Coaxial Connectors Research Articles

MIMO Antenna System With Pattern Diversity for Sub-6 GHz Mobile Phone Applications

A MIMO antenna system is designed and presented for sub-6 GHz mobile phone applications. The proposed antenna design consists of six loop-type radiation elements. From the six elements, four elements are placed at the corners of the mobile phone PCB by following pattern diversity configuration, while the rest of the two elements are placed in the center of the PCB. Furthermore, a $50\Omega $ coaxial connector is utilized to feed the antenna elements. From the presented results, it is demonstrated that the elements placed at the edges are resonating at 2.5 GHz, and the center placed elements provide resonance at 3.5 GHz. Moreover, according to S11 ≤ −6 dB, the impedance bandwidth for both the bands is 790 MHz (2.3-3.09 GHz) and 1.18 GHz (2.99-4.17 GHz), respectively; while for S11 ≤ −10 dB, the impedance bandwidth for both the bands is noted to be 340 MHz (2.38-2.72 GHz) and 650 MHz (3.17–3.84 GHz), respectively. A gain of more than 4 dBi and >85% radiation efficiency are achieved for the single radiation element. The presented antenna design also provides sufficient radiation coverage supporting different sides of the mobile phone PCB. In addition, the effects of the human hand and head on antenna’s performance are studied and it was observed that the proposed antenna system provides acceptable properties in the data mode and talk mode.

Measurement methods and mathematical model of main characteristics of waveguide-coaxial connectors

Modern complex microwave radio electronic systems may use functional devices implemented on different types of transmission lines. In order to connect such devices to each other to form antenna feed system, the following three types of special connectors can be used: coaxial, waveguide, and combined microwave devices based on waveguide and coaxial segments. The main electrical characteristics of waveguide coaxial connectors (WCC) are the losses introduced by the device to the antenna feed and matching with the regular microwave path (voltage standing-wave ratio, VSWR). Standard methods and standard equipment used to measure the characteristics of coaxial or waveguide connectors cannot be applied to WCCs. This article proposes a method designed to measure the main characteristics of waveguide-coaxial connectors and presents their mathematical model (wave matrices). The proposed methods of measuring microwave characteristic are demonstrated on the example of waveguide coaxial connectors of longitudinal coaxial type. It should be noted that the proposed technique has been experimentally tested on a number of specific devices. Not only the waveguide coaxial connectors have been studied in different frequency ranges (waveguide sizes from 23×5 to 58×25 mm), but also with different coaxial channel designs (sizes 3.5/1.52; 6.0/2.6 and 7.0/3.04 mm). The proposed method provides replicable measurements results of the characteristics of waveguide coaxial connectors, which confirms its reliability.

Accounting of the parasitic effects during measurement of the effective permittivity using the quarter-wavelength resonator method

The analysis, approximations and accounting of the influence of the main parasitic effects that affect the results of the measurement are provided in this paper. The method of dielectric constant measurement of coaxial connectors support beads is suggested. The comparison between the acquired results using the suggested method and the reference is made. The results suggest that the method can be used for dielectric constant measurement of the coaxial connector support beads with the accuracy comparable to the method of the volume resonator for rod samples H01p by GOST 8.623-2015.

Novel Miniaturized All-Metal UWB Magneto-Electric Monopole (MEM) Antenna for Multistandard Applications

We propose a novel miniaturized all-metal ultrawideband (UWB) magneto-electric monopole (MEM) antenna in this communication. The proposed antenna is composed of a half-ellipse electric monopole and a quarter magnetic loop. The half-ellipse electric monopole consists of a half ellipse with a rectangular slot, a loaded patch, and an L-shape ground fed by a coaxial connector. Enhanced robustness to severe surrounding environments and lower loss can be achieved by employing an all-metal structure instead of the structure including dielectric materials. A prototype was fabricated and measured. Results show that the proposed MEM antenna can operate in the frequency band of 2.5-13 GHz even higher frequency with the miniaturized dimensions of 0.25λ×0.24λ×0.17λ that is much smaller than a magneto-electric dipole. A unidirectional wide beam radiation pattern with a 10 dB front to back ratio can be obtained. Moreover, the group delay is analyzed which reveals the antenna with good time domain characteristics. The proposed MEM antenna can be employed as a multifunctional antenna operating for multistandard communication networks in a limited space.

Directive 2-D Beam Steering by Means of a Multiport Radially Periodic Leaky-Wave Antenna

A multifed radially periodic two-dimensional leaky-wave antenna is proposed for the generation of a directional beam continuously scanning in elevation by changing the frequency, and over a discrete number of directions in azimuth when activating different elements of the feeding system. The structure is planar and constituted by a circular grounded dielectric slab loaded with microstrip rings, properly positioned around the sources to support the propagation of an angularly directional surface wave over a sector determined by the corresponding activated feeder. This produces a perturbation of the surface wave, resulting in the generation of a directional leaky wave over the aperture, whose complex propagation constant is described by a single fast backward spatial harmonic. The antenna radiation features are numerically investigated in conjunction with the dispersion analysis of the structure, validated through a conventional generalized-pencil-of-function approach. Full-wave simulations have been developed to design a practical feeder, which is constituted by a circular arrangement of commercial coaxial connectors. The proposed multiport antenna is validated by means of measurements performed on a microwave manufactured prototype. The design represents an attractive simple and cost-effective solution to achieve a high-gain beam scanning over the three-dimensional space, alternative to more conventional phased-array design based on cumbersome and lossy feeding networks.

Flexible Meander-Line Antenna Array for Wearable Electromagnetic Head Imaging

Portable lightweight electromagnetic (EM) head imaging systems for brain stroke detection are of great interest due to the need for fast and low-cost diagnosis tools. This communication presents a wideband and compact flexible meander-line antenna array for a wearable EM head imaging system. The antenna is designed and optimized on a 4 mm thick low-cost, flexible room-temperature-vulcanizing (RTV) silicone substrate in close vicinity to a multitissue head model. The antenna comprises two sections of meander-lines, a full ground plane, and a 50 Ω coaxial connector. The measured reflection coefficient |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | on a human head shows that the proposed antenna operates effectively across the frequency band of 0.45-3.6 GHz, attaining fractional bandwidth (FBW) of 155%. The antenna achieves unidirectional radiations with greater than 9 dB of front-to-rear ratio in the near-field region, and safe-level maximum specific-absorption rate (SAR) below 0.2 W/kg using an input power of 10 dBm. A 16 element antenna array was assembled and experimentally utilized in an EM head imaging system. The reconstructed images of abnormality-emulating targets using a confocal imaging algorithm demonstrate the feasibility of utilizing such flexible and lightweight antennas for wearable EM head imaging systems.

Modeling of Signal Distortion Caused by Passive Intermodulation and Cross Modulation in Coaxial Connectors

Coaxial connectors play an important role in communication systems. However, passive intermodulation (PIM) and cross modulation resulting from slight nonlinear characteristics in coaxial connectors may negatively impact signal transmission quality. In addition, degradation of coaxial connectors tends to exacerbate such effects. In this work, the nonlinear characteristics of pristine coaxial connectors are analyzed and modeled. From these results, a new polynomial behavior model is developed to describe the nonlinear characteristics for connectors with various levels of degradation for the first time. A series of two-tone PIM tests on pristine connectors and degraded connectors is conducted with the input power from 35 to 44 dBm. The test results validate the model for pristine connectors and the model for connectors with various levels of degradation. The error vector magnitude (EVM) is selected as the index to quantify the level of signal distortion. The power of PIM and cross modulation interference and the impacts of PIM and cross modulation on EVM are theoretically calculated and simulated. This work serves to provide a behavior model that describes the nonlinear characteristics of pristine and degraded connectors, and a theoretical basis for evaluating the impacts of PIM and cross modulation on signal distortion.

Dual-Band Structure-Shared Antenna With Large Frequency Ratio for 5G Communication Applications

A dual-band structure-shared antenna with large frequency ratio is proposed in this letter by integrating two substrate integrated waveguide slot antennas (SIWAs) on the branches of dipole. In the proposed structure, dipole is fed by coaxial connector while SIWAs are fed by two microstrip lines. To improve the stability of the dipole and the isolation among three antennas, microstrip high-pass filter is introduced. Measured results show that the proposed antenna works at 27.3−28.8 GHz with directional radiation pattern and 3.02−5.03 GHz with omnidirectional radiation pattern.

Effects of Environmental Temperature on Passive Intermodulation in Electrical Connectors

Environmental temperatures may affect the high-frequency electrical performance of passive components, including passive intermodulation (PIM) characteristics. This work proposes a theoretical model of the third-order intermodulation distortion (IM3) signal as a function of the material properties and contact characteristics in a connector. A cross-sectional model of the inner conductor supported by finite-element analysis (FEA) simulations was used to investigate the effect of temperature on the current density distribution in different material regions and its impact on nonlinear performance. Based on electrical contact theory and temperature-dependent modeling, mathematical expressions were developed to calculate the impact of the various contact parameters, such as contact pressure, contact area, and contact resistance. Combining the effects of both material nonlinearity and contact nonlinearity, the IM3 product powers resulting from coaxial connectors associated with temperature change were predicted theoretically. A series of experiments were designed and conducted to measure the IM3 product powers of connectors for a variety of environmental temperatures. The model predictions show a good correlation with these experimental results.

Impact of receptacle degradation and loose connection on signal integrity and electrical performance repeatability

Radio frequency (RF) coaxial connectors are important constituents of modern communication systems. The degraded electrical contacts may adversely affect the signal transmission efficiency particularly in the case of loose connections. In this study, a distributed equivalent model of a coaxial connector with degraded receptacle and the loose connection was developed. The scattering parameters were analysed from the perspectives of both experimental testing and model simulation. The equivalent model and experimental results show good agreement. The impact of the degraded receptacle and loose connection on signal integrity was studied along with its electrical performance repeatability for different cases with respect to a degraded and loose connector. In addition, for the same degradation and loose level, the variation of contact resistance and contact capacitance was also investigated. These results are helpful for a better understanding of the intermittent failure of RF connectors. Moreover, these conclusions are also useful for diagnosing circuit faults caused by deteriorated repeatability of degraded and loose connectors.

W-band system-on-chip electron cyclotron emission imaging system on DIII-D.

Monolithic, millimeter-wave "system-on-chip" (SoC) technology has been employed in heterodyne receiver integrated circuit radiometers in a newly developed Electron Cyclotron Emission Imaging (ECEI) system on the DIII-D tokamak for 2D electron temperature profile and fluctuation evolution diagnostics. A prototype module operating in the E-band (72 GHz-80 GHz) was first employed in a 2 × 10 element array that demonstrated significant improvements over the previous quasi-optical Schottky diode mixer arrays during the 2018 operational campaign of the DIII-D tokamak. For compatibility with International Thermonuclear Experimental Reactor relevant scenarios on DIII-D, the SoC ECEI system was upgraded with 20 horn-waveguide receiver modules. Each individual module contains a University of California Davis designed W-band (75 GHz-110 GHz) receiver die that integrates a broadband low noise amplifier, a double balanced down-converting mixer, and a ×4 multiplier on the local oscillator (LO) chain. A ×2 multiplier and two IF amplifiers are packaged and selected to further boost the signal strength and downconvert the signal frequency. The upgraded W-band array exhibits >30 dB additional gain and 20× improvement in noise temperature compared with the previous Schottky diode radio frequency mixer input systems; an internal 8 times multiplier chain is used to bring down the LO frequency below 12 GHz, thereby obviating the need for a large aperture for quasi-optical LO coupling and replacing it with coaxial connectors. Horn-waveguide shielding housing avoids out-of-band noise interference on each individual module. The upgraded ECEI system plays an important role for absolute electron temperature evolution and fluctuation measurements for edge and core region transport physics studies.

Flexible Coaxial Ribbon Cable for High-Density Superconducting Microwave Device Arrays

Superconducting electronics often require high-density microwave interconnects capable of transporting signals between temperature stages with minimal loss, cross talk, and heat conduction. We report the design and fabrication of superconducting 53 wt% Nb-47 wt% Ti (Nb47Ti) FLexible coAXial ribbon cables (FLAX). The ten traces each consist of a 0.076 mm O.D. NbTi inner conductor insulated with PFA (0.28 mm O.D.) and sheathed in a shared 0.025 mm thick Nb47Ti outer conductor. The cable is terminated with G3PO coaxial push-on connectors via stainless steel capillary tubing (1.6 mm O.D., 0.13 mm thick) soldered to a coplanar wave guide transition board. The 30 cm long cable has 1 dB of loss at 8 GHz with -60 dB nearest-neighbor forward cross talk. The loss is 0.5 dB more than commercially available superconducting coax likely due to impedance mismatches caused by manufacturing imperfections in the cable. The reported cross talk is 30 dB lower than previously developed laminated NbTi-onKapton microstrip cables. We estimate the heat load from 1 K to 90 mK to be 20 nW per trace, approximately half the computed load from the smallest commercially available superconducting coax from CryoCoax

Octave Bandwidth High-Performance Microstrip-to-Double-Ridge-Waveguide Transition

This letter presents a microstrip-to-double-ridge-waveguide transition with high performance in the octave bandwidth operation between 6 and 12 GHz. The structure is based on a three-chamfered-step transformer supported directly over the microstrip line without soldering. The electric contact is ensured by the pressure between the first step of the transformer and a groove in the microstrip line. The transition is formed by two halves, minimizing the manufacturing complexity and the loss contact. A sequential procedure has been followed in the design process. Initially, a port directly feeding the planar structure has been considered, obtaining a simulated return loss level better than 25 dB in the whole operation band. Afterward, feeding through an SubMiniature version A (SMA) coaxial connector, a simulated return loss level better than 20 dB has been obtained. In order to verify the above theoretical simulations, a back-to-back arrangement has been measured, connecting two similar transitions. The prototype shows an insertion loss for a single transition lower than 0.8 dB in the 67% fractional bandwidth from 6 to 12 GHz.

CRW 13 – the new generation radio altimeter: the concept, design, and tests

PurposeThe purpose of this paper is to outline a novel concept of radio altimeter CRW-13 that has been designed and developed in the Lukasiewicz Research Network – Institute of Aviation as a result of the need to update the outdated structure of RWL-750M.Design/methodology/approachThe new design of the device consists of integral antennas and signal processor for smart digital signal filtering.FindingsAs a result of a number of laboratory tests and flight tests of the device installed on MP-02 “Czajka” ultralight aircraft promising results were achieved. They allow to move on to the next stage of implementation and preparation for the device certification.Practical implicationsThe CRW-13 meets with great interest of civilian and military potential customers. It is an ideal solution for airplanes, helicopters, unmanned and guided missiles. The universal design enables installation on many different platforms where exact height measurement is needed and crucial.Originality/valueAt the origin of the new concept was the need to replace the separate transmitting and receiving antennas with one unit comprising two planar microstrip antennas placed directly next to each other on a common plate block in the transceiver. This solution eliminates thick antenna cables and coaxial connectors, which are the most unreliable and problematic elements of radio altimeters. The new concept of integral antennas and the use of signal processors for smart digital signal filtration made it possible to take the technology to the next level.

Beam splitting of a novel triple-beam slot antenna array based on radial gap waveguide

We present a phenomenon of beam splitting caused by asymmetric boundaries. We design and manufacture a novel triple-beam slot antenna array working at the X-band to verify this phenomenon and show its potential applications. The corporate-feed slot antenna is based on a radial ridge gap waveguide (RGW) power divider, and is excited by a central coaxial connector. To achieve good efficiency, a radial SMA–RGW transition structure is proposed. Six different symmetrical and asymmetrical triple-beam RGW slot antenna arrays are mentioned in this paper. Among them, two symmetrical and one asymmetrical triple-beam RGW slot antenna arrays are fabricated and measured, and the measured results have good agreement with full-wave simulations, demonstrating stable performance of the proposed antenna array. Compared with the traditional slot antenna array, the proposal is capable of generating any number of beams in theory, especially odd beams, and each beam can be individually designed. The proposed shared-aperture radial multi-beam antenna can achieve simultaneous multi-directional coverage. It can meet the needs of multi-target tracking and imaging in blind spot detection and collision warning scenarios of the vehicular radar system. It also has potential value for satisfyimg the need for large-scale users to be connected in the wide-area continuous coverage scenario of the fifth generation communication system.

Applying additive manufacturing to integrate coaxial connectors with 3D printed waveguides for cascaded RF link applications

This paper explores the use of additive manufacturing as a low-cost method to integrate coaxial SubMiniature version A (SMA) connectors with waveguides operating at X-band. The integration of coaxial connectors into the filter and waveguide designs via 3D printing eliminates the need for two additional bulky external SMA-to-waveguide transitions, and allows for customizable integrated SMA-to-waveguide transitions that minimize impedance mismatch. Four designs, including air-filled and polycarbonate (PC) dielectric-filled waveguides and two-pole filters, are modeled and manufactured using additive manufacturing to demonstrate this integrative approach. Placement of the coaxial connector in terms of depth and location is optimized in the designs for good match using simulation. PC dielectric posts are also incorporated into the device to provide additional reinforcement to the coaxial connectors without impacting the radio frequency (RF) performance. Good RF performance is achieved with the variation less than 0.39 dB between simulated and measured insertion loss results at the center of the device passband.

Analysis and Design of a Low-Cost Well-Performance and Easy-to-Design Current Sensing Circuit Suitable for SiC mosfets

Current sense resistor (CSR) is widely used due to cost and integration considerations in industrial applications. However, when CSRs are used to sense transient currents caused by power device switching, especially fast-switching silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (mosfets) with high di/dt, even a tiny parasitic inductance in CSRs bring a significant impact on its sensing performance. This article proposes a low-cost well-performance and easy-to-design current sensing circuit that uses the CSRs and an LR compensation network (LRCN) to compensate for the effect of parasitic inductance on transient current sensing. In order to support the parameter selection of the LR network, the effects of parameters such as parasitic capacitance, parasitic inductance, and loads on the performance of the proposed current sensing circuit are analyzed in detail. Meanwhile, a parasitic inductance measurement method that only needs passive probes is proposed to measure and calculate the parasitic inductance of CSRs. This circuit can not only sense the transient current on the printed circuit board level but also observe the transient current on the oscilloscope through a coaxial cable connection. Finally, experimental studies under an inductive load double pulse test setup with SiC mosfets are carried out to verify the validity and feasibility of the proposed transient current sensing circuit. Only a high self-resonant frequency inductor and a surface mounted device resistor are needed to form the LR network to fully compensate the effect of parasitic inductance on CSRs.

Comparative study on longitudinal momentum characteristics of L-type and I-type breech in railgun

The position and magnitude of the longitudinal force during launch are very important to the design of electromagnetic railgun. This problem has become a hot topic of research for a long time. Previous experiments showed that most of the recoil force of the electromagnetic railgun locates at the breech. In order to study the stress distribution and momentum characteristics of the breech during launch. Based on Maxwell’s stress tensor, the momentum conservation equations for electromagnetic railgun were derived. Depending on whether the direction of the source current is perpendicular to the current direction in the rails, the breech is simplified and summarized into I-type and L-type structures. Then, the 3-d models of the two breeches were established and the launch process was simulated by finite element method. Some results such as the current density, magnetic field intensity and electromagnetic stress of the current injector plates and coaxial power connector under both models were obtained. The simulation results show that the longitudinal force on the breech is concentrated on the current injector plates. The longitudinal force on the power connector of L-type breech is much bigger than that of the I-type breech, up to nine times. Besides, different structures of the breech will not affect the launch performance of the railgun.

Non‐invasive Neuromodulation Using Ultrasound

The discovery of light sensitive proteins led to the development of optogenetics and allowed the precise manipulation of neuronal and non‐neuronal cells. This technique uses particular wavelengths of light to manipulate both neuronal and non‐neuronal cells [2, 5]. It has enabled the study of information processing in the brain and recent studies are looking into clinical translational applications of the technique [1]. Despite the advantages offered by optegenetics, it has the drawback of being invasive as light does not penetrate skin past a few millimeters. It is not possible to target deep tissue within the body using this technique and this limits the application in the context of diseases such as Parkinson’s [3] or heart malfunction [4].We are developing devices that can non‐invasively manipulate cells using a technique termed “sonogenetics”. This technique uses a combination of engineering cells to be more sensitive to mechanical stimuli as well as developing ultrasound transducers capable of stimulating cells in freely moving, awake mice. We demonstrate the development of miniature transducers made from non‐hysteretic single crystal lithium niobate to be used for the development of sonogenetics. In addition, we o er mathematical insights to the mechanism of action of ultrasound on neurons. Our analysis of membrane deflection enables us to predict cellular activity based on the applied ultrasound stimulus. By extension, we use this analytical framework to inform the development of transducers and stimulation parameters for achieving non‐invasive stimulation of cells.Support or Funding InformationWM Keck FoundationNational Institute of HealthMembrane Deflection and Capacitance Change due to Ultrasounda–d) Membrane deflection due to an ultrasound stimulus, with parameters 7 MHz and 1 MPa pressure. The stimulus is provided for 10 ms, the resulting area change(e) and the capacitance (f) are then calculated from the input parameters. The value of capacitance generated in this model is then used in a Hodgkin‐Huxley neuron model to determine action potential generation.Figure 1a) LN transducer housed in a MMCX coaxial connector designed for long term behavioral studies in awake, freely‐moving mice. b) Device mounted on a mouse skull to be used for characterization using an automated hydrophone setup (c). d)Pressure profile over the transducer face with a 450 mV input results in up to 2 MPa pressures. e) Transducer attached to mouse skull for long term behavioral studies.Figure 2

A Microwave Platform for Reliable and Instant Interconnecting Combined with Microwave-Microfluidic Interdigital Capacitor Chips for Sensing Applications

This work presents a novel platform conceived as an interconnect box (ICB) that brings high-frequency signals from microwave instruments to consumable lab-on-a-chip devices. The ICB can be connected to instruments with a standard coaxial connector and to consumable chips by introducing a spring-levered interface with elastomer conductive pins. With the spring-system, microwave-microfluidic chips can be mounted reliably on the setup in a couple of seconds. The high-frequency interface within the ICB is protected from the environment by an enclosure having a single slit for mounting the chip. The stability and repeatability of the contact between the ICB and inserted consumable chips are investigated to prove the reliability of the proposed ICB. Given the rapid interconnecting of chips using the proposed ICB, five different interdigital capacitor (IDC) designs having the same sensing area were investigated for dielectric permittivity extraction of liquids. The designed IDCs, embedded in a polydimethylsiloxane (PDMS) channel, were fabricated with a lift-off gold patterning technology on a quartz substrate. Water–Isopropanol (IPA) mixtures with different volume fractions were flushed through the channel over IDCs and sensed based on the measured reflection coefficients. Dielectric permittivity was extracted using permittivity extraction techniques, and fitted permittivity data shows good agreement with literature from 100 to 25 GHz.