Author: claimsbot

1. A method for reducing a signal dynamic range, comprising:
producing a first digital signal on a first carrier frequency, and at least one second digital signal on a second carrier frequency using first and second clock signals, respectively, the first and second clock signals having a respective clock frequency;
evaluating an amplitude component of the first and second digital signals by forecasting an impulse response from each of a first filter and a second filter, respectively, for different instants within a clock period of the respective clock frequency;
ascertaining a correction factor by comparing the evaluated amplitude components with a threshold value;
selectively altering at least one signal from the set of the first and at least one second signal with the correction factor;
filtering the at least one altered signal of the first and the at least one second digital signal with a respective one of the first filter and the second filter; and
adding the filtered signals to form a total signal.
2. The method of claim 1, wherein evaluating an amplitude component comprises:
producing a plurality of forecast signals that respectively represent an output value which is brought about at different instants within a clock period of the respective clock frequency by a forecast impulse response of the filter;
combining the forecast signals produced from the first and the at least one second digital signal to form a total forecast signal such that the output values respectively produced for the same instant within a clock period of the respective clock frequency are combined.
3. The method of claim 2, wherein the number of forecast signals for each signal corresponds at least to four times the number of the first and the at least one second signal.
4. The method of claim 1, wherein the filtering comprises interpolating the at least one altered signal or the first and the at least one second digital signal.
5. A circuit arrangement for reducing the crest factor, comprising:
a first signal generator configured to produce a first digital signal with a clock period, the first digital signal having an amplitude component;
a second signal generator configured to produce a second digital signal, the second digital signal having an amplitude component;
a correction device whose input is connected to the first and the second signal generator and which has a first and a second output;
a first shaping filter for interpolation, connected to the first output of the correction device;
a second shaping filter for interpolation, connected to the second output of the correction device; and
a summation component connected to the first and the second shaping filter, and configured to add together the digital signals which are output by the first and the second shaping filter;
wherein the correction device comprises:
a first forecast device configured to receive the first digital signal and generate a first forecast output reflecting a forecast impulse response of the first shaping filter comprising a plurality of first signal elements, wherein each of the plurality of first signal elements is associated with a respective one of a plurality of different phases associated with the clock period;
a second forecast device configured to receive the second digital signal and generate a second forecast output reflecting a forecast impulse response of the second shaping filter comprising a plurality of second signal elements, wherein each of the second signal elements is associated with a respective one of the plurality of different phases associated with the clock period;
an adder component configured to sum respective first and second signal elements of a given phase for each of the plurality of different phases, thereby generating a plurality of total forecast signals associated with the plurality of different phases; and
a correction value generator configured to receive the plurality of total forecast signals and generate correction values based on the plurality of total forecast signals.
6. The circuit arrangement of claim 5, further comprising:
a first and second plurality of mixing devices associated with each of the first and second forecast devices, wherein each of the plurality of first and second mixing devices is associated with a respective one of the plurality of different phases associated with the clock period; and
first and second numerically controlled oscillators coupled to each of the first and second plurality of mixing devices of the first and second forecast devices, respectively,
wherein the first mixing devices are configured to multiply a first plurality of digital oscillator signals from the first numerically controlled oscillator with respective ones of the plurality of first signal elements to generate frequency shifted first signal elements, and
wherein the second mixing devices are configured to multiply a second plurality of digital oscillator signals from the second numerically controlled oscillator with respective ones of the plurality of second signal elements to generate frequency shifted second signal elements.
7. The circuit arrangement of claim 6, wherein the first and second numerically controlled oscillators are configured to generate a first and second plurality of digital oscillator signals associated with different frequencies.
8. The circuit arrangement of claim 6, wherein the adder component is configured to sum respective first and second frequency shifted elements of a given phase for each of the plurality of different phases to thereby generate the plurality of total forecast signals.
9. The circuit arrangement of claim 5, wherein each of the first and second forecast devices comprise a plurality of filters, wherein each of the plurality of filters is associated with a respective one of the plurality of different phases, and wherein an output of each of the plurality of filters provides collectively the plurality of first and second signal elements, respectively.
10. The circuit arrangement of claim 5, wherein each of the first and second forecast devices comprise:
a first number of filters configured to generate a forecast; and
a first number of sample and hold circuits configured to repeat the forecast from a respective filter a predetermined number of times, wherein the first number multiplied by the predetermined number corresponds to the plurality of different phases of the clock period.
11. The circuit arrangement of claim 5, wherein the correction value generator is configured to produce an error signal from a comparison between each of the plurality of total forecast signals and a threshold value, thereby resulting in a plurality of error signals.
12. The circuit arrangement of claim 11, wherein each error signal is dependent on the threshold value when the threshold value is exceeded.
13. The circuit arrangement of claim 11, wherein the correction value generator is further configured to generate the correction values based on the plurality of error signals.
14. The circuit arrangement of claim 11, wherein the correction value generator further comprises one or more weighting factors for each of the plurality of error signals, and wherein the correction value generator is configured to generate the correction values based on the plurality of weighted error signals.

The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.

1. An optical device that connects, by a signal beam, between an externally inputted input signal and an output signal to be outputted, the optical device comprising:
a sheet-form optical transmission line having a refractive index distribution such that a highest refractive index part is provided in a direction of a thickness of the optical transmission line and a refractive index does not increase with distance from the highest refractive index part in the direction of the thickness of the optical transmission line,
wherein a signal beam corresponding to the input signal is made incident on the optical transmission line as an incident beam,
wherein inside the optical transmission line, the incident beam is transmitted, in a direction of a length of the optical transmission line that is orthogonal to the direction of the thickness of the optical transmission line, in multiple modes having a plurality of eigenmodes in a direction of a width of the optical transmission line that is orthogonal to both the direction of the length of the optical transmission line and the direction of the thickness of the optical transmission line, and an exiting beam is generated by the plurality of eigenmodes interfering with each other in the direction of the length of the optical transmission line,
wherein the exiting beam is made to exit from the optical transmission line, and the output signal corresponding to the exiting beam is outputted,
wherein the optical transmission line has a refractive index distribution such that a central position in the direction of the thickness of the optical transmission line has the highest refractive index and the refractive index does not increase with distance from the central position, and
wherein the optical transmission line is made of polysilane, and the refractive index distribution is provided by an oxygen concentration distribution when the polysilane is cured.
2. An optical device according to claim 1, wherein the optical transmission line has a size, in the direction of the length of the optical transmission line, expressed by a function of a difference between a propagation constant of a 0th-order mode excited in the direction of the width of the optical transmission line and a propagation constant of a primary mode.
3. An optical device according to claim 1, wherein the optical transmission line has a size, in the direction of the length of the optical transmission line, expressed by a function of a basic mode width in the direction of the width of the optical transmission line, the highest refractive index in the direction of the thickness of the optical transmission line, and a wavelength of a beam transmitted in the multi-mode optical transmission line.
4. An optical device according to claim 1, wherein the refractive index distribution changes substantially along a quadratic function.
5. An optical device according to claim 1, wherein the input signal is an electric signal, and an incident portion is provided that converts the electric signal into the signal beam and makes the signal beam incident on the optical transmission line as the incident beam.
6. An optical device according to claim 5, wherein the incident portion has a plurality of light emitting portions disposed in an array in the direction of the width of the optical transmission line.
7. An optical device according to claim 1, wherein the input signal is a signal beam, and an incident portion is provided that makes the signal beam incident on the optical transmission line as the incident beam.
8. An optical device according to claim 1, wherein the output signal is an electric signal, and an exit portion is provided that receives the signal beam as the exiting beam having exited from the optical transmission line and converts the signal beam into the electric signal.
9. An optical device according to claim 8, wherein the exit portion has a plurality of light receiving portions disposed in an array in the direction of the width of the optical transmission line.
10. An optical device according to claim 1, wherein the output signal is a signal beam, and an exit portion is provided that makes the signal beam exit from the optical transmission line as the exiting beam.
11. An optical device according to claim 1, wherein the optical device is a 1\xd7N optical splitting device that is capable of receiving at least one input signal and outputting the input signal as a number, N (N=1,2,3, . . . ), of output signals, and
wherein the optical transmission line includes:
an incident surface for making the incident beam incident; and
an exit surface for making the exiting beam exit,
the size in the direction of the length of the optical transmission line is a value that is substantially an integral multiple of the following expression when the basic mode width in the direction of the width of the optical transmission line is W0, an effective refractive index of a 0th-order mode beam excited in the direction of the width of the optical transmission line is n0 and the wavelength of the beam transmitted in the multi-mode optical transmission line is \u03bb, and
one incident beam is made incident on a center in the direction of the width of the optical transmission line on the incident surface and a number, N, of exiting beams are generated symmetrically with respect to the center in the direction of the width of the optical transmission line on the exit surface:
1
N

\xb7
n
0

\u2062

W
0
2
\u03bb

.
12. An optical device according to claim 1, wherein the optical device is an N\xd71 optical combining device that is capable of receiving a number, N (N=1,2,3, . . . ), of input signals and outputting the input signals as at least one output signal, and
wherein the optical transmission line includes:
an incident surface for making the incident beam incident; and
an exit surface for making the exiting beam exit,
the size in the direction of the length of the optical transmission line is a value that is substantially an integral multiple of the following expression when the basic mode width in the direction of the width of the optical transmission line is W0, an effective refractive index of a 0th-order mode beam excited in the direction of the width of the optical transmission line is n0 and the wavelength of the beam transmitted in the multi-mode optical transmission line is \u03bb, and
a number, N, of incident beams all having the same wavelength \u03bb are made incident symmetrically with respect to a center in the direction of the width of the optical transmission line on the incident surface and one exiting beam is generated at the center in the direction of the width of the optical transmission line on the exit surface:
1
N

\xb7
n
0

\u2062

W
0
2
\u03bb

.
13. An optical device according to claim 1, wherein the optical device is a straight sheet bus that is capable of receiving a number, N (N=1,2,3, . . . ), of input signals and outputting the input signals as a number, N, of output signals corresponding one-to-one to the input signals, and
wherein the optical transmission line includes:
an incident surface for making the incident beam incident; and
an exit surface for making the exiting beam exit,
the size in the direction of the length of the optical transmission line is a value that is substantially an integral multiple of the following expression when the basic mode width in the direction of the width of the optical transmission line is W0, an effective refractive index of a 0th-order mode beam excited in the direction of the width of the optical transmission line is n0 and the wavelength of the beam transmitted in the multi-mode optical transmission line is \u03bb, and
a number, N, of incident beams all having the same wavelength \u03bb are made incident on given positions in the direction of the width of the optical transmission line on the incident surface and a number, N, of exiting beams corresponding one-to-one to the number, N, of incident beams are generated in positions, on the exit surface, whose positions in the direction of the width of the optical transmission line are the same as incident positions of the incident beams:
8
\u2062

n
0

\u2062

W
0
2
\u03bb

.
14. An optical device according to claim 1, wherein the optical device is a cross sheet bus that is capable of receiving a number, N (N=1,2,3, . . . ), of input signals and outputting the input signals as a number, N, of output signals corresponding one-to-one to the input signals, and
wherein the optical transmission line includes:
an incident surface for making the incident beam incident; and
an exit surface for making the exiting beam exit,
a size in the direction of the length of the optical transmission line is a value that is substantially an odd multiple of the following expression when the basic mode width in the direction of the width of the optical transmission line is W0, an effective refractive index of a 0th-order mode beam excited in the direction of the width of the optical transmission line is n0 and the wavelength of the beam transmitted in the multi-mode optical transmission line is \u03bb, and
a number, N, of incident beams all having the same wavelength \u03bb are made incident on given positions in the direction of the width of the optical transmission line on the incident surface and a number, N, of exiting beams corresponding one-to-one to the number, N, of incident beams are generated in positions, on the exit surface, whose positions in the direction of the width of the optical transmission line are symmetrical to incident positions of the incident beams with respect to the center in the direction of the width of the optical transmission line:
4
\u2062

n
0

\u2062

W
0
2
\u03bb

.
15. An optical device according to claim 1, wherein the optical device is a star coupler that receives a number, N (N=1,2,3, . . . ), of input signals and outputs the input signals as a number, N, of output signals corresponding to the input signals, and
wherein the optical transmission line includes:
an incident surface for making the incident beam incident; and
an exit surface for making the exiting beam exit,
a size in the direction of the length of the optical transmission line is substantially a value of the following expression when the basic mode width in the direction of the width of the optical transmission line is W0, an effective refractive index of a 0th-order mode beam excited in the direction of the width of the optical transmission line is n0 and the wavelength of the beam transmitted in the multi-mode optical transmission line is \u03bb, and
a number, N, of incident beams all having the same wavelength \u03bb are made incident on predetermined positions in the direction of the width of the optical transmission line on the incident surface and a number, N, of exiting beams are generated for any one of the incident beams in positions, on the exit surface, whose positions in the direction of the width of the optical transmission line are symmetrical to incident positions of the incident beams with respect to the center in the direction of the width of the optical transmission line:
(

p
\xb1

1
N
)

\u2062
4
\u2062

n
0

\u2062

W
0
2
\u03bb
,
wherein p is an integer that makes the value inside the parentheses positive.
16. An optical device according to claim 15, wherein the optical device is a star coupler that receives a number, NEVEN (NEVEN=2,4,6, . . . ), of input signals and outputs the input signals as a number, NEVEN, of output signals corresponding to the input signals, and
wherein the optical transmission line makes a number, NEVEN, of incident beams all having the same wavelength \u03bb incident on positions symmetrical with respect to the center in the direction of the width of the optical transmission line on the incident surface.
17. An optical device according to claim 15, wherein the optical device is a star coupler that receives a number, NODD (NODD=1,3,5, . . . ), of input signals and outputs the input signals as a number, NODD, of output signals corresponding to the input signals, and
wherein the optical transmission line makes a number, NODD, of incident beams all having the same wavelength \u03bb incident on positions asymmetrical with respect to the center in the direction of the width of the optical transmission line on the incident surface.
18. An optical device according to claim 1, wherein the optical device is a two-way straight sheet bus that is capable of receiving a number, N (N=1,2,3, . . . ), of input signals and outputting the input signals as a number, N, of output signals corresponding one-to-one to the first input signals, and is capable of receiving a number, M (M=1,2,3, . . . ), of input signals and outputting the input signals as a number, M, of output signals corresponding one-to-one to the input signals, and
wherein the optical transmission line includes:
a first surface formed at one end in the direction of the length of the optical transmission line; and
a second surface formed at another end in the direction of the length of the optical transmission line,
a size in the direction of the length of the optical transmission line is a value that is substantially an integral multiple of the following expression when the basic mode width in the direction of the width of the optical transmission line is W0, an effective refractive index of a 0th-order mode beam excited in the direction of the width of the optical transmission line is n0 and the wavelength of the beam transmitted in the multi-mode optical transmission line is \u03bb,
a number, N, of incident beams all having the same wavelength \u03bb are made incident on given positions in the direction of the width of the optical transmission line on the first surface and a number, N, of exiting beams corresponding one-to-one to the number, N, of incident beams are generated in positions, on the second surface, whose positions in the direction of the width of the optical transmission line are the same as incident positions of the incident beams, and
a number, M, of incident beams all having the same wavelength \u03bb as the incident beams on the first surface are made incident on given positions in the direction of the width of the optical transmission line on the second surface and a number, M, of exiting beams corresponding one-to-one to the number, M, of incident beams are generated in positions, on the first surface, whose positions in the direction of the width of the optical transmission line are the same as incident positions of the incident beams:
8
\u2062

n
0

\u2062

W
0
2
\u03bb

.
19. An optical device according to claim 1, wherein the optical device is a two-way cross sheet bus that is capable of receiving a number, N (N=1,2,3, . . . ), of first input signals and outputting the input signals as a number, N, of first output signals corresponding one-to-one to the first input signals, and is capable of receiving a number, M (M=1,2,3, . . . ), of second input signals and outputting the input signals as a number, M, of output signals corresponding one-to-one to the second input signals, and
wherein the optical transmission line includes:
a first surface formed at one end in the direction of the length of the optical transmission line; and
a second surface formed at another end in the direction of the length of the optical transmission line,
a size in the direction of the length of the optical transmission line is a value that is substantially an odd multiple of the following expression when the basic mode width in the direction of the width of the optical transmission line is W0, an effective refractive index of a 0th-order mode beam excited in the direction of the width of the optical transmission line is n0 and the wavelength of the beam transmitted in the multi-mode optical transmission line is \u03bb,
a number, N, of incident beams all having the same wavelength \u03bb are made incident on given positions in the direction of the width of the optical transmission line on the first surface and a number, N, of exiting beams corresponding one-to-one to the number, N, of incident beams are generated in positions, on the second surface, whose positions in the direction of the width of the optical transmission line are symmetrical to incident positions of the incident beams with respect to the center in the direction of the width of the optical transmission line, and
a number, M, of incident beams all having the same wavelength \u03bb are made incident on given positions in the direction of the width of the optical transmission line on the second surface and a number, M, of exiting beams corresponding one-to-one to the number, M, of incident beams are generated in positions, on the first surface, whose positions in the direction of the width of the optical transmission line are symmetrical to incident positions of the incident beams with respect to the center in the direction of the width of the optical transmission line:
4
\u2062

n
0

\u2062

W
0
2
\u03bb

.
20. An optical device according to claim 1, wherein the optical transmission line includes: a reflecting surface that is formed at one end in the direction of the length of the optical transmission line and bends an optical path of the incident beam incident in a direction parallel to the direction of the thickness of the optical transmission line, substantially 90 degrees in the direction of the length of the optical transmission line; andor a reflecting surface that is formed at another end in the direction of the length of the optical transmission line and bends an optical path of the exiting beam transmitted in the direction of the length of the optical transmission line, substantially 90 degrees so as to exit in a direction parallel to the direction of the thickness of the optical transmission line.
21. An optical device according to claim 1, wherein the optical transmission line includes: a prism that is formed at one end in the direction of the length of the optical transmission line and bends, in the direction of the length of the optical transmission line, an optical path of the incident beam incident in a direction inclined in the direction of the thickness of the optical transmission line; andor a prism that is formed at another end in the direction of the length of the optical transmission line and bends an optical path of the exiting beam transmitted in the direction of the length of the optical transmission line, so as to exit in a direction inclined in the direction of the thickness of the optical transmission line.
22. An optical device according to claim 1, wherein the optical transmission line has a plurality of eigenmodes in the direction of the thickness of the optical transmission line.
23. An optical device according to claim 1, wherein the optical transmission line has a thickness of not less than 20 \u03bcm.
24. An optical device according to claim 1, wherein the optical transmission line is curved so that a central position in the direction of the thickness of the optical transmission line always draws the same curve on given two different cross sections including the direction of the length of the optical transmission line and the direction of the thickness of the optical transmission line.
25. An optical device according to claim 1, wherein the optical transmission line is twisted so that a central position in the direction of the thickness of the optical transmission line draws different curves on given two different cross sections including the direction of the length of the optical transmission line and the direction of the thickness of the optical transmission line.
26. A method of manufacturing an optical device that connects, by a signal beam, between an externally inputted input signal and an output signal to be outputted,
wherein the optical device comprises
a sheet-form optical transmission line having a refractive index distribution such that a highest refractive index part is provided in a direction of a thickness of the optical transmission line and a refractive index does not increase with distance from the highest refractive index part in the direction of the thickness of the optical transmission line,
wherein a signal beam corresponding to the input signal is made incident on the optical transmission line as an incident beam,
wherein inside the optical transmission line, the incident beam is transmitted, in a direction of a length of the optical transmission line that is orthogonal to the direction of the thickness of the optical transmission line, in multiple modes having a plurality of eigenmodes in a direction of a width of the optical transmission line that is orthogonal to both the direction of the length of the optical transmission line and the direction of the thickness of the optical transmission line, and an exiting beam is generated by the plurality of eigenmodes interfering with each other in the direction of the length of the optical transmission line,
wherein the exiting beam is made to exit from the optical transmission line, and the output signal corresponding to the exiting beam is outputted,
wherein the optical transmission line has a refractive index distribution such that a central position in the direction of the thickness of the optical transmission line has the highest refractive index and the refractive index does not increase with distance from the central position,
wherein the optical transmission line is made of polysilane, and the refractive index distribution is provided by an oxygen concentration distribution when the polysilane is cured, and
wherein the optical device manufacturing method comprises:
a first step of preparing a forming die that is made of a material capable of transmitting an energy to be applied to cure a resin of which the optical transmission line is made, and includes a concave portion having at least the same depth as the direction of the thickness of the optical transmission line;
a second step of filling the concave portion with the resin;
a third step of applying the energy in a predetermined quantity to the forming die filled with the resin, from above and below in the direction of the thickness of the optical transmission line; and
a fourth step of, on the resin cured with a desired refractive index distribution being formed, determining at least a size in the direction of the length of the optical transmission line and forming a part of connection of the incident and exiting beams in order to form the resin into the optical transmission line.
27. An optical device manufacturing method according to claim 26, wherein in the third step,
the application of the energy is an application of an ultraviolet ray of a predetermined wavelength, and
wherein in the first step,
the prepared forming die is made of a material that is transparent with respect to the ultraviolet ray of the predetermined wavelength.
28. An optical device manufacturing method according to claim 26, wherein in the third step,
the application of the energy is heating.
29. An optical device manufacturing method according to claim 26, wherein the refractive index distribution changes substantially along a quadratic function.
30. An optical device manufacturing method according to claim 26, wherein in the first step,
the forming die includes a concave portion having a size including a plurality of optical transmission lines to be manufactured, and
wherein in the fourth step,
a plurality of optical transmission lines are simultaneously manufactured by cutting the resin.
31. An optical device manufacturing method according to claim 26, wherein in the first step,
the forming die includes a concave portion having a size substantially equal to a size, in the direction of the width of the optical transmission line, of the optical transmission line to be manufactured, and
wherein in the fourth step,
the size in the direction of the length of the optical transmission line is determined by cutting the resin.
32. An optical device manufacturing method according to claim 26, wherein in the first step,
the forming die includes a concave portion having a size substantially equal to a size of the optical transmission line to be manufactured, and
wherein in the fourth step,
a wall, of the concave portion, situated in a position where the incident beam and the exiting beam are made incident and made to exit on and from the optical transmission line is removed.
33. An optical device manufacturing method according to claim 26, further comprising a fifth step of releasing the optical transmission line from the forming die either before or after the fourth step.

1. A spindle motor, comprising:
a turntable coupled to a rotating shaft, and supporting the rotating shaft and a disc;
a centering unit fitted over the rotating shaft, and supporting an inner circumference of the disc; and
a coil spring interposed between the turntable and the centering unit to elastically support the centering unit,
wherein a first end of the coil spring is brought into contact with a spring hanging portion protruding from a side surface of the centering unit, and a second end opposite to the first end of the coil spring is supported by a spring support portion formed in the turntable.
2. The spindle motor as set forth in claim 1, wherein the first end of the coil spring has a first diameter, and the second end has a second diameter that is greater than the first diameter.
3. The spindle motor as set forth in claim 2, wherein an angle between an imaginary line extending along an outer surface of the coil spring and a vertical line parallel to an axial direction of the rotating shaft ranges from 2\xb0 to 12%.
4. The spindle motor as set forth in claim 3, wherein the angle between the imaginary line and the vertical line is T.
5. The spindle motor as set forth in claim 1, wherein the spring hanging portion protrudes from the side surface of the centering unit in a shape of an annular protrusion.
6. The spindle motor as set forth in claim 1, wherein the spring hanging portion comprises a plurality of hanging protrusions that protrude from the side surface of the centering unit.
7. The spindle motor as set forth in claim 1, wherein the spring support portion has a shape of an annular trench when viewed on a plane.
8. The spindle motor as set forth in claim 1, further comprising:
a base plate;
a stator including a bearing housing coupled to the base plate, a bearing inserted into the bearing housing and rotatably supporting the rotating shaft, a core coupled to an outer circumference of the bearing housing, and a coil coupled to the core; and
a rotor including a yoke coupled to the rotating shaft and supporting the turntable, and a magnet coupled to an inner surface of the yoke and facing the core.
9. The spindle motor as set forth in claim 1, wherein the centering unit includes a body having a shape of a container that is open at a top thereof and forming the side surface, and a centering portion inclined from an upper end of the body to a lower end opposite to the upper end of the body.
10. The spindle motor as set forth in claim 1, wherein the coil spring is formed by winding a wire in a shape of a truncated cone.
11. A spindle motor, comprising:
a rotating shaft;
a turntable coupled to a rotating shaft to be rotated along therewith, and supporting a disc;
a centering unit fitted over the rotating shaft, and elastically coupled to an inner circumference of the disc; and
a coil spring interposed between the turntable and the centering unit,
wherein an angle between an imaginary line extending along an outer surface of the coil spring and a vertical line parallel to an axial direction of the rotating shaft ranges from 2\xb0 to 12\xb0.
12. The spindle motor as set forth in claim 11, wherein the coil spring includes a first end making contact with the turntable and having a first diameter, and a second end making contact with the centering unit and having a second diameter that is smaller than the first diameter.
13. The spindle motor as set forth in claim 12, wherein the coil spring has a shape of a truncated cone.
14. The spindle motor as set forth in claim 11, wherein the turntable includes a spring support portion to receive an end of the coil spring.
15. The spindle motor as set forth in claim 14, wherein the spring support portion has a shape of an annular recess.
16. The spindle motor as set forth in claim 11, wherein an end of the coil spring making contact with the centering unit is in contact with a spring hanging protrusion that protrudes from a side surface of the centering unit.
17. The spindle motor as set forth in claim 16, wherein the spring hanging protrusion protrudes along the side surface of the centering unit in a ring shape.
18. The spindle motor as set forth in claim 16, wherein the spring hanging protrusion comprises a plurality of spring hanging protrusions protruding from the side surface of the centering unit.
19. The spindle motor as set forth in claim 11, wherein the angle between the imaginary line and the vertical line is 7\xb0.
20. The spindle motor as set forth in claim 11, further comprising:
a base plate;
a stator including a bearing housing coupled to the base plate, a bearing inserted into the bearing housing and rotatably supporting the rotating shaft, a core coupled to an outer circumference of the bearing housing, and a coil coupled to the core; and
a rotor including a yoke coupled to the rotating shaft and supporting the turntable, and a magnet coupled to an inner surface of the yoke and facing the core.

The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.

1. A bioreactor comprising a chamber (100) capable of receiving a liquid media, and a filter assembly (200) comprising a perfusion filter (210; 212; 214), wherein the filter assembly (200) is disposed in the chamber (100) and the filter assembly (200) is free to move within the chamber (100), wherein the filter assembly (200) comprises means for coupling a harvesting flow through said filter (210; 212; 214) and means for coupling a feed flow through said filter in an opposite direction compared to the harvesting flow, wherein the feed flow is pumped to the bioreactor by means of a feed pump (330) and the harvest flow is pumped from the bioreactor by means of a harvest pump (340).
2. The bioreactor assembly of claim 1, wherein the means for coupling the flows comprises a flexible tube attached to the filter assembly.
3. The bioreactor assembly of claim 1, wherein the filter assembly (200) comprises means for coupling the feed flow and the harvesting flow, respectively.
4. The bioreactor assembly of claim 1, wherein the filter assembly (200) comprises means for coupling the feed flow and harvesting flow in a coaxial manner.
5. The bioreactor assembly of claim 4, wherein the feed flow is arranged coaxially around the harvesting flow.
6. The bioreactor assembly of claim 1, wherein the filter assembly comprises at least two filters (211, 212; 213, 214).
7. The bioreactor assembly of claim 6, wherein the feed flow is directed to flow between the at least two filters (211, 212; 213, 214).
8. A method of operating a bioreactor comprising a chamber (100) capable of receiving a liquid media, and a filter assembly (200) comprising a perfusion filter (210; 212; 214), wherein the filter assembly (200) is disposed in the chamber (100) and the filter assembly (200) is free to move within the chamber (100), wherein the method comprises:
removing a harvesting flow through said perfusion filter (210; 212; 214) from the bioreactor by means of a harvest pump (340);
feeding a feed flow through said perfusion filter (210; 212; 214) to the bioreactor by means of a feed pump (330);
wherein the harvesting flow is removed through said perfusion filter (210; 212; 214) in an opposite direction compared to the feed flow.
9. The method of claim 7, wherein the method is carried out in a mode in which a specific volume of the harvesting flow is first removed from the bioreactor (100) and then a substantially equal volume of the feed flow is fed to the bioreactor (100).
10. The method of claim 8, wherein the removal of the harvesting flow and the feeding of the feed flow are performed in periodic intervals.