A Balanced Feed Network Based On Slot-Microstrip Line Transitions And Its Application

Due to the excellent performance in anti-electromagnetic interference and environmental noise suppression,balanced circuits have gradually been widely used in modern communication systems.However,the current RF devices are mostly single-ended structures,and the matching with the balanced circuit will increase the volume and generate a certain loss.Therefore,the construction of a fully balanced system is imminent.The key components of the balanced system include balanced power dividers/combiners,balanced antennas(arrays),balanced duplexers/multiplexers,etc.The thesis has studied the forms and characteristics of several commonly slot-microstrip line transition structures,and designed two balanced four-way power divider,a new duplexing matching network and a balanced dual-band duplexing power divider based on them.Finally,the above designs are applied to the antenna arrays.The main contents of this thesis are as follows:In this thesis,a broadband balanced-to-single-ended four-way power divider based on the slot-microstrip line transition structure is designed first.The power divider is composed of three series T-junction slot-microstrip line transition structures and a U-shaped balanced port.The series T-junctions can output signals of equal amplitude and opposite phase in a wideband,and the U-shaped balanced port can achieve a high level of CM rejection and good DM transmission characteristics.Then the power divider is used to feed four microstrip quasi-Yagi antennas to realize a broadband antenna array with DM impedance bandwidth from 5.7 GHz to 8.9 GHz,a peak gain of 12.5 d Bi and a maximum cross-polarization level of-25.6/-34.6 d B in the E-/H-plane at 5.8 GHz,and a CM gain of less than-13 d Bi over the full bandwidth.Then,this thesis designs a new matching network based on slot-microstrip line transition structure and implements a balanced dual-band duplexing power divider.Firstly,a wideband balanced-to-balanced four-way power divider based on slot-microstrip line transition structure is designed.It combines series and parallel T-junction slot-microstrip line transition structures to realize phase shift and power distribution functions in a wide bandwidth.Then,a new asymmetric series T-junction slot-microstrip line transition structure was proposed as a duplex matching network for the first time in this thesis.The operating frequencies of the two output ports of this design are independently adjustable and can be applied to balanced ports.Then the above design is combined with the stepped impedance resonator to realize a differential dual-band duplexing power divider with superior performance.The DM center frequencies are 5.38/5.96/6.68/7.3GHz,with-3d B fractional bandwidths of 3.35/2.84/3/2.48%,respectively.The minimum DM insertion losses within the passbands are1.54/1.45/1.20/1.56 d B;the CM transmission coefficient are less than-40 d B at all working frequencies,and the CM reflection coefficients is close to 0d B.Finally,it is combined with a balanced antenna array to realize a balanced quad-band filtering antenna array with good performance.