Portable electronic apparatus with azimuth measuring function, magnetic sensor suitable for the apparatus, and azimuth measuring method for the apparatus

• US 20030013507A1
• Filed: 07/09/2002
• Published: 01/16/2003
• Est. Priority Date: 07/10/2001
• Status: Active Grant

• Current Assignee: Yamaha Corporation
• Original Assignee: Yamaha Corporation
• Inventors: Sato, Hideki
• Granted Patent: US 7,197,343 B2
• Time in Patent Office: Days
• US Class Current: 455/575.1
• CPC Class Codes: G01C 17/28 Electromagnetic compasses with north seeking magnetic elements and having electric pick-offs G01C17/26
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses
• CPC Class Codes: H04M 1/21 Combinations with auxiliary equipment, e.g. with clocks or memoranda pads
• CPC Class Codes: H04M 1/72403 with means for local support of applications that increase the functionality
• CPC Class Codes: H04M 2250/12 including a sensor for measuring a physical value, e.g. temperature or motion

Abstract

A portable phone has a CPU and a magnetic sensor unit including an X-axis magnetic sensor, a Y-axis magnetic sensor, and a temperature sensor. CPU measures at first and second temperatures the influence of a magnetic field of permanent magnets upon an output Sx of the X-axis magnetic sensor and an output Sy of the Y-axis magnetic sensor, and stores the influence data together with the first and second temperature data. CPU estimates at the present temperature the influence upon the output Sx of the X-axis magnetic sensor and the output Sy of the Y-axis magnetic sensor, from the present temperature detected with the temperature sensor and the stored influence data. CPU corrects the outputs Sx and Sy in accordance with the estimated influence and determines the direction of the portable phone from the corrected outputs Sx and Sy.

Claims

1. A portable electronic apparatus comprising:

a casing;

a communication device accommodated in said casing and having permanent magnets; and

a direction measuring device accommodated in said casing for measuring a direction by utilizing geomagnetism,

wherein said direction measuring device comprises;

magnetic sensors for outputting signals corresponding to an external magnetic field;

a temperature sensor for detecting a temperature;

a corrector for estimating influence of the magnetic field of the permanent magnets upon the signals output from said magnetic sensors in accordance with the detected temperature, and correcting the signals output from said magnetic sensors in accordance with the estimated influence; and

a direction determining device for determining a direction in accordance with the corrected signals.

2. A portable electronic apparatus according to claim 1, wherein said casing has a first plane, and the portable electronic apparatus further comprises an input device formed on the first plane for inputting an operation signal.

3. A portable electronic apparatus according to claim 1, wherein said communication device includes a speaker.

4. A portable electronic apparatus according to claim 1, wherein said communication device includes a microphone.

5. A portable electronic apparatus according to claim 1, wherein said corrector measures at a first temperature the influence of the magnetic field of the permanent magnets contained in the signals output from said magnetic sensors, measures at a second temperature different from the first temperature the influence of the magnetic field of the permanent magnets contained in the signals output from said magnetic sensors, and estimates the influence of the magnetic field of the permanent magnets from the influence at the first temperature, the influence at the second temperature, and the present temperature detected with said temperature sensor.

6. A portable electronic apparatus according to claim 5, wherein said corrector includes an initialization prompting device for prompting a user of the portable electronic apparatus to perform an operation of acquiring the influence at the second temperature when a difference between the first temperature and a temperature detected with said temperature sensor after measuring the influence at the first temperature becomes a predetermined temperature or higher.

7. A portable electronic apparatus according to claim 6, wherein said predetermined temperature is selected from the range of 5-25°

C.

8. A portable electronic apparatus according to claim 6, wherein said initialization prompting device includes a character display device.

9. A magnetic sensor comprising:

a substrate;

a magnetic sensor element formed on said substrate for outputting a signal corresponding to the direction and amplitude of an external magnetic field; and

a temperature sensor formed on said substrate for sensing a temperature.

10. A magnetic sensor according to claim 9, wherein:

the magnetic sensor includes a plurality of magnetic sensor elements;

said magnetic sensor element is a magnetoresistive effect element having a pinned layer with a fixed magnetization direction and a free layer whose magnetization direction changes with the external magnetic field, and said magnetic sensor element changes its resistance value in accordance with an angle between the magnetization direction of the pinned layer and the magnetization direction of the free layer; and

the magnetization directions of the pinned layers of at least two elements among the plurality magnetoresistive effect elements are crossed.

11. A magnetic sensor according to claim 9, further comprising a digital signal processing circuit formed on said substrate.

12. A magnetic sensor according to claim 10, wherein the magnetoresistive effect element comprises:

a lower electrode formed on said substrate;

an antiferromagnetic film formed on the lower electrode;

a first ferromagnetic film formed on the antiferromagnetic film;

an insulating film formed on the first ferromagnetic film; and

a second ferromagnetic film formed on the insulating film.

13. A magnetic sensor according to claim 12, wherein the lower electrode is made of conductive nonmagnetic metal material.

14. A magnetic sensor according to claim 12, wherein the antiferromagnetic film is made of PtMn.

15. A magnetic sensor according to claim 12, wherein the insulating film is made of Al₂O₃ or AlO.

16. A magnetic sensor according to claim 12, wherein the ferromagnetic film is made of NiFe.

17. A magnetic sensor according to claim 12, wherein the first ferromagnetic film is the pinned layer and the second ferromagnetic film is the free layer.

19. A direction measuring method according to claim 18, wherein the influence of the magnetic field of the permanent magnets upon the signals of the magnetic sensors is estimated considering also a temperature of the permanent magnets.

18. A direction measuring method comprising steps of:

preparing a portable electronic apparatus comprising a casing having a first plane, a communication device accommodated in the casing and having permanent magnets, magnetic sensors accommodated in the casing and outputting signals corresponding to an external magnetic field, and an input device formed on the first plane for inputting an operation signal;

measuring signals output from the magnetic sensors as first values when the operation signal is input, in a state that the first plane of the portable electronic apparatus is turned upside;

measuring signals output from the magnetic sensors as second values when the operation signal is input, in a state that the first plane of the portable electronic apparatus is turned upside and the portable electronic apparatus is rotated by 180°

after the first values are measured;

estimating an influence of a magnetic field by the permanent magnets upon the signals output from the magnetic sensors in accordance with the first and second values;

correcting the signals output from the magnetic sensors in accordance with the estimated influence; and

determining a direction in accordance with the corrected signals of the magnetic sensors.