Implementation structure of fractional delay digital filter

Abstract

The invention provides an implementation structure of a fractional delay digital filter. By factorizing odd term and even term of independent variable z in the frequency response function of the fractional delay digital filter, a high-level fractional delay digital filter operation can be factorized into two low-level fractional delay digital filter operations and one complex multiplication operation, thus the variation range of the target fitting curve which takes the delay parameter as the independent variable can be narrowed, the curve fitting orders can be lowered, the number of taps of the filter can be decreased, and hardware resources required for realizing the fractional delay digital filter can be reduced on the premise of not reducing the delay precision.

Description

technical field [0001] The invention relates to the field of digital signal processing, in particular to a realization structure of a fractional delay digital filter. Background technique [0002] The fractional delay digital filter is a digital filter whose delay is a non-integer number of samples. It is widely used in modern digital signal processing, and is commonly used in technical fields such as digital communication, array signal processing, speech coding and synthesis, time delay estimation, and sampling rate conversion. . [0003] Fractional delay digital filters have a variety of implementation structures, the most widely used of which is the patent titled "CONTINUOUSLY VARIABLE DIGITAL DELAY CIRCUIT" (continuously variable digital delay circuit) published by C.W.Farrow on September 12, 1989. The patent number is A realization structure of a digital filter that can realize a continuously variable delay is proposed in US Patent 4866647. This architecture uses conv...

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Problems solved by technology

[0004] The delay accuracy of the Farrow structure mainly depends on the order of polynomial fitting. In some technologies that require high delay accuracy, such as digital delay beamforming technology that is widely used in radar, sonar, medical imaging and other fields , the delay accuracy is usually on the order of picoseconds, which requires the Farrow structure to adopt a higher fitting order, thereby increasing the number of filter taps in the Farrow structure, so that the Farrow structure needs to consume more resources

[0005] After searching the existing technical literature, it is found that the patent number is 98804591.5, and the patent name is "Fractional Delay Digital Filter". This patent proposes a digital signal processing device that realizes fractional delay operation in the case of linear processing. A dedicated channel carries out selective amplitude emphasis and phase shifting, and a shared channel carries out inverse amplitude emphasis on the mentioned selected amplitude emphasis, so as to achieve the purpose of reducing the required calculation load under the same processing accuracy. The disadvantage is that this method It is a linear processing method, which cannot be applied to signal processing systems that require continuous variable delay

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