Tunable Band Stop Filter

Introduction

Bandstop filters (BSF for short) refer to filters that can pass most frequency components, but attenuate certain range of frequency components to a very low level, which is opposite to the concept of bandpass filters. The tunable band stop filter with a very small stopband range and a very high Q factor. And it is composed of low pass and high pass filters in parallel rather than in cascade. The name itself indicates that it will stop a particular band. Because it eliminates frequency, it is also called a notch filter.

Working principle

A band stop filter is formed by a simple lidar circuit with capacitors and inductors in series. At very high and very low frequencies, the band reject filter circuit is like an open circuit, while at intermediate frequencies, the circuit is like a short circuit. Therefore, the circuit only attenuates the IF and allows all other frequencies. The lower and higher cut-off frequencies of the filter depend on the filter design.

It can be obtained by simultaneously applying input voltage to the low-pass filter and the high pass filter, and then adding the output voltages of the two circuits. The cut-off frequency of the low-pass filter shall be less than that of the high pass filter.

Effect

For a tunable band stop filter, it allows signals of a certain frequency band to pass through. This frequency band is not only different from the low frequency signal of the low pass filter, but also different from the high frequency signal of the high pass filter. It is a signal of a certain frequency band in the middle, and the signals, interference and noise below or above this frequency band are suppressed. It is equivalent to a series connection of high pass and low pass. The high and low pass are filtered out and the middle band is reserved.

Characteristic

The ideal band stop filter has zero gain in the stopband. The relationship between the central frequency f0 of the band-stop filter and the suppression bandwidth BW is as follows: Q is the quality factor fH is the upper limit frequency of the filter, fL is the lower limit frequency of the filter, where fH ＞ fL. The narrower the bandwidth BW, the higher the quality factor Q.

Application

In different technologies, these filters are used in different fields.

1. In telephone technology, these filters are used as telephone line noise reducers and DSL Internet services, which will help eliminate interference on the line that will reduce DSL performance.

2. Widely used in electric guitar amplifiers. In fact, this electric guitar will produce a "buzz" of 60Hz. This tunable band stop filter is used to reduce hum to amplify the signal generated by the guitar amplifier and make the best equipment. These are also used in some acoustic applications, such as mandolin and basic instrument amplifiers.

3. In the communication electronic equipment, the signal is distorted due to some noises (harmonics), which will cause the original signal to interfere with other signals, resulting in output errors. Therefore, these filters are used to eliminate these unwanted harmonics.

4. It is used to reduce static electricity in the radio.

5. These are also used for optical communication technology. There may be some interference (stray) optical frequencies at the end of the optical fiber, which will cause beam distortion. These distortions are eliminated by a filter band stop. The best example is Raman spectroscopy.

5. In image and signal processing, these filters are very suitable for suppressing noise.

6,. These are used for high-quality audio applications such as PA systems (public address systems).

7. These are also used for medical applications, that is, to eliminate line noise in biomedical instruments such as EGC.

Packaging

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Delivery

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Our service

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