Design and development of rigid coaxial line based variable stub tuner

This paper presents a novel design of rigid coaxial line based variable stub tuner. It incorporates controlled drive for the movement of shorting ring along the length of the stub inside the coaxial line. The ring is housed inside stub through linear slot over the coaxial conductor. Inbuilt slot at outer conductor of coaxial line introduces undesirable discontinuity which deteriorates the performance of the stub. It needs to be compensated to get the desirable performance of tuner. The effect of discontinuity has been analyzed using circuit modelling and compensated in design itself for the desired performance. The compensated tuner has been fabricated and tested where test results are found as return loss better than 25 dB and Voltage Standing Wave Ratio (VSWR) in between 1.1 and 1.9 in the frequency range of 80–850 MHz. The presented work is useful for the development of high power stub tuner in the range of High Frequency (HF), Very High Frequency (VHF) and Ultra High Frequency (UHF) which is an interest of wide spread applications in areas of communication, defence, satellite, radar, tokamak etc.

New synthetic fiber armored cable for freezing-in thermal ice probes

A series of new synthetic armored cables were developed and tested to ensure that they were suitable for use with the RECoverable Autonomous Sonde (RECAS), which is a newly designed freezing-in thermal ice probe. The final version of the cable consists of two concentric conductors that can be used as the power and signal lines. Two polyfluoroalkoxy jackets are used for electrical insulation (one for insulation between conductors, and the other for insulation of the outer conductor). The outer insulation layer is coated by polyurethane jacket to seal the connections between the cable and electrical units. The 0.65 mm thick strength member is made from aramid fibers woven together. To hold these aramid fibers in place, a sheathing layer was produced from a polyamide fabric cover net. The outer diameter of the final version of the cable is ~6.1 mm. The permissible bending radius is as low as 17–20 mm. The maximal breaking force under straight tension is ~12.2 kN. The cable weight is only ~0.061 kg m−1. The mechanical and electrical properties and environmental suitability of the cable were determined through laboratory testing and joint testing with the probe.

Loss Simulation Analysis and Optimization of U-Groove Leaky Coaxial Cable

Leakage coaxial cable is a kind of coaxial cable with various slot structures on the outer conductor of the cable. It can transmit signal and transmit or receive signal and has dual functions of signal transmission line and antenna. Leakage cable has the advantages of strong environmental adaptability, uniform signal coverage, and less attenuation. It is not only widely used in closed or semiclosed space with high signal reception quality, such as tunnels, subway, underground parking lot, and elevators but also can realize security and theft-proof monitoring and protection in some areas, such as oil wells, mining fields and natural resource protection areas, military fortresses, museums, airports, banks, and schools. This paper introduces the classification and electrical parameters of leaky coaxial cables. On the basis of U-groove leaky coaxial cables, the relationship between the parameters of groove holes in U-groove and the loss of leaky coaxial cables is simulated and analyzed by HFSS software. The improved method of U-groove structure is obtained, and the curved hook-groove leaky coaxial cables are designed according to this method. The simulation results show that the coupling loss of the cable is lower than that of the U-groove leakage cable, and the transmission loss is still within the national standard. It lays a theoretical foundation for the design and development of leaky coaxial cable with low coupling loss.

Electrodynamic Parameters of a Coaxial Cable at Bipolar Pulses Propagation

All-in-interworking technology, based on IEEE 802.3 standard, was mainly developed for the separable media cabling and data transmission speed increase. Although the high-speed networking is already provided by a fiber optic cable, coaxial guides are in demand for similar applications. Time-domain analysis is undertaken to estimate electrodynamic states of inner and outer guiding conductors at periodic bipolar pulses propagation on a coaxial cable. An electric current density distribution on the cross-section of the inner conductor is obtained from a solution of Maxwell equations under periodic boundary conditions that are prescribed by a product of two functions. The first one is introduced implicitly for a profile of surface current density in the axial direction, while the other determines this profile transient states. As for shielding braid, which is the cable outer conductor, its current density distribution is derived from an analysis of field harmonics that penetrate into conductive subsurface layers under similar boundary conditions. It is also shown that prescribed implicative boundary conditions for both conductors allow to obtain, at least under auxiliary assumption, some completed formulae useful to the estimation of the pulses duration admissible decrease at their transmission on the coaxial cable. The paper contains some comparative and numerical results as well

Dual-Wide-Band Dual Polarization Terahertz Linear to Circular Polarization Converters based on Bi-Layered Transmissive Metasurfaces

Transmissive metasurface-based dual-wide-band dual circular polarized operation is needed to facilitate volume and size reduction along with polarization diversity for future THz wireless communication. In this paper, a novel dual-wide-band THz linear polarization to circular polarization (LP-to-CP) converter is proposed using transmissive metasurfaces. It converts incident X polarized waves into transmitted left-hand circular polarized (LHCP) and right-hand circular polarized (RHCP) waves at two frequency bands. The structure consists of bi-layered metasurfaces having an outer conductor square ring and three inner conductor squares diagonally intersecting each other. The proposed converter works equally well with incident Y polarizations. Operational bandwidths for the dual-band LP-to-CP are 1.16 THz to 1.634 THz (34% fractional bandwidth) and 3.935 THz to 5.29 THz (29% fractional bandwidth). The electromagnetic simulation was carried out in two industry-standard software packages, High Frequency Structure Simulator (HFSS) and Computer Simulation Technology (CST), using frequency and time domain solvers respectively. Close agreement between results depicts the validity and reliability of the proposed design. The idea is supported by equivalent circuits and physical mechanisms involved in the dual-wide-band dual polarization operation. The impact of different geometrical parameters of the unit cell on the performance of LP-to-CP operation is also investigated.

Fully reconfigurable hexagonal-shaped comb-line filterplatform for prototyping and education purposes

In this paper, a completely reconfigurable comb-line bandpass filter is presented. Due to the modularity, different standard coupling matrix topologies like the folded form, cascaded triplets, and the cul-de-sac form can be implemented and tested. Circuit-based coupling matrices like the extracted pole topology can easily be realized as well. Different types of input-/output- and cross-couplings can be examined before fabrication of a fixed filter set-up takes place. Furthermore, the proposed filter platform can be used to construct a diplexer. By using different heights of the inner and outer conductor of the coaxial resonators, arbitrary center frequencies in the range between 1 and 4 GHz can be realized. Various types of input couplings are available and proposed here to achieve bandwidths between 10 and 110 MHz. A variety of cross-coupling apertures able to realize transmission zeros are presented as well.