Dumbbell Defected Ground Structure Research Articles

DGS Based CP Antenna for 5G Communication with Harmonic

Higher harmonics in antennas contribute to negative effects on antenna performance such as interference, radiation pattern distortion, impedance mismatch and increased complexity in design, commonly occurring in RF communication systems caused by the non-uniformity of the antenna structure and the presence of parasitic elements. Therefore, a patch antenna operating at 3.65GHz for 5G mobile communication that incorporates techniques to suppress unwanted higher harmonics is presented. The antenna design employs a basic rectangular patch antenna with an inset feed technique to enhance the S11 parameters at the resonant frequency. Additionally, two dumbbell defected ground structures (DGS) are employed to minimize the higher modes of harmonic distortion. To transform the antenna into a circular polarized (CP) antenna, two truncated corners and a cross slot perpendicular to the middle of the patch are introduced. The proposed antenna is able to suppress unwanted harmonics at higher resonances, demonstrating its effectiveness in mitigating harmonic distortion

Dual‐band balanced‐to‐single‐ended crossover based on composite right‐ and left‐handed transmission lines

This Letter presents a balanced-to-single-ended (BS) crossover for dual-band applications by using two rings included of composite right- and left-handed (CRLH) transmission lines (TLs) with controllable frequency ratio feature. Two dumbbell defected ground structures (DGSs) are employed through balanced TLs to suppress out-of-band common-mode. Theoretical analysis expresses that the frequency ratio can be controlled by suitable selecting of the element values and the number of designing cells of the CRLH TLs. Furthermore, desired impedances and electrical lengths of DGSs are obtained at the frequency of common-mode rejection by using even- and odd-mode analyses. To validate the proposed structure, a dual-band BS crossover operating at 1.8 and 4.2 GHz is fabricated. Measurement results show that the fabricated proposed structure has good performance at the designed frequency bands.

A Miniature Microstrip Antenna Array using Circular Shaped Dumbbell for ISM Band Applications

The aim of this work is the achievement, and the validation of a small microstrip patch antenna array using a circular shaped dumbbell defected ground structure. This work has been dividing into two stages: The first step is to miniaturize a microstrip patch antenna resonating at 5.8GHz, which operate in the Industrial Scientific Medical band (ISM) and the second is to use a circular defected ground structure to shift the resonance frequency of the antenna array from 5.8GHz to 2.45GHz. At last, a miniaturization up to 74.47%, relative to the original microstrip antenna array has accomplished. The antenna structure has designed, optimized and miniaturized using CST MW Studio. The obtained results have compared with Ansoft’s HFSS electromagnetic solver. The antenna array has fabricated on FR-4 substrate, and its reflection coefficient is measured.

Experimental design of bandstop filters based on unconventional defected ground structures

ABSTRACTA modified design of band stop filters using unconventional defected ground structures (DGS) is presented. The new proposed structures have conventional dumbbell DGS and spiral DGS integrated with U‐slots. These microstrip structures provide high selectivity and Q‐factor. By integrating the U‐slot to the conventional structures, the overall capacitance and inductance increase which results in shift of resonance frequency from3.434 GHz to2.323 GHz for modified dumbbell and from 1.818 GHz to 1.702 GHz for modified spiral structure. Sharp transition is achieved from pass band to stop band and reduced ripples in the pass band for the new proposed DGS while the DGS sizes remain the same. The proposed designs were fabricated and tested on a dielectric substrate with dielectric permittivity of 10. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2969–2973, 2016

Design of microstrip lowpass-bandpass quintuplexer

This paper presents a novel lowpass-bandpass multiplexer consisting of one lowpass channel and four bandpass channels. Dumb-bell defected ground structures and stepped impedance resonators are employed to extend the stopband of the lowpass filter and bandpass filters, respectively. Stepped impedance stubs are used to bring a sharp selectivity in the lowpass channel design. Good isolation between channels is obtained by careful design of the input signal splitting structure, which is realized by utilizing four shunt open stubs with electric length of quarter-wavelength at the center frequency of the four bandpass channels, respectively. To verify the above concept, a lowpass-bandpass quintuplexer is designed, fabricated, and measured. The cut-off frequency of the lowpass filter is selected to be 1 GHz. The central passband frequencies are chosen to be 2.4, 3.5, 4.6, 5.8 GHz. Experimental measurements are in good agreement with simulations.

Design of compact balanced ultra‐wideband bandpass filter with half mode dumbbell DGS

A new compact balanced ultra-wideband (UWB) bandpass filter using half mode dumbbell defected ground structure (DGS) is presented. To realise the UWB response, the `T' shape multiple-mode resonator with short-ended stub is employed. To achieve wideband common mode (CM) suppression and compact design simultaneously, the concept of half-mode DGS is introduced in the two stacked microstrip layers. Afterwards, a balanced UWB filter is designed and measured for verifying the feasibility of the presented design method. The measured results match well with the expected results which indicate the proposed filter exhibits better than -30 dB CM suppression within the DM passband covering from 3.1 to 10.6 GHz.

An improved parameter extraction scheme for dumbbell shaped defected ground structure

The present study proposes an improved scheme for parameter extraction of dumbbell shaped defected ground structure (DGS). A dumbbell DGS has similar kind of response like a single pole LC–Butterworth filter. There are L–C, R–L–C, π and quasi-static equivalent circuits available in literature for dumbbell DGS parameter extraction. In this article, the R–L–C equivalent of dumbbell DGS is re-formulated which provides better accuracy in parameter extraction and it is confirmed through simulation and experimental analysis. This improved model is finally used to extract R–L–C parameters against several structural variations of dumbbell DGS unit cell.

High-Selectivity Low-Pass Filters With Ultrawide Stopband Based on Defected Ground Structures

Compact microstrip low-pass filters (LPFs) with ultrawide stopband based on a defected ground structure (DGS) and their design procedures are presented in this paper. A key merit of the filter configuration is that the selectivity of the LPFs can be conveniently controlled, whereas the bandwidth is fixed. The LPFs are realized using open-circuited uniform impedance stubs and stepped-impedance stubs (SISs). The position of the transmission zeros can be freely controlled by tuning the impedance ratio of the SISs. To expand the stopband, the dumbbell DGS is used to suppress the spurious passbands of the LPFs. Two demonstration filters with a cutoff frequency at 1 GHz have been designed, fabricated, and measured. The measured results indicate good performance: broad stopband ( $>15 f_{c}$ or $20~f_{c}$ ), low passband insertion loss (<0.3 dB), compact size, and sharp skirt characteristic.

English

A compact dumbbell shaped defected ground structure (DGS) is applied to reduce the mutual coupling between microstrip arrays elements for ISM band and wireless applications with 0.47 λ0 elements spacing. The dumbbell DGS with new distribution is inserted in the E-plane between the adjacent arrayscoupled elements to suppress the pronounced surface waves. A four-element array with dumbbell shaped DGS is designed, fabricated on a substrate with dielectric constant of 10.2 and thickness of 1.27mm, and measured. The results show that a reduction in mutual coupling of 35.6 dB is obtained between elements at the operation frequency of the array. The surface current distribution with and Without DGS for the array is discussed. The microstrip array with and without DGS are studied by the waveguide simulator method and fabricated by photolithographic technique.

Compact Elliptic function Lowpass Filter based on Defected Ground Structure

A compact microstrip lowpass filter (LPF) with prominent cutoff sharpness and wide stopband is presented. The microstrip LPF is composed of a broadened microstrip line on the top side of the microstrip structure, an H-shaped defected ground structure (DGS) and a modified dumbbell (DB) DGS in the ground plane. It has a simple design procedure and easily can be tuned. The designed filter is developed and experimental results show that it has a sharp cutoff frequency response.

An asymmetric defected ground structure with elliptical response and its application as a lowpass filter

A new asymmetric defected ground structure (DGS) consisting of two square headed slots connected with a rectangular slot transversely under a microstrip line is proposed. In the frequency characteristics of its unit cell, an attenuation zero is observed close to the attenuation pole. The DGS unit is represented by Cauer's T-network, modeled by a third order elliptical lowpass filter and finally equivalent L-C parameters are extracted. Several studies have been accomplished on the influence of the geometric modification of the filter on its characteristics. Better transition sharpness, lower passband insertion loss and broader stopband are observed, compared to popular dumbbell DGSs due to its additional attenuation zero. The two-cell configuration of this DGS produces a three-pole lowpass filter having wide and deep stopband at low cutoff frequency. This is applied under the input and output feed lines of a parallel-coupled bandpass filter for suppressing harmonic frequencies. A lowpass filter is realized using cascaded investigated DGS and dumbbell DGS under a microstrip line.

Design of ultra‐wide band (UWB) bandpass filter based on defected ground structure

AbstractA new structure of ultra‐wide band (UWB) band pass filter is proposed in this letter. The proposed UWB filter consists of a low pass filter and a quasi‐high pass filter. The low pass frequency characteristic is realized with a dumbbell defected ground structure (DGS) array and narrow slots, the corresponding cut‐off frequency is tuned to 10.7 GHz by adjusting sizes of each dumbbell and their spacing. The quasi‐high pass filter consists of two symmetrical inter‐digital capacitors. The cut‐off frequency is about 3.0 GHz. Combining these two structures we obtain a new structure of UWB band pass filter. An experimental UWB filter was fabricated, the measured results show that the insertion loss is less than 1.5 dB throughout the passband of 3.0–10.8 GHz, the variation of group delay less than 0.25 ns in this band, and a wide stopband bandwidth with 20 dB attenuation up‐to 20.0 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1374–1377, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22471

Miniaturized microstrip lowpass filter with wide stopband using double equilateral U-shaped defected ground structure

A compact double equilateral U-shaped defected ground structure (DGS) unit is proposed. In contrast to a single finite attenuation pole characteristic offered by the conventional dumbbell DGS, the proposed DGS unit provides dual finite attenuation poles that can be independently controlled by the DGS lengths. A 2.4-GHz microstrip lowpass filter using five cascaded double U-shaped DGS units is designed and compared with conventional DGS lowpass filters. This low pass filter achieves a wide stopband with overall 30-dB attenuation up-to10 GHz and more than 42% size diminution.

Study on Transmission Characteristic of Split-ring Resonator Defected Ground Structure

A square split-ring resonator (SRR) defected ground structure (DGS) is studied in this paper. This DGS structure has a ∞at low-pass characteristic and a sharp band-gap property compared to the conventional dumbbell DGS. A detailed analysis of the relationship between the transmission characteristic and the split-ring dimension is made. In order to enhance the out-band suppression, an improved SRR DGS cell with open stubs loaded on the conductor line is then presented and fabricated.

Compact quasi-elliptic function filter based on defected ground structure

A novel defected ground structure (DGS) is investigated for filter applications. With this structure, the basic resonant element exhibits the quasi-elliptic function responses. A new equivalent lumped L–C circuit model is presented and its corresponding L–C parameters are extracted by using parametric relationships, which has quasi-elliptic characteristics. The theoretical analysis for the effect of different design parameters has been carried out, which provides effective guidance in designing DGS. The performance of the new filter is also compared with the characteristic of the dumb-bell DGS filter to highlight the advantages of the proposed DGS. Based on the equivalent circuit model, a three-pole quasi-elliptic lowpass filter (LPF), using two DGS units cascaded, is optimally designed and implemented; experimental results show good agreement with theoretical ones.