RF System Research Articles

Mrs HYBRID MUTUAL COUPLING REDUCTION TECHNIQUES IN MULTIPLE INPUT AND MULTIPLE OUTPUT ANTENNA FOR X-BAND APPLICATIONS

In recent years, Multiple Input and Multiple Output antennas (MIMO) used for high-bandwidth communications where it's important to not have interference from microwave or RF systems. The MIMO antenna offers good matching with stable gain and desired radiation patterns but it suffers on mutual coupling effects. The spacing between antenna elements is less than half the wavelength, and then mutual coupling effects are more. This paper provides a review on different mutual coupling reduction techniques in MIMO antenna. In this letter, a hybrid mutual coupling reduction technique such as substrate integrated waveguide (SIW) and defected ground structure (DGS) in MIMO antennas for X-band applications. The developed MIMO antenna has dimensions as 25 x 36 mm over a FR4 1.6 mm substrate. The MIMO antenna has formed by combining two fractal-shaped structures. Here, the antenna element spacing is taken as minimum of 5.62mm. To reduce the mutual coupling effect and enhance gain, hybrid techniques are used. By adding 24 hollow cylindrical SIW is placed in between a MIMO element and six rectangular DGS slots placed at the bottom of the antenna for reducing the mutual coupling and enhance the gain. The proposed antenna operates at resonating frequencies of 10.04 GHz, 11.14 GHz, and 11.69 GHz for measurement. The mutual coupling or isolation loss was observed around <-25 dB. The envelope correlation coefficient (ECC) and diversity gain (DG) of the proposed antenna are 0.0016 and >9 dB, respectively. The gain observed for the proposed design is 5.2 dB. The Ansys high-frequency structure simulator (HFSS) tool is used for antenna simulation.

Unveiling a half-century mystery of molecular bases for three-line hybrid rice breeding system.

Hybrid rice derived from Wild Abortive (WA) cytoplasmic male sterility type three-line systems is widely used in production. The fertility restoration gene Rf4 can reduce WA352c transcript levels in a dose-dependent manner. A two-copy haplotype of Rf4 (H1) is identified as the most valuable haplotype for future hybrid rice breeding.

RF conditioning towards continuous wave of the RFQ of the Linear IFMIF Prototype Accelerator

The Linear IFMIF Prototype Accelerator (LIPAc) is designed to accelerate 125mA of deuteron beam to 9MeV in continuous wave (CW). The superconductive RF Linac has not yet been installed and the final accelerating stage now under commissioning is the RFQ. This system has been designed and developed by INFN (Italy) before installation in QST (Japan). The RFQ is the longest in the World with its 9.8m and requires RF power injection from 8 independent and synchronized coupler ports. LIPAc demonstrated the acceleration of 125mA deuteron beam at 5MeV for 1ms with a 1s repetition period in 2019. A fundamental milestone to extend beam operations to CW is the completion of the RFQ cavity RF conditioning up to CW. This work presents the strategy followed to successfully reach CW RF injection at 80% of the nominal 132kV vane voltage. The field distribution correction scheme (acting on cooling system at various power levels) was successfully verified. We discuss as well the main challenges encountered on the way, which include updates of the RF system, failure of a circulator (by arcs) and the damages occurred on some of the RF couplers. Finally, the recent status and outlook will be provided.

Simulation study on the slow extraction for the improvement of the beam shill structure at J-PARC Main Ring

J-PARC Main Ring (MR) delivers a slow extracted 30 GeV proton beam to the Hadron Experimental Facility using third-order resonance. One of the critical properties required for the proton beam is the flatness of the time structure of the extracted beam (spill structure). We performed a simple beam simulation of the MR slow beam extraction to investigate the effect of the current ripples of the main magnet power supplies on the beam spill structure. In addition, we investigated in the simulation the effects of the feedback control system on the betatron tune using fast Q magnets and the transverse RF system to improve the spill structure. The simulation qualitatively reproduced the measured spill structures. Now the attempts to optimize their parameters for better spill structure are ongoing.

FAIR SIS100 accelerating RF system - Modeling and analysis of the coupled LLRF control loops

The SIS100 heavy ion synchrotron as core part of the Facility for Antiproton and Ion Research (FAIR) will be equipped with 14 accelerating RF stations in the first stage of realization. Each RF station consists of a tunable ferrite-loaded cavity powered by a tetrode amplifier. Further key components are a solid-state pre-amplifier, a power supply unit, and dedicated Low-Level Radio Frequency (LLRF) feedforward and feedback systems to control amplitude and phase of the cavity gap voltage as well as the resonance frequency. Each cavity has to provide up to 20 kV peak gap voltage in the frequency range from 1.1 to 3.2 MHz. While all components of the system have been successfully tested in the factory acceptance tests and transferred to the FAIR storage, the First-of-Series (FoS) RF station is still persistently operated at GSI to gain experience. For further insight into the LLRF part, especially the stability of the control loops, the inter-coupling of the three local control loops was analyzed with methods from control theory based on simplified but realistic models, which have been developed based on extensive measurements and analysis of the systems’ behavior. In this contribution, the modeling as well as the analysis of the coupling between the LLRF control loops are discussed and the results are presented in comparison with measurements on the FoS system.

Energy Saving Measures in the High-Power RF System of the European XFEL

The high-voltage modulators of the 26 klystrons in the XFEL represent the largest power consumer of the accelerator facility. The beam energy is usually 14 GeV, but a few weeks a year, lower and higher beam energies are also produced. For example, 11.5 and 16.3 GeV. Until mid-2022, the modulator voltages were set so that enough RF power for 16.3 GeV beam energy could be provided at all times. In order to save energy, the modulator voltages will now be lowered to a sufficient level for beam energies of ≤ 14 GeV. In this way, the previous power consumption of the modulators of 5 MW can be reduced up to 1 MW depending on the operation mode. Over the course of a year, this will save several GWh of energy. In the following, the relationship between the output voltage and the power consumption of the modulators is described. Afterwards, it is reported how the power consumption was reduced in various operating conditions in 2022.

Tuner Loop Based on FPGA for Petra Cavity at TPS Booster Ring

The low-level radio frequency system of the Taiwan Photon Source, TPS, booster ring was replaced by the digital low-level RF system, DLLRF, in 2018. After that, the phase drift compensation loop for energy-saving operation and the tuner loop were also implemented in the DLLRF system sequentially. We used Altera-DE3 to build the core of DLLRF and handle the high-speed ADC/DAC procedure for RF signal sampling. As we con-sider the response time of the tuner, we choose an-other low-cost board, Altera-DE0-Nano, to develop the tuner loop for 5-Cell-Petra-Cavity. It has an eight-channel 12-bits-ADC, 150 ksps, ADC128S022, to detect the positions of two tuners and two transmitted powers sampled from two cells of the 5-Cell-Petra-Cavity for a power balance function. The phase information of for-ward power and cavity gap voltage will come from the Altera-DE3 to tell the tuner loop in the Altera-DE0-Nano whether the cavity is on resonance or not. The tuner loop controls the cavity to work not only at the resonance frequency but also with a balanced electric field distribution. This study presents the tuner loop’s architecture, including the locking resonance frequency and field balance functions. The performance of the field balance function is observed by the archive data of the two tuners positions and two transmit power signals.

Environmental Life-Cycle Assessment (LCA) of Wireless RF Systems: A Comparative Sustainability Analysis and a Microwave Engineers' Guide to LCA

Environmental Life-Cycle Assessment (LCA) of Wireless RF Systems: A Comparative Sustainability Analysis and a Microwave Engineers' Guide to LCA

Enhanced Performance in Mixed THz and Multi-antenna RF Systems With MRC Diversity

Enhanced Performance in Mixed THz and Multi-antenna RF Systems With MRC Diversity

Design and commissioning of a wideband RF system for CSNS-II rapid-cycling synchrotron

Design and commissioning of a wideband RF system for CSNS-II rapid-cycling synchrotron

Research on longitudinal dynamics and design of RF parameters of synchrotron for XiPAF-upgrading project

Xi ’an 200 MeV Proton Application Facility (XiPAF) will be upgraded to proton and heavy ion synchrotron recently. In order to ensure the enough life of heavy ion beam, the synchrotron requires ultra-high vacuum, and the designed static vacuum is better than 5×10-10 Pa. In order to place enough vacuum pumps in the synchrotron, the circumference of the synchrotron was increased from 30.9 m to 39.96 m. The revolution frequency range of heavy ions is 0.49∼1.03 MHz. In order to reduce the engineering difficulty and improve the lower limit of frequency bandwidth requirement of the RF system, the harmonic of h=2 is used to capture and accelerate the heavy ions, and the frequency bandwidth range of the RF system is adjusted from 1∼6 MHz to 0.8∼5.0 MHz. In this paper, the longitudinal dynamics parameters of the upgraded synchrotron are designed, and the simulation calculation is carried out. Finally, the parameter requirements of the RF system are proposed.

DESIGN, CONSTRUCTION AND TESTING OF CELLPHONE DETECTOR

A cell phone detector is a device specifically designed to detect and locate the presence of a cell phone in a specific area. Cell phone detection has been studied for a long time. Techniques have been developed or proposed on how to detect cell phones. Most of them are trying to exploit features such as audio systems, RF systems, and common materials in phones and study how these can be used as the basis for cell phone detection. This study uses the cell phone's RF system as a function to detect the presence of a cell phone. Using relatively inexpensive and available electronic components, a circuit that detects signals in the 0.9 GHz to 3 GHz range is used to detect a mobile phone in use. The constructed cell phone detector can detect the presence of various activated cell phones within 1.5 meters around it and indicate this by flashing a light emitting diode (LED) connected to its output. Even if the cell phone is in silent mode. The circuit test results show that the cell phone detector works well.

Dynamic responses of multi-story structural systems with separated gravity and lateral resisting systems under seismic action considering connection semi-rigidity effects

This paper investigates the dynamic behaviour of an innovative structural system with separated gravity and lateral resisting systems (SGLR system), which is proposed for the prefabricated structures in multi-story buildings by enhancing the standardization of beams, under earthquake excitation. The seismic performance of SGLR system is benchmarked against the conventional rigid frame system (RF system) designed with the same maximum inter-story drift ratios, and the influences of connection semi-rigidity on the dynamic responses of SGLR system are focused on. Numerical models are built using the self-developed fiber beam-column elements for composite frames, beam elements for semi-rigid connections and multi-layer shell elements for shear walls based on a six-story prototype structure. The modal analysis indicates that the natural vibration periods of SGLR system are smaller than those of RF system and the connection semi-rigidity will further significantly decrease the periods for the first three orders. Nonlinear time history analysis is conducted under eight sets of ground motions at two different levels in two horizontal directions. The shear walls in SGLR system bear the majority of seismic action with damage concentrated in the bottom. The connection semi-rigidity will decrease the lateral deformation and increase the involvement of the frame part in the lateral resisting mechanism of SGLR system, which can be more significant when the semi-rigidity is higher. SGLR system exhibits better control of inter-story drift ratios considering connection semi-rigidity in low-rise buildings and higher economic efficiency in mid-rise buildings.

A P-type pentatricopeptide repeat protein ZmRF5 promotes 5' region partial cleavages of atp6c transcripts to restore the fertility of CMS-C maize by recruiting a splicing factor.

A fast evolution within mitochondria genome(s) often generates discords between nuclear and mitochondria, which is manifested as cytoplasmic male sterility (CMS) and fertility restoration (Rf) system. The maize CMS-C trait is regulated by the chimeric mitochondrial gene, atp6c, and can be recovered by the restorer gene ZmRf5. Through positional cloning in this study, we identified the nuclear restorer gene, ZmRf5, which encodes a P-type pentatricopeptide repeat (PPR) family protein. The over-expression of ZmRf5 brought back the fertility to CMS-C plants, whereas its genomic editing by CRISPR/Cas9 induced abortive pollens in the restorer line. ZmRF5 is sorted to mitochondria, and recruited RS31A, a splicing factor, through MORF8 to form a cleaving/restoring complex, which promoted the cleaving of the CMS-associated transcripts atp6c by shifting the major cleavage site from 480th nt to 344 th nt for fast degradation, and preserved just right amount of atp6c RNA for protein translation, providing adequate ATP6C to assembly complex V, thus restoring male fertility. Interestingly, ATP6C in the sterile line CMo17A, with similar cytology and physiology changes to YU87-1A, was accumulated much less than it in NMo17B, exhibiting a contrary trend in the YU87-1 nuclear genome previously reported, and was restored to normal level in the presence of ZmRF5. Collectively these findings unveil a new molecular mechanism underlying fertility restoration by which ZmRF5 cooperates with MORF8 and RS31A to restore CMS-C fertility in maize, complemented and perfected the sterility mechanism, and enrich the perspectives on communications between nucleus and mitochondria.

Progress in the energy upgrade of the Southern European Thomson back-scattering source (STAR)

The Southern European Thomson back-scattering source for Applied Research (STAR) is a high-energy photon facility located on the campus of the University of Calabria (UniCal). The facility was designed for its first phase to operate with an electron and photon energy up to 85 MeV and 140 keV respectively. For the second phase of the project the energy of the electrons, and thereby the photons, would be increased up to 150 MeV and 350 keV respectively. The Italian Institute for Nuclear Physics (INFN) was awarded the project for installing, testing, and commissioning the energy upgrade of the electron beamline. In this article, we will outline the progress of this upgrade. In particular the completion of the site acceptance test of the RF system and the IT infrastructure combined with the control system software.

Design of a compact filter integrated wideband and circularly polarized antenna array for K-band application

A compact filtering mechanism in the antenna system is required to avoid unwanted incoming electromagnetic waves in the working frequency band. A circularly polarized (CP), wideband, and high gain antenna array co-design with a wide bandpass filter (BPF) for a K-band satellite application at (17.7 to 21.2) GHz is studied in this paper. Antenna array elements with diagonal slots and BPF in the same frequency are compatible. For maximum radiation efficiency, the input impedance of the slotted 16 × 16 elements antenna array is matched to 50 Ω and equal to the output impedance of the BPF in the operating band. To implement the filtering concept, a co-design is modeled and simulated. The suggested wideband BPF and antenna array are integrated on a combined aperture, manufactured, and tested experimentally. Based on the results of the tests, it can be concluded that the suggested filtering antenna array is well matched (|S11| < −15 dB) throughout a wide frequency band of 17.7 GHz to 21.2 GHz. The final structure simulated and measured 3 dB axial ratio covers the functional spectrum with a maximum 25.3 dBi gain. High directive beams with a 20 dB cross-polarization suppression level in E & H planes are simulated and measured. Due to these advantages, the suggested antenna is an attractive option for use in K-band 3U satellite applications to minimize the requirement for extra filtering circuits in the RF system.

PERFORMANCE ANALYSIS OF HYBRID FSO / RF COMMUNICATION SYSTEM WITH RECEIVE DIVERSITY IN THE PRESENCE OF CHI-SQUARE/GAMMA TURBULENCE AND RICIAN FADING

Within mobile communication systems, the inherent limitations of mobile devices necessitate a considerable portion of signal processing to occur at the base station. The technique of multiple access at the base station, entailing the amalgamation of diverse received signals, plays a pivotal role in the reconstruction of the original signal. This investigation introduces an innovative hybrid FSO/RF system that operates via a single-hop transfer, adeptly incorporating the concept of receive diversity to effectively counteract the challenges posed by saturated atmospheric turbulence. It is important to note that the FSO channel is observed under the Gamma/Chi-Square turbulence model, while the RF channel adheres to the Rician fading model. Notably, the study also yields a closed-form expression for the outage probability of the system. The results underscore significant enhancements in comparison to conventional FSO and RF systems. Despite the demand for an advanced receiver, the proposed hybrid architecture presents substantial improvements that significantly impact the performance of the communication system. It's noteworthy that at the reception, the Switch and Stay (SSC) combining technique along with Selection Combining diversity (SC) strategies are being observed. This holistic approach not only addresses the challenges posed by atmospheric conditions but also harnesses the benefits of diversity techniques to enhance the overall reliability and performance of the communication system.

A low-frequency normal conducting cavity with higher-order mode damping for fourth-generation synchrotron radiation sources.

The utilization of a low-frequency (<200MHz) RF system in storage facilitates the attainment of ultra-low emittances in synchrotron light sources through on-axis injection. This paper focuses on the development of a low-frequency normal conducting (NC) cavity with higher-order mode (HOM) damping for fourth-generation synchrotron light sources. We propose a novel approach to achieve efficient HOM damping in a NC cavity by optimizing the lowest frequency HOM and implementing a beam-line absorber. Notably, unlike conventional NC cavities, the presence of a large beam tube for the beam-line absorber does not compromise the accelerating performance in a coaxial resonant cavity, enabling effective HOM damping while maintaining a high shunt impedance. Through simulations, the prototype design of a 166.6MHz HOM-damped cavity demonstrates a fundamental mode impedance of ∼8 MΩ, with longitudinal and transverse HOM impedances below 2.0 and 50 kΩ/m, respectively.

Optimisation of klystron operational efficiency at ESS

The power required by each cavity of the ESS superconducting linac varies along the length of the accelerator, which results in a wide range of power levels to be provided by the RF power sources. For the medium and high beta sections of the linac, the selected power sources are klystrons with a nominal maximum output power of 1.5 MW. Operating these klystrons as efficiently as possible is among the goals of the ESS objectives to approach a carbon-neutral facility, but the ESS power profile presents specific challenges. This paper will discuss some of the solutions that will be implemented to increase the operational efficiency of the RF systems, focusing on klystron operation.

RF-PSF: A CNN-Based Process Distinction Method Using Inadvertent RF Signatures

Stochastic variation of process parameters within a die and technology-limitation-driven variation from die-to-die give rise to unique distribution patterns for manufacturing process parameters. These patterns work as a process signature that is transferred from the device level to the system level through electrical circuits and can be used to make a distinction among the processes. In this work, we propose an in-situ manufacturing process technology distinction method‘, Radio Frequency Process Specific Functions (RF-PSF)’, that uses process-specific inherent properties of an IC manifested in the transmitted radio frequency signal. Among many desirable testing criteria, RF-PSF addresses the question of fabrication with the intended process technology. This information plays an important role in modern zero-trust architecture and IC clone detection, a counterfeiting method where the IC is manufactured using a different process. An RF transmitter with RF-DAC power amplifier for QPSK modulation has been designed and simulated in 14nm, 22nm, and 65nm processes for 5 process corners (TT, FF, FS, SF, and SS) in Cadence. The simulated data have been processed in MATLAB. A Multilayer Perceptron (MLP), trained with the constellation data, provides an average accuracy of ~90% for process distinction. Realizing that (i) a higher order modulation will have even more process information and (ii) we can harness the Convolutional Neural Network’s (CNN) improved capability on pattern recognition, we can feed image-like constellation plots to a CNN to get better and consistent performance. Using the baseband constellations for 64-QAM modulated data as images, we have achieved ~100% accuracy with commonly used, pretrained CNN models (ResNet18, ResNet50, and GoogleNet) through transfer learning. The separation among 5 process corners within a process, termed intra-process variation, is also analyzed. The effect of baseband sampling rate and ADC resolution, two practical limitations in RF systems, have been explored. An extensive study has been performed on the effect of a key design parameter at the RF circuit level i.e. W/L or aspect ratio, leading to design insights, proper CNN selection, and some control parameters. This work establishes RF-PSF as a zero-power, zero-area overhead, in-situ process distinction method.