Research On Microwave Reconfigurable Power Dividers And Their Applications

With the development of technology,more and more functions are required in a single system and the reconfigurable circuits have been paid much attention to.Microwave power dividers,as key components,have been widely used in the microwave systems.Microwave reconfigurable power dividers can combine the functions of microwave switch and power divider together.The output port of reconfigurable power divider can be selected as the transmission port or as the isolation port,and the isolation between transmission ports can also be realized.The performances of systems can be improved by introducing this function and reconfigurable power dividers have been utilized for high-efficiency power amplifiers.However,the research on reconfigurable power dividers is still at the preliminary stage at present.There are many problems:(1)it is difficult to realize the reconfigurable impedance transformer network;(2)effects of the parasitic parameters of the p-i-n diode are not taken into consideration in the reconfigurable power divider;(3)realization of the reconfigurable power divider with a high dividing ratio is still difficult;(4)there is no research about the multi-way reconfigurable power divider;(5)few applications about the reconfigurable power dividers are proposed,except used in the power amplifier.In order to solve the problems mentioned in above,the contributions of this thesis are shown as follows.1.A switch element with matching network(SEMN)and reconfigurable impedance trans-former networks,as the key components in reconfigurable power divider,are proposed.Since the parasitic inductance and reverse capacitance of the p-i-n diode involved in matching,a good matching performance and a high isolation can be obtained by the SEMN with one p-i-n diode.No lumped elements such as dc blocking capacitors are required in the SEMN.For reconfig-urable two impedance transformer network,with different parameters of one p-i-n diode under forward bias and reverse bias,two load impedances can be both transformed to port impedance,in which,the load impedance can be either real impedance or complex impedance.Moreover,the reconfigurable multiple impedance transformer network(RMITN)is proposed.With the parameters of N-1 p-i-n diodes under different bias conditions,N different load impedances can be all transformed to port impedance.In above reconfigurable impedance transformers,no lumped elements such as dc blocking capacitors are required and the parameters of p-i-n diodes are all involved in matching.2.With four reconfigurable real impedance transformer networks and nine SEMNs,a three-way reconfigurable power divider based on the modified Luzzato divider is proposed,which can provide seven different states in the three-path mode,the two-path mode,and the single-path mode.In each transmission mode,the input port and transmission ports are all matched and high isolations between transmission ports are obtained.Next,when an N-way reconfigurable power divider is realized by connecting the two-and three-way reconfigurable power dividers in cascade,many switches are required and some transmission modes can not be realized with equal power dividing for transmission ports.In order to solve these problems,an N-way recon-figurable Gysel power divider is proposed with one RMITN and 2N-1 SEMNs.In this N-way reconfigurable power divider,N different transmission modes with 2~N-1 states can be realized by the use of only 3N-1 p-i-n diodes.In each transmission mode,the input port and transmission ports are all matched and high isolations between transmission ports are obtained.Moreover,no lumped elements are required in above reconfigurable power dividers.3.A novel simple structure for the realization of a reconfigurable unequal power divider with a high dividing ratio is presented.Since the power dividing ratio is only determined by the electrical length of a transmission line and one RCITN and two SEMNs are used in the structure,the high power dividing ratio can be easily obtained by this reconfigurable unequal power divider.In addition,no output impedance transformers are needed and only three p-i-n diodes are required in the structure.4.Compared with microwave switch and power divider,reconfigurable power divider can provide more selections and the performances of systems can be improved.(1)A reconfigurable network consists of a two-way reconfigurable power divider and two reflective switches.By using this reconfigurable network instead of the switch in the conventional switched multi-beam circular array,an additional beam can be provided with each two adjacent elements and the gains at the depressed areas between each two adjacent original beams are improved.In addition,better mitigation of the fading from multi-path propagation can be obtained since more diversity patterns with low correlations are provided.(2)When the reconfigurable network in above is extended to multi-way reconfigurable power divider,the multiple antenna selection(MAS)is proposed for switched combining and selection combining.More selections can be obtained with one RF chain and stronger signal-to-noise ratio(SNR)can be provided in MAS schemes.(3)With single-/double-port excitation,2L-1 beams can be obtained with L input ports in beam-forming networks.Rigorous analyses of double-port excitation in beam-forming network are given and a sample reconfigurable network by using the reconfigurable power divider is presented for realization of the single-/double-port excitation.In addition,this method can be used in Butler matrix and Rotman lens.