With the increase of low power devices, the design of a compact and efficient rectenna is essential for supplying energy to the devices. This paper presents a compact rectenna for high efficient WiFi energy harvesting. A novel fractal geometry is introduced in the design of antenna for miniaturization, and the ability to harvest WiFi energy is enhanced due to its characteristics of self-similarity and space filling. Besides, a single stub matching network is designed to achieve high conversion efficiency with a relatively low input power ranging from -20 dBm to 0 dBm. Simulation and experiments have been carried out. The results show that the proposed antenna features a good characteristic of reflection coefficient and realized gain at WiFi band. The highest RF to DC conversion efficiency of the rectenna is up to 52% at 2.48 GHz with the input power of 0 dBm. This study demonstrates that the proposed rectenna can be applied to a range of low power electronic applications.

A quasi-millimeter electromagnetic wave with the frequency of 22-30 GHz is applied to detect knots and holes in wood samples. It has better spatial resolution while keeping good transmission properties compared to microwave region used in the previous experiments. The images of knots and holes in wood are clearly obtained by analyzing the phase and amplitude of the transmitted wave. And the phase measurement results are all better than amplitude results according to phase values changing much more than amplitude.

A very simple design method to embed routing capabilities in classical corrugated filters is presented in this paper. The method is based on the calculation of the heights and lengths of the so-called filters design building blocks, by means of a consecutive and separate extraction of their local reflection coefficients along the device. The proposed technique is proved with a 17th-order Zolotarev-filter whose topology is bent twice so that the input and output ports are in the same plane while preserving the in-line filters behaviour. This new filter allows the possibility of eliminating subsequent bending structures, reducing the insertion loss, weight, and PIM.

The surface plasmon effect in metallic photonic crystals has been investigated. Band structure graph is the only graph that can be used to explain the characteristics of photonic crystals. In this work, band structure graphs have been used to describe these characteristics, which include the surface plasmon effect of photonic crystals. Recently, band structure graphs for frequency-dependent materials have been analyzed by several researchers. The surface plasmon effect has been found for these materials. This article reports the effect of surface plasmons which cause resonance state in the metallic photonic crystals when the relative permittivity is changed from band structure graphs. The numerical results from the commercial software show the magnetic field distribution of waves on the normal photonic crystals, and defect mode is added for each frequency.

This article proposes a beam focusing compact wideband microstrip antenna loaded with mu negative (MNG) metamaterial. The antenna is designed to operate in the frequency spectra of IEEE 802.11a wireless LAN 5.15-5.85 GHz. The controlling of the beam direction has been investigated using eight different switching combinations of 12 PIN diodes which are integrated in the metamaterial unit cells. The main beam is found to be focused in -ve y, +ve y and omnidirectional in yz plane in agreement with switching condition of the metamaterial unit cell. The maximum gain enhancement of 7 dB is obtained at 4.9 GHz as the beam of the power pattern is focused in the negative y direction. The basic antenna with patch dimension (0.14λ × 0.14λ) provides wide impedance bandwidth of about 40%. Two prototypes of basic and proposed antennas have been developed using a low profile FR-4 substrate. The simulation results are found in good agreement with the measurement ones.

A novel miniature microstrip-fed multiband antenna for wireless local area network (WLAN) and X-band satellite communication applications is presented in this paper. The proposed antenna consists of two arc-shaped strips, dual inverted L-shaped parasitic stubs and a partial ground plane. The proposed antenna can excite multi-resonant modes while achieving a compact size of 18×34.5×0.8 mm³. The measurement results show that -10 dB impedance bandwidths are 290 MHz (2.28-2.57 GHz), 1.27 GHz (5.0-6.27 GHz), and 850 MHz (7.11-7.96 GHz), which can cover the entire operation frequencies of WLAN (2.48-2.4835 GHz, 5.15-5.875 GHz) and X-band satellite communication system (7.25-7.75 GHz) applications.

In this paper, a new microstrip balanced-to-balanced diplexer is presented and investigated. The proposed diplexer primarily consists of two balanced bandpass filter paths, and each balanced filter path can be designed independently based on two identical stub-loaded triple-mode resonators. It should be mentioned that no extra matching networks are required at the common balanced input port in the design. For demonstration, a prototype balanced-to-balanced diplexer operating at 2.30 and 2.83 GHz is designed, fabricated and measured with 3-dB fractional bandwidths of 13.0% and 13.4%. Both simulated and measured results are provided in satisfactory agreement.

Processing over-the-horizon radar (OTHR) signals is challenging due to appearance of several very close components in the time-frequency plane, strong noise and clutter, multipath propagation, and aliasing. We propose a two-stage procedure for estimating multipath signal components from the received mixture. In the first stage, the instantaneous frequency is estimated from the time-frequency representation of the received signal. The random samples consensus algorithm is applied to the instantaneous frequency estimate to improve the robustness of the procedure against various effects in the underlying signals. In the second stage, the MUSIC algorithm is applied to the dechirped and downsampled signal. The effectiveness of the proposed approach is verified using real-life signals.

A microwave diplexer implemented by using the twenty-first century substrate integrated waveguide (SIW) transmission line technology is presented. No separate junction (be it resonant or non-resonant) was used in achieving the diplexer, as the use of an external junction for energy distribution in a diplexer normally increases design complexity and leads to a bulky device. The design also featured a novel input/output coupling technique at the transmit and receive sides of the diplexer. The proposed SIW diplexer has been simulated using the full-wave finite element method (FEM), Keysight electromagnetic professional (EMPro) 3D simulator. The design has also been validated experimentally and results presented. Simulated and measured results show good agreement. The measured minimum insertion losses achieved on transmit and receive channels of the diplexer are 2.86 dB and 2.91 dB, respectively. The measured band isolation between the two channels is better than 50 dB.

A novel compact CPW (coplanar waveguide-fed) CPSS (Circularly polarized square slot) antenna is presented. The proposed single-layer antenna is composed of a rectangular ground plane embedded with two equal-size patches along two orthogonal directions. Equal amplitudes with 90˚ phase difference values of two patches is capable are generating a resonant mode for exciting two orthogonal E vectors. Axial ratio (AR) bandwidth is significantly enhanced due to slot corner modification. The designed CPSS antenna is compact in nature with volume of 0.37λ₀× 0.34λ₀ × 0.012λ₀ mm³ (λ₀= free space wavelength at centre frequency of the CP bandwidth). It has impedance bandwidth between 4.65-6.72 GHz (36.41%) and 3-dB axial-ratio bandwidth of 520 MHz (4.85-5.37 GHz), which covers 4.9 GHz (802.11j) WLAN for public safety ranging from 4.94 GHz to 4.99 GHz and WLAN (U-NII-1 and U-NII-2A) ranging from 5.150-5.350 GHz for indoor use. The gain variation for the frequencies within the CP bandwidth is also observed to be less than 0.6 dBic. The design is successfully implemented, and measured results are compared with the simulated ones, which are found in good agreement.

To improve HF detection of small RFID tags, a Distributed Diameter Coil (DDC) resonator is included in the reader coil. The key ideas of detection improvement are twofold: using a resonator with Magnetic Resonant Coupling (MRC) and modifying the distribution of diameter and current for each loop of the DDC resonator. These factors allow the magnetic coupling to increase between the reader and the smaller tag, especially in our case where the effective area of the tag is below 0,1% of the reader coil surface. Numerical simulations are carried out using HFSS to confirm the enhancement of the mutual coupling between the tag and the reader coil: the coupling coefficient is used in double-loop coupling (the case of the coupling of two loops), when a third loop (resonator) is inserted. The optimization of the magnetic coupling between a large reader and a small tag with resonator could be realized in changing first the sub-coil diameters, and then the sub-coil number of turns. One figure of merit to quantify the ability of surface detection is defined. A 15% improvement of detection surface in Horizontal Mode is measured at 1 cm of the reader plane in comparison with a conventional coil. Experimental detection measurements on real structures are described to validate statements.

A printed multiband multiple input multiple output (MIMO) antenna system is proposed in this paper. The MIMO antenna system is composed of two identical antenna elements which are perpendicular to each other. The defected ground plane with two microstrip lines is introduced to suppress the coupling between the antenna elements. The proposed MIMO system operates at two separated impedance bandwidths of 770 MHz (2.09-2.86 GHz) and 890 MHz (5.05-5.94 GHz) with an overall size of 50 × 50 × 1.59 mm³. The achieved isolation at the lower and higher frequency bands is higher than 20.9 dB and 17.8 dB, respectively. The proposed MIMO antenna system is feasible to be used for time-division long-term-evolution (TD-LTE, 2300-2655 MHz) and wireless local area network 802.11 a/b/g (WLAN, 2.4-2.4835 GHz, 5.15-5.875 GHz) applications.

The paper focuses on design and analysis of hexagon inspired fractal geometry and defected ground plane to evaluate the performance of patch antenna for wireless applications. It also emphasizes increasing the antenna bandwidth by incorporating novel rectangular Defected Ground Surface (DGS) structure with CPW feed. In the proposed work, antenna is simulated and fabricated for wireless applications using FR4 as the substrate, and it covers wide band with high gain. The antenna resonates at frequencies of 3.79 GHz and 5.5 GHz with measured return losses of -25.02 dB and -26.03 dB, respectively, making the proposed antenna suitable for Wi-Fi, cordless phone, wireless devices and wireless sensor networks applications.

A triply primed array (TPA) is configured on three mutually primed integers (N₁, N₂ and N₃), which operates with O(N₁N₂N₃) degree-of-freedoms to estimate the direction-of-arrivals (DOAs) of multiple incident quasi-stationary signals. The set of unique and contiguous lags of the proposed TPA is searched and verified. Simulation results verify that the proposed TPA can detect more incident signals with higher accuracy than its compatible counterparts.

This paper presents an efficient hybrid method consisting of finite-difference time-domain (FDTD) method, transmission line (TL) equations, and a fast calculation method for excitation fields, which can be applied to the coupling analysis of the shielded cable on the ground excited by plane wave rapidly. It can avoid modeling the infinite ground and the structure of the shielded cable directly. In this hybrid method, the shielded cable is decomposed into external and internal transmission line models, and the corresponding TL equations for the external and internal TL models are established necessarily. Then the FDTD method is utilized to solve the TL equations to obtain the transient responses on the shielding layer and core wires of the cable. A numerous examination of the coupling of coaxial cable exhibits that this hybrid method has very high accuracy and efficiency compared with the SPICE method. Finally, the methods of effective shielding protection of the cable have been proposed by analyzing the influences of the grounding states of the shielding layer, the electromagnetic parameters of the ground and the heights of the cable on the transient responses of the cable.

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.