Impedance Levels Research Articles

Abstract 2187: Kinetics and potency of T Cell-mediated cytolysis of glioblastoma

Abstract Glioblastoma (GBM) is an aggressive form of brain cancer that has no effective treatments and a prognosis of only 12-15 months. Immune system effector T cells are a promising therapy due to their high specificity and innate cytotoxicity. The ability to assess the efficacy and potency of T cell therapies in vitro and with high throughput is vital for the further development of this promising therapy. Cellular impedance-based assays offer a sensitive, label-free, and nondestructive method to continuously monitor cancer cell proliferation and immune cell-mediated cytotoxicity in real-time and at high throughputs, revealing not only the potency but also the kinetics of T cell therapies. Here, we investigated the targeting potency of activated human T cells on human U87MG glioma cell monolayers across multiple cell densities. U87MG cells were plated at 10k, 25k, and 50k cells per well on a PDL-coated CytoView-Z 96-well plate (n=12 wells per density), and their impedance was continuously monitored on the Maestro Z impedance platform. After 24 hours, activated patient-derived T Cells (ImmunoCult CD3/CD28 activation media) were added in a 10:1 effector:target ratio. Impedance and cytolysis were subsequently monitored for another 120 hours. As expected, higher densities proliferated faster and reached a higher impedance level at 24 hours. The addition of activated human T cells resulted in a decrease of the impedance signal consistent with T cell-mediated lysis of the glioma cells. The highest density of T cells (500k) exhibited the fastest rate of U87 cytolysis, with a Kill Time 50 of 35 hours. All densities reached 100% cytolysis by 100 hours. Overall, activated human T cells were highly effective for cytolysis of U87MG glioma cell monolayers of varying densities. The cellular impedance assay revealed high potency, with kinetics that varied across cell densities despite the same effector:target ratios. Citation Format: Stacie A. Chvatal, Meghan T. Logun, Heather B. Hayes, Daniel C. Millard, Lohitash Karumbaiah. Kinetics and potency of T Cell-mediated cytolysis of glioblastoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2187.

Use of Impedance Spectroscopy for the Characterization of In-Vitro Osteoblast Cell Response in Porous Titanium Bone Implants

The use of titanium implants with adequate porosity (content, size and morphology) could solve the stress shielding limitations that occur in conventional titanium implants. Experiments to assess the cellular response (adhesion, proliferation and differentiation of osteoblasts) on implants are expensive, time-consuming and delicate. In this work, we propose the use of impedance spectroscopy to evaluate the growth of osteoblasts on porous titanium implants. Osteoblasts cells were cultured on fully-dense and 40 vol.% porous discs with two ranges of pore size (100–200 μm and 355–500 μm) to study cell viability, proliferation, differentiation (Alkaline phosphatase activity) and cell morphology. The porous substrates 40 vol.% (100–200 µm) showed improved osseointegration response as achieved more than 80% of cell viability and higher levels of Cell Differentiation by Alkaline Phosphatase (ALP) at 21 days. This cell behavior was further evaluated observing an increase in the impedance modulus for all study conditions when cells were attached. However, impedance levels were higher on fully-dense due to its surface properties (flat surface) than porous substrates (flat and pore walls). Surface parameters play an important role on the global measured impedance. Impedance is useful for characterizing cell cultures in different sample types.

Influence of swelling level on charge transmission of chitosan and reduced graphene oxide film electrodes

Chitosan film (CS) and thermally reduced graphene oxide (rGO) are materials used for sensorial devices. However, the high level of swelling, characteristic of CS, coupled with unstable electrochemical measurements, reduces its application. Thus, the swelling effects of CS_rGO films obtained by CS and rGO acetic hydrogel subjected to surface neutralization with ethanol and base were investigated. Their morphological, chemical and electrochemical properties were compared. The untreated CS-rGO showed higher impedance due to the high degree of swelling that led to physical-chemical changes that compromised its efficiency. The neutralization treatments contributed to the reduction of the level of swelling and the formation of more capacitive films, preserving the electrostatic interaction between the functional groups of CS and rGO and maximizing the mobility of charges. Thus, the reduction in swelling, mainly facilitated after treatment with ethanol, presented the lowest impedance and swelling levels among all methods, being suitable for electrode compositions.

Autonomous Monitoring of Line-to-Line Faults in Photovoltaic Systems by Feature Selection and Parameter Optimization of Support Vector Machine Using Genetic Algorithms

Photovoltaic (PV) monitoring and fault detection are very crucial to enhance the service life and reliability of PV systems. It is difficult to detect and classify the faults at the Direct Current (DC) side of PV arrays by common protection devices, especially Line-to-Line (LL) faults, because such faults are not detectable under high impedance fault and low mismatch conditions. If these faults are not diagnosed, they may significantly reduce the output power of PV systems and even cause fire catastrophe. Recently, many efforts have been devoted to detecting and classifying LL faults. However, these methods could not efficiently detect and classify the LL faults under high impedance and low mismatch. This paper proposes a novel fault diagnostic scheme in accordance with the two main stages. First, the key features are extracted via analyzing Current–Voltage (I–V) characteristics under various LL fault events and normal operation. Second, a genetic algorithm (GA) is used for parameter optimization of the kernel functions used in the Support Vector Machine (SVM) classifier and feature selection in order to obtain higher performance in diagnosing the faults in PV systems. In contrast to previous studies, this method requires only a small dataset for the learning process and it has a higher accuracy in detecting and classifying the LL fault events under high impedance and low mismatch levels. The simulation results verify the validity and effectiveness of the proposed method in detecting and classifying of LL faults in PV arrays even under complex conditions. The proposed method detects and classifies the LL faults under any condition with an average accuracy of 96% and 97.5%, respectively.

Intraoperative Cochlear Implant Reinsertion Effects Evaluated by Electrode Impedance.

To assess the effect on impedance levels of intraoperative reinsertion of a cochlear implant (CI) array compared with matched controls. Retrospective patient review. Cochlear implant center. CI recipients in the Sydney Cochlear Implant Centre (SCIC) database who required intraoperative array reinsertion and matched controls. Exclusion criteria; known preceding meningitis or labyrinthitis ossificans; electrode array buckling; incomplete "final" insertion. Cochlear implantation. Impedance values measured intraoperatively, at switch on, 3 months, 6 months, and 12 months postoperatively were analyzed. The Generalized Estimating Equation (GEE) Model was used to compare cases with controls for each device, at each time point, and for each channel. Thirty-one reinsertion cases identified; six CI 422 arrays; 14 CI 24RE (ST) arrays, and 11 CI 512 arrays. No increase in impedance levels was found in the reinsertion cases when compared with their matched controls. The only statistical difference in impedance was seen in the CI 422 cohort at switch on with the reinsertion cases having lower impedances (p = 0.03). This is the first study to examine impedance values in patients who underwent intraoperative CI array reinsertion and to compare them with the impedances of matched controls. No significant increase found in impedances between our reinsertion cases and matched controls, suggesting the reinsertion did not result in any additional trauma or inflammation. This has implications for surgery both in routine cases such as a faulty electrode and also for future design of mechanisms for delivery of intracochlear therapies.

MicroRNAs and ventricular remodeling in aortic stenosis

Introduction and ObjectivesSeveral mechanisms contribute to myocardial hypertrophy and fibrosis in aortic stenosis (AS). MicroRNAs are post-transcriptional modulators of such processes. We hypothesized that their expression in myocardial biopsies from patients with AS could be linked with the degree of left ventricular (LV) hypertrophy and remodeling and to plasma levels of important biomarkers of extracellular matrix turnover. MethodsWe performed myocardial biopsies in eleven patients with isolated severe AS undergoing aortic valve replacement. Echocardiographic exams and biomarker quantification were also performed. Five explanted hearts were used as controls for microRNA expression. ResultsOverexpression of microRNA-101-3p was found in AS, which correlated with higher levels of preoperative valvuloarterial impedance, angiotensin II receptor and angiotensin-converting enzyme, and LV mass regression after surgery. Although not differently expressed in AS compared to controls, both upregulation of miR-4268 and downregulation of microRNA-125-5p were associated with higher LV mass. MicroRNA-125b-5p correlated negatively with LV mass and with relative wall thickness at six-month follow-up. MicroRNA-4268 correlated positively with LV mass regression and was associated with higher plasma angiotensin II receptor levels. ConclusionsMicroRNA-101-3p and microRNA-4268 have potential new roles in the modulation of the hypertrophic response to AS via the renin-angiotensin-aldosterone system and as predictors of reverse remodeling after aortic valve replacement. Our results open new avenues in the understanding of myocardial response to pressure overload and of reverse remodeling after unloading. They also support the possibility of medical therapy to modulate the renin-angiotensin-aldosterone system in hypertrophic hearts.

Task-based hybrid shared control for training through forceful interaction

Despite the fact that robotic platforms can provide both consistent practice and objective assessments of users over the course of their training, there are relatively few instances where physical human–robot interaction has been significantly more effective than unassisted practice or human-mediated training. This article describes a hybrid shared control robot, which enhances task learning through kinesthetic feedback. The assistance assesses user actions using a task-specific evaluation criterion and selectively accepts or rejects them at each time instant. Through two human subject studies (total ), we show that this hybrid approach of switching between full transparency and full rejection of user inputs leads to increased skill acquisition and short-term retention compared with unassisted practice. Moreover, we show that the shared control paradigm exhibits features previously shown to promote successful training. It avoids user passivity by only rejecting user actions and allowing failure at the task. It improves performance during assistance, providing meaningful task-specific feedback. It is sensitive to initial skill of the user and behaves as an “assist-as-needed” control scheme, adapting its engagement in real time based on the performance and needs of the user. Unlike other successful algorithms, it does not require explicit modulation of the level of impedance or error amplification during training and it is permissive to a range of strategies because of its evaluation criterion. We demonstrate that the proposed hybrid shared control paradigm with a task-based minimal intervention criterion significantly enhances task-specific training.

Changes in Pharyngeal Baseline Impedance in Patients With Laryngopharyngeal Reflux.

Few studies have investigated pharyngeal intraluminal baseline impedance (BI) levels in patients with laryngopharyngeal reflux (LPR). The aim of this study was to compare intraluminal BI levels between patients with LPR and healthy controls. Retrospective case series. Tertiary care medical center. We conducted a retrospective analysis of 24-hour multichannel intraluminal impedance (MII)-pH monitoring results from patients with suspected LPR complaining of reflux symptoms. Patients with suspected LPR were divided into 2 groups according to the 24-hour MII-pH monitoring (LPR group: patients with symptoms with reflux events ≥1, symptom but no reflux [SNR] group: patients with symptoms but no reflux event). Healthy controls were recruited and also underwent 24-hour MII-pH monitoring. We compared the esophageal and pharyngeal BI levels and ratios between 3 groups. Pharyngeal BI levels in the LPR group were significantly higher than in the healthy controls. In addition, the pharyngeal BI levels in the SNR group were significantly higher than in the healthy controls. All ratios of pharyngeal to distal esophageal BI levels in the LPR and SNR group were significantly higher than in the healthy controls. However, there were no significant differences in esophageal BI levels and ratios between the 3 groups. We found that the pharyngeal BI levels were higher in patients with LPR than in healthy controls. In addition, the pharyngeal BI levels measured by 24-hour MII-pH monitoring in patients with LPR symptoms, but without a reflux episode, were higher than in the healthy controls.

Kinetics and potency of T Cell-mediated cytolysis of glioblastoma

Abstract Glioblastoma is an aggressive brain cancer with no effective treatments and a prognosis of 12–15 months. Immune system effector T cells are a promising therapy due to their high specificity and innate cytotoxicity. Assessing the efficacy and potency of T cell therapies in vitro and with high throughput is vital for development of this promising therapy. Cellular impedance-based assays offer sensitive, label-free, and continuous monitoring of cell proliferation and immune cell-mediated cytotoxicity, revealing both the potency and kinetics of T cell killing. Here, we investigated the targeting potency of activated human T cells on human U87MG glioma and patient-derived glioma cells. U87MG and patient-derived glioma cells were plated at densities ranging from 10k to 50k cells per well on a PDL-coated CytoView-Z 96-well plate (n=12 wells per density). After 24 hours, activated patient-derived T Cells (ImmunoCult CD3/CD28 activation media) were added in a 10:1 effector:target ratio. Impedance and cytolysis were continuously monitored for over 120 hours. As expected, higher densities of glioma cells proliferated faster and reached a higher impedance level at 24 hours. Addition of activated human T cells resulted in a decrease in impedance consistent with T cell-mediated lysis of the glioma cells. The highest density of T cells (500k) exhibited the fastest rate of U87 cytolysis, with a Kill Time 50 of 35 hours. All densities reached 100% cytolysis by 100 hours. Overall, activated human T cells were highly effective for cytolysis of U87MG and patient-derived glioma cells. The cellular impedance assay revealed high potency, with kinetics that varied across cell densities despite the same effector:target ratios.

Kinetics and potency of T Cell-mediated cytolysis of glioblastoma

Background & Aim Glioblastoma is an aggressive brain cancer with no effective treatments and a prognosis of 12-15 months. Immune system effector T cells are a promising therapy due to their high specificity and innate cytotoxicity. Assessing the efficacy and potency of T cell therapies in vitro and with high throughput is vital for development of this promising therapy. Cellular impedance-based assays offer sensitive, label-free, and continuous monitoring of cell proliferation and immune cell-mediated cytotoxicity, revealing both the potency and kinetics of T cell killing. Here, we investigated the targeting potency of activated human T cells on human U87MG glioma and patient-derived glioma cells. Methods, Results & Conclusion U87MG and patient-derived glioma cells were plated at densities ranging from 10k to 50k cells per well on a PDL-coated CytoView-Z 96-well plate (n=12 wells per density). After 24 hours, activated patient-derived T Cells (ImmunoCult CD3/CD28 activation media) were added in a 10:1 effector:target ratio. Impedance and cytolysis were continuously monitored for over 120 hours. As expected, higher densities of glioma cells proliferated faster and reached a higher impedance level at 24 hours. Addition of activated human T cells resulted in a decrease in impedance consistent with T cell-mediated lysis of the glioma cells. The highest density of T cells (500k) exhibited the fastest rate of U87 cytolysis, with a Kill Time 50 of 35 hours. All densities reached 100% cytolysis by 100 hours. Overall, activated human T cells were highly effective for cytolysis of U87MG and patient-derived glioma cells. The cellular impedance assay revealed high potency, with kinetics that varied across cell densities despite the same effector:target ratios.

Mitigating the Effects of Electrode Biofouling-Induced Impedance for Improved Long-Term Electrochemical Measurements In Vivo.

Biofouling is a prevalent issue in studies that involve prolonged implantation of electrochemical probes in the brain. In long-term fast-scan cyclic voltammetry (FSCV) studies, biofouling manifests as a shift in the peak oxidative potential of the background signal that worsens over days to weeks, diminishing sensitivity and selectivity to neurotransmitters such as dopamine. Using open circuit potential (OCP) measurements, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), and electrochemical impedance spectroscopy (EIS), we examined the biofouling-induced events that occur due to electrode implantation. We determined that the FSCV background signal shift results from cathodic polarization of the Ag/AgCl-wire reference electrode and increased electrochemical impedance of both the Ag/AgCl-wire reference electrode and carbon-fiber working electrode. These events are likely caused collectively by immune response-induced electrode encapsulation. A headstage utilizing a three-electrode configuration, designed to compensate for the impedance component of biofouling, reduced the FSCV background signal shift in vivo and preserved dopamine sensitivity at artificially increased impedance levels in vitro. In conjunction with a stable reference electrode, this three-electrode configuration will be critical in achieving reliable neurotransmitter detection for the duration of long-term FSCV studies.

Cochlear Implant Mapping Through Telemedicine—A Feasibility Study

Access to postoperative aural rehabilitation limits cochlear implant (CI) penetration to the candidate population. The purpose of this study was to evaluate the effectiveness of remote CI programming and aural rehabilitation via telehealth. Retrospective study of one cochlear implant center. Patients undergoing cochlear implantation from 2015 to 2018 undergoing remote programming as part of routine audiologic follow up. AzBio scores, impedances, comfort and threshold levels, and responses to the International Outcome Inventory for Hearing Aids questionnaire modified for CIs (IOI-CI). A total of 22 CIs in 20 patients were included during the study period. Threshold, comfort, and impedance levels were readily obtained via telehealth and were not significantly different between telehealth and live sessions. AzBio scores and warble tone pure tone averages were also similar and acceptable in both session modalities. Based on IOI-CI scores, patients were very satisfied with their hearing outcomes. Using telemedicine, reliable measurements were readily obtained and hearing outcomes after remote programming were comparable to those expected after in-person programming sessions. Patients were overall satisfied with their remote programming sessions. Telehealth is a cost-effective and safe way to deliver post-CI audiologic care, particularly to patients with limited mobility or those in remote locations.

Electrode impedance changes over time in MED El cochlear implant children recipients: Relation to stimulation levels and behavioral measures

Objective: Electrode impedance measures resistance encountered by electric current passing through wires, electrodes and biological tissue. This study was designed mainly to evaluate changes in electrode impedance values and psycho-electric parameters changes (i.e. threshold levels, comfortable levels, and dynamic range) in cochlear implant patients over time. Methods: It was a prospective study encompassing 20 patients implanted by MED-EL device programd using behavioral programs. Electrical stimulation levels and electrode impedance values were examined at 0, 1, 3 and 6 months after the first fitting session. Results: Electrode impedance values were reduced from the time of activation to the 6 months visit. Most comfortable levels increased and dynamic range widened until the 6 months visit. There was an inverse correlation between impedance values and most comfortable level as well as dynamic range, over time. Conclusion: Frequent monitoring of electrode impedance (for device and electrodes problems) and electric stimulation levels (for better performance, mapping and habituation) during the first 6 months of implant use is recommended.

Impact of sex hormone-binding globulin on the human phenome.

Background: Sex hormone-binding globulin (SHBG) is a circulating glycoprotein and a regulator of sex hormone levels, which has been shown to influence various traits and diseases. The molecular nature of SHBG makes it a feasible target for preventative or therapeutic interventions. A systematic study of its effects across the human phenome may uncover novel associations. Methods: We used a Mendelian randomization phenome-wide association study (MR-pheWAS) approach to systematically appraise the potential functions of SHBG while reducing potential biases such as confounding and reverse causation common to the literature. We searched for potential causal effects of SHBG in UK Biobank (N = 334 977) and followed-up our top findings using two-sample MR analyses to evaluate whether estimates may be biased due to horizontal pleiotropy. Results: Results of the MR-pheWAS across over 21 000 outcome phenotypes identified 12 phenotypes associated with genetically elevated SHBG after Bonferroni correction for multiple testing. Follow-up analysis using two-sample MR indicated the associations of increased natural log SHBG with higher impedance of the arms and whole body, lower pulse rate, lower bone density, higher odds of hip replacement, lower odds of high cholesterol or cholesterol medication use and higher odds of gallbladder removal. Conclusions: Our systematic MR-pheWAS of SHBG, which was comprehensive to the range of phenotypes available in UK Biobank, suggested that higher circulating SHBG affects the body impedance, bone density and cholesterol levels, among others. These phenotypes should be prioritized in future studies aiming to investigate the biological effects of SHBG or develop targets for therapeutic intervention.

Impact of Supply Voltage Unbalance and Harmonics on dc Bus Electrolytic Capacitor of Adjustable Speed Drives

Among the various supply voltage abnormalities, unbalance and distortion are some of the major threats to the dc bus capacitor of adjustable speed drives. The effect of supply voltage unbalance on the dc bus capacitor changes in the presence of supply voltage harmonics. Further, the value of grid impedance and the load on the drive influences the response of these supply voltage abnormalities on the dc bus capacitor. This article analyzes the impact of unbalance, distortion, and simultaneous presence of unbalance and distortion in the supply voltage, on the dc bus capacitor, along with the effect of grid impedance and the load on the drive. As a result of the analysis, the article proposes the derating of load required to keep the capacitor current within the safe value irrespective of the level of abnormalities and grid impedance. The effects are analyzed by simulations and validated by the hardware test setup.

Postoperative dynamics of electrode impedance changes in children with cochlear implants

75 patients with a bilateral sensorineural deafness aged from 1 to 4 years (average age - 1.5 years) were included in the study. 50 patients were implanted with Nucleus cochlear implants (Cochlear - Australia) and other 25 patients - with Advanced Bionics implants (Switzerland). The impedance dynamics analysis in two groups of patients implanted with «Cochlear» and «Advanced Bionics» cochlear implants demonstrated that statistically significant decrease in impedance (p<0.05) was observed after the beginning of electrical stimulation and the reduction of postoperative inflammatory process in the inner ear. The stabilization of the impedance levels in both groups of patients was obtained in 3-6 months after the switch-on of speech processor.

Design of Broadband Doubly Asymmetrical Branch-Line Directional Couplers

An analytic broadband design method for four-port N-branch branch-line couplers with outputs terminated by arbitrary impedances is given. An alternative, more practical design method has also been included, which avoids impedance discontinuities in the branches and retrieves the outputs-in-quadrature property lost in the asymmetrization. The doubly asymmetrical couplers so obtained are then used in a proposed design methodology for three-way power dividers that can include, if desired, an impedance level transformation. This article relies on the analysis of a class of asymmetrical structures by means of the odd and even excitations. Therefore, the formalization of this analysis is also detailed.

Measurement and Analysis of Passive Intermodulation Induced by Additional Impedance in Loose Contact Coaxial Connector

The mechanism of the passive intermodulation (PIM) distortion caused by the loose contact in coaxial connectors is of great importance in wireless communication systems. This paper focuses on the effect of the additional impedance on PIM levels in coaxial connectors. First, the additional impedance and PIM levels of the loose contact coaxial connectors are measured. Then, the S-parameters and the additional impedance with three different loose contact cases are simulated. Finally, a modified coaxial connector with different values of conductive tapes is designed to verify the additional impedance impacts on the PIM level. It is shown that the increase of the additional impedance of the metal–metal loose contact will lead to the deterioration of PIM levels in the coaxial connector.

Global and Regional Respiratory Mechanics During Robotic-Assisted Laparoscopic Surgery: A Randomized Study.

Pneumoperitoneum and nonphysiological positioning required for robotic surgery increase cardiopulmonary risk because of the use of larger airway pressures (Paws) to maintain tidal volume (VT). However, the quantitative partitioning of respiratory mechanics and transpulmonary pressure (PL) during robotic surgery is not well described. We tested the following hypothesis: (1) the components of driving pressure (transpulmonary and chest wall components) increase in a parallel fashion at robotic surgical stages (Trendelenburg and robot docking); and (2) deep, when compared to routine (moderate), neuromuscular blockade modifies those changes in PLs as well as in regional respiratory mechanics. We studied 35 American Society of Anesthesiologists (ASA) I-II patients undergoing elective robotic surgery. Airway and esophageal balloon pressures and respiratory flows were measured to calculate respiratory mechanics. Regional lung aeration and ventilation was assessed with electrical impedance tomography and level of neuromuscular blockade with acceleromyography. During robotic surgical stages, 2 crossover randomized groups (conditions) of neuromuscular relaxation were studied: Moderate (1 twitch in the train-of-four stimulation) and Deep (1-2 twitches in the posttetanic count). Pneumoperitoneum was associated with increases in driving pressure, tidal changes in PL, and esophageal pressure (Pes). Steep Trendelenburg position during robot docking was associated with further worsening of the respiratory mechanics. The fraction of driving pressures that partitioned to the lungs decreased from baseline (63% ± 15%) to Trendelenburg position (49% ± 14%, P < .001), due to a larger increase in chest wall elastance (Ecw; 12.7 ± 7.6 cm H2O·L) than in lung elastance (EL; 4.3 ± 5.0 cm H2O·L, P < .001). Consequently, from baseline to Trendelenburg, the component of Paw affecting the chest wall increased by 6.6 ± 3.1 cm H2O, while PLs increased by only 3.4 ± 3.1 cm H2O (P < .001). PL and driving pressures were larger at surgery end than at baseline and were accompanied by dorsal aeration loss. Deep neuromuscular blockade did not change respiratory mechanics, regional aeration and ventilation, and hemodynamics. In robotic surgery with pneumoperitoneum, changes in ventilatory driving pressures during Trendelenburg and robot docking are distributed less to the lungs than to the chest wall as compared to routine mechanical ventilation for supine patients. This effect of robotic surgery derives from substantially larger increases in Ecw than ELs and reduces the risk of excessive PLs. Deep neuromuscular blockade does not meaningfully change global or regional lung mechanics.

Contra-Directional Ridge Waveguide Couplers: Design and Applications

This article presents novel wideband contra-directional couplers based on single conductor ridge waveguide, and their applications. The couplers exhibit wide bandwidths and tight coupling while occupying very small volume due to the compactness of ridge waveguides. The methodology to design the couplers is presented. It is inspired by the even and odd modes used to design TEM coupled lines couplers but implemented with TE modes in this novel approach. The design starts with designing the coupling section in a quadruple-ridge waveguide that supports two independent even and odd TE modes. Proper choice of the cross section allows the designer to achieve the required impedance levels for the required coupling values. An S-band proof of concept prototype of a single coupler was synthesized, fabricated, and tested, demonstrating excellent measured results without any tuning. The couplers can be exploited in versatile applications, such as power sampling, beamforming, or high-power combiners. As an additional proof of concept design, a C-band three-way combiner was also designed and tested, showing the potential of the novel coupler for different applications.