1.  Field of the Invention
The invention generally relates to a magnetic field sensing apparatus. 
2.  Description of Related Art
With the popularity of portable electronic devices, electronic compass technology capable of sensing a geomagnetic direction has come to attention.  When the electronic compass is applied to a portable electronic device with small volume (such as a smart phone), the electronic compass, in addition to being required to comply with the requirement of small volume, is further desired to be capable of achieving a triaxial sensing, and this is because when the smart phone is gripped by a user's hand, it may be slantly gripped, whereby various different grip angles may also be possible.  In addition, the electronic compass may also be applied to a drone (e.g., a remote control aircraft, a remote control helicopter, and etc.),  and it is also desired that the electronic compass can achieve the triaxial sensing. 
A conventional technology achieves the triaxial sensing by means of using complex sensing element, such that, specifically, the triaxial sensing is achieved by using two giant magnetoresistive (GMR) multilayer structures (or tunneling magnetoresistive (TMR) multilayer structures), which are disposed perpendicular to each other, and a hall element.  However, since a detection sensitivity of the hall element is different from a detection sensitivity of the GMR multilayer structures (or the TMR multilayer structures), this causes a precision on one of the axes to be different from precisions on the other two axes.  As a result, when the user rotates the portable electronic device to a different angle, the detection sensitivities with respect to a same magnetic field are different, thereby causing distress in the use. 
In the conventional technology, in order to achieve a multi-axis sensing of the magnetic field, more than two times of manufacturing process are usually used, that is, using manufacturing processes of more than two wafers to manufacture a multi-axial magnetic field sensing module, and thus the overall manufacturing process is complicated and the manufacturing cost is difficult to be lowered.  In addition, this also causes the magnetic field sensing apparatus difficult to be further minimized.