Research On Broadband Radio Frequency Power Amplifiers Based On Load Impedance Control

In order to achieve super high-speed data transmission rate,the next generation wireless communication system will employ transmission signals with much wider bandwidth.As core elements of the wireless communication systems,power amplifiers are required to extend their operation bands while keeping good performance.For the required broadband applications,research on the design methods of modified continuous mode power amplifiers,novel broadband Doherty power amplifier topologies and realization of dual-band optimized broadband power amplifiers are presented in this dissertation.The main contents and innovation points of this dissertation are listed as followed:1.Analysis of the influence from the parasitic parameters and transistor package on the continuous class-B/J mode is presented.Based on the analysis,the discovered compact impedance solutions on the package plane are suggested to be adoptted for the broadband class-B/J power amplifiers design.A simplified nonlinear transistor model is built to simulate the power amplifiers performance on the condition of harmonic impedance mismatch.The realized broadband power amplifier using the proposed method achieves 0.8-3.6 GHz operation band with 55.8-74.1% saturated drain efficiency.2.The bandwidth limitations of the conventional Doherty structure are analyzed.To break through these limitations,a modified post-matching Doherty topology employing low-order impedance inverters is presented.By using the post-matching structure,the bandwidth limitation of the carrier and peaking matching networks can be avoided.Meanwhile,the proposed low-order impedance inverters extend the bandwidth of the load-modulation network.The realized Doherty power amplifier using the proposed method achieves 1.7-2.6 GHz bandwidth with 47-57% drain efficiency at 6-dB output power back-off region.3.The conventional asymmetrical structure is employed to extend the high efficiency back-off range of the post-matching Doherty topology.By using asymmetrical drain supply voltages,the post-matching Doherty power amplifies can achieve larger high-efficiency back-off ranges.The parameters of the low-order impedance inverters and post-matching networks are modified for this asymmetrical design.The designed asymmetrical Doherty power amplifier achieves above 50% drain efficiency in an 800 MHz band at 8-9 dB back-off region.4.Design method of a novel dual-band optimized harmonic controlled broadband power amplifier is presented.Dual-band harmonic control circuits and broadband fundamental matching networks are employed to improve the efficiency performance for two special frequencies in the operation band.Up to third order harmonic control can be achieved by employing the proposed matching network in the two optimized bands.The realized broadband power amplifier archives 1.8-2.7 GHz operation band and 81/74% saturated drain efficiency at the two optimized frequencies 1.9 and 2.6 GHz,respectively.5.Design method of a dual-band optimized Doherty power amplifier is presented by using dual-band load-modulation networks and matched broadband carrier and peaking power amplifiers.The dual-band Doherty operation is achieved by employing direct-matching impedance inverters and off-set lines.By using broadband matching and post-matching networks,the bandwidths of the two optimized bands are wider than the conventional dual-band Doherty structure.The realized Doherty power amplifier archives 63% and 51% 6-dB back-off efficiency at the two optimized frequencies 1.8 and 2.6 GHz,respectively.