Research And Design Of Miniaturized Four-port And Eight-port Directional Couplers

In recent years,with the rapid development of wireless communication,high-performance microwave components,including couplers,power distributors,filters and wireless RFID systems,play an important role in wireless communication systems.As a key component of microwave and millimeter wave systems,couplers have been widely concerned.For example,couplers can be used to various balanced power amplifiers,mixers and feed networks of multi-port antenna.Based on the traditional patch couplers,miniaturized four and eight-port directional couplers are studied in this Thesis.The specific work is as follows:1)A new type of miniaturized rectangular patch coupler is proposed.Two symmetrical cross grooves are etched on the rectangular patch of coupler.By adjusting the length of two sets of grooves,the coupling degree is changed.The realized two couplers have coupling degree of 3 and 6.7d B and operate in the 5.5 GHz band.The 3d B has a 1d B amplitude unbalanced bandwidth of 20% and the 90°±5° phase difference bandwidth of 27.2%.For the 6.7 d B coupler,the corresponding values are 12.7% and 12.7%,respectively.On this basis,a miniaturized rectangular patch 3 d B coupler with nonstandard phase difference is designed.The coupler is miniaturized by etching two groups of horizontal and vertical bending grooves on the rectangular patch.Also,the phase difference of the output signal of the two ports can be adjusted by introducing LC matching network with variable inductance.The size of the coupler is 8×5.5×0.635 mm3.The realized coupler works at 4~5 GHz,and it has the 3 d B±1 d B bandwidth of 18%,the 45±5° bandwidth of 20%.When the inductance changes in the range of 0.2n H~1 n H,the phase difference of the output ports changes in the range of 26°~57°.2)A new miniaturized broadband eight-port directional coupler is proposed.It consists of three layers of metal and two layers of dielectric.The top and bottom metal layers are microstrip lines,and the middle metal layer is ground plane loaded periodically with rectangular slots.The size of the coupler is reduced by arranging the ports symmetrically.The rectangular slot loaded in the middle layer help to enlarge the working bandwidth of the coupler.At the same time,the frequency of the coupler is adjusted by the length of the loaded slot.The realized eight port coupler works at 1.75 GHz,and the bandwidth of 6±1d B is 15.5%.The size is 50×20×0.762 mm3.Also,its dimension is reduced by 40%...