New Global Navigation Satellite System (GNSS) systems under development, such as Galileo, are very promising for future global positioning-based applications. A vast research is undergoing a final stage of implementation in order to fulfill the primary purpose of European Space Agency for developing and then sustaining of 30 (27 + 3 spares) Galileo satellites in orbit. This article presents simulation results for a realistic deployment of multibeam antennas, with a new modified theoretical pattern, in GNSS Satellite Systems. The proposed multibeam antennas use 61-spot beams for maximum efficiency in terms of satellite coverage and accessing high quality of service. In order to prove the reliability and feasibility of this work, various simulations were conducted using the upcoming Galileo system as a platform taking into consideration real-world conditions. Gain analysis versus elevation, Bit Error Rate (BER) and access time simulation results show that the viability of the proposed multibeam antenna deployment is established.

The paper presents the first attempt to develop parameters that are invariant to polarization, aimed at classification and recognition of complex radar objects. Both the simplest (two-point) model and multipoint models of a complex object are analyzed using the so-called emergence principle and a generalization of the interference laws. The polarization invariant parameters of scattered fields and their statistical parameters, including autocorrelation functions and space spectra, are found. The experimental validation of the analysis results is presented.

This paper presents a frequency-modulated continuous-wave (FMCW) radar operating at 120 GHz, which features silicon–germanium (SiGe) chips that employ HBTs with 320 GHz fmax. The chipset comprises a fundamental-wave signal-generation chip with a voltage-controlled oscillator (VCO) that provides frequencies between 114 and 130 GHz and a corresponding dual–transceiver (TRX) chip that supports monostatic and quasi-monostatic radar configurations. The cascode amplifiers used in the TRX chip were characterized in separate test chips and yielded peak small-signal gains of approximately 15 dB. Finally, a quasi-monostatic two-channel FMCW radar frontend with on-board differential microstrip antennas was built on an RF substrate. FMCW radar measurements with frequency chirps from 116 to 123 GHz verified the functionality of the designed radar sensor.

In this paper, the far-field pattern of a Cassegrain reflector is formulated. A novel illumination function is used to approximate the field distribution at the aperture of the reflector. The defined illumination function takes into account the central aperture blockage created by the subreflector. Using the illumination function, a closed-form expression describing the far-field radiation pattern of the Cassegrain reflector is formulated. The radiation pattern obtained from the derived equation is compared with the results obtained from physical optics and physical theory of diffraction. The results are found to be consistent with each other. It is found that the derived results show an impressive accuracy of 99.8% over the main-lobe region. The accuracy is found to be over 91 and 84% for the first and second significant side-lobe region, respectively, which can be considered satisfactory for many applications.

A simple and efficient numerical inversion Laplace transform (NILT) algorithm is implemented in MATLAB environment based on the quotient difference method to solve the problem of electromagnetic (EM) field coupling to lossy or lossless multi-conductor transmission lines (MTL) illuminated by an EM incident field. Two major points are treated in this work for the lossy MTL system excited by an incident EM field; the first one is the optimum equivalent circuit taking into consideration the different physical concepts based on the transmission line theory and the second point deals with the choice and implementation of the numerical method for less computing time and for efficient results. In this paper, the effect of the EM coupling is treated and it is based on the superposition effect of each distributed voltage current sources using the NILT numerical method. Results of the near end and far end voltages and currents for an MTL system are presented and displayed for two types of microwave (MW) structures in the time domain for the case of a plane wave excitation. It has been shown that a non-homogeneous MW structure or multilayered system with a specific choice of the dielectric constant has an advantage for less transient EM coupling due to the external EM field.

ADS-B provides convenient means of air traffic control (ATC) for its low cost and simple ground station hardware. In a low percentage of cases, aircraft positions transmitted via ADS-B are error prone due to e.g. faulty wiring with onboard navigation systems. In the proposed approach, direction of arrival (DOA) estimation is used to verify ADS-B airborne positions. The potential positioning error of ADS-B is thereby evaluated by comparing DOA estimates to DOA values calculated from ADS-B references and the sensor position and orientation. To prove the accuracy of the applied DOA estimation sensor, an additional measurement campaign using a dedicated measurement aircraft has been conducted.

In the present study, the essential oil from the leaves of River Red Gum (Eucalyptus camaldulensis Dehnh) was distilled by microwave applied in situ hydrodistillation (MWHD) and the properties obtained were compared with hydrodistillation (HD) techniques. The chemical composition of essential oil obtained by the microwave method was analyzed by gas chromatography (GC) and GC–mass spectrometry (MS). The results showed that the essential oil from E. camaldulensis could successfully be distilled by using microwave irradiation power. Microwave power has been supplied from a cavity having a multimode microwave reactor 2455 MHz with a maximum power of 1000 W. Electromagnetic power distribution has been analyzed inside the cavity. The yield of essential oil increased with increasing microwave irradiation power. It was also found that the content of main compounds clearly varied according to methods applied. However, the yield of essential oil determined by MWHD was slightly lower than that of conventional HD method at conditions studied.

The possibility to characterize infinite and periodic frequency-selective surfaces (FSS) filters that have two orthogonal axes of symmetry inside a waveguide is reported. Thus, preliminary measurements can rapidly be obtained at low cost with few elementary cells instead of using a large FSS panel in free space. This is possible because of the equivalence that exists between the electromagnetic fields of two symmetric and oblique plane waves incident on and reflected from an infinite periodic surface and the incident/reflected fields that exist inside a single-mode rectangular waveguide containing a finite number of elementary cells. Comparisons of the measurements with some full-wave simulations for FSS belonging to the first three groups as they were defined by Munk confirm the good agreement between them. This is an interesting and simple assessment tool concerning the fabrication quality of FSS. The extension of this technique to non-symmetric FSS patterns is also discussed and supported by experimental and simulation results. The limitations of the technique are finally discussed.

In this study, we present the implementation of invasive weed optimization (IWO) in the maximization of main-lobe to side-lobe level for the non-uniform planar antenna array. The antenna arrays investigated in this study are generated using the chaos game algorithm (CGA) and shaped into selected fractal geometries chosen on the basis of their interesting performance. This CGA is picked out in order to overcome the limitations found in the fractal arrays. All the attained results are compared with the results produced by a well-known optimization algorithm that is the particle swarm optimization (PSO). In all the optimized arrays, IWO shows superior optimization results compared with PSO.

The radiofrequency (RF) system of the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory is a resonant system based on the quarter-wave cantilever-type resonating structure. Power is fed to the Dee from the anode of the 500 kW RCA 4648 tetrode tube operating in grounded cathode configuration, which is coupled to the side of the Dee stem. The tube is obsolete and makes its continued use impractical. A new final power amplifier was designed and built using the commercially available tube Eimac 4W150,000E. The new amplifier was successfully commissioned and has been reliable and easy to operate.

The paper is a joint work between the LEAT (France) and the ENRI (Japan) in the framework of a Sakura project supported by the JSPS and the French Ministry of Foreign Affairs. The purpose is the study of a FOD (Foreign Object Debris) detection system on airport runways. An FM-CW mm-wave radar working between 76.25 and 76.75 GHz is used together with a high directivity printed reflectarray. In addition, a second measurement campaign has been conducted with a 73.8–79.8 GHz (6 GHz band) radar. Measurement results show detection capabilities of a −20 dBsm cylinder up to 35 m that is 10 m less than the FAA recommendations. Antenna improvements are discussed for reaching the requirements and system performance as well as the use of calibration objects.

This paper describes an automatic-dependent surveillance–broadcast (ADS–B) implementation for air-to-air and ground-based experimental surveillance within a prototype of a fully automated air traffic management (ATM) system, under a trajectory-based-operations paradigm. The system is built using an air-inclusive implementation of system wide information management (SWIM). This work describes the relations between airborne and ground surveillance (SURGND), the prototype surveillance systems, and their algorithms. System's performance is analyzed with simulated and real data. Results show that the proposed ADS–B implementation can fulfill the most demanding surveillance accuracy requirements.

The mm-wave as well as avalanche noise properties of IMPATT diode at D-band are efficiently estimated, with different poly-types of silicon carbide (SiC) and GaN as base materials, using advanced computer simulation techniques developed by the authors. The breakdown voltage of 4H-SiC (180 V) is more than the same for 6H-SiC, ZB- and Wz-GaN-based diode of 170,158, and 160 V, respectively. Similarly, the efficiency (14.7%) is also high in the case of 4H-SiC as compared with 6H-SiC and GaN-based diode. The study indicates that 4H-SiC IMPATT diode is capable of generating high RF power of about 8.38 W as compared with GaN IMPATT diode due to high breakdown voltage and negative resistance for the same frequency of operation. It is also observed that Wz-GaN exhibits better noise behavior 7.4 × 10−16 V2 s than SiC (5.16 × 10−15 V2 s) for IMPATT operation at 140 GHz. A comparison between the power output and noise from both the device reveals that Wz-GaN would be a suitable base material for high-power application of IMPATT diode with moderate noise.

We propose in this paper a 4-channel time-domain test bench for the characterization and linearity enhancement of microwave power amplifiers (PAs). The proposed time-domain measurement system utilizes four track and hold amplifiers (THAs) for direct subsampling of radiofrequency (RF) signals. The use of wideband THAs to replace samplers or mixers enables reducing analog IF circuit complexity. It permits direct digitization of RF signals like CW, two-tone and pulsed modulated signals, bringing more flexibility in the receiver's performance by enhancing the dynamic range and bandwidth. This test bench is capable of completely extracting the phase, amplitude, and transfer characteristics of non-linear devices excited with CW or modulated RF signals. In this work, two-tone transfer characteristics of a 50 W GaN HEMT Nitronex PA were extracted and processed for applying digital pre-distortion linearization to enhance linearity performance. Time-domain envelope and carrier waveforms (voltage and current) along with third-order inter-modulation distortion (IMD) products with and without digital pre-distortion scheme are also presented.

This paper introduces a radar system for three-dimensional (3D) object detection and imaging. The presented 3D measurement method combines the frequency-modulated continuous wave (FMCW) approach for range measurements with a multiple-input multiple-output (MIMO) technique for digital beamforming in two dimensions. With an orthogonal arrangement of the antenna arrays for transmit and receive, the angular information is obtained in azimuth and elevation without mechanical beamsteering. The proposed principle allows performing 3D imaging by means of the acquired range, azimuth, and elevation information with a minimum of required hardware. Starting from the realization of the 3D radar imaging concept, the hardware architecture and the developed prototype are discussed in detail. Furthermore, the object detection capability of the 3D imaging radar system is demonstrated by measurements. The results show that the introduced 3D measurement concept in its realization is well suited for numerous applications.

Since Hodgkin and Huxley described the nerve axon as a cable (H–H model), many efforts have been made to find more approximated transmission line models representing the nerve axon. This paper describes a simple model that represents the nerve axon in two parts: the internodal space as a lossy thin-film microstrip line and the node of Ranvier as an active complex load. The complex load terminating the transmission line is given by the variable impedance of a tunnel diode. First, the internodal space is circuitally analyzed and electromagnetically simulated as a lossy thin-film microstrip line terminated on a complex fixed load. The transmission line circuit theory, the two-port network analysis, and a two-dimensional finite difference time domain method are used for such a task by forcing a strip subatomic metallization. Then, the transfer function of the internodal space, cascaded with the node of Ranvier, is equated to the transfer function of a transmission line section that includes a tunnel diode. This procedure is carried out in order to obtain the diode's variable impedance. The diode was introduced by Nagumo, Arimoto, and Yoshizawa for simulating the nerve axon as an active transmission line. The active transmission line is represented by the FitzHugh simplified H–H model known as the Bonhoeffer–van der Pol model.

LInear amplification using Non-linear Components (LINC) is an architecture that achieves linear power amplification for radio-frequency (RF) transmitters. This paper describes the impact of RF power amplifiers (PAs) class on the overall system performances. The linearity and efficiency of the LINC transmitter with different PA classes (AB, B, C, D, E, F, F−1, and J) are evaluated and compared, in terms of error vector magnitude (EVM), adjacent channel leakage ratio (ACLR), and power added efficiency (PAE), for a 16QAM modulation having 5.6 dB peak to average power ratio. Simulations are performed using a gallium-nitride high electron mobility transistor (GaN HEMT) for a power amplifier with an output power of 10 W at 900 MHz.

In this paper, an effective procedure to emplace standard and enhanced mode-S multilateration stations for airport surveillance is studied and developed. This procedure is based on meta-heuristic optimization techniques, such as genetic algorithm (GA), and is intended to obtain useful parameters for an optimal system configuration that provides acceptable performance levels. Furthermore, the procedure developed here is able to evaluate and improve previous system designs, as well as possible system enhancements. Additionally, the design strategies to be used along with the procedure proposed here are fully described. Parameters such as the number of stations, the system geometry, the kind of measurements to be used, and the system accuracy are obtained taking into account the basic requirements such as the Line of Sight, the probability of detection, and the accuracy levels.