Multiplexer Theory And Realization

As an important field of modern science, electronic theory is getting great developments with wonderful acceleration, meanwhile we witness the great developments of solid techniques, and relevantly the endless coming of new types of device. To meet the requirement of the circuits which become more and more complicated, on the one hand the circuit analysis and synthesis techniques becomes more and more complicated and the division of study fields becomes more and more detailed, on the other hand it becomes more and more important to study, innovate and consummate the theory with universality and independent on device types. It is same for multiplexers. To meet the requirements of more and more new types of multiplexers, it attracts great some scholars to study, innovate and consummate multiplexer theory with universality and independent on device types.In this thesis, by analyzing the character of coupled resonator filters and the influences between channels of multiplexers, to meet the actual requirement of filters and multiplexers in design and realization, the direct design if given for relatively boarder bandwidth symmetrical diplexers, relatively boarder bandwidth parallel symmetrical diplexers, relatively boarder bandwidth parallel asymmetrical diplexers and symmetrical 3-channel multiplexers.The influences between channels of multiplexers are analyzed. A channel will cause a relatively big reactance for its neighbor channels, break their passband characters, therefore the influences between the filters which are connected directly will cause mis-match at their common port and destroy the power transfer property.According to the influence characters among channels of multiplexers, by analyzing and classifying relevant papers, it is found that the direct design manner has advantages of convenience, small calculation load, big applicability, is an efficient tool for multiplexer design. Upon the basis that all element values are, known for each channel filter operating in isolation, by this manner some elements are modified to offset the influences among channels of the multiplexers, and minimum extra elements are added when necessary. The key is to find the direct formulas for relative element values, simplify the design problem to arithmetic problem, and avoid complicated theoretical study and mathematical calculations. For a multiplexer consists of directly connected bandpass filters, because of the non-linear relationship of the input impedances of filters and their single element values, it is impossible to offset completely the influences among the channels by absolutely exactly modifying some elements, and that is notVrequired for most situation. In fact, if we ignore high order error, the requirement of multiplexers design will be satisfied by only modifying part of the elements. According to the definition of band-separation factors between channels of multiplexers, the modified element values of the corresponding lowpass prototypes can be expanded as power series in well-defined band-separation factors separately, and the input impedances of the both channels can be expressed as functions of the modified element values. To keep all zero reflection frequencies of the lowpass prototype as corresponding zero reflection frequencies of the corresponding channel, the coefficients for the power series can be determined, and the explicit design formulas can be given for all modified element values of the lowpass prototypes. The study of multiplexers in this thesis is just based upon this thought of design.The circuit structure of coupled resonant filters and their low-pass prototypes are introduced, including the property and practical realization of their components such as impedance inverters, the concept of power transfer function, also the direct design formulas for its lowpass prototype is given. Furthermore, from the point of practice, an important function of impedance inverters in coupled resonant filters is introduced: it can modify any capacitors in lowpass prototypes to any value...