This article reviews the state-of-the-art millimeter-wave (mm-wave) power amplifiers (PAs), focusing on broadband design techniques. An overview of the main solid-state technologies is provided, including Si, gallium arsenide (GaAs), GaN, and other III–V materials, and both field-effect and bipolar transistors. The most popular broadband design techniques are introduced, before critically comparing through the most relevant design examples found in the scientific literature. Given the wide breadth of applications that are foreseen to exploit the mm-wave spectrum, this contribution will represent a valuable guide for designers who need a single reference before adventuring in the challenging task of the mm-wave PA design.

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A Review of Technologies and Design Techniques of Millimeter-Wave Power Amplifiers

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

A millimeter (mm) wave amplifier that combines both high-power output and a wide bandwidth would enable dramatic improvements in areas where high-power radio signals with significant information content are required. However, to date, the only available devices are either high-power vacuum electronic devices with limited bandwidths, or larger bandwidth semiconductor amplifiers with low-power output. Here, we show a new design of a vacuum electronic traveling-wave tube amplifier that has a measured output power of 107 W with a 3-dB bandwidth of 6 GHz centered on 200 GHz. The power-bandwidth product of this amplifier is 642 W-GHz. These results provide a demonstration of a high-power mm-wave source with significant bandwidth. This device is readily scalable to other frequency bands, particularly those in the mm- and sub-mm-wave frequency bands from 100 GHz to 1 THz.

Development of a 100-W 200-GHz High Bandwidth mm-Wave Amplifier

The development of a G-band traveling wave tube for wireless communications and airborne radars is described. The maximum output power of this device is over 20 W. This device provides a saturation output power over 15 W and a saturation gain over 32 dB with a bandwidth of 7.6 GHz. A folded waveguide circuit with modified circular bends is utilized to eliminate the band-edge instability caused by the high beam voltage of 20 kV. A pencil beam of 50 mA with a transmission ratio over 95 % is realized, making the device capable of operating in continuous wave mode. Periodic permanent magnets are employed for compactness. Chemical vapor deposition diamond disc is used in the input and output RF windows to minimize the loss and voltage standing wave ratios of the traveling wave tube. The weight and the size of the device are 2 kg and 300 mm $\times70$ mm $\times70$ mm, respectively. The efficiency of the device is over 5 %.

A G-Band Traveling Wave Tube With 20 W Continuous Wave Output Power

This letter presents the research progress of a pulsed G-band 50 W traveling wave tube (TWT) with pencil beam focused by periodic permanent magnet (PPM). Three approaches have been combined to improve the tube’s operation performances including setting the operating point near the cutoff frequency, using the folded waveguide (FWG) slow wave structure (SWS) with modified circular bends (MCBs), and adopting phase velocity tapering (PVT) technique. The measured output power can be over 50 W at 5% duty cycle with a bandwidth of 3.6 GHz when the beam voltage is 24.25 kV and the beam current is 59 mA. Corresponding electronic efficiency and gain are higher than 3.5% and 35 dB, respectively. The results provide a demonstration of a compact terahertz amplifier with high power, high electronic efficiency and significant bandwidth.

Demonstration of a Pulsed G-Band 50-W Traveling Wave Tube

The development of a compact radio frequency (RF) vacuum power amplifier for high-resolution airborne radar is described. The amplifier, a microwave power module (MPM), operates in the upper millimeter-wave frequency band of 231.5–235 GHz providing a peak output power of 32 W. Common with previous extremely high frequency MPM development at Electron Devices, the ${G}$ -band MPM consists of a periodic permanent magnet focused serpentine waveguide traveling wave tube (TWT) and a miniaturized 20-kV electronic power conditioner. Input drive to the MPM for saturation is around 10 mW. Low-loss chemical vapor deposition diamond WR-4.3 windows serve as the input and output ports of the TWT. Due to the high duty of the radar application, a four-stage TWT collector is employed for beam energy recovery. The MPM operates from a 270- $\text{V}_{\sf {dc}}$ power source. Two MPM configurations have been constructed: a single integrated unit for laboratory testing and a split-package configuration for integration in a standard electro-optical/infrared gimbal. The split-package flight test unit has a maximum prime power requirement of 176 W, corresponding to an overall amplifier efficiency of 9%. The radar sensor has been flown on a modified DC-3 test bed with high-resolution real-time video imagery obtained under cloud-obscured operating conditions.

A Compact Extremely High Frequency MPM Power Amplifier

A compact, upper-mm-wave, microwave power module (MPM) power amplifier operating in G-band from 231.5 GHz to 235 GHz has been developed at L3 Electron Devices. Two MPM configurations have been tested: The first, intended for laboratory use, consists of a single-housing containing a PPM-focused serpentine waveguide traveling wave tube and a compact 20 kV high voltage power supply. This MPM provides a peak output power of 41 dBm at 234 GHz when driven with 7 dBm input. The second MPM is configured for use in a modified tactical airborne gimbal. It employs a custom split-package architecture consisting of separate power supply and RF modules, along with interconnecting cabling. This unit has been qualified for airborne operation up to 20 kft (6 km) and provides greater than 44 dBm at 234 GHz when driven with 11 dBm input drive. Both MPMs operate from 270 VDC prime power and at duty factors up to 50%. Radar waveforms have been processed through both amplifiers. We believe this development represents the first realization of an integrated G-band MPM.

Kevin Berg

Papers

A Compact Extremely High Frequency MPM Power Amplifier

A compact G-band MPM power amplifier for high-resolution airborne radar