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RF Blocker types | In Band Blocker, Out of Band Blocker

This page on the RF Blocker describes types of RF blockers viz. In Band Blocker and Out of Band Blocker. It mentions difference between In Band Blocker and Out of Band Blocker with diagram.

Introduction: The device used to block or supress RF signal is known as RF blocker or RF jammer. It is used to disrupt or block the transmission of particular radio station or satellite station within desired frequency band. As a result of RF signal blockage, the desired wireless signal can not be received or decoded by anyone.

Receiver architectures have been designed to detect and demodulate desired signal and remove unwanted RF blockers. The receiver should take care of elimination of mixer spurious and other undesired products. Receiver use various techniques such as AGC (Automatic gain control) and power detection methods to fulfill above mentioned blockage goals.

What is RF Blocker ?

• Blockers which operate at radio frequencies and have orders of magnitude larger than the desired signal are known as RF blockers.
• Larger blocks can easily jam the receiver.
• Blockers generate frequencies which inter-modulate with others and produce IMD (Inter modulation distortion) products right at the desired signal frequency range.
• There are two types of blockers viz. In band blocker and Out of band blocker. It is easy to filter out-of-band signals and difficult to filter in-band signals.

In band blocker vs Out of band blocker
Figure-1 : In band blocker vs Out of band blocker

In Band Blocker

• The blocker which is close to the desired frequency is known as In band blocker. They are strong carriers which are inside the digital receiving band.
• It creates nonlinear distortion and interferes with weak RF carrier signals.
• In band blockers get mixed in front end part before rf mixer in Direct Conversion Receiver. This produces unwanted product at the baseband.
• In band blockers can only be eliminated at the end of signal chain or in digital domain.

Out of Band Blocker

• The blocker which is far away from the desired frequency is known as out of band blocker. They are strong carriers which are outside of the digital receiving band.
• It creates nonlinear distortion and interferes with weak RF carrier signals.
• Out of band blockers can easily be eliminated using filters as they lie outside the desired frequency band.

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