In this paper, a new topology for rectangular waveguide band-pass and low-pass filters is presented. A simple, accurate and robust design technique for these novel meandered waveguide filters is provided. The proposed filters employ a concatenation of ±90º E-plane mitered bends (±90ºEMBs) with different heights and lengths whose dimensions are consecutively and independently calculated. Each ±90ºEMB satisfies a local target reflection coefficient along the device so that they can be calculated separately. The novel structures allow to drastically reduce the total length of the filters and to embed bends if desired, or even to provide routing capabilities. Furthermore, the new meandered topology allows the introduction of transmission zeros above the passband of the low-pass filter, which can be controlled by the free parameters of the ±90ºEMBs. A band-pass and a low-pass filter with meandered topology have been designed following the proposed novel technique. Measurements of the manufactured prototypes are also included to validate the novel topology and design technique, achieving excellent agreement with the simulated results.
In this paper, we propose a novel synthesis strategy for the design of One Dimensional Electromagnetic Bandgap (1D-EBG) structures where all the performance parameters of these devices can be fully controlled, i.e., the central frequency of the forbidden band, its attenuation level and bandwidth, and the ripple level at the passbands. The novel synthesis strategy employs a new inverse scattering technique to accurately synthesize the 1D-EBG structure, targeting a properly interpolated version of a classical periodic filter fulfilling the required frequency specifications. The new inverse scattering technique follows a continuous layer peeling approach and relies on the coupled-mode theory to precisely model the microwave structures. Telecommunication and radar systems, as well as material characterization devices, will be profited by this proposal with which enhanced filters, sensors, power dividers, couplers, mixers, oscillators and amplifiers can be designed in many different technologies. As a proof of concept, a 1D-EBG structure in microstrip technology with a single forbidden band (free of spurious stopband replicas), with attenuation level of 30 dB, fractional bandwidth larger than 100%, and return loss level at the passbands of 20 dB, has been designed and fabricated. The measurements obtained are in very good agreement with the simulations and target specifications, being free of spurious replicas up to the 15th harmonic, showing the robustness and very good performance of the novel design strategy proposed.
In this paper, a methodology is proposed for the design of EBG-assisted coupled line structures in microstrip technology, controlling independently the forward and backward coupling. It is based on the use of a single-frequency-tuned electromagnetic bandgap (EBG) structure to produce a single backward-coupled frequency band, in combination with the forward-coupled frequency bands produced by the difference between the even and odd mode propagation constants present in microstrip technology. Thus, the central frequency of the backward-coupled band is controlled by the period of the EBG structure, while the frequencies of the forward-coupled bands are fixed by the length of the device. The rest of the frequencies go to the direct port giving rise to a device with the input port matched at all the frequencies and where the coupled bands are easily controllable by adjusting the corresponding design parameter. The novel methodology proposed has been successfully demonstrated by designing a triplexer intended for the GSM (900 MHz) and WLAN (2.4 GHz and 5.5 GHz) telecommunication bands.
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