Compact fully uniplanar bandstop filter based on slow-wave multimodal CPW resonators

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this letter, a compact, fully uniplanar bandstop filter is presented. It is based on multimodal coplanar waveguide resonators implemented using a slow-wave periodic structure that greatly reduces the filter’s horizontal dimension. A multimodal circuit model for the filter is proposed and experimentally validated. A second-order filter prototype at 1.9 GHz, with a compact size of 0.31¿g×0.19¿g , was designed and fabricated. The filter features measured fractional bandwidths of 9.3% and 3.7% for -20- and -30-dB rejection levels, respectively, and a 1.3-dB insertion loss in the passband.Peer ReviewedPostprint (author's final draft

RF-MEMS switches for a full control of the propagating modes in uniplanar microwave circuits and their application to reconfigurable multimodal microwave filters

This is a copy of the author 's final draft version of an article published in the journal Microsystem technologies. The final publication is available at Springer via http://dx.doi.org/10.1007/s00542-017-3379-8In this paper, new RF-MEMS switch configurations are proposed to enable control of the propagating (even and odd) modes in multimodal CPW transmission structures. Specifically, a switchable air bridge (a switchable short-circuit for the CPW odd mode) and switchable asymmetric shunt impedances (for transferring energy between modes) are studied and implemented using bridge-type and cantilever-type ohmic-contact switches, respectively. The switchable air bridge is based in a novel double ohmic-contact bridge-type structure. Optimized-shape suspension configurations, namely folded-beam or diagonal-beam for bridge-type switches, and straight-shaped or semicircular-shaped for cantilever-type switches, are used to obtain robust structures against fabrication-stress gradients. The switches are modelled using a coupled-field 3D finite-element mechanical analysis showing a low to moderate pull-in voltage. The fabricated switches are experimentally characterized using S-parameter and DC measurements. The measured pull-in voltages agree well with the simulated values. From S-parameter measurements, an electrical model with a very good agreement for both switch states (ON and OFF) has been obtained. The model is used in the design of reconfigurable CPW multimodal microwave filters.Peer ReviewedPostprint (author's final draft

Compact Inline E plane Waveguide Resonators and Bandpass Filters with I-shaped Resonant Insets

In this paper, waveguide resonators and bandpass filters with E-plane inserts containing I-shaped resonant insets are presented. These insets introduce to the response finite transmission zeros much less sensitive than those produced by cross-couplings. Also, their use results in structure compactness, unlike bandstop resonant cavities that add volume. Two kinds of extracted pole sections that demonstrate response flexibility of the proposed resonators are designed at 10 GHz and tested. One is based on the dominant mode with a transmission zero in the upper stopband and the other on a pair of higher order modes with a transmission zero in the lower stopband. Also, a 3rd order filter for 11 GHz band combining both dominant and higher order mode resonators is modeled to illustrate the scalability of such a modular design. These filters are very suitable for low-cost mass production

The Design of an Anti-Aliasing Filter for the Next Generation Digitiser

MeerKAT, is a 64-element radio astronomy antenna array which has been recently constructed in the Northern Cape Province of South Africa. It serves as South Africa's contribution towards the international Square Kilometre Array (SKA) project. The MeerKAT array has been designed to observe radio signals produced by celestial sources at UHF-Band, L-Band, S-Band and X-Band frequencies. The first phase of the construction included the design, development and integration of the UHF-Band, L-Band and S-band Receivers, whilst the X-band design has been superseded by the incorporation of the next phase of the SKA international project. In preparation of the next the roll-out, research is required to determine optimal wideband filter topologies suitable for direct digitisation of signal frequencies over the frequency range of 3-6 GHz. In this thesis, exploration of suitable wideband planar filters is performed, noting those with an improved out-of-band rejection. The outcome of the investigation leads into the design and development of the suitable wideband planar filter based on key performance specifications. The performance of the manufactured wideband planar filter is then compared to the theoretical design, and validated against the key performance requirements

A π-CLCL Type Immittance Converter for Constant Current and Dynamic Load Applications

Impedance-admittance converter is shortly termed as immittance converter. In this converter, the output current is proportional to the input voltage and the output voltage is proportional to the input current. The output current is thus independent of the load. This research evaluates the characteristics of a proposed π-CLCL immittance converter, which is a combination of the typical π- and T-type configurations, for constant current and dynamic load applications. The input-output characteristics and efficiency characteristics are analyzed and simulated. The characteristics are compared to that of the typical π- and T-type converters. The input-output characteristics and efficiency characteristics are then examined experimentally. It is observed that the experimental results agree with those of the simulation ones, and confirm that the π-CLCL configuration is more efficient than the typical π- and T-type immittance converters while maintaining a nearly constant output current and thus applicable for dynamic loads.DOI:http://dx.doi.org/10.11591/ijece.v4i5.595

RF-MEMS Switches Designed for High-Performance Uniplanar Microwave and mm-Wave Circuits

Radio frequency microelectromechanical system (RF-MEMS) switches have demonstrated superior electrical performance (lower loss and higher isolation) compared to semiconductor-based devices to implement reconfigurable microwave and millimeter (mm)-wave circuits. In this chapter, electrostatically actuated RF-MEMS switch configurations that can be easily integrated in uniplanar circuits are presented. The design procedure and fabrication process of RF-MEMS switch topologies able to control the propagating modes of multimodal uniplanar structures (those based on a combination of coplanar waveguide (CPW), coplanar stripline (CPS), and slotline) will be described in detail. Generalized electrical (multimodal) and mechanical models will be presented and applied to the switch design and simulation. The switch-simulated results are compared to measurements, confirming the expected performances. Using an integrated RF-MEMS surface micromachining process, high-performance multimodal reconfigurable circuits, such as phase switches and filters, are developed with the proposed switch configurations. The design and optimization of these circuits are discussed and the simulated results compared to measurements

Dual Mode Suspended Substrate Stripline (SSS) Filter

Evolution of wireless communication systems towards high flexibility, low cost and high efficiency leads to tremendous activity in the area of microwave filters. In an RF front-end of a cellular radio base station, signals are being transmitted and received simultaneously. In the receive band, there are chances of intermodulation products from the power amplifier being fed to the receiver,thus the transmit filter must have a very high level of signal rejection. Furthermore, the transmit filter must also have low passband insertion loss since it impacts the power transmitted and the overall transmit system efficiency. Recently, filters with dual-mode operation were being investigated due to their ability to produce two degenerate modes using a single physical structure; therefore, the size and cost of the filter can be reduced without compromising any figure-of-merits. A dual mode suspended substrate stripline filter is presented in this thesis. These filters enable achieving low insertion loss, high Q, high selectivity and good spurious response. Initially, a dual mode ring resonator structure is investigated using suspended substrate stripline technology. This technology is used due to its advantages which are comparable to microstrip or any other planar transmission lines. The HFSS three dimensional finite element method (FEM) is used to evaluate the resonant frequency, quality factor and the first harmonics.A second order suspended substrate stripline filter was designed with capacitive coupled input and output feeding method. The input and output feed were positioned 90 degree from each other while a notch was used in this filter to couple two degenerate modes which also control the bandwidth of the filter. A high performance Generalized Chebychev filter was designed to meet the stringent electrical requirement in the RF front-end of a cellular radio base station. With this fourth order filter, four finite frequency transmission zeros were achieved due to phase cancellation between two paths which results in high selectivity filter response. Metal tuning screws were added to improve any practical imperfections. Finally an asymmetrical Generalized Chebychev filter was designed with real frequency transmission zeros positioned on one side of the passband. With this design, the aim of achieving higher selectivity filter response above the passband was demonstrated

Some theoretical aspects of immittance conversion and inversion in the context of active RC networks

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