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Analog power frequency comb notch filter and its adjustment method

A notch filter and analog engineering technology, applied in the direction of electrical components, digital technology networks, impedance networks, etc., can solve the problems of poor power frequency harmonic suppression, cost increase, complex circuit structure, etc., to achieve the suppression of power frequency and its Harmonics, good noise suppression effect, simple circuit structure effect

Active Publication Date: 2017-11-28
JILIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This device can only filter out power frequency harmonics of one frequency, and the filtering effect is affected by the delay accuracy of the delay device. When the delay does not meet the half-cycle condition or delay drift occurs, the power frequency harmonic suppression effect is poor
To sum up, although the existing technology has solved to a certain extent that the attenuation characteristics of the power frequency notch filter are affected by the precision and temperature drift of the resistors and capacitors, it still cannot achieve multi-stop band attenuation, and needs to be filtered out by multi-stage series connection. Power frequency noise of multiple frequencies, complex circuit structure and increased cost

Method used

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  • Analog power frequency comb notch filter and its adjustment method
  • Analog power frequency comb notch filter and its adjustment method
  • Analog power frequency comb notch filter and its adjustment method

Examples

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Embodiment 1

[0074] The following uses an electrocardiogram (ECG) detector as an example for illustration. ECG reflects the electrical changes of the heart during the process of excitation generation, conduction and recovery, and is an objective representation of the electrical activity of the heart. However, because the ECG signal is weak and is detected indoors, it is easily affected by power frequency and its low-order harmonics. interference.

[0075] Set the power frequency and its harmonic frequency to be filtered as 50Hz, 100Hz, 150Hz, 200Hz, 250Hz. at sampling rate f s In the case of 1000Hz, synthesize the power frequency noise signal n(k) and normalize its amplitude:

[0076]

[0077] D(k)=round(32767×n(k)), write 20 data contained in D(k) into the programmable memory, and set the programmable memory to enter the read state after writing. Choose the oscillation frequency f clk It is a 1M Hz crystal oscillator, and the frequency division factor of the frequency divider is se...

Embodiment 2

[0080] The following uses a nuclear magnetic resonance (Magnetic resonance sounding, MRS) water finder as an example for illustration. The MRS water finder uses the artificially excited electromagnetic field to make the hydrogen protons in the groundwater form a macroscopic magnetic moment. This macroscopic magnetic moment produces a precession motion in the electromagnetic field. The coil receives the electromagnetic signal generated by the macroscopic magnetic moment precession to detect the existence of groundwater. . However, because the MRS signal is extremely weak, generally at the nV level, it is easily affected by power frequency harmonics in the surrounding power lines when measuring in the field. The frequency of the MRS signal (Larmor frequency) is related to the strength of the local geomagnetic field, generally 1kHz-3kHz. For example, the Larmor frequency in Changchun City, Jilin Province is 2326Hz. Although the detection circuit of the MRS water finder has added ...

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Abstract

The invention relates to an analog power frequency comb trap and its adjustment method. The power frequency comb trap is connected by an input signal to one input end of a multiplier, and the power frequency noise synthesizer is connected to the other end of the multiplier. The input terminal is connected, the multiplier is connected to the inverting input terminal of the amplifier through a resistor, the inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier through an RC parallel feedback network, and the output and input signals of the operational amplifier are respectively connected to the adder. Consists of two inputs. The invention can effectively suppress the interference of the power frequency and its harmonics in the weak signal detection circuit, and besides filtering out the power frequency noise, it also has a greater attenuation effect on the power frequency harmonics; the circuit structure of the invention is simple, and the attenuation frequency is not affected by the element Due to the influence of device accuracy and temperature, the attenuation frequency can be set through programming, and the attenuation amount and its attenuation bandwidth can also be adjusted to achieve the best noise suppression effect.

Description

technical field [0001] The invention relates to an analog industrial frequency notch filter of a signal detection circuit, in particular to an analog industrial frequency comb notch filter with multiple attenuation frequency bands and adjustable attenuation characteristics and an adjustment method thereof. Background technique [0002] In the field of signal detection, the power frequency (my country's power frequency is 50Hz) and its harmonic electromagnetic field generate electromagnetic interference in the signal detection circuit through electromagnetic induction, which seriously affects the efficiency and accuracy of signal detection, and is the main source of interference in the signal detection circuit. . Adding a power frequency notch filter to the detection circuit can filter out power frequency noise, which is beneficial to improve the signal-to-noise ratio and the anti-interference ability of the circuit, and is widely used in the fields of communication, radar, me...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H03H17/00
Inventor 林君刘立超刘长胜康利利曾新森周海根周逢道史志辉
Owner JILIN UNIV