Research on the RF Simulation Technology Based on High Frequency Hybrid Method

Some measures in hardware architecture and software platform to improve the real time performance are studied in this paper. A new control solution for array hardware-in-the-loop Radio Frequency Simulation System (RFSS) is proposed based on VMIC fiber-optic network and VISTA & RTX software platforms. The control arithmetic of the RFSS is also briefly introduced. Analysis shows that the new solution has large data throughput capacity and good real-time performance. Meantime the delay of system communication, processing arithmetic and terminal control unit are measured and the overall delay is tested. The results prove the stable real-time performance, universality and scalability of the control system.

To study the electromagnetic scattering characteristics of a V-shaped deformation quadrotor, a calculation approach is presented to determine the dynamic radar cross section (RCS). The rotation of the single/multi-rotor, the opening of the support arm and the deformation of the fuselage are dynamically simulated. Physical optics and physical theory of diffraction are used to calculate the target RCS. The results show that when undeformed, the presence of strong scattering sources such as support arms, rotor towers, and hubs allows for an instantaneous peak of 13.08 dBm 2 under given forward azimuth, and this peak indicator will decrease to 2.714 dBm 2 as the elevation angle increases. Under given conditions, the RCS mean index increases from 4.9693 dBm 2 to 8.7069 dBm 2 as the support arm angle increases from 10° to 50°. When the fuselage rotation angle increased from 20° to 80°, and the RCS mean decreased from 7.7414 dBm 2 to 5.1235 dBm 2 under given observation conditions. It is feasible for the presented method to study the RCS of the V-shaped deformed quadrotor.

The application of radar absorbing materials on the surface of metal aircraft can effectively reduce the radar cross section (RCS). In this paper, the physical optics (PO) method is used to calculate the RCS of electrically large coated targets. First, we calculate the RCS of the original X29 aircraft and the X29 aircraft coated with a broadband two-layer radar absorbing coating. In addition, the backscattered electric field data of coated and uncoated X29 aircraft are obtained by using the PO method, respectively. Finally, the two-dimensional Inverse Fourier Transform (IFT) of the collected data is taken to form the Inverse Synthetic Aperture Radar (ISAR) image.

Study on the near-field effect of spherical composite antenna arrays in the radio frequency simulation system

In this paper the 3-D mathematical formulation and study for the simulation of the radio-propagation mechanisms in urban cellular environments are presented. The proposed methods and techniques are applicable to the 3-D radiocoverage prediction model, currently being developed by the authors' research group. In the far field area, the proposed analysis is based on the well-known deterministic methods of Physical Optics (PO) and Physical Theory of Diffraction (PTD). In the near field and Fresnel zone, a novel and time-efficient technique for the computation of the scattered and diffracted field is applied. Emphasis is also given to the time efficiency of the proposed approach since the high simulation time is one of the most important drawbacks of such radio-propagation prediction codes.

As the classic analytical methods cannot calculate the electromagnetic scattering characteristics at Low Grazing Angle (LGA), a novel numerical method is presented by utilizing the Radar Cross Section (RCS) of the low grazing two-dimensional PM sea spectrum based on the triangles-based Physical Optics (PO) method in this paper. The calculated RCS is compared with the numerical calculation method of different targets and frequencies of incident wave. The results show that PO method is more accurate, especially under LGA condition, and it has a better agreement with the results calculated by commercial software FEKO.

In order to control its attitude, there usually have wings or other structures on the midcourse target. It is the foundation to simulate the radar echo of this kind of rotationally asymmetric target to get it recognized correctly. Firstly, the position variation of each scattering center on both the body and the wing is analyzed. After that, according to the high frequency method and local field theory, the RCS calculation formulas of body and wings of the target are derived with the Geometrical Theory of Diffraction(GTD) and Physical Optics(PO) method respectively. Then, a simple method is put forward to judge whether the wing is shielded with the target's movement according to the PO method. Finally, the wideband radar echo is simulated and the impacts of non-idealization of the scattering centers and rotationally asymmetry of the target on the echo are also analyzed.

The physical theory of diffraction (PTD) has been expanded for the case of slope diffraction, when an incident wave is zero but its derivative is not zero in the direction of a perfectly conducting scattering edge. High frequency asymptotics are found both for elementary edge waves and for the total edge waves scattered by arbitrary curved edges. Great attention is given to fields created by the nonuniform (diffraction) component of edge currents. These fields are usually called ptd corrections to the Physical Optics approach. These corrections are found for diffraction fields in ray regions and in diffraction regions such as the vicinities of shadow boundaries, smooth caustics, and foci.

With the continuous advancement of rotor dynamic electromagnetic scattering research, the radar cross-section (RCS) of turbofan engines has attracted more and more attention. In order to solve the electromagnetic scattering characteristics of a biaxial multirotor turbofan engine, a dynamic scattering method (DSM) based on dynamic simulation and grid transformation is presented, where the static RCS of the engine and its components is calculated by physical optics and physical theory of diffraction. The results show that the electromagnetic scattering of the engine is periodic when the engine is working stably, while the rotors such as fans and turbines are the main factors affecting the dynamic electromagnetic scattering and the ducts greatly increase the overall RCS level of the engine. The proposed DSM is effective and efficient for studying the dynamic electromagnetic scattering characteristic of the turbofan engine.

In this study, high-resistivity gold-implanted silicon substrates developed for radio frequency (RF) applications were characterized. By varying PICTS (Photo-Induced Current Transient Spectroscopy) measurement conditions such as the illumination wavelength, we identified the signature and the nature of four dominant traps. Two were electron traps and the others were hole traps. All of the related defects involved gold atoms. RF simulations of coplanar waveguide transmission lines integrated on these substrates were carried out, based on the trap properties extracted from PICTS results. A good agreement between RF experimental data and simulations was achieved by tuning the trap concentrations. Finally, the gold density extracted from the fit was successfully compared with the secondary ion mass spectrometry profile and an explanation of the role of the traps in RF behavior of the substrate was given.

A bistatic radar cross section (RCS) formulation is developed wherein a first-order physical theory (physical optics and physical theory of diffraction) is used. A large class of curved surfaces is considered using a single parameterization. These curved surfaces, combined with flat plates, can be used to model a variety of realistic shapes. Both the physical optics current and the edge equivalent current are placed on these shapes to radiate the scattered field. The resulting surface integral is evaluated with a uniform asymptotic approach by which a smooth transition from a monostatic local response to a response of distributed nature is devised. A carefully designed shadowing scheme is used to suit all scattering configurations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Physical optics (PO) and the physical theory of diffraction (PTD) are used to determine the backscatter cross sections of dihedral corner reflectors in the azimuthal plane for the vertical and horizontal polarizations. The analysis incorporates single, double, and triple reflections; single diffractions; and reflection-diffractions. Two techniques for analyzing these backscatter mechanisms are contrasted. In the first method, geometrical optics (GO) is used in place of physical optics at initial reflections to maintain the planar nature of the reflected wave and subsequently reduce the complexity of the analysis. The objective is to avoid any surface integrations which cannot be performed in closed form. This technique is popular because it is inherently simple and is readily amenable to computer solutions. In the second method, physical optics is used at nearly every reflection to maximize the accuracy of the PTD solution at the expense of a rapid increase in complexity. In this technique, many of the integrations cannot be easily performed, and numerical techniques must be utilized. However, this technique can yield significant improvements in accuracy. In this paper, the induced surface current densities and the resulting cross section patterns are illustrated for these two methods. Experimental measurements confirm the accuracy of the analytical calculations for dihedral corner reflectors with right, acute, and obtuse interior angles.

The physical optics (PO) and the physical theory of diffraction (PTD) are in extensive use in the antenna design and RCS calculation. The specific feature of these approximations is the phenomenon of polarization coupling. This phenomenon has been known since 1975, but its physical nature is still not explained in the literature. In the present communication, it is shown that this phenomenon is caused by the charges at the edge of a scattering structure, which are accumulated there due to the discontinuity of the PO current component normal to the edge.

Physical optics uses geometrical optics to estimate the surface current. This current is then used in a radiation integral to find the scattered field. PO often works very well for electrically large and smooth bodies. However, in spite of its great success in many applications, the use of an approximate current can lead to inherent limitations of its accuracy. The physical theory of diffraction (PTD) is an important high‐frequency technique that addresses this problem. The PTD became a widely used technique for the analysis and design of antennas, radar cross‐section analysis, and stealth design. The PTD theory is first developed in 2D. Its use is demonstrated by calculating the radiation pattern of a reflector antenna. It is then be generalized to 3D and applied to the scattering by a circular disc. The PTD formulation is closely related to both geometrical theory of diffraction (GTD) and uniform theory of diffraction (UTD).

Racal-Thorn Wells has developed the high frequency radar cross section (RCS) prediction code, FACETS (frequency asymptotic code for electromagnetic target scattering). This code relies on frequency asymptotic electromagnetic techniques, principally physical optics, physical theory of diffraction and geometric optics ray tracing. FACETS is the prediction code that sits at the heart of a suite of programs that make up the FACETS Electromagnetic Analysis System (FEMAS). FEMAS has been developed for translating CAD target surface descriptions into a form suitable for input to the FACETS analysis program and facilitating analysis of the results. The first section of this paper discusses the FACETS RCS prediction code and the second section gives examples of how this tool has been used in the collaborative venture between Racal-Thorn Wells and DERA Space Department, to produce simulated synthetic aperture radar (SAR) images of ships from spaceborne radar geometries. (5 pages)