Digital filter for transmission-end pulse shaping
AssigneeInfineon Technologies AG
InventorElmar Wagner
Life of this patent
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Abstract
The digital filter has a finite impulse response, whose length corresponds at most to the duration of N input values, with the filter emitting an output signal which is n-times oversampled in comparison to the input signal (I, Q). In this case, a means (38.1-38.5) for storage of a plurality of N look-up tables is provided in the filter. n data values are stored per value in each look-up table for a plurality of k possible values of the input signal. Each data value is in this case characteristic of the product of a coefficient of the impulse response and a value of the input signal (I, Q).
Claims25
A digital filter having a finite impulse response, with the length of the impulse response corresponding at most to the duration of N input values, wherein the digital filter:
- receives a digital filter input signal and emits a filter output signal, which is n-times oversampled in comparison to the filter input signal, and
- comprises a means for storage of a plurality N of look-up tables, with n data values being stored per value in each look-up table for a plurality of k possible values of the filter input signal, and each data value being characteristic for the product of
- a coefficient of the impulse response and
- a value of the input signal or a value which is dependent on this value of the input signal,
- wherein the output signal is formed from the data values.
An I/Q modulator, comprising
- a first filter for pulse shaping of signals in the I path of the I/Q modulator, and
- a second filter for pulse shaping of signals in the Q path of the I/Q modulator,
- wherein the first and second filter each are digital filters having a finite impulse response, with the length of the impulse response corresponding at most to the duration of N input values, wherein each digital filter:
- receives a digital filter input signal and emits a filter output signal, which is n-times oversampled in comparison to the filter input signal, and
- comprises a means for storage of a plurality N of look-up tables, with n data values being stored per value in each look-up table for a plurality of k possible values of the filter input signal, and each data value being characteristic for the product of
- a coefficient of the impulse response and
- a value of the input signal or a value which is dependent on this value of the input signal,
- wherein the output signal is formed from the data values.
A filter method having a finite impulse response, with the length of the impulse response corresponding at most to the duration of N input values, the method comprising the steps of:
- emitting a filter output signal for a digital filter input signal, which filter output signal is n-times oversampled in comparison to the filter input signal, and
- reading out a plurality of N stored look-up tables for filtering the digital filter input signal, with n data values being stored per value in each look-up table for a plurality of k possible values of the filter input signal, and each data value being characteristic for the product of
- a coefficient of the impulse response and
- a value of the input signal or a value which is dependent on this value of the input signal, and
- forming the output signal from the data values.
Dependencies are inferred from the claim text.