Design Of Broadband Band-Pass Filtering Power Amplifiers

With the continuous reform of the wireless communication networks,high integration,broadband and high efficiency have become the inevitable trend of the communication systems.In the traditional transceiver system,the power amplifiers are often followed by a bandpass filter to adjust the spectrum.However,the power amplifiers and the bandpass filters are designed independently and connect each other through a 50 ? transmission line,which will increase the system size as well as introducing the loss,then,decreasing the efficiency.Therefore,how to combine the two devices of bandpass filter and power amplifier into one design has attracted many attentions.Conventionally,the most effective method to implement the bandpass filtering power amplifier is to replace the output matching network of the power amplifier with the bandpass filter.Comparing with the filter-power amplifier cascade structure,the co-designed filtering power amplifier possesses higher integration and lower loss.In this thesis,the broadband bandpass filtering power amplifiers are mainly studied.Moreover,the co-design idea is applied to the Doherty power amplifier for the first time.The main contents of the thesis are:1.Based on the asymmetric inter-digitally coupled resonator,a wideband bandpass filter with high selectivity is designed,and its input port is matched to the output port of the transistor to implement a broadband bandpass filtering power amplifier.The simulated and measured results show that the wideband bandpass filtering power amplifier not only possesses excellent filtering characteristics such as high selectivity and wideband harmonic suppression,but also has competitive saturated gain and efficiency.2.Based on the unequal-length branch-line resonator loaded with two stubs,abandpass filter with high selectivity is proposed,and its transmission phase is tuned to be 90°.Therefore,the bandpass filter can replace the conventional ?/4 microstrip in the output matching network of the carrier power amplifier to meet the impedance matching conditions at saturation and back-off.Thus,the bandpass Doherty power amplifier can be implemented.The simulation results show that the proposed bandpass Doherty power amplifier can not only possess high selectivity,but also achieve high efficiency of 78.2% and 60% at saturation and 6-d B back-off.