A review of various proposed schemes to increase the reliability and life span of solid-state lighting (SSL) systems is presented in this article. Since the mainstream devices employed for such lighting systems are inorganic, high-power light-emitting diodes (LEDs), which are devices characterized by their very long life, most of the questions in reliability and endurability arise from the electronic offline circuit driving the LEDs. Issues regarding the limited reliability of specific components, such as electrolytic capacitors, are introduced. Several power-?conversion configurations aimed to capacitance reduction and capacitor technology exchange are put forward as alternative solutions for implementing long-life drivers, with remarks on both their benefits and drawbacks. An extensive literature review on the topic is carried out, and some practical outcomes from recent research on offline LED driving are highlighted.

Matching LED and Driver Life Spans: A Review of Different Techniques

A technological breakthrough is embodied in the successful demonstration of an extended interaction klystron (EIK) amplifier, which has produced over 7.5 kW of peak output power at W-band (94 GHz). An efficiency of ${\sim}{17\%}$ has been achieved with a depressed collector. The EIK is driven by a 20-kV, 4-A sheet beam in a permanent magnet solenoid, with 99% beam current transmission from gun to collector. Key features that contribute to the success of this device are: 1) tight beam focusing and correspondingly narrow beam tunnel, which are made possible by the solenoidal focusing and which provide high interaction impedance and high gain per unit length and 2) the incorporation of design elements to stabilize the inherently over-moded circuit. Measured performance agrees well with 3-D particle-in-cell simulations.

Demonstration of a Multikilowatt, Solenoidally Focused Sheet Beam Amplifier at 94 GHz

The millimeter-wave spectrum, generally considered to range from 30 to 300 GHz, is one of the most actively used spectrums today, with applications such as high-data-rate terrestrial and space communications, radar, and electronic warfare. The helix traveling-wave tube (TWT) amplifier has long been a critical component for enabling modern millimeter-wave systems. This paper presents an overview of several recently developed high-power millimeter-wave helix TWTs which have extended the helix TWT performance envelope. In particular, the power-frequency-bandwidth product for these devices has increased by a factor of 4 to over 100 depending upon the application. These helix TWTs operate at power levels up to 1-kW peak power or 500-W average or continuous-wave power and over frequencies from 18 to 46 GHz, with efficiencies up to 60%. The helix TWT performance improvements discussed here have not only kept pace with improvements in rival technologies such as GaN solid-state power amplifiers but also pushed helix TWTs into competition with traditionally higher power and higher frequency vacuum electron devices such as extended-interaction klystrons and coupled-cavity TWTs. Indeed, the modern high-power millimeter-wave helix TWT offers system engineers a singularly attractive amplifier technology with an outstanding combination of small size, light weight, high efficiency, good linearity, high reliability, and large bandwidth.

Latest Advancements in High-Power Millimeter-Wave Helix TWTs

Traveling wave tubes are rapidly evolving to provide unprecedented power level in comparison to solid state devices in the millimeter waves region of the spectrum (80–300 GHz) thus enabling a wide ...

https://www.tandfonline.com/doi/pdf/10.1080/09205071.2020.1848643

Millimeter wave traveling wave tubes for the 21st Century

This paper presents the first experimental results of an extended interaction oscillator (EIO) based on a pseudospark-sourced electron beam, which produced a peak output power over 38 W at $W$ -band. The advantages of the newly developed device are: 1) transport of the electron beam by the positive-ion focusing channel without the need of an external magnetic field and 2) high interaction impedance and high gain per unit length of the EIO circuit. The experimental results agree well with the 3-D particle-in-cell simulations.

/pdf/simulation-and-experiments-of-a-w-band-extended-interaction-4dihlj66je.pdf

Simulation and Experiments of a $W$ -Band Extended Interaction Oscillator Based on a Pseudospark-Sourced Electron Beam

The design and development of a high-perveance sheet electron beam is reported. A beamstick that employs a novel sheet beam gun together with a permanent magnet solenoid has been fabricated and tested up to 4.8 A at 22 kV. At the nominal operating point of 19.5 kV and 3.3 A, this beamstick has transported 98.5% of the emitted electron current through a 0.4 × 5 mm beam tunnel over a distance of 20 mm in a uniform 8.5-kG field. The beamstick collector has been depressed to -9 kV with very little effect on the beam transport. The performance very well agrees with simulations. This beamstick will be the basis for a high-power (~10-kW) W-band extended-interaction-klystron amplifier that is currently under development.

Demonstration of a 100-kW Solenoidally Focused Sheet Electron Beam for Millimeter-Wave Amplifiers

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 Sheet Beam Klystron (SBK) is characterized by a large drift tube, which allows the use of high beam current at a low voltage, resulting in low beam current density, high efficiency and the possibility of PPM focusing. CPI has designed, manufactured and is currently testing an X-Band SBK capable of 5 MW peak, 20 kW average output power This paper discusses the general design, manufacturing and performance to date of CPI's X-Band SBK.

Adam Balkcum

Papers

Demonstration of a Multikilowatt, Solenoidally Focused Sheet Beam Amplifier at 94 GHz

Demonstration of a 100-kW Solenoidally Focused Sheet Electron Beam for Millimeter-Wave Amplifiers

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

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

X-Band Sheet Beam Klystron (XSBK)