Microwave Power Module Research Articles

Методы диагностики локальных напряжений/деформаций в алмазе при комнатной температуре на основе оптического детектирования магнитного резонанса NV-дефектов

A method for diagnostics of local stresses/strains in diamond at room temperature based on optically detected magnetic resonance (ODMR) of NV defects in a zero magnetic field using low-frequency microwave power modulation is proposed.

Diagnostics methods of local stresses/strains in diamond at room temperature based on optically detected magnetic resonance of NV defects

A method for diagnostics of local stresses/strains in diamond at room temperature based on optically detected magnetic resonance (ODMR) of NV defects in a zero magnetic field using low-frequency microwave power modulation is proposed. Keywords: NV defect, diamond, optically detected magnetic resonance (ODMR).

Demonstration of a Broadband W-Band Microwave Power Module With Improved Gain Flatness

A broadband W-band microwave power module (MPM) is demonstrated. It provides a continuous wave (CW) output power of 65 W from 91 to 97 GHz with a constant driving power of 0 dBm. The MPM consists of a miniaturized folded-waveguide traveling-wave tube (TWT), an integrated power conditioner (IPC), and a gain equalizing solid-state amplifier (GE-SSA). The overall efficiency exceeds 20 % and the saturation gain fluctuation is lower than 0.8 dB. It has dimensions of 380 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 180 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 45 mm and a weight of 5.5 kg.

Impact of the power density on the physical properties, starch structure, and acceptability of oil-free potato chips dehydrated by microwave vacuum drying

Oil-free potato chips with a preserved semicrystalline starch structure are an excellent carbohydrate source since they are related to a low-glycemic index. Microwave vacuum drying is an alternative to produce crispy products under mild temperatures, showing potential to reduce starch gelatinization, preserving its structure. However, the drying parameters require investigation once microwave power density can influence drying kinetics and product's physical properties, including starch structure. Thus, this study aimed to evaluate the impact of power density on the properties above and the product's sensory acceptance. Fresh potatoes were sliced and dried using three initial nominal power densities (6, 4, and 3 W/g) in a microwave vacuum oven with a rotatory system to guarantee uniform heating. The process temperature was controlled by microwave power modulation to avoid high temperatures that cause starch gelatinization. All the investigated conditions preserved the starch crystallinity, but the preservation was higher in the lower power density. However, the highest power density process produced dried samples in a shorter time with a more expanded and porous structure and crispier texture, leading to higher product acceptance. The resulting potato chips can address health and sensory concerns, essential to the world market that demands healthy and tasty foods.

Microwave vacuum drying of foods with temperature control by power modulation

Microwave power modulation during drying was evaluated to guarantee mild temperatures, reducing burning spots when producing sweet potatoes snacks. Samples were peeled, sliced, blanched, and microwave vacuum dried with (MWVDc) and without (MWVD) controlling the temperature (60 °C) with a PID system. MWVD used constant power, while MWVDc adjusted the power input based on samples' temperature target. Moisture content was reduced from 4.5 g g−1 (db) to 0.4 g g−1 (db), resulting in water activity lower than 0.55. MWVD processing time was about 80, 15, and 10 min at 300, 1500, and 2700 W, respectively, resulting in dried samples with dark areas due to hot spots. The power modulation in MWVDc resulted in intermediary drying time (50 min) and uniform color products without burnings. This study demonstrated that automated temperature control leads to high-quality sweet potato chips by microwave processing.

Overview of development of microwave power amplifiers

Microwave power amplifiers are divided into vacuum and solid devices. This paper analyzes the principles, advantages and disadvantages of these two types of devices, and then introduces their development history, current technical research status and future development trends. This paper mainly introduces the microwave power module as it is the combination of these two devices, including its evolution process and current development status both home and abroad, and analyzes and predictes its future development.

Optimal Design of an X-Band, Fully-Coaxial, Easily-Tunable Broadband Power Equalizer for a Microwave Power Module

A microwave power module (MPM), which is a hybrid combination of a solid-state power amplifier (SSPA) as a driver and a traveling-wave tube amplifier (TWT) as the final high power stage, is a high-power device largely used for radar applications. A gain equalizer is often required to flatten the TWT output power gain owing to its big gain fluctuations over the operating frequency range. In this paper, the design of an X-band, fully-coaxial, easily-tunable broadband power equalizer for an MPM is presented. The structure is composed of a coaxial waveguide as the main transmission line and a coaxial cavity loaded with absorbing material as a resonant unit. Sensitivity analyses of the attenuation amplitude and resonant frequency of the equalizer in terms of coaxial cavity length, thickness of the absorbing disc, and insertion depth of the probe were carried out. The measured results were in good agreement with the simulated ones, showing that the equalization curve met the requirements well and proved that this optimal structure has the advantages of a large power capacity, a wide operating frequency band, is easily tunable, and good transmission performance.

On Stabilizing of the Beam Energy in the Standing-Waves Accelerating Structure

Energy of the particles in the standing-waves accelerating structure is stabilized due to the delay of the beam injection and the amplitude modulation of the input microwave power in the structure with the envelope in the form of a sequence of two rectangular pulses of adjustable amplitude without any delay between them and the injection of the beam during the second microwave pulse.

A Compact Extremely High Frequency MPM Power Amplifier

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 50-W Broadband Mini-MPM for Electronic Countermeasure

In this paper, a new miniaturized microwave power modules (MPM) CKu501 for electronic countermeasure is proposed. With the overall dimension at 134 mm × 67 mm × 20 mm, it is significantly smaller than current existing MPMs, and offers a marked improvement in power density. The output power of this mini-MPM reaches 50 W across the operating frequency band of 6-18 GHz, with the overall efficiency greater than 32%. It can be reliably applied in the airborne conditions.

Plasma-assisted CO2 conversion: optimizing performance via microwave power modulation

Significant improvement in the energy efficiency of plasma-assisted CO2 conversion is achieved with applied power modulation in a surfaguide microwave discharge. The obtained values of CO2 conversion and energy efficiency are, respectively, 0.23 and 0.33 for a 0.95 CO2 + 0.05 N2 gas mixture. Analysis of the energy relaxation mechanisms shows that power modulation can potentially affect the vibrational–translational energy exchange in plasma. In our case, however, this mechanism does not play a major role, likely due to the low degree of plasma non-equilibrium in the considered pressure range. Instead, the gas residence time in the discharge active zone together with plasma pulse duration are found to be the main factors affecting the CO2 conversion efficiency at low plasma pulse repetition rates. This effect is confirmed experimentally by the in situ time-resolved two-photon absorption laser-induced fluorescence measurements of CO molecular density produced in the discharge as a result of CO2 decomposition.

Taurine-EVA copolymer-paraffin rods dosimeters for EPR high-dose radiation dosimetry

Abstract Taurine/EPR rods (3 × 10 mm) have been prepared by a simple technique in the laboratory where taurine powder was mixed with a molten mixture of paraffin wax and an ethylene vinyl acetate (EVA) copolymer. The binding mixture EVA/Paraffin does not present interference or noise in the EPR signal before or after irradiation. The rods show good mechanical properties for safe and multi-use handling. An EPR investigation of radiation induced radicals in taurine rods revealed that there are two types of radicals produced after exposure to gamma radiation (60Co). EPR spectra were recorded and analyzed - also the microwave power saturation and modulation amplitude were studied and optimized. Response of taurine to different radiation doses (1.5-100 kGy) was studied and found to follow a linear relationship up to 100 kGy. Radiation induced radicals in taurine persists and showed a noticeable stability over 94 days following irradiation. Uncertainities associated with the evaluation of radiation doses using taurine dosimeters were discussed and tabulated. It was found that taurine possesses good dosimetric properties using EPR spectroscopy in high doses in addition to its simple spectrum.

Integrated Design of a Compact and Lightweight S-Band Traveling-Wave Tube Amplifier for a New Class of Microwave Power Module

A new class of compact and lightweight S-band 1 kW traveling-wave tube (TWT) is being developed for a microwave power module (MPM) that will be used for phased antenna array radar applications. The proposed S-band MPM provides a tenfold peak power increase compared to state-of-the-art S-band MPMs. In this paper, the design of the vacuum power booster TWT part of the MPM is presented. The compact and lightweight S-band TWT is driven by a 6 kV, 0.9 A electron beam. The amplifier is predicted by large-signal simulations to generate over 1 kW at S-band with 25 dB saturated gain and over 40% efficiency. The stability from unwanted oscillations has been investigated. To suppress the oscillations, the helix circuit has been coated with carbon composite material. The coaxial input and output antennas have been fabricated. For efficiency enhancement, a multi-stage depressed collector (MDC) has been designed using a 3D particle-in-cell (PIC) simulator, VORPAL. The collector design makes use of a current loop based on a feedback mechanism for effective design process. The integrated designs of a helix circuit, an electron gun, a periodic permanent magnet (PPM), antennas, and a collector are presented.

Multiparametric gyrotron power control during microwave processing of materials

Optimization of the control of gyrotron generation regime through consistent variation of the cathode voltage and solenoid magnetic field makes possible a significant (up to threefold) decrease in power consumption during microwave processing of materials. It is experimentally established that, for this purpose, it is possible to use fast (with a characteristic time on the order of a fraction of millisecond) modulation of microwave power through variation of the working magnetic field by the current of an auxiliary coil arranged near the cavity.

The Principle Analysis and Research of Power System Converter of Microwave Power Module

According to the demands of power supply system of microwave power module (MPM), ZVS push-pull dual-voltage resonant converter is present. High-voltage can be achieved in this new novel converter topology. The paper introduces the structure of the converter. Then the steady-state and operation characteristic of the converter is analyzed and deduced. A Pspice simulation is carried out to verify the theoretical analysis, the results and conclusions are given in the end. The results show that the ZVS push-pull dual-voltage resonant converter can realize the soft-switch and double voltage well. The structure of the converter is simple and easy to implementation, so it suitable for low input voltage and high output voltage power supply system.

A staggered double vane circuit for a W-band traveling-wave tube amplifier

Based on the combination of a staggered double vane slow wave structure (SWS) and round electron beam, a 200-W W-band traveling-wave tube (TWT) amplifier is studied in this paper. The main advantages of round beam operation over the sheet beam is that the round beam can be formed more easily and the focus requirement can be dramatically reduced. It operates in the fundamental mode at the first spatial harmonic. The geometric parameters are optimized and a transition structure for the slow wave circuit is designed which can well match the signal that enters into and goes out from the tube. Then a TWT model is established and the particle-in-cell (PIC) simulation results show that the tube can provide over 200-W output power in a frequency range of 88 GHz-103 GHz with a maximum power of 289 W at 95 GHz, on the assumption that the input power is 0.1 W and the beam power is 5.155 kW. The corresponding conversion efficiency and gain at 95 GHz are expected to be 5.6% and 34.6 dB, respectively. Such amplifiers can potentially be used in high power microwave-power-modules (MPM) and for other portable applications.

Design and modeling of multistage depressed collectors by using 3D conformal finite-difference time-domain particle-in-cell simulations

The feasibility of designing and modeling a multistage depressed collector (MDC) by using 3D conformal finite-difference time-domain (CFDTD) particle-in-cell (PIC) simulations as implemented in 3D PIC code, VORPAL has been studied. A simple circuit model employing feedback mechanisms has been implemented to provide stable time-dependent voltages for each stage of the depressed collector, and an arbitrary space-time dependent spent-beam distribution is given in our timedomain simulations. We demonstrate the design of a five-stage depressed collector recovering a triangular-like spent-beam distribution imported from a large signal simulation, achieving an energy recovery efficiency of 75%. The MDC after optimization can be integrated into the limited space of an S-band traveling wave tube for a compact microwave power module (MPM).

W-band PELDOR with 1 kW microwave power: Molecular geometry, flexibility and exchange coupling

A technique that is increasingly being used to determine the structure and conformational flexibility of biomacromolecules is Pulsed Electron–Electron Double Resonance (PELDOR or DEER), an Electron Paramagnetic Resonance (EPR) based technique. At X-band frequencies (9.5GHz), PELDOR is capable of precisely measuring distances in the range of 1.5–8nm between paramagnetic centres but the orientation selectivity is weak. In contrast, working at higher frequencies increases the orientation selection but usually at the expense of decreased microwave power and PELDOR modulation depth. Here it is shown that a home-built high-power pulsed W-band EPR spectrometer (HiPER) with a large instantaneous bandwidth enables one to achieve PELDOR data with a high degree of orientation selectivity and large modulation depths. We demonstrate a measurement methodology that gives a set of PELDOR time traces that yield highly constrained data sets. Simulating the resulting time traces provides a deeper insight into the conformational flexibility and exchange coupling of three bisnitroxide model systems. These measurements provide strong evidence that W-band PELDOR may prove to be an accurate and quantitative tool in assessing the relative orientations of nitroxide spin labels and to correlate those orientations to the underlying biological structure and dynamics.

SIMULATION MODELING ON DISPERSION SHAPING AND HARMONIC SUPPRESSION IN HELIX TWT FROM 2 GHz TO 6 GHz

This paper describes the investigation of broadband interaction and harmonic suppression. A special dispersion shape used in broadband traveling-wave tubes (TWT) is obtained. The theoretical and simulation studies of negative dispersion are presented. On the basis of these studies, a broadband TWT used in microwave power module (MPM) is designed. Compared with the old TWT with flat dispersion, the new one with negative dispersion decreases the second harmonic content about 10 dB and improves the fundamental efficiency with a maximum increase of about 5% at the lowest frequency 2 GHz. The new one operates with the beam voltage of 3600 V and current of 250mA. The modified TWT is fabricated and the simulation results meet the measurements very well.

Inactivation of S. mutans Using an Atmospheric Plasma Driven by a Palm-Size-Integrated Microwave Power Module

A low-power palm-size microwave power module for portable microwave-excited plasma applicable to biomedicine is integrated on a single printed circuit board for the first time. The designed board includes a power amplifier chip, a phase-locked loop (PLL) chip, and an impedance matching network with microstrip lines. In addition, as a part of the true one-chip integration of the plasma power module, the PLL is designed and fabricated in a semiconductor chip with a 0.18-μm CMOS technology for dedicated use to our plasma source. For the plasma generator, a 900-MHz coaxial transmission line resonator is used with argon gas flow. The designed plasma source is applied to the inactivation of S. mutans, showing three-log reduction within 180-s treatment. Measurements for the different initial concentrations (from 105 to 10 9 CFU/mL) are also conducted, and the outcomes are discussed. The results verify the feasibility of the proposed integrated microplasma source for use in dental treatments.