Coded data generation or conversion – Analog to or from digital conversion – Differential encoder and/or decoder
Reexamination Certificate
1999-06-29
2001-02-20
Tokar, Michael (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Differential encoder and/or decoder
C341S123000
Reexamination Certificate
active
06191718
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an information signal processing technique and, more specifically, to a data sampling method and device for converting an analog input signal to a digital output signal by using an A/D (analog-to-digital) sampling frequency.
2. Description of the Prior Art
In recent years, the technology relating to mobile communication terminals has made great progress. As a result, mobile communication terminals having various communication functions such as a function of communicating various data including audio data, facsimile data, and personal computer (PC) data have been developed. To implement such communication functions, it is indispensable to incorporate, in a mobile communication terminal, an A/D conversion function for converting an analog signal to a digital signal. The A/D conversion is realized in such a manner that a digital signal is generated by sampling an analog signal according to an A/D sampling frequency. Techniques relating to this type of sampling are disclosed in Japanese Patent Application Laid-Open Nos. 6-313764, 9-83588, 9-135149, 9-321632, 8-4591, etc.
One problem that arises in incorporating various communication functions as described above in mobile communication terminals is that various data to be handled have different frequencies. As is well known, in mobile communication terminals, output signals should have the same frequency even if input signals have different frequencies. However, in the A/D conversion method in which a digital signal is generated by merely sampling an analog signal according to a sampling frequency, output signals have different frequencies when input signals have different frequencies. Although various A/D conversion techniques have been proposed to solve this problem, all of them are complex in configuration and hence are difficult to implement.
SUMMARY OF THE INVENTION
An object of the invention is therefore to provide a data sampling method and device which make it possible, with a simple configuration, to give a prescribed frequency to output signals even if input signals have different frequencies.
Another object of the invention is to provide a data sampling method and device which make it possible to perform delay adjustments on a data string digitally.
According to the present invention, a data sampling method for an A/D (analog-to-digital) conversion from an analog input signal to a digital output signal, includes the steps of: a) converting the analog input signal to digital data by sampling the analog input signal at a sampling frequency fs that is N times an A/D sampling frequency that is necessary for the A/D conversion, where N is an integer; b) decimating the digital data at a ratio of 1/N to produce N decimated data strings; and c) producing the digital output signal based on the N decimated data strings.
The sampling frequency fs may be adjusted based on the N decimated data strings. Preferably, a decimated data string is selected from the N decimated data strings by comparing data error rates thereof. The sampling frequency fs is adjusted depending on a deviation of a selected decimated data string from a predetermined data string of the N decimated data strings.
The step b) may comprise the steps of: b-1) generating N clock signals which have 1/N the sampling frequency fs and are delayed in order by 1/fs; and b-2) distributing the digital data using the N clock signals to produce the N decimated data strings.
A frequency of each of the N decimated data strings may be set to a baseband frequency so as to demodulating the analog input signal.
According to another aspect of the present invention, a data sampling method includes the steps of: a) converting the analog input signal to digital data by sampling the analog input signal at a sampling frequency fs that is N times an A/D sampling frequency that is necessary for the A/D conversion, where N is an integer and is determined depending on a frequency of the analog input signal; b) generating N clock signals which have 1/N the sampling frequency fs and are delayed in order by 1/fs; c) decimating the digital data using two clock signals selected from the N clock signals to produce two decimated data strings, wherein a frequency of each of the N decimated data strings is set to a baseband frequency and one of the two clock signals is delayed from the other by &pgr;/2; and d) combining the two decimated data strings to produce the digital output signal as a quadrature-demodulated signal.
REFERENCES:
patent: 5408235 (1995-04-01), Doyle et al.
patent: 5818882 (1998-10-01), Komatsu
patent: 5963160 (1999-10-01), Wilson et al.
patent: 6-313764 (1994-11-01), None
patent: 8-4591 (1996-01-01), None
patent: 9-83588 (1997-03-01), None
patent: 9-135149 (1997-05-01), None
patent: 9-321632 (1997-12-01), None
NEC Corporaton
Scully Scott Murphy & Presser
Tokar Michael
Tran Anh
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