This study proposes an anti-jamming scheme for linear frequency modulated (LFM) radars to combat smart noise jamming, which is a newly proposed pattern that is very effective against LFM radars. First, by utilizing the smeared spectrum technique, the chirp rates of the target return and jamming signal can be changed. The target return and jamming signal then exhibit different characteristics after the application of matched filters. Finally, the true target can be distinguished from the smart noise jamming, which is suppressed by the reconstruction and subtraction in the receiving signal. Numerical experiments demonstrate the feasibility and practicability of the proposed anti-jamming device, which is also verified as having a superior performance over existing jamming suppression schemes.

A composite wideband absorbing material (WAM) covering dual bands is designed, to reduce the in-band radar cross section (RCS) for broadband antenna in this paper. The upper layer is a traditional absorber while the lower one is a dual-band frequency selective surface (FSS), which is formed by a square ring and an improved Jerusalem cross structure. The absorbing band has been broadened to 112% compared with the magnetic sheet without FSS. Over C and X bands, the absorption rate is over 90%. By using the FSS-based WAM as the ground plane of a Vivaldi antenna, substantial RCS reduction is obtained from 2-18 GHz. Moreover, the RCS is reduced remarkably over -80°-80° incident angles except for minority angles, with the radiation performance preserved at the same time. The experimental results are in good agreement with the simulated ones.

In this study, the effective magnetic response of magnetic metamaterial is considered in the microwave frequency range. The metamaterial is an infinite isotropic dielectric host medium with periodically embedded ferric cylindrical inclusions. It is assumed that the inclusions are partially magnetized by a dc bias magnetic field. The electromagnetic wave propagation is considered in the direction of bias magnetic field and transverse to it. It is shown that the real part of effective relative permeability can have Re(μ_eff)<0 or 0< Re(μ_eff)<1 or Re(μ_eff)>1 subject to the value of bias field.

Design and characterization of a multilayered compact implantable broadband antenna for wireless biotelemetry applications is presented in this paper. The main features of this novel design are miniaturized size, structure that allows integration of electronic circuits of the implantable medical device inside the antenna, and enhanced bandwidth that mitigates possible frequency detuning caused by heterogeneity of biological tissues. Using electromagnetic simulations based on the finite-difference time-domain method, the antenna geometry was optimized to operate in the 401-406 MHz Medical Device Radio communications service band. The proposed design was simulated implanted in a muscle tissue cuboid phantom and implanted in the arm, head, and chest of a high-resolution whole-body anatomical numerical model of an adult human male. The antenna was fabricated using low-temperature co-fired ceramic technology. Measurements validated simulation results for the antenna implanted in muscle tissue cuboid phantom. The proposed compact antenna, with dimensions of 14 mm × 16 mm × 2 mm, presented a -10 dB bandwidth of 103 MHz and 92 MHz for simulations and measurements, respectively. The proposed antenna allows integration of electronic circuit up to 10 mm × 10 mm × 0.5 mm. Specific absorption rate distributions, antenna input power, radiation pattern and the transmission channel between the proposed antenna and a half-wavelength dipole were evaluated.

In this paper, we report a single layer modified T-shaped dipole antenna for UHF-RFID tag applications. The designed RFID tag antenna consists of a pair of T-shaped dipole strips loaded with four half discs patches and a tag chip placed in the center. The antenna's size is 80×40×1.6 mm³. Performance of the proposed design was investigated with simulations and measurements. The main feature of this design is that the RFID tag antenna can operate effectively at 868 MHz and 915 MHz frequency bands which make it broadband. The maximum reading range measured in an anechoic chamber is 4.25 m and 5.27 m at 915 MHz and 867.5 MHz, respectively. Furthermore, the RFID tag antenna can work on metallic plates when inserting a foam spacer between them. The final result has a simple configuration, low profile and can be suitable for practical applications dealing with free-space and metallic objects.

A novel broadband dual-polarized magneto-electric (ME) dipole antenna is proposed for 2G/3G/LTE/WiMAX applications. The proposed antenna has stair-shaped feeding strips to impart a wide impedance bandwidth to it and a rectangular box-shaped reflector to enhance its stability in radiation patterns and high gain over the operating frequencies. The measured results show that a common impedance bandwidth is 80% with standing-wave ratio (SWR) ≤ 1.5 from 1.68 to 3.92 GHz and port-to-port isolation larger than 25 dB within the bandwidth. The measured antenna gains vary from 9.2 to 12 dBi and from 9.2 to 11.8 dBi for port 1 and port 2, respectively. The antenna has nearly symmetrical radiation patterns with low back-lobe radiation both in horizontal and vertical planes, and broadside radiation patterns with narrow beam can also be obtained.

Conventional radar imaging methods use coherent analysis which highlights the necessity of signal phase measurement setups and complex inverse algorithms. To mitigate these drawbacks, this paper proposes a novel phase-less imaging algorithm. A nonlinear over-determined system of equations based on signal Doppler shift is developed, and a new error function originated from least square method is introduced. To obtain the exact position of targets, hybrid optimization is applied to the achieved error function. Simulation results demonstrate that the proposed method is well capable of detecting the targets containing strong point scatterers, even with the distance of 1cm. Also, the resolution of imaging algorithm for point scatterer circumstances is obtained in the order of millimeter. Concurrent with the priory imaging algorithms with the same imaging setups using proposed method reduces complexity and increases imaging swiftness.

Direction of arrival estimation has a noteworthy significance in numerous applications, such as radar systems, smart antennas, sonar, mobile communications, and space communications. The algorithms used to estimate the direction of arrival are to some degree complex and time consuming. Also, the number of antenna elements is a discriminating parameter for assessing the performance of the DoA technique. For real time systems, quick and savvy techniques are required. Along these lines, decreasing the estimation time and also reducing the system cost while keeping a generally high precision are crucial issues. In this paper, a new technique for linear antenna arrays synthesis using optimized number of antenna elements and its application to direction of arrival estimation is introduced. The synthesized arrays exhibit approximately the same radiation pattern as the original arrays. The optimized antenna arrays are synthesized using reduced number of antenna elements. In this case, the number of antenna elements reduction will minimize the system cost and decrease the number of picked samples from the different signal sources. As the number of samples decreases, the dimensions of the steering matrix and data correlation matrix are reduced. In this context, the computational burden, estimation time, and system cost are optimized. The proposed technique can be applied to single or multi-snapshot DoA estimation techniques.

We consider the accuracy improvement of the high frequency scattered fields from 3-D convex scatterers. The Fock currents from the convex scatterers are carefully studied. Furthermore, we propose the numerical contour deformation method to calculate the Fock currents with frequency independent workload and error controllable accuracy. Then, by adopting the Fock currents and the incremental length diffraction coefficient (ILDC) technique, the scattered fields are clearly formulated. Compared to physical optics (PO) scattered fields from 3-D convex sphere, numerical results demonstrate significant accuracy enhancement of the scattered field via the Fock current approach.

Light sheet microscope is a versatile imaging tool for high imaging speed and signal to noise ratio (SNR). In this type of system, the illumination is perpendicular to the direction of detection. Due to its structural feature of perpendicular detection, the SNR is comparable to total internal reflection fluorescence (TIRF) microscopy. Therefore, the perpendicular detection system is of great application prospect. In this paper, we develope a compact optical perpendicular detection system, which can not only be utilized to measure fluorescence with high SNR, but also capture a fluorescent image of flow fluorophore.

This paper examines the electromagnetic shielding characteristics of milano, cardigan and lacoste with respect to weft and rib type composite knitted fabrics. All of these fabrics, made of hybrid yarns containing 50µm diameter metal fibres such as copper, silver and stainless steel, were produced for electromagnetic shielding purposes. The shielding eeffectiveness (SE) of the fabrics was measured by reading S parameters from the signal when the sample was placed in the path of signal at the frequency range 1.7 to 2.6 GHz inside the WR430 waveguide system. After which S parameters was converted to SE values. The variation in electromagnetic shielding effeffectiveness (EMSE) with the factors, such as radiant frequency, metal type, course density and geometry, were discussed. Experimental results show that all factors, especially the geometry of the fabric, have significant effect on SE. The best EMSE values were obtained by milano type knitted fabrics which was above 20dB. It was found that milano, cardigan and lacoste composite fabrics, uncommon in EMSE experiments found in literature, give better shielding performances than rib and weft composite fabrics, under the same conditions.

In this paper, a simple broadband circular polarization (CP) V-shaped slot antenna is developed. The CP antenna consists of Z-shaped feedline with a stub and a patch, and symmetrically etched two rightangled V-shaped slots (an open slot and a closed slot) along the center line. The stub is introduced for multi-resonances to obtain broadband. The broad CP and impedance bandwidths overlap by the symmetrically etched right-angled V-shaped closed slot along the center line and the Z-shaped feedline placed in a proper position. The measured results show that the proposed antenna has a broad overlapped 3-dB axial ratio (AR) bandwidth and -10 dB impedance bandwidth of 71% (2.19-4.6 GHz).

This paper investigates an angle of arrival (AOA) and polarization joint estimation algorithm for an L-shaped electromagnetic vector sensor array based on rank-(L, L, 1) block component decomposition (BCD) tensor modeling. The proposed algorithm can take full advantage of the multidimensional information of electromagnetic signal to obtain the parameter estimation more accurately than the matrix-based method and the existing tensor decomposition method. In addition, the algorithm can accomplish pair-matching of estimated parameters automatically. The numerical experiments demonstrate that even under the conditions of low SNR and limited snapshots, the proposed algorithm can still steadily achieve high detection probability with low estimation error, which is important for practical applications.

This paper presents a tutorial on photonic techniques for arbitrary RF waveform generation, highlights some key results and reviews the recent developments in this area. It also predicts that photonic integration of the entire system as compact photonic chip will be the major research focus and holds the key role for future developments.

The evaluation of the magnetic field from double-circuit twisted three-phase power cable lines misses a sound and exhaustive theoretical and experimental treatment in the literature. This paper presents a rigorous approach to the calculation of the magnetic field from double-circuit twisted three-phase cables, whereby the magnetic field generated by such cables is computed as the vector sum of the two individual fields generated by each twisted three-phase cable. This approach is validated by means of extensive measurements of the magnetic field from single- and double-circuit twisted three-phase power cables - provided by Italian utilities - identical to those installed in the field.

A new miniaturized microstrip branch-line coupler with good harmonic suppression is proposed in this paper. The new structure has two significant advantages, which not only effectively reduces the occupied area to 20.4% of the conventional branch-line coupler at 0.96 GHz, but also has high 6th harmonic suppression performance. The measured results indicate that a bandwidth of more than 120 MHz has been achieved while the phase difference between S₂₁ and S₃₁ is within 90° ± 1°. The measured bandwidth of |S₂₁| and |S₃₁| within 3 ± 0.3 dB are 145 MHz and 150 MHz, respectively. Furthermore, the measured insertion loss is comparable to that of a conventional branch-line coupler. The new coupler can be easily implemented by using the standard printed-circuit-board etching processes and is very useful for wireless communication systems.

A microstrip magnetic dipole Yagi antenna with the feasibility of obtaining a wider bandwidth and relatively smaller size is proposed and demonstrated. The proposed antenna, consisting of a reflector, a driver with backed soldered SMA connector, a coupling microstrip line with three rectangular slots and three modified directors, is designed and fabricated. Good agreement between simulated and measured results is observed. Simulated and measured results reveal that the proposed antenna can provide an impedance bandwidth of 19.2% (4.95-6 GHz). Meanwhile, within the impedance bandwidth, the radiation pattern of the proposed antenna has front-to-back (F/B) ratios ranging from 10.1 dB to 26.1 dB, cross-polarization levels in the endfire direction from 47.1 dB to 73.0 dB, peak gains from 6.4 dBi to 10.4 dBi with an average peak gain of 9.6 dBi and endfire gains from 2.2 dBi to 4.3 dBi with an average endfire gain of 3.1 dBi. Additionally, the measured bandwidth of 19.2% (4.95-6 GHz) not only meets the need for certain Wi-Fi (5.2/5.8 GHz) or WiMAX (5.5 GHz) band communication application, but also provides the potential to implement multiservice transmission.

A low-cost wideband textile antenna based on the substrate integrated waveguide (SIW) technology is proposed, and a pure copper taffeta fabric etched on a woolen felt substrate is used to realize the presented antenna. The impedance matching frequency band for the designed structure is from 2.27 GHz to 3.61 GHz, which is significantly improved compared with previous studies. The operational principle of the proposedquasi-Yagi textile antenna is also described in this paper. The antenna is fabricated and measured, and a good agreement is achieved between the simulation and experimental results. The designed antenna has themaximum gain and efficiency of 4.2dB and 84%, respectively. According to its compactness, low-cost and low-weight specifications, the proposed antenna is a good candidate for being utilizedin wearable communication devices.

A generalized multiphysics model using COMSOL Multiphysics software for optimizing the sintering process of iron powders having various green densities is developed. The modeling is facilitated by designing a 30 GHz multimode applicator, where the test sample is placed for the microwave processing. The effective dielectric and magnetic properties of the resultant metal powder compact is estimated using the effective electromagnetic model considering the idea of core - shell particle approach followed by the Lichtenecker's mixture formula. A theoretical approach relating the penetration depth, proper impedance matching and volume fraction of different density powder compacts is also discussed here. From the study, it is clear that the effective dielectric, magnetic, and thermal properties all contribute to the microwave sintering process of metal powders.

This paper presents non-coil sources to improve the wireless power transfer efficiency for implantable device used in various medical applications --- cardiovascular devices, endoscope in the small intestine, and neurostimulator in the brain. For each application, a bound on the power transfer efficiency and the optimal source achieving such bound are analytically solved. The results reveal that depending on the depth of the implantable devices, power can be transferred to a sub-millimeter scaled receiver with the efficiency ranging from -57 dB to -33 dB, which is up to 6.6 times higher than the performance of existing coil-based source systems. The technique introduced in this paper can be broadly applied to other medical applications.