A Miniaturized Study Of 3dB Microstrip Branch-line Coupler

The destitute trend of communications frequency resource is increasingly obvious with the rapid development of mobile communication technology. communications frequency is gradually developing to high frequency segment. In the development of high frequency communication technology, the strategic significance of deneloping microwave and millimeter-wave technology is prominent.microstrip coupler is important parts of an apparatus in the system of microwave and millimeter-wave, the systemic capability and technical level are restricted by it, the quality of the whole system is directly influenced by its capability. The miniaturized theory of microstrip coupler is developing trend,for improving integration degree of Microwave Integrated Circuits (MIC) and Monolithic Microwave Integrated Circuits(MMIC).In the thesis, the study of miniaturized microstrip branch-line coupler by the theory of shortening transmission line with stub microstrip stub, the miniaturized method makes the area of microstrip branch-line coupler reduced to 44%,comparing with the area of conventional 3dB microstrip branch-line coupler. simulating the microstrip coupler by software Advanced Design System (ADS), educing the S- parameter characteristic curve.the S- parameter reaches applied index of coupler.Microstrip branch-line coupler is ulteriorly miniaturized by heterogeneous trapezoid microstrip,the mutual overlapped problem is solved by this heterogeneous trapezoid microstrip, the miniaturized method of trapezoid microstrip makes the area of microstrip branch-line coupler reduced to 60%,comparing with the area of conventional 3dB microstrip branch-line coupler.Carries on the miniaturization with the trapezoid fishbone microstrip as the shortening transmission line's branch line to the conventional 3dB microstrip branch-line coupler , the miniaturized microstrip branch-line coupler by using the method of trapezoid fishbone microstrip occupies the Electric circuit foundation plate area is only 25%,comparing with the area of conventional 3dB microstrip branch-line coupler,achieves miniaturized the goal. simulating the microstrip coupler by software Advanced Design System (ADS),and educing the S-parameter characteristic curve, compares the simulating S-parameter frequency response curve with theoretical calculation's S- parameter frequency response curve, they are consistent in the center frequency and lower than the central frequency band. the phase difference between straight port and coupling port is close to 90 degree,which is consistent with the phase difference between straight port and coupling port of the conventional 3dB microstrip branch-line coupler .Indicated that this kind of miniaturized the theory is effective and feasible.