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Robust Hard Disk Drive against Electromagnetic Noise from an apparatus like Cellular Phone.

IP.com Disclosure Number: IPCOM000127535D
Publication Date: 2005-Aug-31
Document File: 2 page(s) / 7K

Publishing Venue

The IP.com Prior Art Database

Abstract

In these days, wireless equipment like "cellular phone" and "wireless LAN" are increasing. And many troubles due to electronic magnetic interference are reported. Hard Disk Drive (HDD) is also affected on a servo compensation circuit, Voice Coil Motor (VCM) drive lines, a shock detection circuit, data lines and etc. Generally a metallic shielding is used for avoiding the electromagnetic interference. But it is very difficult to be perfect shielding against strong electronic field strength over 100v/m and high frequency wave over 900MHz. It is useful to stop the HDD operation for protecting data by detecting the electronic magnetic wave with an antenna like micro strip line on a pattern circuit board. However it may be problem to stop the operation in long time under the continuous disturbance at the view point of performance. So it is needed to add some devices on the pattern circuit board for increasing robustness against the electromagnetic wave and avoiding the performance degradation. And it is possible to lower the sensing level of the electromagnetic wave with the antenna in the case of using these devices.

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Robust Hard Disk Drive against Electromagnetic Noise from an apparatus like Cellular Phone.

It is considered the electromagnetic wave of the electronic field length around 100-200 v/m, the frequency around 900MHz - 1.5GHz and the modulation frequency around 50Hz.

<For servo compensation circuit>

The electromagnetic noise makes 50Hz Repeatable Run Out (RRO).

Additional logical integrator is able to keep the RRO small in the following mode. Because the integrator can increase the servo gain in the lower frequency (<500Hz).

<For shock detection circuit>

Shock sensor uses relatively low frequency. So low pass filter (LC, fc=700MHz) and differential signal approach is effective.

<LPF> L or LC for Shock Detection Circuit.

--------- L (Ferritte,etc) -----------+--------------
                                      |                                       = C(Optional)                                       |                                      ---                                      ///

<For data line>

Data line uses high frequency. So band elimination filter (open stub) is effective.

Or a special form guarding pattern can protect the noise. The pattern looks like a micro strip line.

<BEF> Open Stub(≒λ/4) or LC for Data Line.

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