High Power Millimeter Wave Research Articles

Transcriptional landscape of human keratinocyte models exposed to 60-GHz millimeter-waves

The use of millimeter waves (MMW) will exponentially grow in the coming years due to their future utilization in 5G/6G networks. The question of possible biological effects at these frequencies has been raised. In this present study, we aimed to investigate gene expression changes under exposure to MMW using the Bulk RNA Barcoding and sequencing (BRB-seq) technology. To address this issue, three exposure scenarios were performed aiming at: i) comparing the cellular response of two primary culture of keratinocytes (HEK and NHEK) and one keratinocyte derivate cell line (HaCaT) exposed to MMW; ii) exploring the incident power density dose-effect on gene expression in HaCaT cell line; and, iii) studying the exposure duration at the new ICNIRP exposure limit for the general population. With the exception of heat effect induced by high power MMW (over 10 mW/cm2), those exposure scenarios have not enabled us to demonstrate important gene expression changes in the different cell populations studied. Very few differentially genes were observed between MMW exposed samples and heat shock control, and most of them were significantly associated with heat shock response that may reflect small differences in the heat generation. Together these results show that acute exposure to MMW has no effects on the transcriptional landscape of human keratinocyte models under athermal conditions.

Design of Stray Radiation Sensor for ITER ECE Diagnostic

The Electron Cyclotron Emission (ECE) diagnostic has a primary role in the measurement of electron temperature profile and electron temperature fluctuations in ITER. This diagnostic shall be exposed to significant power due to unabsorbed Electron Cyclotron Heating (ECH) power in the plasma. The expected stray power loads could be a few tens of watts, and therefore, the protection of millimetre wave components is one of the design challenges of ITER ECE diagnostic. This protection system includes sensors, a band stop notch filter, and a shutter to stop the RF stray radiation from being incident on the sensitive components. The sensors will be positioned along the ECE transmission line, and shall be used for real-time power monitoring of the stray radiation. Here, we describe a novel design of a sensor for monitoring the stray radiation power. This sensor is a Schottky Diode rectenna, known for high-power and high-speed millimetre wave detection capability. It consists of a 2x2 microstrip patch antenna array, a matching circuit, a diode, and a low pass filter. The antenna array is designed analytically and optimized in CST Microwave Studio, for wide reception angle, high gain, and low side lobe levels. Furthermore, the rectifying circuit is optimized using Agilent Advanced Design System (ADS) software to get better rectification and impedance matching of the signal, thereby improving its detection sensitivity. The ADS simulation results show that the detection sensitivity is about 1000V/W for input power of -30 dBm at 170 GHz, thereby achieving the required performance of the sensor.

Comparative Study of III-Nitride Nano-HEMTs on Different Substrates for Emerging High-Power Nanoelectronics and Millimetre Wave Applications

Comparative Study of III-Nitride Nano-HEMTs on Different Substrates for Emerging High-Power Nanoelectronics and Millimetre Wave Applications

Wireless Soft Actuator Based on Liquid-Gas Phase Transition Controlled by Millimeter-Wave Irradiation

We propose a wireless soft actuator controlled thermally by millimeter-wave irradiation. The actuator is composed of low boiling point liquid sealed in a soft bellows. By irradiating high-power millimeter-waves, the liquid can be evaporated to generate a strong mechanical force. We characterize the force and work extracted from the bellows as a function of the liquid volume and temperature. We then demonstrate the wireless actuation by irradiating a millimeter-wave on the bellows. We also evaluate its dynamic response by modulating the millimeter-wave. Our approach provides novel usage and design space of soft actuators.

Synthesis of Broadband Oversized Smooth-Walled Horn for High-Power Millimeter Wave

This article proposes a synthesis method based on phase modulation to design broadband oversized smooth-walled horns for high-power millimeter-wave applications. The bandwidth of oversized smooth-walled horn is confined by the mismatch of the relative phase between TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode. By analyzing the mode conversion along horn, it is found that the phase of the generated TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode can be influenced by the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode. Therefore, the synthesis method uses a slow waveguide taper, in which the generated TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode is in a small fraction and its phase is efficiently influenced by TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode, to modulate the relative phase of TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode. Using the proposed method, an oversized smooth-walled horn is designed, of which the phase mismatch is ±10° in the range of 32–38 GHz. The simulation results show that the proposed horn has a highly symmetric far-field pattern with a peak gain greater than 28 dBi in the range of 32–38 GHz and the sidelobe level has −19 dB decline compared with the peak gain. A prototype is fabricated and the near-field pattern measurement is carried out. The high correspondence of the simulated near-field patterns with the measured ones proves that the proposed method is an appropriate option to design broadband feed horns for high-power millimeter wave.

Design and simulation investigations of high-power millimeter-wave gyrotron

ABSTRACTIn this paper, a high power millimeter wave gyrotron cavity was modelled and studied for its beam-wave interaction, beam-misalignment, and thermal issues. The sub-assemblies including the magnetron injection gun (MIG), RF output window, and electron beam collector were investigated. The MIG has produced an annular electron beam with transverse velocity spread less than ∼4%. The Particle–In–Cell simulation predicted an RF output of 470 kW in TE10,4 mode at ∼139.52 GHz for a DC drive of 80 kV, 20 A. The temperature on the inner, outer surfaces of the cavity and the corresponding average radial expansion of the cavity were calculated. Due to the radial expansion of the cavity, the resonant frequency and RF output power has changed to ∼0.514 GHz and ∼50 kW, respectively. Finally, the overall efficiency of the present gyrotron was improved from ∼29% to ∼47% by using a single–stage depressed collector.

High-Power Millimeter-Wave Multiplexer for Beam Station of Microwave Rocket

High-Power Millimeter-Wave Multiplexer for Beam Station of Microwave Rocket

Analysis and Simulation of a Gigawatt-ClassKa-Band Radial Transit Time Oscillator

Obtaining high power millimeter-wave output is a research hotspot of high power microwave (HPM) technology. Considering limited power capacity and mode competition in axial millimeter wave generators, the radial device is introduced to output high power millimeter waves. A gigawatt-class ${Ka}$ -band radial transit time oscillator (RTTO) is proposed in this paper. In guiding the magnetic field of 0.8 T, the radial TM01 mode is applied as the operation mode. Particle-in-cell (PIC) simulation demonstrates that when the diode voltage is 400 kV and the beam current is 7.5 kA, the HPMs at 31.2 GHz with an output power of 1.1 GW and a conversion efficiency of about 37% are generated. The maximum radial electric field is 1.2 MV/cm, proving that the radial structure is an effective way to enhance power capacity. 3-D PIC simulation proves there is no angular nonasymmetric mode intersection. Analysis of parameter sensitivity shows that, within a certain range, the thickness and axial position offset of the electron beam will not influence the performance of the RTTO. In addition, the oscillator can operate steadily as the radial guiding magnetic field changes from 0.6 to 6.0 T. With these characteristics, the RTTO is potential to output ${Ka}$ -band HPMs.

Wireless Power Transfer via Subterahertz-Wave

Research on wireless power transmission by a rectenna using millimeter waves and subterahertz waves is gaining attention. It is expected that energy harvesters at high frequencies will be developed for use with future 5 G. High-power wireless power supply to various applications will be possible because of miniaturization of the rectenna. As described herein, we investigate earlier studies of millimeter-wave wireless power supply, selecting and explaining salient examples of millimeter-wave high power wireless power supply.

Balancing Thermal and Electrical Packaging Requirements for GaN Microwave and Millimeter-Wave High Power Amplifier Modules

A method for balancing thermal and electrical packaging requirements for gallium nitride (GaN) high power amplifier (HPA) modules is presented. The goal is to find a design approach that minimizes the junction temperature of the GaN so that it is reliable and has interconnects that meet electrical performance requirements. One benefit of GaN is that it can simultaneously achieve high power density and operate at microwave and millimeter-wave frequencies. However, the power density can be so high that the necessary thermal solutions can have negative impact on electrical performance. This is especially a concern for the electrical interconnects required for the input/ output ports on high power amplifier devices. This is because the signal interconnects must operate at GHz frequencies, which means that special care must be taken to avoid problems such as undesired signal coupling and ground path inductance. Therefore, this work focuses on GaN packaging and its integration into a module. The results show that an optimum thickness for the GaN heat spreader exits for thermal performance but the electrical design is impacted negatively if the optimum thermal design is chosen. Therefore, a balanced design is chosen which meets overall system level requirements.

Andrew Marienhoff Sessler

Andrew Marienhoff Sessler

Millimeter-Wave GaN HEMT for Power Amplifier Applications

SUMMARY Gallium nitride high electron mobility transistors (GaN HEMTs) were developed for millimeter-wave high power amplifier applications. The device with a gate length of 80 nm and an InAlN barrier layer exhibited high drain current of more than 1.2 A/ mm and high breakdown voltage of 73V. A cut-off frequency fT of 113GHz and maximum oscillation frequency fmax of 230GHz were achieved. The output power density reached 1 W/ mm with a linear gain of 6.4dB at load-pull measurements at 90GHz. And we extracted equivalent circuit model parameters of the millimeter-wave InAlN/ GaN HEMT and showed that the model was useful in simulating the millimeter-wave power performance. Also, we report a preliminary constant bias stress test result.

Experimental characterization of anomalous strong scattering of mm-waves in TEXTOR plasmas with rotating islands

Anomalous scattering of high power millimetre waves from gyrotrons at 140 and 110 GHz is investigated for plasma with rotating islands at TEXTOR. The magnetic field and plasma density influence the spectral content of the scattered waves and their power levels significantly. Anomalous strong scattering occurs in two density regimes, one at low densities and one at high densities, that also depend on the magnetic field. The two regimes are separated by a quiescent regime without anomalous scattering. Investigations suggest that scattering in the high-density regime is generated at the low-field side intersection of the gyrotron beam and the island position. The transition from the quiescent regime to the high-density regime occurs when the gyrotron frequency is twice the upper hybrid frequency at this position. There is some evidence that the scattering in the low-density regime is generated near the plasma centre. Under this assumption all the observed scattering is generated when the gyrotron frequency is near or below twice the upper hybrid frequency.

Development of Millimeter-wave High Power GaN Amplifier Technology

Development of Millimeter-wave High Power GaN Amplifier Technology

基于多边带拍频实现高功率毫米波方法

基于多边带拍频实现高功率毫米波方法

Risk mitigation strategy for the ITER electron cyclotron upper port launcher

A basic requirement for ITER equipment to meet is a high level of reliability, because ITER operation time is precious and radioactive operation leaves limited scope for repair. In order to reduce the risk of failure during ITER operation an effective risk mitigation strategy is necessary. This paper presents such strategy for the ITER electron cyclotron upper port launcher (ECUPL). A preliminary ECUPL risk analysis identifies possible failure modes. A probabilistic risk assessment quantifies the risk of failure using a 4 × 4 impact-likelihood matrix. Impact is quantified through technical, cost and schedule elements. Likelihood depends on the risk mitigation strategy adopted. A cost benefit analysis determines the most cost effective risk mitigation strategy. An essential element in risk mitigation is the testing of equipment prior to installation on the ITER machine. This paper argues the need for low- and highpower millimetre wave tests carried out on the fully assembled ECUPL. It presents a conceptual design for a dedicated on-site test bed that can handle 2 of 8 microwave beams at 2 MW long pulse operation.

A remotely steered millimetre wave launcher for electron cyclotron heating and current drive on ITER

High-power millimetre wave beams employed on ITER for heating and current drive at the 170 GHz electron cyclotron resonance frequency require agile steering and tight focusing of the beams to suppress neoclassical tearing modes. This paper presents experimental validation of the remote steering (RS) concept of the ITER upper port millimetre wave beam launcher. Remote steering at the entrance of the upper port launcher rather than at the plasma side offers advantages in reliability and maintenance of the mechanically vulnerable steering system. A one-to-one scale mock-up consisting of a transmission line, mitre bends, remote steering unit, vacuum window, square corrugated waveguide and front mirror simulates the ITER launcher design configuration. Validation is based on low-power heterodyne measurements of the complex amplitude and phase distribution of the steered Gaussian beam. High-power (400 kW) short pulse (10 ms) operation under vacuum, diagnosed by calorimetry and thermography of the near- and far-field beam patterns, confirms high-power operation, but shows increased power loss attributed to deteriorating input beam quality compared with low-power operation. Polarization measurements show little variation with steering, which is important for effective current drive requiring elliptical polarization for O-mode excitation. Results show that a RS range of up to −12° to +12° can be achieved with acceptable beam quality. These measurements confirm the back-up design of the ITER ECRH&CD launcher with future application for DEMO.

Effect of self-focusing on millimetre wave communication with re-entry space vehicles

A high power millimetre wave, employed for communication with a re-entry space vehicle surrounded by a high-density plasma sheath, is affected by linear and nonlinear effects. A signal originating from the ground suffers diffraction divergence through space, prior to entering the fast evolving plasma sheath surrounding the vehicle, and undergoes time dependent absorption inside the sheath. The net signal loss due to diffraction and absorption varies as the spacecraft approaches the ground. The wave launched from the spacecraft for downward communication has a large amplitude in the plasma sheath and gives rise to nonlinear effects. The millimetre wave heats the electrons more strongly in the region where the wave intensity is maximum, causing ambipolar diffusion of the plasma leading to an increase in the refractive index at the axis, thus self-focusing the millimetre wave signal. In free space, after passing through the plasma sheath, the beam suffers defocusing.

A fast switch, combiner and narrow-band filter for high-power millimetre wave beams

A fast directional switch (FADIS) is described, which allows controlled switching of high-power microwaves between two outputs. A possible application could be synchronous stabilization of neoclassical tearing modes (NTMs). Generally, the device can be used to share the installed EC power between different types of launchers or different applications (e.g. in ITER, midplane/upper launcher). The switching is performed electronically without moving parts by a small frequency-shift keying of the gyrotron (some tens of megahertz), and a narrow-band diplexer. The device can be operated as a beam combiner also, which offers attractive transmission perspectives in multi-megawatt ECRH systems. In addition, these diplexers are useful for plasma diagnostic systems employing high-power sources due to their filter characteristics.The principle and the design of a four-port quasi-optical resonator diplexer is presented. Low-power measurements of switching contrast, mode purity and efficiency show good agreement with theory. Preliminary frequency modulation characteristics of gyrotrons are shown, and first results from high-power switching experiments using the ECRH system for W7-X are presented.

Experimental Investigation of Resistive Sensor for High Power Millimetre Wave Pulse Measurement

An experimental investigation of a high power millimetre wave pulse sensor is presented. Two groups of sensors with a ∞at frequency response were fabricated according to results of the optimisation. The frequency response and voltage standing wave ratio were measured and compared with results of the electrodynamical simulations. The largest measured sensitivity variation of the best sensors within waveguide frequency range was §8%. The reasonable agreement between measured and simulated values of the sensitivity was obtained.