Traveling wave tube

Complex nonconstant envelope high-order digital modulation schemes used in modern communication satellites bring new requirements for the linearity and power efficiency of the on-board traveling-wave tubes (TWTs). As a result, a reassessment of typical TWT specifications is required. A digital system-level figure-of-merit, the total degradation, is proposed. It accounts for the characteristics of any coded signaling scheme, as well as

Complex payload architectures, together with the use of high-order digital modulations and advanced coding schemes, call for an accurate evaluation of traveling-wave tube amplifier (TWTA) nonlinearity impairments. To assess in a simple yet accurate manner the level of signal distortion generated by the TWTA nonlinearity, we adopt a correlation-based methodology. The proposed method provides an accurate evaluation of the TWTA

— A coupled transmission line (TL)-based slow-wave structure is presented and characterized. This TL is a modified ring-loop structure referred to as curved ring bar. It inherits the features of the ring-loop structure, but includes elliptic loops to enhance the axial electric field for TM 01 mode. The structure demonstrates wideband behavior and is especially designed for high-power traveling wave tube amplifiers. It is characterized using a pair of uniform and identical coupled TLs utilized to achieve desired dispersion characteristics. This characterization explains the dispersion curves and interaction impedance. A simple way to derive dispersion behavior in terms of circuit parameters is also provided. A traveling wave tube (TWT) model is also presented that gives an output power of 1 MW across 1.8–2.4 GHz. It is noted that the designed TWT provides a bandwidth of 20% and delivers an output power of 1 MW, larger than previously reported in S-band.

ABSTRACT Advanced simulation tools were used to design major components for a 95-GHz traveling-wave tube (TWT) providing approximately 1-kW of average power. This output power would be challenging, if not impossible, using a fundamental mode circuit TWT design, because of beam-current density and thermal-mechanical-stability issues. We addressed these limitations using an overmoded interaction circuit. The program investigated the circuits' thermal and electrical performance, including the effect of multiple-propagating modes and spurious oscillations. We also completed the designs for the electron gun and periodic permanent magnet. The design results for the 1-kW 95-GHz TWT are promising.

Complex nonconstant envelope high-order digital modulation schemes used in modern communication satellites bring new requirements for the linearity and power efficiency of the on-board traveling-wave tubes (TWTs). As a result, a reassessment of typical TWT specifications is required. A digital system-level figure-of-merit, the total degradation, is proposed. It accounts for the characteristics of any coded signaling scheme, as well as

Summary form only given, as follows. The terahertz region of the electromagnetic spectrum 300-3000 GHz in frequency or 0.1-10 mm free space wavelength) has enormous potential for high-data-rate communications, advanced electronics materials spectroscopy, space research, medicine, biology, surveillance, and remote sensing. A critical roadblock to full exploitation of the THz band is a paucity of compact, powerful (1-1000 mW) coherent radiation sources that are efficient (> 1%), frequency agile (instantaneous bandwidth > 1%), reliable and comparatively inexpensive. To address this need, we are investigating folded wavegulde traveling wave tubes (FWGTWTs). These FWCTWTs combine the power density and high frequency advantages of vacuum electronics with the powerful microfabrication methods of MEMS and solid state electronics.

This paper discusses the suitability of using a multiport amplifier (MPA) for multimedia multi-beam telecommunication operation with power flexibility requirements. With this aim, a Ka-band MPA has been characterized in a realistic environment for telecommunication operation. Simulation and measurement results are discussed and the performances of the MPA based architecture and a classical architecture (with one power amplifier per beam) is compared in terms of power consumption. The MPA proves to be an interesting solution since it offers flexibility with lower power consumption and less equipment

Abstract—In this paper, results of different models are com-pared for calculating effective, cold-circuit (beam-free) phase velocities and interaction impedances of folded waveguide (FW) slow wave circuits for use in millimeter-wave traveling wave tubes (TWT). These ...

— We introduce a new slow wave structure referred to as half-ring helix for traveling wave tube (TWT) applications. This new structure is shown to achieve 27% size reduction with concurrent nondispersive response across the S-band. A 10-dB gain improvement was also observed as compared with the standard helix TWT. Moreover, the designed traveling wave tube can attain a maximum saturated output power of 1 KW and a bandwidth of 0.75 GHz (2.5–3.25 GHz). This improved gain and power handling, along with a satisfactory bandwidth, makes the structure attractive as compared with conventional ones. In this paper, we present the TWT design with numerically computed cold test results and evaluate its hot test performance using particle-in-cell simulations. Index Terms— Slow wave structure (SWS), traveling wave tube (TWT), traveling wave tube amplifiers (TWTAs).

A simple method of estimating the attenuation constant due to conductivity losses in a helix slow-wave structure was developed that uses the inputs like the quality factor and dispersion characteristics obtained from the eigen-mode solutions of 3D HFSS modeling of the structure. The method was benchmarked against two practical structures published in the literature, and applied in demonstrating the computation of circuit loss in a segment-loaded broadband helical slow-wave structure. It was seen that proximity of segment to the helix increases the circuit loss significantly thereby affecting the device efficiency. A study of different parameters that affect the circuit attenuation was also carried out.

GaN-based microwave power amplifiers have been identified as critical components in Sandia's next generation micro-Synthetic-Aperture-Radar (SAR) operating at X-band and Ku-band (10-18 GHz). To miniaturize SAR, GaN-based amplifiers are necessary to replace bulky ...

This paper presents a detailed analysis of traveling wave tube (TWT) helical slow-wave structures (SWSs) using three-dimensional (3-D) electromagnetic simulators. The main advantages of this approach are its capability to take into account the real 3-D geometry of this complex structure, and consequently to eliminate the approximations used in the analytical approach. In addition, it provides higher accuracy than experimental

The terahertz region of the electromagnetic spectrum 300-3000 GHz in frequency or 0.1-10 mm free space wavelength) has enormous potential for high-data-rate communications, advanced electronics materials spectroscopy, space research, medicine, biology, surveillance, and remote sensing. A critical roadblock to full exploitation of the THz band is a paucity of compact, powerful (1-1000 mW) coherent radiation sources that are efficient (>