Optimization Design Based On Multi-port Receiver Front-end

With the rapid development of wireless communication technology,information exchange has become the most basic needs in human society.All kinds of wireless communication products are becoming more and more popular in daily life,which connect the world as a whole to bring convenience for people.In the process of communication,the communication standard and the frequency band of the signals are different in a variety of application scenarios.In order to effectively transmit signals,the communication system must use different modulation modes,which means that the receivers need different hardware structures,thus leading to the poor flexibility and high hardware cost.Applying Software Defined Radio technology to the direct conversion receiver can demodulate signals of different standards,frequency and modulation modes,but there are also some problems such as self-mixing and I/Q mismatch.While applying the multi-port technology to the SDR receiver front end can directly convert the radio frequency signals to the baseband signals,which not only can remove the high cost devices such as mixers,but also can eliminate the self-mixing phenomenon due to the high isolation between the input ports.Therefore,multi-port receiver has been widely concerned and studied.The main works of this thesis are listed as follows:1?The principle of multi-port front-end is described.Firstly the theories of diode detection and additive sensing are analyzed,based on which the principle of multi-port sensor network is analyzed and derived.Then the six-port principle and demodulation process are analyzed emphatically.These basic theories provide a theoretical support for the following optimization design of multi-port front-end.2 ? The microwave devices which composes the multi-port are designed and optimized,including a four section elliptic Wilkinson power divider with a frequency of 4~20GHz,which extends the bandwidth and reduces the transmission loss by increasing the sections of transmission and changing the shape of transmission lines based on the single section power divider.In addition,two optimized 3dB couplers are designed.One is an optimized cross and series coupler with the capacitor compensation technology,which minimizes the parasitic impedance effect due to the intersection discontinuity and effectively improves the performance of the coupler;Another is an optimized microstrip slot coupler based on section expansion and gradient shape of the coupled lines,which extends the bandwidth to 2~20GHz and improves the performance of the coupler within the broadband.Finally,from the processing point of view,the parameter tolerance of the optimized power divider and couplers is analyzed,which provides a certain reference value for thefollow-up fabrication.3?From the aspects of bandwidth and performance of the six-port junction,two improved six-port junctions are designed by using the optimized power divider and couplers.One is a six-port junction with a four-section Wilkinson power divider and three seven-section cross and series couplers over the frequency of 2.5~8GHz,which can effectively improve the overall performance of the six-port junction by the section expansion and compensation capacitor technology.The other is a six-port junction with a four-section Wilkinson power divider and three five-section slot couplers over the frequency of 6~20GHz,which can effectively improve the working frequency band of six-port by section expansion and shape transformation.Finally,the simulation result and performance comparison verify the good performance of the improved six-port junctions.