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This paper presents the preliminary analysis of a folded waveguide (FWG) slow wave structure (SWS) for 160GHz traveling wave-tube amplifier. Traveling wave-tube amplifiers operational in the D band of the millimeter wave frequencies are the apt candidates for their application in the point-to-point backhaul communication of 5G and above networks, and in the inter-satellite communication in space. The dispersion analysis of the unit cell of the FWG SWS presented in this paper effectively describes the dependence of the critical design parameters, namely the operational frequency range, bandwidth, and phase velocity on the dimensional variables. An operational bandwidth of 20GHz ranging from 155GHz-175GHz has been successfully obtained with a RF phase velocity of 0.244 times velocity of light in this paper.

A W Band staggered double vane (SDV) loaded traveling wave tube amplifier (TWTA) with two sections separated by a lossy dielectric loaded rectangular wave guide is studied in this paper. The dispersion characteristics and transient analysis of the slow wave structure are analyzed in Computer Simulation Technology Microwave studio (CST MWS) and High Frequency Software Simulator (HFSS). In this amplifier, we propose to use Bragg reflectors on both sides of the slow wave structure (SWS), at the windows for the sheet beam at the electron gun and collector ends; this increases the impedance bandwidth of the RF structure. The attenuator section is comprised of a rectangular waveguide loaded on either side with single lossy dielectric material spanning over 5.5 pitches. The loss profile of the attenuator and loss magnitude is optimized to provide a 20dB loss in separating the input and output sections. A bandwidth of 15GHz ranging from 90-105GHz is obtained through the analysis. In the PIC simulations, a sheet beam of 50mA current is fed with an operating voltage of 18.3kV. The TWTA yields 20dB gain in the 90-105GHz range.

In this paper, a scheme for bandwidth and gain enhancement of 0.220 THz traveling wave tube amplifier (TWTA) is presented. A two-section staggered double vane (SDV) slow wave structure (SWS) loaded with two period Bragg reflector at both the ends is analyzed in this paper. The attenuator section that separates the input and output section comprises of a six pitch long rectangular waveguide loaded with lossy material on top and bottom walls. Velocity taper is provided at all transitions for improved impedance match. The dispersion characteristics were computed through Eigen mode analysis in Microwave studio module of Computer Simulation Technology (CST) and the results were validated using Ansys’s High Frequency Software Simulator (HFSS). 15dB transmission and reflection loss across a bandwidth of 45 GHz from 0.205–0.250 THz is provided by the design optimized attenuator while separating the input and output sections. Through particle in cell (PIC) simulations in CST Particle studio, beam wave interaction between input RF signal and a sheet electron beam is studied. The proposed TWTA yields 22dB gain across the bandwidth of 32 GHz ranging from 0.218–0.250 THz range for a beam current of 30 mA fed at an operating voltage of 19kV.

Modern day impulse-based systems, radar imaging, surveillance systems, internet of things (IoT) and on body sensors find Ultra-Wide Band (UWB) planar antennas as a suitable device to operate at low power and low interference metrics with larger bandwidth, ease of fabrication, and low cost. In this paper a compact planar Coplanar Waveguide (CPW) fed antenna for Ultra-Wideband applications is proposed. The antenna features tapered slots of different shapes making the structure an asymmetrical co-planar waveguide. The antenna was designed and simulated using Matlab. The coplanar antenna is mounted on Rogers RO 3202 substrate. The antenna yields an ultra-wide bandwidth of 11.279 GHz with 10 dB return loss from 2.3617 to 13.641 GHz. The antenna provides acceptable radiation patterns and Voltage Standing Wave Ratio (VSWR) less than 2 dB in the range of 2.28 to 12.769 GHz.

This paper presents a metamaterial approach based ultra-wideband patch antenna using a different split-ring resonator structure. The proposed split-ring resonator is constructed on a 0.43mm thick RT Duroid substrate above a partly covered ground plane. The radiating element comprises of a rectangular geometry with arc-shaped structures at the shorter edges, with an overall dimension of 39x30 mm2. The proposed antenna provides a much favorable radiation pattern with a very efficient impedance matching across a wide bandwidth of 3-44 GHz, making it highly suitable for its operation at and beyond ultra-wideband applications and 5G communications. This paper discusses the antenna's design and the parametrical studies performed using available simulation tools.

The tape helix slow wave structures used in travelling wave tube (TWT) amplifiers are exploited for use as radiating devices through the fast wave analysis. The dispersion equation is derived from accurate boundary conditions that neither involve assumptions on the current density distribution, nor considers a defined distribution function for a dielectric loaded tape helix slow wave structure surrounded by a conductor or a conductor placed inside the tape helix. Analytical computation of the dispersion characteristics of both the structures revealed the presence of fast wave modes usable for applications such as antennas.