Analysis and improvement of HF circuits based on SIW and DGS technologies using iterative method

Recent demands for miniaturized, lightweight, high data rate, and reliable wireless devices motivated researches and designers of wireless systems to adopt the use of multiple input-multiple output MIMO antenna arrays with close proximity of each other. One of the difficulties is to overcome the problems associated with the low isolation between any two closely spaced antennas. The low profile, small size, ease of fabrication, and simplicity of design encourage the use of the IFA/PIFA antennas. In this paper, two vertical IFA antennas with close separation of λ o /15 ( o /2) fed by coaxial lines are combined in an array operating at the frequency of 2.5 GHz. The two antennas are deployed on a ground backed substrate of 50 mm × 50 mm in length and width respectively and a thickness of 1.524 mm with a relative permittivity, e r of 10.2. Each IFA consists of a monopole as the main radiator with a length of 38 mm and a diameter of 1.22 mm placed 11 mm above the ground plane. The separation between the feeding point and the grounded end of the radiating element is 10 mm. The consequence of positioning the antenna in the proximity of each other is the high mutual coupling. To decrease the resulted effects, a new Defected Ground Structure (DGS) has been proposed. A rectangular slot of 32 mm and width of 1.5 mm with a strip line of 29 mm in length and a width of 1 mm have been introduced to the ground plane. The final proposed array with the DGS is shown in the attached figure. The Defected Ground Structure (DGS) has the effect of reducing the interaction between the antennas, main radiators, by restricting the current flow in the ground plane. A parametric study has been carried out to obtain the optimum dimensions of the structure using Ansys High Frequency Structure Simulator (HFSS). The S-Parameters of the design are shown in the enclosed figure. The antenna has an operating frequency of 2.5 GHz. A total isolation level of -22 dB has been achieved by the proposed structure at the operating frequency. The array with the proposed ground structure provides a gain of 3.9 dB at 2.5 GHz when the two ports are excited. This structure is a good candidate for reducing the mutual coupling between two vertical IFA for application utilizing MIMO techniques.

A novel triple-band Defected Ground Structured (DGS) meandered monopole antenna is presented in this paper. In the proposed antenna, three vertical and one horizontal protrudent strips are employed onto ground plane to increase the bandwidth. High Frequency Structure Simulator (HFSS) software based on Finite Element Method (FEM) is used to attain the performance parameters of proposed antenna. The simulated results of triple-band proposed antenna cover the required bandwidths of the PCS-1900/UMTS-2100 and the 2.4/5.2/5.8 GHz WLAN standards. Keywords: Microstrip Patch Antenna (MPA), Defected Ground Structure (DGS), Triple Band, Peak Gain and Peak Directivity, Bandwidth (B.W.), Return Loss (S11), Voltage Standing Wave Ratio (VSWR).

: This paper presents a two element microstrip antenna array using trapezium shape defected ground structure (DGS). The DGS is inserted in the ground plane between two elements of antenna array. Insertion of the DGS is intended to suppress the mutual coupling effect produced by antenna array. Simulation and measurement results were taken and compared between antenna array with and without DGS. Measurement results show that the antenna with DGS compared to antenna without DGS can suppress mutual coupling effect to 7.9 dB, improve the return loss to 33.29% from -30.188 dB to -40.24 dB and axial ratio bandwidth enhancement to 10 MHz. This bandwidth enhancement is achieved from frequency 2.63 GHz – 2.67 GHz for antenna without DGS and from frequency 2.63 GHz – 2.68 GHz for antenna with DGS. In addition, the DGS antenna also improved the antenna gain to 0.6 dB. The results show that the implementation of the trapezium DGS can improve the radiation properties of the antenna without DGS.

The aim of this work is to enhance the intrinsic performance of a circular microstrip patch antenna, using two optimization techniques, widely used nowadays in antenna field, due to their promising features of improving gain, directivity, and return loss. The first one consists on incorporating a periodic DGS (Defected ground Structure) in the ground plane of the proposed antenna , while the second method involve adding double EBG dielectric superstrate atop of the patch. The proposed antenna is designed to operate in the millimeter wave band, more exactly at 30GHz, formulated using cavity model, and its behavior has been explained using an EM-simulator, based on finite element method: HFSSv15(High Frequency Structure Simulator).

ABSTRACTIn this article, the performance of compact planar wearable antenna 4.1 × 4.1 cm2 mounted on different phantoms and human body fed by microstrip line is designed to operate in ultra‐wide band applications. The proposed antenna consists of a circular patch with notch‐cut and U‐shaped slot on the upper side of the substrate and finite ground plane with rectangular shape defected ground structure (DGS) on the lower side. The U‐shaped slot and finite ground plane are used to achieve an enhanced impedance bandwidth. The proposed antenna is designed and simulated using Ansoft High Frequency Structure Simulator (HFSS) to verify its operation over larger frequency range from 3.6 GHz to 15 GHz. The return loss, VSWR, radiation pattern, and gain are investigated in this article and verified with the experimental measurements. The proposed wearable antenna radiates over a wide frequency band and can achieve nearly omnidirectional radiation patterns with an average gain of 3.11 dBi. A good agreement between simulations and practical measurements can be achieved in order to verify the suitability of proposed wearable antenna to be used in various UWB applications. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2531–2536, 2016

In this paper, an investigation on compact microstrip low-pass filters (MLPFs) with extremely perfect low-pass characteristics and improved out-band suppression has been carried out for the improvement of the selectivity parameter ([Formula: see text]). For this purpose, two different defected ground structures (DGSs) based on Moore fractals and Meander line have been designed and experimentally validated. The proposed third-order low-pass filter (LPF) configurations are designed and simulated using the High-Frequency Structure Simulator (HFSS). To validate the simulation models, the prototypes of the suggested low-pass filters are fabricated using Teflon (TM) substrate having a relative permittivity of 2.65 and a loss tangent of 0.001, and measured using the Vector Network Analyzer. The simulation and measurement results are in good agreement. The proposed filters occupy a compact size of [Formula: see text]. The selectivity parameter values for the proposed Moore fractals- and Meander line-modeled DGS-based LPFs are 425[Formula: see text]dB/GHz and 850[Formula: see text]dB/GHz, respectively. The proposed microstrip low-pass filters offer a significant improvement in the selectivity parameter, offering a maximum value of 850[Formula: see text]dB/GHz. The proposed filters exhibit a very high figure of merit (FOM), reporting 71,335 for Moore fractals-based LPF and 118,354 for the Meander line-based LPF. These proposed filters are suitable for advanced mobile phone services, [Formula: see text]-band radar, Global Positioning System, mobile, paging services, Wi-Fi, Bluetooth and wireless LAN.

A Microstrip Patch antenna with two operating frequencies for radar application is presented. The antenna is modeled to resonate at two frequencies in X-band. The X-band frequency range lies between 8 to 12 Gigahertz and are mostly used in radar applications. The design consists of Defected Ground Structure (DGS) provided to improve the antenna performance. The dielectric substrate used by the antenna is of low cost FR4 (Flame Retardant) Epoxy. The Ansoft High Frequency Structural Simulator (HFSS) Version 12 software is used to analyze the results. The parameters like gain, return loss, directivity and bandwidth are discussed in the paper. With 9.19 GHz and 10.82 GHz as the resonant frequencies, a return loss of -22.91 dB and -40.99 dB is obtained with 540 MHz and 1600 MHz as the bandwidth respectively.

Bandstop filters play an essential role in many radio frequency (RF) and microwave communication systems to block undesired signals or reject spurious harmonics. This paper presents the design and experiment of a compact quadband bandstop filter centered at 1.2/1.97/2.96/4.78 GHz with a passband insertion loss ranging from 1.07 to 2.9 dB. The overall volumetric size of the proposed filter is 0.197 λ g × 0.197 λ g × 0.01 λ g , where λ g is the guided wavelength at 1.2 GHz. The desired performance is achieved by introducing two diamond-shaped concentric split ring resonators (DSCSRRs) intercoupled and defected ground structure. The metamaterial properties of the DSCSRR have been verified by extracting and analyzing its effective permittivity and permeability. This research shows that DSCSRRs can generate multiband characteristics and yield high selectivity with good band-to-band isolation by generating transmission zeros between passbands. The filter is designed, optimized, and analyzed using High-Frequency Structural Simulator (HFSS). A good agreement is observed between simulated and experimental results. The measured results demonstrate that the proposed quadband banstop filter exhibits a minimum stopband rejection of 11.22 dB and fractional bandwidth greater than 4.51%, which makes it suitable for front-end transceiver components or multifunctional wireless systems to suppress unwanted signals at four separate frequency bands.

This article proposes the design, fabrication and measurement of a triple-rings complementary split-ring resonator (CSRR) microwave sensor for semi-solid material detection. The triple-rings CSRR sensor was developed based on the CSRR configuration with curve-feed designed together, utilizing a high-frequency structure simulator (HFSS) microwave studio. The designed triple rings CSRR sensor resonates at 2.5 GHz, performs in transmission mode, and senses shift in frequency. Six cases of the sample under tests (SUTs) were simulated and measured. These SUTs are Air (without SUT), Java turmeric, Mango ginger, Black Turmeric, Turmeric, and Di-water, and detailed sensitivity analysis is conducted for the frequency resonant at 2.5 GHz. The semi-solid tested mechanism is undertaken using a polypropylene (PP) tube. The samples of dielectric material are filled into PP tube channels and loaded in the CSRR centre hole. The e-fields near the resonator will affect the interaction with the SUTs. The finalized CSRR triple-rings sensor was incorporated with defective ground structure (DGS) to deliver high-performance characteristics in microstrip circuits, leading to a high Q-factor magnitude. The suggested sensor has a Q-factor of 520 at 2.5 GHz with high sensitivity of about 4.806 and 4.773 for Di-water and Turmeric samples, respectively. The relationship between loss tangent, permittivity, and Q-factor at the resonant frequency has been compared and discussed. These given outcomes make the presented sensor ideal for detecting semi-solid materials.

A compact and low-profile curve-feed complementary split-ring resonator (CSRR) microwave sensor for solid material detection is presented in this article. The curve-feed CSRR sensor was developed based on the CSRR configuration with triple rings (TRs) designed together, utilizing a high-frequency structure simulator (HFSS) microwave studio. The designed curve-feed CSRR sensor resonates at 2.5 GHz, performs in transmission mode, and senses shift in frequency. Four varieties of the sample under tests (SUTs) were simulated and measured. These SUTs are Air (without SUT), Roger 5880, Roger 4350, FR4, and detailed sensitivity analysis is being performed for the resonant band at 2.5 GHz. The finalized CSRR curve-feed sensor was integrated with defective ground structure (DGS) to deliver high-performance characteristics in microstrip circuits, which leads to a high Q-factor magnitude. The presented curve-feed sensor has a Q-factor of 520 at 2.5 GHz, with high sensitivity of about 1.072. The relationship between loss tangent, permittivity, and Q-factor at the resonant frequency has been compared and discussed. These disseminated outcomes make the suggested sensor ideal for characterizing solid materials.

An inset fed slotted rectangular microstrip antenna is proposed and researched in this paper using Photonic Band Gap (PBG) substrates with Defected Ground Structure (DGS). Rogers RT/duroid 5880 (tm) which is utilized as substrate material whose dielectric steady is 2.2. Firstly, using HFSS software, a normal rectangular microstrip patch antenna is designed and its contribution is noticed. Secondly, on the patch, many circular slots with equal distance and diameter are made. Thirdly, many circular air holes are created on the slotted rectangular microstrip antenna’s substrate with equal distance and diameter to present PBG substrate and afterwards the performance of that antenna is noticed. Finally, by making circular defects of equal distance and diameter on the ground plane of previously designed antennas, DGS is generated. This antenna gets the best exhibitions among the past three designed. The proposed antenna's return loss, bandwidth, gain and directivity are -38.7 dB, 441.7 (5.0556- 5.4973GHz) MHz, 9.0828 dBi and 9.2161 dBi respectively. At a frequency of 5.2765 GHz, which can be used as C-band satellite applications, the proposed antenna is resonated.

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.

The design of planar filter using stepped impedance type distributed synthesis has been proposed for 8.6–9.5 GHz frequency band. To improve the return loss characteristics, instead of using traditional defected ground structure (DGS), the combination of fractal geometry and DGS, known as ‘fractal DGS’ has been embedded in the ground plane of the filter. The filter using fractal geometry gives 65% better return loss as compared to filter without DGS. Three laboratory prototypes (without DGS, first iteration DGS and second iteration DGS) have been developed to validate the simulated and measured results. The measured results are agreed with simulated one.

The novel technique of band rejection design of Chebyshev dumbbell EBG assisted low pass filters (LPFs) is presented in this paper. The ground plane of a standard 50-ohm transmission line is perturbed by dumbbell electromagnetic bandgap structure (EBG) or called defected ground structure (DGS) to generate ultra rejection band that is beneficial to higher order harmonic suppression. The purpose of the paper is to develop a method to calculate band rejection dependent filling factor (FF) of a Chebyshev modulated dumbbell DGS physical dimension through the use of predefined side lobe level (SLL) rejection ratio, Bragg's theory and Chebyshev polynomial. Unlike that of circular and rectangular EBG cells, the filling factor of dumbbell shaped DGS has been re-defined. The rejection trend under re-defined FF is consistent with the pre-defined SLL. A comparison of Chebyshev circular EBG LPF and proposed Chebyshev dumbbell DGS has been evaluated. The proposed dumbbell DGS LPF has better rejection bandwidth than circular EBG LPF.

This paper presents the effects of defected ground structure (DGS) on different ground planes in RF power amplifiers (PAs). Two DGS patterns etched on the front and back planes of printed circuit board which are named Top-DGS and Bottom-DGS, and a thru microstrip line are manufactured and measured to compare the insert loss at the fundamental and second harmonic frequencies. In order to evaluate the effects of the Top-DGS, Bottom-DGS and without DGS on the PA, three 4W PA have been designed and measured. Measured results show that the PA with the Top-DGS can reject the second harmonic about 13dB at Pout 34.76dBm, and achieve better the output power (Pout) and power added efficiency (PAE) than the one without DGS; the one with the Bottom-DGS has the suppression of about 28dB for the second harmonic at Pout 34.21dBm, and has less the Pout and PAE for the decreased characteristic impedance (Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> ) of DGS pattern.