Abstract-This paper presents the graphical solutions of conjugately characteristic-impedance transmission lines (CCITLs) implemented by periodically loaded lossless transmission lines (TLs), which can exhibit both non-negative (NNCR) and negative characteristic resistances (NCR) with the corresponding propagation constants. The standard T-chart and the extended T-chart are employed to solve CCITL problems with NNCR and NCR cases respectively, depending on the argument of CCITL characteristic impedances. The range of plotting of the standard T-chart and the extended T-chart is always inside or on the unit circle, and always outside or on the unit circle of the voltage reflection coefficient plane, respectively. Two examples of finite periodic TL structures providing both NNCR and NCR cases are given. It is found that both T-charts provide the same input impedance of the corresponding CCITLs as expected, and the standard T-chart is more familiar and easier to deal with.
Abstract-This paper presents an ultra-wideband rectangular ring fed by stepped monopole antenna.The initial parameters of rectangular ring are first considered to obtain the bidirectional pattern with the desired resonant frequency. Subsequently, the parameters of stepped monopole for enhancing impedance bandwidth are investigated. To study the impedance and radiation behaviors, the simulations of the proposed antenna have been carried out. It is found that this antenna offers a bidirectional beam with the impedance bandwidth (return loss lower than −10 dB) covered the frequency range from 3.1 to 10.6 GHz. At the desired direction along this frequency band, the gain of 2.33-5.21 dBi is achieved. Furthermore, the prototype antenna was fabricated and measured to verify the simulated results. Obviously, the simulation and measurement are reasonably in good agreement.
Abstract-Radiation characteristics of a probe-excited rectangular ring antenna are investigated by using the dyadic Green's function approach. The radiation characteristics, such as radiation pattern, beam-peak direction, half-power beamwidth and directivity, are analyzed. For the specified operating frequency, the ring width and ring height are selected as the same cross-sectional dimension of rectangular waveguide operated at the dominant mode. The effects of the excited probe and rectangular ring to the modal distributions are described. For the desired modal distribution, the directivity primarily depends on the ring lengths. For compact size of the proposed antenna, the ring length of 0.4λ is chosen to provide a bidirectional pattern with the calculated half-power beamwidth in E-plane and H-plane of 100 and 69 degrees respectively, and directivity of 4.43 dBi. Furthermore, the prototype antenna was fabricated and measured. The coincided results between the theory and the experiment are obtained.
In this letter, the standard theory of small reflections (TSR) is generalized for the case of multi-section transformers, composed of conjugately characteristic-impedance transmission lines (CCITLs) connected in cascade, with small discontinuities. Using the assumption of small reflections, the total voltage reflection coefficient looking into the input of the transformer can be approximated, resulting in the TSR for multi-section CCITL transformers with small discontinuities. Numerical results, some physical interpretations and potential applications of results will be discussed in this letter.
Index Terms-Conjugately characteristic-impedance transmission lines (CCITLs), theory of small reflections (TSR).
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