Non-Foster matching circuits are those that can function as negative capacitors or inductors, and can thus overcome the gain bandwidth limitation of passive matching circuits for antennas. This paper presents a non-Foster matching circuit (NFC) for a very low frequency (VLF) receiver loop antenna. The bandwidth of the antenna was improved by 383%, and the average gain was improved in most bands compared to a passive matching circuit (over 15-30 kHz). In contrast to circuits reported in other publications, the signal to noise ratio (SNR) of the passive matching network performed better than the non-Foster matching network. To analyze this phenomenon, a noise model was developed for the simplified balanced NFC, and noise analysis was conducted between the non-Foster and passive matching networks, which indicates that the non-Foster matching circuits cannot provide a better SNR performance than the passive matching circuits under low noise figure level receiver conditions.

This paper reviews recent advances in the design of low noise amplifier (LNA) in complementary metal oxide semiconductor (CMOS) technology for radio transceivers at microwave and millimeter wave (mmWave) frequencies. First, the evolution of wireless communication systems and CMOS technology are briefly revisited to highlight the requirements of an LNA design. Then, key performance parameters and device circuit models are described. Next, we discuss typical LNA topologies, followed by those important design techniques, algorithms and concepts developed specifically for CMOS LNAs. Moreover, reported CMOS LNA designs are summarized, and future design issues are identified. Finally, we conclude the paper and briefly outline our future work on CMOS LNA designs.

This paper discusses the in fluence of simplifications in models used in the design of electromagnetic protection against indirect effects of lightning strikes. A real and complex test case such as the power plant of an A400M aircraft, simulated with the FDTD method, is chosen for this. The parameters studied are the inclusion/removal of installations, modification of electrical contacts, material properties, and changes in the cable characteristics. The simulations performed allow us to quantify the impact of different simplification approaches and, in consequence, to draw conclusions on the relative importance of different model features, being the most important ones to maintain the electrical contacts, to include installations and cables carrying high currents, to consider different materials, to respect the accurate cable routes or to take care of isolated equipment.

Design, simulation, implementation and measurement results of multiline and multilayer microstrip directional couplers are given with closed form relations. Step-by-step design procedure reflecting the design practice of directional couplers, which requires only information on coupling level, port impedances and operational frequency, is presented. The method based on the synthesis technique applied in the design of conventional two-line microstrip symmetrical directional couplers is adapted to design multilayer directional couplers with the aid of electromagnetic simulators using parametric analysis with curve fitting method. The proposed design method is compared with the measurement results and accuracy is verified. It has been also shown that the directivity of the couplers designed using the multilayer structure is improved significantly. A method such as the one presented in this paper can be used to design multilayer two-line and three-line directional couplers which can be integrated to the front end of an RFID systems to provide the required isolation between transmitter and receiver and prevent signal leakage due to use of conventional circulators.

In this paper, a novel compact hexagonal shaped ultra-wideband multiple-input multiple-output (UWB-MIMO) Koch fractal antenna is designed with penta-band rejection characteristics for portable devices. The antenna rejects the C-band downlink frequency from 3.7-4 GHz, the C-band uplink frequency from 5.75-6.05 GHz and the satellite bands from 7.45 to 8.4 GHz. The band 7.45-7.55 GHz is used by the meteorological satellite service for the geostationary satellite services. The band 7.75-7.9 GHz is used by the meteorological satellite service for non-geostationary satellite services. The band 8.025-8.4 GHz is used by the Earth exploration satellites for geostationary satellite services. The C-band and satellite bands interfere with the UWB and have been rejected using a band reject filter. A spiral shaped slot is introduced inside the fractal hexagonal monopole to introduce band reject characteristics. The band suppression and widening of the impedance bandwidth are achieved by using defected ground structures. The antenna has wideband impedance matching with S₁₁ < -10 dB in the UWB frequency range from 3.1 to 13.6 GHz and has a low mutual coupling with S₂₁ < -19 dB. The antenna has very low envelope correlation coefficient of less than 0.17 and low capacity loss of 0.254, which proves that the MIMO antenna shows good diversity performance.

The block diagram of a TR (Transmit Receive) module that consists of four channels using a silicon substrate is presented in this paper. The silicon substrate fabricated by microelectronic process has been adopted to increase the interconnect density of module. Several broadband vertical transitions are simulated and optimized by EM simulator. The vertical transition works well from DC to 40 GHz. The insertion loss is less than 1 dB, and the return loss is better than -15 dB in back-to-back configuration. A novel TR module based on the silicon substrate is proposed for its miniaturization and high integration advantages. The module occupies a compact area of 30 mm×20 mm×1.8 mm, and the weight is 1.77 g.

This paper reviews the motion of a charged particle in the electrostatic field of two coaxial likely charged rings located at some distance from one another. The charges of rings and that of the particle are of the same sign. Initial conditions of motion of the particle relatively to the rings under which the particle overcomes the electrostatic repulsion of rings and localises along a particular circular trajectory laying in the internal space between the rings were determined.

In this paper, a channel characterization of an RF link using circularly polarized antennas inside a mine is performed. The association of circular polarization with multiple-input-multiple-output (MIMO) radio technologies represents a powerful tool to improve the performance of an underground RF channel. The statistical parameters of the channel are derived from in-mine measurements at the 2.4 GHz band for both co-polarization (CP) and cross-polarization (XP) scenarios. Results show a remarkable improvement through the use of MIMO combined with circular polarization compared to the regular patch MIMO antenna system, in terms of channel capacity and path loss. This improvement increases significantly at the XP scenarios, reaching up to 18 bps/Hz for channel capacity and up to 21 dB for path loss. The RMS delay spread for a circularly polarized setup is generally higher than the linearly polarized MIMO patch setup due to surface roughness of the gallery. In the linear polarization case, a signal degradation of more than 15 dB at the XP case is observed compared to the CP scenario. This signal loss that is due to depolarization is somewhat mitigated by the surface roughness.Due to its superior and stable performance, MIMO combined with circular polarization is better suited than a regular MIMO patch system for in-mine uses, especially in the applications where the transmitter may change direction with respect to the receiver.

Carbon fiber reinforced polymer (CFRP) is measured as reflector material for millimeter waves at 60 GHz. Reflectivity is measured to characterize material anisotropy in a mono-static setup. Disc shaped material samples are rotated in steps of one degree. Four commonly employed CFRP are investigated: unidirectional fibers, plain-weave, twill-weave and fiber shreds. Results show that the unidirectional CFRP and twill-weave CFRP are anisotropic, while the remaining materials are isotropic within measurement accuracy.

In this paper, a beam switchable antenna solution for vehicular use is presented. Main objective is to improve the cellular connectivity of vehicles operating in poor coverage region. An adaptive antenna system operating in the frequency band 824-960 MHz having high gain, and full azimuth plane coverage, and main beam in elevation plane pointing towards 90˚, was developed. Beam switchable antenna provides beam-steering in azimuth plane, by switching one antenna element active at a time. The concept of stacked patch antenna with L probe feed was used for a single element. This arrangement gives gain of 7.4-8.2 dBi, and total radiation eciency of 0.11 dB, over the band, with broadside radiation pattern, and half power beam width of single element up to 80˚. The field measurements for the designed antenna system were performed in poor coverage regions using commercial cellular network. Results were compared to corresponding results of conventional vehicular antenna, having omnidirectional radiation pattern and the gain of 3 dBi. The developed antenna system results in 3.5...12.7 dB higher RX level than reference antenna and increase communication range from 71 km to 109 km in open area. Similarly, in suburban area the communication range is increased from 20 km to 30.8 km. Also, the narrower beam acts as spatial filter and results in reduced fading.

This paper presents the applicability of cavity modeling technique to analyze field propagation inside a multiport waveguide network. For a better understanding of the subject, we have considered a five-port quadraplexer as our target network. Field propagations within the network at different passband and stopband frequencies have been presented. The analysis has been verified by comparing the overall frequency response of the network with the available data in literature. The analysis demonstrates the field division at different junctions as well as field attenuation/propagation at different points of the network, which will be helpful for designing more complex and/or advanced multiport waveguide networks. It also demonstrates the presence of higher order modes at different discontinuities of the network and their effectson the respective field distributions.

A three-section branch-line coupler is miniaturized using diamond-series stubs microstrip lines. The modified coupler is capable of operating from 1.6 GHz to 3 GHz with a return loss of less than -20 dB, phase imbalance of less than 2.5°, insertion loss and coupling of 4.5 dB and 3.02 dB, respectively. The bandwidth of the coupler has been extended up to 1.4 GHz. In addition, it achieves up to 84% size reduction as compared to a conventional three-section coupler. Furthermore, its performance and circuit size were compared with another modified coupler with normal open-stubs microstrip lines. Effects of the diamond structure and number of stubs were analyzed and discussed in detail, Furthermore, the results achieved by this study are superior to the previous studies.

A new single-layer element structure for broadband operation is presented. The element is composed of a circular ring attached two sets of phase-delay lines with the opposite direction of rotation. The demission of circular ring is fixed, and about 460° reflection phase range is achieved by varying the length of the phase-delay lines. Using the proposed element, a 381-element single-layer linearly polarized reflectarray is designed, fabricated and measured. A gain of 27.5 dB is measured at 13.58 GHz with 3-dB beamwidth of about 6.8°, and the corresponding aperture efficiency is 57.3%. Good radiation performances are also achieved at other frequencies. Measured results show 1.5-dB and 3-dB gain bandwidth of 47.8% (13.58-20.08 GHz) and 64% (12.08-20.78 GHz) with the center frequency of 13.58 GHz respectively, which demonstrates excellent broadband performance. Besides, high aperture efficiencies (more than 50%) are achieved in a wide frequency range (12.08-17.08 GHz). Low cross polarization and sidelobe levels are also achieved in the frequency band.

A process is introduced to design and validate insertable rectangular-waveguide verification standards for the electromagnetic characterization of materials using the Nicolson-Ross-Weir method. Each insertable structure consists of a series of metal steps that acts as a surrogate material exhibiting smooth and predictable permittivity and permeability characteristics across the waveguide band. These known material properties can be used to assess the performance of material characterization systems. Since the verification standards are inserted into the waveguide in the same manner as samples under test, each step in the normal measurement procedure is duplicated. A specific example of an S-band verification standard is presented, with the standard fabricated using two different methods. The first standard is machined from a solid metal block while the second is constructed by metalizing a 3-D printed polymer structure. Comparison of the predicted material parameters to those extracted from experimental data demonstrates the utility of the proposed insertable standards.

A front-end module (FEM) consisting of a single-pole-double-throw (SPDT) switch and a low noise amplifier (LNA) with good performance is proposed. The SPDT switch is based on PIN diodes, which are mounted on impedance transforming lines parallelled to the main transmission lines with an asymmetric topology. This asymmetric topology is utilized to achieve low insertion loss and high transmit-to-receive isolation. The interstage matching of switch and LNA is designed to achieve low noise figure. To validate the design, the FEM is simulated, fabricated and measured. The experiment results show that, within the range of 7.8-8.1 GHz, the FEM achieves a gain of 22 dB and noise figure of 1.9 dB in receiving mode, with an insertion loss of 0.9 dB and isolation of 40 dB in transmitting mode. In addition, the FEM can handle up to 4 W transmitting power at 8 GHz with good linearity.

A new direction finding method for multiple-input multiple-output (MIMO) radar with non-circular sources is proposed. The method takes advantage of the properties of non-circular sources to formulate a new virtual array. Then based on the ESPRIT like algorithm, the bearing of targets is estimated. In addition, the direction of departure (DOD) and direction of arrival (DOA) are paired automatically. Compared with the uniform circular array estimation of signal parameters by rotational invariance techniques (UCA-ESPRIT), the proposed method achieves better estimation performance and can deal with more sources. We also provide the Cramer-Rao Lower Bound (CRLB) for comparison. Simulation results demonstrate the effectiveness and feasibility of the proposed method.

Aircraft collision avoidance system is an airborne system which is designed to provide the service as a last defense equipment for avoiding mid-air collisions between aircraft. End-fired antenna is suitable to be used in such airborne systems where low aerodynamic drag is urgently required. An effort to develop such an antenna using dipole elements is presented in this paper. Here a unit element planar folded dipole antenna is presented which radiates in the end-fire direction. Split ring resonators inspired artificial materials are incorporated in the design to improve the directivity performance of the proposed antenna, and those materials are loaded in the same plane of the primary dipole radiator. Here suppression of surface wave in the antenna takes place, which results in gain enhancement and also reduction of side lobes which make radiation pattern better. All these proposed antennas are designed and simulated in CST Microwave Studio (MWS) EM tool which is based on time domain solver. The performance and other antenna characteristics have been explored from the simulation results followed by the antenna fabrication and measurement. Quite good agreement is achieved between the simulated and measured results. Much better performance characteristics make this proposed antenna a good candidate for this application.

Predicting signal power loss between the transmitter and receiver with minimal error is an important issue in telecommunication network planning and optimization process. In recent years, median order statistic filters have been exploited as a preprocessing constituent for analyzing signals. This work presents a resourceful predictive model, built on multi-layer perceptron (MLP) network with vector order statistic filter based preprocessing technique for improved prediction of measured signal power loss in a microcellular LTE network environment. The predictive model is termed Vector statistic filters multilayer perceptron (VSF-MLP). In terms of some essential performance evaluation indices such as the correlation coefficient, root-mean-square error and coefficient of efficiency, results show that VSF-MLP model prediction performs considerably better than the standard MLP model prediction approach on signal power data collected from different study locations in typical urban terrain.

Due to changes in global security requirements attention is turning to new means by which anomalies on the human body might be identified. For security screening systems operating in the millimeter wave band anomalies can be identified by measuring the emissivities of subjects. As the interaction of millimeter waves with the human body is only a fraction of a millimeter into the skin and clothing has a small, but known effect, precise measurement of the emission and reflection of this radiation will allow comparisons with the norm for that region of the body and person category. A technique to measure the human skin emissivity in vivo over the frequency band 80 GHz to 100 GHz is developed and described. The mean emissivity values of the skin of a sample of 60 healthy participants (36 males and 24 females) measured using a 90 GHz calibrated radiometer was found to range from 0.17±0.005 to 0.68±0.005. The lower values of emissivity are a result of measuring particularly thin skin on the inner wrist, volar side of the forearm, and back of hand, whereas higher values of emissivity are results of measuring thick skin on the outer wrist, dorsal surface of the forearm, and palm of hand. The mean differences in the emissivity between Asian and European male participants were calculated to be in the range of 0.04 to 0.11 over all measurement locations. Experimental measurements of the emissivity for male and female participants having normal and high body mass index indicate that the mean differences in the emissivity are in the range of 0.05 to 0.15 for all measurement locations. These results show the quantitative variations in the skin emissivity between locations, gender, and individuals. The mean differences in the emissivity values between dry and wet skin on the palm of hand and back of hand regions were found to be 0.143 and 0.066 respectively. These results confirm that radiometry can, as a non-contact method, identify surfaces attached to the human skin in tens of seconds. These results indicate a route to machine anomaly detection that may increase the through-put speed, the detection probabilities and reduce the false alarm rates in security screening portals.

In this work, a new technique in suppressing the effect of four-wave mixing (FWM) by Odd-Even Channels Arrangement (OEC) is presented. The proposed technique is verified mathematically and by simulations with other recent techniques which are input power and channel spacing under the same input parameters. Simulation was done with the power variation effect, and the bit rate was 100 Gb\s. Based on theoretical and simulation analyses, FWM power was drastically reduced by more than 10 dB when OEC was conducted. In terms of system performance, OEC offered better performance than previous techniques in both theoretical and simulation analyses.