Design Theory and Realization of Multi-Band Couplers and Power Dividers
|School||South China University of Technology|
|Course||Electromagnetic Field and Microwave Technology|
|Keywords||Couplers power divider impedance transfotmer multi-band broadband filtering coupler 0-dB coupler (crossover)|
In the current multi-band and multi-standard portable wireless systems, transceivers aremostly implemented by combining several parallel single-band or single-standardradio-frequency (RF) front-ends, the partially shared analog baseband circuitry and severalbroadband antennas combined with switching arrays to select the desired signal path.Increasing the number of frequency bands and operating standards will increase the totalon-chip silicon area and the number of off-chip passive components of the conventionalmulti-band and multi-standard transceivers, which means that the size and cost of the systemincrease. It will also increase the power consumption and shorten the battery life. In order tomeet these challenges of the design of multi-band communication systems: small size, lowcost and low power consumption, all kinds of innovations on multi-band systems andmonomer multi-band devices are created in academics and industry circles.Couplers and power dividers are basic passive components of the microwavecommunication systems, and widely used in the design of all kinds of microwave circuits,such as balanced amplifiers, mixers and feeding network for an antenna array. Trying to slovethese problems mentioned above, this dissertation is devoted to constructing the theory ofdesign of multi-band couplers and power dividers, proposing new design methods, andcreating novel multi-function coupler and power divider structures. This dissertation issupported by the National Natural Science Foundation of China (Guangdong joint fund) keyproject (61171029)“Compact planar UWB antennas and RF components”. The maininnovations of this dissertation are listed below.1. The coupling theories of the four-port network with phase inverter and the symmetricalthree-port network are proposed. These theories employ network theory and even-oddmode analysis to derive the equivalent port impedances of the four-port network withphase inverter and the equivalent port admittances of the symmetrical three-port network,which is under the conditions of reciprocity, matching, and isolation. Then, the designmethod of multi-band/broadband0/180°based on the equivalent port impedances of thefour-port network and the design method of multi-band/broadband power divider based onthe equivalent port admittances of the symmetrical three-port network are proposed. Byusing the proposed design methods, the complex four-port issues of design a multi-band0/180°coupler are turned into the simple single-port matching issues of the equivalentport impedances, while the complex three-port issues of design a multi-band power divider are turned into the simple single-port matching issues of the equivalent portadmittances. These new theories and new methods are compatible with the traditionaldesign methods, and they can not only explain the traditional design, but also from thepoint of view of impedance matching, explain the working mechanism of the multi-bandcouplers and power dividers. Finally, two novel tri-band branch line couplers and onenovel tri-band Wilkinson power divider are proposed to verify these theories throughsimulation and experimentation. This part of research work has been published in IEEETransactions on Microwave Theory and Techniques、IEEE Microwave and WirelessComponents Letters and Proc. IEEE Int. Antennas Propag. Symp.. One utility modelpatent and one invention patent have been granted and applied, respectively.2. The miniaturized dual-band E-type λ/4impedance transformer and tri-band Π-type andT-type λ/4step impedance transformers are proposed and analyzed. Based on the E-typeλ/4impedance transformer, a novel dual-band branch line coupler is proposed. Comparedwith conventional dual-band branch line coupler, the proposed dual-band branch linecoupler features compact size, many design freedoms, a wide range of frequency ratio.Based on the tri-band λ/4step impedance transformers, the tri-band rat race couplers areproposed, for the first time. This part of research work has been published in Microwaveand Optical Technology Letters、Journal of South China University of Technology(Natural Science Edition) and Proc IEEE Asia Pacific Microwave Conf.. NominationPrize for excellent paper in2009National Conference on Microwave and MillimeterWave is awarded.3. A dual-band/broadband Gysel power divider with arbitrary power-dividing ratio forhigh-power application is proposed, and its analytical design equations are derived. Due tothe use of an inverter, the proposed Gysel power divider features compact size, broadband,good matching and isolation performances and a wide range of frequency ratio, et al. Anovel Gysel power divider with controllable bandwidth using uniform impedancetransmission lines for arbitrary power-dividing ratios is proposed. The power-dividingratio is determined only by the electrical lengths of the transmission lines and independentof the impedance of transmission lines, which overcomes the limitation of high processingprecision and the high power application caused by using high-impedance lines in theconvention design of power dividers for large power-dividing ratio. In addition, theequivalent relationship between the three-port Gysel power divider and four-port rat racecoupler with phase invert is proved. Then, compact broadband microstrip rat race couplers with superior performances are proposed for microwave integrated circuits applications.This part of research work has been published in IEEE Transactions on MicrowaveTheory and Techniques, IEEE Transactions on Microwave Theory and Techniques(Letters) and Journal of Electromagnetic Waves and Applications.4. By using the coupled-resonators, the dual-band filtering coupler is creatively proposed.This device integrates the power divider/combiner with the filtering function, whileoperating two frequency bands, which has the certain reference significance for enrichingand expanding the design method of filtering couplers. In addition, a novel full planardual-band0-dB coupler (crossover) and its analytical equations are proposed. This devicefeatures simple structure, a wide range of frequency ratio and broadband bandwidth, et al.This part of research work has been published in IEEE Transactions on MicrowaveTheory and Techniques and IEEE Microwave and Wireless Components Letters.Amoung the above mentioned innovation areas, the first one belongs to the the area ofdesign theory of multi-band couplers and power dividers, while the second, third, and fourthbelong to the area of the realizations of multi-band couplers and power dividers.