Vol. 104

In application to active microwave remote sensing, the counterwise RL (left-hand circularly polarized transmitting and right-hand circularly polarized receiving) and LR polarized bistatic scattering are generally stronger than the likewise LL and RR ones, respectively. In this paper, we investigate the circularly polarized propagation over terrain profile at 1.575 GHz and 900 MHz in application to wireless communication. Completely different from common sense in remote sensing, however, numerical simulations show that field strengths for likewise polarizations are larger than those for counterwise polarizations. For further verification, circularly polarized bistatic scattering from terrain is also provided, which is consistent with previous conclusion that the counterwise LR polarized one is larger. Physical mechanism of such a contradictory behavior is explicated by local Fresnel reflections, and physical insights are offered for terrain propagation of circular polarizations. It is suggested that the likewise configuration be adopted in wireless communication, although the counterwise is adopted in microwave remote sensing.

A triple band artificial magnetic conductor (AMC) featuring zero reflection phase at 1.18 GHz, 1.59 GHz, and 2.45 GHz is designed and modeled. A square patch is used to achieve the first resonance. The other two resonance frequencies are generated by two square slots inserted in the first patch. All the three resonant frequencies are adjusted independently of each other and easily predicted by the developed analytical model. A good agreement between electromagnetic simulation and analytical results is obtained with a resonance frequency shift lower than 120 MHz.

A miniaturized half-mode substrate-integrated-waveguide (HMSIW) based bandpass filter with defected ground surface (DGS) for sub-5G applications is presented in this research. The novelty in this article is the proposal of an original configuration of an SIW Filter composed of a mix of DGS cells; each couple of C shapes is etched exactly beneath of two cross shapes, which give us long rejection. We have used six periodic cross-shaped slots as DGS in top of the cavity plane for disturbing the current and creating stopband rejection, and we have also used three couples of C-shaped DGS cells in the bottom plane to improve the performances of the proposed filter. This novel bandpass filter is developed on a 1.54 mm-thick FR-4 (with relative permittivity of 4.3 and the tangent loss of 0.025) operating in the band ranging from 3.4 GHz to 3.8 GHz with a bandwidth of 400 MHz and having the size of 13.5 × 38.6 mm². The proposed HMSIW-based filter is simulated, fabricated, and measured. The measurement results are in decent agreement with the simulation results.

In this paper we present a high pass filter based on half mode substrate integrated waveguide HMSIW technology dedicated to the transmission of microwave signals range from 6 GHz to 18 GHz. The taper is used for microstripe to SIW transition. We designed SIW line transmission using CST and HFSS simulators on a Rogers RT5880 substrate with dielectric constant of 2.2 and thickness of 0.508 mm, and we used the half mode technique for miniaturizing the filter size and achieving a size reduction about of 50%. The fabricated filter size is 60 x 12 mm². The lower measured return loss is about -51 dB. We compared the simulation results with measurement ones for validating our proposal. Good agreement between CST, HFSS and measurement results is observed.

In this paper, a novel low-profile direct feed antenna element is proposed to work across the mm-wave frequency band for 5G smartphone applications. The antenna covers the frequency band from 25-32 GHz achieving a wide fractional bandwidth of 24.5%. Contrary to most of the previously reported designs, the proposed antenna has a low-profile single-substrate structure and uses a conventional corporate feed. To improve the overall gain, a 16-element antenna array is formed based on the proposed antenna element. The total realized gain of the array is 15 dBi, and its size is 63×10×0.64 mm³ which fits inside a smartphone chassis. To validate the idea, a prototype is fabricated and measured. A study is also conducted, through simulations, on the beam steering capabilities of the antenna array using digital phase shifters. Having a simple structure and good performance makes the proposed antenna array an excellent candidate for 5G smartphone applications.

A dual-band dual-polarized dipole antenna with an artificial magnetic conductor (AMC) reflector is proposed, which can be applied in 5G base stations. The antenna consists of a pair of ±45° crossed dipoles and a wideband AMC reflector. By adopting arrow-shaped dipoles and introducing slots, dual-band characteristic is achieved. The AMC is designed to operate with 90° reflection-phase bandwidth of 2.1-3.9 GHz (30%). Compared with using traditional reflector, the profile height can be reduced from 0.25λ₀ to 0.11λ₀ (where λ₀ is the free-space wavelength at 2.6 GHz). The measurement results show that the impedance bandwidth with |S₁₁| < -14 dB is about 15.5% (2.44-2.85 GHz) and 18.6% (3.17-3.82 GHz), covering the Sub-6 GHz bands. The average gain is 8.5 dBi in the lower band and 8.2 dBi in the upper band. At 2.6 GHz and 3.45 GHz, the half-power beamwidth of the antenna is 77° and 80°, respectively. In the two bands, the port isolation of the antenna is more than 28 dB, and the cross-polarization level is less than -20 dB.

This paper presents a broadband antenna for 5G indoor micro base station, which has a low profile and simple structure. The proposed antenna avoids the traditional high-cost multilayer technology and is a low-cost configuration. It consists of a center fed circular patch with four shorting pins to properly stimulate the radiation mode of TM₀₁ and TM₃₁ internally. Next, four equally sized fan-shaped slots are opened in the radiator to further expand the bandwidth and improve the input impedance. |S₁₁| < -10 dB simulation impedance bandwidth is about 51% from 3.11 to 5.24 GHz and covers 5G n78 (3.3-3.8 GHz) and n77 (3.3-4.2 GHz) and the n79 (4.4-5 GHz). The voltage standing wave ratio (VSWR) < 1.8 in the whole operating frequency band, which has good matching characteristics.

An efficient and stability-improved finite-difference time-domain (FDTD) method with auxiliary difference equations (ADE) for cold magnetized plasma is developed in this paper. The two equations of Ampere's law and the auxiliary equation for plasma are unified as a single equation at first. Then the leapfrog difference scheme is applied to it and Faraday's law, respectively. By introducing a mid-term computation into the unified equation, the iterative equations of the ADE-FDTD for plasma are derived. Its stability condition remains the same as that of a vacuum which is analyzed and numerically verified. Numerical experiments show that our proposed method is more efficient than those provided by others but with the same accuracy. Finally, the transmission properties of a magnetized plasmonic slab are investigated. The reflection and transmission coefficients of the right-circularly-polarized (RCP) and left-circularly-polarized (LCP) waves are calculated. The results show that our proposed method can be applied to study these plasma-based structures accurately and efficiently.

RF and mm wave filterssuffers from a common problem of asymmetries in filters transmission response caused by unwanted field couplings between individual resonators. In this paper, unwanted or spurious couplings between non-adjacent resonators are identified in the filter network from the simulation stage and mitigated to the extent possible. A 4-pole Quasi Elliptic Planar Band Pass Filter is fabricated at 48.5 GHz on a Liquid Crystal Polymer (LCP) substrate. An improvement of 6 dB in side lobe imbalance in filter transmission response is obtained. Effect of spurious coupling on band pass filters transmission response is demonstrated through EM simulation. Commensurate measurement results are presented.

This work is purposed to provide microstrip antennas for a CP-SAR system with low sidelobe, tilted beam, and circular polarization. This antenna is configured for the L-band (1.27 GHz) mounting on an Unmanned Aerial Vehicle (UAV). The proposed microstrip antenna consists of three-square radiating elements, due to the ease in fabrication. Meanwhile, the proximity structure has been adopted in the feeding network. The tilted beam was obtained by arranging the different phases for each element. On the other hand, a low sidelobe was achieved by managing the power distribution of each patch using the Chebyshev polynomial. The proposed antenna was precisely printed and examined in an anechoic chamber to verify the characteristics of the antenna such as polarization, sidelobe level, and beam direction. Based on the measurement results, the proposed antenna has a tilted beam and a low side lobe that meets the specifications of the CP-SAR system.

This article presents a compact, low profile, four ports multiple-input-multiple-output (MIMO.) antenna operating at the n38 and n41 5G frequency bands. The antenna has a measured -10 dB bandwidth of 2.5-2.9 GHz with isolation less than -11 dB. The designed antenna system employs open slot radiators etched on a single-sided rectangular PCB substrate with a total size of 40 ×100 mm², including a ground plane. The open slot radiators are symmetrically printed at the four corners of the rectangular substrate. The radiators are excited by 50-Ω strip lines. Rectangular-shaped slits are used as decoupling structures. MIMO parameters such as the envelope correlation coefficient (ECC), channel capacity loss (CCL), and mean effective gain (MEG) are being calculated using the measured results. The ECC is less than 0.1 over the entire operating band despite the antenna's small size. The proposed antenna shows good performance in two sub-6-GHz frequency bands for 5G NR applications: n38 (2570 to 2620 MHz) and n41 (2496 MHz-2690 MHz).

An elliptical shape patch (ESP) antenna with inverted U-shaped slots is proposed and presented in this paper for on-body communication. A coplanar waveguide (CPW) feed is used as ground to produce impedance matching, and inverted U-shaped slots are used to produce the ultra-wideband (UWB). The proposed ESP antenna model covers UWB characteristics in free space, and it is observed at 3 to 10.7 GHz. When it is implanted on flat tissue model of human body, the bandwidth is 2.2 to 10.8 GHz. The SAR values of 1.26 W/kg and 1.58 W/kg are observed on-body at 4.9 GHz and 7.3 GHz operating frequencies, respectively. The results with respect to radiation pattern, gain, reflection coefficient, surface current distribution are also presented.

Various resonance modes, high transmission, and quality factor with simple design are highly desirable parameters for realizing nano-integrated plasmonic devices. In the context, a plasmonic structure consisting of two straight waveguides MIM coupled one central defective circular nano-disk resonator (CNDR) is proposed in this work. The insulator and metal of the proposed plasmonic filter are air and silver, respectively. The plasmonic filter is designed and investigated numerically by using the finite difference time domain method (FDTD). Our simulation results indicate that the proposed plasmonic filter has two transmission peaks with a maximum transmission equal to 80 and 70 percent. The advantages of the proposed filter are the various resonance modes with high transmission peaks and high quality factor which reaches 35.27. In view of these features, our proposed structure of plasmonic filter has the potential to be employed in various devices such as plasmonic demultiplexers and sensors for optical communication purposes.

The design of an innovative breast model system that focuses on a wideband for the detection of malignant tumours is described. The planned antenna has an overall area of 18×28 mm² and a fractional bandwidth (FBW) of 99% across a frequency spectrum of 3.4-10 GHz. The suggested antenna has excellent impedance matching, a considerable gain of 3.95 dBi, maximum efficiency of 96.98%. Omnidirectional radiated patterns are verified in the frequency, and time-domain analysis is also investigated for breast tumor diagnosis. For detecting a breast tumor with accuracy, the suggested antenna S₂₁ parameters are evaluated together, including imaging outcomes of current densities and specific absorption rate (SAR). These findings show that the radiator and the whole system work well at finding the tumor.

A dual-band hexagon shape substrate integrated waveguide (SIW) based band pass filter with single loop complementary spilt ring resonators (CSRRs) is introduced in this paper. The design parameters of this filter are optimized by using artificial neural networks (ANNs). Especially error back propagation multilayer perceptron (EBP-MLP) neural network with Levenberg-Marquart (LM) algorithm is used. A physical prototype of the proposed model is fabricated and tested. In the lower passband from 10.2 to 10.6 GHz, the insertion loss is about -0.8 dB with a fractional bandwidth of 3.85%, and in the upper passband from 12.11 to 13.31 GHz, the insertion loss is about -0.8 dB with a fractional bandwidth of 9.56%. It is observed that the insertion loss is same in both the passbands. The obtained experimental results are in good agreement with the estimated results using full-wave analysis and ANN optimization.

A high frequency device design and simulation results are reported for an 8 x 8 phased array of unit cells. Each unit cell comprises a (3 x 3) sub-array of 1/4 wave rod monopole radiators. Each unit cell is the basic building block that can be arranged to form 9 interpenetrating arrays. Each interpenetrating array comprises an independently addressable 8 x 8 array of 1/4 wave rod monopole radiators that fits into the lateral space of a single 8 x 8 array of patch radiators but can operate on 9 independent radio frequency channels within the same contiguous communication band without interference and can direct each radio frequency channel into independent directions simultaneously. The beamformer architecture, operation principle, and simulation results are presented and discussed, and an outline of its construction based on 2.5D integration is presented.

In this article, two compact Substrate Integrated Waveguide (SIW) bandpass filters based on Defected Ground Structure (DGS) technology are proposed. Hilbert Cell of second orderis the resonator shape proposed for the DGS of both filters, where the first filter DGS consists of five pairs, and the second one uses only three pairs. The pair used in the first filter consists of two cells located side to side whereas they are placed face to face in the second filter. In order to enhance the performance of the second filter and based on the evanescent-mode technique, three other pairs of first order Hilbert cells are engraved on the top layer. Both band-pass filters are designed to operate in C band with a measured bandwidth of 1.8 GHz for the first filter and 0.86 GHz for the second one. The proposed structures have the same physical dimensions, which is 38.1 mm×16 mm with different measured insertion losses of -2.5 dB and -2.7 dB. Both structures exhibit an upper stopband rejection with attenuation around -20 dB and -29 dB, respectively. The filters operate in a transmission bandwidth of [5.5 GHz-7.3 GHz] and [5.27 GHz-6.13 GHz] with a fractional bandwidth (FBW) of 28.1% and 15.09% for the first filter and the second filter respectively. A good agreement is reported between the measured and simulated results.

As unmanned aerial vehicle (UAV) is widely used in many civilian fields the wideband (WB) high power electromagnetic radiation devices development, whether the WB radiation would influence the civilian UAV to fulfil its tasks needs to be analyzed. Therefore, the radiated susceptibility of three models of DJI UAVs is studied in the paper. A decimetric wave oscillator with the power of over 500 MW was introduced as the radiation source. In experiment, adjusting the distance between radiation antenna and UAVs to change the electric field and the testing antenna was employed to measure the electric field on line. The three models of UAVs can be shot down by the electric field of 10 kV/m, 20 kV/m and 30 kV/m, respectively. Besides, as electric field reached up to over 35 kV/m, the rotor motor, electric control system and inertial measurement unit (IMU) in Mavic Air and Mavic Air 2 were easier to burn down. Except that, the energy accumulation effect has been proved in the experiment. In conclusion, the UAVs should fulfill tasks in the WB electromagnetic environment whose electric field is much less than 10 kV/m, and some shielding methods are needed to make UAV survive.

An electronically reconfigurable reflectarray antenna of 12 × 12 units is presented in this paper. The element consists of a slotted square patch and a gapped metal square ring. PIN diodes are loaded on slotted square patches, which can be electronically controlled to produce two states with 180˚ phase difference. A reflectarray prototype is fabricated and experimentally studied. Experimental results agree well with the full-wave simulations by Ansys HFSS, and scanning beams within ±45˚ range are obtained with a maximum aperture efficiency of 14.9% at 5.8 GHz. 1-dB bandwidth is 9.9%, and 3-dB bandwidth is 19.1%.

This paper presents a mechanically reconfigurable reflectarray with height adjustment for phase compensation. We designed, fabricated, and measured a prototype of 11×11 elements with microcontrollers to verify the feasibility of the proposed reflectarray. Simulated results show that the phase curve of the unit has good linearity and exhibit broadband characteristics. The maximum phase shift of the unit reaches about 200° at a center frequency of 16 GHz, which meets the requirement of a reflectarray with 1-bit phase quantization. Experimental results show that the gain of the proposed reflectarray is 17.7 dBi, with beam scanning range of ±50°. The proposed configurations can be used for a low-cost beam scanning antenna in wireless communication.