A 400 GHz monolithic leaky wave antenna (LWA) is presented in this paper. The proposed LWA, constructed by the unit cell with multiple structural parameters, is regarded as the on-chip microstrip with perforation on the signal trace and the ground plane. A hybrid full-wave eigenvalue method theoretically extracts the complex propagation constants of first higher-order mode (EH1) of the perforated microstrip to improve the unit cell design. The extracted results also assist in realizing the differential feeding network to excite the leaky mode of the proposed antenna in high efficiency. A 400 GHz LWA prototype is designed and fabricated in CMOS 0.13 μm 1P8M process. The on-chip experiments show the measured input return loss including the effects of the contact pad lower than 10 dB from 380 GHz to 420 GHz. The measured antenna gain is higher than 0.8 dBi and has a maximum value of 1.3 dBi at 400 GHz. From 390 GHz to 405 GHz, the measured main beam is at 33° to 43° from broadside, indicating good agreement with the calculated results.

In this work, the dosimetry for two resonant modes of a highly resonant wireless power transfer (HR-WPT) system is investigated, and the results are compared. The physical mechanism of the two resonant modes, which occur when the two transmitting and receiving resonators are extremely close to one another, is presented with the simulated results and the equivalent circuit models for the HR-WPT system. The difference between the two resonant modes for the specific absorption rate induced in the head model is discussed by comparing the electromagnetic fields for each mode. Furthermore, the dosimetry for the four-coil HR-WPT system is also investigated under the conditions of a single resonant mode and two resonant modes. The specific absorption rates (SARs) are calculated with head-size and body-size simplified human models at various distances from the WPT system and in each mode. The electric and magnetic fields of the odd mode show stronger distribution than those of the even mode in the area near to the WPT system, while the opposite results are found in the area farther away.

Long-range wireless power transmission (WPT) is implemented with the phased array transmitter technology, which has been extensively applied in the field of the radar systems. The cost of a conventional phased array transmitter module scales up in proportion to the number of antenna elements, as the massive number of transmit channels results in the increasing complexity of hardware and feeding antenna elements. Besides, the conventional phase-shifting transmitter architecture has lower DC to RF power conversion efficiency due to the insertion loss of power combining network at microwave frequency. In this paper, the concept of spatial power combining transmitter is utilized, and the upconversion circuit is greatly simplified to an injection locked oscillator. Our WPT system is implemented with the technology of oscillator array antenna at 2.4 GHz, which converts DC power to RF power and radiates into the air directly. The feedback voltage controlled oscillator (VCO) is implemented as the microwave source using a off-the-shelf bandpass filter, and the external signal is injected to the oscillator via a microstrip coupler. {The oscillator core shows the DC-to-RF conversion efficiency of 45.87% with the injected power of 0 dBm at 2.4 GHz. Then the digital phase shifter is used to phase shifting the injected signal to extend the beam coverage. From the link budget analysis, the overall DC-to-DC efficiency of our highly-integrated system shows 1.5 times (0.22%) of the conventional phased array (0.15%) when the separation between the transmit array and the receive horn antenna is 1.2 meter. Therefore, as an modularized array, the proposed system demonstrates the promising capability of upscaling to an efficient massive array with greatly reduced bill-of-materials (BOM).

The long-term meteorological data of Era-interim from 1979 to 2014 covering the observation at 00, 06, 12 and 18 have been used to derive vertical refractivity gradient in the lowest 100. Diurnal, seasonal and annual variations of refractivity gradient and its component are analyzed for coastal and plateau areas of Nigeria. The relative frequency of the occurrence of gradient below -100 N-units/km used in clear air propagation study is derived from cumulative distribution of the gradient. Occurrence of anomalous propagation in each region is also estimated. The result will help in the effective wireless link planning and design.

This paper presents the analytical design and numerical performance evaluation of novel V-band millimetre-wave (mm-wave) beamforming networks (BFNs), based on the Rotman lens array feeding concept. The devices are intended for operation in the unlicensed 60-GHz frequency band. The primary objective of this work is to study the feasibility of designing flexible V-band beamformers, based on liquid-crystal polymer (LCP) substrates. The planar Rotman lens device has been initially developed, and the output performances, in terms of the scattering parameters and accuracy, have been analysed. This is further continued with the detailed designs of the Rotman lens BFNs based on the four different proposed flexural cases, namely the concave-axial bending, the convex-axial bending, the concave-circumferential bending, and the convex-circumferential bending. Each of the flexures has been analysed, and the performance in terms of the surface currents and phase distributions, as the primary functionality indicators, has been presented. The presented flexible beamformers exhibit significant characteristics to be potentially employed as low-cost and efficient units of the mm-wave transceivers with the in-built beam steering capabilities for the conformal wireless subsystems.

A beam-reconfigurable printed antenna on an Artificial Magnetic Conductor (AMC) is proposed for navigation and radiolocation applications at a frequency of 9.41 GHz. The AMC is formed based on a periodic Jerusalem cross shaped slot structure and is located in between two substrate layers, close to the radiator. The AMC plane has a bandwidth of 1.95 GHz around the targeted frequency of 9.41 GHz. By integrating micro-electro-mechanical system (MEMS) switches on the folded patches in combination with parasitic elements, a beam steering capability of up to ±58° is achieved with a rear full ground plane. This eliminates the need for a mechanical steering system, which is traditional in the applications targeted. The antenna achieves a high gain of 8.08 dB and 90% efficiency. A good agreement between simulated and measured results is obtained.

A topology, equations and design methodology for complex impedance-transforming branch-line hybrid couplers are presented. This method also allows the realization of real impedance-transforming to higher impedances. Limitations for real, imaginary and complex impedances are discussed. Test results are shown for a 3 dB 50 to 450 Ω hybrid coupler, at a 2 GHz center frequency, with a 21% bandwidth, an amplitude balance of 4.35±1 dB and a phase balance of 92.16°±8.8°. To showcase the complex impedance scenario, two 3 dB 50 Ω to 70-200j Ω are measured at a 2 GHz center frequency. One of these couplers uses a technique for reducing the chip size, yielding a 22.5% bandwith, 4-0.9 dB amplitude balance and 93.22°-6.74° phase balance, while acomplishing a 25% size reduction.

In this paper, a compact circularly polarized antenna based on a resonant quadrifilar spiral structure for the application of UHF RFID handheld reader is proposed and demonstrated experimentally. To reduce antenna size and improve impedance matching, the original resonant arms are revised by bending inverted-F structures and printing them on dielectric substrate, and the four arms are fed by a four-way phase shift network. Such an antenna indicates stable circular polarization performance and wide beam-width. The gain bandwidth (>2 dBi) can cover the frequency band from 902 MHz to 928 MHz, which is suitable for most of the popular UHF RFID system in the world. Moreover, the 1×4 array and 2×2 array based on previously demonstrated antenna unit are numerically investigated. The array performances, including the gain, beam scanning and low side-lobe are discussed.

A modified Koch fractal shape is used to decrease the dimensions of an antenna and resonates at more than one band for agricultural application. A new feeding technique of aperture coupled method called a non-uniform annular Photonic Band Gap is applied in order to integrate the designed antenna to the active elements. Subsequently, a transmission line transformer is designed using Genetic algorithm to achieve a perfect matching between the active element (amplifier) and the load (antenna). The proposed antenna is designed and fabricated. The results show that the proposed antenna has a high gain of 20.5 dB, 21 dB, and 22 dB at 0.915 GHz, 1.8 GHz and 2.45 GHz respectively with a compact size and low cost. The results predict its prospect as a promising alternative to the conventional one, which is compatibly applicable to agriculture applications especially when multiband function is required.

Based on the theory of Babinet's principle, a type of dual-polarized antenna working in C band with complementary structures is designed. The structures comprise a wire loop antenna and a slot loop antenna, which is complemented and fed by a coaxial line. A ground is placed to improve the front-to-back ratio of the antenna. The performance of the antenna is studied numerically and experimentally. A prototype antenna was built, stable and symmetric radiation patterns are obtained within the frequency of 4.9 GHz~5.1 GHz, and the port isolation is less than -24dB. The measured results coincide with the simulated ones. This explains the feasibility of the proposed dual-polarized antenna.

An electromagnetic interference (EMI) shielding material based on the composite of BaFe₁₂O₁₉, polyaniline (PANI) and multi-walled carbon nanotube (MWCNT) was proposed. The constituents of the composite were brought together through mechanical mixing and the in-situ polymerization of aniline on the BaFe₁₂O₁₉ and MWCNT surfaces. A series of composite with different MWCNT wt% loadings (0, 5, 10, 15, 20 and 25wt%) was prepared, and its effect on the EMI shielding performance was investigated. X-ray diffraction analysis was performed on all synthesized composites to confirm the phase formations. FESEM micrographs reveal the PANI particle formation on both BaFe₁₂O₁₉ and MWCNT surfaces. Electromagnetic measurements were done by using a rectangular waveguide connected to a network analyser to obtain the permeability, μ_r, permittivity, ε_r, and shielding effectiveness (SEA and SER). The increase in the MWCNT loading results in the enhancement of the composite's shielding performance to a certain limit. Optimum EMI shielding performance are shown by sample PBM4 (20wt% MWCNT) with SER and SEA values of 5.14 dB at 8.2 GHz and 36.41 dB at 12.4 GHz, respectively. influence of different MWCNT loadings (0, 5, 10, 15, 20 and 25wt%) on the EMI shielding performance of a composite consisting of BaFe₁₂O₁₉, polyaniline (PANI) and multi-walled carbon nanotube (MWCNT) were investigated.

A novel 1.8 GHz compact microstrip low-pass filter (LPF) based on quasi-yagi defected ground structure (DGS) and compensated capacitors is proposed in this paper. The filter has a very sharp cut-off frequency response with low insertion loss and achieves a wide reject band with overall 20 dB attenuation from 2.8 GHz up to 10 GHz. The equivalent circuit model of Yagi-DGS-unit is derived using AWR software, and the circuit parameters are extracted by using a simple circuit analysis method. The advantage of this structure is that the reject band can be controlled by tuning the dimension of Yagi-arms at higher frequency rang. The proposed 1.8 low-pass filter is designed using microwave office electromagnetic software and fabricated on the RO4003 ceramic structure with dielectric constant of 3.38. The compact filter occupies an area of (0.45λ_g × 0.35λ_g) with λ_g = 44 mm. A comparison between simulation and measurement results confirms the validity of the LPF configuration and design procedure. In order to improve the compactness of the proposed LPF, a new multi-layer method has been employed. Finally, a new minimized LPF-topology 50% more compact than the conventional is realized.

This paper proposes a compact Radial Line Slot Array (RLSA) antenna for 5.8 GHz Wi-Fi devices, which meets market needs. Various small RLSA antenna models with radius of 140 mm, were designed using extreme beamsquint technique. The models then were simulated to result in a best model. A prototype of the best model was then fabricated and measured to verify the simulation. The measured parameters are: a gain of 18 dBi, bandwidth of 1 GHz, beamwidth of 20˚, and mainlobe to sidelobe ratio of 15 dB, which meet antenna specifications for market needs. The prototype was tested as an antenna for a Wireless Fidelity (Wi-Fi) device in order to show its performance. The test showed that the prototype worked properly. Lastly, we compared the size of the prototype with the average size of various antennas available in markets. We found that the prototype had the advantage of small size and flat, with similar performance.

In this work linear random arrays are studied. It is shown that random symmetric linear arrays can be more easily characterised (with respect to the asymmetric ones) in terms of the first and second order statistics of the array factor magnitude. In particular, the non-stationarity of the array factor can be taken into account while studying the array response. Accordingly, this leads to more accurate predictions as far as the side-lobe level is concerned.

Effective electromagnetic parameters (EEPs) of periodic structures fabricated mainly by carbonyl iron powders are calculated in this paper. A method of inverting the scattering parameters obtained from simulation software was used. The effect of the absorbent volume ratio and the cycle length on EEPs was studied and analyzed. The correlation of the shapes with EEPs was also researched. The empirical formulas were proposed to calculate EEPs, in which the interaction between two adjacent cells was considered. By using this method, any material could be designed as a periodic structure with controlled EEPs, and the values of EEPs were located between the electromagnetic parameter (EP) of air and that of the original material by a specific rule. The EEPs can be used to design new absorbers as the fundamental data of electromagnetic property of some fresh materials.

The concept of virtual experiments is based on the idea of solving the inverse scattering problem by processing a suitable recombination of the available data, instead of those arising from the measurements. By properly designing such experiments (and without additional measurements), it is possible to enforce some peculiar field's or contrast source's properties, which can be helpful to perform the inversion in a more simple and reliable way. In this paper, we show that the factorization method can be used as a tool to design the virtual experiments. In doing so, we also provide, for the first time, an insight into its physical meaning. As an example, we exploit the virtual experiments designed via FM as the backbone of a linearized inversion approach for quantitative imaging of non-weak targets.

The paper introduces a new method for eliminating multiple-time-around detections in coherent pulsed radar systems with single constant pulse repetition frequency. The method includes the phase modulation of transmit pulses and corresponding phase demodulation at reception, which is matched to signals from the unambiguous range interval, and subsequent coherent integration followed by successive CFAR processing in range and Doppler domains. The performance of the proposed method is studied by means of statistical simulations. It is shown that the elimination performance can be essentially improved by optimizing the transmit phase modulation code. The optimization problem is formulated in terms of least-square fitting the power spectra of multiple-time-around target signals to a uniform power spectrum. Several optimum biphase codes are designed and used in the performance analysis. The analysis shows that the method can provide very high probability of elimination without noticeable degradation in the detection performance for targets from the unambiguous range interval.

This study is focused on how to obtain the effective or equivalent properties of inhomogeneous materials, which, contrary to the usual metamaterials, are assumed to possess only a sandwichlike form of heterogeneity. More specifically, the aim is to see how the method of inversion, and associated type and amount of data, condition the outcome of the inversion, notably as concerns the possibility or not of exotic features such as simultaneous negative permittivity and permeability in certain frequency intervals. Two inversion schemes are considered and compared: the Nicolson-Ross-Weir (NRW) scheme and an optimization scheme. The adopted form of the optimization scheme provides only numerical retrievals, but it applies to any number of far-field data couples, which fact makes it a useful tool for determining whether the retrieved properties of an inhomogeneous material really are independent of the angle of incidence as is required for effective properties. It is shown, via the optimization scheme, that the apparently infinite number of solutions predicted by the NRW scheme is reduced to a single solution-closest to the predictions of a mixture model-when the constraint of independence with respect to angle of incidence is invoked. Moreover, this solution exhibits none of the exotic features of the properties of the usual metamaterials except temporal dispersion and loss even when the component materials of the inhomogeneous layer are neither dispersive nor lossy.

Brain stroke incidences have arisen at an alarming rate over the past few decades. These strokes are not only life threatening, but also bring with them a very poor prognosis. There is a need to investigate the onset of stroke symptoms in a matter of few hours by the doctor. To address this, Electromagnetic Impedance Tomography (EMIT) employing microwave imaging technique is an emerging, cost-effective and portable brain stroke diagnostic modality. It has the potential for rapid stroke detection, classification and continuous brain monitoring. EMIT can supplement current brain imaging and diagnostic tools (CT, MRI or PET) due to its safe, non-ionizing and non-invasive features. It relies on the significant contrast between dielectric properties of the normal and abnormal brain tissues. In this paper, a comparison of microwave signals scattering from an anatomically realistic human head model in the presence and absence of brain stroke is presented. The head model also incorporates the heterogenic and frequency-dispersive behavior of brain tissues for the simulation setup. To study the interaction between microwave signals and the multilayer structure of head, a forward model has been formulated and evaluated using Finite Element Method (FEM). Specific Absorption Rate (SAR) analysis is also performed to comply with safety limits of the transmitted signals for minimum ionizing effects to brain tissues, while ensuring maximum signal penetration into the head.

As important fundamental equipment, high voltage switchgears are widely used in electric power systems and directly relative to the power reliability and quality. Partial discharge (PD) online monitoring is one of the most effective methods used for insulation testing and diagnosis in high voltage switchgears and power systems. This paper proposes a unique ultra-wide-band (UWB) antenna with high performance for PD ultra-high-frequency (UHF) detection in high voltage switchgears. Actual PD experiments were carried out, and the designed antenna was used for PD measurements. The measured results demonstrate that the proposed antenna has wide work frequency band, good omnidirectional radiation patterns and appreciable gain, which indicate that the proposed antenna is suitable for UHF online monitoring of PDs in high voltage switchgears.