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Method for designing adjustable frequency domain filter based on smooth curve

A filter design, smooth curve technology, applied in color TV parts, TV system parts, TV and other directions, can solve the problem of no filter, larger cutoff frequency fluctuation, ringing and other problems, to achieve robustness Strong, enhance the effect of image quality

Active Publication Date: 2010-08-11
BEIJING DAYANG TECH DEV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, when the filter designed by the window function method is used for image down-sampling filtering, there are many deficiencies: there is oscillation behavior near the discontinuity point of the ideal frequency response, and the passband cut-off frequency ω cannot be specified precisely p and the stopband cutoff frequency ω s , it may need repeated verifications to determine the ideal window type and size, because the fluctuations in the passband and stopband are not uniform, and the closer to the cutoff frequency, the greater the fluctuation, resulting in "overshoot" and "vibration" in the filtered image. bell phenomenon
In addition, a low-pass filter with complete technical indicators needs to specify the passband cut-off frequency ω p , stopband cut-off frequency ω s , passband fluctuation coefficient σ 1 , stop band fluctuation coefficient σ 2 , but there is no standard filter specification for HD / SD down-conversion or arbitrary scale down-conversion of video

Method used

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  • Method for designing adjustable frequency domain filter based on smooth curve
  • Method for designing adjustable frequency domain filter based on smooth curve
  • Method for designing adjustable frequency domain filter based on smooth curve

Examples

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Embodiment 1

[0025] This embodiment is an adjustable smooth curve-based frequency domain filter design method. In this embodiment, the pass-band cut-off frequency and the stop-band cut-off frequency are adaptively calculated by changing the sampling rate of the signal, and then, between the pass-band and the stop-band, a transition band is generated by smooth curve fitting, which solves the problem of the distribution of sample points in the transition band. On this basis, the frequency response is designed and generated, and finally the frequency response is sampled at equal intervals in the frequency domain to obtain the final frequency domain filter. The frequency response of the filter is plotted as figure 2 As shown, the curve is defined piecewise. where the x-axis is the frequency axis, the y-axis is the amplitude axis, and ω p is the passband cutoff frequency, ω s is the stopband cutoff frequency, in the interval [0, ω p ) is called the passband, [ω p , ω s ) is called the tr...

Embodiment 2

[0035] This embodiment is an improvement of the first embodiment, and is a refinement of the step of calculating the cutoff frequency in the first embodiment. The source signal and the target signal in the step of calculating the cutoff frequency described in this embodiment include: a video image signal and an audio digital signal.

[0036] In fact, the filter designed in the present invention can generate a one-dimensional filter, can also generate a two-dimensional filter, and can even generate an n-dimensional filter by extension. Without loss of generality, when the present invention is used to generate an n-dimensional filter, the frequency responses corresponding to n different directions (dimensions) are all generated by the steps described in the first embodiment. While the audio signal is actually a one-dimensional signal, the video image signal is actually a two-dimensional signal. As long as the pass-band cut-off frequency and the stop-band cut-off frequency are c...

Embodiment 3

[0038] This embodiment is an improvement of the first embodiment, and is a refinement of the step of initializing the smooth curve in the first embodiment. The smooth curve in the step of initializing the smooth curve in this embodiment includes: an ellipse and a parabola.

[0039] In fact, a smooth curve between the passband cutoff frequency and the stopband cutoff frequency can be fitted with a variety of curves. Simpler curves are elliptic lines and parabolas, using elliptic line fitting to generate transition bands such as Figure 4 shown. The following example illustrates the process of using an ellipse to fit the transition zone. The ellipse equation is expressed as

[0040] x 2 a 2 + y 2 b 2 = 1 - - - ( 1 ) ...

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Abstract

The invention relates to a method for designing an adjustable frequency domain filter based on a smooth curve, which is used for processing digital signals. The method comprises the following steps: calculating cut-off frequency; calculating pass-band cut-off frequency and stop-band cut-off frequency; initiating the smooth curve; generating frequency response; and adjusting the smooth curve to correct and optimize a filter to obtain the frequency domain filter. The invention adaptively calculates the pass-band cut-off frequency and stop-band cut-off frequency by signal variable sampling rate,adopting the smooth curve to generate a transition band between the pass band and the stop band in a fit manner, solves the distribution problem of transition band sample points by using adjustability and smoothness of the curve, designs and generates the frequency response on the basis, and finally obtains the frequency domain filter by sampling frequency responses at equal intervals in the frequency domain.

Description

technical field [0001] The invention relates to an adjustable smooth curve-based frequency domain filter design method, which is a digital signal processing method and a low-pass filter design method. Background technique [0002] Filter design is one of the core issues of signal processing. Generally speaking, the filter has the function of frequency selection, and its purpose is to suppress certain frequency components in the input signal, thereby changing the relative proportion of each frequency component in the signal spectrum. According to the nature of the signal processed by the filter, it can be divided into analog filter and digital filter. Digital filters include finite impulse response (FIR, Finite Impulse Response) filters and infinite impulse response (IIR, Infinite Impulse Response) filters. Compared with the latter, the former has outstanding advantages: the system is always stable, easy to achieve linear phase, and no obvious phase distortion occurs in vid...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04N5/14H04N5/21
Inventor 姚威邓伟王雨曾国卿谷显峰边宏昌
Owner BEIJING DAYANG TECH DEV
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