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Multiplexers Fit the Bill for Carrier-Aggregation Filter Challenges

March 7, 2016
This application note describes how multiplexers can solve complex RF filtering challenges that result from carrier aggregation.

Deployment of carrier aggregation (CA)—combining two or more blocks of spectrum or “component carriers” (CCs)—by mobile network operators worldwide has fueled ever-faster data rates. When CA is implemented, mobile devices communicate on multiple LTE bands simultaneously.

However, to maintain good reception and battery life, interference between the bands must be avoided while minimizing insertion loss. In the white paper, “Addressing Carrier Aggregation Challenges Using Multiplexer Solutions," Qorvo discusses how multiplexers can solve such challenges associated with CA.

Most early CA deployments combined only two CCs. However, network operators will add combinations of three or more bands as a means to further accelerate data rates. But with that benefit comes the challenge of complex RF filtering.

When utilizing CA, each device transmits and/or receives on more than one CC simultaneously. This approach creates the need for cross-isolation, which will prevent interference between CCs. Achieving cross-isolation requires filters to sufficiently attenuate out-of-band signals. Each CC can then avoid loading the other aggregated bands. Every filter must also minimize the insertion loss of the transmitted signal to maintain good reception and minimize power consumption.

While cross-isolation is not as difficult to achieve when aggregating widely separated bands, it becomes much more difficult to attain when combining bands that are close together. In these instances, multiplexers become a practical solution to meet system requirements.

Because multiplexers integrate transmit and receive filters for the aggregated CCs into a single component, they provide the required isolation while allowing multiple CCs to connect to the same antenna at the same time. The white paper describes the complex performance requirements for multiplexers by comparing the isolation requirements when communicating without CA versus the requirements when implementing CA. The document also discusses Qorvo's QM25005 multiplexer.

Qorvo Inc., 2300 NE Brookwood Pkwy., Hillsboro, OR 97124; (844) 890-8163

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