Experimental Methods In Rf Desig
Abstract:With the globalization of the integrated circuit (IC) design flow of chip fabrication, intellectual property (IP) piracy is becoming the main security threat. While most of the protection methods are dedicated for digital circuits, we are trying to protect radio-frequency (RF) designs. For the first time, we applied the split manufacturing method in RF circuit protection. Three different implementation cases are introduced for security and design overhead tradeoffs, i.e., the removal of the top metal layer, the removal of the top two metal layers and the design obfuscation dedicated to RF circuits. We also developed a quantitative security evaluation method to measure the protection level of RF designs under split manufacturing. Finally, a simple Class AB power amplifier and a more sophisticated Class E power amplifier are used for the demonstration through which we prove that: (1) the removal of top metal layer or the top two metal layers can provide high-level protection for RF circuits with a lower request to domestic foundries; (2) the design obfuscation method provides the highest level of circuit protection, though at the cost of design overhead; and (3) split manufacturing may be more suitable for RF designs than for digital circuits, and it can effectively reduce IP piracy in untrusted off-shore foundries.Keywords: hardware trust; IP piracy; power amplifier; RF circuit; split manufacturing
Experimental Methods In Rf Desig
Explore wide dynamic range, low distortion radio equipment, the use of direct conversion and phasing methods, and digital signal processing. Use the models and discussion to design, build and measure equipment at both the circuit and the system level. Laced with new unpublished projects and illustrated with CW and SSB gear.
Funding: This work was supported by institutional funding provided by the Max-Delbrück Center for Molecular Medicine, Berlin, Germany provided to Prof. Thoralf Niendorf. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Basic design of the proposed bow tie dipole antenna building block used in numerical EMF simulations (a). Eight bow tie dipole antennas placed radially around a cylindrical phantom (b). Transversal view of the virtual phantom setup together with the bow tie dipole antennas (c).
Temperature simulations were performed at 298 MHz using the parameters found in the experimental setup with a background temperature of 20C and an input power of 50 W per channel. To simulate the effect of RF heating over a three minute time period, the temperature was calculated based on the power loss distribution of an in-phase phase setting (Ch1-8: 0). This setup yielded a deep lying hotspot in the center of the phantom. To demonstrate 2D hotspot steering RF heating over two minutes using a specific set of phases (Ch1: 0, Ch2:45, Ch3:180, Ch4:225, Ch5:0, Ch6:225, Ch7:135, Ch8:45) for the eight elements was applied.
Basic design and dimensions of the bow tie dipole building block used for MR imaging, MR thermometry and RF heating at 7.0 T (a). Picture photographs taken from the front, back and side of the bow tie antenna building block (b). Picture photograph of the cable trap design using semi rigid cable. Schematic diagram of the matching and tuning network connected to the antenna (d).
For the hybrid multichannel applicator eight bow tie elements were placed in an equidistant radial pattern in a stereotactic holder. For accurate placement of the eight antennas the holder was created using a 3D computer aided design (CAD) model developed with Autodesk Inventor 2011 (Autodesk Inc., San Rafael, CA, USA). The holder was plotted with a 3D rapid prototyping system (BST 1200 es, Dimension Inc., Eden Prairie, MN, USA) using ABS+ material. Figure 3 illustrates the final setup of the 8 channel hybrid TX/RX applicator tailored for MR imaging, MR thermometry and targeted RF heating in a 7.0 T environment.
Picture photograph of the eight channel TX/RX hybrid applicator implemented at 7.0T together with annotations that induce the transmission channel number (left). Picture photograph of the experimental setup which uses the hybrid applicator together with a cylindrical phantom at 7.0T (right).
For absolute temperature measurements and for validation of the MR thermometry maps, four optical thermo sensors were employed (OmniFlex, Neoptix, Quebec, Canada). Temperature calibration measurements were performed to scrutinize the accuracy of the MRTh method, yielding an experimental absolute error of 1 K and a relative error of 0.2 K for the fiber optic approach and 2 K for MRTh.
Axial and coronal views of specific absorption rate (left) and temperature (middle) distribution derived from EMF and temperature simulations using the 8 channel applicator, a cylindrical phantom and a 1H excitation frequency of 298 MHz. For comparison, a temperature map derived from MRTh acquisitions at 7T (298 MHz) using the TX/RX applicator is shown (right). For the experimental setup a heating period of 120 s was used. A set of phase shifts (Ch1:0, Ch2:45, Ch3:180, Ch4:225, Ch5:0, Ch6:225, Ch7:135, Ch8:45) between the bow tie antennas was used to steer the SAR and temperature hotspot towards the surface of the phantom.
The observation that the hotspot dimensions in the phantom are more focused when using higher frequencies has major implications for future hybrid applicator designs. The size of the antenna elements can be reduced significantly at higher frequencies. This reduction in antenna size would afford a placement of even more transmission elements around the area of interest. This approach would support the intention of spreading the surface SAR more evenly across the surface and would help to further increase the SARcenter/SARsurface ratio. An increase in the number of independent transmission elements - each with exquisite phase and amplitude control - would also be instrumental to further sharpen the geometry and size of the temperature hotspot.
It is a recognized limitation of this feasibility study that only 2D steering has been used to move the SAR and temperature hotspot to an arbitrary position in the phantom. For this reason we anticipate an arrangement of bow tie antennas not only in the axial plane, but also along the direction of the main magnetic field (z-axis) to enable 3D steering capabilities of the SAR/temperature hotspots. These efforts will be paralleled by moving towards a heterogeneous head phantom, which would enable a more realistic model for the assessment of thermal distributions. For this purpose we anticipate to position/design the antennas in such a way, that the Poynting vector is perpendicular to the electromagnetic boundary layer (cranium in case of the human brain) and directed towards the targeted region of interest. Such an arrangement with a directed EM energy towards the focus point, while more realistic, will potentially reduce the 3D hotspot dimension in z-direction as compared to the cylindrical phantom setup used in this study.
Conceived and designed the experiments: LW CÖ. Performed the experiments: LW CÖ. Analyzed the data: LW CÖ DS TN. Contributed reagents/materials/analysis tools: LW CÖ WH DS AM HW RS AG PW TN. Wrote the paper: LW TN.
RF MARKER SIMULATION MODEL FOR INTERVENTIONAL MRI APPLICATIONSCompared to the other imaging modalities Magnetic Resonance Imaging (MRI) system has many advantages. There is a great demand to carry out interventional cardiovascular procedures under MRI scanner. However, the lack of visible markers and MRI compatible interventional instruments and devices, is the main problem for realizing clinical applications with MRI guidance. In order to provide widespread usage of MRI for endovascular operations, commercial catheters and guidewires must be manufactured by considering many performance criteria including visualization, miniaturization, flexibility and safety. In this study, an orientation independent simulation model was developed and validated to obtain a reliable method for evaluating the designed RF marker structures in a MRI environment. Utilized RF coil designs have similar size and properties with former constructed clinical grade MRI compatible RF markers in experimental works [1]. Finite Element Method (FEM) simulations were carried out for different RF coil designs to make the computational analysis of their electrical and magnetic characteristics by using COMSOL Multiphysics program.By delineating an approved simulation platform of a MRI environment, various different designs of RF marker prototypes can be compared between each other in many aspects, instead of realizing these models. Proposed simulation platform enables a convenient facility to determine various parameters of micro coils that have significant effects on visibility and safety performance of the candidate designs including signal to noise ratio (SNR) and Quality (Q) factor, RF induced heating and specific absorption rate (SAR).
Conversion coatings are used to inhibit corrosion on aluminum structures while maintaining electrical conductivity. The most common type of conversion coatings in aerospace applications (MIL-DTL-5541 Type I), contain hexavalent chromium compounds as the corrosion-inhibiting additive. These Type I conversion coatings have a long pedigree and are highly effective in preventing corrosion; however, the hexavalent chromium compounds in these coatings are carcinogenic and water-soluble. Therefore, the use of these compounds is highly regulated in order to protect both workers and the public leading to high cost in both use and disposal. In addition to these regulations, use of these materials on new designs for DOD is prohibited by DFARS 48 CFR Parts 223 and 252, and is scheduled to be prohibited in Europe in September 2017 by REACH regulations. In response, new more environmentally friendly non-hexavalent chromium-based processes are becoming available. Coatings resulting from these types of processes are referred to as MIL-DTL-5541 Type II conversion coatings. The long term reliability and performance impacts resulting from the use of these coatings are not fully understood and there currently is an effort in the U. S. aerospace industry organized by NASA to fully define these impacts while hardware is still in the design stage. 350c69d7ab
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