Position demodulating method and circuit of disk apparatus

1. A position demodulating method of a disk apparatus, for calculating a decoded position after position signals of a disk read by a head were demodulated, comprising:

a first step wherein after position information of different phases are demodulated from said position signals, they are multiplied by a position sensitivity gain, respectively, and first position information PosN and second position information PosQ are calculated;

a second step wherein said first position information PosN and said second position information PosQ are compared and third position information Pos 1 and fourth position information Pos 2 in which influences of an error of the position sensitivity gain appear oppositely are calculated; and

a third step wherein a first weight gain G 1 and a second weight gain G 2 are obtained from said third position information Pos 1 and said decoded position is calculated by including an addition value of a multiplication value obtained by multiplying said third position information by said first weight gain and a multiplication value obtained by multiplying said fourth position information by said second weight gain;

wherein said first weight gain is a segment primary function which changes like a triangle for a detected position so as to be equal to 1 at a track center and 0 at track boundary positions on both sides.

2. A position demodulating method of a disk apparatus, for calculating a decoded position after position signals of a disk read by a head were demodulated, comprising:

a first step wherein after position information of different phases are demodulated from said position signals, they are multiplied by a position sensitivity gain, respectively, and first position information PosN and second position information PosQ are calculated;

a second step wherein said first position information PosN and said second position information PosQ are compared and third position information Pos 1 and fourth position information Pos 2 in which influences of an error of the position sensitivity gain appear oppositely are calculated; and

a third step wherein a first weight gain G 1 and a second weight gain G 2 are obtained from said third position information Pos 1 and said decoded position is calculated by including an addition value of a multiplication value obtained by multiplying said third position information by said first weight gain and a multiplication value obtained by multiplying said fourth position information by said second weight gain;

wherein said first weight gain is a segment primary function which changes like a triangle for a detected position which is set to 1 at a track center and which is restricted to a lower limit value 0.5 at a position near a switching position of said position information PosN and PosQ on both sides.

3. A position demodulating method of a disk apparatus, for calculating a decoded position after position signals of a disk read by a head were demodulated, comprising:

a first step wherein after position information of different phases are demodulated from said position signals, they are multiplied by a position sensitivity gain, respectively, and first position information PosN and second position information PosQ are calculated;

a second step wherein said first position information PosN and said second position information PosQ are compared and third position information Pos 1 and fourth position information Pos 2 in which influences of an error of the position sensitivity gain appear oppositely are calculated; and

a third step wherein a first weight gain G 1 and a second weight gain G 2 are obtained from said third position information Pos 1 and said decoded position is calculated by including an addition value of a multiplication value obtained by multiplying said third position information by said first weight gain and a multiplication value obtained by multiplying said fourth position information by said second weight gain;

wherein said first weight gain is a segment primary function which changes like a trapezoid for a detected position which is set to 1 at a position in front of a switching position of said position information PosN and PosQ on both sides from a track center and which is restricted to a lower limit value 0.5 at a position near said switching position.

4. A position demodulating method of a disk apparatus, for calculating a decoded position after position signals of a disk read by a head were demodulated, comprising:

a first step wherein after position information of different phases are demodulated from said position signals, they are multiplied by a position sensitivity gain, respectively, and first position information PosN and second position information PosQ are calculated;

a second step wherein said first position information PosN and said second position information PosQ are compared and third position information Pos 1 and fourth position information Pos 2 in which influences of an error of the position sensitivity gain appear oppositely are calculated; and

a third step wherein a first weight gain G 1 and a second weight gain G 2 are obtained from said third position information Pos 1 and said decoded position is calculated by including an addition value of a multiplication value obtained by multiplying said third position information by said first weight gain and a multiplication value obtained by multiplying said fourth position information by said second weight gain;

wherein said first weight gain is a curve function which changes for a detected position which is set to 1 at a position in front of a switching position of said position information PosN and PosQ on both sides from a track center and which is restricted to a lower limit value 0.5 at a position near said switching position.

5. A method according to claim 2 , wherein

said first weight gain is determined with reference to said segment primary function by said third position information in which saturation characteristics have been corrected.

6. A method as in claim 1 , 2 , 3 or 4 , wherein with respect to said first weight gain, said second weight gain is set to a value obtained by subtracting the first weight gain from 1.

7. A method as in claim 1 , 2 , 3 or 4 , wherein in said second step, a first speed correcting position and a second speed correcting position which are proportional to a moving speed of the head are obtained every said third position information Pos 1 and said fourth position information Pos 2 and added.

8. A position demodulating circuit of a disk apparatus, for calculating a decoded position after position signals of a disk read by a head were demodulated, comprising:

a first circuit unit which demodulates position information of different phases from said position signals, subsequently multiplies said position information by a position sensitivity gain, respectively, and calculates first position information PosN and second position information PosQ;

a second circuit unit which compares said first position information PosN with said second position information PosQ and calculates third position information Pos 1 and fourth position information Pos 2 in which influences of an error of the position sensitivity gain appear oppositely; and

a third circuit unit which obtains a first weight gain and a second weight gain from said third position information Pos 1 and calculates said decoded position by including an addition value of a multiplication value obtained by multiplying said third position information by said first weight gain and a multiplication value obtained by multiplying said fourth position information by said second weight gain;

wherein said first weight gain is a segment primary function which changes like a triangle for a detected position so as to be equal to 1 at a track center and 0 at track boundary positions on both sides.

9. A position demodulating circuit of a disk apparatus, for calculating a decoded position after position signals of a disk read by a head were demodulated, comprising:

a first circuit unit which demodulates position information of different phases from said position signals, subsequently multiplies said position information by a position sensitivity gain, respectively, and calculates first position information PosN and second position information PosQ;

a second circuit unit which compares said first position information PosN with said second position information PosQ and calculates third position information Pos 1 and fourth position information Pos 2 in which influences of an error of the position sensitivity gain appear oppositely; and

a third circuit unit which obtains a first weight gain and a second weight gain from said third position information Pos 1 and calculates said decoded position by including an addition value of a multiplication value obtained by multiplying said third position information by said first weight gain and a multiplication value obtained by multiplying said fourth position information by said second weight gain;

wherein said first weight gain is a segment primary function which changes like a triangle for a detected position which is set to 1 at a track center and which is restricted to a lower limit value 0.5 at a position near a switching position of said position information PosN and PosQ on both sides.

10. A position demodulating circuit of a disk apparatus, for calculating a decoded position after position signals of a disk read by a head were demodulated, comprising:

a first circuit unit which demodulates position information of different phases from said position signals, subsequently multiplies said position information by a position sensitivity gain, respectively, and calculates first position information PosN and second position information PosQ;

a second circuit unit which compares said first position information PosN with said second position information PosQ and calculates third position information Pos 1 and fourth position information Pos 2 in which influences of an error of the position sensitivity gain appear oppositely; and

a third circuit unit which obtains a first weight gain and a second weight gain from said third position information Pos 1 and calculates said decoded position by including an addition value of a multiplication value obtained by multiplying said third position information by said first weight gain and a multiplication value obtained by multiplying said fourth position information by said second weight gain;

wherein said first weight gain is a segment primary function which changes like a trapezoid for a detected position which is set to 1 at a position in front of a switching position of said position information PosN and PosQ on both sides from a track center and which is restricted to a lower limit value 0.5 at a position near said switching position.

11. A position demodulating circuit of a disk apparatus, for calculating a decoded position after position signals of a disk read by a head were demodulated, comprising:

a first circuit unit which demodulates position information of different phases from said position signals, subsequently multiplies said position information by a position sensitivity gain, respectively, and calculates first position information PosN and second position information PosQ;

a second circuit unit which compares said first position information PosN with said second position information PosQ and calculates third position information Pos 1 and fourth position information Pos 2 in which influences of an error of the position sensitivity gain appear oppositely; and

a third circuit unit which obtains a first weight gain and a second weight gain from said third position information Pos 1 and calculates said decoded position by including an addition value of a multiplication value obtained by multiplying said third position information by said first weight gain and a multiplication value obtained by multiplying said fourth position information by said second weight gain;

wherein said first weight gain is a curve function which changes for a detected position which is set to 1 at a position in front of a switching position of said position information PosN and PosQ on both sides from a track center and which is restricted to a lower limit value 0.5 at a position near said switching position.

12. A circuit according to claim 11 , wherein

said first weight gain is determined with reference to said segment primary function by said third position information in which saturation characteristics have been corrected.

13. A circuit in claim 8 , 9 , 10 or 11 , wherein said second circuit unit obtains a first speed correcting position and a second speed correcting position which are proportional to a moving speed of the head every said third position information Pos 1 and said fourth position information Pos 2 and adds them.

14. A circuit as in claim 8 , 9 , 10 or 11 , wherein with respect to said first weight gain, said second weight gain is set to a value obtained by subtracting the first weight gain from 1.