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15 | In some cases, filters—usually bandpass filters—are also placed after an LNA in the receiver chain to protect and prevent the amplification of out-of-band signals. Another method of protecting sensitive receiver electronics is using a variable attenuator, such as a digital step attenuator (DSA), before the LNA in a receiver chain. The DSA can use signal-power- monitoring circuitry to determine the level of attenuation needed to ensure the signal energy in the receive path does not exceed the desired threshold. The challenge associated with using receiver protection circuitry is that any component or device before the LNA or receiver circuitry will inevitably result in insertion loss and added noise, increasing the noise floor of the receiver chain. This ultimately results in reduced dynamic range on the low end but may enhance the dynamic range on the high end in the case of filters and variable attenuators. Multiplexers, Circulators, Switches, and Antenna Diversity Many RF systems, including sensing, radio navigation, communication, and imaging applications, rely on both a transmission and reception signal chain, such as radar and transceivers, for communication. With purely passive systems, only a receiver is needed to pick up ambient and reflected signals generated by other sources. However, other systems require a method that prevents the higher- power transmission signal energy from being coupled into the receiver signal chain. If the transmitter signal energy is low enough, the receiver may just be desensitized during transmission, but a high enough transmitter signal energy and coupling could damage a receiver chain. This is a problem if the transmitter and receiver share the same antenna or if the transmitter and receiver antennas need to be in proximity or are omnidirectional. To minimize coupling in directional antennas, they should be placed at least 10 wavelengths away from each other. This can still be done with omnidirectional antennas to limit near-field coupling and allow only far-field coupling to the receive antennas, but it will still result in a significant amount of the transmitter signal energy entering the receiver. For some applications, it is desirable to have antenna diversity (different transmitter and receiver antennas), but that comes with the previously mentioned considerations. If there is a need for greater transmitter/receiver isolation than what antenna diversity can provide, then engineers can choose from several different methods and hardware components. If it is possible to incorporate time- division multiplexing (TDM), then a synchronized switching scheme can be used where only the transmitter or receiver is switched on to the antenna path. This can provide an extremely high amount of isolation, WILCS02 Wi-Fi ® Network Controller ICs/Modules mouser.com/microchip-wilcs02-modules