What is receiver blocking?

This page describes receiver blocking interference basics.It mentions receiver desensitization due to receiver blocking.

The process of reducing the sensitivity of the radio receiver is known as desensitization. In other words, it refers to reduction in strength of the desired signal in the presence of strong off tune signal in comparison to when the interfering signal were absent. This is predominant when the input desired signal is weak in strength. The figure-1 below depicts the same.

Receiver desensitization due to receiver blocking interference

receiver blocking

Usually, receiver blocking specification refers to ability of the receiver to withstand very strong off tune signals which are about 20KHz away from the wanted or desired signal. Often the spacing also can be 100KHz.

When strong signal is present it will take more of the resources and hence there would not be enough power budget to accommodate the weaker desired signals. But when the undesired signal is turned to be off, weaker signals will receive full measure of the power budget.

receiver blocking testing

The typical way to measure receiver blocking behavior or performance is to feed to input signals. The desired signal and another signal at some frequency spacing(i.e. 20 or 100KHz) with much strong signal level are used. The strong signal is increased to the point when blocking de-sensitization causes a 3dB drop in the desired signal output.

Effect of blocking can be minimized to the great extent with the use of front end RF attenuators. Using this overall gain will also be reduced but this results into reduction in overall signal level and hence it will help avoid the desensitization situation.

receiver blocking test procedure

The figure depicts typical set up used in receiver blocking testing. As shown both desired and unwanted signal are combined using power combiner and fed to the DUT(receiver). Refer z-wave conformance testing which mentions receiver blocking test procedure for testing the receiver performance of the z-wave device.

What is difference between

Refer QPSK vs OQPSK vs pi/4QPSK for difference between QPSK, OQPSK and pi/4QPSK modulation types
difference between OFDM and OFDMA
Difference between SC-FDMA and OFDM
Difference between SISO and MIMO
Difference between TDD and FDD

RF and Wireless Terminologies