Circuit model for coplanar-slotline tees

Coplanar-slotline tees have been used in a number of microwave circuits, although no complete models were available to explain their behavior. In this letter, a new “circuit-model” for a coplanar-slotline tee is presented. The model, based on the separation of coplanar waveguide (CPW) even and odd modes into two different ports, explains the tee's behavior even if CPW air bridges are not used and slotlines are loaded asymmetrically. The new model has been applied to the analysis of the input reflection coefficient of an offset-fed slotline antenna, showing an excellent agreement between simulation and measurement.Peer Reviewe

Circuit Model for mode conversion in coplanar waveguide assymmetric shunt impedances

A new `circuit model' for the conversion between even and odd modes in coplanar waveguide asymmetric shunt impedances is presented. The model is based on the separation of modes into two input and two output ports. In contrast to previous work, it allows a quantitative analysis of the energy exchange between modes.Peer Reviewe

Circuit model for a coplanar-slotline cross

A new 6-port “circuit-model” for coplanar-slotline crosses is presented. The model is based on the separation of the two fundamental Coplanar Waveguide (CPW) modes (even and odd) into different ports. It generalizes previous models since it explains the cross's behavior even if air-bridges are not used and slotlines are loaded asymmetrically. The new model is applied to the analysis of the S-parameters of an asymmetric slotline resonator, and validated through comparison with experimental results up to 40 GHz.Peer Reviewe

Compact, wideband impedance tuner using a three-line-microstrip structure

© 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.A novel three-line-microstrip compact impedance tuner is presented. It is based on a multimodal structure wherein six variable capacitances, implemented with two parallel-connected varactors each, create multiple interactions among the three-line-microstrip modes in a reduced circuit area. Experimental results show better-than-70% coverage of the Smith chart in an 85% frequency bandwidth from 1.4 to 3.2 GHz.Peer ReviewedPostprint (author's final draft

Circuit model for slotline-to-coplanar waveguide asymmetrical transitions

A new `circuit-model' for slotline-to-coplanar waveguide asymmetrical transitions is presented and applied to the design of slotline resonators. The model, based on the separation of coplanar-waveguide (CPW) modes into two different ports, overcomes limitations of previous models because it explains the transition behaviour even if CPW air-bridges are not used.Peer Reviewe

Circuit model for mode conversion in coplanar waveguide asymmetric series-impedances

A new `circuit model' for converting between even and odd modes in asymmetric series impedances in the ground plane of a coplanar waveguide is presented. The model is based on the separation of modes into two input and two output ports. In contrast to previous work, it enables a quantitative analysis of the energy exchange between modes to be obtained.Peer Reviewe

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

Enhanced robustness of a bridge-type Rf-Mems switch for enabling applications in 5G and 6G communicationsr

In this paper, new suspended-membrane double-ohmic-contact RF-MEMS switch configurations are proposed. Double-diagonal (DDG) beam suspensions, with either two or three anchoring points, are designed and optimized to minimize membrane deformation due to residual fabrication stresses, thus exhibiting smaller mechanical deformation and a higher stiffness with more release force than previously designed single diagonal beam suspensions. The two-anchor DDGs are designed in two different orientations, in-line and 90¿ -rotated. The membrane may include a window to minimize the coupling to the lower electrode. The devices are integrated in a coplanar-waveguide transmission structure and fabricated using an eight-mask surface-micro-machining process on high-resistivity silicon, with dielectric-free actuation electrodes, and including glass protective caps. The RF-MEMS switch behavior is assessed from measurements of the device S parameters in ON and OFF states. The fabricated devices feature a measured pull-in voltage of 76.5 V/60 V for the windowed/not-windowed two-anchor DDG membranes, and 54 V/49.5 V for the windowed/notwindowed three-anchor DDG membranes, with a good agreement with mechanical 3D simulations. The measured ON-state insertion loss is better than 0.7 dB/0.8 dB and the isolation in the OFF state is better than 40 dB/31 dB up to 20 GHz for the in-line/90¿ -rotated devices, also in good agreement with 2.5D electromagnetic simulationsPostprint (published version

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

Circuit model for slotline-to-coplanar waveguide asymmetrical transitions

A new 'circuit-model' for slotline-to-coplanar waveguide asymmetrical transitions is presented and applied to the design of slotline resonators. The model, based on the separation of coplanar-waveguide (CPW) modes into two different ports, overcomes limitations of previous models because it explains the transition behaviour even if CPW air-bridges are not used.Peer ReviewedPostprint (published version