Research And Design Of Power Amplifier Based On Filter Matching Network

With the continuous innovation and development of communication technology,integration,miniaturization and high efficiency wireless communication systems have become a trend.As the main ingredients of the radio frequency(RF)front-end circuit,power amplifier and filter are indispensable,and their performance has a greater impact on the entire communication system.In traditional RF front-end circuits,the power amplifier(PA)and filter are usually designed separately,they are cascaded through a 50 ? interconnection transmission line to achieve signal amplification and filtering.On the one hand,this design method will increase the size of the overall circuit;on the other hand,it may introduce additional losses caused by the mismatch between the two devices,resulting in the decline of the performance of the whole communication system and the increase of manufacturing cost,which is difficult to realize the development trend of today's wireless communication system.In order to solve the above problems,the collaborative design of PA and filter has been extensively researched in recent years.The most widely used is to embed the filter into the matching network of the PA to realize the design of the filtering power amplifier.This method directly matches the input impedance of the filter to the drain terminal of the transistor,which can effectively avoid the extra loss caused by the mismatch between the PA and the filter cascade.The filter here has a filtering effect and can also perform impedance transformation.The final designed PA has both functions of signal amplification and filtering.In addition,the circuit as a whole has a high degree of integration,which is in line with the development trend of today's wireless communication systems.This article has carried out in-depth research on the PA based on filter matching network design,and the specific work is as follows:(1)A broadband bandpass filter matching network is proposed,which is composed of a branch load coupled microstrip line structure and a harmonic control network.The branch load coupled microstrip line structure can realize broadband filter matching,and the harmonic control network can tune the second harmonic and third harmonic impedance to improve the efficiency of the PA.The proposed filter network is matched to the drain terminal of the transistor to realize a PA with filtering effect.The actual measurement results show that in the 3.3-3.7 GHz operating frequency band,the saturated output power is 39.5-41.6 d Bm,the drain efficiency is 59%-72%,and the gain is basically above 10 d B.(2)A design method of Doherty power amplifier(DPA)with filtering effect is proposed.The high efficiency linearization characteristic DPA is combined with the bandpass filtering characteristic,and its filtering effect is realized through the filtering power divider and the filtering post-matching network.For the input and output matching network of the PA,the step impedance matching method is used for broadband matching.A DPA with filtering effect is designed.The actual measurement results show that in the 2.3-2.7 GHz operating frequency band,the saturated output power is 43.2-44.6 d Bm,and the drain efficiency is 66.4%-77.6% at this time.When the power is backed by 6 d B,the drain efficiency is 51%-62%.