This article addresses
the radio frequency (RF) design challenges of terminals for carrier aggregation
(CA). CA is one of the key features of the Third Generation Partnership Project
(3GPP) Long Term Evolution (LTE), helping to achieve higher data rates by
transmitting multiple carriers from or to the same terminal. In Release-10 of
LTE, up to five carriers can be aggregated, each with a bandwidth of 1.4, 3, 5,
10, 15, or 20 MHz, thereby allowing for overall bandwidth of up to 100 MHz.
Wide bandwidths are very desirable, as they enable mobile broadband services
such as high-definition video streaming to take off. Unfortunately, in many areas
of the world, there are currently few, if any, contiguous spectrum allocations
of 20 MHz or higher. CA is the technical solution to overcome the spectrum
fragmentation, and it provides the flexibility needed to adapt to a wide variety
of spectrum scenarios. However, with flexibility come RF design challenges of
terminals, as will become clear in this article.
