Power Handling Capacity Research Articles

Application of metamaterials for performance enhancement of planar antennas: A review

Metamaterials are assemblies of metallic and/or dielectric materials with properties that are not readily found in naturally existing materials. Hence, metamaterial structures are commonly loaded on/near the patch, embedded in the substrate, loaded/etched from the ground plane or placed as a superstrate layer for enhancing bandwidth and gain, and size miniaturization of conventional patch antennas. The demand for wide bandwidth, high gain, and compact antennas is highly contemplated in recent wireless communication research studies. Despite their lightweight, ease of fabrication, low profile, and simplicity for integration, patch antennas have performance limitations as result of their narrow bandwidth, lower gain, larger size, and lower power handling capacity. To address these problems, metamaterial-based antennas have gained massive interest. There exist inadequate literatures about review of current state of extensive study reports on metamaterial application for patch antenna performance enhancement. Thus, this paper has reviewed and discussed latest research works on metamaterial applications for performance enhancement of planar patch antennas.

Capacity Enhancement of a Radial Distribution Grid Using Smart Transformer

Distributed generation (DG) and electric vehicle (EV) are increasingly installed in the modern microgrids (MGs). This demands for an improvement in the power handling capacity of the existing distribution feeders. The power handling capacity of a feeder is limited by the voltage magnitude violation caused by overloading. The smart transformer (ST) is proposed as an effective solution for improving the performance of modern MG. This paper utilizes the power management capabilities of the ST with an integrated battery energy storage system (BESS) for improving the power handling capacity of a medium voltage (MV) 5-bus radial feeder. The proposed method demonstrates the ST's capability to control the active and/or reactive power flow at the MV grid for maintaining the steady-state voltage magnitude within the grid-specified limit. A sensitivity analysis based design study is proposed to determine the power rating requirements for different ST and BESS converters during distinct power control scenarios. The analysis shows the capability of ST in injecting/absorbing active and reactive powers in flexible combinations for achieving the desired voltage magnitudes. The findings are verified through simulation and experimental results.

Coir Composite Based Electronics for Microwave Charging of Electric Vehicles

Electric vehicles are becoming popular due to environmental concern and reduction in battery costs. Several charging methods are being investigated including microwave wireless charging. Design of low profile, planar transmission lines and antenna with high power handling capacity forms the backbone of microwave charging of electric vehicles. Unconventional substrates including coir provide good scope for designing planar structures with high power handling capacity. A novel low cost microstrip antenna and transmission line using Coir Phenol formaldehyde composite as a dielectric substrate is proposed. This is expected to be simple, easy-to-produce and inexpensive. The prototypes are designed, fabricated and measured for resonance frequency of 2.45GHz. The microwave parameters including ’S’ matrix and gain are simulated using electromagnetic simulator HFSS. Experimental results employing VNA E5080A showed good consonance with simulated results in the frequency range 900MHz to 4.0GHz. Encouraging terminal voltage is obtained at 2.45GHz making this substrate a potential candidate for vehicle charging applications.

Compact circular polarizer based on cross-shaped slot for high-power microwave applications.

A compact high-power waveguide circular polarizer working at the C-band is presented in this paper. By introducing a split-ring slot and an orthogonally crossed rectangular slot into a circular waveguide, high transmission efficiency and 90° phase difference of two linearly polarized orthogonal TE11 modes are achieved by using the polarizer within a half wavelength. In the meantime, the power handling capacity of the designed polarizer is expected to be over 120 MW, which can be applied in the high-power microwave region. The designed circular polarizer is fabricated and measured by the cold test; the results of experiments and simulations agree well with each other. It is shown in the experiments that the axial ratio is less than 0.9 dB, the voltage standing-wave ratio is less than 1.2, and the conversion efficiency is over -0.15 dB at 4.2-4.4 GHz.

A Novel High-Efficiency Segmented Design Method for High-Power Serpentine Shaped Mode Converter

A segmented design scheme based on the iterative approach is proposed for the design of high-power serpentine shaped TM01–TE11 mode converter. It is found that the maximum electric field strength ( $E_{\mathrm {max}}$ ) in a serpentine shaped mode converter is related to the power ratio of the TM01 and TE11 modes at crux positions where the two modes have phase difference of $n\pi $ . Moreover, the bending direction of the serpentine axis at the crux positions needs to be adjusted to ensure high-efficiency power conversion from TM01 to TE11. By dividing the serpentine converter into several segments at the crux positions, and specifying the power ratio of the TM01 and TE11 modes, an improved iterative method using phase self-adaption and phase normalization is proposed for the design of the segmented serpentine structures with the desired $E_{\mathrm {max}}$ . For demonstration, a tri-bend TM01–TE11 mode converter was designed at $X$ -band for the specified $E_{\mathrm {max}}$ of 5 GW power input. Both the simulated and tested results of the conversion efficiency and electric field distribution are consistent with the theoretical predictions. Due to a quick estimation of the maximum power handling capacity of a serpentine shaped mode converter with arbitrary diameter, the proposed method has the merits of quick convergence and high computation efficiency.

Higher order mode coupler for the circular electron positron collider

A conceptual design report (CDR) for the Circular Electron Positron Collider (CEPC) was published in September 2018. CEPC will use a 650 MHz radiofrequency (RF) system with 240 two-cell cavities. The collider will be a double ring with shared cavities for Higgs operation and separate cavities for W and Z operations. The higher order modes (HOMs) excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. This study examined the impedance budget and HOM damping requirements for the CEPC ring to keep the beam stable, and a coaxial HOM coupler was considered for extracting the beam-induced HOM power. A double-notch coupler was chosen because of its wide bandwidth for the fundamental mode. Each cavity has two detachable coaxial HOM couplers mounted on the cavity beam pipe with a HOM power handling capacity of 1 kW. This paper presents the design process of the HOM coupler: the RF design, thermal analysis, and mechanical aspects. To validate the design, a prototype of the HOM coupler and a coaxial line test bench were fabricated and tested, and the test results agreed well with the simulation results. The HOM damping results for a real 650 MHz two-cell cavity were also measured and compared with the damping requirements.

Ku-Band Radial-Line Continuous Transverse Stub Antenna With Transmit-Array Lens for High-Power Microwave Application

An antenna operating at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band for high-power microwave (HPM) applications is presented in this article. The antenna can realize directional radiation of the coaxial transverse electromagnetic (TEM) mode and form a pencil beam in the desired direction. The antenna contains two parts: a radial-line continuous transverse stub antenna (RL-CTSA) as a feed antenna and two transmit-array (T-A) lenses. The RL-CTSA is designed to be a standing wave antenna, and the CTSA is step sized and arranged concentrically on the antenna aperture. The T-A lens consists of numerous elliptical-hole elements and can achieve a full transmission phase of 360° by rotating the elliptical-hole elements. An antenna prototype operating at 14.25 GHz has been designed and fabricated with an aperture radius of 300 mm. The experimental results show that the antenna has a gain of 37.9 dBi with a 21° deflection in elevation plane. The aperture efficiency reaches 75.1%, the reflectance is below −20 dB, and the radiation efficiency is more than 94.0%. Furthermore, high-power tests indicate that the power handling capacity of the antenna is higher than 250 MW.

Design of Class F Power Amplifier for 2.4ghz using Third Harmonics

Historically, travelling wave tube amplifier (TWTA) has been a common type of Microwave amplifier used commonly in terrestrial and space application due to their high efficiency and power handling capacity. However due to their bulky nature and also being very expensive, it is difficult to use them commercially in a large scale. Inspired by the advantage such as very less development cost, minimum supply voltage, gradual degradation and numerous commercial applications, Solid State Power Amplifier (SSPA) has been the replacement to vacuum tube Technology. The efficiency of the amplifier is one of the most important task in the microwave engineering research. An important figure of merit, power-added efficiency (PAE), is the main focus. Hence in this paper, class F Power amplifier is designed for 2.4GHz frequency. Class F Amplifier is also called as wave shaping amplifier since the harmonics generated helps the amplification process. The class f PA is biased nearer to the class B amplifier (close cut-off area) so the transistor can move back and forth rapidly to produce the harmonics. The efficiency of class F amplifier depends on how many harmonics are used for the amplification process. Here, the amplification process is performed up to the third harmonics which provides 41.606 dBm output power with 27dBm input power. Also a gain of more than 20.277dBm is achieved when the input given is 27dBm. Several other results like reflection Coefficient and transmission coefficient simulations has also been provided with the power added efficiency (PAE) of 75.402 achieved has also been simulated.

X-band reflectarray antenna with arbitrarily (elliptical) polarization for high-power microwave applications

An X-band high-power microwave antenna with arbitrarily (elliptical) polarization is proposed and investigated in this paper. The proposed antenna is founded on a reflectarray composed of printed elements and excited by the microwave energy in the azimuthally symmetric mode. The design procedure starts by calculating the phase difference between rays arriving at arbitrary points on the reflectarray aperture. This phase difference is then compensated by the reflectarray elements to realize the directional radiation of the azimuthally symmetric mode. Square metallic loops inside of a wire grid are used as phase shift elements, and phase variation over the reflectarray aperture is achieved through varying the inside dimension of square loops. An antenna prototype is fabricated to validate the proposed approach. The radiation characteristics of the antenna are measured, and there is a good agreement between simulation and measurement. Measured results show that the boresight gain and axial ratio at 10 GHz are 21.66 dB and 1.4 dB, respectively. The full-wave simulations prove the power-handling capacity of more than 1 MW for this antenna. The proposed antenna is significantly capable for high-power microwave applications, which is due to its compactness, the simple structure, its high-gain and high-power capabilities.

Analysis and design of TEM-TE11 coaxial waveguide bend mode converters

AbstractTwo coaxial waveguide bend mode converters that transform coaxial transverse electromagnetic mode to TE11 coaxial waveguide mode are presented in this paper. Both converters are designed and optimized on the basis of the strictly derived mode coupling coefficients. Conversion efficiencies of both converters are over 99% and the power-handling capacities reach a gigawatt level. The combined dual-bend mode converter is fabricated and tested. The experimental results coincide well with the theoretical calculations and simulations, which demonstrates the feasibility of the designed converter.

Design of a Yagi-Uda Antenna With Gain and Bandwidth Enhancement for Wi-Fi and Wi-Max Applications

There are various patch antennas used for Wi-Fi and Wi-MAX applications. But, the problems with them are low gain, low power handling capacity and hence, conventional yagi-uda antennas are used. Conventional yagi-uda antennas are used in applications where high gain and directionality are required. Generally, numbers of directors are added to increase gain of these antennas. But, here we present modified yagi-uda antennas, in which the gain and bandwidth can be enhanced by not adding additional directors. In this paper, we initially discuss the designs of various yagi-uda antennas with uniform, non-uniform spacings between directors and then we discuss their gain and bandwidth enhancement by various approaches. Simulation results show that, the proposed techniques can enhance gain as well as bandwidth when compared with the traditional yagi-uda antennas.

Novel design and analysis of RF MEMS shunt capacitive switch for radar and satellite communications

&lt;span&gt;In this paper, a new type of Radio Frequency Micro-Electro-Mechanical System (RF-MEMS) shunt capacitive switch is designed and studied. RF MEMS switch has a number of advantages in a modern telecommunication system such as low power consumption, easy to fabricate and power handling capacity at radio frequency. At high frequency applications, this switch shows very superior performance due to which it now became one of the key elements for RF application. In this proposed design, an innovative type of MEMS switch is designed. The MEMS switch structure consists of substrate, co-planar waveguide (CPW), dielectric material and a metallic bridge. The proposed MEMS switch has a dimension of 508 µm × 620 µm with a height of 500 µm. The substrate used is GaAs material. The relative permittivity of the substrate is 12.9. This proposed MEMS switch is designed and simulated in both UP (ON) state and DOWN (OFF) state. The proposed RF-MEMS switch is designed and simulated using Ansoft High frequency structure simulator (HFSS) electromagnetic simulator. The simulated result shows better performance parameters such as return loss ( &amp;lt;-10 dB) and insertion loss ( &amp;gt; -0.5 dB) in UP state, whereas return loss ( &amp;gt; -0.5 dB) and isolation (&amp;lt;-10 dB) in DOWN state. This switch has good isolation characteristics of – 43 dB at 27 GHz frequency.&lt;/span&gt;

Distributed power flow control using cascaded multilevel isolated bidirectional DC–DC converter with multi‐phase shift modulation

This study proposes a cascaded multilevel isolated bidirectional DC–DC converter (CMIBDC) suitable for large capacity energy storage applications. Compared to conventional IBDC, the proposed converter has higher power-handling capacity distributed among multiple cascaded HV and LV bridges. The HV bridges are cascaded through a high-frequency transformer with a common DC bus. On the other hand, the LV bridges are directly cascaded with isolated DC storage batteries. Effectively, the CMIBDC requires only a single DC input to store the energy in multiple battery units. A multi-phase shift (MPS) modulation scheme has been introduced which provide wide range of power flow control. The MPS modulation shapes the high-frequency link AC current with low THD thus reducing high-frequency losses. Detailed operating waveforms of the proposed CMIBDC converter in different modes are presented. The performance of the proposed converter and modulation scheme has been demonstrated through PSCAD/EMTDC simulation and validated experimentally using Spartan 3AN FPGA processor-controlled CMIBDC.

A Polarization Conversion Radome for High-Power Microwave Applications

A polarization conversion radome with embedded meander line with high-power microwave applications potential is presented. This radome is sandwiched by three-layer dielectric and two-layer metal meander line. The metal meander line is used to achieve polarization conversion, and the sandwich structure is used to avoid the contact between air and metal and then increase power handling capacity. After optimizing unit cell parameters, a polarization conversion radome with embedded meander line is constructed and loaded on the radial-line helical array antenna. The simulated and measured results show that the incident circular polarization wave is converted to a transmitted linear polarization wave well, and the antenna system is matched well in different radiation directions. The simulated results show that the polarization conversion radome with embedded meander line has great applications potential for high-power microwave field.

Theoretical research on power handling capacity of the modes TM01 and TM02 in corrugated waveguides

This paper studies the power handling capacity of the modes TM01 and TM02 in circumferentially corrugated waveguides through analytical research on the evolution of the field distribution and the corresponding dispersion with an overmoded ratio. As the overmoded ratio grows at the constant frequency, the total electric field of the volumetric wave, in which the amplitude of the axial electric field reaches its peak value on the central axis and declines along the r-axis, gradually concentrates toward the corrugated surface; the volumetric wave is then converted into a surface wave. Such conversion does not completely prevent, but weakens the enhancement of the power handling capacity caused by augmentation of the overmoded ratio. Moreover, due to the effect of the longitudinal mode transition, the power handling capacity of the modes TM01 and TM02 does not monotonically increase as the overmoded ratio grows with the constant frequency. Such longitudinal mode transition counteracts, to some extent, the enhancement of the power handling capacity caused by augmentation of the overmoded ratio. Even when the average radius of the corrugated waveguide is only a little larger than the cutoff radius of the required frequency, the power handling capacity decreases dramatically with augmentation of the overmoded ratio. A comparison between the different types of ripple demonstrates that a smaller corrugation pitch results in a lower power handling capacity. The advantage of the power handling capacity of the TM02 mode over that of the TM01 mode is proved by a careful comparison between the different cases.

A novel TM01-TE01 high-power microwave mode converter

This study presents the design and simulation of a novel type of TM01-TE01 mode converter for high-power microwave applications, which efficiently converts the TM01 circular waveguide mode into the TE01 circular waveguide mode. The converter is composed of three sections: power-dividing section, twist-waveguide section and power-combining section. These sections were analyzed and discussed respectively, and the whole converter structure was studied numerically. The results show that at the central frequency 12.5 GHz, the TM01-TE01 conversion loss of the converter made of aluminum is 0.05 dB and the bandwidth for S21 &amp;gt; 0.25 dB is 2.73 GHz. Moreover, the power-handling capacity is over 2 GW.

A High-Power Microwave Reflectarray Antenna Based on Perforated Dielectric Substrate

A high power microwave antenna based on the reflectarray concept is designed and investigated in this paper. The reflectarray aperture is directly driven by an azimuthally symmetric mode and a directional boresight beam is realized through azimuthally introducing a phase shift of 90 to the phase shift profile of reflectarray unit cells. A sample model operating at X-band is designed to verify the validity of the proposed approach. Variable diameter air-filled holes through a host dielectric material are exploited as the phase-shifting unit cells because of the advantage of higher power handling capacity. Theoretical analysis and full-wave simulations are accomplished and results are in good agreements. A collimated beam of circular polarization with peak gain of 20.2 dB and axial ratio of 1.3 are achieved at the boresight direction for the design frequency of 10 GHz. The radiation performance of the proposed antenna as well as its compact structure makes it a potential candidate for high gain high power applications.

Design of a TE01-Mode Waveguide Bend Based on an Elliptical Waveguide Structure

A Ka-band broadband TE01-mode overmoded waveguide bend based on an elliptical waveguide structure is proposed for high-power transmission line in this paper. To investigate the mode conversion inside the waveguide bend, the mode coupling coefficients of elliptical waveguide bend are theoretically deduced. The influence of the cross section on the power-handling capacity and the transmission efficiency is studied. Calculation and simulation results present that the proposed overmoded waveguide bend has a propagation bandwidth of 7 GHz (relative bandwidth of 21%) with an efficiency over 95%. A prototype is fabricated and measured. The average transmission efficiency is over 93% in the range of 29–36 GHz according to the S-parameter measurement. The results of near-field test demonstrated that a TE01 mode with high purity is obtained at the output port of waveguide bend. The high-power performance is investigated by connecting it with a Gyrotron traveling wave tube, and the waveguide bend works stable under a maximum output power of 150 kW. The measurement results demonstrate that a novel approach is proposed successfully for the design of high-power waveguide bend.

Effect of magnetic field tapering on whistler pumped free electron laser

An analytical formalism of whistler pumped free electron laser (FEL) with tapered magnetic field is developed. The tapering raises the efficiency of the device to 7% for typical parameters. The frequency and power of the FEL can be controlled by tuning the plasma density and/or magnetic field also by increasing the energy of electron beam. The angle of injection of electron beam is very crucial for higher efficiency of FEL. Presence of plasma ensures the space charge and current neutralization and larger power handling capacity of the device.

Design and experimental demonstration of a TEM-TE10 phase shifter for high-power microwave applications.

A novel phase shifter used to adjust the output phase of high power microwave (HPM) is investigated. The phase shifter is composed of two different circular polarizers, one of which can convert the coaxial transverse electromagnetic mode (TEM) into circularly polarized (CP) TE11 mode, and the other one can realize the transformation between the CP TE11 mode and the rectangular TE10 mode. The two circular polarizers are connected by a circular waveguide, and the TEM-TE11 circular polarizer can rotate around its axis continuously. In this way, the phase shifter can adjust the output phase of the TE10 mode in the range of 0°-360°. In this paper, the principle of a phase shifter working at 1.57 GHz, as well as the experimental results, is demonstrated. The experimental and simulation results are in good agreement. At the central frequency, the transmission efficiency in this range of phase-shifting process is over 94.6%, and the power-handling capacity is as high as 1.5 GW. This novel phase shifter is of interest to HPM spatial power combination technologies.