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Active RC (Resistance-Capacitance) filter bandwidth calibration method

A technology of filter bandwidth and calibration method, applied in the direction of output stability, electrical components, etc., to improve the efficiency of detection and correction

Active Publication Date: 2011-07-20
GUANGZHOU RUNXIN INFORMATION TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Since the on-chip resistors and capacitors generally have a deviation of 10% to 25%, the corner frequency affecting the filter is as high as ±50%.

Method used

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  • Active RC (Resistance-Capacitance) filter bandwidth calibration method
  • Active RC (Resistance-Capacitance) filter bandwidth calibration method
  • Active RC (Resistance-Capacitance) filter bandwidth calibration method

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Embodiment Construction

[0027] The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0028] Such as Figure 1 to Figure 3 As shown, a method for calibrating the bandwidth of an active RC filter according to the present invention includes an active RC filter 101, the filter output is a fixed-frequency square wave signal, and the frequency of the square wave signal is inversely proportional to the RC resistance and capacitance. Adjust the size of RC to change the filter output square wave frequency 103 is calculated as follows:

[0029] ,(1)

[0030] The output square wave signal period, that is, the pulse width is: (m is a constant), (2)

[0031] From the formula (1), we can see that, is inversely proportional to the RC constant, so that the measurement of the RC constant is transformed into the Measurement.

[0032] said Measurement module 102, the higher frequency used in its digital circ...

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Abstract

The invention discloses an active RC (Resistance-Capacitance) filter bandwidth calibration method. An RC filter and a measurement module are provided in the method, wherein the output of the filter is a square wave signal with a fixed frequency, and the measurement on an RC constant is converted into the measurement on a reference value; the measurement module is used for converting the measurement on the RC value into a reference value of a clock counting of which the frequency is disclosed in the specification in a pulse width; a mode of increasing capacitor arrays is adopted, and a counting value N is proximal through regulating the capacitor arrays; and an offset factor alpha is calculated, and through changing the capacitance arrays, the current RC constant is multiplied by a coefficient 1 / alpha to calibrate the corner frequency of the filter to a design value. In the invention, the RC constant is measured and calibrated by adopting the circuit structure through frequency measurement, so that the active RC filter bandwidth can be calibrated. The method can be better applied to the automatic calibration of the filter bandwidth of the active RC filter.

Description

technical field [0001] The invention relates to a method for adjusting the bandwidth of an RC filter based on frequency measurement technology. The purpose of changing the bandwidth of the filter is achieved by measuring and detecting the frequency and adjusting the capacitance RC constant. Numerical size and correction of the RC constant. Background technique [0002] At present, in the active RC filter, the change of R (resistance) and C (capacitance) will be caused by the change of PVT (process, voltage, temperature), which will affect the change of the corner frequency of the filter and change the frequency characteristics of the filter , so it is necessary to measure and correct the frequency characteristics of the filter to overcome the influence of PVT changes. In an active filter, its frequency characteristics are inversely proportional to the product of RC resistance and capacitance. For a fixed output frequency, the RC constant in the circuit should be constant, s...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03L1/00
Inventor 李正平方敏黄伟朝刘松艳
Owner GUANGZHOU RUNXIN INFORMATION TECH
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