1. A method for reducing a Peak to Average Power Ratio (\u201cPAPR\u201d) of an Orthogonal Frequency Division Multiplexing (\u201cOFDM\u201d) signal, comprising:
routing said OFDM signal to first and second signal processing paths;
time delaying said OFDM signal traveling along said first signal processing path;
using a digital filter and said OFDM signal to determine a threshold value;
determining whether an instantaneous signal magnitude value of said OFDM signal traveling along said second signal processing path is greater than said threshold value, exclusively when said digital filter has a steady state behavior;
if it is determined that said instantaneous signal magnitude value is greater than said threshold value, scaling a magnitude of at least a first complex symbol sample of said OFDM signal which has been time delayed to a level that precludes a power amplifier from entering a non-linear region of operation; and
if it is determined that said instantaneous signal magnitude value is not greater than said threshold value, outputting said complex symbol sample of said OFDM signal which has been time delayed without modification to said magnitude thereof.
2. The method according to claim 1, wherein said OFDM signal is a baseband OFDM signal and said scaling is performed at baseband.
3. The method according to claim 1, wherein said OFDM signal is a baseband OFDM signal and said scaling is performed at an intermediate frequency.
4. The method according to claim 1, further comprising scaling magnitudes of a plurality of second complex symbol samples of said OFDM signal which immediately precede or succeed said first complex symbol sample.
5. The method according to claim 4, wherein said magnitudes of said first and second complex symbol samples are scaled by different amounts.
6. A method for reducing a Peak to Average Power Ratio (\u201cPAPR\u201d) of an Orthogonal Frequency Division Multiplexing (\u201cOFDM\u201d) signal, comprising:
routing said OFDM signal to first and second signal processing paths;
time delaying said OFDM signal traveling along said first signal processing path;
determining whether an instantaneous signal magnitude value of said OFDM signal traveling along said second signal processing path is greater than a threshold value;
if it is determined that said instantaneous signal magnitude value is greater than said threshold value, scaling a magnitude of at least a first complex symbol sample of said OFDM signal which has been time delayed to a level that precludes a power amplifier from entering a non-linear region of operation;
if it is determined that said instantaneous signal magnitude value is not greater than said threshold value, outputting said complex symbol sample of said OFDM signal which has been time delayed without modification to said magnitude thereof; and
determining said threshold value by:
calculating a power value using said instantaneous signal magnitude value;
computing an average signal power value using said power value;
multiplying a maximum PAPR by said average signal power value to yield an allowed peak power; and
calculating a square root of said allowed peak power to obtain a maximum allowable signal magnitude, where said maximum allowable signal magnitude comprises said threshold value.
7. The method according to claim 6, wherein said average signal power value is computed using a digital filter.
8. The method according to claim 7, wherein said determining step is performed exclusively when said digital filter has a steady state behavior.
9. A method for reducing a Peak to Average Power Ratio (\u201cPAPR\u201d) of an Orthogonal Frequency Division Multiplexing (\u201cOFDM\u201d) signal, comprising:
routing said OFDM signal to first and second signal processing paths;
time delaying said OFDM signal traveling along said first signal processing path;
determining whether an instantaneous signal magnitude value of said OFDM signal traveling along said second signal processing path is greater than a threshold value;
if it is determined that said instantaneous signal magnitude value is greater than said threshold value, scaling a magnitude of at least a first complex symbol sample of said OFDM signal which has been time delayed to a level that precludes a power amplifier from entering a non-linear region of operation;
if it is determined that said instantaneous signal magnitude value is not greater than said threshold value, outputting said complex symbol sample of said OFDM signal which has been time delayed without modification to said magnitude thereof; and
determining said threshold value by:
computing an average signal magnitude using said instantaneous signal magnitude value;
multiplying said average signal magnitude by a maximum magnitude ratio to yield an allowable peak magnitude, where said allowable peak magnitude comprises said threshold value.
10. The method according to claim 9, wherein said average signal magnitude is computed using a digital filter.
11. The method according to claim 10, wherein said determining step is performed exclusively when said digital filter has a steady state behavior.
12. A system, comprising:
at least one electronic circuit configured to:
route an OFDM signal to first and second signal processing paths;
time delay said OFDM signal traveling along said first signal processing path;
using a digital filter and said OFDM signal to determine a threshold value;
determine whether an instantaneous signal magnitude value of said OFDM signal traveling along said second signal processing path is greater than said threshold value, exclusively when said digital filter has a steady state behavior;
if it is determined that said instantaneous signal magnitude value is greater than said threshold value, scale a magnitude of at least a first complex symbol sample of said OFDM signal which has been time delayed to a level that precludes a power amplifier from entering a non-linear region of operation; and
if it is determined that said instantaneous signal magnitude value is not greater than said threshold value, output said complex symbol sample of said OFDM signal which has been time delayed without modification to said magnitude thereof.
13. The system according to claim 12, wherein said OFDM signal is a baseband OFDM signal and said scaling is performed at baseband.
14. The system according to claim 12, wherein said OFDM signal is a baseband OFDM signal and said scaling is performed at an intermediate frequency.
15. The system according to claim 12, wherein the electronic circuit is further configured to scale magnitudes of a plurality of second complex symbol samples of said OFDM signal which immediately precede or succeed said first complex symbol sample.
16. The system according to claim 15, wherein said magnitudes of said first and second complex symbol samples are scaled by different amounts so as to prevent large instantaneous amplitude changes of said OFDM signal.
17. A system, comprising:
at least one electronic circuit configured to:
route an OFDM signal to first and second signal processing paths;
time delay said OFDM signal traveling along said first signal processing path;
determine whether an instantaneous signal magnitude value of said OFDM signal traveling along said second signal processing path is greater than a threshold value;
if it is determined that said instantaneous signal magnitude value is greater than said threshold value, scale a magnitude of at least a first complex symbol sample of said OFDM signal which has been time delayed to a level that precludes a power amplifier from entering a non-linear region of operation; and
if it is determined that said instantaneous signal magnitude value is not greater than said threshold value, output said complex symbol sample of said OFDM signal which has been time delayed without modification to said magnitude thereof;
wherein said electronic circuit is further configured to determine said threshold value by:
calculating a power value using said instantaneous signal magnitude value;
computing an average signal power value using said power value;
multiplying a maximum PAPR by said average signal power value to yield an allowed peak power; and
calculating a square root of said allowed peak power to obtain a maximum allowable signal magnitude, where said maximum allowable signal magnitude comprises said threshold value.
18. The system according to claim 17, wherein said average signal power value is computed using a digital filter.
19. The system according to claim 18, wherein said determination as to whether said instantaneous signal magnitude value is greater than said threshold value is made exclusively when said digital filter has a steady state behavior.
20. A system, comprising:
at least one electronic circuit configured to:
route an OFDM signal to first and second signal processing paths;
time delay said OFDM signal traveling along said first signal processing path;
determine whether an instantaneous signal magnitude value of said OFDM signal traveling along said second signal processing path is greater than a threshold value;
if it is determined that said instantaneous signal magnitude value is greater than said threshold value, scale a magnitude of at least a first complex symbol sample of said OFDM signal which has been time delayed to a level that precludes a power amplifier from entering a non-linear region of operation; and
if it is determined that said instantaneous signal magnitude value is not greater than said threshold value, output said complex symbol sample of said OFDM signal which has been time delayed without modification to said magnitude thereof;
wherein said electronic circuit is further configured to determine said threshold value by:
computing an average signal magnitude using said instantaneous signal magnitude value;
multiplying said average signal magnitude by a maximum magnitude ratio to yield an allowable peak magnitude, where said allowable peak magnitude comprises said threshold value.
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 arrangement, comprising:
an electric motor, comprising:
a stator, and
a motor rotor;
a pump, driven by the electric motor; and
a plurality of flow guiding elements,
wherein a process fluid is moved by the pump to a higher pressure,
wherein the motor rotor is rotatable around a rotation axis,
wherein the stator surrounds the motor rotor at least partially circumferentially,
wherein a gap extends circumferentially between the motor rotor and the stator,
wherein a flow path is provided, along which at least a part of the process fluid is directed in an axial direction,
wherein the gap belongs to the flow path,
wherein in the flow path the plurality of flow guiding elements are provided in order to avoid a flow in the circumferential direction of rotor rotation in the gap, and
wherein the plurality of flow guiding elements are guide vanes installed in the flow path upstream the gap and which are shaped to generated a counter swirl to the direction of rotor rotation before the process fluid enters the gap.
2. The arrangement as claimed in claim 1, wherein a surface of the stator adjoining the gap is provided with the plurality of flow guiding elements.
3. The arrangement as claimed in claim 2, wherein the surface is provided with a plurality of longitudinal grooves extending along the rotation axis.
4. The arrangement as claimed in claim 2,
wherein the surface is provided with a plurality of grooves of a helical shape, and
wherein the helix is left handed for a right turning rotor and right handed for a left turning rotor.
5. The arrangement as claimed in claim 1, wherein the electric motor and the pump are enclosed by a common gas tight casing, which is provided with an inlet and an outlet for the process fluid.
6. The arrangement as claimed in claim 1, wherein the stator includes a dedicated cooling system, which is separated from the gap by an adjoining partition wall.
7. The arrangement as claimed in claim 6, wherein the adjoining partition wall is of a cylindrical shape.