What is claimed is:
1. A method for synchronizing output of a scanning device with the motion of a scan mechanism within the device, comprising the steps of:
receiving encoder signals indicative of a position of the scan mechanism relative to a scan platen or an object being scanned;
detecting transitions of the encoder signals;
generating scan pulses for triggering a scan operation by a scan element at a desired scan resolution based on the detected transitions of the encoder signals; and
generating a transfer signal controlling output of data from the scan element in synchronization with the scan pulses, accounting for variations in velocity of the scan mechanism.
2. The method of claim 1, wherein the scan mechanism includes a scan bar, and the motion of the scan bar is controlled by a DC motor.
3. The method of claim 1, wherein the steps of receiving, detecting, generating the scan pulses, and generating the transfer signal are performed during a starting portion of the scan operation.
4. The method of claim 1, wherein the steps of receiving, detecting, generating the scan pulses and generating the transfer signal are performed throughout a scan operation.
5. The method of claim 1, wherein the encoder signals include a single channel phase signal.
6. The method of claim 5, wherein the step of detecting includes detecting low to high and high to low transitions of the single channel phase signal.
7. The method of claim 1, wherein the encoder signals include a channel A phase signal and a channel B phase signal.
8. The method of claim 7, wherein the step of detecting includes detecting transitions of the channel A phase signal from low to high and from high to low and detecting transitions of the channel B phase signal from low to high and from high to low.
9. The method of claim 1, wherein the variations of the velocity of the scan mechanism cause variations of the frequency at which the scan pulses are generated.
10. The method of claim 9, wherein the step of generating scan pulse signals includes updating a frequency of scan pulses at each detected transition of the encoder signals.
11. The method of claim 1, wherein the scan operation is triggered from rising edges of the scan pulses.
12. The method of claim 1, wherein the transfer signal transitions between an exposure state and a transfer state, and data is transferred from the scan element when the transfer signal is in the transfer state.
13. The method of claim 12, wherein the transfer signal is low during the exposure state and high during the transfer state.
14. The method of claim 12, wherein the variations of the velocity of the scan mechanism cause variations of the frequency at which the scan pulses are generated, and the step of generating the transfer signal includes varying the duration of the transfer state for the transfer signal in relation to the variations of the frequency at which the scan pulses are generated.
15. The method of claim 1, wherein the step of generating scan pulses includes compensating for a difference in an encoder resolution and the desired scan resolution.
16. The method of claim 1, wherein the scanning device scans data at a high resolution.
17. An apparatus for synchronizing output of a scanning device with the motion of a scan mechanism within the device, comprising:
a scan pulse generator for receiving encoder signals indicative of a position of the scan mechanism relative to a scan platen or an object being scanned, detecting transitions of the encoder signals, and generating scan pulses for triggering a scan operation by the scan element at a desired scan resolution based on the detected transitions of the encoder signals; and
a transfer signal generator for generating a transfer signal for controlling output of data from the scan element in synchronization with the scan pulses, wherein the transfer signal generator accounts for variations in velocity of the scan mechanism.
18. The apparatus of claim 17, wherein the scan mechanism includes a scan bar, and the motion of scan bar is controlled by a DC motor.
19. The apparatus of claim 17, wherein the scan pulse generator receives the encoder signals, detects transitions of the encoder signals, and generates scan pulses and the transfer signal generator generates the transfer signal during a starting portion of the scan operation.
20. The apparatus of claim 17, wherein the scan pulse generator receives the encoder signals, detects transitions of the encoder signals, and generates scan pulses, and the transfer signal generator generates the transfer signal throughout the scan operation.
21. The apparatus of claim 17, wherein the encoder signals include a single channel phase signal.
22. The apparatus of claim 21, wherein the scan pulse generator detects low to high and high to low transitions of the single channel phase signal.
23. The apparatus of claim 17, wherein the encoder signals include a channel A phase signal and a channel B phase signal.
24. The apparatus of claim 23, wherein the scan pulse generator detects transitions of the channel A phase signal from low to high and from high to low and detects transitions of the channel B phase signal from low to high and from high to low.
25. The apparatus of claim 17, wherein the variations of the velocity of the scan mechanism cause variations of the frequency at which scan pulses are generated.
26. The apparatus of claim 25, wherein the scan pulse generator updates a frequency of the scan pulses at each detected transition of the encoder signals.
27. The apparatus of claim 17, wherein the scan operation is triggered from rising edges of the scan pulses.
28. The apparatus of claim 17, wherein the transfer signal transitions between an exposure state and a transfer state, and data is output from the scan element when the transfer signal is in the transfer state.
29. The apparatus of claim 28, wherein the transfer signal is low during the exposure state and high during the transfer state.
30. The apparatus of claim 28, wherein the variations of the velocity of the scan mechanism cause variations of the frequency at which the scan pulses are generated, and the transfer signal generator generates a transfer signal in synchronization with the scan pulses by varying the duration of the transfer state for the transfer signal in relation to the variations of the frequency at which the scan pulses are generated.
31. The apparatus of claim 17, wherein the scan pulse generator compensates for a difference in the encoder resolution and the desired scan resolution in the generation of the scan pulses.
32. The apparatus of claim 17, wherein the scanning device scans data at a high resolution.
33. A method for generating scan pulses for triggering a scan operation, comprising the steps of:
determining a difference between a desired scan resolution and a resolution of encoder signals indicative of a position of the scan mechanism relative to a scan platen or an object being scanned; and
generating scan pulses for triggering a scan operation by a scan element, compensating for differences in the encoder signal resolution and the desired scan resolution.
34. The method of claim 33, wherein if the encoder resolution is less than the desired scan resolution, the difference is compensated for by interpolating between encoder signal transitions to generate the scan pulses.
35. The method of claim 33, wherein if the encoder resolution is greater than the desired scan resolution, the difference is compensated for by generating scan pulses only at some of encoder signal transitions.
36. The method of claim 33, wherein if the encoder resolution is the same as the desired scan resolution, scan pulses are generated at each encoder signal transition.
37. The method of claim 33, wherein variations of the velocity of the scan mechanism cause variations of the frequency at which scan pulses are generated.
38. The method of claim 37, wherein the frequency at which the scan pulses are generated is updated at every encoder signal transition.
39. An apparatus for generating scan pulses for triggering a scan operation, comprising the steps of:
means for determining a difference between a desired scan resolution and a resolution of encoder signals indicative of a position of the scan mechanism relative to a scan platen or an object being scanned; and
means for generating scan pulses for triggering a scan operation by a scan element, compensating for differences in the encoder signal resolution and the desired scan resolution.
40. The apparatus of claim 39, wherein if the encoder signal resolution is less than the desired scan resolution, the difference is compensated for by interpolating between encoder signal transitions to generate the scan pulses.
41. The apparatus of claim 39, wherein if the encoder resolution is greater than the desired scan resolution, the difference is compensated for by generating scan pulses only at some of encoder signal transitions.
42. The apparatus of claim 39, wherein if the encoder resolution is the same as the desired scan resolution, scan pulses are generated at each encoder signal transition.
43. The apparatus of claim 39, wherein variations of the velocity of the scan mechanism cause variations of the frequency at which scan pulses are generated.
44. The apparatus of claim 43, wherein the frequency at which the scan pulses are generated is updated at every encoder signal transition.
45. A method for synchronizing output of a scanning device with the motion of a scan mechanism within the device, comprising the steps of:
receiving scan pulses for triggering a scan operation; and
synchronizing a transfer signal controlling output of data from the scan element with the scan pulses, accounting for variations in velocity of the scan mechanism.
46. The method of claim 45, wherein the transfer signal transitions between an exposure state to a transfer state, and data is transferred from the scan element when the transfer signal is in the transfer state.
47. The method of claim 46, wherein the transfer signal is low during the exposure state and high during the transfer state.
48. The method of claim 46, wherein the variations of the velocity of the scan mechanism cause variations of the frequency of the scan pulses, and the step of synchronizing includes varying the duration of the transfer state for the transfer signal in relation to the variations of the frequency of the scan pulses.
49. The method of claim 48, wherein the step of varying includes decreasing the duration of the transfer state for the transfer signal in proportion to increases in the frequency of the scan pulses until the duration of the transfer state reaches a minimum duration.
50. The method of claim 49, wherein the step of synchronizing further includes accumulating the generated scan pulses when the minimum duration for the transfer state of the transfer signal is reached.
51. The method of claim 50, wherein the scan pulses are accumulated until the frequency of the scan pulses decreases to a predetermined frequency.
52. The method of claim 51, wherein while scan pulses are accumulated, a transfer signal is generated with a transfer state of the minimum duration.
53. The method of claim 45, wherein the step of synchronizing includes maintaining a constant duration for the exposure state of the transfer signal.
54. The method of claim 53, wherein the constant duration for the exposure state corresponds to a constant exposure time for the scanning device.
55. An apparatus for synchronizing output of a scanning device with the motion of a scan mechanism within the device, comprising the steps of:
receiving scan pulses for triggering a scan operation; and
synchronizing a transfer signal controlling output of data from the scan element with the scan pulses, accounting for variations in velocity of the scan mechanism.
56. The apparatus of claim 55, wherein the transfer signal transitions between an exposure state to a transfer state, and data is transferred from the scan element when the transfer signal is in the transfer state.
57. The apparatus of claim 56, wherein the transfer signal is low during the exposure state and high during the transfer state.
58. The apparatus of claim 56, wherein the variations of the velocity of the scan mechanism cause variations of the frequency of the scan pulses, and the step of synchronizing includes varying the duration of the transfer state for the transfer signal in relation to the variations of the frequency of the scan pulses.
59. The apparatus of claim 58, wherein the step of varying includes decreasing the duration of the transfer state for the transfer signal in proportion to increases in the frequency of the scan pulses until the duration of the transfer state reaches a minimum duration.
60. The apparatus of claim 59, wherein the step of synchronizing further includes accumulating the generated scan pulses when the minimum duration for the transfer state of the transfer signal is reached.
61. The apparatus of claim 60, wherein the scan pulses are accumulated until the frequency of the scan pulses decreases to a predetermined frequency.
62. The apparatus of claim 61, wherein while scan pulses are accumulated, a transfer signal is generated with a transfer state of the minimum duration.
63. The apparatus of claim 55, wherein the step of synchronizing includes maintaining a constant duration for the exposure state of the transfer signal.
64. The apparatus of claim 63, wherein the constant duration for the exposure state corresponds to a constant exposure time for the scanning device.
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 method of synchronizing multi-carrier systems, the method comprising:
inserting a predetermined frequency domain signal into a signal on a transmitter side of a multi-carrier system to create a combined signal;
multi-carrier modulating the combined signal, wherein the multi-carrier modulating is an inverse discrete Fourier transform;
transmitting the multi-carrier modulated signal via a carrier channel to a receiving side of the multi-carrier system;
synchronizing the multi-carrier modulated signal by using the predetermined frequency domain signal portion of the transmitted multi-carrier modulated signal, wherein the predetermined frequency domain signal portion is analyzed in a time domain; and
demodulating the synchronized multi-carrier modulated signal by a Fourier transform.
2. The method according to claim 1, wherein the multi-carrier system is one system out of a group consisting of:
Orthogonal Frequency Division Multiplexing (OFDM) systems;
Isotropic Orthogonal Transform Algorithm systems; and
Filtered Multi Tone systems.
3. The method according to claim 1, wherein the predetermined frequency domain signal is a frequency domain pilot signal.
4. The method according to claim 1, further comprising:
performing a coarse timing before the synchronizing by using information of a guard interval.
5. The method according to claim 4, wherein the information of the guard interval is a cyclic prefix.
6. The method according to claim 5, further comprising:
detecting the guard interval by maximizing an energy in a channel.
7. The method according to claim 1, further comprising:
calculating a channel estimation based on the predefined frequency domain signal portion of the transmitted multi-carrier modulated signal.
8. A multi-carrier system, the multi-carrier system comprising:
a unit adapted to insert a predetermined frequency domain signal into a signal on a transmitter side of the multi-carrier system to create a combined signal;
a unit adapted to multi-carrier modulate the combined signal, wherein the multi-carrier modulating is an inverse discrete Fourier transform;
a unit adapted to transmit the transformed signal via a carrier channel to a receiving side of the multi-carrier system;
a unit adapted to synchronize the multi-carrier modulated signal by using the predefined frequency domain signal portion of the transmitted multi-carrier modulated signal, wherein the predetermined frequency domain signal portion is analyzed in a time domain; and
a unit adapted to demodulate the synchronized multi-carrier modulated signal by a Fourier transform.
9. A non-transitory computer-readable medium, in which a computer program is stored which, when being executed by a processor, is adapted to control or carry out a method of synchronizing multi-carrier systems, the method comprising:
inserting a predefined frequency domain signal into a signal on a transmitter side of a multi-carrier system to create a combined signal;
multi-carrier modulating the combined signal, wherein the multi-carrier modulating is an inverse discrete Fourier transform;
transmitting the multi-carrier modulated signal via a carrier channel to a receiving side of the multi-carrier system;
synchronizing the multi-carrier modulated signal by using the predefined frequency domain signal portion of the transmitted multi-carrier modulate signal, wherein the predetermined frequency domain signal portion is analyzed in a time domain; and
demodulating the synchronized multi-carrier modulated signal by a Fourier transform.
10. The method of claim 1, wherein the predetermined frequency domain signal is a frequency domain scatter pilot (SP) signal.
11. The method of claim 1, wherein the predetermined frequency domain signal comprises both frequency domain continuous pilot (CP) and frequency domain scatter pilot (SP) signals.
12. The method of claim 1, wherein the carrier channel is a frequency selective fading channel.
13. The method of claim 1, wherein the synchronizing step uses a scatter pilot (SP) signal in a time domain correlation.
14. The method of claim 1, wherein continuous pilot (CP) signals are treated as noise.
15. The method of claim 1, further comprising:
detecting a scatter pilot (SP) sequence.
16. The method of claim 15, further comprising:
selecting the detected SP sequence that provides a maximum correlation.
17. The method of claim 1, further comprising:
adding a predetermined number of consecutive OFDM symbols in the time domain to obtain a superimposed pilot sequence.
18. The method of claim 1, further comprising:
adding consecutive windows of samples that are equivalent to a predetermined number of consecutive OFDM symbols in the frequency domain.