Coaxial Connectors Research Articles

High‐precision mathematical modelling of passive intermodulation in connectors

Passive intermodulation is an undesirable but unavoidable interference in communication system. Two high-precision mathematical models are proposed to predict the passive intermodulation behaviour in coaxial connectors. Three kinds of coaxial connectors are selected as test samples. A series of two-tone tests with increasing input power from 30 to 44 dBm are performed. The measured results are divided into two parts, which are used for model fitting and prediction verification, respectively. Based on the observation of the concave function characteristics in current-voltage curve of the connectors, the hyperbolic sinusoidal (sinh) and Gram-Charlier A Series models are proposed. Compared with the polynomial models, the goodness of fit of the two novel models is higher. Model validation is performed, showing the higher accuracy of the proposed models.

Conformal Integration of Efficient Conductive-Ink-Printed Antennas in Smart Suitcases for LPWAN-Based Luggage Tracking.

In the context of localization and sensing within the Internet of Things, new antenna manufacturing technologies, such as antennas printed with conductive inks on thin thermoplastic sheets, allow for seamless integration into plastic objects produced by an injection molding process. In this paper, we present printed sensor antennas for the [862–928] MHz band supporting LoRa and Sigfox and the [2.4–2.5] GHz band for WiFi, Bluetooth, and IEEE802.15.4 communication. To integrate them into smart suitcases, the antennas are printed, overmolded, tested, and measured, following a dedicated conformal integration strategy consisting of two design iterations. Additionally, as a more convenient connection to the printed antennas, printed transmission lines along with a dedicated transition to printed circuit board technologies are implemented and characterized, avoiding rigid coaxial connectors that exhibit fragile mounting on flexible substrates. The overmolded stand-alone antennas achieve fractional impedance bandwidths of 26% and 15% covering the [862–928] MHz and [2.4–2.5] GHz bands, respectively, with a substantial margin and with in-band simulated total efficiencies of 94% and 88%, respectively. Finally, the seamless integration of two antennas into a smart suitcase for tracing via Sigfox and WiFi demonstrates the potential of the proposed technique to realize high-performance antennas occupying virtually no real estate.

Passive Intermodulation Distortion in Connectors With Nonlinear Interaction in Electrical Contacts and Magnetic Materials

Nonlinearities in electrical contacts and magnetic materials are two main contributors to passive intermodulation (PIM). In this study, mechanisms of thermally induced current truncation and hysteresis effect are introduced to provide explanations for PIM generation and to make predictions for the third-order intermodulation (IM3) products resulting from coaxial connectors. Equivalent circuit models are presented to provide insight into the nonlinear sources both in contact junction and body area with the relative contribution of various physical parameters. The finite element analysis (FEA) model of the central conductor of a DIN-to-N coaxial adapter is developed to identify the current density and temperature distribution in the contact area, while an FEA model of simplified connector cross section is presented to simulate the magnetization effect in the body area. Combined with two nonlinear sources, an equivalent circuit model predicting the PIM behavior is developed. The simulation results show that the material nonlinearity contributes to frequency dependence, while the power dependence is dominated by both nonlinear mechanisms. Connectors with different contact surface are obtained by designed accelerated tests, and two types of connector with different materials are manufactured. Good agreements are observed in experimental measurements, verifying the proposed model of contact–material interaction-induced PIM.

Supplementary comparison between INTI-PTB of scattering coefficients in PC-3.5 connector (SIM.EM.RF-S17)

Main textThis document presents the final report of the supplementary comparison identified as SIM.EM.RF-S17 and carried out by the NMI (National Metrology Institute) from Argentina (INTI) and Germany (PTB).The measurands were S-parameters up to 32 GHz in 3.5 mm coaxial connector. In addition, this comparison shows how digitalization during the measurement process and data analysis can improve a comparison outcome, this comparison being one of the first comparisons under BIPM scope in which exchanged data between participants consisted of digital uncertainty objects based on an XML structure.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Passive Intermodulation on Coaxial Connector Under Electro-Thermal-Mechanical Multiphysics

This work proposes and demonstrates a multiphysics model for the passive intermodulation (PIM) effect on coaxial connectors with complex electro-thermal-mechanical coupling. The PIM effect under multiphysics is numerically modeled and solved from the basis of contact components and parameters. In the experimental demonstration, to get rid of the random test error, the design of experiment method is utilized to build an empirical model for verification. The comparison shows the max prediction differences with comparison among the proposed numerical multiphysics model, empirical model, and experiment are within ±3 dB; the good match between the experiment and predictions proves the theory.

Особливості проєктування поздовжньо-співвісних хвилеводно-мікросмужкових з’єднувачів

The authors justify the use of combined longitudinal-coaxial connectors — waveguide-coaxial or waveguide-microstrip type — in new modern antenna-feeder microwave paths. Using the example of a basic coaxial waveguide-coaxial connector based on a section of a regular rectangular waveguide, the study considers the process of converting an electromagnetic wave of a regular waveguide of the main waveguide type H10 into a transverse electromagnetic wave of a coaxial line with a wave resistance (impedance) Z0 = 50 Ohm. Such a connector allows implementing good electrical parameters — matching (standing wave ratio, SWR) and linear losses — but its design is difficult to configure and cannot be reliably reproduced. However, the basic operation principles of this connector make it possible to use it as a prototype when creating modern coaxial waveguide-coaxial or waveguide-microstrip connectors. One example of such a modern connector is the sealed longitudinal-coaxial waveguide-microstrip connector based on a segment of H-shaped waveguide, shorted by an end wall on one end. Correcting the reactive component of both inductive and capacitive nature will allow achieving the required parameters of the wave impedance of the connector. With this in mind, the author has built an inductive-capacitive system consisting of a matching element in the form of a staggered fin and a corrective element in the form of a rectangular parallelepiped. To ensure the air tightness of the connector design, the segment of the coaxial line was replaced by a sealed coaxial insert, which is a serial electronic component. Particular attention was paid to the layout and design of this sealed waveguide-microstrip connector, as well as to the calculation of the overall dimensions of its elements. The article proposes an original technique for measuring the main parameters of both waveguide-coaxial and waveguide-microstrip connectors. The author forms a mathematical model of combined type connectors based on the scattering wave matrix and presents the parameters of real hermetically sealed longitudinally coaxial waveguide-microstrip connectors based on waveguide segments of various standard sizes and measured at various frequencies.

Power Balance Control Strategy of Permanent Magnet Synchronous Motor of Belt Conveyor

Aiming at the problem of multi-machine power balance control of long distance belt conveyor with double drum and three permanent magnet synchronous motor, the control method of speed and torque of master and slave motors of belt conveyor driven by multiple motors is analyzed. According to the properties of coaxial rigid connection and flexible connection of three motors of double drum, The power balance strategy based on fuzzy Active Disturbance Rejection Controller (ADRC) is proposed to achieve the purpose of disturbance rejection and improve the stability of the system. The simulation results show that the proposed method can solve the power imbalance problem of the system motor. Compared with the traditional PID control method, the corresponding speed of fuzzy ADRC control method is less than 300ms, the power deviation of rigid connected motor is less than 0.1kW, and the power deviation of flexible connected motor is less than 0.3kW. This method can effectively reduce the synchronization error of each motor, and has good robustness, and realize the power balance distribution among multiple motors.

Prediction of the High Frequency Behavior in Degraded Coaxial Connector Based on Neural Network

Accurate prediction of high frequency behavior for the degraded contact surface is of great significance for the reliability evaluation of the connector. A prediction algorithm of neural network is proposed to forecast the high frequency scattering parameters under different degrada-tion levels. The degraded high frequency parameters are extracted according to the developed equivalent model. Simulations are conducted to predict the scattering para-meters at the specific frequencies using the BP (back propagation) and Elman neural networks, and the prediction accuracy is further compared. Moreover, the scattering parameters at 3.1GHz to 3.5GHz are predicted for the two degradation levels, which provides the variations under higher frequency.

Improved Design of Flange Mount Coaxial Connector With Low Passive Intermodulation Distortion

Imperfect electrical connections cause multiple problems in radio-frequency (RF) measurements, with passive intermodulation (PIM) being the most common one. This article proposes a new design approach to reduce the PIM distortion caused by the imperfect electrical connection in flange mount coaxial connectors. The proposed approach employs a flexible ring embedded in the outer conductor of the flange mount coaxial connector to improve the reliability of the metal electrical connection. A simulation model is further developed to analyze the effects of the embedded ring on the signal transmission performance. The effectiveness of the proposed approach is verified by experiments, demonstrating that the improved design can not only decrease the PIM level by up to 9 dB, but also show a good reliability and stability in the conditions requiring repeated connection and disconnection, and thus, this method has the potential for the application of all flange mount devices.

The modified quarter-wavelength resonator method for parameters control of the coaxial connector dielectric beads

The paper describes the modification of the SRG-50-751 connector by means of the support bead material change. The modification is made in order to extend the operating temperature range of the connector, and may also reduce the VSWR of the connector. The modified coaxial quarter-wavelength resonator method is used for bead parameter control. The modification of the method increases the dielectric constant measurement accuracy and enables to measure specimens with different lengths. The method of dielectric loss tangent measurement of the beads is outlined in the article.

Effect of second harmonic and second‐order intermodulation on third‐order passive intermodulation

Third-order intermodulation (IM3) is considered as a typical metric to evaluate passive intermodulation (PIM) in electrical connectors, which may be affected by the second-order effect in the circuit with cascaded non-linearities. In this study, the effects of second harmonics and second-order intermodulation on the IM3 powers were theoretically modelled and experimentally verified. Combined with mathematical modelling, an equivalent circuit model of a passive non-linear source was presented to investigate the effect of second-order signals on the IM3 powers. A modified non-linear transfer function was developed by considering multiple non-linear superpositions in cascaded non-linearities. Based on the designed two-tone test, a mathematical expression was provided with the determination of correlation model coefficients. Numerical simulations were performed by using the proposed model, demonstrating the effect of signals induced by the second-order non-linearity on the IM3 powers in series passive components. The IM3 powers resulting from cascaded connectors associated with different signal frequencies were predicted. Coaxial connector samples were designed as cascaded PIM sources in circuits, which were experimentally measured in a GSM 900 MHz frequency band. Good agreement was obtained between the predictions and measurements with error of 0.76 dB in average.

Research on High-power Transmission Technology of Satellite Borne RF Connector

The reliability of the communication link shall be affected severely due to failure modes such as multipactor, low pressure discharge, and thermal damage that are commonly found in the RF connector when it performs high-power microwave signal transmission in the vacuum environment of outer space. This paper proposes supporting measures in respect of design against multipactor, low pressure discharge and thermal damage after analyzing mechanisms of failure modes of the RF connectors when it transmits high-power microwave signals in a vacuum environment. Upon tests, these proposed measures can effectively guarantee the reliability of the RF coaxial connector transmitting high-power signals in vacuum.

A wide‐band all‐metal and high‐gain omnidirectional antenna with simple prototype

An all-metal dipole two-element array antenna is proposed to achieve a wide-band impedance bandwidth and an omnidirectional radiation pattern. The concept of this antenna derives from a quarter-shorted magnetic dipole structure. The proposed antenna consists of an air-filled metallic parallel bi-plate and two dipole elements. The dipole elements are perpendicularly fabricated at the open end of the bi-plate. Fed by a single coaxial SMA connector in the center of this structure, a quasi-TEM mode in the bi-plate can be excited similar to the parallel waveguide. Based on the multiple resonances and line-array effect, the proposed antenna can achieve a wide-band working bandwidth and a stable omnidirectional pattern. Simulated and experimental results confirm that this antenna has a peak gain of 4.16 dBi and a relative impedance bandwidth of 72% (0.8–1.7 GHz). The proposed antenna can be used in UAV (unmanned aerial vehicle) application.

A Novel Nonlinear Model for Passive Intermodulation in Coaxial Connectors

A novel nonlinear model describing the passive intermodulation (PIM) behavior in coaxial connectors is developed based on sine function. Two types of coaxial connectors are selected as test samples, and a series of two-tone PIM tests are conducted. The coefficients of the sine function model for these connectors are obtained by fitting the test results using ordinary least squares (OLS) method. The predicted results of the sine function model agree well with the test results, which prove that the sine function model can be used to describe the third-order and the fifth-order PIM performance of coaxial connectors accurately. The differences between the sine function model and other nonlinear models are compared.

Cost-Effective Surface-Mount Off-Center-Fed Dipole Antenna Element and Its Array for 5G Millimeter Wave New Radio Applications

A cost-effective ball grid array (BGA) packaged surface-mount off-center-fed dipole antenna element and its array are proposed for 5G millimeter-wave new radio (NR) applications. The proposed antenna element exhibits a compact size of 0.61 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.61 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.16 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ( λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength in free space at the center operating frequency) and is realized by only one FR4 layer to minimize cost. Plated through holes (PTHs) connect the dipole patch on the top layer to the bottom layer. Furthermore, tin-lead solder balls are mounted under the bottom layer to form the BGA packaging. The surface-mountable feature enables the antenna element to be integrated with other surface mount devices without any waveguide or coaxial connectors. The evaluation board uses a 50- Ω grounded coplanar waveguide (GCPW) line to test the performance of the antenna element and array. The antenna prototype and evaluation board have been manufactured and measured. The measurement results show that the -10-dB impedance bandwidth of the proposed antenna element achieves 35.7% in the range of 25.1-36 GHz. The measured peak gains of the antenna element and the 1 ×8 arrays are 6.72 and 13.53 dBi, respectively.

Wideband split-ring antenna arrays based on substrate integrated waveguide for Ka-band applications

AbstractThis paper presents wideband split-ring antenna arrays based on substrate integrated waveguide (SIW) for Ka-band (26.5–40 GHz) applications. The antenna array is fed by a 2.92 mm coaxial connector (K-connector) and the power is equally distributed to each split-ring resonator. The designed coplanar waveguide (CPW), SIW, CPW-to-SIW transition, coaxial-to-CPW transition, and two-stage SIW power divider are described in detail. By using a thin Rogers 6002 substrate with silver epoxy-filled vias, a transition prototype is designed, fabricated, and tested in a back-to-back configuration. A wideband split-ring resonator is developed as a single element and four possible arrangements of antenna arrays are introduced. By combining the designed components and routing paths, two full layouts of the antenna arrays with four split-ring resonators are addressed. As a demonstrator, a 2×2 antenna array prototype in a compact format is designed, fabricated, and tested. The fabricated antenna array achieves a measured directivity of 15.0 dBi with a fractional bandwidth of 23.0% centered at 30.5 GHz.

Wideband transverse electromagnetic cell design and its application in frequency selective surface measurement

An open transverse electromagnetic cell (TEM cell) that covers L-band, S-band, and C-band is proposed in this paper. According to impedance matching theory analysis, the characteristic impedance of coaxial connector and microstrip with air as substrate are considered, which are combined with a taper gradient section to realize the function of TEM cell. The proposed TEM cell was modeled and simulated in CST Microwave Studio. Through full-wave simulation, the proposed TEM cell demonstrates a wideband transmission characteristic, S11 less than −10 dB from 1 to 8 GHz, which is relatively rare among the designs that have been reported. The test flow and data post-processing method are given. To verify the effectiveness of the test method, an example of measuring a classical square slot frequency selective surface that their resonance frequency is 3.7 GHz is designed and simulated in the TEM cell. To verify the simulated results, a prototype is fabricated and measured with the proposed TEM cell. The experimental result demonstrates a good agreement with the simulated result, which indicates that the designed TEM cell has good test performance.

A single‐layer high‐gain dipole antenna array with a bidirectional radiation pattern based on parallel‐strip line

A single-layer dipole antenna array with quasi-Yagi configuration has been proposed and demonstrated, which provides a dual radiation pattern with the same sense. This antenna is mainly composed of a substrate-supported parallel strip line (PSL) and several periodic dipole elements. Fed by PSL, dipole elements can be stimulated with a uniform power, forming a linear dipole antenna array. By adjusting the elements separation appropriately, the step phase of array factor can be tuned to achieve the same directivity as the element dipole. When an SubMiniature version A (SMA) coaxial connector is connected at the beginning of PSL, the fundamental mode TEM in the PSL is excited and the radiation electromagnetic wave from the dipole elements is achieved. A taper line between the SMA and PSL can be used to reduce the discontinuity, minimizing the reflection coefficient of the port. According to the theory of classical Yagi antenna, the gain can be further improved by introducing multiple directors, achieving the gain increment of about 3 dBi in the proposed design. Considering 5 GHz frequency band applications (4.85–5.2 GHz), the experimental and simulated results show the proposed antenna array has a working bandwidth ( | S 11 | ≤ − 10 d B ) from 4.85 to 12 GHz.

Selection of tools and cutting modes for turning small-sized high-precision parts of micro-wave electronics from beryllium bronze

Beryllium bronze has the property of plasticity after heat treatment, which is a decisive factor when choosing the material of conductors in unpressurized coaxial connectors. The presence of burrs on these parts according to technical requirements is not allowed. When turning details of beryllium bronze, difficult to remove burrs appear. The aim of the study is to select a tool and cutting modes for turning small-sized high-precision parts of microwave electronics from beryllium bronze, in which there are no burrs or their size and quantity are minimal. In this study, empirical methods are used in the form of experimental selection of cutting modes and tools for the purpose of combating burrs, and analytical methods in the form of analysis of the character of burrs using the provisions of the theory of metal cutting, analysis of factors affecting the formation of burrs during machining surface parts. On CNC lathes CITIZEN CINCOM studied typical of this type of production tools ten leading manufacturers of precision cutting tools for turning. As a result of the study, it was not possible to completely exclude the appearance of burrs during machining. The smallest size and the number of burrs were obtained when machining with carbide tools manufactured by Swiss companies Fraisa, Utilis, IFANGER, Applitec. TiAlN coating is well suited for beryllium bronze treatment. When turning with a new tool at low speeds, the number of burrs decreases, their character changes, they become small drop-shaped. The processing modes recommended by the tool manufacturer differ from those selected experimentally. For further use of the selection results, it is necessary to create a database of regulatory and reference information on the types of processing for specific materials, tools, machine tools according to the accuracy criteria, taking into account the minimization of the number and size of burrs.

Evaluation of the position of the connection point of the coaxial probe to the rectangular printed antenna

The input impedance of the printed antenna depends on the feed connection coordinate. It is often possible to provide the required level of the voltage standing wave coefficient of a simple printed antenna by correctly selecting the connection coordinate of the feeding coaxial probe. The selection of the coordinate of the coaxial probe connection by analytical calculations is usually inconvenient due to its complexity, so often numerical calculation methods are used to optimize printed antennas, such as the method of finite differences in the time domain, the method of moments, and others. The paper deals with the problem of selecting the connection point of a feeding coaxial probe to a rectangular printed antenna using the finite difference time domain method, the cavity model method, and a combination of these two methods. It has been established that the finite differences time domain method requires large computing power, since the selection of the coordinate of the connection of the coaxial probe requires a complete solution of the electrodynamic problem for each case of feed connection. The cavity model method allows us to estimate the position of the power point almost in real time with minimal computing power, but it has much less accuracy compared to the finite difference time domain method. It is possible to reduce the number of iterations in the process of selecting the coordinate of connecting the coaxial probe using the finite difference time domain method due to its joint use with the cavity model method. In this case, the first (initial) coordinate of the coaxial probe connection is determined using the cavity model. After that, optimization algorithms are applied together with the finite difference time domain method. The paper presents the results of comparing the required number of iterations for convergence of the optimization algorithm based on the confidence domain method when using the finite difference method in the time domain and the joint use of the cavity model and the finite difference time domain when solving the problem of selecting the feeding coordinate.