Search

Two broadband dual-polarized band-notched crossed dipole antennas based on the grounded coplanar waveguide (GCPW) filter for 2G/3G/4G/5G base station are proposed in this paper. Two antennas with two and three radiation nulls are displayed to demonstrate the design innovation. Firstly, a wideband crossed dipole antenna with GCPW feed structure is designed, and its coverage frequency is 1.7-3.6 GHz. Then, a compact GCPW second-order hybrid bandstop filter is designed using defected ground structure (DGS) and defected microstrip structure (DMS). The DGS-DMS filter are embedded inside the antenna radiator to achieve the stopband covering 2.9-3.1 GHz with only one dielectric substrate. At last, a miniaturized GCPW third-order DGS-DMS highly selective bandstop filter is integrated in wideband antenna to realize the stopband of 2.87-3.17 GHz. The proposed band-notched antenna uses only one substrate. Compared with the antenna using second-order filter, the antenna using third-order filter has one more radiation null, wider stopband of 2.87-3.17 GHz and higher selectivity.

In this paper, a compact matryoshka DGS using dielectric resonator (DR) is proposed. Despite the use of dielectric resonators to obtain band-stop frequency response not being a new idea, the proposed compact matryoshka DGS is an original contribution, since only recently the matryoshka geometry was used in DGS applications. Furthermore, a numerical analysis of the positioning of the DR is presented, which makes it possible to determine the region of the DGS for which the minimum resonant frequency is reached, and the resonant frequency range that can be obtained. To the best of the authors’ knowledge, this numerical analysis is an unpublished result, even more so, for the matryoshka DGS. The matryoshka geometry was described, including initial design equations. To verify the expected characteristics (miniaturization, selectivity, and resonant frequency tunability), two compact matryoshka DGSs (DGS1 and DGS2) were designed using a high permittivity ceramic (MCT-115) as DR. The obtained numerical and experimental results showed good agreement, and the initial design equations proved to be applicable, which allows new dimensions to be determined for other resonant frequencies, according to the application requirements. Resonant frequencies ranging from the maximum value to 33% (DGS1) and 27% (DGS2) were achieved, depending on the DR position. Considering $\lambda _{0}$ the wavelength in free space, corresponding to the resonant frequency, DGS1 and DGS2 achieved an occupied area of $0.04\lambda _{0}\times 0.04\lambda _{0}$ , and $0.05\lambda _{0}\times 0.05\lambda _{0}$ , respectively, a good miniaturization. The proposed compact matryoshka DGS may be especially attractive for applications that require a very selective band-stop frequency response. If a wider band-stop is required, the proposed DGS can be cascaded.

This work envisioned presenting a novel compact boat-shaped dual-band Multiple Input- Multiple Output (MIMO) antenna for isolation enhancement of 5G/WLAN application. Each identical rectangular patch consists of stubs, a defective ground structure and a split ring resonator placed on a defective ground plane to generate 2.32 GHz and 5.2 GHz for dual-band operation and make a low profile. The MIMO antenna design is challenging due to size constraints and mutual coupling. The 2-port MIMO antenna is realized using the diagonal deployment of symmetric radiators on an FR-4 substrate, consuming an entire size of $2103.93\,\,mm^{2}\times 1.6$ mm. The impedance bandwidth is enhanced by incorporating a shorting pin, covering 2.22 to 2.42 GHz (200 MHz) and 5.142 to 5.706 GHz (564 MHz). Meanwhile, to overcome the mutual coupling effects and improve isolation, an innovative hybrid decoupling structure (ladder-shaped slot and neutralization line) is introduced between the bottom and top of radiating elements. It suppresses the surface waves with maximum isolation better than −46 dB & −45 dB at 2.32 GHz and 5.2 GHz, respectively. Furthermore, the MIMO performance metrics, such as envelope correlation coefficient (< 0.001 dB) and diversity gain (>9.99 dB), are analyzed. The diversity performance results demonstrate that the MIMO antenna is apt for 5G / WLAN terminal devices.

A ten-elements MIMO antenna with improved isolation and reduction of X-polar radiation (XPR) in millimeter (mm) wave region of n258 (24.25-27.5 GHz) is presented. The individual antenna element consists of stub loaded coplanar waveguide (CPW) structure with elliptical shaped radiator. Elliptical shaped Defected ground structure (DGS) has been incorporated at ground to reduce the mutual coupling effect between the adjacent antenna pairs and the minimum isolation obtained 35 dB. The backside of the substrate has a metallic plane with defects which is not connected to the coplanar ground of the antenna and it acts as a reflector to improve the radiation characteristics by lowering of XPR as well as improving the co-pol to X-pol isolation up to 20 dB and 28 dB in the boresight direction in both the XZ and YZ planes respectively. The diversity performances in terms of Envelope Correlation Coefficient (ECC), Diversity Gain (DG) and Channel Capacity Loss (CCL) are obtained as $0.1\times 10^{-6}$ , 10 dB and 0.005 bps/Hz respectively which are within the acceptable limits. Mean effective gain (MEG) values with respect to the excited port 2 and port 3 is identical and approximately −3 dB and the multiplexing efficiency of the proposed MIMO antenna is satisfactory over the bandwidth. The group delay is investigated and found to be almost constant with a variation of 1.2 ns thus indicating linear phase characteristic of the antenna. The proposed structure is compared with other mm-wave MIMO antennas and found to be advantageous. A prototype of the proposed 10-elements MIMO is fabricated, and the measured results resemble with the simulated results.

A low-profile printed six-port ultrawideband (UWB) antenna with a novel decoupling structure for enhancing port-to-port isolation is analyzed in this paper. Six symmetrical pyramidal form UWB antennas with defective ground structures interspersed with parasitic components served as a unique decoupling structure in the proposed design. The grounded branches and modified rectangular stubs on the ground plane generate closed and open current distribution channels, causing the uniform current flow to be disrupted and the coupling effect to be neutralized. The projected six-port antenna has an electrical dimension of $0.68\times 0.89 \times 0.01\,\,\lambda ^{3}$ ( $\lambda $ is computed using a lower frequency of 2.9 GHz), having a below -10 dB impedance bandwidth of 116% from 2.9 to 11 GHz. Across the impedance bandwidth, the average port-to-port isolation is better than 20 dB. The antenna design has acceptable radiation properties with a peak gain of 8.3 dBi at a frequency of 7.5 GHz. Further, the projected design is also exposed to the time domain characteristics and diversity metrics. Among the different ports, the values of the group delay and fidelity factors are less than 1.5 ns and more than 0.92, correspondingly. The values of the diversity parameters such as ECC < 0.075, DG approximately 10 dB, MEG $ < -3$ dB, TARC $ < -10$ dB, CCL < 0.3 bps/Hz, and ME $ < -2$ dB ensure that the projected design is appropriate for the MIMO applications. The designed antenna is fabricated and measured, and the results are in line with the simulation.

In this article, the significance of engineered ground planes in microstrip antennas and the effects of various configurations for the enhancements of the characteristics like isolation, cross-polarization levels, bandwidth and size reduction are vividly analyzed. These defects are classified and compared based on different applications and some important conclusions have been derived to infer a clear idea about their implementations as well as design considerations. The basic objective of this article is to motivate the readers and make them understand how this simple technique can be utilized to achieve various complex requirements of antennas needed for many contemporary as well as upcoming technologies like 5G, massive MIMO, IoT and millimeter-wave communications by taking care of all the above parameters.

This paper presents two different antenna modules at two different bands with a compact size structure that is used for both of mm-Wave and microwave bands, with the objective of keeping the size as minimum as possible. The presented structure consists of two integrated modules with overall dimensions of 24 $\times 15\times0.787$ mm3 and is implemented on a Rogers RT5880 substrate. The first module is designed to resonate at 25.75 GHz with bandwidth of 4.15 GHz. The length of this module is taken as a constraint in designing the second module, which is the microwave one. This module is designed to have resonance frequency of 5.45 GHz with bandwidth of 1.12 GHz. The two modules are etched on the same substrate in an integrated fashion to give the required structure with two separate feeds and a separation gap between them in the ground plane. The proposed antenna structure is simulated using the CST-MW studio simulator, where it is found that for the mm-Wave module, the band’s gain is 5.58 dBi and the efficiency is 0.87 at 25.75 GHz. As for the microwave module, the gain is 2.45 dBi and the efficiency is 0.77 at 5.45 GHz. The proposed structure is implemented practically and the relevant measures agree with the simulated ones. A comparison of the proposed structure with other designs available in literature shows that it exhibits the minimum size among them, while keeping the other parameter values of comparable orders. The proposed structure is suitable for being used in 5G applications where both of the microwave and millimeter- wave bands are utilized.

This paper studies the electromagnetic properties of defected ground structure (DGS) with von Koch snowflake fractals. First, the snowflake fractal is employed in the dumbbell shaped DGS, and we have discovered that it has the characteristics of a low-pass filter and the out-of-band rejection increases with fractal iterations. In consideration of fabrication accuracy and performance, the third iteration has been adopted. Based on this structure, we have designed a narrow-band filter and a wide-band filter to verify our theory. From the simulated and measured results, we can see that the out-of-band rejection level has been greatly improved. The proposed structure can be applied in communication planar circuits.

In this paper we present the design and fabrication of a two-antenna array to resonate at 5.8 GHz, a frequency that satisfies a host of applications, especially those associated with the ISM band, but including IoT applications. The design incorporates several techniques to improve figures of merit and reduce its size. The array presents a measured bandwidth of 617 MHz (from 5.503 to 6.120 GHz, or 10.63% about the central frequency) when built on a thin substrate, and of 455 MHz (from 5.517 to 5.972 GHz; 7.84%) when fabricated using a thicker one. The simulated gains were of 6.89 dBi and 7.63 dBi, whereas the measured ones were 6.7 dBi and 7.2 dBi, respectively. Size reduction is better than 30% and the simulated efficiencies are higher than 90%.

This paper presents a new design to broaden polarization conversion ratio (PCR) bandwidth utilizing reflective surfaces. The proposed design is based on anisotropic surfaces for linearly polarized electromagnetic waves. The combination of a traditional two-corner-cut square patch and a two-layer substrate with defected ground structure contributes to PCR bandwidth expansion and size reduction. The experimental results indicate that PCR fractional bandwidth is higher than 121% in 5.4-22 GHz band for both x- and y-polarized waves and the conversion efficiency is greater than 90%. In addition, the proposed structure is approximately robust under oblique incidences, which verifies the applicability of the structure in a practical environment. The experimental results are in excellent agreement with simulated ones. The reflective surface with wideband PCR can be utilized in various practical applications, such as radiometer, reflector antennas, remote sensors, and imaging sensors.

This paper proposes a fault-section location method based on sparse measurements, aimed at asymmetrical faults. A virtual current vector is defined to indicate the faulted section, which is sufficiently sparse except that the fault position corresponding entries are nonzero. To simplify the algorithm, the virtual vector is fixed by amplitudes of voltages and impedances and the feasibility is demonstrated. The Bayesian Compressive Sensing theory is introduced to reduce the number of required intelligent electronic devices (IEDs). In addition, the minimal number of IEDs and their allocation are discussed. The performance of the proposed method is validated in a 69-bus, 12.66-kV distribution system with six distributed generations (DGs) in response to various fault scenarios. The simulation results show that the method is robust for single-phase, double-phase, and double-phase to ground faults with high resistance under noisy condition. Furthermore, the method is applicable for networks with inverter interfaced DGs. [ABSTRACT FROM AUTHOR]

This paper proposes a fully decentralized multi-agent system (MAS) based technique for service restoration of radial distribution networks. The technique utilizes expert system rules and considers the customers’ priority and the presence of distributed generators (DGs). It also considers the operational constraints in both healthy and restored sections of the feeder. The technique relies on one type of agents only, hence, simplifying its implementation. Moreover, it allows for assigning a back-up decision making agent to improve the reliability of the restoration process. The effectiveness of the technique is validated through several case studies simulated on an 11 kV distribution feeder. The agents are implemented in Java Agent Developing Framework (JADE) environment for communications and decisions making. Power flow calculations are performed in MATLAB environment to validate the correctness of the agents’ decisions. [ABSTRACT FROM PUBLISHER]

In this paper, application of a defected ground structure in realization of 1-D and 2-D microwave displacement sensors is presented. A coplanar waveguide (CPW) line with two slots along the line that generate a transmission zero (TZ) in the transmission response is printed on a fixed substrate. A metallic patch is also printed on the bottom face of a movable substrate located on the fixed substrate. By moving the upper substrate, the length of the etched slots on the fixed underneath substrate changes, and hence, the TZ shifts proportionally. The displacement can be measured based on the frequency shift of the TZ. The 2-D displacement sensor has a similar structure with two additional slots perpendicular to the CPW line on the signal trace. The parallel and perpendicular slots generate two separated TZs in two different frequency bands. The proposed 2-D displacement sensor uses the frequency range of 2.8–4.2 GHz to measure the horizontal displacement with the high sensitivity of 0.41 GHz/1 mm and the frequency range of 5.7–8.8 GHz to measure the vertical displacement with the high sensitivity of 1.2 GHz/1 mm. In comparison with the previous works, the displacement measurement in each direction is independent of the other one. Furthermore, since TZs show narrow notch-frequency bands with high and fixed rejection levels (high $Q$ -factor resonator), independent of the measured displacement, the measurement error is minimized. Also, the dynamic range of the sensor is wide and almost has no intrinsic geometrical limitation. The 2-D sensor is fabricated and tested. The measured results show good agreement with the simulated results. [ABSTRACT FROM PUBLISHER]

The current-controlled grid-connected inverter with LCL filter is widely used in the distributed generation system (DGS), due to its fast dynamic response and better power quality features. However, with the increase of power injected into the grid, control performances of the inverter will be significantly influenced by the nonideal grid conditions. Specifically, the possible wide variation of the grid impedance challenges the system stability. Meanwhile, background harmonics of the grid can greatly distort the injected current. Therefore, the control of the inverter should be designed with strong stability-robustness and high harmonic-rejection-ability, both of which correlate closely with the inverter output impedance. However, it is difficult to shape the output impedance into the one with a desirable characteristic simply by adjusting the current loop gain. In this paper, an impedance shaping method is proposed with virtual impedances, and the current control loop can be designed independently. The implementation and parameter design of the virtual impedances are studied under the practical considerations. With this proposed method, the grid-connected inverter can work stably over a wide range of the typical inductive-resistive grid impedance and exhibit strong rejection ability of grid-voltage harmonics. Experimental results from a 6-kW single-phase grid-connected inverter confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

We propose a new analysis method to determine the bandgap characteristics of an electromagnetic bandgap structure with a defected ground structure (DGS). The proposed method is based on a 1-D segmented transmission line model and a piecewise linear approximation of Zo within a unit cell. Although the previous method is only applicable to rectangular DGSs (RDGSs), the proposed method is applicable to any DGS shapes. As an example, the proposed method is applied to a circular DGS and shows a good agreement with full-wave simulations of the unit cell and measurements of 11\,\times\,11 unit cells. The circular DGS achieves a 15% improvement in the stopband bandwidth over the RDGS with the same perforation area. The proposed method allows us to explore a variety of DGS shapes in the search for better stopband characteristics. It also offers the basis for numerical optimization techniques to be used in synthesizing DGS shapes to meet required stopband characteristics. [ABSTRACT FROM PUBLISHER]

In this letter, a new Doherty power amplifier having the ideal harmonic termination condition that has been usually ignored is proposed. A defected ground structure (DGS) is adopted on the ground pattern of the output lambda/4 impedance inverter of the carrier amplifier and output offset transmission line of the peaking amplifier that are essential for proper load modulation operation of a conventional Doherty amplifier. As a result of the second and third harmonic termination, excellent improvement in power added efficiency (PAE), gain, maximum output power as well as linearity is obtained. The acquired improvements in gain, maximum output power (P1 dB), PAE, and adjacent channel leakage ratio to wideband code division multiple access 2FA signal are 0.33 dB, 0.42 dB, 12.7%, and 5.1 dB, respectively. Moreover, physical length of microstrip line is shortened fairly by DGS, therefore the whole amplifier circuit size is considerably reduced [ABSTRACT FROM PUBLISHER]

A novel design of frequency doubler using feedforward technique and defected ground structure (DGS) is proposed. The feedforward loop in the proposed frequency doubler suppresses the fundamental component (fo), and the DGS diminishes the higher order harmonics such as third, fourth, and so on. Due to the combination of feedforward structure and DGS, only the doubled frequency component (2fo) appears at the output port and the other unwanted components are suppressed excellently. A frequency doubler is designed at 1.85GHz of fo by the proposed technique and measured. The measured output power of 2fo is -3 dBm when the input power is 0 dBm. The obtained suppression of fo, 3fo, and 4fo are 42.9, 19.2, and 29.7dB, respectively. [ABSTRACT FROM PUBLISHER]

This letter is to present a new defected ground structure (DGS), which is useful for mounting an active device, and its application to a microwave oscillator. The newly proposed DGS circuit is useful for mounting a transistor such as a BJT or field effect transistor (FET) on ground plane. In order to bias dc to a transistor, it is necessary to implement the dc isolated circuit in a practically applied active device with a DGS. For dc isolation, each branch of DGS should be isolated from ground. However, the proposed DGS structure with dc isolations introduces a degradation of gain performance for a transistor and changes the matching point. In order to overcome these limits, we have investigated a coupling method by using the simple coupling capacitor without degradations in RF performances. This letter displays the comparison of several measurements for the fabricated DGS circuits including the case that compensates the degradations due to the dc isolation. Furthermore, a design example of a microwave oscillator with the proposed DGS is demonstrated to show the validity of this letter. [ABSTRACT FROM PUBLISHER]