| This dissertation presents network synthesis techniques for designing quarter-wave-length-coupled microwave transmission line filter networks. A network is comprised of individual resonators. Each resonator section has a specific response which can be described in terms of the frequency selectivity or Q of the resonator. The goal of network synthesis is to combine resonators with different responses, and thus different Q values, to form a desirable overall network response with a network total Q.; This dissertation is concerned with achieving a particular response called the maximally-flat response, which occurs when the derivatives of the response with respect to frequency are zero at the resonant or central frequency of the network. For quarter-wavelength-coupled transmission line networks this condition is met by setting all of the lower-order terms of the transducer loss function to zero. The highest-order term of the transducer loss function determines the total Q of the network. Setting all lower-order terms to zero yields the parameters, e.g. impedance values, of the individual resonators necessary to achieve a maximally-flat response for the network. By describing the individual resonators in terms of their Q values, any arbitrary resonator can be used in the network as long as it resonates at the frequency of the network with the given value of Q.; Each chapter of this dissertation is a self-contained paper. After an introductory chapter, quarter-wavelength-coupled filters with uniform coupling lines are addressed. First, an approach is presented for creating maximally-flat quarter-wavelength-coupled filters using quarter-wavelength shorted-stub resonators. This approach provides a more accurate value for total Q than current approaches and creates a truly maximally-flat response. Next, this approach is generalized to use arbitrary resonators by describing quarter-wave shorted-stub resonators in terms of their value for Q. This approach is referred to as the Q Distribution Method. A chapter is devoted to providing examples using a variety of different parallel resonators. In addition, an approximate closed-form expression for the Q distribution is derived using the binomial transformer equation.; The Q Distribution Method may also be applied to designing quarter-wave transformer impedance matching networks. Unlike current techniques, it yields a value for the total Q of the impedance matching network, makes it possible to create useful nonmonotonic impedance matching network solutions which have a degraded maximally-flat form. Finally, parallel resonators are added to quarter-wave transformer impedance matching networks to improve the performance of the impedance matching network in three ways. First, adding parallel resonators improves the poor stopband rejection from which quarter-wave transformer impedance matching networks suffer. Second, for a given load-to-source mismatch, adding more than one parallel resonator creates numerous realizable networks, i.e. values of total Q. Third, using parallel resonators requires one less quarter-wave transformer to achieve the same order of response.; An appendix describes a method for finding the Q of a resonator using S parameter data. A second appendix discusses a new transmission line resonant structure, a capacitively-loaded, half-wavelength, tapped-stub resonator. With this resonator, both the Q and resonant frequency can be set independently, and thus a tracking filter can be constructed which has a fixed Q. (Abstract shortened by UMI.)... |
