Enhancing Carrier Aggregation: Design of BAW Quadplexer With Ultrahigh Cross-Band Isolation

Carrier aggregation (CA) is a technology first introduced in LTE-Advanced (LTE-A) to increase the peak data rate of 4G networks (for example, the maximum available speed) [1]. The mobile network operator can increase the total available bandwidth for a single user by aggregating multiple channels together, thereby increasing the user data rate as well as the spectrum utilization efficiency and resource allocation flexibility of the entire network. Before LTE-A, mobile network operators could allocate the spectral resource only to a particular user within a single designated frequency band, limiting the maximum channel capacity. The realization of CA allows network operators to create larger channels from nonadjacent spectrum blocks. For example, operators can use a 10-MHz carrier from the 2,100-MHz band and combine it with another 5-MHz carrier from the 700-MHz band to create a 15-MHz LTE channel. The LTE-A standard specifies that each of the component carriers (CCs) of the communication signal is limited to 20 MHz of bandwidth. Aggregation of up to five CCs allows a maximum of 100 MHz of total signal bandwidth, as depicted in Figure 1. This leads to a fivefold increase in channel capacity and data speed [2]. It is projected that CA technology will continue to be widely and intensively used in future-generation communications, such as 5G.