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The present work is dedicated to an experimental and theoretical study of an innovative underwater ultrasound source. The source works using a technique in which a pulsed power generator using the impedance mismatch of a long high-voltage coaxial cable generates a train of voltage impulses with a very high pulse repetition frequency of the order of a few MHz. Applying this train of voltage impulses to a pair of underwater electrodes generates a streamer-initiated breakdown of water and, subsequently, a plasma column connecting the electrodes over a very large inter-electrode gap of 55 mm. The interaction of the long plasma column thus formed with the surrounding water produces a rapidly expanding vapor bubble, an "instrument" producing a strong pressure wave with an overall energy efficiency of 24%, an order of magnitude higher than most underwater pressure sources reported in the literature. [ABSTRACT FROM AUTHOR]

Purpose: Standard head coils used at 7T MRI suffer from high signal loss at lower brain regions and neck. This study aimed to increase the field of view (FOV) of a birdcage coil to image the lower brain regions and neck with a straightforward approach of using add‐on transmit shielded coaxial cable coil (SCC) elements. Methods: A new head‐neck coil was modeled as a combination of the 2Tx/32Rx Nova head coil and 6Tx SCC elements. The add‐on transmit SCC elements have been produced. The full wave electromagnetic simulations were performed to analyze the coil geometry and estimate the local specific absorption ratio (SAR). The B1+$$ {\mathrm{B}}_1^{+} $$ field maps and structural images were acquired in a phantom and in vivo on a 7T scanner. Results: The computed SAR histogram revealed a peak SAR10g$$ {\mathrm{SAR}}_{10g} $$ of 4.08 W/kg. The simulated and measured B1+$$ {\mathrm{B}}_1^{+} $$ maps are in good agreement. The manufactured coil's S‐parameters are below −$$ - $$10 dB. The B1+$$ {\mathrm{B}}_1^{+} $$ field measurements on a subject presented the increase in the FOV. The T1‐weighted structural images of three subjects acquired with the head‐neck coil showed increased coverage compared to the head coil only. Conclusion: Combining the 2Tx/32Rx Nova head coil and 6Tx SCC elements allowed imaging of the whole brain with an increased FOV down to the C4 spine. The coil stayed fully functional when different subjects were scanned. We conclude that the SCC transmit‐only coils are a robust adjunct to conventional coil designs and can meaningfully enhance and expand their field of view. [ABSTRACT FROM AUTHOR]

With the demand for scalable cryogenic microwave circuitry continuously rising, recently developed flexible microwave striplines offer the tantalizing perspective of increasing the cabling density by an order of magnitude without thermally overloading the cryostat. We use a superconducting quantum circuit to test the thermalization of input flex cables with integrated 60 dB of attenuation distributed at various temperature stages. From the measured decoherence rate of a superconducting fluxonium qubit, we estimate a residual population of the readout resonator of (2.2 ± 0.9) × 10 − 3 photons and we measure a 0.28 ms thermalization time for the flexible stripline attenuators. Furthermore, we confirm that the qubit reaches an effective temperature of 26.4 mK, close to the base temperature of the cryostat, practically the same as when using a conventional semi-rigid coaxial cable setup. [ABSTRACT FROM AUTHOR]

This paper uses the non-integer ratio coaxial line impedance transform matching method to design a wideband RF power amplifier. The motivation for the research stems from the limitations of the fixed conversion ratio of traditional impedance converters at RF frequencies and the challenges of low-frequency performance degradation. A fixed conversion ratio and low-frequency performance often limit traditional impedance matching methods. The model enables flexible and efficient wideband impedance matching, covering a wide frequency range of 2–650 MHz. The results show that the power amplifier has an output power of more than 48.5 dBm, a gain of more than 16 dB, and a drain efficiency (DE) of more than 55% in the frequency band range of 2–650 MHz, which is superior to similar designs in terms of low-frequency performance and bandwidth. [ABSTRACT FROM AUTHOR]

A novel common-aperture miniaturized antenna with wideband and dual-polarized characteristics is proposed, which consists of a circularly polarized (CP) and a linearly polarized (LP) antenna. The circularly polarized antenna stacked on the upper layer adopts asymmetrical ground and introduces the patch and T-type feed network. On this basis, the meshed reflector structure, which also works as a ground plane for the LP antenna, is added to reduce the influence on circular polarization and achieve directional radiation. The LP antenna stacked in the lower layer uses a monopole structure, and the coaxial feed line perforates the reflector, and thereby the common-aperture antennas are tightly stacked together from top to bottom. Simulation and test are in good accordance, and the results show that the two ports of the antenna are well matched in the range of 5.5 GHz to 7.8 GHz, where peak gains of 8.5 dB and 6 dB are realized for circular polarization and linear polarization, respectively. Moreover, the 3 dB axial ratio (AR) bandwidth of the CP antenna is 34.3% and the isolation between the two ports is better than 15 dB, suggesting potential applications in the relay platform or drone detection for signal transmission and reception. [ABSTRACT FROM AUTHOR]

This paper presents a compact, broadband, high‐gain dielectric rod antenna. By utilising an air–dielectric hybrid method for designing the radiating and matching sections, gradual variations in the average equivalent permittivity along the rod are achieved, and the mechanism of the method is analysed. This approach facilitates a smooth impedance transition from the feed to the air, resulting in good impedance matching characteristics. Additionally, the antenna is fed through a tapered double‐ridged waveguide (DRW) with a coaxial line to tapered DRW transition. The proposed antenna achieves an impressive impedance bandwidth of 90.2%, covering the entire K and Ka bands. The unique structure of the proposed dielectric rod significantly enhances the antenna's gain, reaching a maximum value of 17.86 dBi. With its small aperture and compact longitudinal dimensions, this antenna is suitable for applications in settings like the Space Environment Simulation Research Infrastructure (SESRI). [ABSTRACT FROM AUTHOR]

In this paper, an ultra-wideband substrate integrated coaxial line (SICL) array based on silicon-based MEMS process is proposed for high-speed data transmission. A quasi-coaxial transition array is designed to connect the SICL array with grounded-coplanar waveguides (GCPWs). Moreover, a stepped-impedance matching structure is introduced to reduce the discontinuities and improve the transmission performance. For high efficiency design, a Bayesian Optimization (BO)-based approach is adopted to optimize dimensions of the proposed SICL array. The objective function is set to be the weighted combination of the bandwidth and the crosstalk of the proposed array structure to obtain wide bandwidth and low crosstalk simultaneously. With the proposed BO-based approach, iteration times can be reduced by approximately 99.9% compared with the parametric sweep method. A 40-channel SICL array is designed and fabricated under silicon-based Micro-electromechanical Systems (MEMS) process. Ultra-wideband of 110 GHz is measured in each channel with the insertion loss less than 3 dB and the return loss larger than 15 dB. The couplings between two adjacent channels are no more than − 30 dB. Good eye diagram and low bit error rate (BER) are achieved for each channel at data rate of 95 Gb/s and hence the total data rate can reach 3.8 Tb/s. The bandwidth density of the proposed SICL array is 0.164 Gb/s/ μ m, which is much higher than those of the conventional SICLs. [ABSTRACT FROM AUTHOR]

As neutron yields increase at fusion facilities, a universal symptom the community must deal with is MeV neutron-induced backgrounds in cables running to diagnostics. On the first Gain > 1 plasmas in the world, the National Ignition Facility (NIF) neutron time-of-flight (nToF) diagnostic registered significant cable backgrounds that compromised key performance measurements. The South Pole nToF is uniquely located inside the NIF Target Bay shield walls, ∼18 m from the fusion source, and consequently has long coaxial cable runs (> 20 m) that see significant neutron fluence. The resulting neutron-driven current in the cable is comparable to the downscattered neutron signal, compromising the downscattered ratio (DSR) measurement. We have characterized this background with a series of on-shot tests and developed a background subtraction technique to mitigate these effects. The background subtracted DSR results are validated against zirconium activation measurements, indicating that we have successfully reclaimed high-quality data output. The ion temperature measurement is found to not be affected by this background. Alternative approaches to addressing neutron-induced cable backgrounds are presented for potential future hardware upgrades. [ABSTRACT FROM AUTHOR]

A low‐insertion‐loss, high‐power rectangular waveguide‐to‐coaxial transition is proposed in this letter. The proposed rectangular waveguide‐to‐coaxial transition is constructed by a rectangular‐waveguide H–T junction and square coaxes. The H‐plane T‐junction is used to convert the input wave into two in‐phase waves. After passing through three 90° bends, the electric field vectors of the two in‐phase waves are in opposite directions. Then they combine at the coaxial port. The TE10 mode in the rectangular waveguide is converted to the TEM mode in the coaxial line by the transition ridge. The power capacity of the transition is increased by the N‐type connector. For verification, an X‐band rectangular waveguide‐to‐coaxial transition has been designed, fabricated, and measured. The measured results show that the 20‐dB fractional bandwidth is 22.4%. The insertion loss is no more than 0.1 dB. The transmission efficiency is 97.7%. And the power capacity can reach 65 kW. [ABSTRACT FROM AUTHOR]

This paper presents a study of six physical transmission line transformers (TLTs) designed to provide wideband output matching for laterally diffused metal oxide semiconductor (LDMOS) transistors within a push-pull amplifier operating in the 1.8-30 MHz spectrum with an output power of 600W. While the mathematical model of TLTs is well described in the literature, the impact of physical construction methods on impedance matching and real amplifier performance is more challenging to ascertain. This paper compares six different TLTs built on various ferrite cores and employing different implementations of transmission lines. Return loss below -14 dB was achieved from 1.65 to 37.4 MHz, with most of the tested transformers exhibiting return loss better than -10 dB up to 50 MHz. The study also presents the impact of transmission line implementation on impedance matching using both special-purpose low impedance coaxial cable and a combination of general-purpose coaxial cables connected in parallel. Comparison of three chosen transformers in a real RF amplifier shows that using parallel transmission lines can lead to a return loss comparable to that of a specialpurpose coaxial cable, although at the cost of lower efficiency and output power. Second harmonic cancellation effect was also investigated for three transformers. [ABSTRACT FROM AUTHOR]

This study presents a detailed comparative review of microwave and mm-wave band-wise microstrip-to-waveguide transitions for MMIC/MIC interconnect transmitter/receiver front-end connections in microwave, mm-wave, and sub-mmwave applications. All microwave band microstrip-torectangular waveguide transitions from 4 GHz (C-band) to 325 GHz (Y-band) have been reviewed and compared in terms of their performance parameters like return loss (RL), insertion loss (IL), and their relative or fractional bandwidth. This survey also highlights the requirement for appropriate substrates for distinct operating bands in PCB fabrication, which include extracted dielectric permittivity, loss tangents, and necessary thicknesses. The literature also strongly talks about the suitable rectangular waveguide needed for a particular waveguide with its dimensional information. The comparison also talks about the type of transitions (inline or vertical), and the and the coupling methodology used for transitions merits and demerits along with their applications. The outcome of this detailed review is that it describes all the methodological steps involved, along with mathematical expressions and their performance parameters, for new researchers and scientists in this particular area. [ABSTRACT FROM AUTHOR]

This paper presents a novel foldable S-band microstrip patch antenna array operating in the 2.4–2.45 GHz band. The substrate is designed to allow the array to be folded and arranged in tiles, forming a versatile, reconfigurable antenna array. Additive manufacturing is used to fabricate the substrate for ease of fabrication and flexibility in its design. The major challenge in this type of design is creating a proper method of feeding the elements while maintaining the array's optimal performance. A novel hinge design that can hold a coaxial cable for the series-fed array is introduced. The hinge provides the capability of folding the array from a flat orientation into various folded orientations. In this paper, a 2 × 1 microstrip array unit is presented as proof of concept. The antenna was fabricated and measured, and the results of the measurements are in close agreement with the simulations. The antenna can provide a gain as high as 7.72 dBi in flat conditions. [ABSTRACT FROM AUTHOR]

Abstract Broadband couplers consist usually of multiple coupled lines that are each a quarter wave‐length long. Herein, in contrast to conventional methods, a short length of a microstrip line is coupled to a coaxial line. The length of the coupled microstrip line is small compared to the wavelength at the lowest operating frequency. The coupling is weak and the microstrip line is λ/8 at the highest operating frequency. The proposed structure resembles a pair of coupled lines with a linear coupling response. The coupling exhibits a slope of 6 dB/octave over multi‐octave bandwidth. The microstrip line is connected to a lumped element compensating network at the coupled port. The compensating network is a low‐pass circuit with a slope of −6 dB/octave. The power handling of the coupler is high due to the coaxial line and the weakly coupled microstrip line. Electromagnetic simulations and analytical formulations are presented. The broadband coupler handles nearly 1 kW of input power. Due to the weak coupling of the microstrip‐coaxial coupler, the lumped element circuit needs to handle

Capacitively coupled plasmas (CCPs) are widely used in plasma processing applications, where efficient power coupling between the radio frequency (RF) source and the plasma is crucial. In practical CCP systems, impedance matching networks (IMNs) are employed to minimize power reflection. However, the presence of coaxial cables can significantly impact plasma impedance and matching performance. We develop a comprehensive simulation framework for the IMN design of CCPs, fully considering the effects of RF coaxial cables. The model self-consistently couples a distributed transmission line (TL) model, a lumped-element circuit model, and an electrostatic particle-in-cell model. This coupled model is used to investigate the impact of coaxial cables on matching performance under various discharge conditions and cable configurations. The simulation results indicate that the optimal power transmission efficiency was achieved after 6 matching iterations. The power coupled to the CCP increased from 2.7 W before matching to 180.9 W, and the reflection coefficient ultimately decreased to 0.003. The results also reveal that neglecting the cables will lead to a decrease in the power dissipated in the CCP. The proposed method demonstrates effectiveness in achieving impedance matching for different gas pressures (75–300 mTorr) and cable lengths. It can be concluded that the matching speed is faster for an appropriate cable length. This work provides valuable insights into the role of TLs in CCP impedance matching and offers a practical tool for optimizing power delivery in realistic CCP systems with RF coaxial cables. [ABSTRACT FROM AUTHOR]

Featured Application: This paper introduces a two-dimensional GNSS signal positioning method for tunnels, characterized by low cost, seamless positioning continuity between the interior and exterior of the tunnel, and ease of engineering implementation. To address the issue of GNSS receivers being unable to function properly in tunnels due to the loss of Global Navigation Satellite System (GNSS) signals, this paper proposes a two-dimensional differential positioning system for tunnel environments based on dual leaky coaxial (LCX) cables with GNSS signal frequency relay forwarding. The system receives mixed GNSS signals from open environments and utilizes the frequency selection capabilities of the MAX2769E chip to separate and generate radio frequency signals at different frequencies corresponding to GPS, BDS, and GLONASS. These signals are then used to drive three ports of the LCX cables, which are laid in parallel within the tunnel. By leveraging the uniform radiation characteristics of the LCX cables, stable GNSS signal coverage is achieved throughout the tunnel. On the receiving end, the GNSS receiver achieves two-dimensional positioning by utilizing inter-satellite pseudorange differences and reference point error correction. The simulation results indicate that the dual T-shaped radiating LCX cables configuration offers excellent positioning accuracy and noise resistance, achieving meter-level positioning accuracy in tunnel environments. [ABSTRACT FROM AUTHOR]

The blast pressure acting on the borehole wall is the basis of the dynamic analysis of rock blasting. The history of blast-induced borehole wall pressure (BWP) is difficult to measure owing to the complex interaction between the blasting load and the borehole wall, and the limitations of the general test system. In this work, the complete history of BWP under air-deck charge was measured for the first time, and the stress-response process was analyzed. PVDF (polyvinylidene fluoride) gages and a charge mode for the test circuit were employed. To improve the testing accuracy, the matching relationships among the parallel capacitor, the equivalent capacitance of PVDF gages, and the parasitic capacitance of the coaxial cable were effectively addressed. The experimental data within the span of 0–0.65 m from the explosive cartridge center show that there are two obvious peaks in the complete history of BWP, the first is a μs-level air shockwave load, followed by a ms-level explosion gas load. The peak of BWP is dominated by the peak of explosion gas (Pg) within the scope of about 0–0.35 m from the explosive cartridge center, while is mainly determined by the peak of air shockwave (Ps) in a farther range. The specific impulse distribution suggests that the explosion energy is mainly consumed in the area within the range of about 0–0.25 m from the explosive cartridge center. The strain rate in the borehole wall induced by air shockwave demonstrates a dynamic response (range of 131.9 ~ 2922.6 s−1), while indicating a quasi-dynamic loading (range of 0.1 ~ 2.1 s−1) when induced by the explosion gas. The findings contribute to expanding the understanding of the stress characteristics of the air shock wave and explosion gas and provide accurate initial loads for numerical simulation related to rock blasting of non-fluid–solid coupling. Highlights: The complete history of borehole wall pressure under air-deck charge was accurately measured by solving the capacitance matching in the test circuit for charge mode. The entire stress response process of the borehole wall rock is revealed. The specific impulse distribution of air shock wave and explosion gas along the borehole axis is obtained. The stress characteristics of borehole wall induced by air shockwave and explosion gas are compared. [ABSTRACT FROM AUTHOR]

A design for manufacturing (DFM) of a well‐performing wideband coaxial filter line using direct metal laser sintering (DMLS) additive manufacturing is proposed. The demonstrated transmission line is an air‐filled coaxial line chosen for low loss and consistent group delay over the bandwidth. Transmission line theory is used first to account for the impact of the shorted stub needed to support the central conductor. Deviations due to parasitics are described to transition the design from an ideal model to a physical prototype. The constraints inherent in DMLS are discussed and accounted for throughout the DFM. This process is demonstrated with a prototype having return and insertion losses of greater than 10 dB and less than 1.64 dB, respectively, over a 5.3:1 bandwidth from 6.4 to 33.9 GHz with a flat group delay of 129 ps ± 7%. [ABSTRACT FROM AUTHOR]

Broadband couplers consist usually of multiple coupled lines that are each a quarter wave‐length long. Herein, in contrast to conventional methods, a short length of a microstrip line is coupled to a coaxial line. The length of the coupled microstrip line is small compared to the wavelength at the lowest operating frequency. The coupling is weak and the microstrip line is λ/8 at the highest operating frequency. The proposed structure resembles a pair of coupled lines with a linear coupling response. The coupling exhibits a slope of 6 dB/octave over multi‐octave bandwidth. The microstrip line is connected to a lumped element compensating network at the coupled port. The compensating network is a low‐pass circuit with a slope of −6 dB/octave. The power handling of the coupler is high due to the coaxial line and the weakly coupled microstrip line. Electromagnetic simulations and analytical formulations are presented. The broadband coupler handles nearly 1 kW of input power. Due to the weak coupling of the microstrip‐coaxial coupler, the lumped element circuit needs to handle <1.5 W. A high‐power coupler has been fabricated for the frequency range of 30 to 500 MHz. It exhibits a coupling response of 56 ± 0.4 dB. [ABSTRACT FROM AUTHOR]

A generator of powerful nanosecond pulses that contains a storage capacitor, a segment of a coaxial cable, and closing and opening semiconductor switches has been developed. With a storage-capacitor charging voltage of 12 kV, the generator allows switching quasi-rectangular voltage pulses with an amplitude of ~26 kV, a rise time of ~4 ns, and a fall time of ~6 ns into a 75 Ω load. The half-maximum pulse duration is ~45 ns, and the "jitter" relative to an external triggering signal is less than 2 ns. The possibility of increasing the generator output power and the duration of output-voltage pulses is shown. [ABSTRACT FROM AUTHOR]

In this article, a compact and portable microwave atmospheric pressure plasma jet (MW‐APPJ) generator based on a coaxial transmission line resonator (CTLR) was proposed. Based on the electromagnetic simulations, the jet generator was designed as a tapered inner conductor structure that ensures plasma generation at low power. A self‐igniting argon (Ar) plasma jet of 10 mm length was generated at an input power of ~20 W and maintained at 2 W. Thanks to the high efficiency of the CTLR structure, plasmas of mixed reactive gases were also realized. Intrinsic plasma parameters and active species were determined using optical emission spectroscopy. Furthermore, the MW‐APPJ device was used to modify the polytetrafluoroethylene surface, and improvement of hydrophilicity was achieved without thermal damage. [ABSTRACT FROM AUTHOR]

The study proposes a multidimensional mathematical modeling of antennas using coaxial cables for 5G, with emphasis on the relationship between cable length, frequency, and VSWR. By employing a final configuration incorporating five circular slots of 6 mm and operating at a frequency of 3.5 GHz, a linear pattern in this relationship was identified. Despite the recognized challenges in accurately modeling VSWR concerning cable length, the study enabled antenna optimization through the determination of the proposed antenna's properties and their respective mathematical correlations. [ABSTRACT FROM AUTHOR]

This article is devoted to the study of microwave-absorbing properties of Co-C coating applied by magnetron sputtering. This article presents the main results of the manufacturing of a Co-C coating by magnetron sputtering, and the evaluation of experimental and computational research data on the relationship between the structure and properties of the obtained films. The structure of Co-C systems has been modeled to control the resulting structures using X-ray diffraction analysis. The structural-phase state of the resulting thin-film Co-C systems and the microwave-absorbing properties of coatings were studied using the transmission line method, consisting of a vector network analyzer, an air coaxial line, a software program, and an external computer. It has been established that on the resulting Co-C film the reflection coefficient in the frequency range of 8.2–12.4 GHz varies in the range of 900 → 718 mU, with reflection losses of −0.86 → −2.57 dB, and a standing wave coefficient of 19 → 6.8. An analysis of the obtained data indicates the presence of losses of electromagnetic energy in the studied frequency range. [ABSTRACT FROM AUTHOR]

The Cosmic Dawn was marked by the formation of the first stars, and preceded the Epoch of Reionization (EoR), when the Universe underwent a fundamental transformation caused by the radiation from these first stars and galaxies. Interferometric 21-cm experiments aim to probe redshifted neutral hydrogen signals from these periods, constraining the conditions of the early Universe. The SKA-Low instrument of the Square Kilometre Array (SKA) is envisaged to be the largest and most sensitive radio telescope at metre and centimetre wavelengths. The latest Aperture Array Verification Systems feature 7-m coaxial transmission lines connecting the low noise amplifiers to optical transmitters at the front of the analogue-receiving chain. An impedance mismatch between these components results in a partially reflected electromagnetic signal, introducing chromatic aberrations into the instrument bandpass. This causes power from the foreground signals to appear at higher delays, potentially contaminating the 'EoR window', a region in which the 21-cm signal should be detectable. We present an end-to-end simulation pipeline for SKA-Low using a composite sky model combining radio foregrounds from the Galactic and Extragalactic All-Sky MWA (GLEAM) Survey, Haslam 408 MHz, and a 1.5-cGpc 21-cm brightness temperature cube generated with the 21cm space simulator. We derive a model for the scattering parameters of a coaxial transmission line in terms of its specifications and bulk material properties. Assuming identical cables of length |$\le 15.0$|  m with impedance mismatch |$\le 10\, \Omega$|⁠ , the reflection is confined below the EoR window. However, we demonstrate that even a 0.1 per cent length tolerance introduces contamination with an absolute fractional difference of ~10 per cent across all accessible k-modes. [ABSTRACT FROM AUTHOR]

An atmospheric pressure plasma source of the microwave plasma pencil type utilizing a coaxial line is presented. The generated plasma takes the form of a cylinder up to about 30 mm long and up to 5 mm in diameter. It is suitable for surface sterilization, surface treatment, and material processing. This study numerically analyzes the electromagnetic radiation emitted by the plasma pencil, which compromises performance and poses safety risks. Electric field distributions, radiation patterns, the ratio of the power entering the discharge to the incident wave power, and the ratio of radiated power to entering power were numerically investigated for different plasma parameters and pencil lengths. Results indicate that increasing electron density, gas temperature, plasma length, and pencil length increases the radiated power by up to more than 60% of the entering power, and the radiation patterns can be highly non-uniform with strong backward lobe. The numerical finding were qualitatively confirmed experimentally. It was also found that it is possible to reduce radiation from the device by using appropriately designed cones, the presence of which does not impede its performance. [ABSTRACT FROM AUTHOR]

A technique for solving the one-port closed coaxial transmission line sample holder scattering equation for complex permittivity inversion for lossy materials is presented. A non-linear least-squares procedure is used for the determination of parameters for the specification of the spectral functional form of the complex permittivity. The method allows for accurate retrieval of many low- and high-permittivity dielectric materials in the frequency range of 1 GHz to 3 GHz inserted into the coaxial cell. Using this method, the complex permittivity of a number of liquids and a Maltese soil known as Bajjad soil have been extracted by measurements using a short terminated coaxial transmission line sample holder. The proposed novel inversion method is mainly based on the reflection coefficient of the test material. The measured results of the complex permittivity of liquid dielectrics such as ethanol, methanol, and TX100 are validated and compared with previously published data obtained from measurements made by the National Physical Laboratory (NPL) using a two-port measurement setup made with the same commercial coaxial transmission line sample holder used in the one-port setup. Since the technique allows broadband measurements, it has been used to characterise the soil dielectric spectrum in the frequency range of 1–3 GHz, which is also compared with results from a two-port setup of the same coaxial line. The experimental results are a validation of the proposed approach for different types of materials. [ABSTRACT FROM AUTHOR]

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Heaviside proposed the telegrapher's equations as an alternative to the Maxwell equations. The telegrapher's equations demonstrated that the electromagnetic waves propagate in coaxial cables at the velocity of light c. The electromagnetic waves are used in Fourier analysis, Laplace transformation, and z transformation. Electromagnetic waves exhibit the physical phenomenon of simultaneous "partial reflection and refraction". Feynman found it tremendously important from the viewpoint of the physical phenomenon and advanced to the studies of quantum electrodynamics and quantum mechanics. In this session, we demonstrate that the physical phenomenon of partial reflection and refraction is an expression of the "law of conservation of energy" of electromagnetic waves, which falls into the category of classical physics. [ABSTRACT FROM AUTHOR]

Abstract The study proposes a multidimensional mathematical modeling of antennas using coaxial cables for 5G, with emphasis on the relationship between cable length, frequency, and VSWR. By employing a final configuration incorporating five circular slots of 6 mm and operating at a frequency of 3.5 GHz, a linear pattern in this relationship was identified. Despite the recognized challenges in accurately modeling VSWR concerning cable length, the study enabled antenna optimization through the determination of the proposed antenna’s properties and their respective mathematical correlations.

Coaxial cables and optical fibers are two types of cylindrical waveguides used in telecommunications. Fiber Bragg gratings (FBGs) have found successful applications in various fields, such as optical communications, fiber lasers, and fiber-optic sensing. In this paper, we propose and numerically investigate the implementations of various fiber Bragg configurations, including uniform, chirped, apodized, and phase-shifted configurations, on coaxial cables to generate the corresponding special types of coaxial cable Bragg gratings (CCBGs). The simulation results of different CCBGs match well with the well-known FBG theories. It is demonstrated that the reflection spectrum of a CCBG can be flexibly tailored by introducing various quasi-periodic perturbations in the permittivity of the dielectric layer along the coaxial cable. The proposed special types of CCBGs with unique characteristics could find potential applications in radio frequency signal processing, communication, and sensing fields. [ABSTRACT FROM AUTHOR]

Marine controlled source electromagnetic (MCSEM) method is widely used to reveal the electrical structure of shallow media below the seafloor. It is an indispensable geophysical means in the exploration of marine oil and gas exploration, natural gas hydrates and seafloor geological structures. The transmitter and receiver in electromagnetic detection equipment need to maintain a high temporal consistency, usually using high-stability pulse-per-second (PPS) generated by GPS or BeiDou navigation modules as a synchronization signal. Coaxial cable is a widely used tow cable, so it is necessary to design a clock synchronization method of marine controlled source electromagnetic transmitter using coaxial cable. This paper proposes a method for synchronizing the internal clocks of the transmitter with PPS using ship-borne power supply when coaxial cable is used as tow cable. In this method, the ship-borne high-power supply outputs a high-voltage AC signal that is synchronized with the 400 Hz signal output from GPS; the coaxial cable transmits AC high power electrical energy and control commands; the AC signal transmitted via the coaxial cable is converted into a stable and continuous 1 Hz signal by step-down, waveform shaping and frequency division for synchronizing the internal time pulses of the transmitter. The test result shows that the 1 Hz signal obtained by this method has a deviation of about 504 ns relative to the PPS. This deviation meets the need of MCSEM transmitter for clock synchronization. [ABSTRACT FROM AUTHOR]

Based on the SOS + MCL approach (SOS—generator with output Semiconductor Opening Switch; MCL—Magnetic Compression Line), a high-power solid-state picosecond system has been developed. The SOS generator forms an initial pulse with a power of 8.5 GW (0.65 MV at a load of 50 Ω) and a duration of 7 ns, which is fed to the input of a magnetic compressor containing 4 lines MCL1–MCL4 connected in series. Structurally, each MCL is a coaxial line and contains ferrite rings placed on its inner conductor and magnetized by an external longitudinal magnetic field. The lines are filled with transformer oil at excess pressure. Each line compresses the pulse in time and increases its peak power. At the output of the last line, MCL4, the peak power increases to 100 GW (2.2 MV at 48 Ω load), and its duration decreases to 100 ps. Record high values of rise rates for voltage, current, and power have been achieved. At a 48 Ω load, the voltage rise rate reaches 27 MV/ns, and the power rise rate reaches 2 TW/ns. In a line with an impedance of 7 Ω, a current pulse with an amplitude of 100 kA and a rise rate of 1.18 MA/ns was obtained. It has been established that the duration of the pulse (full width at half maximum) generated in MCLs corresponds to the double transit time of an electromagnetic wave between the electrodes of the line in the transverse direction. Numerical models have been developed to study the operation of MCLs. Using the models, the internal structure of the process of power amplification in the line was studied, and an assessment was made on the influence of the processes of gyromagnetic precession on the operation of the lines. [ABSTRACT FROM AUTHOR]

Pulse forming lines (PFL) are widely applied in high-power pulsed power generators due to their high energy density and great ability with square waveform modulation. However, the three-cylinder coaxial Blumlein line (tPFL), a commonly used PFL structure, has low energy efficiency due to the difference in impedance of the outer and inner lines. In order to increase the outer line impedance and improve the output waveform of the PFL, a racetrack Blumlein pulse forming line (r-B PFL), formed by two inner cylinders, two middle cylinders, and one outer cylinder that resembles a runway shape, is proposed in this paper. The glycerin energy storage technology and the spiral line technology were applied in the PFL. Moreover, the r-B PFL was tested experimentally after its construction, yielding a satisfactory result. The PFL structure in which multiple middle cylinders share the same outer cylinder achieves a higher outer line impedance, leading to a high energy efficiency of the PFL, which contributes to the PFL development trend toward compactness and miniaturization. [ABSTRACT FROM AUTHOR]

Aimed at the interconnection between coaxial transmission line and substrate‐integrated waveguide (SIW), a wideband coaxial‐to‐SIW transition was proposed and applied in a 1‐to‐4 radial power divider. First of all, a fan‐shaped region was designed on the end of a SIW transmission line. Then, a coaxial transmission line was inserted into this region. To improve the impedance matching at the coaxial port, a feeding ring was designed on the back of the transition where the coaxial line was inserted. Next, the transition was applied in a 1‐to‐4 radial power divider to realize an equal power division. Finally, to validate the correctness of the designs, prototypes were fabricated and measured. For the coaxial‐to‐SIW transition, measured reflection coefficient |S11| was less than −15 dB from 7.84 to 12.18 GHz. Transmission coefficient |S21| was between −0.52 and −0.24 dB. For the 1‐to‐4 radial divider, measured |S11| was less than −15 dB from 7.91 to 12.4 GHz, and the transmission coefficient was around −6.9 dB. Measurement and simulation agreed well with each other. Therefore, the proposed design can be used in coaxial‐to‐SIW interconnection scenarios. [ABSTRACT FROM AUTHOR]

A strong response of nanosystems to the action of weak microwave power through the gap between the sample and the end of the coaxial cable from the microwave generator is detected by measurements at 4.2 K of the conductance of a short-channel -type silicon transistor and samples with a short quantum point contact in a two-dimensional electron gas of GaAs/AlGaAs heterostructures. The conductance response is gigantic in the tunnel mode of the devices, and the sign of the microwave photoconductance outside this mode depended on the mesoscopic state of the sample and the studied range of gate voltage. The nature of the discovered effects is elucidated by modeling mesoscopic transport within the framework of single-particle quantum mechanics and the Landauer formula as well as by analyzing the basic circuits of electrical control of the semiconductor device. The main reason for the response of nanosystems to microwave exposure is forced in-phase charge oscillations in contacts to the semiconductor due to capacitive coupling in the near metallic environment of the sample. [ABSTRACT FROM AUTHOR]

Silica composites with low dielectric constants have broad application prospects in the fields of low dielectric and thermal insulation materials. However, silica composites still face challenges such as strong water absorption and strict storage conditions in practical applications. Modification of SiO2@quartz fiber composites was conducted with hydrophobic modifiers (hexamethyldisilazane HMDS, stearic acid, sodium dodecyl sulfate) to study the effects of type and mass fraction of hydrophobic modifiers on the hydrophobic and dielectric properties of the composites. The hydrophobic-modified composites were made into coaxial cables to study the effect of heat treatment on the performance of the cables. The results show that the 3% HMDS-modified composite have the best hydrophobic modification with contact angle of 151.6°, the lowest contact angle is 132.6° after 240 days of storage, and the dielectric constant is as low as 1.87 after 200 °C calcination. The hydrophobic-modified composites were made into coaxial communication cables, and the cables had a voltage standing wave ratio of 1.48, an attenuation value of 1.56 dB, and a characteristic impedance of 48 Ω. The hydrophobic-modified composite materials exhibit excellent cable performance, demonstrating potential application value in communication cables and other fields. [ABSTRACT FROM AUTHOR]

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This article proposes a dual mode dual-polarized antenna configuration for IRNSS and fifth generation (5G) applications, operating at a frequency of 3.5 GHz based on characteristic mode analysis (CMA), and aims to provide broadband dual-polarized functionality. The original design of the antenna is a traditional patch antenna, and its dual-polarized features are determined using characteristic mode analysis. The full-wave method is used to stimulate both orthogonal modes using a 50 Ω coaxial input line at 3.5 GHz. In this design, the circular patch has been extended into an elliptical patch through a process of mode separation. The circular patch exhibits resonance at a frequency of 2.5 GHz, whereas the extended elliptical radiator demonstrates two resonance modes at 2.5 GHz and 3.5 GHz. The operational mechanism is elucidated by modal analysis and characteristic angle. This antenna operates on two different frequencies at the 2.5 GHz IRNSS band with horizontal polarization and the 3.5 GHz 5G service with vertical polarization. The maximum gain achieved with these frequency ranges is 5.31 dBi and 4.72 dBi, respectively. A ring resonator is chosen to improve the axial ratio and impedance bandwidth of the suggested prototype. The antenna's ground plane is shaped like a rectangle and features a V-shaped slot in the radiating patch. The antenna's physical footprint is 50 mm × 50 mm × 1.6 mm and an FR4 dielectric substrate serves as its foundation. Through its interaction with a PIN diode, the diode modifies the polarization of the antenna. The antenna functions as a right-handed circular polarization (RHCP), when the diode is operational. The bandwidth from 4.3 to 7.5 GHz is covered. On the other hand, it generates linear polarization (LP) between 4.2 and 5.3 GHz. The experimental antenna is evaluated and examined for its performance characteristics. The simulations are carried out utilizing the CST simulator. A prototype antenna has been manufactured and its performance has been validated against simulated findings. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) coupling effects including both inductive and capacitive coupling have long been an essential problem in broad-band spectral electrical impedance tomography (sEIT) measurements at the field scale. Efforts have been made to remove EM coupling numerically or to suppress the effects by modified data acquisition strategies. For near-surface applications with relatively small survey layouts, inductive coupling can be well removed in the mHz to kHz frequency range. With the use of shielded coaxial cables and so-called active electrodes where the amplifiers are mounted at the electrodes, capacitive coupling in sEIT measurements can also be reduced. However, it remains challenging to cope with capacitive coupling between the cable shield and the ground, especially in resistive field conditions. The aim of this study is to deal with this type of capacitive coupling effect by identifying and filtering out sEIT measurements that are strongly affected by capacitive coupling. Based on a correction method for capacitive coupling proposed in a previous study, an approach to estimate measurement errors due to capacitive coupling is presented first. In the second step, a workflow was proposed to calculate the capacitive coupling strength (CCS) for each electrode configuration, which is defined as the ratio of the imaginary part of the impedance induced by capacitive coupling and the imaginary part of the impedance due to the subsurface electrical conductivity. In the final step, measurements with low CCS were selected for inversion and the results were compared with inversion results obtained using the previously developed correction approach. It was found that the filtering method based on CCS is more capable in tackling capacitive coupling compared to using model-based corrections. Spectrally consistent sEIT results up to kHz were obtained using the newly developed filtering method, which were not achieved in previous work using model-based correction. [ABSTRACT FROM AUTHOR]

This research introduces an innovative phase inverter (PI) design using a substrate‐integrated coaxial line (SICL). The proposed SICL PI is achieved by bisecting the SICL with two I‐shape slots embedded on the top and bottom broad‐side walls of the SICL. The central signal strip is also bisected, and the divided strips are diverted to the top/bottom walls on the other side of the slots through one or two via‐holes. Thus, phase inversion is obtained by swapping the potentials of the central strip and the top/bottom walls. A transition between the feeding SMA and the SICL is also developed to facilitate measurements. Experimental results demonstrate that the proposed SICL PI exhibits a fractional bandwidth (FBW) of 2.74–4.66 GHz (51.8%) under the criteria of return losses greater than 10 dB, insertion losses less than 0.5 dB, and phase deviation within ±15°. [ABSTRACT FROM AUTHOR]

The investigation into the dielectric properties of transformer oils has been a focal point in both historical and contemporary electric insulation technology as high-voltage applications have greatly benefited from the continuous research efforts in this field. The dielectric permittivity is one of the factors to be negotiated when discussing the electric insulation of any material. This work aims to showcase a new short-circuited coaxial cable method to evaluate the complex dielectric permittivity of palm, sunflower and rapeseed oil and review other previously used measurement techniques. Mainly, the test was performed using a sample holder that represents a short-ended coaxial cable filled with the test material which is connected to one port of a vector network analyser. The measurements of the input impedance for various oil samples were conducted at frequencies ranging from 1 MHz to 10 MHz. The technique uses the value of the input impedance which depends on the reflected signals from the test sample to the network analyser, consequently, the value of the dielectric permittivity and dielectric loss have been calculated using the short circuit impedance formula which involves numerical methods to get the results which shows that this method can be used as an alternative to investigate the oils insulation parameters as it provides smooth results for permittivity without any divergence, ensuring more reliable and consistent measurements as well as providing high accuracy in determining the permittivity of materials. [ABSTRACT FROM AUTHOR]

Anatomy-specific radio frequency receive coil arrays routinely adopted in magnetic resonance imaging (MRI) for signal acquisition are commonly burdened by their bulky, fixed, and rigid configurations, which may impose patient discomfort, bothersome positioning, and suboptimal sensitivity in certain situations. Herein, leveraging coaxial cables' inherent flexibility and electric field confining property, we present wireless, ultralightweight, coaxially shielded, passive detuning MRI coils achieving a signal-to-noise ratio comparable to or surpassing that of commercially available cutting-edge receive coil arrays with the potential for improved patient comfort, ease of implementation, and substantially reduced costs. The proposed coils demonstrate versatility by functioning both independently in form-fitting configurations, closely adapting to relatively small anatomical sites, and collectively by inductively coupling together as metamaterials, allowing for extension of the field of view of their coverage to encompass larger anatomical regions without compromising coil sensitivity. The wireless, coaxially shielded MRI coils reported herein pave the way toward next-generation MRI coils. [ABSTRACT FROM AUTHOR]

The high‐power characteristic of the coaxial to waveguide transition plays an important role in modern communication and radar systems. In this letter, a novel design of a high‐power transition from a 50 Ω coaxial line with an N‐type connector to a WR‐90 rectangular waveguide. The power handling capability (PHC) of the proposed structure is significantly enhanced by a cone‐shaped excitation probe with a bold end, a transitional cavity, and a mode conversion cavity with a curved shorted back wall. The simulated results reveal that the transition possesses high PHC of 257 kW at 8.5 GHz, which is the upper limit of the power tolerance for the N‐type connector. The measured results show that the return loss and insertion loss are better than 15 and 0.15 dB, respectively, in the range of 7.96–9.16 GHz. In addition, experimental validation confirms the normal operation of the structure under a 250 kW power level test, demonstrating the applicability of the proposed transition in high‐power microwave systems. [ABSTRACT FROM AUTHOR]

Cryogenic qubit controllers (QCs) are the key to build large-scale superconducting quantum processors. However, developing scalable QCs is challenging because the cooling power of a dilution refrigerator is too small (~10 μW at ~10 mK) to operate conventional logic families, such as complementary metal-oxide-semiconductor logic and superconducting single-flux-quantum logic, near qubits. Here we report on a scalable QC using an ultra-low-power superconductor logic family, namely adiabatic quantum-flux-parametron (AQFP) logic. The AQFP-based QC, referred to as the AQFP-multiplexed QC (AQFP-mux QC), produces multi-tone microwave signals for qubit control with an extremely small power dissipation of 81.8 pW per qubit. Furthermore, the AQFP-mux QC adopts microwave multiplexing to reduce the number of coaxial cables for operating the entire system. As a proof of concept, we demonstrate an AQFP-mux QC chip that produces microwave signals at two output ports through microwave multiplexing and demultiplexing. Experimental results show an output power of approximately −80 dBm and on/off ratio of ~40 dB at each output port. Basic mixing operation is also demonstrated by observing sideband signals. [ABSTRACT FROM AUTHOR]

The establishment of the mid-infrared and terahertz free-electron laser (MIR/THz FEL) facility is ongoing at the PBP-CMU Electron Linac Laboratory (PCELL) in Chiang Mai University. The facility utilizes an S-band radio-frequency (RF) gun and a linear accelerator (linac) to generate and accelerate electron bunches. These electron bunches are accelerated in the RF gun and the linac using RF pulses with a frequency of 2856 MHz. Measuring the RF properties becomes essential, as the RF pulse information can be utilized to estimate the electron beam properties. To achieve the measurement results, we employed an RF measurement system comprising directional couplers, coaxial cables, attenuators, a crystal detector, and an oscilloscope. Prior to conducting measurements, the crystal detector and RF equipment were calibrated and characterized to ensure precise and reliable results. The electron beam energy estimation using the measured RF power was compared with the measured beam energies. The gun and the linac were operated with an absorbed RF power of 1.52 MW and an input power of 1.92 MW, respectively. The estimated electron beam energies were found to be 2.18 MeV and 15.0 MeV, respectively, closely aligning with the measured beam energies of 2.1 MeV and 14.0 MeV after the gun and linac acceleration. These consistent energy values support the reliability of our RF power measurement system and procedure. [ABSTRACT FROM AUTHOR]

This article presents the modeling and realization of a compact substrate integrated coaxial line (SICL) based butler matrix operating at 5 GHz for beam-forming applications. The proposed 4 × 4 butler matrix is developed using SICL-based hybrid coupler, crossover, and phase shifter. A compact 90 ∘ coupler comprising of center tapped unequal stubs is designed to enhance the size reduction as well as to extend the out of band rejection. Wideband SICL-based crossover operating from DC to 10 GHz is conceived for the proposed butler matrix using a plated through hole as transition. The SICL crossover features very high measured isolation of 65 dB owing to the reduction in coupling between the two signal paths within a lateral footprint of only 0.034 $\lambda_g^2$. A meandered SICL-based line is used in order to provide the necessary 45 ∘ and 0 ∘ phase shift to realize the butler matrix. The fully shielded and self-packaged compact 4 × 4 SICL-based butler matrix is fabricated and experimentally validated to operate at 5 GHz. [ABSTRACT FROM AUTHOR]

Parallel imaging is one of the key MRI technologies that allow reduction of image acquisition time. However, the parallel imaging reconstruction commonly leads to a signal‐to‐noise ratio (SNR) drop evaluated using a so‐called geometrical factor (g‐factor). The g‐factor is minimized by increasing the number of array elements and their spatial diversity. At the same time, increasing the element count requires a decrease in their size. This may lead to insufficient coil loading, an increase in the relative noise contribution from the RF coil itself, and hence SNR reduction. Previously, instead of increasing the channel number, we introduced the concept of electronically switchable time‐varying sensitivities, which was shown to improve parallel imaging performance. In this approach, each reconfigurable receive element supports two spatially distinct sensitivity profiles. In this work, we developed and evaluated a novel eight‐element human head receive‐only reconfigurable coaxial dipole array for human head imaging at 9.4 T. In contrast to the previously reported reconfigurable dipole array, the new design does not include direct current (DC) control wires connected directly to the dipoles. The coaxial cable itself is used to deliver DC voltage to the PIN diodes located at the ends of the antennas. Thus, the novel reconfigurable coaxial dipole design opens a way to scale the dynamic parallel imaging up to a realistic number of channels, that is, 32 and above. The novel array was optimized and tested experimentally, including in vivo studies. It was found that dynamic sensitivity switching provided an 8% lower mean and 33% lower maximum g‐factor (for Ry × Rz = 2 × 2 acceleration) compared with conventional static sensitivities. [ABSTRACT FROM AUTHOR]

This work deals with wave propagation into a coaxial cable, which can be modelled by the 3D Maxwell equations or 1D simplified models. The usual model, called the telegrapher's model, is a 1D wave equation of the electrical voltage and current. We derived a more accurate model from the Maxwell equations that takes into account dispersive effects. These two models aim to be a good approximation of the 3D electromagnetic fields in the case where the thickness of the cable is small. We perform some numerical simulations of the 3D Maxwell equations and of the 1D simplified models in order to validate the usual model and the new one. Moreover, we show that, while the usual telegrapher model is of order one with respect to the thickness of the cable, the dispersive 1D model is of order two.

We report a comparative study on microwave control lines for a transmon qubit using (i) flexible stripline transmission lines and (ii) semi-rigid coaxial cables. During each experiment, we performed repeated measurements of the energy relaxation and coherence times of a transmon qubit using one of the wiring configurations. Each measurement run spanned 70–250 h of the measurement time, and four separate cooldowns were performed so that each configuration could be tested twice. From these datasets, we observe that changing the microwave control lines from coaxial cables to flexible stripline transmission lines does not have a measurable effect on coherence compared to thermal cycling the system or random coherence fluctuations. Our results open up the possibility of large-scale integration of qubit control lines with integrated component with planar layouts on flexible substrate. [ABSTRACT FROM AUTHOR]