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

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.

1 . 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.    
   
   
       2 . A magnetic sensor according to  claim 1 , 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.    
   
   
       3 . A magnetic sensor according to  claim 1 , further comprising a digital signal processing circuit formed on said substrate.  
   
   
       4 . A magnetic sensor according to  claim 2 , 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.    
   
   
       5 . A magnetic sensor according to  claim 4 , wherein the lower electrode is made of conductive nonmagnetic metal material.  
   
   
       6 . A magnetic sensor according to  claim 4 , wherein the antiferromagnetic film is made of PtMn.  
   
   
       7 . A magnetic sensor according to  claim 4 , wherein the insulating film is made of Al2O3 or AlO.  
   
   
       8 . A magnetic sensor according to  claim 4 , wherein the ferromagnetic film is made of NiFe.  
   
   
       9 . A magnetic sensor according to  claim 4 , wherein the first ferromagnetic film is the pinned layer and the second ferromagnetic film is the free layer.  
   
   
       10 . 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.    
   
   
       11 . A direction measuring method according to  claim 10 , 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.