Broadband High-efficiency Power Amplifiers Research Articles

Multispectrum Signal Transmitters: Advances in Broadband High-Efficiency Power Amplifiers for Carrier Aggregated Signals

The growing demand for broadband mobile access drives the deployment of sophisticated and increasingly spectrum-efficient modulation techniques and access technologies resulting in communication signals with highly varying envelopes and increasing peakto-average power ratios (PAPRs). These communication signals call for advanced transmitter architectures and design techniques. This is particularly the case for the constituent radio frequency (RF) power amplifiers (PAs), which are required to amplify communication signals efficiently while maintaining signal quality and minimizing out-of-band emissions in adjacent channels. The Doherty [1] technique has been successfully applied to develop highly efficient solid-state PAs for wireless communication applications. Benefiting from recent advancements in laterally diffused metal oxide semiconductors (LDMOSs), and taking advantage of the advent of gallium nitride (GaN) technology, Doherty PA (DPA) demonstrators with average drain efficiencies approaching 50% were reported in [2]-[4]. Unfortunately, the underlying narrow bandwidth of these demonstrators currently restricts their use to infrastructure supporting third-generation (3G) wireless networks. Communication signals required by the 3G Partnership Project (3GPP) specifications for long-term evolution (LTE) will have to utilize carrier aggregation to meet the need for transmission bandwidth. Carrier aggregation refers to the use of more than one spectrum portion to deploy multiple component carriers to yield aggregated channels of wider transmission bandwidth (up to 100 MHz). Figure 1 illustrates the three carrier aggregation scenarios that are envisaged: 1) intraband contiguous carrier aggregation (contiguous component carriers aggregated in the same operating band), 2) intraband noncontiguous carrier aggregation (noncontiguous carriers aggregated in the same operating band), and 3) interband carrier aggregation (carrier aggregation of component carriers in different operating bands that may be contiguous or noncontiguous within each band).

Design of Broadband High-Efficiency Power Amplifiers Based on a Series of Continuous Modes

In this letter, a series of continuous modes for designing broadband high-efficiency power amplifiers (PAs) are proposed, which extend the continuous mode concept. The impedance solutions space based on these modes offer a greater freedom for realizing broadband high-efficiency PAs. To verify this theory, a high-efficiency PA over a 54.5% bandwidth from 1.6 to 2.8 GHz is designed. The simulated results show that the fundamental impedances in this PA are found to be in good agreement with the calculated ones. Moreover, this PA delivers average output power of 14.2 W with an average drain efficiency of 75.7% in the target band.