| In the face of the upcoming abundant application scenarios of wireless communication,such as the Internet of Things and Digital Twin,multi-mode,multi-band,multifunctional transmitter system has become a competent solution.The reconfiguration technologies represented by the Software Defined Radio has made efficient and configurable transmitter system without redundant modules become possible.Moreover,the Digital Power Amplifier(DPA)can well meet these requirements.The existing DPA architecture,whether current mode or voltage mode,contains substantial DPA cells.The circuit design of those cells affects the overall performance,meanwhile,the high resolution of a DPA also brings about deeper power back-off levels.Therefore,it is key for the performance improvement of DPAs that to improve on the circuits of DPA cells along with passive power distribution and combination networks to enhance the output power and efficiency of the system in saturated and power back-off states.Enhancement can be considered from two aspects: firstly,to achieve better impedance matching of transistors;secondly,to reduce the insertion loss of the passive power distribution and combination structure.Based on the mentioned means,the key technologies of DPAs were researched.The main content and innovations in this thesis are summarized as follows:1.A K band 8-bit current mode DPA is designed based on 0.7 μm InP DHBT process.The total resolution of the DPA is separated into two parts: the equal weighted cells controlled by the highest 4 bits and binary weighted cells controlled by the lowest 4 bits.It takes into account both the design complexity along with the resolution.The circuit topology of the DPA cell adopts the differential cascode structure based on a variable gain amplifier,and the principles and factors influencing performance of the cell are analyzed.The use of differential compensation capacitors and interstage compensation inductors can effectively improve the power gain of the cells.The binary weighted cells adopt four types of transistors with different emitter sizes in the InP DHBT process to realize the non-equal weighted cells.The post-simulation results show that the output power of the DPA reaches 25.12 ～ 26.16 d Bm,and the PAE is 14.99 ～ 17.42 % in the range of 18.6 to22.0 GHz;2.A spiral transformer was designed as the four channel power divider to achieve a single driver drives four DPA cells for cutting down DC power consumption and chip size;The power divider model is derived based on the Thévenin equivalent circuit of the transformer,and its impedance conversion is analyzed based on the model,and is compared with the simulation results using the multi-port network scattering parameter analysis theory;The simulation results show that the amplitude imbalance of the four pairs of differential output ports of the transformer is less than 1.19 d B,while the phase imbalance is less than 3.93 °;3.A broadband two-finger Balun based on a spiral transformer with low insertion loss is proposed as the power combination network.The method of cross connection between the output ports of the DPA cells and the input ports of Balun was applied into the current mode DPA.The impedance conversion mechanism of the Balun power combination network is derived based on the Thévenin equivalent circuit of the ideal transformer.It indicates that the method of cross connection is beneficial to minimize the winding resistance loss.Adopting two stages of balun to form a power combination network,and by performing electromagnetic simulation to extract and optimize the parameters of the Balun,the results show the insertion loss of the whole power combination network is 2.49 ～ 3.25 d B with combination efficiency of 47.32 ～ 56.31 %in the range of 18.6 ～ 22.0 GHz. |
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