a current reflection coefficient. When the reflected current reaches the side of the recording head 29 again, the second reflection occurs and by decreasing a current value with this reflection, the current settling time is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus, and particularly to a recording system from a recording / reproducing R / W-IC for high-frequency recording to a recording / reproducing head via a transmission line. The present invention relates to a magnetic recording / reproducing device.

[0002]

2. Description of the Related Art In a magnetic disk drive, in order to record a large amount of data in a limited space and record / reproduce a large amount of data in a short time, a high recording density technology and a high speed data transfer technology, that is, recording / reproducing. It is essential to increase the frequency.

In order to promote the technology for increasing the recording density, the positioning accuracy has been improved by improving the recording / reproducing head, the servo technology, and the head suspension.

In order to promote high-speed data transfer technology, improvements have been made to electronic components typified by channel LSIs and R / W-ICs, and to transmission line characteristics for transmitting recording / reproducing signals arranged in a suspension section. Have been done.

A system from the R / W-IC to the magnetic head via the transmission line, which is the object of the present invention, has been developed by the following method. The following is a known technique.

(1) A low output impedance circuit system has been proposed for a recording head driver (hereinafter referred to as a writer) of an R / W-IC. For example, "A 500MHz Write Am
plifier for Hard Disk Drives with Low Output Imped
ance ", ESSCIRC (European Solid State Circuits Conf
erence) Proceeding, pp.62-64, 1999.

(2) The transmission line is constituted by one non-connected line without connecting a plurality of lines in the middle. For example, there is a long tail type TSA developed by Hutchinson.

(3) In the recording head, measures are taken to reduce the inductance while maintaining the state in which magnetic recording can be performed.

A recording system for high-speed transfer / high-frequency recording has been developed by the above combination.

[0010]

As the recording frequency increases, a phenomenon occurs in which the inversion timing of the current waveform shifts due to interference between the recording current waveform after the overshoot and the rising waveform of the next bit. In the magnetic head, a recording magnetic field corresponding to the current waveform is generated and recorded on the medium. At this time, if the reversal timing of the current waveform shifts, the position for recording the magnetization reversal also shifts. The position shift of the magnetization reversal is one of the causes of the error rate deterioration.

An object of the present invention is to perform high-speed transfer / high-frequency recording by keeping the reversal timing of the current waveform from shifting.

To prevent the reversal timing from being shifted specifically, the followings are possible: (1) shorten the rise time of the recording current, and (2) shorten the current settling time after the recording current overshoot. The goal is to minimize interference.

[0013]

Since the recording head includes a coil, the impedance has a frequency dependence.
Therefore, a current reflection for the recording current occurs in principle due to the impedance mismatch between the transmission line and the recording head. The magnitude and waveform of the reflected current are related to the degree of impedance mismatch. Therefore, the impedance mismatch condition, specifically, the characteristic impedance of the transmission line
(Zo), line length (Length or l), recording head resistance (Rh)
・ Head impedance composed of inductance (Lh)
By appropriately selecting the relationship between (Zh) and the output impedance (Zout) of the writer, it is possible to obtain a recording current waveform with a fast rise and a short current settling time.

First, in the head section, current reflection occurs due to the ratio of the characteristic impedance of the transmission line to the impedance of the head. In this case, a reflected current having the same polarity as the rising of the current is generated, so that the rising portion is equivalently earlier.

Next, the current reflected on the head side returns to the writer side, and causes the current reflection on the writer side again. In this case, by setting the output impedance of the writer to be higher than the characteristic impedance of the transmission line, the reflected current on the writer side is reflected as a waveform having a polarity opposite to that of the incident current to the writer.

When the reflected current reaches the head side, it is subtracted from the current because it has a polarity opposite to that of the current already incident on the recording head. Therefore, in the rising portion of the recording current, an overshoot is generated by the first reflection on the head side, the rising time is shortened, and the current setting is shortened by the second reflection.

Further, the reflected current from the third time onward becomes a multiple reflection, so that the amplitude can be reduced by adjusting the current reversal coefficient on the writer side. Thereby, the influence can be almost eliminated.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The general structure of a magnetic disk drive will be described with reference to FIGS. 2 and 3, and subsequently, from the R / W-IC to which the present invention is applied to a recording head via a transmission line. The mounting part of the recording system will be described.

A magnetic disk drive, which is an example of a recording / reproducing apparatus, includes a head disk assembly (HDA) 10 and a recording / reproducing control circuit 11.

The HDA 10 includes a spindle unit 12 on which a magnetic recording medium 13 for recording data is stacked, data to be recorded on the magnetic recording medium 13, and
3 comprises a carriage unit 15 on which a magnetic head 14 for reading data from is mounted.

The carriage unit 15 includes a voice coil motor (VCM) 17 for seeking and positioning the magnetic head 14 on the magnetic recording medium 13, an arm 18,
A suspension 19 attached to the tip of the arm 18,
Magnetic head 14 attached to the tip of suspension 19
And a flexible patterned cable (FPC) 16 for transmitting a recording / reproducing signal, and an R mounted on the FPC 16
/ W-IC 20, R / W-IC 20, and magnetic head 14
It comprises a transmission line 21 for transmitting a recording / reproducing signal between them.

A recording / reproduction control circuit 11 is provided between the HDA 10 and an external device. The recording / reproduction control circuit 11 includes a signal processing LSI 22 and a hard disk drive control (HDD).
Dcontrol) 23 is mounted. The connector 25-1 on the HDA side and the connector 25- on the recording / reproduction control circuit 11 side
2, the R / W-IC 20 and the signal processing LSI 22 are connected. It is connected to an external device via an external interface 24 of the recording / reproduction control circuit 11.

Next, the suspension 19 installed at the tip of the arm 18 will be described with reference to FIG. The transmission line 21 extends along the side or upper and lower surfaces of the arm 18.
The magnetic head 14 is connected to the end of the transmission line 21.

FIG. 1 shows the configuration of FIG. 3 in which only the recording system is taken out and rewritten as a simplified configuration model to meet the following description. The writer 26 of the R / W-IC 20 includes a driver section 27 and an output impedance setting circuit (impedance: Zout) 28.
The transmission line 21 is connected to the R / W-IC 20.
The characteristic values of the transmission line are characteristic impedance (Zo), line length (Length or l (lowercase L, represented in cursive in the formula)), and transmission delay time (τd). The recording head is connected to the transmission line 21. If there is a connection point in the middle of the line, the transmission line is divided before and after the connection point. In this case, the connection point generally becomes capacitive and thus has a low impedance, and when viewed from the transmission line, a discontinuous point of impedance is sandwiched.
It appears as a configuration with a set of transmission lines. In this system, based on the configuration described below, the position of current reflection only increases in the middle of the transmission line, and it can be easily analogized by analysis.

The present invention is directed to a configuration in which an R / W-IC is connected to a recording head via a transmission line. Accordingly, FIG. 3 shows that the R / W-IC2
Although the configuration in which the R / W-IC is mounted is shown in the above description, the mounting position of the R / W-IC may be anywhere. For example, an R / W-IC may be mounted on the arm 18 or the suspension 19.

Next, the definition of terms / symbols used in the present invention and a partial evaluation method will be described with reference to FIG.

(1) Rise time of recording current (tr)
And the definition of fall time (tf) tr is called rise time, and Iwpp is changed from -Iwset to Iwset
This is the time required for the current to change from 10% to 90%, assuming that the amplitude is 0 to 100%. Iwset is a set (DC) current value, and Iwpp / 2 = Iwset. Further, tf is a fall time, which is a time required for a current change from 90% to 10%.

Since the writer is a symmetrical circuit and is transmitted as a differential signal current, tr = tf generally holds.

(2) Definition of recording current settling time (ts) ts is called a recording current settling time, and after current inversion starts for an isolated current inversion waveform, -5% Iw ≦ Iw (t) ≦
It represents the time until it falls within the range of + 10% Iw. Where Iw
(t) indicates the instantaneous value of the recording current.

(3) Definition of Overshoot (OS) The OS is called overshoot and is a scale indicating the magnitude of the maximum amplitude current with respect to the amplitude of the set current value. OS is
For the isolated current inversion waveform, the magnitude (Ios) of the maximum amplitude current exceeding Iwset after current inversion is defined as a percentage value divided by Iwpp.

(4) Recordable limit frequency (fw_li)
m) Definition fw_lim is called a recordable limit frequency, and tr, t
It is determined by the relationship between s and the bit time interval. That is, when interference starts between the current inversions before and after, a current inversion timing shift occurs due to waveform interference. A frequency at which the timing shift exceeds a certain set time with respect to the bit time interval is defined as a recordable limit frequency. In this embodiment, ± 5% of the bit time interval is set as the limit time of the timing shift.

FIG. 5 shows the results of actual measurement and evaluation in accordance with the above definition.
Shown in FIG. 5 shows the recording current rise time (tr), the settling time (ts), and the recordable limit frequency (fw_li).
m). To advance to high-frequency recording, the recordable limit frequency must be increased.
It can be seen from the figure that tr and ts must be shortened for this purpose.

An embodiment for shortening tr and ts will be described below.

The method comprises the steps of: writing the output impedance of the writer;
This method uses a reflected current generated by intentionally shifting the characteristic impedance of the transmission line and the impedance of the recording head.

First, an equivalent circuit of the recording head will be outlined.

For high-frequency recording, an equivalent circuit of the impedance (Zh) of the recording head can be represented as a series connection system of a resistance (Rh) and an inductance (Lh).

Next, the current reflection coefficient when the recording head is viewed from the transmission line is represented by Δh, and is defined by Expression (1).

[0038]

(Equation 1)

Here, when Equation (1) is solved by setting Zh = Rh + jωLh,

[0040]

(Equation 2)

Is obtained. From equation (2), the reflection current from the recording head is Δh = 0 only when Lh = 0 and Rh = Zo.
(Non-reflection). Therefore, in the recording head, since a coil exists in principle (Lh ≠ 0), a reflected current always occurs.

Now, the reflected current from the recording head when the step current flows from the transmission line toward the recording head can be expressed by the following equation (3).

[0043]

(Equation 3)

From equation (3), the reflected current is represented by the time constant Lh
It can be seen that an exponential function waveform of / (Zo + Rh) is obtained. The polarity of the reflected current can be represented by the sign of the coefficient Γhr;

[0045]

(Equation 4)

When Δhr> 0, a reflected current having the same polarity as the input current polarity is generated, and when Δhr <0, a reflected current having a polarity opposite to the input current polarity is generated.

Next, the output impedance of the writer is set to Zo.
ut. The current reflection coefficient when the writer is viewed from the transmission line is represented by Δic, and is defined by Expression (5).

[0048]

(Equation 5)

From equation (5), if Zout is equal to Zo, then Γic = 0, and there is no reflection. Zout is Zo
If it is smaller, Γic> 0, and a current having the same polarity as the current flowing from the transmission line to the writer is reflected. On the other hand, when Zout becomes larger than Zo, Γi
c <0, and the current having the opposite polarity to the current flowing from the transmission line to the writer is reflected.

Next, the relationship between the transmission delay time .tau.d of the transmission line and the transmission line length l can be expressed by equation (5).

[0051]

(Equation 6)

Most of the insulator used for the transmission line of the FPC is polyimide. For polyimide, ε
s (relative permittivity) = about 3.4, and μs (relative magnetic permeability)
= 1.0, a transmission delay time of τd = 0.31 ns (nanosecond) occurs when the line length is 50 mm (millimeter).

Next, the ratio of the time constant to the transmission delay time τd in the number of reflected current waveforms (Equation 3) on the recording head side is defined by Expression (7), and is referred to as the time constant of the head reflected current to the transmission delay time. .

[0054]

(Equation 7)

Simulation evaluation was performed based on the above-described relational expressions. The reference condition is Zo = 100Ω, l
= 30mm, Rh = 10Ω, Lh = 14nH, Zout
= 200Ω.

FIG. 6 shows an example of a simulation waveform under the reference condition. FIG. 6 is a waveform obtained by extracting two inversions in the equally-spaced continuous inversion pattern. (A) shows the input current waveform to the line, (b) shows the current waveform including the reflected current at the writer output, and (c) shows the current waveform including the reflected current at the recording head end. Was. When a reflected current under a certain condition is used, overshoot can be added. By adding overshoot, c
As shown, the rising of the recording current (head current) is a
It becomes earlier than the rise of the input current in the figure. Further, the current setting after the overshoot can be made faster.
In order to explain the state of the reflected current used here, the operation will be described using a case where a pulse current is virtually input.

FIG. 7 shows that Δic = −0.33, Δhr =
0.82, time constant of head reflection current with respect to transmission delay time (Lh / (Zo + Rh)) * (1 / τd) = 0.13
The operation waveforms in are shown.

First, when the pulse waveform 50 is input, it immediately appears in the writer output. The pulse waveform 51 is transmitted through the transmission line and reaches the head end. Since the pseudo current reflection coefficient Δhr> 0 on the head side, a reflection current of the same polarity is generated at the head end with respect to the pulse current waveform that has arrived, and the waveform shape follows the characteristic of the current reflection coefficient Δh. Waveform 52 is
Since it is a composite waveform of the pulse waveform and the reflection waveform that have reached the head end, and the reflection current waveform has the same polarity as the input current waveform,
This will increase the amplitude. In this waveform, the reflected current waveform portion 53 sends the line backward and returns to the writer. Since the current reflection coefficient Γic <0 on the writer side, a reflection current having a polarity opposite to that of the reflection current 53 returned to the writer is generated according to the characteristics of Γic. The waveform 54 is a composite waveform of the current waveform 53 returned to the writer and the reflection waveform. Here, the reflected waveform is a waveform subtracted from the current waveform 53 because it is a reverse polarity waveform.

The waveform 55 reflected on the writer side reaches the head end again through the transmission line. At the head end, waveform 5
5 is a waveform of the opposite polarity to the initial input pulse waveform. At the head end, since Δhr> 0, a reflected current waveform having the same polarity as the input waveform is generated. Therefore, since the waveform 55 of the opposite polarity is input, the reflected current waveform also has the opposite polarity (the same polarity as the waveform 55). The waveform 56 at the head end at this time is a waveform obtained by combining the waveform 55 and the reflected current waveform.

Again, the emission current waveform 57 on the head side is transmitted backward through the transmission line and reaches the writer side. On the writer side, Γic
Since <0, the polarity of the reflected current is inverted. The combination of the current waveform 57 and the reflected current is observed as a waveform 58. Thereafter, the above operation causes multiple reflections. However, since the reflection coefficient is a value of 1 or less, the multiple reflection always converges and disappears.

As described above, when the reflected current is used, the first reflection on the head side works in the direction of increasing the current amplitude, and the second reflection works in the direction of decreasing the current amplitude. Therefore, when the current waveform shown in FIG. 6A is input, the current amplitude increases on the head side due to the effect of the first reflection, and as a result of increasing the overshoot amount, tr becomes faster. Further, the current amplitude is reduced by the effect of the second reflection, and the current settling time ts is reduced.

In summary, since the reflection current is used, the reflection coefficient Γic on the writer side must not be zero, and the current reflection coefficient Γh on the recording head side must not be zero. Then, the first reflected current waveform on the recording head side is generated on the same polarity side as the rise of the recording current waveform, the first reflected current returns to the writer side, and a reflected current of the opposite polarity is generated on the writer side, and again. The tr and ts can be shortened by the fact that the second reflected current waveform generated when reaching the recording head side has the opposite polarity to the polarity of the recording current waveform.

This embodiment aims at shortening the rise time (tr) of the recording current waveform and shortening the current settling time (ts) by using the reflected current up to the second time at the head end. I have. Therefore, it is necessary to substantially eliminate the influence of the reflected current after the third time. Therefore, the relationship was examined with Δic as the horizontal axis and the ratio of the third reflected current amplitude to the first reflected current amplitude as the vertical axis. Here, when examining the reflected current amplitude, Lh = 0
Asked. The reason is that Lh is, as shown in Equation (3),
Since this affects the time constant of the reflected current but does not affect the amplitude, this is a measure for correctly observing the current amplitude. Therefore, it does not affect the result. This result is shown in FIG.
Shown in

The current amplitude caused by the third reflection at the head end causes waveform distortion. Therefore, the current amplitude caused by the third reflection is set to 10% or less. Since the third reflected current distorts the recording current waveform, it can be changed in the design of the recording system. Now, to suppress the current amplitude to 10% or less,
ic ≧ (−0.38). When this Γic is obtained as a ratio of the writer output impedance to the characteristic impedance of the transmission line, it becomes 2.23 times.

Next, the amplitude of the reflected current on the head side is determined by the characteristic impedance of the line and the resistance value of the head. Therefore, a pseudo current reflection coefficient Δhr can be used instead of the current reflection coefficient Δh on the head side. Again, since the reflected current is used, Γic and Γhr
Both must not be 0. And Γic and Γhr
Sign determines the polarity of the reflected waveform with respect to the input waveform.
In this embodiment, since the above-described reflected waveform is used, Δi
c and Δhr need to be different signs.

As a means for realizing the signs of Γic and 異 hr with different signs and making tr and ts faster, the following relationship may be established between the characteristic impedance of the transmission line, the output impedance of the writer, and the resistance value of the recording head. . From the characteristic impedance (Zo) of the transmission line, the resistance (R
h) (Zo> Rh) and make the output impedance (Zout) of the writer larger (Zo <Zout) than the characteristic impedance (Zo) of the transmission line.

In the following, the dependence of tr, ts and overshoot (OS) on the output impedance of the writer (FIG. 9) and the dependence on the characteristic impedance of the line (FIG. 10) were obtained by simulation.

The horizontal axis of FIG. 9 is the output impedance (Zout) of the writer. The vertical axis shows tr and ts when the current reflection coefficient (Γic) on the writer side and the inductance Lh of the recording head are used as parameters.

As shown in FIG. 9, as the output impedance (Zout) of the writer increases, the current reflection coefficient Γic on the writer side decreases. At the same time, tr becomes faster and ts
Slows down. In the relationship between tr and Γic, the smaller Γic, the faster tr becomes. Especially at Lh = 14nH,
In (Γic ≦ (−0.1)), tr is stable and fast,
In (Γic> (− 0.1)), the change of tr is large. Also, as the inductance Lh of the recording head becomes smaller,
Both tr and ts are faster.

As for the overshoot, as the inductance Lh of the head decreases, the overshoot increases and the output impedance (Zou) of the writer increases.
Overshoot increases as t) increases.

From the limitation of the waveform distortion due to the third reflected waveform amplitude, Δic ≧ (−0.38) must be satisfied. Further, as described above, since it is necessary to stably and quickly set tr, it is necessary to set Δic ≦ (−0.1). When this relationship is converted into the ratio of the output impedance (Zout) of the writer to the characteristic impedance (Zo) of the transmission line, the relationship becomes 1.2 ≦ (Zout / Zo) ≦ 2.23.

FIG. 10 shows the dependence of tr, ts and overshoot on the characteristic impedance of the line. Here, the case where Zout = 2 * Zo is fixed is shown as an example. As can be seen from the drawing, when the characteristic impedance of the line is increased, tr and ts become faster, and the overshoot increases. This result is satisfied in the range of Zout> Zo, and can be estimated from the result of FIG.

Next, in order to obtain the effect of the present invention, the basic configuration of the writer output impedance setting circuit 28 will be described with reference to FIG.
This will be described with reference to FIG.

In order to obtain the effect of the present invention, 1.2 ≦
It has been described above that (Zout / Zo) ≦ 2.23. The meaning of this equation indicates that even if the output impedance of the driver 27 changes, the ratio between the output impedance of the writer and the characteristic impedance of the transmission line must always satisfy this relationship. Therefore, a basic configuration for satisfying this relationship is shown in FIG.

The configuration is such that a connection terminal 73-
Resistances R1 (70) and R3 (7) between connection terminals 74-1 and 74-2 and transmission line connection terminals 74-1 and 74-2.
2), R1 (70) and transmission line connection terminal 74-1
, A resistor R2 (71) is provided between the line and the transmission line connection terminal 74-2 between the line R3 (72) and the transmission line connection terminal 74-2. This configuration shows the basic configuration,
This also includes one including this configuration or one configured with elements or circuits having functions equivalent to R1, R2, and R3.

The operation of the output impedance setting circuit 28 will be described using an example.

Example 1: When the output impedance of the driver 27 increases (for example, approaches infinity), the resistors R1 (70) and R3 (72) are ignored by the output impedance of the driver and R2 (71). Are seen from the transmission line 21 side as the output impedance (Zout) of the writer.

Example 2: When the output impedance 27 of the driver 27 approaches a small value (for example, zero), R1
(70) and the series resistance of R3 (72) R1 + R3 and R
Parallel resistance with 2 (72)

[0079]

(Equation 8)

Is the output impedance of the writer (Zou
t).

[0081]

According to the present invention, it is understood that there is a close relationship between tr, ts, overshoot, the reflection coefficient on the writer side, and the line length, which are necessary conditions for performing high-frequency recording. From each relationship, a recording system suitable for high-frequency recording can be obtained.

[Brief description of the drawings]

FIG. 1 is a simplified configuration model of a recording system in a magnetic recording apparatus.

FIG. 2 is a schematic diagram of a magnetic disk drive.

FIG. 3 is an enlarged view of an end of an arm on which an R / W IC is mounted.

FIG. 4 is a diagram showing a definition of a recording current waveform characteristic value.

FIG. 5: Recording current rise time (tr) and settling time (t)
FIG. 6 is a diagram showing a relationship between s) and a recording limit frequency.

FIG. 6 is a diagram showing a simulation result of a recording current waveform of each part.

FIG. 7 is a simulation result diagram showing characteristics of the polarity and waveform shape of the reflected current at the input end of the recording head using the pulse current input.

FIG. 8 is a graph showing the relationship between the first reflected current at the head end and the third reflected current.
Amplitude ratio of reflected current and writer-side current reflection coefficient Γic
FIG.

FIG. 9 shows recording current rise time (tr), settling time (ts),
FIG. 9 is a diagram illustrating the dependence of overshoot on the writer output impedance.

FIG. 10: Recording current rise time (tr), settling time (t)
s) illustrates the characteristic impedance dependence of overshoot.

FIG. 11 is a basic configuration diagram of an output impedance setting circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Head disk assembly (HDA), 11 ... Recording / reproduction control circuit, 12 ... Spindle part, 13 ... Magnetic recording medium, 14 ... Magnetic head, 15 ... Carriage part, 16 ...
Flexible Patterned Cable (FPC), 17
... Voice coil motor (VCM), 18 ... Arm, 19
... Suspension, 20 ... R / W-IC, 21 ... Relay line, 22 ... Signal processing LSI, 23 ... Hard disk drive control (HDDcontrol), 24 ... External interface, 25-1 ... Connector, 25-2 ... Connector, 26 ...
Writer, 27 ... Driver, 28 ... Output impedance setting circuit, 29 ... Recording head, 50 ... Pulse waveform, 51 ...
Pulse waveform, 52 ... combined waveform of pulse waveform and reflection waveform,
53: reflected current waveform, 54: composite waveform of the reflected current waveform 53 and the reflected waveform on the writer side, 55: reflected current waveform, 56
... A combined waveform of the reflected current waveform 55 and the reflected waveform on the head side, 57... A combined waveform of the reflected current waveform 57 and the reflected waveform on the writer side, 70.
... resistance R2, 72 ... resistance R3, 73-1 ... connection point with driver, 73-2 ... connection point with driver, 74-1 ... connection point with transmission line, 74-2 ... connection point with transmission line

Claims (8)

[Claims] 1. A writer comprising a driver for outputting a recording current and an output impedance setting circuit, a transmission line connected to an output of the writer, and a recording head for connecting a recording head to a side of the transmission line opposite to the writer. A recording apparatus comprising a recording system, wherein when a reflection current for the recording current in the recording head returns to the writer, a reflection current of an opposite polarity is generated in the writer. 2. The current reflection coefficient (Γic) when the writer is viewed from the transmission line is (−0.1) ≧ Γic ≧
2. The recording apparatus according to claim 1, wherein (-0.38). 3. The characteristic impedance (Z) of the transmission line.
o) to the output impedance of the writer (Zou
2. The recording apparatus according to claim 1, wherein the ratio of t) satisfies 1.2 ≦ (Zout / Zo) ≦ 2.23. 4. A recording device having a writer comprising a driver for outputting a recording current and an output impedance setting circuit, a transmission line connected to the output of the writer, and a recording system for connecting a recording head to the opposite side of the transmission line. An apparatus, wherein a current reflection coefficient (Γic) when viewing the writer from the transmission line is different from a pseudo current reflection coefficient (Γhr) when viewing the recording head from the transmission line. A recording apparatus in which the characteristic impedance (Zo) of the transmission line and the output impedance (Zout) on the writer side are set as follows. 5. The recording apparatus according to claim 4, wherein the resistance (Rh) of the recording head is smaller than (Zo), and the output impedance (Zout) of the writer is larger than (Zo). 6. The resistance (Rh) of the recording head (Zo) is made larger than the resistance (Rh) of the recording head in a range of Zout> Zo.
The recording device according to any one of the preceding claims. 7. A recording device comprising a driver for outputting a recording current and a writer comprising an output impedance setting circuit, a transmission line connected to the output of the writer, and a recording system for connecting a recording head to the opposite side of the transmission line. A recording device, comprising: a resistor in the output impedance setting circuit. 8. The driver according to claim 1, wherein the first resistor element is connected between a connection terminal to one output of the driver and a connection terminal to one of the transmission lines and the other output of the driver. A second resistance element connected between a connection terminal and a connection terminal of the other of the transmission lines; and a second resistance element connected between the first resistance element and one of the transmission line connection terminals. 8. The recording apparatus according to claim 7, wherein the third resistance element is connected to the other transmission line connection terminal across the lines.