Volume 72, Issue 5-6 -

In this paper, a frequency reconfigurable antenna for 5 G/LTE/WWAN mobile terminal applications is presented. The proposed antenna consists of a radiation element which is folded on a dielectric cuboid. Four PIN diodes located on the antenna element are used for frequency reconfigration. By controlling the states of four PIN diodes with an 8-bit microcontroller, a broad band which can cover deca-band as LTE700/2300/2500, GSM850/900/1800/1900, UMTS 2100, WLAN2400 and the future 5 G or LTE3600 is obtained with a compacted size of 40×8×5mm 3 . The antenna gain, efficiency and radiation characteristics are also shown.

A printed antenna array consisting of 10 wideband symmetrical pentagonal dipoles is presented. The feed network of impedance transformers is employed to provide appropriate amplitude and phase distribution necessary to obtain flat top beam pattern. The measured results demonstrate excellent radiation characteristics including 38° flat gain region with maximum ripple of 3.5 dB at the centre frequency. Furthermore, the proposed antenna that is placed in corner reflector with angle of 60° has good gain (17 dBi) and side lobe suppression (18.9 dB). Although it is designed at the centre frequency f c =12 GHz, it was shown to be capable of shaping a good flat top radiation pattern within a fractional bandwidth at least 6 % of centre frequency. Also, proposed antenna features cheap, simple and easy fabrication that makes it suitable for mass production.

A new circularly polarized (CP) slot antenna with a small gap and a stick-shaped shorted strip is presented. The proposed antenna has a sufficient bandwidth for ultrahigh frequency (UHF) radio-frequency identification (RFID) reader applications. The antenna structure consists of a rectangular slot with a small gap, a stick-shaped shorted strip and a 50   Ω coplanar waveguide (CPW) feedline with an asymmetrical ground plane. By using the stick -shaped shorted strip to disturb magnetic current distribution on the slot, the CP radiation can be generated. The measured results demonstrate that the proposed antenna can reach a 10 dB return loss impedance bandwidth of 14.1 % (894–1030   MHz) and a 3 dB axial ratio (AR) bandwidth of 6.4 % (910–970   MHz). The whole antenna size is 80 × 80 × 1.6 mm 3 .

A novel frequency reconfigurable Quasi-Yagi antenna is proposed. The antenna has two dipoles on different layers of the substrate and they are fed by two coplanar striplines. Four PIN diodes, loading inside the coplanar striplines, are used as the switches. By switching the states of the four diodes, the antenna can work in three modes with different working bands around 3.5 GHz (cover the band of WiMAX), 5.2 GHz (cover the band of WLAN) and 7 GHz respectively. In addition, the working bands can be independently tuned by adjusting several parameters of the antenna. A prototype antenna was fabricated and tested. Good agreement between the simulation and the measurement is achieved. The results prove that the antenna can realize frequency reconfiguration effectively while maintaining the pattern characteristic of Yagi antenna at all frequency.

In this paper various shapes of DR antennas excited by common feed have been proposed and successfully implemented for wideband applications. Proposed structures are Hemispherical, Arrow-shaped and Triangular DRA, while common excited feed is inverted trapezoidal conformal patch. These shapes of DR offer significant optimization in several parameters such as impedance bandwidth, peak gain and bandwidth per unit volume of the antenna. By using inverted trapezoidal patch feed mechanism an impedance bandwidth (VSWR<2) of about 63 % for hemispherical shape, 66 % for arrow shape, and 72 % for triangular shape DRA has been achieved with maximum bandwidth per unit volume. Proposed wideband DRAs i. e. triangular, hemispherical, and arrow shapes of DR antennas cover almost complete C-band (4 GHz–8 GHz) frequency spectrum of microwave. The average peak gain within the operating band for hemispherical, arrow, and triangular shape DRA are about 5, 5.4, and 5.5 dB respectively. A comparative analysis of proposed structures for various antenna parameters has been analyzed by HFSS (High-Frequency Structure Simulator) and validated by experimental results.

By virtue of the excellent aerodynamic performances, conformal phased arrays have been attracting considerable attention. However, for the synthesis of patterns with low/ultra-low sidelobes of the conventional conformal arrays, the obtained dynamic range ratios of amplitude excitations could be quite high, which results in stringent requirements on various error tolerances for practical implementation. Time-modulated array (TMA) has the advantages of low sidelobe and reduced dynamic range ratio requirement of amplitude excitations. This paper takes full advantages of conformal antenna arrays and time-modulated arrays. The active-element-pattern, including element mutual coupling and platform effects, is employed in the whole design process. To optimize the pulse durations and the switch-on instants of the time-modulated elements, multiobjective invasive weed optimization (MOIWO) algorithm based on the nondominated sorting of the solutions is proposed. A S-band 8-element cylindrical conformal array is designed and a S-band 16-element cylindrical-parabolic conformal array is constructed and tested at two different steering angles.

In this paper, a compact low-pass filter (LPF) with wide stopband is proposed based on interdigital capacitor loaded hairpin resonator. The structure composed of an upper high-impedance transmission line, a middle interdigital capacitor, and a pair of inter-coupled symmetrical stepped-impedance stubs. Detailed investigation into this structure based on even-odd mode approach reveals that up to four transmission zeros can be generated and reallocated by choosing the proper circuit parameters. And owing to the aid of transmission zeros, the fabricated quasi-elliptic LPFs experimentally demonstrate a wide 20dB stopband from 1.4 fc to 5.1 fc using a compact size of only 0.005 λ g 2 .

A varactor-loaded half-mode substrate integrated waveguide (HMSIW) reconfigurable bandpass filter (BPF) is proposed in this paper. The proposed BPF is composed of complementary split-ring resonators (CSRRs) and varactors. Meanwhile, a nonmetalized via is employed in the center of the CSRR. It is noted that the varactor is embedded into the nonmetalized via, which can significantly reduce the tunable filter size. By changing the reverse bias voltage of the varactor, the resonant frequency of the proposed filter can be adjusted. Moreover, low insert loss (IL) and wide tuning range can be achieved. In order to validate its practicability, a BPF with the frequency ranging from 1.9 GHz to 2.5 GHz is fabricated and good agreement between the simulated and measured results is observed.

Differential bandpass filters (BPFs) named Filter A and Filter B based on Terminated Coupled Lines (TCLs) are proposed in this letter. The TCLs contributes to not only three poles in differential-mode (DM) for wideband filtering response but also multiple zeros in both DM and common-mode (CM) offering wide DM out-of-band rejection and good CM suppression. Fabricated filters centred at 3.5 GHz with wide DM passband and wideband CM suppression have been designed and measured. The filters improved the noise suppression capability of the communication and radiometer systems. The simulated and measured results are in good agreement.

A wideband bandpass filter (BPF) with an adjustable notched-band and high selectivity is proposed. The proposed BPF consists of a multi-mode resonator (MMR), two λ /2 resonators, and I/O feed lines with 50 ohm characteristic impedance. The MMR, connected as a whole by a wide stub, is composed of one I-shaped resonator and two open-loop resonators. Tightly coupling is built between MMR and λ /2 resonators. I/O feed lines are directly connected with two λ /2 resonators, respectively. Due to the use of tapped-line coupling, one transmission zero (TZ) is formed near low-edge of aim passband. High-edge of passband with one attendant TZ can be tuned to desired location by adjusting bottom-side position of used wide stub or bottom-side length of I-shaped resonator in MMR. The top-side length of I-shaped resonator is applied to improve upper stopband performance and shift undesired resonant mode of MMR near high-edge of aim passband to proper frequency point. The notched-band in aim passband is dominated by top-side position of wide stub in MMR. Good agreement is observed between simulated and measured results.

An ultra-wideband (UWB) bandpass filter with ultra-wide stopband based on a rectangular ring resonator is presented. The filter is designed for the operational frequency band from 4.10 GHz to 10.80 GHz with an ultra-wide stopband from 11.23 GHz to 40 GHz. The even and odd equivalent circuits are used to achieve a suitable analysis of the proposed filter performance. To verify the design and analysis, the proposed bandpass filter is simulated using full-wave EM simulator Advanced Design System and fabricated on a 20mil thick Rogers_RO4003 substrate with relative permittivity of 3.38 and a loss tangent of 0.0021. The proposed filter behavior is investigated and simulation results are in good agreement with measurement results.

A novel scheme of a shrunken Wilkinson power divider with harmonic suppression, using two identical resonators in the conventional Wilkinson power divider is designed. Moreover, the LC equivalent circuit and its relevant formulas are provided. To substantiate the functionality and soundness of design, a microstrip implementation of this design operating at 1 GHz with the second to eighth harmonic suppression, is developed. The proposed circuit is relatively smaller than the conventional circuit, (roughly 55% of the conventional circuit). Simulation and measurement results for the proposed scheme, which are highly consistent with one another, indicate a good insertion loss about 3.1 dB, input return loss of 20 dB and isolation of 20 dB, while sustaining high-power handling capability over the Wilkinson power divider.

This paper presents a multi segment capacitive level monitoring sensor based on distributed E-fields approach Glocal . This approach has an advantage to analyze build-up problem by the local E-fields as well the fluid level monitoring by the global E-fields. The multi segment capacitive approach presented within this work addresses the main problem of unwanted parasitic capacitance generated from Copper (Cu) strips by applying active shielding concept. Polyvinyl chloride (PVC) is used for isolation and parafilm is used for creating artificial build-up on a CLS.

We report on a W-band frequency-modulated continuous-wave (FMCW) radar module with fractional bandwidth over 10 %. To improve flatness over large operation bandwidth, the radar module is developed with focus on the 90–101 GHz modular transceiver, for which accurate modeling of Schottky diode in combination with an integrated design method are proposed in this work. Moreover, the nonlinearity compensation approach is introduced to further optimize the range resolution. To verify the design method and RF performance of the radar module, both measurements of critical components and ISAR imaging experiments are performed. The results demonstrate that high resolution in range and azimuth dimensions can be achieved based on the radar module, of which the receiving gain flatness and transmitting power flatness are better than ±1.3 dB and ±0.7 dB over 90~101 GHz, respectively.

Diffraction of theH $H$- polarized electromagnetic wave by the planar graphene grating in the THz range is considered. The scattering and absorption characteristics are studied. The scattered field is represented in the spectral domain via unknown spectral function. The mathematical model is based on the graphene surface impedance and the method of singular integral equations. The numerical solution is obtained by the Nystrom-type method of discrete singularities.

The evanescent wave re-construction performance in the time reversal system with periodic sub-wavelength grating is studied in this paper. Both the analysis and calculation results show that the evanescent components of the initial wave can’t be re-constructed directly by far field time reversal processing. The results indicate the uncertainty of the super-resolution performance of the time reversal technique with randomly arranged scatters. A new method to achieve super-resolution imaging by using evanescent-to-propagation wave conversion also been proposed at the end of this paper.

This paper assembles some information about white Gaussian noise (WGN) and its applications. It starts from a description of thermal noise, i. e. the irregular motion of free charge carriers in electronic devices. In a second step, mathematical models of WGN processes and their most important parameters, especially autocorrelation functions and power spectrum densities, are introduced. In order to proceed from mathematical models to simulations, we discuss the generation of normally distributed random numbers. The signal-to-noise ratio as the most important quality measure used in communications, control or measurement technology is accurately introduced. As a practical application of WGN, the transmission of quadrature amplitude modulated (QAM) signals over additive WGN channels together with the optimum maximum likelihood (ML) detector is considered in a demonstrative and intuitive way.