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Blocking and Interference Rejection

Written by Robert Lacoste
Signals and Sensitivity In wireless communication, there is always some level of error rate, or at least the chance of some signal error. In this article, Robert revisits the topic of wireless receiver sensitivity, this time looking at how different receivers react differently to electronic perturbances. Topics Discussed How do different receivers react differently to electronic perturbances How does sensitivity work in wireless commsWhat is co-channel interference?What is adjacent channel interference?How does blocking work?An example using the Analog Device's ADF7030-1 Tech Used ADF7030-1 sub-GHz transceiver from Analog Devices Welcome to “The Darker Side.” I previously devoted a column to wireless receiver sensitivity: “Long-range RF for the IoT-Part 1” (Circuit Cellar 313, August 2016). This month, I am returning to this topic and to explain why knowing the sensitivity of a receiver is not enough. Specifically, I will explain why receivers are not equal when some electronic perturbances are around, and for sure there will be some. As usual, I will not use any complicated math. So, stay cool and enjoy! SENSITIVITY First, let’s come back to sensitivity. Imagine that you have a wireless link between two devices—a transmitter and a receiver some distance away. It could be any kind of wireless link, such as Wi-Fi, Bluetooth, LoRa, cellular or anything else. The transmitter is sending a message, which is a given sequence of bits, and the receiver does its best to receive these bits. If the receiver is close to the transmitter, then the received signal power is high, and the bits are recovered nearly without any error (Figure 1, Case 1). The so-called “bit error rate” (BER), which is simply the number of bits in error divided by the total number of bits transmitted, will be close to 0%. It’s important to know that the number of errors is never zero. It could be very close, but in any transmission, there will always
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Blocking and Interference Rejection

by Circuit Cellar Staff time to read: 10 min