Coded data generation or conversion – Converter compensation
Reexamination Certificate
2003-02-25
2004-12-28
Wamsley, Patrick (Department: 2819)
Coded data generation or conversion
Converter compensation
C341S120000
Reexamination Certificate
active
06836227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a digitizer module, a waveform generating module, a converting method, a waveform generating method and a recording medium for recording a program thereof. More particularly, the present invention relates to a digitizer module for converting a pair of analog signals into a pair of digital signals with equal sample timing, a waveform generating module for outputting a pair of synchronous analog signals and a program and a method of process thereof.
2. Description of the Related Art
As known in the art, with regard to a digitizer module for sampling a pair of analog signals such as quadrature modulated signals to be synchronized each other, there has been a problem that if sampling timings of a pair of AD converters sampling a pair of analog signals do not match each other, quality of observed signals is lowered due to an impairment of orthogonality regarding a result of measuring the two analog signals originally in quadrature.
And also, with regard to a waveform generating module for converting a pair of digital signals to be synchronized each other into analog signals respectively and outputting the signals, if converting timings of a pair of DA converters converting a pair of digital signals into a pair of analog signals respectively do not match each other, quality of outputted signals is lowered due to a phase difference between a pair of analog signals, which are originally synchronized.
In order to prevent the impairment of quality of signal due to the previous problems, an equal-length routing has been used with respect to a clock signal of a pair of DA converters or a pair of AD converters.
The difference of sample timing or converting timing previously described also results from differences between characteristics of AD converters or DA converters and circuits or routing on other signal trace. Consequently, in order to achieve a digitizer module or a waveform generating module with higher precision, it is desirable to prevent the impairment of quality of signal due to these causes, as well as an equal-length routing with respect to a clock signal.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a digitizer module, a waveform generating module, a converting method, a waveform generating method and a recording medium for recording a program thereof, which are capable of solving the problems above. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to the first aspect of the present invention, a digitizer module for converting a pair of analog signals into a pair of digital signals with equal sample timing, comprises an AD converter for sampling the pair of analog signals at a predetermined time interval and converting into a first and second digital signals respectively, a second signal frequency component calculating unit for calculating a second signal frequency component representing a component of each frequency of the second digital signal on the basis of the second digital signal, a skew frequency component calculating unit for calculating a skew frequency component representing a phase error of each frequency of the second digital signal corresponding to the first digital signal on the basis of a skew of a timing with which the pair of analog signals are sampled by the AD converter and a second signal frequency component correcting unit for correcting the second signal frequency component on the basis of the skew frequency component.
A digitizer module may further comprise a corrected second signal calculating unit for calculating the second digital signal on which the skew has been corrected on the basis of the second signal frequency component, which is corrected.
The second signal frequency component calculating unit may calculate the second signal frequency component by performing a discrete Fourier-transform on the second digital signal, the skew frequency component calculating unit may calculate a correcting function in a frequency domain for correcting the skew with the skew frequency component and the second signal frequency component correcting unit may correct the second signal frequency component by multiplying the second signal frequency component by the correcting function in the frequency domain.
A digitizer module may further comprise a first signal frequency component calculating unit for calculating a first signal frequency component representing a component of each frequency of the first digital signal on the basis of the first digital signal, wherein the second signal frequency component correcting unit may correct the second signal frequency component on the basis of the skew frequency component and the first signal frequency component.
A digitizer module may further comprise a second signal frequency component calculating unit for calculating a first signal frequency component representing a component of each frequency of the first digital signal on the basis of the first digital signal and a first signal frequency component correcting unit for correcting the first signal frequency component on the basis of the skew frequency component.
A digitizer may further comprise a skew measuring unit for measuring the skew on the basis of an amount of a phase difference between the first and second digital signals, in case a same signal as the pair of analog signals is inputted to the AD converter.
According to the second aspect of the present invention, a digitizer module for converting a pair of analog signals into a pair of digital signals with equal sample timing, comprises an AD converter for sampling the pair of analog signals at a predetermined time interval and converting into a first and a second digital signals, a first digital filter for generating a first converted signal into which the first digital signal is converted on the basis of a predetermined filter coefficient, a correcting filter coefficient generator for generating a correcting filter coefficient correcting a skew, besides a waveform of an impulse response of the correcting filter coefficient is same as the first digital filter, on the basis of the skew of a timing with which the pair of analog signals are sampled by the AD converter and a predetermined filter coefficient and a second digital filter for converting the second digital signal on the basis of the correcting filter coefficient and generating a second converted signal on which the skew is corrected.
The correcting filter coefficient generator may make the correcting filter coefficient be h(k·T−&tgr;), in case the predetermined filter coefficient is h(k·T) and the skew is &tgr;, where the first digital filter has at least two the predetermined filter coefficient, k denotes an integer in a range of zero to a number one less than the number of the predetermined filter coefficient and T denotes a sampling interval of the AD converter.
According to the third aspect of the present invention, a waveform generating module for outputting a pair of synchronous analog signals, comprises a first digital signal calculating unit for generating a first digital signal on the basis of a first signal frequency component representing a component of each frequency of a first analog signal, which the waveform generating module should output, a second digital signal calculating unit for generating a second digital signal on the basis of a second signal frequency component representing a component of each frequency of a second analog signal, which the waveform generating module should output, a DA converter for converting the first and second digital signals into the first and second analog signals at a predetermined time interval respectively, a skew frequency component calculating unit for calculating a skew frequency component representing a phase error of each frequency of the second analog signal corresponding to the first analog signal, on the basis of a
Advantest Corporation
Osha & May L.L.P.
Wamsley Patrick
LandOfFree
Digitizer module, a waveform generating module, a converting... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Digitizer module, a waveform generating module, a converting..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digitizer module, a waveform generating module, a converting... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3336529