In this paper, a new type of single loaded broadband double-whip antenna is designed for very high frequency (VHF). The simulation model by moment method is established to analyze the influence of antenna spacing on the performance of a double-whip antenna. The location of antenna loading and the parameters of loading network and broadband matching network are optimized by grasshopper optimization algorithm, and the voltage standing wave ratio (VSWR), gain, pattern and roundness of double-whip antenna are calculated. In fact, a fabricated prototype of the proposed antenna is realized. The measured VSWR is consistent with the simulation results, which is less than 3 at all frequencies, with an average value of 1.89; the maximum directional gain is greater than 2.01 dB, with a maximum of 6.44 dB and average value of 3.79 dB; the minimum roundness of antenna gain is 0.03 dB (at 30 MHz), and the maximum roundness is 1.87 dB (at 300 MHz); the efficiency is all over 51%, with a maximum value of 79% and an average value of 60.71%.

In this paper, a novel semi-circular ultra wide-band antenna inspired by a complementary split ring resonator for enhancement of bandwidth and a frequency selective surface reflector for gain enhancement is proposed for broadband applications. Initially, an ultra wide-band antenna employing a pair of L-shaped resonators and complementary split ring resonators is proposed which provides a wide impedance bandwidth of 130.3% from 3.16 to 15 GHz with -10 dB return loss. Finally, a frequency selective surface reflector is employed below the suggested ultra wide-band antenna to enhance the gain. The dimensions of the coplanar waveguide fed ultra wide-band antenna are 35 × 30 × 1.6 mm³ and those of the ultra wide-band antenna with a frequency selective surface reflector, which consists of 10 × 10 array of elements located at a distance of 17 mm below the proposed antenna, are 53.15 × 53.15 × 1.6 mm³. A parametric analysis of substrate dimensions of ultra wide-band antenna and the distance between ultra wide-band antenna and frequency selective surface reflector is performed. The average peak gain of the proposed antenna increases from 4.9 dB to 10.9 dB, which operates at 3.79 GHz, 4.44 GHz, 7.89 GHz, 9.01 GHZ, and 11.15 GHz proposed for broadband applications. With the help of ANSYS, the signal correlation of the proposed antenna is analysed by time domain analysis using similar antennas in face-to-face and side-to-side scenarios. The simulated results of the proposed model are in correlation with experimental ones of the prototype model.

This paper reports a novel approach using an inductive loading to reduce the resonant frequency of a mushroom-shaped high impedance surface. The current path is extended on the mushroom-shaped structure's vias and additional traces, which introduces a three-dimensional inductor to the unit cell and leads to an increase in total inductance. As a result, the resonant frequency of the high impedance structure decreases, and a smaller unit cell size can be achieved at the low gigahertz frequency range. Finite element electromagnetic simulation, equivalent circuits modeling, and experimental measurements suggest the feasibility of the proposed approach.

This work presents the design and simulation of a beam scanning antenna at 300 GHz using Luneburglens for 5th generation communication applications or beyond. The basic antenna consists of a highly directional Yagi-Uda antenna with lens shaped configuration (substrate lens antenna - SLA) and designed using multiple parallel elements such as one reflector and one driven element with 6 directors. The SLA is focused by Luneburg lens, which is modeled using a unique foam material AirexR82 with relative dielectric constant of 1.12, and it is pressed to realize different dielectric constants in order to obey the index law inside the lens. The final nine - element array of SLA integrated with Luneburg lens provides a 50% increase in bandwidth compared with conventional Yagi-Uda antenna along with an increase in the gain of 31.3% compared with single SLA. The designed model can achieve a beam scan coverage up to 146˚ with a maximum gain of 17.1 dBi and an estimated efficiency of 92.9%. The beam scanning antenna provides a wide bandwidth of 83 GHz starting from 289 GHz to 372 GHz. The analysis of the proposed antenna is done in CST suite and is validated using HFSS software.

In this paper, the required array patterns with controlled nulls are obtained by optimizing only the excitation phases of a small number of elements on both sides of the array. A genetic algorithm is used to appropriately find which elements of the array to be optimized and also to find the required number of the excitation phases. The performance of the proposed phase-only method is compared with some other exciting methods, and it is found to be competitive, fulfill all the desired radiation characteristics, and represent a good solution for interference mitigation. Moreover, the proposed phase-only array is designed and validated under realistic electromagnetic effects using CST full wave modeling. Experimental results are found in a good agreement with the theoretical ones and show realistic array patterns with accurate nulls.

An eight-port antenna system for fifth-generation (5G) multi-input multi-output (MIMO) mobile communication in smartphones is proposed, working in 3.5 GHz frequency band (3400-3600 MHz) and 5 GHz frequency band (4800-5100 MHz). The presented eight-port antenna array consists of four vertical structure antennas placed at four corners and four horizontal structure antennas etched along the two long sides of the circuit board. The height of vertical structure is only 4 mm, which is suitable for ultra-thin smartphones. The design of eight-port antenna array was fabricated and measured. According to the test results, an ideal impedance matching (superior to 10 dB), preeminent isolation (superior to 17 dB) and excellent efficiency (superior to 61%) are obtained over the 3.5 GHz frequency band and 5 GHz frequency band. In order to evaluate MIMO performance, the ergodic channel capacities and envelope correlation coefficients (ECC) are also investigated.

The effect of measurement errors in the S-matrix of a reciprocal 2-port device is recognized in the (usually low) difference between S₁₂ and S₂₁, as the device were nonreciprocal. This ``false non-reciprocity'' is analyzed in the present paper, and it is verified that, for low loss device, the difference acts principally on the phases of S₁₂ and S₂₁. This anomaly can be removed if a numerical correction is applied to the experimental S-matrix. In doing so, it is proved that the residual measurement errors have comparable amplitudes on all scattering parameters.

Automotive radars make use of angle information obtained from antenna arrays to distinguish objects that lie in the same range-Doppler cell (relative to the ego vehicle). This paper proposes novel ways of using presently known minimum redundancy arrays (MRAs) in single-input multiple-output (SIMO) and multiple-input multiple-output (MIMO) automotive radars. Firstly, an MRA-based sparse MIMO array is proposed as a novel modification to the nested MIMO array. The proposed sparse MIMO array uses MRAs as the transmitting and receiving modules, unlike the nested MIMO array, which uses two-level nested arrays (TLNAs) at the transmitting and receiving blocks. Upper bounds for the virtual array aperture and the overall attainable degrees of freedom (DOF) offered by the MIMO radar have been derived in terms of the number of sensors. Secondly, the suitability of large Low-Redundancy Linear Arrays (LRLAs) in SIMO automotive radars is also studied. A long-range automotive radar driving scenario was assumed for DOA estimation and simulations were carried out in MATLAB using the Co-array MUltiple SIgnal Classification (co-array MUSIC) algorithm. Simulation results confirm that the proposed MRA-based MIMO array provides better angular resolutions than the nested MIMO array for the same number of sensors and that LRLAs can serve as a handy replacement for ULAs in SIMO radars owing to their acceptable performance. As MIMO and SIMO radars designed from currently known MRAs were sufficient to satisfy the angular resolution requirements of modern automotive radars, a need to synthesize new MRAs did not arise.

In this paper, using quasi-conformal mapping, a bi-functional coating layer is designed with the intention of both cloaking and directivity enhancement of an omnidirectional antenna. For TM external waves coming from a certain direction, the proposed coating layer conceals the inner objects. In addition to the cloaking performance, the designed coating layer plays the role of a metamaterial-based lens that dramatically enhances the directivity level of inner omnidirectional loop-family antennas. To reach this goal, a proper coordinate transformation is elaborately utilized to transform the cylindrical wavefronts radiated from the antenna into semi-pure plane waves. With appropriate simplifications, the proposed coating layer turns into an isotropic meta-device, which is more suitable to be fabricated. To prove the feasibility of the implementation, an SRR-meander line meta-atom is designed to locally realize the required permittivity and permeability distribution of the bi-functional layer. Full-wave simulations are performed via COMSOL finite element solver to validate the cloaking effect and directivity enhancement of the proposed coating layer, at the same time.

A miniaturized multilayer tunable super wideband (SWB) bandpass filter (BPF) is presented based on a microstrip structure. A pair of transmission line is coupled with the aid of three defected ground structures (DGS) at ground to improve the coupling and provide ultra wide band pass response. One of the transmission line is placed at the top plane of the upper layer, and the other transmission line is at bottom plane of the lower layer with defected microstrip structures (DMS) to improve the return loss. Bandwidth can be tuned by properly selecting the resonator size. Circuit model for the microstrip resonator and mathematical analysis are given and studied. Finally, the proposed vertical connection with slotline structures and a three pole UWB filter is designed, simulated, fabricated, and the results are well vindicated by an exemplary circuit centered at 6.5 GHz with the measured fractional bandwidth (FBW) of 135%. The filter exhibits a constant group delay of 0.3 ns in the pass band and the size of the resonator is 13.67 mm×17.58 mm×3.2 mm.

In this paper, a contactless microwave transition is described and characterized. In our ``ElectroMagnetic Drive'' (EMDrive) measuring setup, it will be dedicated to transmit high Radio Frequency (RF) powers without any mechanical effort. It exhibits very good matching and transmission performances. It is found to transmit 100 W microwave power range at 2.45 GHz without any visible mechanical effect on a 10 mg precision balance, contrary to a previous coaxial cable. This device appears useful to every EMDrive setup and can be easily implemented.

This paper presents the simultaneous application of Minkowski fractal geometry and EBG structures for mutual coupling reduction in microstrip array antennas for the first time. In this approach, a modified version of Minkowski fractal geometry is applied on the patch elements, and at the same time 1D electromagnetic bandgap (EBG) structures, composed of 4 EBG elements, are placed between the array elements in a very close distance. Unlike many other coupling reduction methods, which have at least one of the issues of gain reduction or complex fabrication, the proposed method does need any via or double-sided etching and slightly increases the gain of the antenna, while an excellent reduction level of 23 dB has been achieved. To verify the concept, 2 array antennas with the spacing of λ₀ and λ₀/3 were fabricated and tested, showing very good agreement between predicted and measured results.

In this paper, we develop a multi-band circularly polarized planar antenna operating at 28 GHz and 60 GHz for 5G and WiGig applications. The antenna is composed of a square slot antenna fed by a proximity coupled microstrip line and loaded by grounded square loop and three tilted angle strips. Grounded square patch introduces resonance at 60 GHz frequency while the strips introduce resonances at 28 GHz. The square slot is designed as a wide-band antenna which can support these two resonances.

An eight-element multiple-input-multiple-output antenna system which consists of H-shaped slot antennas is presented around the handset frame for 5G applications. Each antenna element consists of a H-shaped radiating surface and an L-shaped microstrip feeder. In the frequency bands of 3.4-3.6 GHz and 4.7-5.1 GHz, the isolation is lower than -15 dB by introducing the ladder-shaped defect ground structure. The antenna efficiency is 50%-81%, and the envelope correlation coefficient is lower than 0.02 among antenna elements. The measurement results agree well with the simulation ones, indicating that the proposed antenna can satisfy the requirements of 5G communication.

A wideband high gain circularly polarized (CP) rectangular dielectric resonator antenna (RDRA) having a frequency range of 21 to 31 GHz is proposed. The RDRA consists of two layers with different dielectric permittivities and has been excited using a cross slot aperture. The proposed antenna offers wide impedance and CP bandwidths of ~36.5% and 13.75% respectively, in conjunction with a high gain of ~12.5 dBi. Close agreement has been achieved between simulated and measured results.

In this paper, an auxiliary differential equation (ADE) transmission line method (TLM) is proposed for broadband modeling of electromagnetic (EM) wave propagation in biological tissues with the Cole-Cole dispersion Model. The fractional derivative problem is surmounted by assuming a linear behavior of the polarization current when the time discretization is short enough. The polarization current density is approached using Lagrange extrapolation polynomial, and the fractional derivation is obtained according to Riemann definition of a fractional α-order derivative. Reflection coefficients at an air/muscle and air/fat tissues interfaces simulated in a 1-D domain are found in good agreement with those obtained from the analytic model over a broad frequency range, demonstrating the validity of the proposed approach.

Present contribution introduces, for the first time, the description of human exposure dynamics to mobile phone radiation by implementing the use of in-air integrated energy density (IED) evolution in time. Using the amplitude probability density (APD) function capability of a real-time spectrum analyzer, we demonstrate the differences in exposure due to five different mobile applications running in Long Term Evolution (LTE) standard, based on energy deposited in air: voice call; voice over LTE (VoLTE); video call, file download and live streaming. This exposimetric method will be of great interest also for the new 5G communication standard. The superiority of the approach has three branches: a) integrated APD allows a sample rate of the order of 0.6 x 10⁸/s which is equivalent to an extremely agile tracing of the power level change in LTE communication standard (happening at every 6.67 μs); b) momentary and mean IED accumulation rate can be computed, and minute differences between mobile applications may be observed during their running time; c) the superficial tissue temperature increase may be rapidly estimated after the period of use of one specific wireless application in the GHz frequency range. The method implemented here also provides the means for rapid usage profile expectancy assessment of a mobile phone user.

A compact substrate integrated waveguide (SIW) filter based on composite right/left-handed (CRLH) resonator units is implemented in this paper. The filter is composed of two CRLH resonator units serially connected by a SIW transmission line unit. The structure of the filter and equivalent circuit transmission behavior are analyzed, and a novel design method by optimizing the length and width of the interdigital metal slots to decrease the filter operation frequency is proposed. To further demonstrate the design theory and performance of the proposed filter, the filter was designed and fabricated on an RT6010 dielectric material. The measurement results show that the proposed filter works at a center frequency of 5.8 GHz with 200 MHz bandwidth. The insertion loss is 2.3 dB, and the filter size is only 10 mm × 7.4 mm.

A T-shaped feed based differential microstrip bandpass filter (BPF) with high common-mode (CM) rejection ratio is presented. The filter comprises two magnetically coupled conventional square open-loop resonators (SOLR), with capacitive coupled T-shaped input-output (I/O). The choice of the T-shaped I/O coupling feed enables a higher common-mode suppression of -57 dB at f₀^d that extends up to 4.1f₀^d with a value better than -30 dB. Frequency f₀^d is the cutoff frequency of the differential-mode (DM) passband. Moreover, this feed can symmetrically position two transmission zeros (TZs) at the upper and lower stopbands. This yields a highly selective and compact filter. Additionally, a T-shaped feed only excites the odd mode of the filter resulting in a wide stopband with high out of band rejection. The upper and stopband rejection of the filter is better than -50 dB. To demonstrate the design, DM and CM lumped models of the filter are proposed and studied. The filter operates at 1.263 GHz with a fractional bandwidth (FBW) of 3.9%. The design is validated experimentally by characterizing DM, CM, common-mode to differential-mode (CD), and differential-mode to common mode (DC). Moreover, the group delay (GD) response of the filter is measured, and a significantly flat response is observed with a maximum delay variation of only 0.88 ns in the 3 dB bandwidth.

In this paper, a new robust computational method that applies the geometrical theory of diffraction (GTD) in conjunction with the ray tracing (RT) technique is developed to evaluate the electromagnetic scattering pattern due to a plane wave incident on a rough surface of quite arbitrary statistical parameters. The Fresnel reflection model is applied under the assumption of arbitrary electrical and optical properties of the rough surface material to obtain the scattering patterns for both the power reflected to the upper half-space and the power transmitted into the medium covered by the rough surface. Also, the polarization of the plane wave primarily incident on the rough surface is taken into consideration. The algorithm developed in the present work accounts for multiple bounces of an incident ray and, hence, it can be considered arbitrary higher-order GTD-RT technique. The accuracy of the obtained results is verified through the comparison with the experimental measurements of the scattering pattern of a light beam incident on rough sheets with specific statistical properties. Also, some of the obtained results are compared to other published results using the geometrical optics (GO) and the second-order Kirchhoff's approximation. The numerical results of the present work are concerned with investigating the dependence of the scattering pattern on the surface roughness, refractive index, angle of incidence, and the resolution of the geometric model of the rough surface. Also, it is shown that, for limited resolution of the rough surface model, the accuracy of the calculated scattered field depends on the angle of incidence of the primary beam and the surface roughness.