Every Application of a Band Reject Filter That You Need You Know About


With each day, technology keeps on developing in various regions around the world. This is mostly with respect to electronic and radio frequency equipment, which finds a lot of applications in almost all the work sectors. A type of device that is commonly utilized in association with RF equipment is the band reject filter. These filters mainly comprise a low-pass and high-pass filters that are set along with a parallel connection

What is a band stop filter? 

A band stop filter is a device that enables the passage of various frequencies but rejects particular ones. Due to this feature, it is also called a band elimination filter or notch filter (Circuits Today, Band Stop Filter, 2011). The device is designed in a manner that allows the frequencies to pass above and below a particular range. This entirely depends on the components used in the band stop filter circuit design of the device. Any of the frequencies between the two cut-off ranges are attenuated.

The businesses that want to invest in these devices need to know some important details such as configurations, applications, cost, types, etc. The following points explain the crucial factors of the reject filters.

Configurations of band reject filter

A  band reject filter has a certain set of configurations that make it unique. Depending on their needs, companies can select the configurations mentioned below.  

  • Lumped Component – It is made for frequencies that fall below 150 MHz. It is also suitable for 10% to 30 or 40% bandwidth notches 
  • Helical Resonator – It is made for frequencies that fall in the range of 30 to 400 MHz. This is also suitable for 0.5% to 5% narrow bandwidth notches
  • Coaxial Resonator –  It is made for frequencies that range in 400 to 3,000 MHz.

It is also used for 0.5% to 5% narrow bandwidth applications

Band Reject Filter Applications

Listed below are some of the top band stop filter applications that companies should know about. 

  1. The filter is used mainly in public address systems and speaker systems for ensuring good quality audio. 
  2. The devices are a crucial part of telephone technology, as they are used as line noise reducers in case of signal transmission.
  3. In DSL and other internet services, it is important to reduce unnecessary interference as much as possible. The bandstop filters are utilized for this purpose.
  4. Radio signals are used for a variety of purposes and are a common communication device. The filters are needed to decrease the static on the radio devices, for enabling clear communications.
  5. Guitar amplifiers are devices similar to PA speaker systems. They are used as an output sound source from musical instruments. The band reject filters are used in such amplifiers to reduce a specific humming sound that may occur after the instruments are plugged.
  6. Other than radios, PA’s and amplifiers, the filters are incorporated in many other electronic communication devices to decrease a specific interference range called ‘noise’ in the form of harmonics. In this manner, there are lesser chances for errors to occur in the output. Unwanted harmonics need to be weeded out for clear communications.
  7. In the medical field, machines like the electrocardiogram (ECG) machine incorporates the use of reject filters for hassle free operations.
  8. The reject filters are an important part of image and signal processing units.
  9. Optical communication technologies use optic fibres in order to process light transmissions. In such technologies, distortions in the light pathway may occur. To avoid this, band stop filters are excellent ways of achieving clear light transmission.

Apart from band reject filters, a tunable notch filter is a similar device which allows the user to switch between different frequencies for a variety of electronic processes. Before businesses invest in such devices, they should consider factors such as cost, availability, material quality, company brand, etc.