Research And Design Of Compact Ultra-Wideband And Phase-Adjustable Phase Shifter

A phase shifter is a microwave device that can control the phase of a radio frequency signal without generating energy attenuation.It is widely used in microwave phase measurement,communication systems,antenna arrays,radar systems,and microwave automatic control systems.In recent years,digital phase shifters have developed rapidly.However analog phase shifters cannot be replaced because of their advantages of continuous phase modulation,so they still have important research significance.This thesis studies the transmission line type phase shifter and the reflection type phase shifter,it analyzes the basic principle of the phase shifter,and designs the ultra-wideband Schiffman phase shifter and the reflection-type phase shifter based on the varactor diode.The main work of the thesis is as follows:(1)An ultra-wideband Schiffman phase shifter is designed.The phase shifter is mainly composed of two transmission lines.One acts as the main line which is loaded with stub.The other serves as a reference line.The main line part uses a thin microstrip line instead of the inductor,which is loaded between the transmission line and the stub to achieve the phase change on the ultra-wideband.The proper choice of the length and spacing of the main line can make the phase difference between the two transmission lines remains unchanged in a relatively wide the frequency range.The designed phase shifter works at 2-8 GHz.It has a insertion loss less than 2 d B,and the phase difference of 90 °.The designed phase shifter has a simple structure and low processing cost.It can also maintain a constant phase difference within a wide operating bandwidth.It can be widely used in phased array antennas with fixed phase differences.(2)A reflection-type phase shifter based on a varactor is designed.First,a low-insertion loss phase shifter is proposed.It consists of two cascaded four-port directional couplers and eight tunable reflective circuits.The designed phase shifter works at 5.19-5.84 GHz.It has a insertion loss lessthan 1.09 d B,and the phase difference of 250 °.Based on this,a compact phase shifter is designed,which consists of two cascaded four-port directional couplers and four tunable reflective circuits with varactor diodes.By adjusting the voltage applied to the varactor diode,its capacitance can be changed and further the reflected phase of the output wave is changed,the phase shifter is miniaturized by bending the transmission line of the reflection circuit.The phase shifter works at 5.51-6.64 GHz,Its insertion loss is also less than 1.86 d B,and the maximum phase shift in the operating frequency band reaches 406.77 °.The phase shifter has a small size and good performance,and can dynamically adjust the phase shift range of the phase shifter.Therefore,it can be widely used in wireless communication systems.