A sheet-beam coupled-cavity traveling wave tube has produced over 10 kW of peak power at a center frequency of 34 GHz, with a 3-dB bandwidth of almost 5 GHz. The power of this amplifier is an order of magnitude higher than state-of-the-art conventional amplifiers of comparable frequency, bandwidth, and operating voltage $({ . This unprecedented performance is made possible by a unique, Naval Research Laboratory (NRL)-developed sheet electron beam along with a novel slow-wave interaction structure. High-current, low-voltage operation provides high gain per unit length and allows an interaction structure ${ long to be used to achieve the desired gain of 15 dB at saturation. Measured performance agrees well with 3-D particle-in-cell simulations.

Demonstration of a Wideband 10-kW Ka-Band Sheet Beam TWT Amplifier

A sheet-beam coupled-cavity traveling wave tube has produced over 10 kW of peak power at a center frequency of 34 GHz, with a 3-dB bandwidth of almost 5 GHz. The power of this amplifier is an order of magnitude higher than state-of-the-art conventional amplifiers of comparable frequency, bandwidth, and operating voltage (<;20 kV). This unprecedented performance is made possible by a unique, NRL-developed sheet electron beam along with a novel slow-wave interaction structure. High-current, low-voltage operation provides high gain per unit length and allows an interaction structure <; 5-cm long to be used to achieve the desired gain of 15 dB at saturation. Measured performance agrees well with 3-D particle-in-cell simulations.

Demonstration of a wideband 10-kW Ka-band sheet beam TWT amplifier

The concept of long-range microwave power transmission (MPT) has been driven by the desire to remotely power satellites, drones, or some mobile facilities. The advantage of long-range MPT is power transmission over a long distance without the need to deploy a wired power network. However, the overall efficiency, robustness, directional radiation (DR), and so on are still issues that limit the application and further research. In this framework, the key challenges in designing transmitters, DR, and receivers that can guarantee high efficiency and precise tracking for long-range MPT have been acknowledged. Owing to the complexity, the design of the MPT systems remains an open research question. Focusing on the existing constraints, this article not only elaborates on the current major research topics and discusses the development trends but also reviews the design approaches proposed in the state of the art for long-range MPT. This power transmission mechanism shows essential meanings of application in daily life, and the current research status and development prospects for MPT are also presented in this article.

Long-Range Wireless Microwave Power Transmission: A Review of Recent Progress

To meet the need to transmit increasingly massive volumes of data, a more than 3 kW continuous wave (CW) Ka-band sheet beam traveling-wave tube (SB-TWT) is reported for the first time. Working under unsaturated drive, the maximum gain obtained is 29 dB with a sheet beam of 30.9 kV, 0.82 A, and the efficiency exceeds 24% with a single-stage collector depressed to −15 kV. The 1-dB bandwidth reaches 6 GHz from 26 GHz to 32 GHz and the bandwidth with output power greater than 2 kW can even reach 7GHz from 26 GHz to 33 GHz. The realization of 99.8% static transmission as well as over 97% actual CW transmission of sheet beam is verified successfully, which benefits from adopting periodic cusp magnet (PCM) focusing, and thereby total weight is less than 15 kg. The relevant experimental details are introduced in this letter.

Continuous Wave Operation of a Ka-Band Broadband High-Power Sheet Beam Traveling-Wave Tube

In this paper, a theoretical model is presented for the double-slot coupled-cavity slow wave structure (CCSWS). By matching boundary conditions in conjunction with Green's function technique and moment method, the formulas for discussing the high frequency characteristics of the SWS, including dispersion and interaction impedance, are given. This model is validated by comparing its results of two typical double-slot CCSWS operating in X-band, one with inline slots and the other with staggered slots, with those obtained by computer simulation using Ansoft HFSS code. Comparison is also made with the experimental data as well as the equivalent circuit model of a particular double-slot CCSWS. The results show that the theoretical method strikes a better balance between the accuracy and the calculation efficiency than other methods.

Theory, Simulations, and Experiments of the Dispersion and Interaction Impedance for the Double-Slot Coupled-Cavity Slow Wave Structure in TWT

A family of 700-W Ka-band Coupled-Cavity Traveling-Wave Tubes (CCTWTs) has been successfully developed, built, and tested at Communications and Power Industries (CPI). These CCTWTs are capable of up to 700-W Continuous Wave (CW) output power with 2.0 GHz of instantaneous bandwidth. They were built with the intended use for the commercial satellite and military communication market. We discuss the design and successful demonstration of the family of CCTWTs, including the VTA-6428S2B prototype which achieved over 700-W (783-W maximum output power) with an overall efficiency reaching as high as 52%.

Dennis San Pedro

Papers

700 W Ka-band Coupled-Cavity Traveling Wave Tubes (CCTWT) for communication