RF filter, or radio frequency filter, comprises inductors, capacitors, and resistors. These are an imperative component in the wireless technology landscape. The purpose of it is to filter the signal frequency in communication channels. It suppresses unwanted frequency signals and allows signals that meet a specific frequency to pass.
RF filters for wireless communication are governed by frequency, amplitude, wavelength, and phase properties. In addition, the movement and behavior of RF signals are affected by reflection, diffraction, absorption, scattering, free space path loss, gain, and attenuation. These behaviors determine whether the user receives enough RF filters for wireless communication.
There are four RF filters:
- Band stop filter
- Bandpass filter
- Lowpass filter
- High Pass filter
Functioning of Band Stop | Tunable RF Notch Filter
A band-rejection or band-stop filter passes most frequencies unchanged. However, it reduces or weakens those in a specific range. The purpose of the Tunable RF filter is to remove a narrow band of frequencies or a single frequency. It is used in the audio system to remove interfering frequencies like powerline hum. In software-defined radio and radio receivers, it is used to remove a single interfering frequency.
Depending on the design, a notch filter can be either active or passive. An active filter contains amplifying elements like an op-amp, and a passive filter is made of passive elements like capacitors, inductors, and resistors.
A Tunable RF Filter is one whose band-reject frequency range can be tuned or controlled. A tunable RF notch filter or band-reject filter has the characteristic that the band’s center frequency can be set with different values, whether electronically or mechanically.
Some of the tunable Rf notch filters are listed below:
| Name | Application | Type | Bandwidth | Package Type |
| K&L Microwave – D5CTN – 4000/6000-100MHZ-O/O-MQI | Wireless Communications | Digitally Controlled | 100 to 400 MHz | Module with Connectors |
| Ranatec – RI 268 | WiFi, 5G NR, 4G | Digitally Controlled | 5/160 MHz | Rackmount |
| Micro Lambda Wireless, Inc. – MLFR-0218 | Electronic Warfare | YIG Filter | 50 MHz | Module with Connectors |
| K&L Microwave – D5TNF-650/1000-3MHz-N/N-GRI | ATE Labs, Wireless Communications, Military | Digitally Controlled | 15 MHz | Benchtop |
| K&L Microwave – 3TNF-30/76-N/N | ATE Labs, Wireless Communications, Surveillance | Mechanically Controlled | 1 to 2.5 Hz | Benchtop |
| Teledyne Microwave Solutions – F3874 | Electronic Warfare | YIG Filter | 50 to 90 MHz | Module with Connectors |
| Micro Lambda Wireless, Inc. – MLFRD-0206 | Electronic Warfare | YIG Filter | 20 MHz | Module with Connectors |
| Ranatec – RI 266 | Test & Measurement | Digitally Controlled | 5 & 100 MHz | Rackmount |
| WainWright Instruments – WTRCT10-2400-2700-20-40-40M-1 | LTE, TD-SCDMA, CDMA, DECT, Wifi, WLAN, WiMax, 5G N | Digitally Controlled | 20 MHz | Module with Connectors |
| Micro Lambda Wireless, Inc. – MLFR – 0618 | Electronic Warfare | YIG Filter | 25 MHz | Module with Connectors |
Difference between Lowpass filter and Band Pass Filters
Band Pass filters have high-frequency and block unwanted signals in the wireless RF system. These filters have a bandwidth and center frequency and only allow the signals within a specified bandwidth to move through. The signals that are outside of the bandwidth are attenuated. They are widely used in wireless receivers and transmitters.
A lowpass filter (LPF) is a device that allows low-frequency signals to pass through and blocks signals that are above a specific frequency. The difference between a low pass filter and a high pass filter (HPF) is their function. A lowpass filter attenuates content or signals more than its cutoff frequency, and a high-frequency filter attenuates signals below the cutoff frequency.
Industries That Are Primarily Dependent On RF Filters For Wireless Communication
RF notch filters are essential as they control the signal so that the data moves with minimal interference. With the help of Rf filters, the external interference created by neighboring communication systems can be easily blocked.
Additional Read: How Does RF Bandpass Filter Improves Signal Transmission?
RF filters allow global navigation satellite systems, Wi-Fi, public systems, and other bands to co-exist simultaneously. It is among the vital core technologies to address next-generation systems such as telemedicine, intelligent facilities, autonomous vehicles, and other highly connected applications.
Prominent sectors like below listed are largely dependent on RF filters for wireless communication:
- Aerospace
- Drone systems
- Military
- Automatic vehicles
- Satellite
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